Tissue expression of LC3B autophagy marker as a potential biomarker of prostate cancer recurrence after treatment with high-intensity focused ultrasound (pilot study)

Abstract

Background. The role of autophagy markers in prostate tumor recurrence has not been sufficiently investigated. We hypothesized that autophagy activation may be one mechanism by which prostate cancer cells survive exposure to high-intensity focused ultrasound (HIFU).Aim. To compare tissue expression of autophagic LC3B marker in prostate biopsies before and after treatment of localized prostate cancer by HIFU ablation.Materials and methods. 45 patients with localized morphologically confirmed prostate cancer were examined: group 1 – 25 patients of 65.6 ± 8.4 years without signs of recurrence or progression of the disease; group 2 – 20 patients of 67.5 ± 7.9 years with tumor recurrence proven during morphological examination. Immunohistochemical examination was performed by streptavidin-biotin method. In all cases, Anti-LC3B antibody ab48394 was used. The reaction results were quantified using the Histochemical score (Hs) system.Results. Prior to treatment, all patients of group 1 showed moderate cytoplasmic expression (Hs = 111 [111; 115]) of antibodies against LC3B in prostate adenocarcinoma cells, 5 % of patients – weak cytoplasmic expression in muscle connective stromal cells (Hs = 47 [43; 50]), 10 % of patients – weak positive LC3B reaction in the vessel wall (Hs = 28 [20; 35]). After treatment, the expression of LC3B in adenocarcinoma cells became negative, in the cytoplasm of muscle connective stromal cells weak (Hs = 75 [67.5; 80.0]), in the endothelium of the vascular wall even weaker (Hs = 55 [45.5; 60.0]) (p <0.001). Prior to treatment in group 2, LC3B expression in tumor tissue was moderate in 89 % of patients (Hs = 151.5 [137.5; 160.0]), weak in muscle connective stromal cells in 12 % of patients (Hs = 44 [35; 51.5]), and weak in the vascular wall in 5 % of patients (Hs = 30 [25; 35]). After treatment, LC3B expression in adenocarcinoma cells became pronounced (Hs = 260 [250; 285]), in muscle connective stromal cells – moderate (Hs = 118 [100; 130]), in the vascular wall – weak (Hs = 45 [30; 55]) (p <0.001). There was a significant correlation between tumor recurrence and LC3B overexpression (r = 0.51; p <0.001).Conclusion. The development of prostate cancer recurrence is associated with increased expression of autophagic LC3B protein. Increased LC3B expression, which is interpreted as evidence of autophagy activation and correlates with the risk of disease progression, is used by the tumor as an oncogenic advantage.