Topical tacrolimus potentiates carcinogenesis in mouse skin and reduces the lymph node CD4/CD8 ratio

Y Niwa MD PhD^a, T Terashima MD^b, H Sumi MD^c

^aNiwa Institute for Immunology, Tosashimizu, Kochi, Japan, ^bDepartment of Dermatology, Osaka City University Medical School, Osaka, Japan, ^cDepartment of Internal Medicine, National Cancer Center Hospital East, Kashiwa, Japan

AIM: Tacrolimus (FK506) is a potent macrolide immunosuppressant, widely used for preventing graft rejection in organ transplantation. Recently, topical FK506 has been used to treat atopic dermatitis because of its immunosuppressive effect on not only CD4 T cell but also on Th1, 2 T cells which are closely correlated to the pathogenesis of atopic dermatitis. However, since 7% of patients undergoing systemic administration of FK506 for liver transplantation subsequently developed malignancy (Transplantation, 66, 1193, 1998), we investigated the carcinogenic effect of topical FK506. METHODS: We used a standard cutaneous tumor induction protocol, in which CD-1 mice was treated with the tumor initiator of 7, 12-dimethylbenz [α] anthracene (DMBA) at a dose of 0.2 µmol or acetone alone on day 1 of the experiment, followed by promoting treatment with 5 µg of 12-O-tetradecanoylphorbol-13-acetate (TPA), with or without 5 nmoles of tacrolimus, twice a week for 20 weeks. CD4 and CD8 T cells in axillary and inguinal lymph nodes were also assessed by flow cytometry. RESULTS: After 14 wk, there was marked synergy between tacrolimus and the DMBA/TPA regimen, with 0.47 ± 0.13 new tumors per mouse per week in the tacrolimus/DMBA/TPA group vs. 0.10 ± 0.025 in the DMBA/TPA group, and 0.01 ± 0.002 in the group treated with DMBA and tacrolimus without TPA (P<0.01). A significant reduction in the ratio of CD4 to CD8 cells was found in lymph nodes in tacrolimus-treated mice five weeks after its application (Niwa et al, Br J Dermatol, in press, 2003). Though the serum FK506 concentration after topical application is 50 to 100 fold lower than when the drug is systemically administered, the concentration of FK506 in lymph nodes (6.3 ng/ml) after topical treatment was found not to differ significantly from that after systemic FK506 administration (5.3 ng/ml). These findings suggest that topical application produces high concentrations of FK506 in lymph, with subsequent depletion of CD4 T cells in lymph node. CONCLUSIONS: It has been already stated in the manufacturer's confidential documents of FK506 ointment before the legal allowance that tumor formation was accelerated in mice treated with topical FK506 after ultra violet light (UVL) irradiation. On account of the side-effect of the glucocorticosteroid ointment especially on the face, there has been a great enthusiasm for this topical FK506 therapy especially on the face. Our data suggest that restraint should be exercised in prescribing this regimen, especially for use on the face, and safety of this drug should be re-examined.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 1091 (Immunobiology).