Transcriptional Regulation of miR-31 by Oncogenic KRAS Mediates Metastatic Phenotypes by Repressing RASA1

Abstract

Activating KRAS mutations are nearly ubiquitous in pancreatic cancer occurring in more than 95% of clinical cases. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by binding sequences within the 3′UTRs of target mRNAs. An integral role for miRNAs in cancer pathogenesis is well established; however, the role of miRNAs in KRAS-mediated tumorigenesis is poorly characterized. Here it is demonstrated that expression of miR-31 is coupled to expression of oncogenic KRAS and activity of the MAPK pathway. MiR-31 is highly expressed in patient derived xenografts and a panel of pancreatic and colorectal cancer cells harboring activating KRAS mutations. The miR-31 host gene is a large non-coding RNA that correlates with miR-31 expression and enabled identification of the putative miR-31 promoter. Using luciferase reporters, a minimal RAS responsive miR-31 promoter was found to drive robust luciferase activity dependent on expression of mutant KRAS and the transcription factor ELK1. Furthermore, ELK1 interacts directly with the endogenous miR-31 promoter in a MAPK-dependent manner. Expression of enforced miR-31 significantly enhanced invasion and migration of multiple pancreatic cancer cells resulting from activation of RhoA through regulation of the miR-31 target gene RASA1. Importantly, acute knockdown of RASA1 phenocopied enforced miR-31 expression on the migratory behavior of pancreatic cancer cells through increased RhoA activation.

Fusobacterium nucleatum Increases Proliferation of Colorectal Cancer Cells and Tumor Development in Mice by Activating Toll-Like Receptor 4 Signaling to Nuclear Factor−κB, and Up-regulating Expression of MicroRNA-21

“…The well-known oncoprotein RAS can be inactivated through binding to the RAS-GAP members 26 . Several studies have shown that RASA1 mutation or loss of function in CRC results in the activation of RAS-MAPK cascade 27–29 . Therefore, we assumed that F nucleatum infection may lead to the reduced expression of RASA1 expression through miR21, and result in the activation of MAPK signaling pathway.…”

Clustered miRNAs and their role in biological functions and diseases

“…Many miRNAs also target TFs to modulate their own expression or that of other miRNAs (Mihailovich et al, 2015). In KRAS proto-oncogene, GTPase (KRAS) mutant cells, Ras-responsive element binding protein (RREB1) binds to the promoter of miR-143/145 cluster resulting in its suppression (Kent, Mendell & Rottapel, 2016). Interestingly, KRAS and RREB1 in turn are the targets of miR-143/145 cluster (Das & Pillai, 2015).…”

Function and regulation of microRNA‐31 in development and disease

“…One well‐documented oncomiR role of miR‐31 was described in colorectal cancers (Cottonham et al, ; Cekaite et al, ; Xu et al, ; Yang et al, ; Ito et al, ; Lei et al, ; Li et al, ; Tateishi et al, ). Some of the miR‐31 targets of colon cancer include important tumor suppressors such as E2F2 (E2F Transcription Factor 2); SATB2 , RASA1 (RAS p21 GTPase activating protein 1), which was recently shown to be targeted by miR‐31 in pancreatic cancer); RHOBTB1 (Rho‐Related BTB Domain Containing 1); and TIAM1 (T Lymphoma and Metastasis Gene 1) (Cottonham et al, ; Sun et al, ; Xu et al, ; Yang et al, ; Li et al, ; Kent et al, ). Importantly, suppression of miR‐31 in colon cancer cells resulted in the increased sensitivity to chemotherapeutic drug fluorouracil, suggesting the potential of using miR‐31 as a therapeutic target to enhance the efficacy of chemotherapy treatments (Wang et al, ).…”