Littérature scientifique sur le sujet « K-ras cancer cells »

Pancreatic cancer remains intractable owing to the lack of effective therapy for unresectable cases. Activating mutations of K-ras are frequently found in pancreatic cancers, but these have not yet been targeted by cancer therapies. The Keap1-Nrf2 system plays a crucial role in mediating the oxidative stress response, which also contributes to cancer progression. Nrf2 activation reprograms the metabolic profile to promote the proliferation of cancer cells. A recent report suggested that K-ras- and Nrf2-active lung cancer cells are sensitive to glutamine depletion. This finding led to the recognition of glutaminase inhibitors as novel anticancer agents. In the current study, we used murine pancreatic cancer tissues driven by mutant K-ras and p53 to establish cell lines expressing constitutively activated Nrf2. Genetic or pharmacological Nrf2 activation in cells via Keap1 deletion or Nrf2 activation sensitized cells to glutaminase inhibition. This phenomenon was confirmed to be dependent on K-ras activation in human pancreatic cancer cell lines harboring mutant K-ras, i.e., Panc-1 and MiaPaCa-2 in response to DEM pretreatment. This phenomenon was not observed in BxPC3 cells harboring wildtype K-ras. These results indicate the possibility of employing Nrf2 activation and glutaminase inhibition as novel therapeutic interventions for K-ras mutant pancreatic cancers.

Objective. This study is to investigate the role of the CIKs cocultured with K-ras-DCs in killing of pancreatic cancer cell lines, PANC-1 (K-ras+) and SW1990 (K-ras−).Methods. CIKs induced by IFN-γ, IL-2, and anti-CD3 monoantibody, K-ras-DCCIKs obtained by cocultivation of k-ras-DCs and CIKs. Surface markers examined by FACS. IFN-γIL-12 ,CCL19 and CCL22 detected by ELISA. Proliferation of various CIKs tested via 3H-TdR. Killing activities of k-ras-DCCIKs and CTLs examined with 125IUdR.Results. CD3+CD56+and CD3+CD8+were highly expressed by K-ras-DCCIKs. In its supernatant, IFN-γ, IL-12, CCL19 and CCL22 were significantly higher than those in DCCIK and CIK. The killing rate of K-ras-DCCIK was greater than those of CIK and CTL. CTL induced by K-ras-DCs only inhibited the PANC-1 cells.Conclusions. The k-ras-DC can enhance CIK's proliferation and increase the killing effect on pancreatic cancer cell. The CTLs induced by K-ras-DC can only inhibit PANC-1 cells. In this study, K-ras-DCCIKs also show the specific inhibition to PANC-1 cells, their tumor suppression is almost same with the CTLs, their total tumor inhibitory efficiency is higher than that of the CTLs.

K-ras (Kirsten ras GTPase) mutations are oncogenic events frequently observed in many cancer types especially in pancreatic cancer. Although mitochondrial dysfunction has been associated with K-ras mutation, the molecular mechanisms by which K-ras impacts mitochondria and maintains metabolic homeostasis are not fully understood. In this study, we used two K-ras inducible cell systems, human pancreatic epithelial/ K-rasG12D (HPNE/K-rasG12D) and human embryonic kidney cells with tetracycline repressorT-Rex/K-rasG12V, to evaluate the role of oncogenic K-ras in regulating mitochondrial function. Among a panel of genes known to affect mitochondria, only the expression of OPA3 (optic atrophy protein 3) was consistently up-regulated by K-ras activation in both cell lines. Importantly, high expression of OPA3 was also observed in clinical pancreatic cancer tissues. Genetic knockdown of OPA3 caused a significant decrease of energy metabolism, manifested by a suppression of oxygen consumption rate (OCR) and a decrease in cellular ATP content, leading to inhibition of cell proliferation capacity and reduced expression of epithelial–mesenchymal transition (EMT) markers. Our study suggests that OPA3 may promote cellular energy metabolism and its up-regulation in K-ras-driven cancer is likely a mechanism to offset the negative impact of K-ras on mitochondria to maintain energy homeostasis. As such, OPA3 could be a potential target to kill cancer cells with K-ras mutations.

