To further investigate whether Sema4D can directly induce production of TGF-β1 by HNSCC cells and conversely if inhibition of Sema4D would affect the production of TGF-β1 by tumor cells, we used the HN6 stable Sema4D knockdown and controls [54]. The gene discussed is TGFB1; the disease is head and neck squamous cell carcinoma.