Mutant K-RAS Promotes Invasion and Metastasis in Pancreatic Cancer through GTPase Signaling Pathways

Abstract

Pancreatic ductal adenocarcinoma is one of the most aggressive malignancies, characterized by the local invasion into surrounding tissues and early metastasis to distant organs. Oncogenic mutations of the K-RAS gene occur in more than 90% of human pancreatic cancers. The goal of this study was to investigate the functional significance and downstream effectors of mutant K-RAS oncogene in the pancreatic cancer invasion and metastasis. We applied the homologous recombination technique to stably disrupt K-RAS oncogene in the human pancreatic cell line MiaPaCa-2, which carries the mutant K-RASG12C oncogene in both alleles. Using in vitro assays, we found that clones with disrupted mutant K-RAS gene exhibited low RAS activity, reduced growth rates, increased sensitivity to the apoptosis inducing agents, and suppressed motility and invasiveness. In vivo assays showed that clones with decreased RAS activity had reduced tumor formation ability in mouse xenograft model and increased survival rates in the mouse orthotopic pancreatic cancer model. We further examined molecular pathways downstream of mutant K-RAS and identified RhoA GTP activating protein 5, caveolin-1, and RAS-like small GTPase A (RalA) as key effector molecules, which control mutant K-RAS-dependent migration and invasion in MiaPaCa-2 cells. Our study provides rational for targeting RhoA and RalA GTPase signaling pathways for inhibition of pancreatic cancer metastasis.

Kras promotes myeloid differentiation through Wnt/β‐catenin signaling

“…29 The importance of C/ EBPα in the expression of G-CSF receptor is supported by results showing that G-CSF receptor mRNA is selectively absent in C/EBPα knockout mice. Accumulated unphosphorylated β-catenin in the cytoplasm translocates to the nucleus (5,6), where it binds to Lef/Tcf and stimulates the transcription of target genes such as C/EBPα, C/EBPɛ, and G-CSF receptor (7). C/EBPα mRNA levels were reduced in HL-60 cells undergoing monocytic differentiation in response to treatment with 12-O-tetra-decanoylphorbol-13-acetate (TPA).…”

“…AKT phosphorylates GSK3β and inactivates GSK3β (3,4). Accumulated unphosphorylated β-catenin in the cytoplasm translocates to the nucleus (5,6), where it binds to Lef/Tcf and stimulates the transcription of target genes such as C/EBPα, C/EBPɛ, and G-CSF receptor (7). In the absence of DMSO, β-catenin is phosphorylated by a destruction complex composed of the core proteins, including Axin, APC, CK1, β-catenin, GSK3β, and E3-ubiquitin ligase β-TrCP.…”

“…3 Despite the high frequency of Nand Kras mutations in AML, the precise roles of ras oncogenes in leukemogenesis remain unclear. 1,6,7 Mutated Kras induces tumor cell migration through the activation of the MAPKs and PI3K/AKT pathways. 4 These findings indicate that Kras is essential for normal mouse development, whereas Hras and Nras are not.…”

“…5 Mutants of Kras play essential roles during malignant transformation in human cancers. 1,6,7 Mutated Kras induces tumor cell migration through the activation of the MAPKs and PI3K/AKT pathways. 2,8 Kras conditional knockout mice develop profound hematopoietic defects, including splenomegaly, an expanded neutrophil compartment, and reduced B-cell number, indicating that Kras is required for adult hematopoiesis.…”

Molecular mechanisms linking geranylgeranyl diphosphate synthase to cell survival and proliferation

“…Although Ras is mutated in a number of cancers like pancreatic and lung adenocarcinomas (McCormick, 2015, Padavano et al, 2015), the majority of prenylated proteins are not mutated in cancer (Alan and Lundquist, 2013). Notable exceptions are that dominant negative RhoA can be found in angioimmunoblastic T-cell lymphoma and mutated RhoH can be found in non-Hodgkin lymphoma and multiple myeloma (Preudhomme et al, 2000, Nagata et al, 2016).…”