Ifenprodil identified as an adjunct to sorafenib for HCC treatment via CRISPR-Cas9 screen

The vasodilator ifenprodil together with sorafenib has been identified as a new drug combination for hepatocellular carcinoma (HCC) treatment by researchers from the University of Hong Kong (HKU) using clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR-Cas9) screen.

By utilizing the combinatorial CRISPR-Cas 9 screen, two gene targets, including N-methyl-D-aspartate receptor 1 (NMDAR1) and FLT4/FGFR3, were identified to suppress HCC cell proliferation and stemness. Another key finding of the study was that HCC patients with low NMDAR1 expression had better survival outcomes. Both findings led the researchers to evaluate the efficacy of targeting NMDAR1 and FLT4/FGFR3 in HCC treatment. [Cancer Res 2021;81:6219-6232]

Ifenprodil and sorafenib were used to target NMDAR and FLT4 and/or FGFR3, respectively. Results showed that ifenprodil synergized with sorafenib to reduce cell growth and stemness in multiple HCC cell lines, patient-derived organoids and tumour xenograft models.

Thus, the two-drug regimen of ifenprodil and sorafenib profoundly suppressed the growth and self-renewal ability of HCC cells, the researchers noted.

“Additionally, we also showed that upregulation of unfolded protein response, triggering of cell-cycle arrest, and downregulation of genes associated with wingless-related integration site [WNT]–signalling and stemness could account for the enhanced effects of the drug combination,” they explained.

Liver cancer is the fifth most common cancer and the third leading cause of cancer death in Hong Kong. Despite initial response to sorafenib, HCC tumours often develop drug resistance, which limits treatment options. Combination therapy is a strategy for expanding treatment options to reduce drug resistance that arises from monotherapy.

The combinatorial CRISPR-Cas9 screen enabled expedited search among many possible drug combinations for those that inhibit druggable targets in the HCC genome. In the study, genes that are existing or potential drug targets for suppressing HCC growth were covered. “Utilizing the combinatorial CRISPR-Cas9 screen to generate multiplexable gene knockouts, we rapidly characterized the survival of cancer cells following dual-genetic knockouts in a pool of cells linked with DNA barcodes specifying the type of genetic alterations they carry,” noted the researchers.

In contrast to conventional drug screening array that requires handling of many independent multiwells, the CRISPR-Cas9 screen requires only a simple set-up since the number of DNA barcodes carried by a large population of cells could be counted in high volume by throughput sequencing technologies.

“Through screening genes and their combinations from which hits can be translated directly into combinations of existing drugs, nonconventional drugs and drug combinations could be discovered and repurposed for treating cancers,” pointed out the researchers.

“Successful drug repurposing saves cost and time that would otherwise be needed for developing new therapeutic agents with uncertain efficacy and safety profile,” Said Dr Stephanie Ma of the School of Biomedical Sciences, HKU.

“The application of the combinatorial CRISPR-Cas9 screen has broadened our scope in search for effective combinations of actionable targets and repurposed drugs for HCC in a rapid and simple manner, and could be extended to other cancers and diseases,” added Dr Alan Wong of the School of Biomedical Sciences, HKU.