THE ROLE OF STORE-OPERATED Ca2+ ENTRY (SOCE) IN BREAST TUMOR CELL MIGRATION

Abstract

Breast cancer is the leading cause of mortality among females accounting for the highest incidence of cancers in Qatar. While the number of new cases is alarming, the majority of cancer-related death (90%) is attributed to the metastasis of the disease rather than the primary tumor. Studies so far have confirmed the role of Ca2+ entry in non-cancerous cell proliferation, as well as in the migration, proliferation, and cell adhesion of many types of cancer. Store Operated Ca2+ Entry (SOCE) is a ubiquitous Ca2+ influx pathway that is important in regulating Ca2+ homeostasis in non-excitable cells. There is some controversy in the field with paradoxical reports in the literature regarding the role of SOCE proteins in different stages and types of cancer that require further investigation. Here, we use various approaches including gene editing to assess the impact of individual SOCE proteins on cell migration and invasiveness by employing Ca2+ imaging techniques and cell migration assays. We focused our investigations on 1) Examining the impact of STIM1 phosphorylation on normal cell migration, SOCE, and ER partitioning during mitosis; and 2) Evaluating the impact of STIM1, Orai1, STIM2, and STIM1/2 knockout on cancer cell migration. In the first project, we used cells obtained from a non-phosphorylatable STIM1 mouse model (STIM1-10A) developed and characterized previously in our Lab to assess the importance of STIM1 phosphorylation on cell migration. Surprisingly, in contrast to some previous reports, we found that STIM1 phosphorylation had no significant effect on cell movement, SOCE, and ER distribution in mitosis. Consequently, in the second aim, we used a highly metastatic breast cancer cell line (MDA-MB-231), and by employing CRISPR/Cas9 technology to delete either STIM1, Orai1, STIM2, or STIM1/2 we document differential phenotypes that either accelerate or attenuate cancer cell movement. The complete loss of STIM1 resulted in faster cell migration, conversely, the deletion of Orai1, STIM2, and STIM1/2 slowed down the migration of MDA-MB-231 cells. Furthermore, our transcriptomics analysis revealed differential expression of migration-related and cell adhesion genes in the STIM1-KO line, which could underlie the faster migration in this cell line. Interestingly, the transcription factor NFAT1 RNA level and protein expression were significantly reduced in the STIM1 KO phenotype. Upon the re-expression of NFAT1 in STIM1 KO MDA-MB-231 cells, the developed phenotype was reversed enforcing the involvement of NFAT1 transcription factor on STIM1 associated rapid migration. These findings enforce new therapeutic strategies that could target STIM1 to treat or prevent breast cancer metastasis and open the door for further studies to further define the role of SOCE in breast cancer cell migration.

Date of Award	2022
Original language	American English
Awarding Institution	HBKU College of Health & Life Sciences