Search

Resistance to anti-androgen therapy is associated with increased expression of androgen receptor (AR) mRNA, AR gene amplification or AR mutation. Increased AR levels are necessary and sufficient to promote hormone-refractory growth in models and, paradoxically, alter the cellular response to classic AR antagonists such that they function as weak agonists. Therefore, second generation antiandrogens must overcome these resistance mechanisms. We searched for novel AR antagonists that might retain function in the context of increased AR expression through a cell-based screen. Using the high affinity AR agonist RU59063 as a starting point, we synthesized and screened over 200 compounds to construct a structure/activity profile that defines features of the scaffold essential for receptor binding and for maximal antagonism. We focused our further efforts on a novel compound MDV3100, which retains potent antiandrogen activity in cells expressing increased levels of AR, blocks AR function in mice and impairs the growth of LNCaP and LAPC-4 xenografts engineered to express high levels of AR, whereas bicalutamide had minimal activity. MDV3100 inhibits AR with 10-fold greater affinity than bicalutamide and functions through a novel mechanism of action that impairs nuclear translocation and DNA binding. MDV3100 produced sustained PSA responses (greater than 50% reduction) in about ∼55 percent of men with castrate-resistant prostate cancer in a 140 patient phase I-II clinical trial. In a phase III registration study of 1119 men with castration resistance, chemotherapy refractory prostate cancer, MDV3100 prolonged survival compared to best supportive care (18.4 months versus 13.6 months; hazard ratio 0.631). The heterogeneity of clinical response to anti-androgen therapy suggests additional molecular determinants of drug resistance. By conducting an integrated genomic analysis of 214 prostate cancers, we have defined a common set of molecular lesions and pathways that may define distinct subsets of prostate cancer as well as responder/non-responder populations to antiandrogen therapy. In preclinical models we found that tumors with PTEN loss are relatively insensitive to androgen ablation therapy due to reciprocal negative feedback between the AR and PI3K signaling pathways. PTEN-mediated resistance can be overcome with combined AR + PI3K pathway inhibition. Studies of these and other molecular abnormalities reveal unique features of prostate cancer progression with implications for downstream drug development. References Chen CD, Welsbie DS, Tran C, Baek SH, Chen R, Vessella R, Rosenfeld MG, Sawyers CL. Molecular determinants of resistance to antiandrogen therapy. Nat Med. 2004 Jan;10(1):33-9. Epub 2003 Dec 21. PMID: 14702632. Tran C, Ouk S, Clegg NJ, Chen Y, Watson PA, Arora V, Wongvipat J, Smith-Jones PM, Yoo D, Kwon A, Wasielewska T, Welsbie D, Chen CD, Higano CS, Beer TM, Hung DT, Scher HI, Jung ME, Sawyers CL. Development of a second-generation antiandrogen for treatment of advanced prostate cancer. Science. 2009 May 8;324(5928):787-90. Epub 2009 Apr 9. PMID: 19359544. Scher HI, Beer TM, Higano CS, Anand A, Taplin ME, Efstathiou E, Rathkopf D, Shelkey J, Yu EY, Alumkal J, Hung D, Hirmand M, Seely L, Morris MJ, Danila DC, Humm J, Larson S, Fleisher M, Sawyers CL; Prostate Cancer Foundation/Department of Defense Prostate Cancer Clinical Trials Consortium. Antitumour activity of MDV3100 in castration-resistant prostate cancer: a phase 1-2 study. Lancet. 2010 Apr 24;375(9724):1437-46. Epub 2010 Apr 14. PMID: 20398925. Taylor BS, Schultz N, Hieronymus H, Gopalan A, Xiao Y, Carver BS, Arora VK, Kaushik P, Cerami E, Reva B, Antipin Y, Mitsiades N, Landers T, Dolgalev I, Major JE, Wilson M, Socci ND, Lash AE, Heguy A, Eastham JA, Scher HI, Reuter VE, Scardino PT, Sander C, Sawyers CL, Gerald WL. Integrative genomic profiling of human prostate cancer. Cancer Cell. 2010 Jul 13;18(1):11-22. Epub 2010 Jun 24. PMID: 20579941. Carver BS, Chapinski C, Wongvipat J, Hieronymus H, Chen Y, Chandarlapaty S, Arora VK, Le C, Koutcher J, Scher H, Scardino PT, Rosen N, Sawyers CL. Reciprocal Feedback Regulation of PI3K and Androgen Receptor Signaling in PTEN-Deficient Prostate Cancer. Cancer Cell. 2011 May 17;19(5):575-86. PMID:21575859. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr PL04-01. doi:1538-7445.AM2012-PL04-01

