Alterations in the inflammatory cells infiltrating basal cell carcinomas during immunocryosurgery

Immunocryosurgery, the combination modality of a cryosurgery session at day 14 of a 5-week daily imiquimod treatment cycle, has shown remarkable efficacy in the treatment of basal cell carcinoma (BCC). The modality was designed to exploit synergy of antitumor effects, including the induction of immune responses, elicited by imiquimod and cryosurgery. Herein, we report on the infiltration of the BCC by selected inflammatory cell species during an immunocryosurgery treatment cycle. The density of tissue infiltrating CD68⁺, CD3⁺ and Foxp3⁺ cells was studied by immunohistochemistry in 56 BCC biopsies from 28 treated sites (26 patients) at baseline and at days 12, 16 or 28 during treatment. Immunocryosurgery induces statistically significant alterations in all three cell species (p < 0.003): The density of CD68⁺ increased already by day 12 and remained at a higher level during the treatment thereafter. The density of CD3⁺ cells increased significantly between days 12 and 16 of treatment. The density of T_reg (Foxp3⁺) cells increased in the early phase of treatment (highest at day 12) to decrease significantly already 2 days after the cryosurgery session (day 16) and thereafter up to day 28 of the treatment cycle (p = 0.033). Within the tumor tissue, these alterations result in an abrupt increase in the CD3⁺/Foxp3⁺ ratio, a finding suggesting that the cryosurgical perturbation may probably play a decisive modulating role in the cellular composition of the inflammatory infiltrate during immunocryosurgery, eventually heralding the induction of an effective tumor-destructing immune response.