Also, there is a known interplay between IL-13 and TGF-β signaling [13,14], so it will additionally be interesting to examine IL-13-PE treatment in a context where, similar to a subset of human HNSCC patients, the cancer cells are unaffected by the growth inhibitory effects of TGF-β1 and can thereby utilize this cytokine to create a tumor-promoting microenvironment. This evidence concerns the gene IL13 and head and neck squamous cell carcinoma.