Abstract Introduction: K-Ras mutant cancers such as pancreatic cancer are a major cause of cancer-related death and are difficult to treat, with a five-year survival rate of less than 6%. It is reported that oncogenic K-Ras signaling passes through RAF/MEK/ERK pathways. Selumetinib (AZD6244) is a selective MEK inhibitor for K-Ras mutant cancers dependent on mitogen-activated protein kinase (MAPK) signaling pathway and is currently in phase II trials. However, the underlying mechanisms of action are not well known. Autophagy is a self-digest pathway to degrade cellular organelles and macromolecules in maintaining proteome homeostasis, and it is suppressed by the mammalian target of rapamycin complex 1 (mTORC1), a master regulator of translation and autophagy. mTOR activity is known to be activated by AMP-activated protein kinase (AMPK) and negatively regulated by c-Jun N-terminal kinase 1/2 (JNK1/2) MAPK signaling. Autophagy is thought to play protective and suppressive roles in cancer; however, the molecular basis for the relationship between the induction of autophagy and the initiation of pancreatic malignancy is currently unknown. Heat shock factor 1 (HSF1), a key transcription factor involved in proteotoxic stress response via protein-folding. HSF1 plays a pro-oncogenic role in the development of cancer by regulating signaling transduction and translation during tumorigenesis. HSF1 is reportedly hyperactive in pancreatic cancers. AZD6244 reportedly decreases HSF1 phosphorylation at Ser326 and HSF1 expression in melanomas and therefore abates cancer development. However, the detailed mechanism by which HSF1 engages in AZD6244-mediated autophagy in K-Ras mutant human pancreatic cancer is not fully understood. Objectives: This study aims to investigate the role of HSF1 in AZD6244-mediated autophagy in K-Ras mutant human pancreatic cancer. Methods and Results: AZD6244 induces robust autophagy response in human pancreatic cells with hyperactive K-Ras signaling. Simultaneously, AZD6244 reduces HSF1 phosphorylation at Ser326 and HSF1 expression in human pancreatic cancer cells. Intriguingly, genetic deletion of HSF1 induces autophagy under starvation condition. In addition, AZD6244 induces phosphorylation of AMPK Ser172 and JNK1/2 T183/Y185 and decreases mTORC1 activity in human pancreatic cancer cells. Pharmaceutical inhibition of AMPK or genetic deletion of JNK1/2 prevents AZD6244-induced autophagy. Furthermore, HSF1 knockdown induces phosphorylation of Unc-51-like kinase 1(ULK1) Ser555 and decreases ULK Ser757, which is mediated by AMPK and mTOR, respectively. Conclusion: HSF1 plays an integral role in Selumetinib-mediated autophagy through AMPK and/or JNK1/2 signaling in K-Ras mutant human pancreatic cancer cells. Citation Format: Shruti Ghai, Alex Young, Kuo-Hui Su. Novel effect of Selumetinib-mediated autophagy via HSF1 in K-Ras mutant pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3004.

Abstract The abilities of mutated active K-RAS and H-RAS proteins, in an isogenic human carcinoma cell system, to modulate the activity of signaling pathways following exposure to ionizing radiation is unknown. Loss of K-RAS D13 expression in HCT116 colorectal carcinoma cells blunted basal extracellular signal-regulated kinase 1/2 (ERK1/2), AKT, and c-Jun NH2-terminal kinase 1/2 activity. Deletion of the allele to express K-RAS D13 also enhanced expression of ERBB1, ERBB3, and heregulin but nearly abolished radiation-induced activation of all signaling pathways. Expression of H-RAS V12 in HCT116 cells lacking an activated RAS molecule (H-RAS V12 cells) restored basal ERK1/2 and AKT activity to that observed in parental cells but did not restore or alter basal c-jun NH2-terminal kinase 1/2 activity. In parental cells, radiation caused stronger ERK1/2 pathway activation compared with that of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which correlated with constitutive translocation of Raf-1 into the plasma membrane of parental cells. Inhibition of mitogen-activated protein kinase/ERK1/2, but not PI3K, radiosensitized parental cells. In H-RAS V12 cells, radiation caused stronger PI3K/AKT pathway activation compared with that of the ERK1/2 pathway, which correlated with H-RAS V12–dependent translocation of PI3K into the plasma membrane. Inhibition of PI3K, but not mitogen-activated protein kinase/ERK1/2, radiosensitized H-RAS V12 cells. Radiation-induced activation of the PI3K/AKT pathway in H-RAS V12 cells 2 to 24 hours after exposure was dependent on heregulin-stimulated ERBB3 association with membrane-localized PI3K. Neutralization of heregulin function abolished radiation-induced AKT activation and reverted the radiosensitivity of H-RAS V12 cells to those levels found in cells lacking expression of any active RAS protein. These findings show that H-RAS V12 and K-RAS D13 differentially regulate radiation-induced signaling pathway function. In HCT116 cells expressing H-RAS V12, PI3K-dependent radioresistance is mediated by both H-RAS-dependent translocation of PI3K into the plasma membrane and heregulin-induced activation of membrane-localized PI3K via ERBB3.

