Clinical significance of androgen receptor variant-7 (AR-V7) in prostate cancer

Aim: Prostate cancer is the most common cancer in males in the United States, except skin cancer. Approximately 238,590 people were diagnosed with prostate cancer in 2013 and this number constitutes approximately 28% of all newly diagnosed cases of cancer (1). There are various agents used in the treatment of prostate cancer. Various resistance mechanisms against agents used in the treatment of prostate cancer were mentioned in the literature. The aim of this study is to determine the clinical and prognostic significance of androgen receptor variant 7(AR-V7), which is one variant of the androgen receptors, in prostate cancer. Materials and Methods: Forty five cases diagnosed with metastatic prostate adenocarcinoma in Çukurova University Faculty of Medicine, Oncology polyclinic between the years 2004-2015 were selected, and biopsy paraffin tissue blocks of the patients were presented. Number of cases with prostate biopsy paraffin block was thirty eight, number of cases with paraffin block of organ in which metastasis occurred was forty two, and number of cases with both prostate biopsy paraffin block and paraffin block of organ in which metastasis occurred was thirty five. AR-V7 was studied from the paraffin blocks of patients with RT-PCR method. Laboratory, demographic and clinical results of the patients were compared. SPSS 22.0 software package was used in statistical analysis. Results: The average diagnosis age of the patients was 64.2 ± 8.89 (45-87). Average PSA of the patients at diagnosis was 160±356 (1.04 - 2021) ng/ml. 12 of the patients (26.7%) had bone marrow metastasis, 12 of the patients (26.7%) had regional lymph node metastasis, 10 of the patients (22.2%) had bone metastasis, 5 of the patients (11.1%) had distant lymph node metastasis, 2 of the patients (4.4%) had lung metastasis, 2 of the patients (4.4%) had bladder metastasis, 1 of the patients (2.2%) had peritoneum metastasis and 1 of the patients (2.2%) had testicular metastasis. While 15 of 38 patients with prostate paraffin tissue blocks (39.5%) were detected as AR-V7 positive, 21 of 42 patients with metastasis paraffin tissue blocks (50%) were detected as AR-V7 positive. While AR-V7 negative variant was detected in prostate tissue blocks of 3 patients (8.6%), AR-V7 variant in metastatic tissue paraffin blocks was detected as positive. It was observed that there was compatibility between prostate tissue AR-V7 status and metastatic tissue AR-V7 status (PMcNemar =0.250). 3rd and 6th month PSA average control of AR-V7 positive patients was higher than AR-V7 negative patients; this difference between 6th month control PSAs was statistically significant in patients with prostate tissue paraffin blocks (p=0.035). PSA values were higher in AR-V7 positive patients treated with abiraterone, but it was not statistically significant (p>0.05). Median overall survival in AR-V7 positive group was shorter compared to AR-V7 negative group, but the difference was not statistically significant (p>0.05). Median overall survival in AR-V7 positive group treated with abiraterone was about 10 months shorter than AR-V7 negative group. Conclusion: It is thought that AR-V7 plays a role in resistance to the treatment in prostate cancer patients. AR-V7 status can be viewed in terms of response to treatment especially in patients who will be started to abiraterone treatment. However, these results must be confirmed by studies conducted in more patients. Keywords: AR-V7, Prostate cancer