In support of this notion, Friedmann et al. have found that a marked increase in cAMP levels (950% of a control), which can be achieved by irreversible and direct stimulation of ADCY, leads to a 10.9-fold rise of melanin content, whereas a relatively small increase in cAMP levels (260% of the control), resulting from melanocortin 1 receptor stimulation, increases melanin content by only 35% in melanoma cells during 7-day culture [43]. This evidence concerns the gene MC1R and melanoma.