XRCC1 immunohistochemical expression in DMBA – induced oral squamous cell carcinoma treated with different thymoquinone preparations

Abstract

The X-ray repair cross-complementing 1 (XRCC1) enzyme plays an important role in the DNA repair pathway. XRCC1 polymorphism increased the risk of human oral squamous cell carcinoma. Loading of thymoquinone on gold nanoparticles as a drug carrier, had revealed a superior anti-cancer effect as a chemotherapeutic agent in DMBA-induced OSCC. This study aimed to evaluate the expression of DNA repair enzyme X-ray repair cross-complementing 1 (XRCC1) following treatment of induced oral cancer in hamster buccal pouch with thymoquinone (TQ) only and loaded on gold nanoparticles (AuNps). Sixty male Syrian golden hamsters were divided into 4 groups: Group A: (negative control). The left pouches of the rest of animals were painted with the carcinogen DMBA (3times / week/ 12 weeks), then: Group B: (positive control), Group C: painted and injected intraperitoneally (i.p) with TQ only (3 times/week for 6 and 12 weeks). Group D: painted with TQ loaded on AuNps (3 times/week for 6 and 12 weeks). After euthanization, all pouches were surgically excised, fixed and processed for H&E and XRCC1 immunohistochemical stains. Groups B, C1, C2, and D1 showed well-differentiated squamous cell carcinoma with low intensity of immune staining. Groups D2 showed remarkable regression of tumors both clinically and histologically with high intensity of IHC staining. Loading of TQ at low concentration (0.001 mg/kg) on AuNps /12 weeks was a promising chemotherapeutic combination, through enhancing XRCC1 expression to regress the carcinogenesis process. This effect could be due to the anti-oxidant, free-radicle scavenging effect and enhancing apoptosis by TQ.