-Original-

A New Anorectal Melanoma Cell Line Derived from a Primary Human Rectal Tumor

Seiichi Shinji¹, Yuuki Shichi², Takeshi Yamada¹, Goro Takahashi¹, Ryo Ohta¹, Hiromichi Sonoda¹, Akihisa Matsuda¹, Kazuhide Yonaga¹, Takuma Iwai¹, Kohki Takeda¹, Koji Ueda¹, Sho Kuriyama¹, Toshimitsu Miyasaka¹, Yoshibumi Ueda³, Norihiko Sasaki⁴, Kimimasa Takahashi⁵, Ryuji Ohashi⁶, Toshiyuki Ishiwata², Tomio Arai⁷ and Hiroshi Yoshida¹

¹Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Nippon Medical School, Tokyo, Japan
²Division of Aging and Carcinogenesis, Research Team for Geriatric Pathology, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
³Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan
⁴Research Team for Geriatric Medicine (Vascular Medicine), Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
⁵Department of Veterinary Pathology, School of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan
⁶Department of Integrated Diagnostic Pathology, Nippon Medical School, Tokyo, Japan
⁷Department of Pathology, Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Tokyo, Japan

Background: Anorectal melanoma is a rare disease with a poor prognosis. Symptoms are often nonspecific, which complicates preoperative diagnosis. Here, we describe the establishment of MELS, a new anorectal melanoma cell line derived from resection of a rectal tumor in a 40-year-old Japanese man.
Methods: Histological, electron microscopic, and immunohistochemical features of S-100, HMB-45, Melan-A, and NSE positivity of the tumor were typical of surgically resected anorectal melanoma.
Results: MELS cells are round or oval and have sharp thorn-like protrusions on some or all cell membranes. The cells form irregular attached colonies with numerous floating cells in two-dimensional culture. Transmission electron microscopy revealed that some MELS cells have cytoplasmic melanosomes. Immunocytochemically, MELS cells and surgical tissues had the same staining pattern. 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.
Conclusions: No previous report provided detailed clinical information on an anorectal melanoma cell line. Thus, MELS cells should improve our understanding of the biological characteristics of anorectal melanoma and provide a novel platform for examining the effects of therapies for anorectal melanoma.

J Nippon Med Sch 2022; 89: 368-376

Keywords
anorectal melanoma, novel cell line, colorectal cancer, electron microscopy, HMB-45

Correspondence to
Seiichi Shinji, Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
s-shinji@nms.ac.jp

Received, September 20, 2021
Accepted, November 10, 2021