Doctor of Philosophy (PhD)
First Advisor's Name
First Advisor's Committee Title
Second Advisor's Name
Second Advisor's Committee Title
Third Advisor's Name
Third Advisor's Committee Title
Fourth Advisor's Name
Fourth Advisor's Committee Title
Fifth Advisor's Name
Fifth Advisor's Committee Title
Melanoma, Tumor Microenvironment, Endothelin, Regulatory T cell
Date of Defense
Endothelins are cytokines ubiquitously expressed in the microenvironment of several tumors. In melanoma is not clear whether stromal cells respond to the endothelin present in the microenvironment. To address this question, I generated tumors derived from different murine melanoma cell lines (B16F10, YUMM1.7, YUMMER1.7) in a transgenic mouse that overexpresses endothelin 3 (Edn3) by keratinocytes in the skin (K5-Edn3). Tumors from all the cell lines grew larger and were more aggressive when Edn3 was overexpressed in the skin. In tumors derived from YUMM1.7-GFP cells, very few tumorigenic cells expressed the Edn3 receptor, Endothelin receptor b (Ednrb) suggesting an environmental role for endothelin signaling in melanoma microenvironment. The present study showed for the first time that Ednrb is expressed in several cell populations inside melanoma microenvironment. The clinical relevance of the finding was validated using publicly available RNA-seq data from melanoma patients. Regulatory T cells (Tregs) was the only population that was numerically different when K5-Edn3 tumors were compared to wild-type tumors suggesting that Edn3 promotes Treg enrichment in melanoma microenvironment. The present study supports the notion that endothelin promotes the formation of an immunosuppressive milieu in melanoma facilitating escape from tumor immunity. Endothelin was required for immune escape of highly immunogenic melanoma cells YUMMER1.7. The immunosuppressive features of Tregs were enhanced in presence of Edn3. The master regulator of Tregs’ suppressive functions, FOXP3, was remarkably upregulated in K5-Edn3 tumors as well as immunosuppressive cytokines TGF-β and IL-10. Overexpression of Edn3 in the tumor microenvironment prevented the expansion of CTLs possibly via GZB-mediated cytolysis. Expression of chemokines and inflammatory cytokines were downregulated in K5-Edn3 tumors. Cytokines that elicit anti-tumor immunity, exhibited reduced levels in K5-Edn3 tumors. The YUMM1.7-GFP tumors exposed to high levels of Edn3 were sensitive to immune checkpoint inhibitor (anti-CTLA-4) as well as to Ednrb blockage (BQ-788). The response to BQ-788 was more pronounced suggesting that EDNRB targeting might be an alternative therapeutic strategy for melanoma patients that are under immunotherapy regimen. In conclusion, the present study indicates that Edn3/Ednrb signaling has an important role in the melanoma microenvironment where it mediates immunosuppression resulting in escape from tumor immunity.
Tiburcio de Freitas, Juliano, "The Immunosuppressive Role of Edn3/Ednrb Signaling in the Melanoma Microenvironment" (2019). FIU Electronic Theses and Dissertations. 4029.
In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).