Recent findings have shown that inhibitors targeting BET (bromodomain and extraterminal domain) proteins, such as the small molecule JQ1, are potent growth inhibitors of many cancers and hold promise for cancer therapy. However, some reports also have revealed that JQ1 can activate additional oncogenic pathways and may affect EMT (epithelial mesenchymal transition). Therefore, it is important to address the potential unexpected effect of JQ1 treatment, such as cell invasion and metastasis. Here, we showed that in prostate cancer, JQ1 inhibited cancer cell growth but promoted invasion and metastasis in a BET protein independent manner. Multiple invasion pathways including EMT, BMP (bone morphogenetic protein) signaling, chemokine signaling and focal adhesion pathway were activated by JQ1 to promote invasion. Notably, JQ1 induced upregulation of invasion genes through inhibition of FOXA1, an invasion suppressor in prostate cancer. JQ1 directly interacted with FOXA1, inactivated FOXA1 binding to its interacting repressors, TLE3, HDAC7, and NFIC, thus blocking FOXA1 repressive function and activating the invasion genes. Our finding indicates that JQ1 has an unexpected effect of promoting invasion in prostate cancer. Thus, the ill effect of JQ1 or its derived therapeutic agents cannot be ignored during cancer treatment, especially in FOXA1 related cancers.
Leiming Wang, Mafei Xu, Chung-Yang Kao, Sophia Y. Tsai, Ming-Jer Tsai