Single-cell analysis identifies BASP1 as a driver of drug resistance and cell plasticity in oral squamous cell carcinoma.

Despite initial positive responses with chemotherapy, many cancer patients experience relapse, continued tumor growth, and metastatic spread due to drug resistance. It is well documented that a rare population of phenotypically heterogeneous cells contributes to intratumour heterogeneity and drug resistance. To date, these rare populations are poorly characterized. To identify the potential role of these rare populations in drug resistance, here we have performed single-cell RNA sequencing of human oral squamous cell carcinomas lines presenting with sensitive, early, and late cisplatin-resistance patterns. The single-cell RNA-sequencing data identified two different transitional clusters within the three, sensitive, early, and late cisplatin-resistant major clusters. The differential gene expression profile and deregulated pathways analysis suggested Brain Abundant Membrane-Attached Signal Protein 1 (BASP1) as a major upregulated gene not only in major drug-resistant clusters but also in transitional clusters. Selective knockdown of BASP1 reverses epithelial to mesenchymal transition (EMT) phenotype in cisplatin-resistant cells and restores cisplatin-induced cell death. Mechanistically, BASP1 positively regulates LIN7A expression through phosphorylation of RAC-alpha serine/threonine-protein kinase as well as by supressing microRNA hsa-mir-501-3p, which in turn induces β-catenin-mediated EMT in chemoresistant cells. Overall, our study demonstrates that BASP1 acts as a key regulator of EMT in cisplatin-resistant oral squamous cell carcinoma and represents a promising therapeutic target to overcome drug resistance in advanced stages of the disease.