Effect of exercise training on lymphocyte subpopulations in chemically and hormonally induced prostate cancer: flow cytometry analysis

Abstract

Introduction: Long-term and regular exercise training is suggested to have an immunomodulatory effect, protecting against several diseases. This work aimed to analyse the effect of exercise training on peripheral lymphocyte subpopulations in a model of prostate cancer (PCa) chemically and hormonally induced. Methods: Fifty-five male Wistar Unilever rats of 4 weeks of age were randomly divided into four experimental groups as follow: control sedentary group (SED+CONT; n=10), control exercised group (EX+CONT; n=10), induced sedentary group (SED+PCa; n=15) and induced exercised group (EX+PCa; n=20). Prostate lesions were induced through the sequential administration of flutamide (50 mg/kg, TCI Chemicals, USA), testosterone propionate (100 mg/kg, TCI Chemicals, Portland, USA) and N-methyl-N-nitrosourea (30 mg/kg, Sigma Chemical, Spain), and subcutaneous implantation of tubes filled with crystalline testosterone (Sigma Chemical, Spain). At eight weeks of age, exercised animals started the training in a treadmill (Treadmill Control LE 8710, USA), 5 days/weeks, for 53 weeks. Animals were sacrificed at 61 weeks of age through an intraperitoneal injection of ketamine (75 mg/kg, Imalgene® 1000, Merial S.A.S., France) and xylazine (10 mg/kg, Rompun® 2%, Bayer Healthcare S.A., Germany), followed by exsanguination by cardiac puncture. Peripheral blood of all animals was collected by intracardiac puncture and transferred into tubes containing EDTA salt as an anticoagulant for flow cytometry analysis. The following conjugated monoclonal antibodies were used: cyCD3-BV421, CD3-FITC, CD25-APC, CD45-BV510, CD127-PE, CD161-FITC, CD4-PE/Cy7, CD45RA-APC/Cy7, OX-82-PE and CD8a-PerCP. The flow cytometry immunophenotyping was performed in a BD FACSCantoTM II cytometer (BD Biosciences, USA) and data were analysed with InfinicytTM, flow cytometry software 1.7 version. The prostate was collected and stained with H&E for histopathological analysis. Statistical analysis was performed using SPSS 25. The differences were considered statistically significant at p<0.05. Results: A higher level of CD161+NK cells were observed in EX+PCa group when compared with SED+PCa group (p<0.05). These results are in accordance with the literature which suggests that exercise training increase NK cells number. Moreover, long-term exercise training increased gama delta Tcells/CD3 ratio and decreased Treg/NK ratio in PCa-induced groups (p<0.05). Dysplasia, prostatic intraepithelial neoplasia and microinvasive carcinoma were observed in dorsolateral prostate. Although the difference did not reach the level of statistical significance, the exercise training reduced the frequency of the lesions in induced groups (p>0.05). Conclusion: These results reinforce the beneficial role of exercise in anti-tumour immune response. Additional studies are warranted to better understand these results.