TGF-β increases the expression of PTHrP in tumor cells via the TGF-β-Smad signaling pathway and enhances osteoclast generation and bone destruction by upregulating the expression of RANKL in adjacent osteoblasts, which is crucial for establishing the vicious cycle of tumor cell metastasis and bone destruction [142,143,144]. Here, TGFB1 is linked to neoplasm.