Establishment and characterization of a novel anorectal melanoma cell line derived from primary human rectal tumor

Anorectal melanoma is a rare disease with poor prognosis and nonspecific symptoms, leading to difficulties in preoperative diagnosis. Here, we describe the establishment of MELS, a novel anorectal melanoma cell line derived from tumor resection of the rectum in a 40-year-old Japanese man.Histological, electron microscopic, and immunohistochemical features of S-100, HMB-45, Melan-A, and NSE positivity in the patient's tumor were confirmed as typical of surgically resected anorectal melanoma.MELS cells are round or oval cells with sharp thorn-like protrusions on some or all of the cell membrane. They form irregular attached colonies with numerous floating cells in two-dimensional culture. Transmission electron microscopy revealed that some MELS cells possess cytoplasmic melanosomes. Immunocytochemically, MELS cells showed the same staining patterns as surgical tissues. MELS cells had lower growth rates than Caco-2 (a colon adenocarcinoma cell line) and A375 (a cutaneous melanoma cell line) cells. Oxaliplatin and irinotecan were more effective in MELS cells than in Caco-2 and A375 cells.Prior to our study, no reports had provided detailed clinical information on anorectal melanoma cell lines. Thus, MELS cells should improve current knowledge on the biological behaviors of anorectal melanoma, while providing a novel platform for examining the effects of anorectal therapies.