Role of the protein kinase BRAF in the pathogenesis of endometriosis

ABSTRACT

Objective: Mitogen-activated protein kinases (MAPKs) are involved in the proliferation and survival of endometriotic lesions. Vemurafenib (PLX4032) is a novel protein kinase inhibitor that targets BRAF, a member of the MAPK pathway. The present study tested the in vitro and in vivo effects of PLX4032 on endometriotic cells.

Research design and methods: We conducted a laboratory study in a tertiary-care university hospital from January 2013 to September 2013. We enrolled a cohort of 40 patients: 20 with histologically proven endometriosis and 20 unaffected women. A thorough surgical examination of the abdominopelvic cavity was performed on all of the study participants. Ex vivo stromal and epithelial cells were extracted from endometrial and endometriotic biopsies from both sets of patients. Proliferation, apoptosis, pERK/ERK ratio, cell cycle regulation (Cyclin D1 and CDK4) and inflammation (PTGS2) were explored with and without PLX4032 treatment. Human endometriotic lesions were implanted into 40 nude mice that were separated into two groups according to PLX4032 or vehicle treatment, which they received for four weeks, before sacrifice and histological examination.

Results: Treating endometriotic cells with PLX4032 abrogated the phosphorylation of ERK, significantly reducing the pERK/ERK ratio in both epithelial and stromal cells from endometriotic women compared to the controls (p < 0.05). In addition, treatment with PLX4032 significantly decreased proliferation in both stromal and epithelial cells with a concomitant decrease in Cyclin D1/CDK4 complex and PTGS2 levels. Using a murine model of endometriosis, we observed that PLX4032-treated mice displayed a significant decrease in implant volume compared to the initial size; a slight, but non-significant, increase in size was observed in the vehicle-treated mice.

Conclusion: Our data suggest that MAPKs and BRAF are involved in the pathogenesis of endometriosis. PLX4032-induced inhibition of BRAF controlled endometriotic growth, both in vitro and in vivo, and could constitute a promising target for the treatment of endometriosis.

KEYWORDS:

• Vemurafenib
• PLX4032
• endometriosis
• BRAF
• MAPK

Acknowledgments

The authors would like to warmly thank staff members from our department operating room for their expert assistance with data collection. The authors thankfully acknowledge Nathalie Girma for management of the patient database. The authors also gratefully acknowledge Thomas Guilbert, of the Institute Cochin’s Imaging Facility, for his help with the ImageJ software analysis.

Declaration of interest

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.