Colorectal carcinomas are characterized by multiple genetic alterations, including constitutive Wnt activity and gain-of-function mutations in K-RAS and B-RAF. BRAF encodes a Ser/Thr kinase acting in the Ras/MEK/ERK pathway and the V600E mutation found in 11% of colorectal cancers renders this kinase constitutively active. B-RAF mutated colorectal carcinomas represents a very aggressive entity with a poor prognosis. Understanding the molecular mechanisms activated downstream of mutated B-RAF is urgently needed to design new therapeutic avenues to treat B-ARF mutated colorectal carcinomas and to circumvent resistance to therapies targeting the Ras/Raf/MEK1/ERK1/2 pathway. In a search for candidates that critically contribute to both intrinsic and acquired resistance to MEK1 inhibition in B-RAF mutated colorectal cancer cells, we identified one scaffold protein whose expression is driven by both NF-kB and AP-1 families of transcription factors. This scaffold protein promotes the expression of HER2 and HER3 in colorectal cancer cells subjected to MEK1 or B-RAF inhibition (Selumetinib and Vemurafenib, respectively) and, as such, is critically involved in the intrinsic resistance to these targeted therapies. The same scaffold protein is also strongly induced in B-RAF but not K-RAS mutated colorectal cancer cells showing acquired resistance to MEK1 inhibition. Interfering with the expression of this scaffold protein circumvents both intrinsic and acquired resistance to Selumetinib in B-RAF mutated colorectal cancer cells. Our study defines a new molecular actor critically involved in oncogenic signaling pathways triggered by mutated B-RAF. Our study also defineS new combinatory therapies to better treat B-RAF-mutated colorectal carcinomas.

Cancer stem cells (CSCs) are a tumor cell subpopulation that drives tumor progression and metastasis, leading to a poor overall survival of patients. In colorectal cancer (CRC), the hyper-activation of Wnt/β-catenin signaling by a mutation of both adenomatous polyposis coli (APC) and K-Ras increases the size of the CSC population. We previously showed that CPD0857 inactivates Wnt/β-catenin signaling by promoting the ubiquitin-dependent proteasomal degradation of β-catenin and Ras proteins, thereby decreasing proliferation and increasing the apoptosis of CRC lines. CPD0857 also decreased the growth and invasiveness of CRC cells harboring mutant K-Ras resistant to EGFR mAb therapy. Here, we show that CPD0857 treatment decreases proliferation and increases the neuronal differentiation of neural progenitor cells (NPCs). CDP0857 effectively reduced the expression of CSC markers and suppressed self-renewal capacity. CPD0857 treatment also inhibited the proliferation and expression of CSC markers in D-K-Ras MT cells carrying K-Ras, APC and PI3K mutations, indicating the inhibition of PI3K/AKT signaling. Moreover, CPD0857-treated xenograft mice showed a regression of tumor growth and decreased numbers of CSCs in tumors. We conclude that CPD0857 could serve as the basis of a drug development strategy targeting CSCs activated through Wnt/β-catenin-Ras MAPK-PI3K/AKT signaling in CRCs.

KRAS, BRAF, and PI3KCA are the most frequently mutated oncogenes in human colon cancer. To explore their effects on morphogenesis, we used the colon cancer–derived cell line Caco-2. When seeded in extracellular matrix, individual cells proliferate and generate hollow, polarized cysts. The expression of oncogenic phosphatidylinositol 3-kinase (PI3KCA H1047R) in Caco-2 has no effect, but K-Ras V12 or B-Raf V600E disrupts polarity and tight junctions and promotes hyperproliferation, resulting in large, filled structures. Inhibition of mitogen-activated protein/extracellular signal–regulated kinase (ERK) kinase blocks the disruption of morphology, as well as the increased levels of c-myc protein induced by K-Ras V12 and B-Raf V600E. Apical polarity is already established after the first cell division (two-cell stage) in Caco-2 three-dimensional cultures. This is disrupted by expression of K-Ras V12 or B-Raf V600E but can be rescued by ribonucleic acid interference–mediated depletion of c-myc. We conclude that ERK-mediated up-regulation of c-myc by K-Ras or B-Raf oncogenes disrupts the establishment of apical/basolateral polarity in colon epithelial cells independently of its effect on proliferation.

400 Background: The role of the potential stem cell marker CD133 as a predictive or prognostic marker in multimodal rectal cancer treatment is currently under debate. While CD133 has been identified as a prognostic marker in rectal cancers after preoperative radiochemotherapy (RCT) it was recently characterized as a very unspecific feature for colorectal cancer stem cells. We therefore analyzed the association between CD133 expression and mutations in the proto-oncogenes K-Ras and PI3K in rectal cancer patients receiving neoadjuvant RCT. Methods: CD133 expression was evaluated immunhistochemically in pre-treatment biopsies and surgical specimens of 128 patients with locally advanced rectal cancers (cUICC II/III) treated with preoperative RCT within the phase-III German Rectal Cancer Trials. K-Ras mutations were analyzed by sequencing of exons 1, 2, and 3. PI3K mutations were detected by sequencing the p110α subunit (PIK3CA) and correlated with histopathologic parameters, tumor regression and survival. Results: CD133 expression was significantly associated with mutations in the K-Ras gene in both pre-treatment biopsies and post-treatment tumor specimens in uni- and multivariate analyses. However, no significant correlation was observed between CD133 and PI3K mutations. Post-treatment CD133 levels were correlated with neoadjuvant RCT (50.4 Gy/5-FU vs. 50.4 Gy/5-FU+Ox) and tumor regression grading. Anyway, there was no significant association between pre- and post-treatment CD133 expression and disease-free survival. Conclusions: CD133 expression levels are strongly associated with mutations in the K-Ras proto-oncogene in rectal cancers before and after preoperative RCT. Our results strengthen the hypothesis that CD133 is not a specific marker for colorectal stem cells but might be integrated in proliferation pathways like the ras-raf axis.

