Micro RNAs are small non-coding RNAs, which regulate fundamental cellular and developmental processes at the transcriptional and translational level. In breast cancer, miR-145 expression is downregulated compared with healthy control tissue. As several predicted targets of miR-145 potentially regulate cell motility, we aimed at investigating a potential role for miR-145 in breast cancer cell motility and invasiveness. Assisted by Affymetrix array technology, we demonstrate that overexpression of miR-145 in MDA-MB-231, MCF-7, MDA-MB-468 and SK-BR-3 breast cancer cells and in Ishikawa endometrial carcinoma cells leads to a downregulation of the cell-cell adhesion protein JAM-A and of the actin bundling protein fascin. Moreover, podocalyxin and Serpin E1 mRNA levels were downregulated, and gamma-actin, transgelin and MYL9 were upregulated upon miR-145 overexpression. These miR-145-dependent expression changes drastically decreased cancer cell motility, as revealed by time-lapse video microscopy, scratch wound closure assays and matrigel invasion assays. Immunofluorescence microscopy demonstrated restructuring of the actin cytoskeleton and a change in cell morphology by miR-145 overexpression, resulting in a more cortical actin distribution, and reduced actin stress fiber and filopodia formation. Nuclear rotation was observed in 10% of the pre-miR-145 transfected MDA-MB-231 cells, accompanied by a reduction of perinuclear actin. Luciferase activation assays confirmed direct miR-145-dependent regulation of the 3 0 UTR of JAM-A, whereas siRNA-mediated knockdown of JAM-A expression resulted in decreased motility and invasiveness of MDA-MB-231 and MCF-7 breast cancer cells. Our data identify JAM-A and fascin as novel targets of miR-145, firmly establishing a role for miR-145 in modulating breast cancer cell motility. Our data provide a rationale for future miR-145-targeted approaches of antimetastatic cancer therapy.

The PAR-3–aPKC–PAR-6 complex is recruited to primordial cell–cell junctions, in which aPKC phosphorylates JAM-A to promote junctional maturation.

This paper describes a ternary protein complex consisting of junctional adhesion molecule-A (JAM-A), tetraspanin CD9, and αvβ3 integrin in endothelial cells. In this complex, CD9 links JAM-A to αvβ3 integrin to regulate basic fibroblast growth factor–specific mitogen-activated protein kinase activation, endothelial cell migration, and tube formation. Our findings contribute to a better understanding of the signaling events during angiogenesis.

Contact inhibition of locomotion (CIL) is a process that regulates cell motility upon collision with other cells. Improper regulation of CIL has been implicated in cancer cell dissemination. Here, we identify the cell adhesion molecule JAM-A as a central regulator of CIL in tumor cells. JAM-A is part of a multimolecular signaling complex in which tetraspanins CD9 and CD81 link JAM-A to αvβ5 integrin. JAM-A binds Csk and inhibits the activity of αvβ5 integrin-associated Src. Loss of JAM-A results in increased activities of downstream effectors of Src, including Erk1/2, Abi1, and paxillin, as well as increased activity of Rac1 at cell–cell contact sites. As a consequence, JAM-A-depleted cells show increased motility, have a higher cell–matrix turnover, and fail to halt migration when colliding with other cells. We also find that proper regulation of CIL depends on αvβ5 integrin engagement. Our findings identify a molecular mechanism that regulates CIL in tumor cells and have implications on tumor cell dissemination.

No abstract

Approximately 90% of ovarian cancer (OC) is Epithelial ovarian Cancer (EOC) subtype and claims ~15,000 lives in the United States annually, making it the deadliest reproductive cancer in women. There are few treatment options for EOC, amongst them include surgical resection of tumors or debulking, and chemotherapy alone or combination. In general, the survival rate of patients with EOC is about 48% and this has not changed in last few decades. According to recent reports from American Cancer Society and SEER, racial disparity in ovarian cancer not only exists for African American (AA) patients, but is worsening over the past few years. African American (AA) patients presents with more advanced disease and develop chemoresistance frequently, and as such, they experience worse survival. Thus identifying the cause of this discrepancy, or more importantly, describing which AA patients are at the highest risk of therapeutic relapse would alter our current treatment strategies and improve overall disease free survival rate. Therefore, the central focus of this proposal is to delineate the molecular and genetic mechanisms contributing to racial disparity of AA patients. Therefore, the overall objective of our studies are to identify the etiology of racial disparity in ovarian cancer and define the molecular networks that contribute this discrepancy in outcomes. Lymphoblastic Leukemia-Derived Sequence 1 (LYL1) is a polypeptide that harbors basic helix-loop-helix transcription factor, a DNA binding motif and dysregulated in many cancers including EOC. Analysis of TCGA data for EOC revealed that LYL1 gene amplification in about 12% patients and associated with poor prognosis. Interestingly, further analysis of LYL1 copy number alteration in different ethnicities disclosed LYL1 amplification in about 36% of the African American (AA) EOC patients. Importantly, EOC patients with low LYL1 (n=1640) expression has better survival probability compared to patients with overexpressed LYL1 (n=202). This discrepancy in survival probability is much more prominent in AA EOC patients. As this is an intriguing observation, we evaluated the levels of LYL1 expression in different EOC cell lines in comparison with fallopian tube epithelial cells. Our data shows, upregulation of LYL1 in most of the EOC cell lines compared to normal fallopian tube epithelial cells. To examine the upregulated LYL1 in EOC cell lines, we performed siRNA mediated downregulation, and evaluated their clonogenic, migration invasion potential. Consistent with the TCGA data, knocking down LYL1 in EOC cells significantly attenuated their clongenic, migration and invasion potential. Furthermore, ectopic overexpression of LYL1 in EOC cells that shows deep deletion of the gene, exhibited increased clonogenicity, invasion and migration. Collectively, our studies indicate an important role for LYL1 in EOC tumor progression and metastatic phenotypes, and could be a biomarker for disparities in EOC outcomes. Citation Format: Damieanus Ochola, Shirisha Jonnalagadda, Swetha Peddibhotla, Tasmin Omy, Mark Reedy, Palle Komaraiah. Upregulated LYL1 promotes epithelial ovarian cancer (EOC) cell growth and metastasis [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-132.