Melanoma is the deadliest form of
skin cancer, partially due to its inherent resistance to
therapy. Here, we test in live larvae the hypothesis that mature melanosomes contribute to resistance to chemotherapeutic
drug,
cisplatin, via
drug sequestration. We also compare three melanosome biogenesis
proteins-
microphthalmia-associated transcription factor (Mitfa), vacuolar protein sorting 11 (Vps11) and
oculocutaneous albinism 2 (
Oca2) to determine their respective contributions to chemoresistance. Melanocytes in zebrafish larvae harbouring loss-of-function mutations in the mitfa, vps11 or
oca2 genes are more sensitive to
cisplatin damage than wild-type larvae. As a comparison, we examined sensory hair cells of the lateral line, which are sensitive to
cisplatin. Hair cells in
oca2 and mitfa mutants do not show increased
cisplatin sensitivity when compared to wild-type larvae, suggesting the increase in
cisplatin sensitivity could be melanocyte specific. However, hair cells in vps11 mutants are more sensitive to
cisplatin than their wild-type counterparts, suggesting that this mutation increases
cisplatin susceptibility in multiple cell types. This is the first in vivo study to show an increase in chemotherapeutic
drug sensitivity when melanosome maturation mutations are present. The
proteins tested, especially
Oca2, represent novel
drug targets for increasing the efficiency of
melanoma chemotherapy treatment.