Examining the reliability of surrogate tissue predictability of drug efficacy in reconstituted human 3D skin models containing melanomas.

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49 Background: Melanoma has a poor survival rate in advanced stages due to the lack of efficacious approved treatments. However, melanoma’s dermal location enables the application of human skin models. These models mimic many important characteristics of skin in vivo and obviate the use of invasive procedures. Monitoring gamma-H2AX foci to assess DNA double-strand break (DSB) levels in reconstituted human 3D skin tissue harboring melanoma tumor cells may provide insights into important questions in cancer research. In addition to the differential toxicities of anti-cancer agents on the various cell types, we examine how the early drug response of normal tissues might serve as surrogates for predicting treatment efficacy on the tumors. Methods: Commercially available reconstituted 3D human skin tissue consists of dermal fibroblast and epidermal keratinocyte layers with malignant melanoma A375 cells which have been cultured to form a multilayer, highly differentiated epidermis containing various stages of cutaneous melanoma malignancy. Drugs representative of several different categories were studied, including bleomycin (a radiomimetic), camptothecin (a topoisomerase I inhibitor), temozolomide (a DNA alkylating agent), AZD6244 (a MEK inhibitor), Vorinostat (a HDAC inhibitor) and cisplatin (a DNA intercalatingagent). DNA DSB levels were monitored by gamma-H2AX foci formation and apoptosis by TUNEL assay. Tumor growth was monitored by H&E staining. Results: A wide range of responses in both tumor and normal tissue by various drugs were observed, including tumor regression and normal tissue toxicity. The early responses of normal tissues depended on the treatment, providing insights into the use of surrogate tissues as predictors of drug efficacy and later tumor regression. Conclusions: Measuring DNA DSB damage in reconstituted 3D skin tissue is an attractive model for studying the efficacy and toxicity of genotoxic drugs against melanoma. If validated, such models would help reduce the use of animals for preclinical studies.