YBX1 integration of oncogenic PI3K/mTOR signalling regulates the fitness of malignant epithelial cells [RPPA]. YBX1 integration of oncogenic PI3K/mTOR signalling regulates the fitness of malignant epithelial cells [RPPA]

In heterogeneous head and neck cancer (HNC), subtype-specific treatment regimens are currently missing. An integrated analysis of patient HNC subtypes using single-cell sequencing and proteome profiles revealed an epithelial-mesenchymal transition (EMT) signature within the epithelial cancer-cell population. The EMT signature coincided with PI3K/mTOR inactivation in the mesenchymal subtype. Conversely, the signature was suppressed in epithelial cells of the basal subtype which exhibits hyperactive PI3K/mTOR signalling. We further identified YBX1 phosphorylation, downstream of the PI3K/mTOR pathway, restrains basal-like cancer cell proliferation. In contrast, YBX1 acts as a safeguard against the proliferation-to-invasion switch in mesenchymal-like epithelial cancer cells, and its loss accentuates partial-EMT and in vivo invasion. Interestingly, phospho-YBX1 that is mutually exclusive to partial-EMT, emerged as a prognostic marker for overall patient outcomes. Expression profiling by reverse-phase protein array were performed to explore the underlying molecular mechanisms. Overall design: The reverse-phase protein array analysis of head and neck cancer (HNC) cell lines SCC15 and SCC25 upon YBX1 knockout. The reverse-phase protein array analysis of normal oral cells (OKF6) and HNC cells (SCC15 and SCC25). The reverse-phase protein array analysis of mouse tissues (wildtype, Grhl3cKO, Pik3ca, Pik3caGrhl3cKO tumours and adjacent tissues)

在异质性头颈癌（head and neck cancer, HNC）中，目前尚无针对各亚型的专属治疗方案。本研究通过单细胞测序与蛋白质组谱对患者头颈癌亚型开展整合分析，发现上皮癌细胞群中存在上皮间质转化（epithelial-mesenchymal transition, EMT）特征。该特征与间质亚型中的PI3K/mTOR通路失活相吻合；与之相反，该特征在基底亚型的上皮细胞中受到抑制，而基底亚型的PI3K/mTOR信号通路呈过度激活状态。我们进一步发现，位于PI3K/mTOR通路下游的YBX1磷酸化可抑制基底样癌细胞的增殖。与之相对，YBX1在间质样上皮癌细胞中可作为保护因子，阻止增殖向侵袭表型的转换；而YBX1缺失会加剧部分上皮间质转化（partial-EMT）进程并增强体内侵袭能力。有趣的是，与部分上皮间质转化相互排斥的磷酸化YBX1，可作为患者总体生存结局的预后标志物。本研究通过反相蛋白阵列（reverse-phase protein array）技术开展表达谱分析，以探究潜在的分子机制。整体实验设计如下：1. 对头颈癌（head and neck cancer, HNC）细胞系SCC15与SCC25进行YBX1基因敲除后的反相蛋白阵列分析；2. 对正常口腔细胞OKF6以及头颈癌细胞系SCC15、SCC25开展反相蛋白阵列分析；3. 对小鼠组织（野生型、Grhl3条件性敲除型、Pik3ca突变型、Pik3ca与Grhl3双条件性敲除型肿瘤及癌旁组织）进行反相蛋白阵列分析。