Abstract
Regorafenib is used for hepatocellular carcinoma (HCC), but its response does not last long, partly due to chemoresistance acquisition. We performed a clustered regularly interspaced short palindromic repeats (CRISPR)-based loss-of-function genetic screen and aimed to discover molecules involved in regorafenib resistance in HCC. Xenograft tumors established from Cas9-expressing HCC cells with pooled CRISPR kinome libraries were treated with regorafenib or a vehicle. Sequencing analysis identified 31 genes, with the abundance of multiple guide RNAs increased in regorafenib-treated tumors compared to that in vehicle-treated tumors, including 2 paralogues, LATS2 and LATS1, core components of the Hippo signaling pathway. Notably, all eight designed guide RNAs targeting LATS2 increased in regorafenib-treated tumors, suggesting that LATS2 deletion confers regorafenib resistance in HCC cells. LATS2 knockdown significantly mitigated the cytotoxic and proapoptotic effects of regorafenib on HCC cells. LATS2 inhibition stabilized the Hippo signaling mediator YAP, leading to the upregulation of antiapoptotic Bcl-xL and the multidrug resistance transporter ABCB1. Among 12 hepatoma cell lines, the half maximal inhibitory concentration (IC50) values of regorafenib were positively correlated with any of YAP, Bcl-xL and ABCB1 levels. The inhibition of YAP or Bcl-xL in regorafenib-insensitive HCC cells restored their susceptibility to regorafenib. In conclusion, our screen identified the Hippo signaling pathway as the mediator of regorafenib efficacy in HCC.
Highlights
Hepatocellular carcinoma (HCC) is the primary histological type of liver cancer and the most common cause of cancer-related deaths, especially in Asia and Africa [1]
The RESORCE trial, a randomized, double-blind, placebo-controlled, phase 3 trial of regorafenib, was recently conducted for patients with HCC who progressed on sorafenib
To discover genes involved in chemoresistance to regorafenib in HCC, we performed an in vivo pooled clustered regularly interspaced short palindromic repeats (CRISPR) library screen
Summary
Hepatocellular carcinoma (HCC) is the primary histological type of liver cancer and the most common cause of cancer-related deaths, especially in Asia and Africa [1]. Surgical resection or transplantation are the curative therapeutic options, but they can be applied to only 10 to 20% of HCC patients because of donor shortage, liver dysfunction or detection at an advanced tumor stage [1]. Even after curative resection, HCC often recurs at a very high rate, since the liver is already predisposed to tumor development due to sustained chronic damage caused by viral infection, alcohol, lipids, etc. The RESORCE (regorafenib for patients with hepatocellular carcinoma who progressed on sorafenib treatment) trial, a randomized, double-blind, placebo-controlled, phase 3 trial of regorafenib, was recently conducted for patients with HCC who progressed on sorafenib. Since 2017, regorafenib can be used for advanced HCC as the second line of therapy after the failure of sorafenib treatment [2,3]
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