Abstract 2431: Co-targeting ROS and CLU-mediated stress response using SMIP004 (a novel inducer of ROS and cancer cell selective apoptosis) and OGX-011 in MDV3100-resistant, castrate-resistant prostate cancer
Authors: Nappi Lucia , Beraldi Eliana , Zhang Fan , Wolf Dieter , Gleave Martin 
Published: August 2015

Prostate cancer is the most common male carcinoma in North America and the second leading cause of cancer related death in men. While new drugs targeting Androgen Receptor (AR), like abiraterone and MDV3100, significantly increase survival of patients with castration resistant prostate cancer (CRPC), many patients still die of metastatic resistant disease. Continued therapeutic improvements towards prolonging the chronicity of CRPC will require characterization of innate and stress-activated survival responses, and rational combinatorial co-targeting strategies designed to abrogate them. OGX-011 is a second generation antisense oligonucleotide targeting Clusterin (CLU) currently under evaluation in phase III clinical trials. CLU is a molecular chaperone involved in endoplasmic reticulum (ER) stress, protein homeostasis and in many signaling and transcriptional survival networks. It is cytoprotective under stress conditions and correlated with treatment resistance in prostate and other cancers. SMIP004 is a novel drug that modulates cell cycle and ER stress and unfolded protein responses (UPR). Some of its fuctions have been correlated to Reactive Oxygen Species (ROS) modulation. However, the exact mechanisms of action of SMIP004 are not completely understood.

Cell survival of LNCaP (castration sensitive), C-42 (castration resistant), M42D, M49F (MDV3100 resistant) and PC3 (AR negative) human prostate cancer cell lines was assessed by crystal violet assay. CLU silencing was obtained by transfecting cells with short interference RNA or OGX011. Western blotting analysis was used to detect proteins expression and RT-QPCR for mRNA levels. ROS were evaluated in live cells after incubation with 2′,7′-DCFDA by FACS Canto II.

Consistent with induction of proteotoxic stress, SMIP004 significantly up-regulated CLU mRNA and protein levels in prostate cancer cell lines sensitive and resistant to MDV3100. SMIP004 as well as MDV3100 were able to increase ROS production. Interestingly CLU silencing, through siRNA or OGX011, inhibited ROS while CLU overexpression, after SMIP004 and/or MDV3100, significantly induced ROS production in MDV3100 sensitive and resistant cells. Moreover SMIP004 efficiently controlled cell survival of MDV3100 sensitive and resistant prostate cancer cells but the combination with clusterin inhibitors had a synergistic effect in these cells. Interestingly, SMIP004 reduced AR variant-7, a AR splicing variant associated with abiraterone and MDV3100 resistance, in both MDV3100 sensitive and resistant cells.

Clusterin plays a central role in ROS tolerance in prostate cancer cells. Clusterin inhibition in combination with SMIP004 is able to control cell survival of MDV-3100 sensitive and resistant cells also trough a modulation of oxydative stress.

Citation Format: Lucia Nappi, Eliana Beraldi, Fan Zhang, Dieter Wolf, Martin Gleave. Co-targeting ROS and CLU-mediated stress response using SMIP004 (a novel inducer of ROS and cancer cell selective apoptosis) and OGX-011 in MDV3100-resistant, castrate-resistant prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2431. doi:10.1158/1538-7445.AM2015-2431