Abstract P3-06-08: JAM2 inhibits breast cancer invasion and migration by inhibiting the EMT process and potentially affects the immune microenvironment by increasing CXCL9/CXCL10
Authors: Peng Yang 
Published: March 2022

Abstract
Objectives: Large-scale epidemiological surveys have shown that patients with Down syndrome, which are caused by a chromosomal abnormality (an extra chromosome 21), are significantly less likely to develop solid tumors, including breast cancer than the normal population. This feature has prompted the search for oncogenes located on chromosome 21. Junctional Adhesion Molecule 2 (JAM2), which is located on chromosome 21, is lowly expressed in breast cancer and is associated with a good prognosis. These findings strongly suggest that JAM2 may be a potential oncogene for breast cancer. However, the role and function of JAM2 in breast cancer are not yet clear. Methods: Several databases such as CCLE, GTEx, METABRIC and TCGA were used to explore the expression of JAM2 in breast cancer and to analyze its diagnostic and prognostic value in breast cancer and to verify the stratification effect of JAM2 expression on the overall survival of breast cancer patients using Meta-analysis. Changes in relevant markers were examined at the genes and protein levels using RT-qPCR and Western blot techniques, cell migration and invasion ability by scratch assay and transwell assay, cell cycle and apoptosis by flow cytometry, and cell viability and chemotherapeutic drug sensitivity by CCK-8 assay. RNA-seq data of JAM2 overexpression were analyzed by bioinformatics methods, and we predicted drug sensitivity by machine learning algorithms, and finally the potential effect of JAM2 on the tumor microenvironment was investigated using liquid phase microarray technology. Results: JAM2 was found to be significantly downregulated in breast cancer tissues by our study, and the area under the curve (AUC) associated with JAM2 expression in Para-cancerous tissue and breast cancer tissues was analyzed by two algorithms, logistic regression and random forest algorithm, respectively, which calculated an AUC of 0.929 and 0.887 for the TCGA cohort, indicating that JAM2 has good clinical diagnostic value. Pearson's correlation analysis revealed that the expression of JAM2 and DNMT1 (r = -0.12, P &lt; 0.01), DNMT3B (r = -0.14, P &lt; 0.01) and EHMT2 (r = -0.19, P &lt; 0.01) DNA methyltransferase expression showed a significant negative correlation, and after specific inhibition of DNA methyltransferase with 5-azacytidine, there was a significant increase in JAM2 mRNA levels in the JAM2-treated group compared with the control group, suggesting that the low expression of JAM2 in breast cancer is partly regulated by DNA methylation. By analyzing the database, we found that the expression of JAM2 was significantly lower in distant recurrent tumors than in primary focal tumors. Transwell assays also showed that JAM2 overexpression significantly inhibited the migration and invasion of breast cancer cells. Vimentin and EZH2 were decreased after JAM2 overexpression, and then the level of EMT process inhibitor protein E-cadherin was increased. Through the combination of RNA-seq sequencing and machine learning algorithms, we predicted the chemotherapeutic drugs that might be sensitized after JAM2 overexpression and verified that JAM2 overexpression could sensitize breast cancer cells to Doxorubicin, and we found in the follow-up experiments that JAM2 overexpression could increase BAX and inhibit BCL-2 thereby leading to apoptosis of breast cancer cells. Then we found that JAM2 could inhibit the process of EMT by increasing the expression of ATF3 and thus inhibiting FN1 through Western blot assay. Finally, by liquid-phase microarray technology, we found more chemokines of CXCL9/CXCL10 in the cell supernatant of JAM2 overexpressing cell lines compared to the null control, thus this could be a potential mechanism for JAM2 to affect the tumor immune microenvironment.
Citation Format: Yang Peng. JAM2 inhibits breast cancer invasion and migration by inhibiting the EMT process and potentially affects the immune microenvironment by increasing CXCL9/CXCL10 [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-06-08.