Targeting Cancer Stem Cell and Its Fibroblast Niche in Chemoresistance of Head and Neck Squamous Cell Carcinoma

Present study revealed the role of cancer stem cell enrichment and its fibroblast niche influence in chemoresistance of oral squamous cell carcinoma. In-vitro cell line model of dysplasia (early carcinogenesis) developed from 4NQO induced carcinogenesis mice tongue model system, and in chemo-therapy induced acquired chemo-resistant cell line model, revealed the enrichment of CSCs genes (CD44, CD133, Aldh1a1, Notch1, CXCR4, Sox2, Oct4, and Nanog) and increased aggressiveness in terms of tumorigenicity, and functional properties like clone formation and migration capacity of the oral cells. Targeting these CSC population in dysplastic cells (Notch1 pathway), significantly reduced the proliferation, and functional properties of severe dysplastic cells. Targeting the Aldh1a1 expression using si-RNA Aldh1a1 and small molecule inhibitor NCT-501, showed a significant reduction in tumorigenic, proliferation, multi drug resistant (MDR) gene (MDR1, MRP2, ERCC1, thymidine synthatase, survivin, etc) expressions, and functional properties by characteristic reduction in other CSC gene expression in an in-vitro, ex-vivo and in-vivo model system. Upon culturing the dysplastic cells/ cancer cells, in direct or indirect co-culture system, along with the dysplastic/cancer associated fibroblast, showed enrichment in CSC, and chemo-resistance gene expression. Targeting CXCR4/SDF-1a pathway based cross-talk between the cancer and CAFs, when abrogated using AMD3100, a small molecule inhibitor, showed significant reduction in MDR gene, CSC gene and functional property reduction in an in-vitro, and ex-vivo model system. Thus, this study showed the importance of cancer stem cell and microenvironment influence on chemo-resistance and a need to upgrade the conventional therapeutic regime from only targeting cancer cells to CSCs and tumor microenvironment in toto.