RASSF2 is a novel pro-apoptotic effector of K-Ras that is frequently inactivated in a variety of primary tumors by promoter methylation. Inactivation of RASSF2 enhances K-Ras-mediated transformation and overexpression of RASSF2 suppresses tumor cell growth. In this study, we confirm that RASSF2 and K-Ras form an endogenous complex, validating that RASSF2 is a bona fide K-Ras effector. We adopted an RNAi approach to determine the effects of inactivation of RASSF2 on the transformed phenotype of lung cancer cells containing an oncogenic K-Ras. Loss of RASSF2 expression resulted in a more aggressive phenotype that was characterized by enhanced cell proliferation and invasion, decreased cell adhesion, the ability to grow in an anchorage-independent manner and cell morphological changes. This enhanced transformed phenotype of the cells correlated with increased levels of activated AKT, indicating that RASSF2 can modulate Ras signaling pathways. Loss of RASSF2 expression also confers resistance to taxol and cisplatin, two frontline therapeutics for the treatment of lung cancer. Thus we have shown that inactivation of RASSF2, a process that occurs frequently in primary tumors, enhances the transforming potential of activated K-Ras and our data suggests that RASSF2 may be a novel candidate for epigenetic-based therapy in lung cancer.

Molte cellule tumorali, al fine di generare ATP e sostenere i processi anabolici, si servono principalmente della glicolisi piuttosto che della respirazione mitocondriale. Di conseguenza, il glucosio assume un ruolo critico per la sopravvivenza e la proliferazione delle cellule tumorali. Inoltre, attraverso la via dei pentosi fosfati, il glucosio porta alla formazione di NADPH, contribuendo al mantenimento nelle cellule dell’equilibrio ossidativo. Nondimeno, il glucosio può entrare anche nel pathway biosintetico delle esosammine (HBP), sostenendo la N- e O-glicosilazione di lipidi e proteine, importante per lo sviluppo tumorale. Considerando l’essenziale ruolo del glucosio, un possibile approccio per la terapia antitumorale è l’utilizzo del metabolismo del glucosio come target, non solo attraverso la glicolisi ma sfruttando anche gli altri processi glucosio-dipendenti. A tal proposito, la deprivazione di glucosio e la seguente analisi del destino cellulare a livello fenotipico e molecolare possono costituire una strategia utile per smascherare tutti i meccanismi mediati dal glucosio che partecipano alla crescita e alla sopravvivenza delle cellule tumorali. Tale strategia potrebbe essere poi sfruttata per offrire nuovi target e progettare nuove terapie antitumorali. Sebbene alcuni dati indichino che i tumori originino da cellule con persistenti difetti alla catena respiratoria mitocondriale, l’inibizione della fosforilazione ossidativa (OXPHOS) sembra una condizione di adattamento più che una causa della riprogrammazione metabolica delle cellule tumorali. In questo scenario, i meccanismi di regolazione post-traduzionali, di natura essenzialmente reversibile, a carico di proteine mitocondriali potrebbero assumere un importante ruolo regolatorio. Una delle principali modificazioni post-traduzionali è la fosforilazione dei residui Ser/Thr e, a tal proposito, la chinasi PKA presenta numerosi target a livello mitocondriale ed è coinvolta nella regolazione di biogenesi, trasporto e attività dei Complessi I e IV e della morfologia mitocondriale. Poiché è stato osservato che K-ras può causare la diminuzione dell’espressione di geni codificanti per componenti della via cAMP/PKA, nelle cellule K-ras-trasformate la deregolazione di tale via potrebbe portare alla disfunzione mitocondriale ed allo switch metabolico caratteristico delle cellule tumorali. A conferma di questa ipotesi, le cellule K-ras-trasformate mostrano minori livelli di attività dell’enzima PKA rispetto alle cellule normali. Inoltre, la stimolazione esogena della attività della PKA, ottenuta mediante trattamento con forskolina (FSK), protegge le cellule K-ras-trasformate, sia murine sia umane, dalla morte indotta dalla deplezione di glucosio. Tale protezione è dovuta alla stimolazione dell’attività del Complesso I, all’aumento dell’ATP intracellulare e della fusione mitocondriale e alla riduzione dei livelli di ROS. L’inibizione specifica di PKA previene quasi completamente molti di questi effetti. Inoltre, il breve trattamento con Mdivi-1, molecola in grado di favorire la fusione mitocondriale, riduce fortemente i livelli di ROS specialmente nelle cellule trasformate, indicando una stretta relazione tra morfologia e attività mitocondriale. Queste osservazioni supportano l’idea che l’apoptosi indotta dalla deprivazione di glucosio nelle cellule K-ras-trasformate è associata alla deregolazione della via cAMP/PKA che a sua volta causa la diminuzione dell’attività del Complesso I, la riduzione della produzione di ATP e la prevalenza della fissione mitocondriale rispetto alla fusione. Tale scoperta può aprire nuovi scenari per lo sviluppo di farmaci antitumorali. Poiché la carenza di glucosio si può riscontrare nell’ambiente in cui cresce e si sviluppa il tumore, tale condizione può essere sfruttata per potenziare l’azione di specifici agenti, come alcuni modulatori dell’OXPHOS. Infatti, l’inibizione delle funzioni mitocondriali in condizioni di deprivazione di glucosio potrebbe risultare letale per le cellule tumorali. In accordo, in questo lavoro viene mostrato che la deprivazione di glucosio e gli inibitori del Complesso I, come rotenone, piericidina A e capsaicina, hanno un effetto sinergico nell’indurre la morte delle cellule tumorali. Nello specifico, basse dosi d’inibitori del Complesso I, inefficaci sulle cellule normali e su cellule cresciute in alto glucosio, diventano citotossiche per le cellule tumorali cresciute in basso glucosio. L’effetto citotossico degli inibitori del Complesso I sulle cellule tumorali è ulteriormente e fortemente aumentato quando l’attività OXPHOS viene stimolata tramite il trattamento con FSK. Queste osservazioni dimostrano che la riattivazione della funzione mitocondriale associata alla deplezione di glucosio e al trattamento con basse dosi di inibitori del Complesso I riduce fortemente la sopravvivenza delle cellule tumorali e potrebbe quindi essere valutato come approccio terapeutico. Come indicato in precedenza, nelle cellule tumorali il glucosio è implicato in numerosi processi. L’analisi trascrittomica e proteomica di cellule murine K-ras-trasformate e della loro controparte normale mostra che la deprivazione di glucosio modula l’espressione di molti geni legati allo stress del reticolo endoplasmatico e all’Unfolded Protein Response (UPR). L’attivazione di tale risposta si osserva in entrambe le linee cellulari ma più fortemente nelle cellule trasformate, dove è associata anche alla morte cellulare. Infatti, la sua attenuazione tramite l’inibitore della traduzione proteica, cicloesimide, o lo chaperone chimico, 4-fenil-butirrato, protegge specificatamente le cellule trasformate dalla morte cellulare in basso glucosio. Anche l’inibizione della chinasi proapoptotica JNK, attivata a valle dell’UPR, previene specificatamente la morte delle cellule trasformate. Questa osservazione è in accordo col fatto che in basso glucosio le cellule trasformate mostrano una maggiore attivazione di JNK rispetto alle cellule normali. Inoltre, l’attivazione dell’UPR e la morte glucosio-dipendente delle cellule trasformate è completamente prevenuta dall’aggiunta nel terreno di coltura di un substrato dell’HBP, N-Acetyl-D-glucosammina, cosa che suggerisce una stretta relazione tra i due processi. È interessante notare che anche cellule umane esprimenti l’oncogene K-ras e caratterizzate da un fenotipo iperglicolitico mostrano simili effetti in seguito alla modulazione dell’UPR o dell’HBP. Quindi, la deprivazione di glucosio nelle cellule K-ras-trasformate può indurre un meccanismo di morte cellulare UPR-dipendente, attivato dall’eccessivo accumulo di proteine mal foldate, probabilmente come conseguenza della riduzione della N-glicosilazione delle proteine. La piena delucidazione di questa risposta potrebbe essere importante per progettare nuove strategie terapeutiche antitumorali. Oggi la nuova sfida della ricerca e della terapia antitumorale è il totale sradicamento del tumore, uccidendo anche le cellule staminali tumorali (cancer stem cells, CSCs). Considerando l’importante ruolo del metabolismo e della sua riprogrammazione nello sviluppo tumorale, la caratterizzazione del metabolismo delle CSCs può essere considerata un importante mezzo per lo sviluppo di nuove strategie antitumorali. Recentemente, è stata ottenuta la linea cellulare staminale di osteosarcoma umano, 3AB-OS. In questo lavoro di tesi ho svolto una prima caratterizzazione