Additional mechanisms explaining the antitumor activity of IMQ will also be less than discussion. peripheral bloodCderived CD11c+ mDCs acquired antiperforin and antiCgranzyme B reactivity upon TLR7/8 activation and could use these molecules to efficiently lyse major histocompatibility complex (MHC) class Ilo malignancy cell lines. The same activation protocol led pDCs to destroy MHC class ICbearing Jurkat cells inside a TRAIL-dependent fashion. While suggesting that mDCs and pDCs are directly involved in the IMQ-induced damage of BCC lesions, our data also add a fresh facet to the practical spectrum of DCs, ascribing to them a major role not only in the initiation but also in the effector phase of the immune response. Desire for imiquimod (IMQ) 1st came from the observation that this imidazoquinoline exerts a serious activity against viral SU 5214 acanthomas that was originally explained by its IFN-inducing capacity (1). When used topically for a prolonged period of time, it can lead to the regression of particular virus-induced (e.g., genital warts  and molluscum contagiosum ) and additional (e.g., basal cell carcinoma [BCC] [4, 5] and lentigo maligna ) pores and skin neoplasms. IMQ exerts its biologic activity primarily by ligation of Toll-like receptor (TLR) 7 (7) and, to a lesser degree, TLR8, both of which have been identified as natural receptors for single-stranded RNA (8, 9). Cell activation SU 5214 via TLR7 and TLR8 prospects to downstream activation of NF-B and additional transcription factors (10, 11). As a result, several genes encoding mediators and effector molecules of the innate as well as the adaptive immune response are transcribed (12C14). Because of their prominent manifestation of TLR7 and TLR8, plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) (15, 16), respectively, are consequently likely candidates for the initiation of the IMQ-induced sponsor defense reaction. Additional mechanisms explaining the antitumor activity of IMQ will also be CD274 under conversation. These include (a) the reversal of CD4+ regulatory T cell function (17), (b) a TLR-independent immunostimulatory action of IMQ via adenosine receptor signaling (18), (c) direct (19) and indirect, via IFN- (20), IMQ-induced proapoptotic effects on tumor cells, and (d) an antiangiogenic activity of IMQ, as demonstrated inside a mouse model of angiogenesis (21, 22). In a recent study, our group investigated IMQ-induced tumor regression in mice and found not only a good clinical response of the tumors to the topically applied compound but also a direct correlation between IMQ-induced tumor regression and the denseness of DCs in the peritumoral cells (23). Not infrequently, malignancy cells in death were found in close contact with DCs, which was compatible with a tumoricidal house of the second option (24, 25). In this study, we wanted to determine whether related phenomenona also happen during IMQ treatment of human being pores and skin cancers and, if so, to unravel the mechanisms responsible for IMQ-induced tumor regression. RESULTS Regression of BCC upon IMQ treatment Seven individuals with histopathologically confirmed superficial BCC were SU 5214 treated with IMQ. After a treatment period of 6 wk, we observed a complete medical (Fig. 1) and histopathological response in all individuals. No indications of SU 5214 recurrence were noted in any of the individuals adopted for at least 10 mo. Open in a separate window Number 1. Total regression of superficial BCC after a 6-wk treatment period with IMQ. IMQ topically applied five instances a week for a period of 6 wk led to a local inflammatory response, which resulted in a complete medical and histopathological tumor clearance in all individuals treated. The clinical photos are representative for those individuals (= 7) treated with IMQ. In accordance with a previous statement (4), all individuals developed, before tumor clearance, SU 5214 an inflammatory cells reaction at the site of IMQ software. It began as erythema after 2C3 d of treatment; became erosive during the second week (Fig. 1); appeared mainly because crusting and, later on, scaling plaques after 3C4 wk; and resolved completely after cessation of IMQ treatment. Systemic side effects such as flu-like symptoms, lymphadenopathy, myalgia, or changes in laboratory ideals never occurred in any of our individuals. Emergence kinetics of leukocytic populations in the peritumoral infiltrate upon IMQ treatment Biopsies from BCCs were acquired before, during, and after IMQ treatment and subjected to immunofluorescence analysis using a broad panel of antibodies (Table I) to analyze, both quantitatively and qualitatively, the composition and kinetics of the IMQ-induced inflammatory infiltrate. In untreated BCCs we found a sparse infiltrate, primarily consisting of T cells of the helper phenotype (Table II). Upon 2 wk of IMQ treatment, a dramatic increase of CD8+ T cells and, to a much lesser degree, of CD4+ T cells was seen around tumor cell islets (Table II). Fig. 2 (A and B) demonstrates, after 2 wk of topical IMQ treatment, BCC islets were surrounded and partly infiltrated by dendritically formed cells exhibiting either the CD11c+/HLA-DR+.