Lmw-E Mediates Mammary Tumorigenesis By Deregulating Acinar Morphogenesis & Generating Cancer Stem Cells

<p>Cyclin E is the regulatory subunit of the cyclin E/CDK2 complex that</p> <p>mediates the G1-S phase transition. N-terminal cleavage of cyclin E by elastase in</p> <p>breast cancer generates two low molecular weight (LMW) isoforms that exhibit both</p> <p>enhanced kinase activity and resistance to p21 and p27 inhibition compared to fulllength cyclin E. Clinically, approximately 27% of breast cancer patients overexpress</p> <p>LMW-E and associate with poor survival. Therefore, we <strong><em>hypothesize </em></strong>that <em>LMW-E</em></p> <p><em>disrupts normal mammary acinar morphogenesis and serves as the initial route into</em></p> <p><em>breast tumor development. </em>We first demonstrate that LMW-E overexpression in</p> <p>non-tumorigenic hMECs is sufficient to induce tumor formation in athymic mice</p> <p>significantly more than overexpression of full-length cyclin E and requires CDK2-</p> <p>associated kinase activity. Further <em>in vivo </em>passaging of these tumors augments</p> <p>LMW-E expression and tumorigenic potential. When subjected to acinar</p> <p>morphogenesis <em>in vitro</em>, LMW-E mediates significant morphological disruption by</p> <p>generating hyperproliferative and multi-acinar complexes. Proteomic analysis of</p> <p>patient tissues and tumor cells with high LMW-E expression reveals that the</p> <p>activation of the b-Raf-ERK1/2-mTOR pathway in concert with high LMW-E</p> <p>expression predicts poor patient survival. Combination treatment using roscovitine</p> <p>(CDK inhibitor) plus either rapamycin (mTOR inhibitor) or sorafenib (b-raf inhibitor)</p> <p>effectively prevented aberrant acinar formation in LMW-E-expressing cells by</p> <p>inducing the G1/S cell cycle arrest. In addition, the LMW-E-expressing tumor cells</p> <p>exhibit phenotypes characteristic of the EMT and enhanced cellular invasiveness.</p> <p>These tumor cells also enrich for cells with CSC phenotypes such as increased</p> <p>CD44hi/CD24lo population, enhanced mammosphere formation, and upregulation of</p> <p>ALDH expression and enzymatic activity. Furthermore, the CD44hi/CD24lo</p> <p>population also shows positive correlation with LMW-E expression in both the tumor</p> <p>cell line model and breast cancer patient samples (p<0.0001 & p=0.0435,</p> <p>respectively). Combination treatment using doxorubicin and salinomycin</p> <p>demonstrates synergistic cytotoxic effects in cells with LMW-E expression but not in</p> <p>those with full-length cyclin E expression. Finally, ProtoArray microarray identifies</p> <p>Hbo1 as a novel substrate of the cyclin E/CDK2 complex and its overexpression</p> <p>results in enrichment for CSCs. Collectively, these data emphasize the strong</p> <p>oncogenic potential of LMW-E in mammary tumorigenesis and suggest possible</p> <p>therapeutic strategies to treat breast cancer patients with high LMW-E expression.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2012

Author dc:creator

• Duong, MyLinh T

Contributors dc:contributor

• Khandan Keyomarsi, Ph.D.
• Michelle Barton, Ph.D.
• Mong-Hong Lee, Ph.D.

• cyclin E
• breast cancer
• acinar morphogenesis
• roscovitine
• b-Raf-ERK1/2-mTOR pathway
• cancer stem cells
• epithelial-mesenchymal transition
• salinomycin
• Hbo1
• Cancer Biology
• Laboratory and Basic Science Research

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/221

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1253