del suo profilo metabolico, paragonato a quello delle cellule tumorali MG63, da cui le cellule 3AB-OS sono state selezionate. Si è osservato che le cellule 3AB-OS dipendono più fortemente dalla glicolisi rispetto alle cellule MG63. Infatti, quando cresciute in presenza di galattosio e piruvato (substrati mitocondriali) le cellule 3AB-OS riducono maggiormente la propria capacità proliferativa rispetto alle cellule MG63. Esse risultano anche essere fortemente sensibili alla deprivazione di glucosio e al trattamento con inibitori della glicolisi mentre sono insensibili all’inibizione della catena respiratoria. Inoltre, diversamente dalle cellule MG63, le cellule 3AB-OS presentano principalmente mitocondri frammentati, in particolare in basso glucosio. Tutte queste osservazioni suggeriscono che il metabolismo energetico delle cellule 3AB-OS presenti caratteristiche paragonabili a quello delle cellule staminali normali e delle cellule tumorali caratterizzate da un metabolismo glicolitico. Può essere interessante notare che il profilo trascrizionale delle cellule 3AB-OS è simile a quello delle cellule K-ras-trasformate, confermando la similitudine tra le CSCs e le cellule tumorali glicolitiche. Quindi, alcune strategie sviluppate per il trattamento delle cellule tumorali glucosio-dipendenti potrebbero essere usate anche per trattare specifiche CSCs.
Several cancer cells, in order to generate ATP and sustain different anabolic processes, rely mainly on glycolysis instead of Oxidative Phosphorylation (OXPHOS). Thus, glucose assumes a critical role for cancer cell survival and proliferation. Moreover, through the penthose phospate pathway glucose leads to production of NADPH contributing to maintenance of cellular oxidative equilibrium. Besides, glucose can also enter Hexosamine Biosynthesis Pathway (HBP), sustaining lipid and protein N- and O-glycosylation that cover an important role in cancer development. Taking in consideration the essential role of glucose in cancer, one important anticancer therapeutic approach is to target its metabolism namely glycolysis and the other processes in which it is involved. On this regard, glucose deprivation and consequent analysis of cancer cell fate both at phenotypical and molecular level can be a useful strategy to unmask all mechanisms that participate to glucose-mediated cancer cell growth and survival. Such a strategy could be subsequently exploited to provide new targets and to set new anticancer therapies. Although there is evidence that tumors originate from cells with persistent defects in the mitochondrial respiratory system, inhibition of OXPHOS activity seems to be an adaptation to cancer metabolism reprogramming rather than a cause. In this scenario, reversible post-translational modifications of mitochondrial components could assume an important regulatory role. Among the most important post-translational modifications there is Ser/Thr phosphorylation and, on this regard, the protein kinase PKA has numerous mitochondrial targets being involved in the regulation of the biogenesis, the import and the activity of mitochondrial Complex I or IV as well as of mitochondrial morphology. Since it has been observed that oncogenic K-ras may lead to a depression of genes encoding for components of the cAMP/PKA signaling pathway, in K-ras-transformed cells the deregulation of cAMP/PKA pathway could cause OXPHOS depression and “glucose addiction” of cancer cells. In agreement with such a hypothesis, K-ras-transformed cells show lower PKA activity as compared to normal cells. Moreover, exogenous stimulation of PKA activity, achieved by Forskolin (FSK) treatment, protects mouse and human K-ras-transformed cells from apoptosis induced by glucose deprivation, by enhancing Complex I activity, intracellular ATP levels and mitochondrial fusion and by decreasing intracellular ROS levels. Worth noting, several of these effects are almost completely prevented by inhibition of PKA activity. Moreover, short time treatment with Mdivi-1, a molecule that favors mitochondrial fusion, strongly decreases the cellular ROS levels especially in transformed cells, indicating a close relationship between mitochondrial morphology and activity. These findings support the notion that glucose shortage-induced apoptosis, specific of K-ras-transformed cells, is associated to a derangement of PKA signaling that leads to mitochondrial Complex I decrease, reduction of ATP formation and prevalence of mitochondrial fission over fusion. Such a discovery can thereby open new approaches for the development of anticancer drugs. Given that glucose shortage is often encountered in the tumor microenvironment, it can be exploited to potentiate the action of specific agents, such as the mitochondrial OXPHOS activity modulators, that in condition of glucose deprivation could be lethal for cancer cells. Accordingly, it is shown that glucose deprivation and Complex I inhibitors, i.e., rotenone, piericidin A and capsaicin, synergize in inducing cancer cell death. In particular, low doses of Complex I inhibitors, ineffective on normal cells and on cells grown in high glucose, become specifically cytotoxic on cancer cells cultured in low glucose. Importantly, the cytotoxic effect of Complex I inhibitors is strongly enhanced when mitochondrial OXPHOS activity is stimulated by FSK. These findings demonstrate that the reactivation of the mitochondrial function associated with glucose depletion and low doses of mitochondrial Complex I inhibitors strongly affect cancer cell survival. This therapeutic approach might be valuable to eradicate cancer cells. As above indicated, glucose is implicated in numerous processes in cancer cells. Transcriptomic and proteomic analyses applied to mouse K-ras-transformed cells as compared to normal cells show that glucose deprivation modulates the expression of several genes linked to endoplasmic reticulum stress and the Unfolded Protein Response (UPR). The activation of such a response, as confirmed by mRNA and protein expression, is observed in both cell lines, but only in transformed cells is strictly associated to their death. In fact, its attenuation by protein translation inhibitor cycloheximide or chemical chaperone 4-Phenyl-butyrate specifically rescues transformed cells from death. Moreover, glucose deprivation-induced transformed cell death is also prevented by inhibition of an UPR downstream pro-apoptotic kinase, JNK, whose activation is observed specifically in transformed cells as compared to normal cells. Interestingly, UPR activation and death of transformed cells is completely prevented by addition of a specific HBP substrate, namely N-Acetyl-D-glucosamine, suggesting a strict relation between the two processes. Notably, also oncogenic K-ras expressing human glycolytic cells show similar effects after UPR modulating treatments. Thus, we show that glucose deprivation can induce an UPR-dependent transformed cell death mechanism, which is activated by harmful accumulation of unfolded proteins, probably as consequence of N-glycosylation protein reduction. The full elucidation of this response could be relevant to design new therapeutic strategies. Today the new challenge of anticancer research and therapy is the total eradication of the cancer, targeting cancer stem cells (CSCs). Considering the important role of metabolism and metabolic reprogramming in cancer development, also the definition of CSCs metabolism can be considered an important tool for future strategies targeting these cells. Recently, a human osteosarcoma 3AB-OS CSC-like line has been developed. Therefore we have decided to characterize its metabolic features as compared to the parental osteosarcoma MG63 cells, from which 3AB-OS cells were previously selected. 3AB-OS cells depend on glycolytic metabolism more strongly than MG63 cells. Indeed, addition to the growth medium of galactose and pyruvate -mitochondrial specific substrates- instead of glucose markedly reduces 3AB-OS growth, as compared to MG63 cells. In line with these findings 3AB-OS cells, compared to MG63 cells, are strongly sensitive to glucose depletion, glycolysis inhibition and less sensitive to respiratory inhibitors. Additionally, in contrast to MG63 cells, 3AB-OS display mainly fragmented mitochondria, particularly in low glucose. Overall, these findings suggest that 3AB-OS energy metabolism is more similar either to normal stem cells or to cancer cells characterized by a glycolytic metabolism. Interestingly, the transcriptional profile of CSCs is similar to that of K-ras-transformed cells, confirming a possible similarity to glycolytic cancer cells. Therefore, some strategies developed for glucose addicted cancer cells could be used also to treat specific CSCs.

