HIF1A and neoplasm: In addition, implantation of H358 tumor cells in vivo gave rise to tumors staining positive for TMPRSS4 protein (Fig. 5) suggesting that expression of TMPRSS4 within the tumor microenvironment may be promoted by hypoxic conditions as demonstrated in the metastatic hepatocyte carcinoma xenograft model in which elevated TMPRSS4 gene and protein product correlate to the HIF-1α expression level (25).