Pan-KRAS inhibitors suppress proliferation through feedback regulation in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is currently one of the most lethal cancers worldwide. Several basic studies have confirmed that Kirsten rat sarcoma virus (KRAS) is a key driver gene for the occurrence of PDAC, and KRAS mutations have also been found in most patients in clinical studies. In this study, two pan-KRAS inhibitors, BI-2852 and BAY-293, were chosen as chemical probes to investigate their antitumor potency in PDAC. Their inhibitory effects on KRAS activation were validated in vitro and their antiproliferative potency in PDAC cell lines were profiled, with half-maximal inhibitory concentration (IC50) values of approximately 1 µM, demonstrating the therapeutic potential of pan-KRAS inhibitors in the treatment of PDAC. However, feedback regulation in the KRAS pathway weakened inhibitor activity, which was observed by a 50 times difference in BAY-293 from in vitro activity. Furthermore, pan-KRAS inhibitors effectively inhibited cell proliferation in 3D organoids cultured from PDAC patient samples; however, there were some variations between individuals. These results provide a sufficient theoretical foundation for KRAS as a clinical therapeutic target and for the application of pan-KRAS inhibitors in the treatment of PDAC, with important scientific significance in translational medicine.

Wild­type KRAS inhibits the migration and invasion of pancreatic cancer through the Wnt/ß­catenin pathway.

Kirsten rat sarcoma virus (KRAS) mutation is considered to be the event that leads to the initiation of pancreatic ductal adenocarcinoma (PDAC), the mutation frequency of the KRAS gene in PDAC is 90­95%. Studies have shown that wild­type KRAS (KRASWT) has a survival advantage in PDAC and can antagonize the effect of mutated KRAS G12D (KRASG12D), leading to a low cell transformation efficiency. The present study focused on the differences in biological behavior between KRASWT and KRASG12D and explored the mechanism in pancreatic cancer. Overexpressed KRASWT and KRASG12D was transfected into cells through lentiviral transfection. The differences and mechanisms were explored using cell counting kit­8 (CCK­8), clone formation, wound healing and Transwell assays, as well as western blotting, immunohistochemistry and tumor formation in nude mice. In vitro, the proliferation of KRASWT group was reduced compared with PANC­1 group, while the proliferation of KRASG12D group was not significantly changed. In vivo, the proliferation of KRASWT group was reduced and that of KRASG12D group was enhanced compared with that in the PANC­1 group. The invasion and migration of KRASWT group were decreased, while the invasion and migration of KRASG12D group were increased. Western blotting showed that the expression of E­cadherin, α­E­catenin, MMP­3, MMP­9, STAT3 and phosphorylated STAT3 in KRASWT group was increased, while no significant difference was observed in KRASG12D group. The results of immunohistochemistry were consistent with those of western blotting. KRASWT group can inhibit the proliferation of pancreatic cancer in vitro and in vivo, while KRASG12D group can significantly promote proliferation in vivo, but not significantly in vitro. Wild­type KRAS may inhibit the invasion and migration of pancreatic cancer through the Wnt/ß­catenin pathway.

Extrinsic KRAS Signaling Shapes the Pancreatic Microenvironment Through Fibroblast Reprogramming.

BACKGROUND & AIMS: Oncogenic Kirsten Rat Sarcoma virus (KRAS) is the hallmark mutation of human pancreatic cancer and a driver of tumorigenesis in genetically engineered mouse models of the disease. Although the tumor cell-intrinsic effects of oncogenic Kras expression have been widely studied, its role in regulating the extensive pancreatic tumor microenvironment is less understood. METHODS: Using a genetically engineered mouse model of inducible and reversible oncogenic Kras expression and a combination of approaches that include mass cytometry and single-cell RNA sequencing we studied the effect of oncogenic KRAS in the tumor microenvironment. RESULTS: We have discovered that non-cell autonomous (ie, extrinsic) oncogenic KRAS signaling reprograms pancreatic fibroblasts, activating an inflammatory gene expression program. As a result, fibroblasts become a hub of extracellular signaling, and the main source of cytokines mediating the polarization of protumorigenic macrophages while also preventing tissue repair. CONCLUSIONS: Our study provides fundamental knowledge on the mechanisms underlying the formation of the fibroinflammatory stroma in pancreatic cancer and highlights stromal pathways with the potential to be exploited therapeutically.

KRAS mutations as essential promoters of lymphangiogenesis via extracellular vesicles in pancreatic cancer.