Pancreatic Ductal Adenocarcinoma (PDAC) is nearly always associated with mutant K-Ras. Nevertheless, targeting oncogenic K-Ras has so far proved ineffective in treating this form of cancer and pancreatic cancer cell lines can become K-Ras independent. Other forms of Ras are rarely mutated but wild type N-Ras and H-Ras have been shown to be present alongside functional K-Ras mutations and have been demonstrated to increase responsiveness to growth factors. Beyond this little evidence had previously been gathered on the activity or function of N-Ras and H-Ras in PDAC. Therefore, this thesis aimed to determine if other Ras isoforms are active in PDAC cell lines and what effect they may have on controlling cell division, oxidative metabolism, cytokine expression and the phospholipid composition of the membrane. The presence of active N-Ras and K-Ras was identified in three of the four human PDAC cell lines tested. Only active K-Ras was detected in a cell line derived from a mouse model of pancreatic cancer driven by heterologous expression of mutant KRAS. N-Ras was shown to be functioning alongside K-Ras to control the relative level of oxidative metabolism in the Suit-2 and a faster growing variant of the Panc-1 cell lines, but K-Ras acts alone in the slow growing Panc-1 cell line that does not contain N-Ras. N-Ras and K-Ras were shown to have different effects on the levels of cytokines, although K-Ras is largely independent of N-Ras in its regulation of phospholipid composition. A novel N-Ras independent mechanism for K-Ras transcriptional control of cyclin B1 was demonstrated. When K-Ras is depleted cyclin B1 and cyclin A are decreased. Cyclin B1 transcription can be rescued by inhibition of the Proteasome. A model is proposed whereby an unknown protein or proteins activates cyclin B1 transcription in a cell-cycle independent fashion and is protected from proteasomal degradation by K-Ras. These results suggest that mutant K-Ras can act in conjunction with wild-type N-Ras, but also can function independently to regulate G2 cyclins.

