Imiquimod Enhances the Systemic Immunity Attained by Local Cryosurgery Destruction of Melanoma Lesions

Abstract

Melanoma lesions can be frozen in vivo, resulting in necrotic death of malignant cells and in tumor antigen release suitable for cross-presentation by professional antigen-presenting cells. Imiquimod is a small molecule with adjuvant pro-inflammatory effects that can be topically delivered as a cream. Local cryosurgery of B16/ovalbumin (OVA)-derived subcutaneous tumor nodules leads to curative destruction of the lesions. If imiquimod is repeatedly applied on the cryo-treated lesion, a conspicuous, leukocyte-rich inflammatory infiltrate appears during the days following treatment. Mice treated by cryosurgery plus imiquimod rejected rechallenges of B16/OVA in 90% of the cases, whereas cryosurgery alone failed to prevent tumor grafting in 70% of the cases. The combination treatment of B16/OVA tumors was also able to protect 60% of the mice against outgrowth of a lethal dose of non-transfected B16 tumor cells. Addition of imiquimod to cryosurgery results in increases of the cellular immune response against tumor antigens as measured by in vitro IFN-gamma production and T-cell proliferation in response to OVA. The potent memory response is not only directed against the OVA epitope, but also toward a broader range of B16 antigens. Our data indicate that these combined treatments turn the treated tumor lesion into an autologous tumor vaccine, which is even able to cause vitiligo in several cases. These preclinical data and the simplicity of the procedures warrant the design of a pilot clinical trial.

Current Technique and Application of Percutaneous Cryotherapy

“…Similar results could also be shown for the combination of cryoablation with Imiquimod, a TLR7 agonist and stimulator of dendritic cells [88]. The combination of CTLA-4 antibodies and cryoablation also improves the treatment result [89].…”

Immunomodulatory Effect of Imiquimod Through CCL22 Produced by Tumor-associated Macrophages in B16F10 Melanomas

“…The therapeutic effect of a TLR7 agonist (including IQM) or TLR7/8 dual agonist on melanoma growth in vivo has been previously reported (2,4,7,33). These reports revealed the immunostimulatory effect of these agonists through effector cells, such as CD8 + T cells, plasmacytoid DCs or M1 macrophages, and decrease the Tregs and MDSC in the tumor lesion, leading to the inhibition of B16F10 melanoma growth in vivo.…”

“…Localized TLR7/8 activation induces antitumor immunity and partially suppresses B16F10 melanoma growth in vivo (4,7,11). To confirm the potential therapeutic effect of IQM, we first examined the effect of IQM on murine B16F10 melanoma growth in vivo.…”

“…To investigate the immunomodulatory mechanisms responsible for the decrease of Tregs, we evaluated the immunomodulatory effects of topical IQM. We determined the mRNA expression of type 1 and 2 T helper cell (Th1/Th2)-related chemokines and CCL2, which is a key chemokine for the induction of antitumor effects in B16F10 melanoma (3,4,7,10), in tumors from IQM-treated and untreated mice by using qRT-PCR. Compared to untreated mice, topical IQM significantly decreased the mRNA expression of Th2/Tregrelated chemokines (CCL17 and CCL22) in the tumor microenvironment (Figure 2A).…”

“…Several reports have suggested that IQM may be an optimal reagent for invasive melanoma when used in combination with other therapies (3,4,7,10,11). Turza et al reported that IQM was effective in 10 cases of superficial dermal and subcutaneous metastasis of melanoma when used in combination with intralesional interleukin (IL)-2 (9).…”