Inhibition of Akt enhances the chemopreventive effects of topical rapamycin in mouse skin

Cancer Prevention Research
By: , and 

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Abstract

The PI3Kinase/Akt/mTOR pathway has important roles in cancer development for multiple tumor types, including UV-induced non-melanoma skin cancer. Immunosuppressed populations are at increased risk of aggressive cutaneous squamous cell carcinoma (SCC). Individuals who are treated with rapamycin, (sirolimus, a classical mTOR inhibitor) have significantly decreased rates of developing new cutaneous SCCs compared to those that receive traditional immunosuppression. However, systemic rapamycin use can lead to significant adverse events. Here we explored the use of topical rapamycin as a chemopreventive agent in the context of solar simulated light (SSL)-induced skin carcinogenesis. In SKH-1 mice, topical rapamycin treatment decreased tumor yields when applied after completion of 15 weeks of SSL exposure compared to controls. However, applying rapamycin during SSL exposure for 15 weeks, and continuing for 10 weeks after UV treatment, increased tumor yields. We also examined whether a combinatorial approach might result in more significant tumor suppression by rapamycin. We validated that rapamycin causes increased Akt (S473) phosphorylation in the epidermis after SSL, and show for the first time that this dysregulation can be inhibited in vivo by a selective PDK1/Akt inhibitor, PHT-427. Combining rapamycin with PHT-427 on tumor prone skin additively caused a significant reduction of tumor multiplicity compared to vehicle controls. Our findings indicate that patients taking rapamycin should avoid sun exposure, and that combining topical mTOR inhibitors and Akt inhibitors may be a viable chemoprevention option for individuals at high risk for cutaneous SCC.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Inhibition of Akt enhances the chemopreventive effects of topical rapamycin in mouse skin
Series title Cancer Prevention Research
DOI 10.1158/1940-6207.CAPR-15-0419
Volume 9
Year Published 2016
Language English
Publisher American Association for Cancer Research
Contributing office(s) Arizona Water Science Center
Description 10 p.
First page 215
Last page 224
Online Only (Y/N) N
Additional Online Files (Y/N) N