Abstract
IntroductionThe POU class 1 homeobox 1 transcription factor (POU1F1, also known as Pit-1) is expressed in the mammary gland and its overexpression induces profound phenotypic changes in proteins involved in cell proliferation, apoptosis, and invasion. Patients with breast cancer and elevated expression of Pit-1 show a positive correlation with the occurrence of distant metastasis. In this study we evaluate the relationship between Pit-1 and two collagenases: matrix metalloproteinase-1 (MMP-1) and matrix metalloproteinase-13 (MMP-13), which have been related to metastasis in breast cancer.MethodsWe began by transfecting the MCF-7 and MDA-MB-231 human breast adenocarcinoma cell lines with the Pit-1 overexpression vector (pRSV-hPit-1). Afterward, the mRNA, protein, and transcriptional regulation of both MMP-1 and MMP-13 were evaluated by real-time PCR, Western blot, chromatin immunoprecipitation (ChIP), and luciferase reporter assays. We also evaluated Pit-1 overexpression with MMP-1 and MMP-13 knockdown in a severe combined immunodeficiency (SCID) mouse tumor xenograft model. Finally, by immunohistochemistry we correlated Pit-1 with MMP-1 and MMP-13 protein expression in 110 human breast tumors samples.ResultsOur data show that Pit-1 increases mRNA and protein of both MMP-1 and MMP-13 through direct transcriptional regulation. In SCID mice, knockdown of MMP-13 completely blocked lung metastasis in Pit-1-overexpressing MCF-7 cells injected into the mammary fat pad. In breast cancer patients, expression of Pit-1 was found to be positively correlated with the presence of both MMP-1 and MMP-13.ConclusionsOur data indicates that Pit-1 regulates MMP-1 and MMP-13, and that inhibition of MMP-13 blocked invasiveness to lung in Pit-1-overexpressed breast cancer cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-014-0505-8) contains supplementary material, which is available to authorized users.
Highlights
The POU class 1 homeobox 1 transcription factor (POU1F1, known as Pit-1) is expressed in the mammary gland and its overexpression induces profound phenotypic changes in proteins involved in cell proliferation, apoptosis, and invasion
Pit-1 regulates matrix metalloproteinase-1 (MMP-1) and matrix metalloproteinase-13 (MMP-13) messenger RNA (mRNA) and protein levels in MCF-7 and MDA-MB-231 cell lines To evaluate the effect of Pit-1 on matrix metalloproteinases (MMPs)-1 and MMP-13 mRNA expression, we carried out a real-time polymerase chain reaction (PCR)
It has previously been demonstrated that patients with breast cancer and overexpression of the Pit-1 transcription factor are associated with higher occurrence of distant metastasis, but the mechanisms remain unknown
Summary
The POU class 1 homeobox 1 transcription factor (POU1F1, known as Pit-1) is expressed in the mammary gland and its overexpression induces profound phenotypic changes in proteins involved in cell proliferation, apoptosis, and invasion. Patients with breast cancer and elevated expression of Pit-1 show a positive correlation with the occurrence of distant metastasis. In this study we evaluate the relationship between Pit-1 and two collagenases: matrix metalloproteinase-1 (MMP-1) and matrix metalloproteinase-13 (MMP-13), which have been related to metastasis in breast cancer. Breast cancer cells need, among other steps, to break their intercellular adhesion complexes and basement membrane to acquire motility to invade adjacent tissues [1]. Proteolytic enzymes of various classes (metallo, aspartic, cysteine, serine, and threonine) execute the breaking down of matrix elements. Nielsen et al [11] reported that MMP-13 expression by myofibroblasts was often associated with microinvasive events, and they proposed that MMP-13 may play an essential role during the transition from ductal carcinoma in situ lesions to invasive ductal carcinoma of the breast
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