Experimental rationale for treatment of high-risk human melanoma with zinc chloride fixative paste : Increased resistance to tumor challenge in murine melanoma model

Fixed-tissue micrographic surgery (Mohs) of melanoma has been shown by retrospective analysis to improve 5-year survival. To determine whether zinc chloride fixative paste acts as an immune adjuvant to increase host resistance to melanoma. We performed a murine study using the poorly immunogenic B16 melanoma of C57Bl6J mice, and the more immunogenic K1735p melanoma of C3H/HeN mice. Tumors were treated with zinc chloride paste and excised 24 hours later (Group 1), or simply excised (Group 2). Mice were challenged 7 days later with injection of melanoma cells at a distant site, and tumor growth in this second site was followed. K1735p melanomas developed at the challenge site in 69% of mice treated with excision versus 32% of mice treated with zinc chloride fixation (P < 0.025). Development of B16 melanoma was not altered by zinc chloride fixation. Zinc chloride fixation of the more immunogenic K1735p melanoma increased resistance to subsequent tumor challenge, suggesting that zinc chloride fixative paste acts as an immune adjuvant.