Supplementary Methods. Supplementary Figure 1. Chemical structures of the small molecule IST5-002 analogs. Supplementary Figure 2. IST5-002 inhibits phosphorylation of Stat5 in mouse and human breast cancer cells. Supplementary Figure 3. IST5-002 does not have significant inhibitory activity against 50 kinases tested. Supplementary Figure 4. IST5-002 does not affect phosphorylation of Pak1/2. Supplementary Figure 5. IST5-002 inhibits expression of Stat5 target genes in PC cells and in CML cells. Supplementary Figure 6. IST5-002 is not generally cytotoxic as determined by lack of cell death induction in cancer cell lines established from other organs. Supplementary Figure 7. CWR22Rv1 PC cells were inoculated subcutaneously into the flanks of castrated athymic nude mice supplied with sustained-release 5alpha-dihydrotestosterone (DHT)-pellets (n=10/group, 1 tumor/mouse, 1.5 ??107 CWR22Rv1 cells per site, 1 DHT pellet/mouse). Supplementary Figure 8. IST5-0-02 induces apoptosis in CWR22Rv1 tumors grown in nude mice and in clinical PCs cultured ex vivo in organ explant cultures. Supplementary Figure 9. IST5-002 induces extensive apoptotic death of imatinib-sensitive and -resistant CML cells.
ARTICLE ABSTRACT
Bypassing tyrosine kinases responsible for Stat5a/b phosphorylation would be advantageous for therapy development for Stat5a/b-regulated cancers. Here, we sought to identify small molecule inhibitors of Stat5a/b for lead optimization and therapy development for prostate cancer and Bcr-Abl–driven leukemias. In silico screening of chemical structure databases combined with medicinal chemistry was used for identification of a panel of small molecule inhibitors to block SH2 domain–mediated docking of Stat5a/b to the receptor-kinase complex and subsequent phosphorylation and dimerization. We tested the efficacy of the lead compound IST5-002 in experimental models and patient samples of two known Stat5a/b-driven cancers, prostate cancer and chronic myeloid leukemia (CML). The lead compound inhibitor of Stat5-002 (IST5-002) prevented both Jak2 and Bcr-Abl–mediated phosphorylation and dimerization of Stat5a/b, and selectively inhibited transcriptional activity of Stat5a (IC50 = 1.5μmol/L) and Stat5b (IC50 = 3.5 μmol/L). IST5-002 suppressed nuclear translocation of Stat5a/b, binding to DNA and Stat5a/b target gene expression. IST5-002 induced extensive apoptosis of prostate cancer cells, impaired growth of prostate cancer xenograft tumors, and induced cell death in patient-derived prostate cancers when tested ex vivo in explant organ cultures. Importantly, IST5-002 induced robust apoptotic death not only of imatinib-sensitive but also of imatinib-resistant CML cell lines and primary CML cells from patients. IST5-002 provides a lead structure for further chemical modifications for clinical development for Stat5a/b-driven solid tumors and hematologic malignancies. Mol Cancer Ther; 14(8); 1777–93. ©2015 AACR.
