BDNF and neoplasm: Moreover, reciprocal communication between CAFs and tumor cells is required, where CAFs, in turn, upregulate tumor stimulating mediators (vimentin, matrix metalloproteinases, periostin, IGF2, BDNF, IL-33, and CXCL12), which are important for tumor growth, invasion and downregulation of tumor suppressor genes, like p53 and p21 [8, 9, 11].