A Therapeutic Strategy for Chemotherapy-Resistant Gastric Cancer via Destabilization of Both β-Catenin and RAS

Treatment of advanced gastric cancer patients with current standard chemotherapeutic agents frequently results in resistance, leading to poor overall survival. However, there has been no success in developing strategies to overcome it. We showed the expression levels of both β-catenin and RAS were significantly increased and correlated in tissues of 756 gastric cancer (GC) patients and tissues of primary- and acquired-resistance patient-derived xenograft tumors treated with 5-fluorouracil and oxaliplatin modulated with leucovorin (FOLFOX). On the basis of our previous studies, where small molecules to suppress colorectal cancer (CRC) via degrading both β-catenin and RAS were developed, we tested the effectiveness of KYA1797K, a representative compound functioning by binding axin, in the growth of GC cells. The efficacy test of the drugs using gastric tumor organoids of Apc(1638N) mice showed that the CD44 and ALDH1A3 cancer stem cell markers were induced by FOLFOX, but not by KYA1797K. KYA1797K also efficiently suppressed tumors generated by re-engrafting the FOLFOX-resistant patient-derived xenograft (PDX) tumors, which also showed resistance to paclitaxel. Overall, the small-molecule approach degrading both β-catenin and RAS has potential as a therapeutic strategy for treating GC patients resistant to current standard chemotherapies.