Roles of the MicroRNA miR-31 in tumor metastasis and an experimental system for the unbiased discovery of genes relevant for breast cancer metastasis

In these studies, the microRNA miR-31 was identified as a potent inhibitor of breast cancer metastasis. miR-31 expression levels were inversely associated with the propensity to develop metastatic disease in human breast cancer patients. Additionally, various functional analysis revealed that miR-31 expression was both necessary and sufficient to impede breast cancer metastasis. These effects did not involve confounding influences on primary tumor development; instead, miR-31 exerted its anti-metastatic activities by impinging upon at least three distinct steps of the invasion-metastasis cascade: local invasion, one or more early post intravasation events, and metastatic colonization. At a mechanistic level, miR-31 impaired metastasis via the pleiotropic suppression of a cohort of target genes that otherwise operate to promote metastasis, including integrin a5, radixin, and RhoA. Significantly, the concomitant re-expression of integrin a5, radixin, and RhoA sufficed to override the full spectrum of miR-31'7s anti-metastatic activities. Moreover, the concurrent short hairpin RNA-conferred knockdown of endogenous integrin a5, radixin, and RhoA levels closely phenocopied the known consequences of ectopic miR-31 expression on metastasis. Integrin a5, radixin, and RhoA were found to act during at least partially unique steps of the invasion-metastasis cascade downstream of miR-31. Notably, the temporally controlled re-activation of miR-31 in already-established metastases elicited metastatic regression. These anti-metastatic therapeutic responses were attributable to the capacity of acutely re-expressed miR-31 to induce both cell cycle arrest and apoptosis; such effects arose specifically within the context of the foreign microenvironment present at a metastatic locus. When taken together, these findings provide mechanistic insights concerning the regulation of breast cancer metastasis and suggest that miR-31 may represent a clinically useful prognostic biomarker and/or therapeutic target in certain aggressive human carcinomas. In addition, a novel experimental system for the unbiased identification of metastasisrelevant genes was described. The utility of this system was demonstrated in an initial proof-of-concept screen, which implicated RhoJ as a previously unappreciated modulator of cell motility. Collectively, these observations imply that the single-cell clone-based screening methodology outlined herein may represent a generally useful means by which to enumerate novel regulators of various metastasis-relevant processes.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Valastyan, Scott J. (Scott John)

Advisor dc:contributor.advisor

• Robert A. Weinberg.

• Biology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/61791

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/61791