碩士
國防醫學院
微生物及免疫學研究所
92
Colorectal cancer evolves through a multistep process in gene alterations. Mutated K-Ras was found in 45% of colorectal cancer in early development during adenomatous stage. Retinoid inducible gene 1 (RIG1) is a tumor suppressor gene isolated from retinoid-treated cells, which can negatively regulate downstream signal pathway of Ras and lead to growth suppression and apoptosis of several cancer cells. Here we analyzed the correlation between K-Ras mutation and RIG1 protein expression in paraffin-embedded colorectal cancer tissues, and investigated the regulation of RIG1 expression by the Ras signal pathways. Mutations at codon 12 and 13 of the K-Ras gene were found in 25 of 45 (55.5%) colorectal cancer tissues analyzed by DNA sequencing and muation-specific PCR. Twenty three out of the 25 (92%) tissues with K-Ras mutation were stained positive for RIG1 protein. Whereas, only 9 out of 20 (45%) tissues with wild type K-Ras expressed the RIG1 protein. RIG1 expression was positively correlated to tumor differentiation. Endogenous RIG1 expression was low in 8 colorectal cancer cell lines. Blockage of the ERK/ELK pathway by PD98059 (50μM) for 48 hours resulted in an enhanced RIG1 mRNA level in SW480 cells, and an increased RIG1 protein expression in SW480 and HT29 cells. Whereas, suppression of the PI3K/AKT pathway by LY294002 had no effect on RIG1 expression. High percentage of colorectal cancer tissues with K-Ras mutation were stained positive for RIG1 protein. However, results from in vitro data indicated down regulation of RIG1 expression through the ERK/ELK pathway in cells with K-Ras mutation. These observations suggest that RIG1 expressions were differently regulated between in vivo and in vitro by Ras signal pathways.

