Gastric cancer is the third most lethal and fifth most common cancer worldwide. Diffuse gastric cancer (DGC) often develops due to inherited or somatic mutation of the tumour suppressor gene E-cadherin (CDH1). Germline inactivation of CDH1 causes the inherited cancer syndrome Hereditary DGC (HDGC), with up to 70% lifetime penetrance. Dasatinib, an ATP-competitive tyrosine kinase inhibitor, preferentially targets pathways that are upregulated in CDH1-null cancer cells. Consequently, it is considered a potential chemopreventative drug for advanced HDGC. To improve this targeted therapy, we aimed to identify synergistic partners of dasatinib, which provide a greater than additive effect when combined with dasatinib.
Single-cell level transcriptional changes in response to treatment can reveal drug targets that are involved in dasatinib resistance. To this end, we treated an inducible Cdh1/Trp53 knockout HDGC mouse model with dasatinib and a vehicle control. Mouse stomachs were then extracted for single-cell isolation (using the 10X Genomics Gene Expression Flex kit) and mRNA sequencing.
Bioinformatic analyses revealed a distinct cluster of putative gastric cancer cells. Differential expression analysis between these cells in treated versus control samples revealed genes differentially regulated in response to dasatinib. Gene set enrichment analysis identified Reactome pathways that were altered between treatment and control groups, including RHO GTPase, MAPK, and YAP/TAZ signalling, oxidative phosphorylation, and autophagy. Drugs targeting these signatures (defactinib, trametinib, verteporfin, metformin, and chloroquine, respectively) are predicted to be synergistic with dasatinib by countering emerging drug-resistant cell populations, and were therefore tested in combination with dasatinib in an HDGC cell line model.