Rationale: Having established cell culture and xenograft systems for studying patient melanoma samples, the researchers were able to grow tumors in vitro and in vivo from single cells and found a correlation of tumor metastatic behavior in immunocompromised mice and in patients. Recently they have extended the experiments to examine melanoma sensitivity to novel compounds. In screens of FDA approved drugs, they found several cardenolides including digoxin that reproducibly exhibited greater toxicity to primary human melanomas as compared to a range of normal human cells. They then examined the anti-tumor efficacy against primary human melanomas growing in vivo as xenografts. While trametinib, vemurafenib, and digoxin and digitoxin individually slowed the growth of human melanomas xenografts, they did not cause tumor regression. However, the combination of digoxin or digitoxin and trametinib caused substantial tumor regression using melanomas obtained from multiple patients, some with BRAF mutations and some without. The effects were dramatically better than trametinib, digoxin, digitoxin or vemurafenib alone. No difference in efficacy for the combination was seen in BRAF mutant and BRAF wild-type samples.