Our previous in vivo studies indicated that a phenolic
thioether amine (
PTEA),
4-S-cysteaminylphenol (CAP), selectively disintegrates melanocytes of black hair and skin, and inhibits the growth of murine and human
malignant melanomas. To elucidate the mechanism of the in vivo melanocytotoxicity and anti-
melanoma effect, this study examined the selectivity and specificity of
PTEA incorporation into
malignant melanoma cells using [14C]4(2)-S-CAP, and then identified a
PTEA-
binding protein through a
ligand binding assay using [125I]-labelled cell lysates. Whole body autoradiography showed that [14C]4-S-CAP is selectively incorporated and accumulated into the eye and tumours of a
B16 melanoma-bearing mouse. SK MEL 23 human
melanoma cells also showed a steady accumulation of [14C]4-S-CAP (threefold at least up to 5 min) and of [14C]2-S-CAP (sevenfold up to 20 min), compared with that of HeLa cells and fibroblasts, which plateau at 5 min. Chromatography of 4-S-CAP on an affinity column (both CH- and CNBr-activated
Sepharose 4B) identified a 58 kD
protein in
melanoma cells, which was present at very low levels in HeLa cells; this 58 kD
protein was retained by both 4-S- and 2-S-CAP affinity columns, but not by columns of a phenolic
thioether (cysteinylphenol: CP) or a phenolic
thioether amide (N-acetyl-4-S-CAP), and could be retrieved by either 4-S or 2-S-CAP but not by CP and N-acetyl-4-S-CAP. This
protein was glycosylated, and contained
mannose residues.(ABSTRACT TRUNCATED AT 250 WORDS)