Abstract 669: Anticancer effects of novel non steroidal glucocorticoid receptor ligand, Compound A, in T-cell leukemia lines

Abstract

Abstract Glucocorticoids (GCs) are widely used in chemotherapy of hematologic malignancies, including T cell leukemia. The biological effects of GCs are mediated by the glucocorticoid receptor (GR), a well known transcription factor. Therapeutic effects of GCs are mainly mediated via GR transrepression that involves negative interaction between GR and other transcription factors. In contrast, side effects of glucocorticoids are mediated by GR transactivation that requires binding of GR homodimer to hormone-responsive elements in gene promoters. Selective GR activators (SEGRA) that shift GR functions towards transrepression have improved therapeutic index and hold a great potential for the GR-targeted chemotherapies. Recently we and others characterized a novel non-steroidal GR ligand, 2-(4-acetoxyphenyl)-2-chloro-N-methylethylammonium chloride also called Compound A (CpdA). CpdA prevents GR dimerization and transactivation, but strongly enhances GR transrepression. We also revealed that CpdA possesses anti-cancer activity: it inhibited growth and viability of prostate cancer cells in GR-dependent fashion. Here we analyzed CpdA effects in K562 and CEM T-cell leukemia lines. We found that both cell lines express functional GR. CpdA at 10-6-10-5M concentration range exerted cytostatic and apoptotic effects in both cell lines. CEM cells were more sensitive to CpdA than K562 that correlated with the higher amount of GR protein in these cells. We found that in contrast to GCs, CpdA did not induce GR transactivation evaluated by RT-PCR of known GR-target genes such as FKBP51. At the same time, Luciferase assay showed that CpdA efficiently activated transrepression of NF-kB and AP-1 factors. Currently, GCs are used for the treatment of blood cancers in combined chemotherapy with different anti-cancer drugs including proteasome inhibitor Bortezomib (BZ). It is known that proteasome inhibitors increase GR stability. Thus, we expected that BZ will maximize ligand properties of CpdA as GR modulator and will increase its anti-cancer effects. We found that BZ induced caspase-dependent apoptosis in both T-cell leukemia cell lines. The effect of BZ on GR expression and function and on apoptosis induced by CpdA is under study. In addition, we have performed Ames test and Topoisomerase I assay as first steps towards the evaluation of toxicological profile of CpdA. We have not revealed mutagenic effect of CpdA either in frameshift or in base-substitution indicator strains at the wide range of concentrations (10-9-10-4M). CpdA also did not inhibit eukaryotic topoisomerase I activity. Overall, our data suggest that novel GR modulator CpdA has a high chemotherapeutic potential for the treatment of T-cell leukemia. The detailed mechanisms of its anti-cancer effects in transformed T-cells are under investigation. Work is supported by grants: RFBR 10-04-00979, RO1CA118890, ACS IL 160185, UICC ICRETT-09-137. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 669. doi:10.1158/1538-7445.AM2011-669