Breast cancer, one of the most common types of cancer among women, is now the second leading cause of cancer deaths after lung cancer. Since a majority of cancer deaths are due to metastasis of breast tumor cells to distant organs, understanding tumor cell invasion and metastasis at a molecular level will help us in developing therapeutics that will improve the quality of life of breast cancer patients. Cell migration, an integral component of tumor invasion and metastasis, is regulated by the assembly and disassembly of actin cytoskeleton, which involves the coordinated action of several classes of actin binding proteins. It has been shown previously that there is reduced expression of profilin 1 (Pfn1- an ubiquitously expressed actin binding protein) in invasive breast cancer cells. Pfn1 is now considered as a tumor-suppressor protein based on its ability to restrict the growth and tumorigenesis of breast cancer cells when overexpressed. Besides actin, Pfn1 also binds to several families of proline-rich ligands and these interactions have been implicated in several cellular processes including actin assembly, endocytosis and gene transcription. We have previously shown that overexpression of Pfn1 reduces the migration of BT474, a ductal carcinoma breast cancer cell line. The aim of the present work is to determine whether overexpression or selective inhibition of ligand binding of Pfn1 alter the migration and invasion of metastatic breast cancer cells. Specifically, we have studied how stable overexpression of Pfn1 and its mutant forms that are selectively impaired in binding to either actin or proline-rich ligands affect the migration and invasion of MDA-MB-231, a highly metastatic breast cancer cell line. We show that functional perturbation of Pfn1 affects the F-actin content in MDA-MB-231 cells. Specifically, Pfn1 overexpression stimulates actin polymerization, whereas expression of an actin-binding deficient mutant of Pfn1 decreases the overall level of polymerized actin in MDA-MB-231 cells. Increased focal adhesion formation in MDA-MB-231 cells as a result of Pfn1 overexpression appears to require a functional actin-binding site of Pfn1. We show that cell migration and invasion in response to chemotactic stimulus are inhibited when either fully functional or mutant forms of Pfn1 are expressed in these cells. Finally, we demonstrate that perturbation of Pfn1 affects the secretion of matrix-metalloproteinases (enzymes that are important for matrix degradation during cell invasion) by MDA-MB-231 cells.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-07182006-015907 |
| Date | 27 September 2006 |
| Creators | Panchapakesa, Vaishnavi Rajendran |
| Contributors | Dr Partha Roy, DR James Wang, Dr Alan Wells |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-07182006-015907/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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