Kirsten rat sarcoma virus (KRAS) gene mutations are present in more than 90% of pancreatic ductal adenocarcinomas (PDACs). KRASG12D is the most frequent alteration, promoting preneoplastic lesions and associating with a more aggressive phenotype. These tumors possess increased intratumoral lymphatic networks and frequent lymph node (LN) metastases. In this issue of the JCI, Luo, Li, et al. explored the relationship between the presence of the KRASG12D mutation and lymphangiogenesis in PDAC. The authors used in vitro and in vivo models and an elegant mechanistic approach to describe an alternative pathway for lymphangiogenesis promotion. KRASG12D induced SUMOylation of heterogenous nuclear ribonucleoprotein A1 (hnRNPA1) via SAE1 and SUMO2 activation. SUMOylated hnRNPA1 was loaded into extracellular vesicles (EVs) and internalized by human endothelial lymphatic cells (HLEC). Further, SUMOylated hnRNPA1 promoted lymphangiogenesis and LN metastasis by stabilizing prospero homeodomain protein 1 (PROX1) mRNA. These data provide mechanistic insight into cancer lymphangiogenesis with the potential for developing biomarkers and RAS pathway therapeutics.

Colorectal cancer-derived exosomes and modulation KRAS signaling.

Colorectal cancer (CRC) is one of the most common cancers worldwide and one of the main causes of cancer-associated mortality. At the period of diagnosis, metastases to other tissues will be present in around 30% of CRC individuals. Individuals with CRC continue to have a poor prognosis despite advances in medication. There is a growing body of literature that CRC develops as a result of the aggregation of various mutations in tumor oncogenes or suppressor genes and that diagnosing cancer in its initial phases may assist in increasing the overall lifespan of individuals with the illness. On the other hand, tumor cells may discharge exosomes in response to oncogenic mutations. By Inhibiting signaling pathways, including the Kirsten rat sarcoma virus (KRAS) mechanism, which is important in a variety of cell activities, exosomes have been shown to cause colorectal cancer in animal studies. The purpose of this review was to summarize the latest discoveries on the modulation of KRAS signaling by exosomes extracted from colorectal cancer.

Complete response to nivolumab in Kirsten rat sarcoma virus oncogene KRAS-G12C mutant metastatic lung adenocarcinoma: a case report.

BACKGROUND: The advent of immunotherapies has ushered in a new era in the treatment of non-small cell lung carcinoma. Although immunotherapies are associated with improved clinical outcomes, studies report a median overall survival of 11 months with progression-free survival of 2.5 months with the use of nivolumab for pretreated metastatic non-small cell lung cancer. Herein, we describe a case of advanced non-small cell lung carcinoma that has shown exceptional response to immunotherapy, with the patient being in complete response for the past 6 years since commencement of nivolumab. CASE PRESENTATION: We report the case of a 58-year-old female Caucasian, an ex-smoker with 40-pack-year history of smoking, who presented with cough and chest pain and was subsequently diagnosed with metastatic pulmonary adenocarcinoma. The tumor was positive for Kirsten rat sarcoma virus oncogene KRAS-G12C mutation and had high programmed death-1 ligand expression. She was commenced on first-line chemotherapy with carboplatin and gemcitabine with disease response, then continued on maintenance pemetrexed. She was then commenced on immunotherapy with nivolumab, with complete response for a total of 6 years. She does not report any adverse events. Currently, she shows no evidence of recurrence of non-small cell lung carcinoma. CONCLUSION: The exceptional response to immunotherapy seen in this case may be explained by the presence of Kirsten rat sarcoma virus oncogene mutation, which is associated with enhanced clinical response to programmed death-1 ligand inhibitors. This report emphasizes the urgent need for further studies evaluating the role of Kirsten rat sarcoma virus oncogene mutation in determining the clinical efficacy of immunotherapies. This would enable us to make effective evidence-based clinical interventions in the treatment of non-small cell lung carcinoma.

Neoplastic transformation of human epidermal keratinocytes by AD12-SV40 and Kirsten sarcoma viruses.

Recent investigations have begun to dissect the number and nature of genetic alterations associated with cancer cells. In the present study, primary human epidermal keratinocytes acquired indefinite life-span in culture but did not undergo malignant conversion in response to infection with a hybrid of adenovirus 12 and simian virus 40. Addition of Kirsten murine sarcoma virus, which contains a K-ras oncogene, to these cells induced morphological alterations associated with the acquisition of neoplastic properties. These findings demonstrate the malignant transformation of human primary epithelial cells in culture and support a multiple-step process for neoplastic conversion.

Colorectal cancer-derived exosomes and modulation KRAS signaling

Colorectal cancer (CRC) is one of the most common cancers worldwide and one of the main causes of cancer-associated mortality. At the period of diagnosis, metastases to other tissues will be present in around 30% of CRC individuals. Individuals with CRC continue to have a poor prognosis despite advances in medication. There is a growing body of literature that CRC develops as a result of the aggregation of various mutations in tumor oncogenes or suppressor genes and that diagnosing cancer in its initial phases may assist in increasing the overall lifespan of individuals with the illness. On the other hand, tumor cells may discharge exosomes in response to oncogenic mutations. By Inhibiting signaling pathways, including the Kirsten rat sarcoma virus (KRAS) mechanism, which is important in a variety of cell activities, exosomes have been shown to cause colorectal cancer in animal studies. The purpose of this review was to summarize the latest discoveries on the modulation of KRAS signaling by exosomes extracted from colorectal cancer. (AU)

Molecular cloning of the temperature-sensitive 371 Kirsten murine sarcoma virus and expression in Escherichia coli of the mutant and wild-type viral Kirsten ras p21 proteins.

