21-OH 6,19-epoxyprogesterone: A new dissociated glucocorticoid with anti-inflammatory properties but without antiapoptotic effects on chemotherapeutically treated mouse mammary tumor cells.

ORQUEDA A; VELEIRO A,; BAL DE KIER JOFFE E,; KORDON E,; BURTON G,; PECCI A.

Boston Massachussets, USA,

Congreso; Frontiers in Basic Cancer Research. American Association for Cancer Research,; 2009

Glucocorticoids (GC) are widely used as coadyuvants in the treatment of solid tumors with chemotherapics such as paclitaxel (PXL) and doxorubicin (DOXO). However, clinical evidence supports the idea that GCs may induce resistance to the antitumor therapy. To improve  pharmacological significance, intense efforts have been made to design new dissociated steroids (steroid receptor glucocorticoid modulators (SRGMs)), able to differentially modulate glucocorticoid activity by retaining their beneficial effects but without the undesired ones. Previously we showed that the well used GC dexamethasone (Dex) inhibits apoptosis induced by PXL or DOXO in breast tumor cells through a mechanism involving Bcl-XL and Bcl-2 induction. 21-OH-6,19-epoxyprogesterone (21-OH-6,19-OP) is a rigid steroid considered a passive glucocorticoid antagonist. Molecular dynamic simulation studies predicted that 21OH-6,19OP is unable to induce GR/21-OH-6,19-OP complex homodimerization and/or binding to co-activators, making these  complex incapable to directly activate gene transcription. Here, we investigated the effects of 21-OH-6,19-OP on apoptosis induced by DOXO or PXL in the epithelial mouse mammary tumor cell line LM3 by analyzing Caspase-3 activity and gene and protein expression of antiapoptotic members Bcl-2 y Bcl-XL. The results show that, contrary to Dex, 21-OH-6,19-OP cannot reverse apoptosis induced by DOXO or PXL in LM3 cells. In fact, 21-OH-6,19-OP and Dex differentially regulate Bcl-2 and Bcl-XL expression. Dex´s reversion on chemotherapic induced apoptosis (Dex+DOXO o Dex+PXL) correlates with an increase in Bcl-XL levels while 21-OH-6, 19-OP does not affect neither cell death nor Bcl-XL levels. Importance of Bcl-XL involvement in DOXO resistance of cells treated with Dex was confirmed by knocking-down Bcl-XL with specific siRNA. Silencing Bcl-XL expression directly implicated loss of antiapoptotic GC effects. On the other hand, 21-OH-6,19-OP antiinflammatory action was also evaluated on the lung epithelial tumor cell line A549 by determining Interleukin-8 (IL-8) and Cyclooxygenase-2 (COX-2) expression in the presence of  the Tumor Necrosis Factor-alpha (TNF-α). Expression levels of IL-8 and COX-2, measured by qRT-PCR, indicate that 21-OH-6,19-OP may have antiinflammatory effects as it reverses these inflammation markers expression induced by TNF-α in lung epithelial cells.Together these findings suggest that 21-OH-6,19-OP is a SRGM keeping glucocorticoid antiinflammatory properties, but unable to retain antiapoptotic effects, thus becoming a novel candidate for treatment of solid tumors as breast cancer.