Abstract A26: Levels of phospho-Connexin 43 and phospho-TRKB in epithelial ovarian cancer.
Authors: Garrido Maritza P. , Selman Alberto , Gabler Fernando , Vega Margarita , Romero Carmen 
Published: May 2016

Cancer is the second cause of death in Chile, and one of the most aggressive and worse prognosis is ovarian cancer. Between 70 and 80% of ovarian cancer cases correspond to epithelial ovarian cancer (EOC).

EOC has a poor treatment response, so that is necessary to study new targets in order to improve cancer therapy. In this context, the neurotrophin receptors (for instance TRK receptors) and cell adhesion and communication molecules such as connexins are very important.

Researches undertaken by our group have found that Nerve Growth Factor and its high affinity receptor TRKA are involved in cell proliferation and angiogenesis in EOC. TRKB, another subtype of TRK receptor, by interacting with its high affinity ligand brain-derived neurotrophic factor or NGF has been strongly associated with metastatic processes and resistance to cancer therapies in many kinds of cancers. Specially, phosphorylation of TRKB on residue tyrosine 812 (pTRKB) is capable of activating FLCy-PKC pathway, which has an important role on proliferation, apoptosis and protein modifications, like connexins.

On the other hand, cells are anchored and connected into tissues through gap junctions, among others. These are channels that connect cytoplasmic contents of neighbor cells and also regulate many physiological processes such as cell cycle, permeability and migration. Connexins are proteins that form these channels. Connexin 43 (Cx43) has been widely studied in cell lines and tissues from cancer, being present in ovarian cancer. Phosphorylation of Cx43 on serine 368 (pCx43) disrupts gap junctions and intercellular junctional communication. This could be an advantage for malignant cells to survive in processes such as therapy resistance, proliferation and metastasis. This phosphorylation is induced by several tyrosine kinase receptors, for instance platelet-derived growth factor receptor.

The main purpose of this study is to describe the presence and levels of pTRKB and pCx43 on women´s ovary samples and to associate them with patients´ survival through a retrospective study.

Samples of female patients (age 26 -79, average 52 years) who underwent surgical procedures at University of Chile Clinical Hospital were used. Each participant signed an informed consent approved by the institutional ethics committee. Fresh tissue stored at -80°C and paraffin-fixed tissues were employed, jointly with retrospectively analysis of medical records. Biopsy and classification of samples were performed in the Pathology Department of the same Hospital, and the samples were classified in inactive or normal ovaries (N=17), ovarian tumor (N=18) and epithelial ovarian cancer (N=33). pCx43 and pTRKB levels were determined by immunohistochemistry (IHQ) and levels of Cx43 and pCx43 were measured by Western-blot. The semi-quantitative analysis was performed by ImageProPlus 6.0.250 and UnScan-It gel 6.1. These results were associated with patients' survival. Kruskal Wallis and Mann Whitney tests were performed.

The results showed that pTRKB and pCx43 were found in epithelial cells of ovarian tissues which levels increased during the progression of EOC; in fact, pTRKB content was evaluated by IHQ being 1.7 times in tumors and 3,2 times in EOC (p&lt;0.05) compared to normal ovarian epithelium respectively. Levels of pCx43 were 3,6 times in tumor and 6,0 times in EOC respect to ovarian normal epithelium (p&lt;0.01). The pCx43/Cx43 ratio evaluated by western-blot, increased from 0,37 to 0,83 (2,3 times, p&lt;0,05) between inactive ovary and EOC.

These results suggest that the studied molecules play a role in the progression of EOC and should be considered as potential targets to be evaluated in future research.

Grants: FONDECYT 1110372, CONICYT-FONDAP 15130011 and OAIC University of Chile Clinical Hospital project 603/13

Citation Format: Maritza P. Garrido, Alberto Selman, Fernando Gabler, Margarita Vega, Carmen Romero. Levels of phospho-Connexin 43 and phospho-TRKB in epithelial ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A26.