Abstract P6-08-11: The Potential Role of Junctional Adhesion Molecule (JAM)-2 in Breast Cancer Cells and the Expression of JAM2 in Ductal Mammary Carcinoma
Authors: Al-Mrabt N , Martin TA , Mansel RE , Jiang WG. 
Published: April 2011

Background. JAM-2, Junctional Adhesion Molecule-2, is a member of the JAM family that has been found in epithelial and endothelial cells. It was found to be co-localised in the tight junctions of conjoining epithelial cells and, via homotypic interactions, may influence the function of tight junctions. Although the molecule has been indicated in the resting of tumour cells in the circulation, its role in solid tumours is not clear. In the present study, we investigated the cellular impact of JAM-2 on breast cancer cells and a possible clinical link with the aggressiveness of breast cancer.

Materials and methods. Two human breast cancer cell lines, MDA MB-231 and MCF-7 were used. Expression construct for full length human JAM-2 were generated and used for over-expression of JAM2 in breast cancer cells. Anti-JAM2 transgenes were designed, cloned and used in the cells in order to create JAM2 knockdown sublines. The tight junction function was assessed using a trans-epithelial resistance assay (TER, with an EVOM voltammeter). Matrix adhesion and cell migration were assessed using an ECIS (electric cell-substrate impedance sensing) assay. The expression of JAM2, at transcript and protein levels, was determined in a cohort of ducal carcinoma of the breast and was correlated with the pathological grade and clinical outcome.

Results. MDA MB-231 cell, negative in JAM-2 in wild type, was transfected to over-express JAM2 (MDA231JAM2exp). Expression of JAM-2 in MCF-7, positive in JAM2 expression, was knocked down by way of transgene (MCF7ÄJAM2). Over-expression of JAM2 resulted in a significant increase in TER (654±18.5Ω in MDA231JAM2exp, p=0.008 vs 617±14.5Ω in control cells). In the adhesion assay, neither MDA MB 231 nor MCF-7 showed a significant change in their adhesiveness after JAM2 expression manipulation. Interestingly, knocking down JAM2 in MCF7MAM2 cells resulted in an increase in cell migration using the ECIS assay. The opposite was seen with MDA231JAM2exp cells in which over-expression of JAM-2 resulted in a reduced cell migration. In a cohort of ductal carcinoma (n=80), JAM-2 transcript (normalised to CK19) was found to be significantly reduced in high grade tumours (median(IQ) 3.7 (0.21-26.8) in grade-1 vs 0.01 (0-0.46) grade-2, p=0.0039 by Mann-Whitney U test). Although there was no significant correlation between JAM-2 and the mortality, tumours from patients who developed metastasis had a significantly lower levels of JAM-2 than those who were disease free (0.10 (0.01-3.79) vs 0.54 (0-4.46), p=0.021, respectively).

Discussion. The present study shows that the Junctional Adhesion Molecule-2 has a significant impact on the functions of breast cancer cells, including the transepithelial resistance and the cellular migration of the cells. The study has also shown that reduction of JAM2 expression is associated with tumour grade and, to a degree, the clinical outcome in breast cancer. It is concluded that JAM-2 has a pivotal role to play in regulating the aggressiveness of breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-08-11.