ST6GAL1 promotes cancer stem-like cell-associated paclitaxel resistance through the EGFR-mTOR-SOX2/BMI1 axis in non-small cell lung cancer

Abstract

Aim: Despite the contribution of cancer stem-like cells (CSLCs) to acquired paclitaxel resistance in non-small cell lung cancer (NSCLC), the biomarkers and regulatory mechanisms sustaining their stemness under chemotherapy pressure remain poorly understood. This study aimed to identify the stemness-maintaining programs underlying CSLC-associated paclitaxel resistance. Methods: Paclitaxel-resistant NSCLC cell models were established. RNA-seq data from resistant spheres and adherent resistant cells were integrated with Gene Ontology/Kyoto Encyclopedia of Genes and Genomes/gene set enrichment analysis and patient transcriptomic datasets to identify CSLC maintenance-associated candidate biomarkers. Inhibitors, sphere-forming assays, CD104-CD166+CD49fhi flow cytometry, reverse transcription quantitative polymerase chain reaction, western blotting, and ST6GAL1 knockdown or overexpression were used for functional and mechanistic validation. Sambucus nigra agglutinin lectin blotting was performed to assess epidermal growth factor receptor (EGFR) α2,6-sialylation. Clinical relevance was assessed using ST6GAL1 immunohistochemistry on 46 clinical lung tumor tissues. Results: Paclitaxel-resistant NSCLC cells exhibited enhanced sphere formation and CD104-CD166+CD49fhi expansion. N-glycosylation was activated in resistant spheres. A seven-gene N-glycosylation signature was identified as a CSLC-associated candidate biomarker in acquired paclitaxel resistance. Inhibiting N-glycosylation suppressed the EGFR-mTOR-SOX2/BMI1 axis, decreased CSLCs, and restored paclitaxel sensitivity. ST6GAL1 regulated EGFR α2,6-sialylation. ST6GAL1 depletion also decreased EGFR abundance, suppressed mTOR-SOX2/BMI1 signaling, and sensitized paclitaxel-resistant spheres to paclitaxel rather than adherent cells. ST6GAL1 expression, which was higher in tumors from patients who underwent chemotherapy, showed a trend toward poorer survival among chemotherapy-treated patients. The seven-gene signature was associated with shorter disease-free survival but not overall survival in lung cancer patients. Conclusions: ST6GAL1-mediated α2,6-sialylation of EGFR contributes to the maintenance of CSLC-associated paclitaxel resistance through mTOR-SOX2/BMI1 signaling. These findings identify ST6GAL1-dependent EGFR sialylation as a potential therapeutic target in CSLC-associated chemoresistance.