Open AccessDeubiquitylating enzyme, USP 9X, regulates proliferation of cells of head and neck cancer lines
Author(s) -
Nanayakkara D. M.,
Nguyen M. N.,
Wood S. A.
Publication year - 2016
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/cpr.12273
Subject(s) - cell growth , biology , cancer research , head and neck squamous cell carcinoma , hacat , wnt signaling pathway , cell culture , cancer cell , cell cycle , cell , cancer , microbiology and biotechnology , signal transduction , head and neck cancer , genetics
Objectives Truncating mutations in USP 9X have been identified in oral squamous cell carcinoma patients. The aim of this study was to determine USP 9X's functional role, if any, in head and neck cancer cells. Materials and methods USP 9X was depleted/overexpressed in head and neck cancer cell line: SCC 15 (tongue), CAL 27 (tongue), FaDu (pharynx) and Detroit 562 (pharynx). Cell proliferation was monitored using the Cy QUANT assay, and cell cycle distribution was determined by flow cytometry. Immunoblot assays were conducted to assess protein levels. RT ‐ qPCR was performed to determine Notch and Wnt pathway target gene expression. Results Our data showed a direct correlation between USP 9X protein levels and proliferation, as well as Notch pathway activity in head and neck cancer cells. However, at least in FaDu, USP 9X did not appear to regulate proliferation through the Notch pathway. Immunoblotting revealed a dramatic reduction in downstream targets of mTOR complex 1, namely total ribosomal protein (S6) and its phosphorylated form ( pS 6), when USP 9X was depleted in FaDu cells. In contrast, in immortalized but non‐tumorigenic HaCaT keratinocytes, USP 9X depletion led to increase in cell proliferation, maintaining direct regulation of Notch activity. Conclusions The functional role of USP 9X was found to be context dependent. USP 9X possibly promotes head and neck cancer cell proliferation through the mTOR pathway.