MUC1, a transmembrane glycoprotein of the mucin family, when aberrantly expressed on breast cancer cells is correlated with increased lymph node metastases. We have previously shown that MUC1 binds intercellular adhesion molecule-1 (ICAM-1) on surrounding accessory cells and facilitates transendothelial migration of MUC1-bearing cells. Nevertheless, the underlying molecular mechanism is still obscure. In the present study, we used a novel assay of actin cytoskeletal reorganization to show that by ligating ICAM-1, MUC1 triggers Rac1-and Cdc42-dependent actin cytoskeletal protrusive activity preferentially at the heterotypic cell-cell contact sites. Further, we show that these MUC1/ICAM-1 interaction -initiated lamellipodial and filopodial protrusions require Src family kinase and CT10 regulator of kinase like (CrkL) accompanied by the rapid formation of a Src-CrkL signaling complex at the MUC1 cytoplasmic domain. Through inhibition of Src kinase activity, we further revealed that Src is required for recruiting CrkL to the MUC1 cytoplasmic domain as well as mediating the observed actin cytoskeleton dynamics. These findings suggest a novel MUC1-Src-CrkL-Rac1/Cdc42 signaling cascade following ICAM-1 ligation, through which MUC1 regulates cytoskeletal reorganization and directed cell motility during cell migration. (Mol Cancer Res 2008;6(4):555 -67)

BackgroundThe mucin MUC1, a type I transmembrane glycoprotein, is overexpressed in breast cancer and has been correlated with increased metastasis. We were the first to report binding between MUC1 and Intercellular adhesion molecule-1 (ICAM-1), which is expressed on stromal and endothelial cells throughout the migratory tract of a metastasizing breast cancer cell. Subsequently, we found that MUC1/ICAM-1 binding results in pro-migratory calcium oscillations, cytoskeletal reorganization, and simulated transendothelial migration. These events were found to involve Src kinase, a non-receptor tyrosine kinase also implicated in breast cancer initiation and progression. Here, we further investigated the mechanism of MUC1/ICAM-1 signalling, focusing on the role of MUC1 dimerization in Src recruitment and pro-metastatic signalling.MethodsTo assay MUC1 dimerization, we used a chemical crosslinker which allowed for the detection of dimers on SDS-PAGE. We then generated MUC1 constructs containing an engineered domain which allowed for manipulation of dimerization status through the addition of ligands to the engineered domain. Following manipulation of dimerization, we immunoprecipitated MUC1 to investigate recruitment of Src, or assayed for our previously observed ICAM-1 binding induced events. To investigate the nature of MUC1 dimers, we used both non-reducing SDS-PAGE and generated a mutant construct lacking cysteine residues.ResultsWe first demonstrate that the previously observed MUC1/ICAM-1signalling events are dependent on the activity of Src kinase. We then report that MUC1 forms constitutive cytoplasmic domain dimers which are necessary for Src recruitment, ICAM-1 induced calcium oscillations and simulated transendothelial migration. The dimers are not covalently linked constitutively or following ICAM-1 binding. In contrast to previously published reports, we found that membrane proximal cysteine residues were not involved in dimerization or ICAM-1 induced signalling.ConclusionsOur data implicates non-cysteine linked MUC1 dimerization in cell signalling pathways required for cancer cell migration.

The “technological singularity” is forecasted to occur in the mid-21st century and is defined as the point when machines will become smarter than humans and thus trigger the merging of humans and machines. It is hypothesized that this will have a profound influence on medicine and population health. This paper describes a new course entitled “Technology and the Future of Medicine” developed by a multi-disciplinary group of experts. The course began as a continuing medical education course and then transitioned to an accredited graduate-level course. We describe the philosophy of the course and the innovative solutions to the barriers that were encountered, with a focus on YouTube audience retention analytics. Our experience may provide a useful template for others.

No abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information 5f. WORK UNIT NUMBER Breast cancer is the second leading cause of cancer death in Canadian women. To metastasize, cells must move through the stroma of the breast, enter the circulation, survive transit, exit the circulation, and form a secondary tumor. It is not fully understood how breast cancer cells gain the ability to move or what signaling pathways mediate these events, and identification of critical components of these pathways would represent potential targets for anti-metastatic therapies. The MUC1 glycoprotein is expressed on the apical membrane of normal breast epithelia. In many human breast carcinomas, MUC1 is overexpressed and loses apical polarization, events that correlate with increased metastasis. Several critical steps of the metastatic cascade require cell adhesion, and it has been reported that MUC1 is a ligand for ICAM-1, which is expressed throughout the migratory tract of a metastasizing breast cancer cell. It was subsequently reported that MUC1/ICAM-1 binding initiates calcium oscillations, cytoskeletal reorganization, and cell migration, suggesting that binding could be important in metastasis. Here, we investigate the mechanism of MUC1/ICAM-1 binding induced signaling. We show that MUC1 forms constitutive dimers which are required for Src recruitment and ICAM-1 binding induced signaling. We show that MUC1 dimers are not covalently linked and do not require cytoplasmic domain cysteine residues. These results reveal information on the mechanism of MUC1/ICAM-1 signalling, which can be used to identify novel targets and combinational strategies for anti-metastatic therapy in breast cancer. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)UBreast cancer, metastasis, MUC1, ICAM-1, Src 43 ashlyn@ualberta.ca