Prediction of clinical outcome in cancer is usually achieved by histopathological evaluation of tissue samples obtained during surgical resection of the primary tumor. Traditional tumor staging (AJCC/UICC-TNM classification) summarizes data on tumor burden (T), presence of cancer cells in draining and regional lymph nodes (N) and evidence for metastases (M). However, it is now recognized that clinical outcome cansignificantly vary among patients within the same stage. Data collected from largecohorts of human cancers has demonstrated the impact of immune-classification, which has a prognostic value that may add largely to the significance of the AJCC/UICC TNM-classification. In our study we examined the immune cells that infiltrated the tumor tissues of colorectal and ovarian cancer patients. In a cohort of newly diagnosed colorectal cancer patients we examined the correlations between the KRAS mutational status, patterns of tumor-infiltrating immune cells and the presence of tumor recurrence. Our data suggest that colorectal cancer patients with low levels of tumor-infiltrating lymphocytes, a high CD1a/DC-LAMP tumor-infiltrating dendritic cells ratio, and a KRAS mutation in codon 13 are at a high risk of disease recurrence. In ovarian cancer patients we focused on the dynamics of the tumor-infiltrating...

碩士
高雄醫學大學
醫學研究所碩士班
94
The biomarkers of lung cancer that can significantly affect the prognosis of the patients and the effectiveness of anti-cancer drug therapy are (1) K-ras mutation (2) EGFR mutation (3) biomarkers of neuroendocrine features. From literature review, we know that the prevalence of lung cancer is increasing, the prevalence of smoking is increasing too, and K-ras mutation is significantly correlated with the smoking status. So the role of K-ras mutation is lung cancer carcinogenesis is becoming more and more significant. Our study focused on the feasibility of predicting K-ras mutational status by analyzing the gene expression profile of peripheral blood by membrane array, and the roles of K-ras mutation in lung cancer carcinogenesis. We sieve out 28 genes that most related to the mutated K-ras associated carcinogenetic pathway by means of comparative genome hybridization and bioinformatics. Then we constructed the membrane array including these 28 genes. We collected 30 coupled lung cancer tumor tissue and peripheral blood samples. By direct sequencing of the tumor tissue, the K-ras mutation rate is 36.7% (11/30), the hot spots of K-ras mutation are codon 12 (81.9%) and codon 13 (18.1%). There are 11 patients have positive results on membrane array on peripheral blood analysis, compared with the results of tumor tissue direct sequencing, the sensitivity, specificity and accuracy of the membrane array are 81.8%, 89.5%, 86.7% respectively. The kappa statistic is 0.713, revealed a good correlation between membrane array and direct sequencing. The K-ras mutation rate of the male and the female are 21.4% and 50% respectively. The K-ras mutation rate in early stage(stage I+II) and late stage lung cancer(stage III+IV) are 21.4% and 50% respectively. The membrane array positive rate of the male and female are 21.4% and 50% respectively, the membrane array positive rate in early stage and late stage lung cancer are 28.6% and 43.8% respectively. The K-ras mutation rate and membrane array positive rate is higher in women and in late stage lung cancer, but not statistically significant. TBX19 is over-expressed more commonly in late stage lung cancer (43.8%) than in early stage lung cancer (7.1%), and is statistically significant (p<0.05). Besides, we find out 4 genes that their over-expression is significantly correlated with K-ras mutation. These four genes include BCL2 (p<0.001), E2F4 (p<0.001), MMP1 (p<0.05), TBX19 (p<0.001). The next step of our study is to clarify the relationship between the four genes and the mutated K-ras in lung cancer carcinogenesis.