Curcumin Implants not Curcumin Diet Inhibits Estrogen-Induced Mammary Carcinogenesis in ACI Rats

摘要

Curcumin is widely known for its anti-oxidant, anti-inflammatory and anti-proliferative activities in cell culture studies. However, poor oral bioavailability limited its efficacy in animal and clinical studies. Recently, we developed polymeric curcumin implants that circumvents oral bioavailability issues, and tested their potential against 17β-estradiol (E2)-mediated mammary tumorigenesis. Female ACI rats were administered curcumin either via diet (1,000 ppm) or via polymeric curcumin implants (two 2-cm; 200 mg each; 20% drug load) 4 days prior to grafting a subcutaneous E2 silastic implant (1.2 cm, 9 mg E2). Implants were changed after 4½ months to provide higher curcumin dose at the appearance of palpable tumors. The animals were euthanized after 3 weeks, 3 months and after the tumor incidence reached >80% (~6 months) in control animals. The curcumin administered via implants resulted in significant reduction in both the tumor multiplicity (2±1 vs 5±3; p=0.001) and tumor volume (184±198 mm³ vs 280±141 mm^>3; p=0.0283); the dietary curcumin, however, was ineffective. Dietary curcumin increased hepatic CYP1A and CYP1B1 activities without any effect on CYP3A4 activity whereas curcumin implants increased both CYP1A and CYP3A4 activities but decreased CYP1B1 activity in presence of E2. Since CYP1A and 3A4 metabolize most of the E2 to its non-carcinogenic 2-OH metabolite and CYP1B1 produces potentially carcinogenic 4-OH metabolite, favorable modulation of these CYPs via systemically delivered curcumin could be one of the potential mechanisms. The analysis of plasma and liver by HPLC showed substantially higher curcumin levels via implants versus the dietary route despite substantially higher dose administered.