Bevacizumab induces apoptosis in the rat endometriosis model

INTRODUCTION: Endometriosis is accepted to be one of the angiogenetic diseases and neovascularization is essential for the development and survival of the endometrial tissue at the ectopic sites. Therefore, angiogenesis inhibitors are novel therapeutic agents promising a new hope for this disease. Bevacizumab is a recombinant, monoclonal antibody targeting human VEGF and it is used in various human tumors. The aim of this study was to investigate the effects of anti-VEGF antibody Bevacizumab on endometrial explants and on apoptotic gene expression levels in the rat endometriosis model.MATERIAL & METHODS: In this study surgical induction of endometriosis was performed in 29, nonpregnant, 8 weeks old Wistar Albino rats. After 3 weeks, second laparotomies were performed to measure dimensions of endometriotic foci and explant areas were calculated. The animals were divided in three groups: Group I (control group), single intraperitoneal injection of saline (0.25cc; n=10); Group II (study group), single intraperitoneal injection of bevacizumab (2.5 mg/kg; n=10); and Group III (positive control group), single subcutaneous injection of depot leuprolide acetate (1 mg/kg; n=9). Three weeks later, the rats were sacrificed and the endometriotic explant dimensions were measured, the severity and extent of the adhesions and total adhesion scores were calculated. Endometriotic foci were removed for apopotic gene expresions, histopathologic and immunohistochemical examination. The level of Bax, Cyc-c, Bcl-2 and Bcl-xl mRNA gen expressions were detected by polymerase chain reaction PCR. The presence of epithelium in explants were examined by the semiquantitative evaluation and CD10 immunohistochemistry.RESULTS: Bevacizumab treatment statistically significantly decreased the endometriotic implant size (58.8%) compared with control (6.2%) (P<0.001), and this effect was comparable with the decrease in leuprolide acetate (61.9%) (P=0.62). Bevacizumab-treated rats had lower total adhesion scores (1.4±0.9) when compared with control group (2.9±0.9) (P=0.003), but bevacizumab-treated rats had similar scores with leuprolide group (2.2±1.3) (P=0.13). Semiquantitative evaluation of the persistence of endometrial epithelial cells in the explants showed a significantly lower score in leuprolide-treated rats (0.56±1.0) compared with control rats (1.78±1.0) (P=0.009), but bevacizumab-treated rats (1.4±1.4) had similar scores with control group (P=0.45). There was no statistically significant difference in semiquantitative evaluation between bevacizumab and leuprolide group (P=0.17). In PCR study of endometriotic foci apoptotic genes (Bax, Cyc-c) and anti-apoptotic genes (Bcl-2, Bcl-xl) were evaluated. Bevacizumab statistically significantly increased expression of Bax gene 3.1 fold, Cyc-c gene 1.3 fold and decreased expression of Bcl-2 gene 0.4 fold, Bcl-xl gene 0.8 fold compared with control group (P<0.001). Similarly, leuprolide acetate statistically significantly increased expression of Bax gene 3.0 fold (P<0.001), Cyc-c gene 1.3 fold (P<0.001) and decreased expression of Bcl-2 gene 0.4 fold (P<0.001), Bcl-xl 0.8 fold (P=0.002), compared with control group. The level of change in anti-apoptotic and apoptotic gene expressions did not show statistically significant difference between bevacizumab and leuprolide group (P>0.05).CONCLUSIONS: This study suggests that a novel angiogenesis inhibitor, anti-VEGF antibody bevacizumab is as effective as leuprolide acetate in the regression of the endometriotic lesions. One possible mechanism of this effect is the induction of apoptosis.