Wild Type Kirsten Rat Sarcoma Is a Novel microRNA-622-regulated Therapeutic Target for Hepatocellular Carcinoma and Contributes to Sorafenib Resistance

Gut. 2018 Jul;67(7):1328-1341. doi: 10.1136/gutjnl-2017-315402. Epub 2017 Dec 23.

Abstract

Objective: Sorafenib is the only effective therapy for advanced hepatocellular carcinoma (HCC). Combinatory approaches targeting mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK)- and phosphatidylinositol-4,5-bisphosphate-3-kinase (PI3K)/protein-kinase B(AKT) signalling yield major therapeutic improvements. RAS proteins regulate both RAF/MAPK and PI3K/AKT signalling. However, the most important RAS isoform in carcinogenesis, Kirsten rat sarcoma (KRAS), remains unexplored in HCC.

Design: Human HCC tissues and cell lines were used for expression and functional analysis. Sorafenib-resistant HCC cells were newly generated. RNA interference and the novel small molecule deltarasin were used for KRAS inhibition both in vitro and in a murine syngeneic orthotopic HCC model.

Results: Expression of wild type KRAS messenger RNA and protein was increased in HCC and correlated with extracellular-signal regulated kinase (ERK) activation, proliferation rate, advanced tumour size and poor patient survival. Bioinformatic analysis and reporter assays revealed that KRAS is a direct target of microRNA-622. This microRNA was downregulated in HCC, and functional analysis demonstrated that KRAS-suppression is the major mediator of its inhibitory effect on HCC proliferation. KRAS inhibition markedly suppressed RAF/ERK and PI3K/AKT signalling and proliferation and enhanced apoptosis of HCC cells in vitro and in vivo. Combinatory KRAS inhibition and sorafenib treatment revealed synergistic antitumorigenic effects in HCC. Sorafenib-resistant HCC cells showed elevated KRAS expression, and KRAS inhibition resensitised sorafenib-resistant cells to suppression of proliferation and induction of apoptosis.

Conclusions: KRAS is dysregulated in HCC by loss of tumour-suppressive microRNA-622, contributing to tumour progression, sorafenib sensitivity and resistance. KRAS inhibition alone or in combination with sorafenib appears as novel promising therapeutic strategy for HCC.

Keywords: hepatocellular carcinoma; molecular mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / therapeutic use*
  • Carcinoma, Hepatocellular / drug therapy
  • Carcinoma, Hepatocellular / metabolism*
  • Carcinoma, Hepatocellular / pathology
  • Cell Culture Techniques
  • Humans
  • Liver Neoplasms / drug therapy
  • Liver Neoplasms / metabolism*
  • Liver Neoplasms / pathology
  • MicroRNAs / metabolism*
  • Niacinamide / analogs & derivatives*
  • Niacinamide / therapeutic use
  • Phenylurea Compounds / therapeutic use*
  • Proto-Oncogene Proteins p21(ras) / physiology*
  • Sorafenib

Substances

  • Antineoplastic Agents
  • KRAS protein, human
  • MIRN622 microRNA, human
  • MicroRNAs
  • Phenylurea Compounds
  • Niacinamide
  • Sorafenib
  • Proto-Oncogene Proteins p21(ras)