Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide and is associated with high morbidity and mortality. Increased activation of Signal Transducer and Activator of Transcription-3 (STAT3) has been implicated in OSCC tumorigenesis and progression. The mechanisms of STAT3 hyperactivation in OSCC are incompletely understood. Preliminary data suggests that the receptor-like protein tyrosine phosphatase T (PTPRT) directly dephosphorylates, and thus inactivates, STAT3 in OSCC preclinical models. Recent reports from our group and The Cancer Genome Atlas (TCGA) have demonstrated promoter methylation or mutation of PTPRT in a relatively high proportion of OSCC tumors (60% and 5.5%, respectively of 347 tumors analyzed to date). Further investigation showed that expression of OSCC-derived PTPRT mutants leads to increased STAT3 activation in OSCC cells. We therefore hypothesize that loss-of-function (LOF) of PTPRT by mutation or promoter methylation contributes to STAT3-mediated growth and survival pathways in OSCC. We therefore predict that OSCC tumors harboring LOF alterations of PTPRT will exhibit increased sensitivity to STAT3 pathway inhibition, ultimately allowing the identification of a subgroup of patients who are most likely to respond to STAT3 pathway inhibitors. We will investigate the above hypotheses via the following specific aims:
Specific Aim 1 : To determine the effect of OSCC tumor-derived PTPRT mutations on phosphatase activity and the contribution of PTPRT mutations to growth, survival, and sensitivity to STAT3 pathway inhibition in OSCC preclinical models.
Specific Aim 2 : To investigate PTPRT promoter methylation in OSCC human tumors and cell lines and determine the contribution of PTPRT loss to OSCC tumorigenesis, progression, and sensitivity to STAT3 pathway inhibition in vivo using a PTPRT KO mouse model.

Public Health Relevance

Oral squamous cell carcinoma (OSCC) is an invasive malignancy with more than 40,000 cases diagnosed annually in the United States. We have identified loss of function genetic and epigenetic alterations of a protein tyrosine phosphatase receptor (PTPRT) in OSCC leading to increased STAT3 signaling and identifying a subset of patients that are most likely to respond to STAT3 pathway inhibition. We propose here to determine the contribution of PTPRT mutation and methylation to OSCC development, progression and STAT3 activation with the goal of improving therapy for OSCC patients.

National Institute of Health (NIH)
Predoctoral Individual National Research Service Award (F31)
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NIDR Special Grants Review Committee (DSR)
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Frieden, Leslie A
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University of Pittsburgh
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Peyser, N D; Freilino, M; Wang, L et al. (2016) Frequent promoter hypermethylation of PTPRT increases STAT3 activation and sensitivity to STAT3 inhibition in head and neck cancer. Oncogene 35:1163-9
Peyser, Noah D; Wang, Lin; Zeng, Yan et al. (2016) STAT3 as a Chemoprevention Target in Carcinogen-Induced Head and Neck Squamous Cell Carcinoma. Cancer Prev Res (Phila) 9:657-63
Peyser, Noah D; Du, Yu; Li, Hua et al. (2015) Loss-of-Function PTPRD Mutations Lead to Increased STAT3 Activation and Sensitivity to STAT3 Inhibition in Head and Neck Cancer. PLoS One 10:e0135750
Lui, Vivian Wai Yan; Peyser, Noah D; Ng, Patrick Kwok-Shing et al. (2014) Frequent mutation of receptor protein tyrosine phosphatases provides a mechanism for STAT3 hyperactivation in head and neck cancer. Proc Natl Acad Sci U S A 111:1114-9
Peyser, Noah D; Grandis, Jennifer R (2014) Genetic mutations in head and neck cancer: utilizing existing treatments. Pharmacogenomics 15:1553-5