Platelets and Anti-Angiogenic Resistance In Ovarian Carcinoma

<p>Background: Resistance to targeted anti-angiogenic therapy is a growing clinical concern given the disappointing clinical impact of anti-angiogenic. Platelets represent a component of the tumor microenvironment that are implicated in metastasis and represent a significant reservoir of angiogenic regulators. Thrombocytosis has been shown to be caused by malignancy and associated with adverse clinical outcomes, however the causal connections between these associations remain to be identified.</p> <p>Materials and Methods: Following IRB approval, patient data were collected on patients from four U.S. centers and platelet levels through and after therapy were considered as indicators of recurrence of disease. <em>In vitro</em> effects of platelets on cancer cell proliferation, apoptosis, and migration were examined. RNA interference was used to query signaling pathways mediating these effects. The necessity of platelet activation for <em>in vitro</em> effect was analyzed. <em>In vivo</em> orthotopic models were used to query the impact of thrombocytosis and thrombocytopenia on the efficacy of cytotoxic chemotherapy, the effect of aspirin on thrombocytosis and cancer, and platelet effect on anti-angiogenic therapy.</p> <p>Results: Platelets were found to increase at the time of diagnosis of ovarian cancer recurrence in a pattern comparable to CA-125. Platelet co-culture increased proliferation, increased migration, and decreased apoptosis in all cell lines tested. RNA interference implicated platelet derived growth factor alpha (PDGFRA) and transforming growth factor beta-receptor 1 (TGFBR1) signaling. Biodistribution studies suggested minimal platelet sequestration of taxanes. Blockade of platelet activation blocked <em>in vitro</em> effects. <em>In vivo</em>, thrombocytosis blocked chemotherapeutic efficacy, thrombocytopenia increased chemotherapeutic efficacy, and aspirin therapy partially blocked the effects of thrombocytosis. In vivo, withdrawal of anti-angiogenic therapy caused loss of therapeutic benefit with evidence of accelerated disease growth. This effect was blocked by use of a small-molecule inhibitor of Focal Adhesion Kinase. Anti-angiogenic therapy was also associated with increased platelet infiltration into tumor that was not seen to the same degree in the control or FAK-inhibitor-treated mice.</p> <p>Conclusions: Platelets are active participants in the growth and metastasis of tumor, both directly and via facilitation of angiogenesis. Blocking platelets, blocking platelet activation, and blocking platelet trafficking into tumor are novel therapeutic avenues supported by this data.</p> <p><em>Copyright © 2012 Justin Neal Bottsford-Miller, all rights reserved.</em></p>

Name thesis:degree_name

Masters of Science (MS)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2012

Author dc:creator

• Bottsford-MIller, Justin N

Contributors dc:contributor

• Anil Sood, M.D.
• Vahid Afshar-Kharghan, M.D.
• Gary Gallick, Ph.D.

• Platelets
• Cancer
• Angiogenesis
• Biology
• Cancer Biology
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/247

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1299