The Mechanism Of Chemo-resistance Results From Androgen Receptor Splicing Variants And The Study Of New Reagents For Prostate Gancer

PART1: Prostate cancer (PCa) is the second leading cause of cancer-relateddeath among men in the United States. The standard first-line treatment for prostatecancer (PCa) is androgen deprivation therapy (ADT), by surgical or chemicalmethod, to reduce the level of circulating androgens or to block the binding ofandrogens to androgen receptor (AR), which suppresses AR transcriptional activity.Unexpectedly, researchers observe diverse evidence that tumors continue to rely onAR signaling in this androgen-depleted environment. And most patients will developadvanced stages of the disease, such as castration-resistant prostate cancer (CRPC),which is basically more aggressive after ADT treatment, and chemo-resistanceprostate cancer which is briefly more malignant after chemotherapy several years.Recently, reseachers reveals that AR splicing variants (ARVs) play an important rolein CRPC and chemo-resistace prostate cancer. Especially, AR-V7and ARV567espredominately express compared to all ARVs in prostate cancer cells, as drives us tostudy on both of them to identify the mechanism of CRPC and chemo-resistaceprostate cancer caused by ARVs.Our results indicated that AR, AR-V7and ARV567eslead to activited ARsignaling pathway, AR transcription activity and increasing tumor cells growth inandrogen presence condition. But in the andogen depleted condition, the activities ofAR are inhibited while ARVs keep their antivities. In addition, to identify themechanism of chemo-resistance prostate cancer we compare the response of AR andARVs to taxels, such as Paclitaxel (PTX) and Docetaxel (DTX). The taxels caninhibit AR on transcription acitivities, downstream gene expression and tumor cellsgrowth with or without androgen. But taxels have no effect on those funtions of ARVs. Surprisingly, ARVs can facilitate AR nuclear translocation and help AR toescape from inhibition of taxels. To reveal the reason why AR and ARVs havedifferent respond to taxels, we carry out microtubule in vivo and in vitro bindingassay involved in AR and ARVs. We find that AR can directly bind withmicrotubule but ARVs can’t bind with microtubule.Then we generate a series of ARdeletions, which respectively contain different functional domains. To compare thedifference between microtubule binding ability of these AR deletions, we illustratethat AR734-AR774is the microtubule association sequence (MTAS) of AR.Moreover, the cellular distributions of AR functional deletions show thatAR734-AR774plays an important role to cytoplasmic resident of proteins, thus weconclude that the MTAS is in AR734-AR774. In sum, our study reveals themechanism that chemo-resistance of prostate cancer results from ARVs expression.And our study is very important for prostate cancer therapy. PART2: According to the recent clinical evidence, Src highly expresses inprostate cancer. In particular, Src may be playing an important role inandrogen-independent tumor growth during CRPC and prostate cancer metastasis tobone. The non-receptor protein tyrosine kinase Src and its family members (Srcfamily kinases, SFKs) have been reported as an up-regulator in prostate cancer, withincreasing activity of Src in the progressive stages of the disease. Currently, KX-01(KX2-391, Kinex Pharmaceuticals) as a Src kinase inhibitor is undergoing clinical trials for the treatment of solid tumors. A novel peptidomimetic class of Src inhibitor,KX-01, targets the peptide substrate site and exhibits more complete specificity forSrc when compared to other clinical Src inhibitors. KX-01represents a novel class ofclinical Src inhibitor that has recently completed Phase1clinical trial testing forsolid tumors. In this study, we identify the mechanism that KX-01suppresses the ARsignaling pathway, AR and ARVs transcription activities and cell growth when ARand ARVs express in these cells. Furthermore, we identify that the inhibition ofKX-01results from KX-01reduce the synthesis of mRNA of AR and ARVs. Andbecause mRNA synthesis of ARVs is dependent on mRNA of AR, KX-01perhapshas more powerfull inhibition on ARVs than on AR. In sum, KX-01is not only apotential drug for thereputic of prostate cancer, but also for recrudescent orrefractory prostate cancer. This is firstly reported.