Testosterone membrane-initiated action in breast cancer cells: Interaction with the androgen signaling pathway and EPOR.

Membrane-initiated androgen actions have now been acknowledged, even though a specific binding site has not been biochemically characterized yet. Recent data indicate that testosterone-BSA, a non-permeable testosterone analog, can exert specific actions in breast cancer cell lines, including proper transcriptional effects, independent of the intracellular androgen sites. In the present work we explore the effects of testosterone-BSA in two specifically modified pathways, revealed by early trascriptome analysis, namely the non-genotropic androgen signaling and the HIF1alpha pathway. We provide evidence that p38 MAPK and PI3K/Akt/NFkappaB and/or Rho/Actin pathways are directly involved in testosterone-induced apoptosis, while the JNK/c-JUN pathway is involved in membrane site-initiated transcription. Furthermore we show that membrane-acting androgens modify the transcription of the erythropoietin receptor (EPOR), leading to erythropoietin-initiated actions. Interestingly, association of recombinant human erythropoietin (rHuEPO) together with testosterone-BSA protects cells from apoptosis, through discrete signaling events. The effect of testosterone-BSA is exerted through the classical erythropoietin promoter, while rHuEPO decreases the transcription of EPOR acting on a newly identified regulatory/promoter region, upstream of its known promoter. These results suggest a new interaction of membrane-acting androgen with EPOR and should be taken into account in the pharmaceutical manipulations of breast cancer patients.