TGFB1 and head and neck squamous cell carcinoma: Moreover, cell viability assay showed that TGF-β1 treatment effectively increased the palbociclib resistance (a 1~4-fold increase in IC50 values of palbociclib) in all three HNSCC cell lines, and PI3K inhibitor alpelisib combined with palbociclib could at least partially restore palbociclib sensitivity (Fig. 4e).