Progestin favor development of breast tumor metastasis via progesterone receptor nongenomic actions

ROMINA CARNEVALE; ROXANA SCHILLACI; ALEJANDRO J. URTREGER; MARTIN RIVAS; CINTHIA ROSEMBLIT; CECILIA PROIETTI; WENDY BÉGUELIN; V. BOONYARATANAKORNKIT; DEAN P. EDWARDS; ELISA D. BAL DE KIER JOFFÉ; PATRICIA ELIZALDE

Los Angeles, EEUU.

Congreso; 98th Annual Meeting of the American Associaton for Cancer Research; 2007

American Associaton for Cancer Research (AACR)

Accumulating evidence indicates that progestins exert rapid nongenomic effects modulating a variety of cellular functions. Recently we demonstrated that progestin-rapid activation of MAPKs and PI-3K/Akt signaling pathways resulted in the induction of breast cancer cell proliferation. To explore which of the progesterone receptor (PR) functions, either as transcription factor or as activator of signaling pathways, were involved in the regulation of progestin responses, we performed reconstitution experiments with wild-type (wt)PR-B, with transcriptionally impaired mutant C587A-PR and with mutant PR-BmPro, which lacks the ability to activate cytoplasm signaling. Here, we assessed medroxyprogesterone acetate (MPA) regulation of breast cancer cell proliferation and survival, proteases activity and in vivo development of experimental metastasis. We performed this study in the PR null murine mammary metastatic tumor line LM3. These cells were transiently transfected with wtPR-B (LM3-PRB), C587A-PR (LM3-C587A-PR), PR-BmPro (LM3-PR-BmPro) or with an empty vector. We first studied MPA effect in LM3 cell proliferation by incorporation of [3H] thymidine. MPA (10nM) treatment induced LM3 cell proliferation, via MAPK and PI-3K/Akt pathways, in cells expressing wt PR-B or transcriptionally impaired C587A-PR. In contrast, in cells expressing PR-BmPro, progestins did not induce cell growth. Using a clonogenic assay, we observed that MPA significantly increased survival of both LM3-PR and LM3-C587A-PR while no effect was observed in LM3-PR-BmPro survival. We next studied the effect of MPA treatment on urokinase-like plasminogen activator (uPA) activity by casein and plasminogen zymography. Treatment of LM3-PR-B and LM3-C587A-PR cells with MPA reduced uPA activity via MAPK and PI-3K/Akt pathways. MPA-inhibition of uPA activity in LM3-PR-BmPro cells was significantly lower as compared with LM3-PR-B and LM3-C587A-PR cells. Finally, we used an in vivo experimental metastasis system in which we evaluated the ability of LM3 cells to form lung metastasis. LM3 cells transfected with empty vector, PR-B, C587A-PR, PR-BmPro, or wt LM3 cells were injected into the tail vein of mice. At day 28 the number of superficial lung nodules was counted. We found that either wtPR-B, C587A-PR or PR-BmPro expression decreased the number of lung metastasis. Treatment with 40mg MPA depot increased the metastatic capacity of LM3-PR and LM3-C587A-PR cells while no modulation of LM3-PR-BmPro metastatic capacity was observed. These results demonstrated for the first time that progestins favor development of breast tumor metastasis via PR function as activator of signaling pathways. Our present findings provide mechanistic support to the design of a novel therapeutic intervention in PR-positive breast tumors involving blockage of PR capacity to activate cytoplasmic signaling.