Expression of TMPRSS2/ERG oncoprotein in prostatic carcinoma

Introduction ERG is one of the oncoproteins that resulted from fusion or rearrangement of two genes, between the androgen receptor-regulated gene TMPRSS2 (21q22.3) and member of transcription factor gene, most commonly ERG (21q22.2) . ERG has some conflicts in prostatic cancer (Pca), mainly toward its expression and correlation with Gleason score and type of specimen. Aim of the work The aim of the work is to study the ERG expression in Pca and find its correlation with Gleason score and type of specimens. Materials and methods Sixty Pca specimens were collected including 34 radical prostatectomy specimens and 26 core biopsies. Specimens were stained with hematoxylin and eosin stain and re-evaluated. Immunohistochemistry was carried out using mouse anti-ERG antibody. Any degree of nuclear staining was considered positive. The percentage of positive cells were calculated and graded as follows: 1+ (weak)=less than 10%, 2+ (moderate)=11–50%, and 3+ (strong)=more than 50% tumor cells stained positive. For statistical purpose, the grading of the expression was categorized into two main categories: low, which includes negative and weak expression, and high, which includes moderate and high expression. Strongly positive vascular endothelial cells were used as an internal control. χ 2 test was used in the statistical study of the presented work. Results A nuclear ERG expression was found at an occurrence of 55%. The degree of reactivity was graded from negative (27/60, 45%), weak (13/60, 21.6%), moderate (11/60, 18.3%), to strong (9/60, 15%). No significant difference was obtained between Gleason score of less than 7 and those of more than or equal to 7, with a P value of 0.1713. Of 34 radical prostatectomy specimens, the degree of reactivity was graded from negative (12/34, 35.3%), weak (8/34, 23.5%), moderate (8/34, 23.5%), to strong (6/34, 17.6%). Of 26 core biopsy specimens, the degree of reactivity was graded from negative (15/26, 57.7%), weak (5/26, 19.2%), moderate (3/26, 11.5%), to strong (3/26, 11.5%). The significant difference was obtained in low and high grouping (low=negative and weak expression and high=moderate and strong expression) for ERG expression with Gleason score, with a P value of 0.0276. By comparison between radical prostatectomy and core biopsy specimens using low and high ERG grouping, no significant difference was found, with a P value of 0.1405. Regarding specimen type and Gleason score, no significance was obtained between both types of specimens and Gleason score, with a P value of 0.4085 and 0.4733, respectively. Conclusion The higher the Gleason score, the lower the expression of ERG . Although ERG is encountered in the pathogenesis of Pca, it is not common to be overexpressed in Pca specimens, either radical prostatectomy or core biopsies. Despite many limitations of our study such as low number of specimens, the importance of ERG in prostatic carcinoma has to be further studied in association with other parameters such as PSA level and cancer staging.