TGFB1 and prostate cancer: The constitutive activation of TGF‐β pathway has been widely documented to participate in bone metastasis of multiple types of cancers, such as prostate cancer and breast cancer (Dai et al., 2017; Fournier et al., 2015; Kang et al., 2005; Korpal et al., 2009; Yin et al., 1999), and therapies targeting TGF‐β can effectively reduce metastasis of tumor cells to bone (Hu et al., 2012; Wan et al., 2012).