Purpose: To elucidate the role and molecular mechanism of Numb in prostate cancer (PCa) and the functional contribution of Numb-/low PCa cells in castration resistance.<br /><br />Experimental Design: The expression of Numb was assessed using multiple Oncomine datasets and PCa tissues from both humans and mice. The biological effects of the overexpression and knockdown of Numb in human PCa cell lines were investigated in vitro and in vivo. In addition, we developed a reliable approach to distinguish between PCa cell populations with a high or low endogenous expression of Numb protein using a Numb promoter based lentiviral reporter system. The difference between Numb-/low and Numbhigh PCa cells in the response to androgen deprivation therapy (ADT) was then tested. The likely downstream factors of Numb were analyzed using luciferase reporter assays, immunoblotting and quantitative real-time PCR.<br /><br />Results: We show here that Numb was down-regulated and negatively correlated with PCa advancement. Functionally, Numb played an inhibitory role in xenograft prostate tumor growth and CRPC development by suppressing Notch and Hedgehog signaling. Using a Numb promoter based lentiviral reporter system, we were able to distinguish Numb-/low PCa cells from Numbhigh cells. Numb-/low PCa cells were smaller and quiescent, preferentially expressed Notch and Hedgehog downstream and stem-cell-associated genes, and associated with a greater resistance to ADT. The inhibition of the Notch and Hedgehog signaling pathways significantly increased apoptosis in Numb-/low cells in response to ADT.<br /><br />Conclusions:Numb-/low enriches a castration resistant PCa cell subpopulation that is associated with unregulated Notch and Hedgehog signaling.
http://ift.tt/2uCJcpg
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