PDGFA and hepatocellular carcinoma: It was found that PDGF-α secreted by HCC activated the Ras/ERK signaling pathway in TCs and increased the expression of matrix metalloproteinase-9, which in turn accelerated the invasive metastasis of HCC.[53,54] There is a large distribution of TCs and TPs between the submucosa and smooth muscle cells in bladder cancer.