Anti-cancer activity of novel selective glucocorticoid receptor agonist 13S-G2 in vitro on the model of blood cancer

Background
Glucocorticoids (GCs) are widely used in the treatment of hematological malignancies as well as in the systemic therapy of autoimmune and inflammatory diseases. The therapeutic effects of GCs are realized via glucocorticoid receptor (GR) activation by DNA-independent transrepression (TR), while their side effects are associated with transactivation (TA). Side effects could be reduced by developing selective glucocorticoid receptor agonists (SEGRAs), acting via the activation of TR. Recently, we synthesized a novel compound, 2-(hexylamino)-1-(4-nitrophenyl)ethanol (13S-G2), which was a derivative of synephrine, and its biological activity was studied in leukemia and lymphoma cells in vitro.
Methodology
The effect of 13S-G2 on the viability of chronic myeloid leukemia (CML) K562 cells and B-cell lymphoma Granta-519 cells was evaluated using the MTT assay. TA induction was assessed by quantitative PCR (qPCR) of GR-dependent genes (GILZ, FKBP51, REDD1/DDIT4). TR induction was studied using a luciferase reporter assay (with NF-κB reporter construct) and qPCR analysis of key TR marker genes (COX2, IL-1α, IL-6, CCNE1). The affinity of 13S-G2 was assessed in silico by molecular docking (Molegro Virtual Docker), and in vitro via a radioligand binding assay.
Results
Compound 13S-G2 showed cytotoxicity with IC50 values of 184±95 μM in K562 and 26.8±1.2 μM in Granta-519. In silico, we demonstrated that 13S-G2 occupied a sterically advantageous location at the GR binding site formed by the amino acid residues Arg611, Asn564, and Gln642. In a radioligand binding assay (IC50), the radiolabeled Dexamethasone displacement in K562 cells by 13S-G2 was 0.69 μM. The inhibitory effect of 13S-G2 on luciferase activity was 55% in K562 and 15% in Granta-519. Compound 13S-G2 suppressed the expression of TR marker genes, in most cases by 1.5-2.0 fold. The absence of TA induction was proved for 13S-G2.
Conclusions
The novel SEGRA 13S-G2 demonstrates promising transrepression-driven anti-cancer activity in hematological malignancies with the absence of TA induction and low potential for side effect development.