<p>Supplementary Table and Figures: Table S1: Prostate cancer tumor microarray characteristics Fig. S1: IRS antibody validation Fig. S2: Effect of NT157 on the viability of benign prostatic cell line Fig. S3: Immunoblot analysis of cell cycle markers Fig. S4: NT157 inhibits LNCaP xenograft growth and delays CRPC Table S2: Growth rate calculation for NT157 treated xenografts Fig. S5: NT157 treatment of LNCaP Xenograft has no effect on mice body weight Fig. S6: NT157 potentiates docetaxel activity in PC3 xenografts Table S3: Growth rate calculation for NT157 and Docetaxel treated PCs xenografts Fig. S7: Growth rate calculation for NT157 and Docetaxel treated PCs xenografts Fig. S8: NT157 treatment of PC3 xenograft tumors has no effect on mice body weight</p>
ARTICLE ABSTRACT
Insulin-like growth factor (IGF) signaling is associated with castrate-resistant prostate cancer (CRPC) progression. Insulin receptor substrates 1 and 2 (IRS1/2) mediate mitogenic and antiapoptotic signaling from IGF1 receptor (IGF1R), insulin receptor, and other oncoproteins. This study demonstrates that IRS1/2 expression is increased in prostate cancer, and persists in CRPC. Furthermore, this study assesses the anticancer activity of NT157, a small molecule tyrphostin targeting IRS proteins, using androgen-responsive (LNCaP) and -independent (PC3) prostate cancer cells in vitro and in vivo. NT157 treatment resulted in dose-dependent inhibition of IGF1R activation, suppression of IRS protein expression, inhibition of IGF1-induced AKT activation, but increased ERK activation in NT157-treated cells in vitro. These effects were correlated with decreased proliferation and increasing apoptosis of LNCaP cells and increasing G2–M arrest in PC3 cells. NT157 also suppressed androgen-responsive growth, delayed CRPC progression of LNCaP xenografts, and suppressed PC3 tumor growth alone and in combination with docetaxel. This study reports the first preclinical proof-of-principle data that this novel small molecule tyrosine kinase inhibitor suppresses IRS1/2 expression, delays CRPC progression, and suppresses growth of CRPC tumors in vitro and in vivo. Demonstration that IRS expression can be increased in response to a variety of stressors that may lead to resistance or reduced effect of the therapies indicate that NT157-mediated IRS1/2 downregulation is a novel therapeutic approach for management of advanced prostate cancer. Mol Cancer Ther; 13(12); 2827–39. ©2014 AACR.
