Pleomorphic adenoma gene 1 (PLAG1) protects p53-/- myoepithelial cells from mitochondria-related apoptosis caused by hypoxia

Abstract

Objective

Pleomorphic adenoma (PA) is one of the most frequent benign tumors of the salivary glands. Although pleomorphic adenoma gene 1 (PLAG1) is considered to be responsible for the oncogenesis of a PA, its role in myoepithelial cells remains poorly understood. This study investigated the intrinsic involvement of PLAG1 in the apoptosis pathway at hypoxia in the absence of p53.

Methods

Mouse myoepithelial (ME) cells were derived from p53^-/- mice. The cells were grown in serum-free medium in an atmosphere of 5 % CO₂ and 100 % humidity. Hypoxic conditions were set at 37°C, 2 % O₂, and 5 % CO₂. Cell viability and cell proliferation were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell cycle assay, respectively. Apoptosis was assessed by caspase-3/7 and mitochondrial membrane potential (MMP) assays and western blotting for apoptosis-related proteins. In gene knockdown experiments, small interference RNAs (siRNA) were transfected into cells using the lipofection method.

Results

PLAG1 is regulated downstream of HIF-1α and shows potential to inhibit and/or resist apoptosis via the modulation of the Bcl-2 pathway under hypoxic conditions, which is often observed at the center of PAs.

Conclusions

Exposure to hypoxia in myoepithelial cells increases PLAG1 expression, whereby Bcl-2-relataed pathway and MMP is activated.