Reference Detail

Ref Type

Journal Article

PMID

(25724523)

Authors

Leiker AJ, DeGraff W, Choudhuri R, Sowers AL, Thetford A, Cook JA, Van Waes C, Mitchell JB

Title

Radiation Enhancement of Head and Neck Squamous Cell Carcinoma by the Dual PI3K/mTOR Inhibitor PF-05212384.

Journal	Vol	Issue	Date	Pages	Journal Short Title
Clinical cancer research : an official journal of the American Association for Cancer Research	21	12	2015 Jun 15	2792-801	Clin Cancer Res

URL

Abstract Text

Radiation remains a mainstay for the treatment of nonmetastatic head and neck squamous cell carcinoma (HNSCC), a malignancy characterized by a high rate of PI3K/mTOR signaling axis activation. We investigated the ATP-competitive dual PI3K/mTOR inhibitor, PF-05212384, as a radiosensitizer in preclinical HNSCC models.Extent of radiation enhancement of two HNSCC cell lines (UMSCC1-wtP53 and UMSCC46-mtP53) and normal human fibroblast (1522) was assessed by in vitro clonogenic assay with appropriate target inhibition verified by immunoblotting. Radiation-induced DNA damage repair was evaluated by γH2AX Western blots with the mechanism of DNA double-strand break repair abrogation investigated by cell cycle analysis, immunoblotting, and RT-PCR. PF-05212384 efficacy in vivo was assessed by UMSCC1 xenograft tumor regrowth delay, xenograft lysate immunoblotting, and tissue section immunohistochemistry.PF-05212384 effectively inhibited PI3K and mTOR, resulting in significant radiosensitization of exponentially growing and plateau-phase cells with 24-hour treatment following irradiation, and variable radiation enhancement with 24-hour treatment before irradiation. Tumor cells radiosensitized to a greater extent than normal human fibroblasts. Postirradiation PF-05212384 treatment delays γH2AX foci resolution. PF-05212384 24-hour exposure resulted in an evident G1-S phase block in p53-competent cells. Fractionated radiation plus i.v. PF-05212384 synergistically delayed nude mice bearing UMSCC1 xenograft regrowth, with potential drug efficacy biomarkers identified, including pS6, pAkt, p4EBP1, and Ki67.Taken together, our results of significant radiosensitization both in vitro and in vivo validate the PI3K/mTOR axis as a radiation modification target and PF-05212384 as a potential clinical radiation modifier of nonmetastatic HNSCC.

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Molecular Profile	Treatment Approach

Gene Name	Source	Synonyms	Protein Domains	Gene Description	Gene Role

Therapy Name	Drugs	Efficacy Evidence	Clinical Trials

Drug Name	Trade Name	Synonyms	Drug Classes	Drug Description

Gene	Variant	Impact	Protein Effect	Variant Description	Associated with drug Resistance

Molecular Profile	Indication/Tumor Type	Response Type	Therapy Name	Approval Status	Evidence Type	Efficacy Evidence	References