Phosphoinositide-3 kinase alpha-specific inhibitors (PI3Kαi) displayed promising potential for the treatment of esophageal squamous cell carcinoma (ESCC) with frequent activation in PI3K signaling. However, acquired resistance is likely to develop and limit the efficacy of PI3Kαi like other targeted therapies. To identify genomic adaptation to PI3Kαi, we applied whole-genome sequencing and detected gene mutation and amplification in four lines of ESCC cells established with adapted resistance to a novel PI3Kαi CYH33. Particularly, HRAS^G12S mutation was found in KYSE180C cells. Overexpression of HRAS^G12S in ESCC parental cells rendered resistance to CYH33. By contrast, down-regulation of HRAS^G12S restored the sensitivity of KYSE180C1 cells to CYH33, and combination of CYH33 and MEK162 displayed synergistic effect against KYSE180C1 cells and xenografts. Furthermore, elevated mTORC1, mitogen-activated protein kinase (MAPK), and c-Myc signaling pathways were found in resistant cells by RNA sequencing and combination of CYH33 and RAD001, MEK162, or OTX015 overcame the resistance to CYH33, which was accompanied with enhanced inhibition on S6, extracellular signal-regulated kinase 1 (ERK), or c-Myc, respectively. Overall, we characterized the adaptations to PI3Kαi in ESCC cells and identified combinatorial regimens that may circumvent resistance.

磷酸肌醇 3 激酶 α 特异性抑制剂 (PI3Kαi) 显示出治疗食管鳞状细胞癌 (ESCC) 的潜力，PI3K 信号通路频繁激活。然而，与其他靶向疗法一样，获得性耐药可能会发展并限制 PI3Kαi 的疗效。为了鉴定对 PI3Kαi 的基因组适应性，我们应用全基因组测序并检测了四系 ESCC 细胞中的基因突变和扩增，这些细胞系对新型 PI3Kαi CYH33 具有适应性抗性。特别是在KYSE180C细胞中发现了HRAS ^G12S突变。HRAS ^G12S在 ESCC 亲代细胞中的过表达导致对 CYH33 的抗性。相比之下，HRAS ^{G12S 的下调}恢复了 KYSE180C1 细胞对 CYH33 的敏感性，CYH33 和 MEK162 的组合对 KYSE180C1 细胞和异种移植物显示出协同作用。此外，通过RNA测序在耐药细胞中发现升高的mTORC1、丝裂原活化蛋白激酶（MAPK）和c-Myc信号通路，CYH33与RAD001、MEK162或OTX015的组合克服了对CYH33的耐药性，伴随着增强分别抑制 S6、细胞外信号调节激酶 1 (ERK) 或 c-Myc。总体而言，我们表征了 ESCC 细胞对 PI3Kαi 的适应性，并确定了可能规避耐药性的组合方案。