Inhibition of the androgen receptor (AR) results in activation of the PI-3K/mTOR pathway in PTEN deficient prostate cancer cells by reciprocal feedback inhibition (Carver BS, 2011). Enzalutamide or PI-3K/mTor inhibition result in feedback activation and combined inhibition abrogated this effect. We explored AR inhibition in CRPC cell lines with low, intermediate and high AR expression in the context of PI-3K/mTor inhibition to identify biomarkers of response and resistance. We utilized no/low (DU145, PC3), intermediate (LNCaP) and high (22Rv1,VCap) AR expressing prostate cancer (PC) cell lines to evaluate anti-tumor activity with 4 pan-PI3K/mTOR inhibitors (GDC-0980, GDC-0941, LY294002, PF-04691502), enzalutamide and abiraterone as single agents or various in combinations at clinically relevant doses. Cytotoxic activity of enzalutamide was more potent than abiraterone (IC50's was < 1µM and > 10µM) in LNCaP cells, however, the opposite was seen in DU145 and PC-3 cell lines. High AR expressing cells (22Rv1, VCap) were more sensitive to AR inhibition. PI-3K/mTor SMIs GDC-0980, GDC-0941 or PF-04691502 had IC50's in the range 50-500nM while LY294002 had an IC50 16-24 µM except for DU145. This cell line had increased IC50 values comparatively for PI-3K/mTor SMIs GDC-0980, GDC-0941 or PF-04691502 (1.5-3.75 µM) and LY29002 (48.5 µM). The combination index (CI) isobologram method indicated significant synergism for PI-3K/mTOR SMIs plus enzalutamide or abiraterone in all PC cell lines irrespective of AR status. Combination treatments were associated with increased apoptosis (Annexin-V staining and PARP-cleavage assay) in LNCaP and VCaP > 22Rv1 > DU145 and PC3. Cell cycle analysis by flow cytometry demonstrated that enzalutamide induces G1 arrest in LNCaP and DU145 cells and G2/M arrest in PC3 cells. PI-3K inhibition induces S arrest in LNCaP and DU145 and G2/M arrest in PC3 cells. The combination of enzalutamide plus PI-3K inhibition enhanced S arrest in LNCaP while in DU145 and PC3, G0/G1 arrest was prominent. PI-3K SMI plus enzalutamide completely inhibited pAkt308/473, pS6 and p4EBP1 in LNCaP cells, pAkt473 in PC3 cells and pS6 and p4EBP1 in 22Rv1 cells. Enzalutamide alone or in combination with PI-3K inhibition also suppressed AR expression in 22Rv1 cells. A 22Rv1 mouse xenograft model is evaluating safety and efficacy of the combination. This is a novel therapeutic strategy for CRPC patients to be evaluated in a clinical trial. Citation Format: Daruka Mahadevan, Carla Morales, Laurence S. Cooke, Bradley Somer, Wenqing Qi. Dual inhibition of the androgen receptor and PI-3K/mTor pathways has significant antitumor activity in castrate-resistant prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 675. doi:10.1158/1538-7445.AM2014-675

laparoscopic biopsy of sentinel lymph node in patients with clinical stage I testicular tumor. J Urol 2002; 168:1390–5. [47] Holman E, Kovacs G, Fiasko T, et al. Hand-assisted laparoscopic retroperitoneal lymph node dissection for nonseminomatous testicular cancer. J Laparoendosc Adv Surg Tech A 2007;17:16–20. [48] Davol P, Sumfest J, Rukstalis D. Robotic-assisted laparoscopic retroperitoneal lymph node dissection. Urology 2006;67:199. [49] Weissbach L, Boedefeld EA, Horstmann-Dubral B. Surgical treatment of stage-I non-seminomatous germ cell testis tumor. Final results of a prospective multicenter trial 1982– 1987. Testicular Tumor Study Group. Eur Urol 1990;17: 97–106. [50] Donohue JP, Foster RS. Retroperitoneal lymphadenectomy in staging and treatment. The development of nervesparing techniques. Urol Clin N Amer 1998;25:461–8. [51] Eggener SE, Carver BS, Sharp DS, Motzer RJ, Bosl GJ, Sheinfield J. Incidence of disease outside modified retroperitoneal lymph node dissection templates in clinical stage I or IIA nonseminomatous germ cell testicular cancer. J Urol 2007;177:937–43. [52] Allaf ME, Bhayani SB, Link R, et al. Laparoscopic retroperitoneal lymph node dissection: duplication of the open technique. Urology 2005;65:575–7. [53] Jewett MA, Kong YS, Goldberg SD, et al. Retroperitoneal lymphadenectomy for testis tumor with nerve sparing for ejaculation. J Urol 1988;139:1220–4.