ERG Protein Expression in Prostatic Acinar Adenocarcinoma and Its Correlation With Clinicopathological Features

Prostatic cancer is one of the most common malignancies in males and is the second leading cause of cancer-related deaths in males worldwide. The burden is expected to grow 1.7 million new cases and 499,000 new deaths by 2030. Although the diagnosis of prostatic carcinoma can usually be made on histological features, nowadays many immunohistochemical (IHC) markers are used to distinguish it from benign mimickers as well as in predicting prognosis and treatment. Out of these markers, Ets-related gene (ERG product) is a proto-oncogene which participates in chromosomal translocations and is frequently over expressed in prostatic carcinoma which harbors ERG-transmembrane protease, serine 2 fusion. ERG is a transcription factor belonging to the erythroblast transformation-specific (ETS) family. It is involved in many important cellular processes including differentiation, cell proliferation, angiogenesis, cell migration, hematopoiesis, and apoptosis. This proto-oncogene is expressed in the urogenital tract and hematopoietic cells. Gene fusions involving sequences of transmembrane protease serine 2 (promoter of TMPRSS2) and protein coding sequences of ERG result in over expression of ERG in prostatic tumors. This TMPRSS2-ERG fusion has been shown to occur in 50-70% cases of prostatic acinar adenocarcinoma in different studies. Genetic rearrangements were not identified in epithelial carcinomas until Tomlins et al. demonstrated ERG gene fusions in prostatic carcinoma.The presence of this fusion is now believed to be a critical event in the development of prostatic carcinoma.

TMPRSS2-ERG fusion results in constitutive expression of ERG oncoprotein resulting in enhanced proliferation and invasive potential of prostatic cancer cells. Moreover, TMPRSS2-ERG fusion gene product can be an important therapeutic target in prostatic cancer. Immunohistochemical (IHC) expression of ERG oncoprotein may serve as a surrogate biomarker of TMPRSS2-ERG fusion gene. Therefore in the present study we aimed to evaluate the ERG expression in prostatic acinar adenocarcinoma and its association with clinicopathological features.