Rodent fibroblasts infected with the ts371 Kirsten murine sarcoma virus (KiMuSV) are temperature sensitive for the maintenance of transformation because of the production of an abnormal p21 protein. We cloned the ts371 KiMuSV provirus from the genome of a conditionally transformed nonproducer cell line, ts371 KiMuSV NRK clone 5 (T. Y. Shih, M. O. Weeks, H. A. Young, and E. M. Scolnick, J. Virol. 31:546-556, 1979). The molecularly cloned virus had 1,000-fold lower transformed focus-forming activity at 39 degrees C than at 34 degrees C. The ts371-v-Ki-ras gene differed from the wild type (wt) by a single point mutation, resulting in the substitution of arginine for glutamine at amino acid residue 43 of the encoded p21. A second difference from the published sequence for wt v-Ki-ras (N. Tsuchida, T. Ryder, and E. Ohtsubo, Science 217:937-939, 1982) at amino acid residue 37 was found. However, on sequencing the wt v-Ki-ras in this region, we found that it also contained a glutamate at residue 37. Preliminary characterization of bacterially expressed wt and ts371-v-Ki-ras p21 proteins is discussed.

Expression of intact Ki-ras p21 protein in Escherichia coli.

We have constructed recombinant plasmids capable of expressing in Escherichia coli the intact ras p21 protein encoded by Kirsten murine sarcoma virus. The Ki-ras gene was inserted into an expression vector carrying the E. coli tryptophan promoter and E. coli lipoprotein transcriptional terminator. The resulting plasmids direct the synthesis of large quantities of p21 protein, which represented 20% of the total cellular protein. The Ki-ras p21 protein is immunoprecipitated with monoclonal antibody to p21, and exhibits guanine nucleotide binding activity and autophosphorylation activity. The purified Ki-ras p21 expressed in E. coli has shown to have intact N-terminal and C-terminal amino acid sequences predicted by the nucleotide sequences and migrate as -23K in SDS/polyacrylamide gels.

Synthesis of proviral DNA in inbred mouse-derived clones of cells expressing different Fv-1 phenotypes.

Formation of proviral DNAs by B-tropic murine leukaemia viruses (MLVs) was examined in N-type and dually permissive mutant cells derived from two inbred mouse strains, DDD and G, both of which are N-type. In the N-type cells, formation of circular proviral DNA was strongly suppressed relative to that of linear DNA. Mutation resulting in loss of the N-type Fv-1 restriction resulted in efficient formation of circular DNA by the previously restricted B-tropic MLV. This showed that Fv-1 restriction and inhibition of closed circular DNA formation were controlled by the same gene. The efficiency of formation of circular proviral DNA by the defective Kirsten murine sarcoma virus was determined by the tropism of the helper virus.

Toward a model for the molecular genetics of carcinogenesis in rats.

Cultured rat embryo cells are resistant to neoplastic transformation by chemical carcinogens unless they are extensively subcultured or infected with a murine leukemia virus (MuLV) first. We found that, in normal cultured cells, MuLV activates expression of rat genes that are the progenitors of sarcoma virus genes, but not those of endogenous "leukemia" virus. Elevated levels of sarcoma virus-related RNA in normal cells infected with MuLV were indistinguishable from the levels in cells transformed spontaneously or by a carcinogen or a sarcoma virus. Because of previous reports that some carcinomas in rats also contain elevated levels of sarcoma virus-related RNA, we believe these events can be explained by a molecular genetic model which may be generally valid for initiation of carcinogenesis. The basic elements of the model are: transcriptional activation of all the multiple copies of normal rat progenitors of sarcoma virus genes is required before cellular transformation can be initiated, and initiation occurs when a spontaneous or induced mutation in any one active copy of these same genes generates a dominant transforming function.

Expression of pp60v-src alters the ionic permeability of the plasma membrane in rat cells.

The transmembrane potential of Rous sarcoma virus (RSV)-infected Rat-1 cells, expressing the pp60v-src protein kinase, is markedly less negative (by approximately 30 mV) than that of their normal counterparts. By contrast, the membrane potential of Rat-1 cells infected with Kirsten sarcoma virus is virtually unaltered. The RSV-induced membrane depolarization is shown to be due to a severalfold increase in the cation permeability ratio (PNa/PK) of the plasma membrane. When cells infected with a temperature-sensitive mutant of RSV (ts LA29), encoding a src protein with heat-labile kinase activity, are shifted from the nonpermissive to the permissive temperature, a rapid and sustained membrane depolarization is observed. Conversely, thermal inactivation of the ts LA29 pp60v-src kinase activity rapidly restores the membrane potential to near normal levels. Addition of epidermal growth factor, platelet-derived growth factor, or insulin to uninfected cells fails to cause a detectable change in membrane potential. We conclude that, unlike growth factor receptor tyrosine kinases, pp60v-src can induce, either directly or indirectly, a major change in the membrane permeability to monovalent cations.