# Targeting yes-associated protein to overcome imatinib resistance in gastrointestinal stromal tumor drug-tolerant persister cells

## TL;DR

This study shows that targeting YAP can help overcome imatinib resistance in gastrointestinal stromal tumor cells that survive treatment.

## Contribution

The study identifies YAP as a key player in drug-tolerant persister cells and proposes a combination therapy with YAP inhibitors.

## Key findings

- YAP activity is elevated in imatinib-resistant persister cells and is localized in the nucleus.
- Combining imatinib with YAP inhibitors like verteporfin significantly reduces persister cell survival.
- In mouse models, the combination therapy delays tumor regrowth after treatment stops.

## Abstract

The tyrosine kinase inhibitor (TKI) imatinib targets KIT and PDGFRA, offering significant therapeutic benefits in advanced gastrointestinal stromal tumors (GISTs). However, the high rate of recurrence following treatment discontinuation suggests that drug-tolerant persister cells (DTPs) may contribute to therapy resistance. Elucidating the mechanisms underlying DTP survival is critical for the development of curative strategies. This study aimed to investigate the role of yes-associated protein (YAP) in DTP survival and to evaluate the efficacy of combining imatinib with YAP inhibitors as a potential therapeutic approach.

Imatinib-sensitive GIST cell lines were treated with imatinib to generate DTPs. YAP activity was assessed via western blotting, fluorescence immunostaining, and nuclear-cytoplasmic fractionation. Proliferation and apoptosis assays were conducted to evaluate sensitivity to YAP inhibitors, such as verteporfin. Xenograft mouse models were used to assess the efficacy of combination therapy with imatinib and verteporfin.

DTPs exhibited increased nuclear localization and activity of YAP, which was reversible upon imatinib withdrawal. YAP inhibitors reduced nuclear YAP levels and showed greater efficacy in DTPs than in parental cells. Combination therapy with imatinib and verteporfin significantly suppressed DTP proliferation and induced apoptosis in vitro. In xenograft models, the combination therapy delayed tumor regrowth after treatment cessation compared to imatinib monotherapy.

YAP activity was elevated in GIST DTPs, and YAP inhibitors effectively suppressed this activity. The combination of imatinib and YAP inhibitors enhanced tumor growth suppression. These findings underscore the pivotal role of YAP in DTP survival and demonstrate the therapeutic potential of combining imatinib with YAP inhibitors.