Sorafenib-resistance is mediated by a novel Kirsten rat sarcoma-microRNA-axis in hepatocellular carcinoma

Introduction:

Acquired drug-resistance is a crucial therapeutic issue for intermediate and advanced hepatocellular carcinoma (HCC) patients treated with sorafenib. The RAF/MAPK-pathway is one of the major targets of the multi-kinase inhibitor sorafenib. RAS proteins function as upstream-regulators of RAF/MAPK-signaling. However, the most prominent RAS isoform in carcinogenesis, Kirsten rat sarcoma (KRAS), is still unexplored in HCC progression and therapy resistance.

Methods:

Sorafenib-resistant HCC cells were generated and used for expression and functional analysis. HCC tissue samples, microarrays, and human and murine HCC cell lines were used. The Cancer Genome Atlas (TCGA) datasets of HCC patient samples were analyzed using online databases. Si-RNAs, microRNAs and a novel small molecule – “deltarasin” – were used for inhibition of KRAS. A murine syngeneic orthotopic HCC model was applied for in vivo analysis of KRAS inhibition.

Results:

KRAS expression was modulated by sorafenib in HCC cell lines. Sorafenib-resistant cells showed elevated KRAS expression as compared to non-resistant HCC cells. KRAS inhibition was sufficient to break sorafenib-resistance. Moreover, KRAS expression was elevated in HCC and correlated with ERK activation, proliferation, size, tumor stages and survival of patients. MicroRNA library screening revealed KRAS as a major functional target of the tumorsuppressive microRNA-622. In vivo, deltarasin treatment markedly suppressed tumor proliferation, enhanced apoptosis and reduced RAF/ERK- and PI3K/AKT signaling.

Conclusions:

KRAS is dysregulated in HCC which is mediated by loss of the tumorsuppressive microRNA-622. The miR-622-KRAS axis contributes to tumor progression and sorafenib-resistance. KRAS inhibition alone or in combination with sorafenib appears as novel promising therapeutic strategy for HCC.