Triple-Negative Breast Cancer (TNBC) Cell Metastasis is Controlled by the Opposing Actions of 5alpha-dihydroprogesterone (5alphap) and 3alpha-dihydroprogesterone (3alphahp) on Expression of Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases

Abstract BackgroundTriple receptor-negative breast cancers (TNBC) comprise up to 20% of all breast cancers and are the most aggressive mammary cancer subtype, marked by early-onset metastasis, high tumor recurrence rate, and low overall survival. Because TNBC cells lack expression of the estrogen receptor (ER), progesterone receptor (PR) and excess human epidermal growth factor receptor 2 (HER2), there have been no hormone-based explanations and therapeutics for TNBC. Our previous studies had shown that the endogenously produced hormones, 5αdihydroprogesterone (5αP) and 3α-dihydroprogesterone (3αHP), respectively, stimulate and inhibit TNBC cell proliferation and primary tumor development. Here we examined the role of 5αP and 3αHP in controlling metastasis of TNBC (MDA-MB-231)human breast cells. The objectives were to determine the effects of 5αP and 3αHP on TNBC cell (a) adhesion, migration and invasion and (b) expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs).MethodsMDA-MB-231 human breast cells were incubated in medium without (control) or with 5αP or 3αHP. Effects on adhesion were examined by previously validated detachment assays. Effects on migration and invasion were measured by transwell assays employing modified Boyden chambers. Effects on expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 were determined by reverse transcription polymerase chain reaction (RT-PCR).Results5αP stimulated, whereas 3αHP suppressed, TNBC cell detachment, migration and invasion. 5αP stimulated expression of MMP-2 and MMP-9, and inhibited expression of TIMP-1 and TIMP-2, whereas 3αHP inhibited expression of MMPs and stimulated expression of TIMPS.ConclusionsHere we show for the first time that 5αP stimulates and 3αHP suppresses the key elements of metastasis (adhesion, migration, invasion) in TNBC cells, and that these opposing actions correlate with the opposing effects of these two hormones on MMP and TIMP expression. The results indicate that the relative concentrations of the cancer-promoter hormone (5αP) and the cancer-suppressor hormone (3αHP) in the breast microenvironment control TNBC cell metastasis, and suggest that blocking 5αP synthesis and increasing 3αHP concentrations in the breast microenvironment could provide the first hormone-based therapeutic regimen to arrest TNBC progression and metastasis.