Molecular Imaging for early detection of melanoma metastasis and response to therapy.

Purpose: Melanoma is considered one of malignant tumors, with poor therapy outcome particularly when metastatic lesions occur. Aim of this study is to test in vivo with Ultrasound Biomicroscopy (UBM) and PET/CT if a short interfering RNA (siRNA) could effectively contrast antiapoptotic action of the FKBP51 protein, a marker of malignancy and radioresistance of melanocytes. Methods: 8 nude mice, Balb/c NOD SCID IL2gamma (null) strain, 4-5 weeks old, received an iv injection of 1,5x106 melanoma cells (SAN) in 100 ?l of PBS. 4 mice 15 and 24 days post SAN injection received iv siRNA therapy (Group 1), and 4 mice had no therapy (CTRL Group). All mice were weekly monitored with UBM to detect hepatic lesions, and were analyzed with 18F- fluorodeoxyglucose (FDG) at day 27 post melanoma cells injection. Results: Group 1 showed no or rare liver metastasis at UBM examination, and a low 18F- FDG uptake limited to small lungs area liver (lung SUV Mean 0.75, lung SUV Max 0.77, liver SUV Mean 0.37; liver SUV Max 0.40). CTRL Group showed diffuse metastatic lesion both in liver and lung and a high 18F- FDG uptake in lung and liver (lung SUV Mean 1.13, lung SUV Max 0.88, liver SUV Mean 1.14; liver SUV Max 1.2). Imaging results are correlated with macroscopic post mortem lung and liver findings. Conclusion: Multimodality Molecular Imaging is able to monitor non invasively the progression of melanoma metastatic disease and therapy outcome.