['In the present study, we made an attempt to elucidate the role of oversecretion of interleukin-4 (IL-4) in cancer stem cells (CSCs) of head and neck squamous cell carcinoma (HNSCC).', 'HNSCC samples were analyzed for the presence of CSCs by flow cytometry. In addition, we have performed drug and apoptosis resistance assays to determine the role of IL-4 in CSCs.', 'HNSCC samples contained 3.3% of CD133+ cancer stem like side population (SP) cells in HNSCC which displayed infinite cell proliferation and they had high self-renewal capacity. These CD133+ cells displayed enhanced expression of IL-4, which promoted multidrug and apoptosis resistance. After neutralizing IL-4, the CD133+ SP cells became more sensitive to drug treatment and apoptosis.'] Does constitutive secretion of Interleukin-4 dictate CD133+ side population cells to resist drug treatment and cell death?