Molecular characterization of a novel cancer cell line established from human carcinoma in pleomorphic adenoma (CaPA-4)

Abstract

A cultured cell line (CaPA-4), derived from an undifferentiated carcinoma in a pleomorphic adenoma of the submandibular gland, was established through xenografted tumors in nude mice. Geneticin treatment eliminated surrounding mouse fibroblasts and yielded enriched tumor cells at an early stage of cell passage. In vitro, the line grew in a cobblestone pattern, revealing its epithelial origin. Chromosomal analysis by Giemsabanding confirmed its human origin, while electron microscopic examination showed its squamous-cell characteristics. CaPA-4 cells stained positive for the c-myc and Ha-ras antibodies. Molecular analysis showed over-expression of both c-myc and Ha-ras mRNA, with point mutation of p53 at codon 248 and of Ha-ras at codon 61. Amplification and rearrangement of the Ha-ras gene were observed; however, no loss of heterozygosity (LOH) of the p53 gene was detected by Southern blotting. This sequence of cancer-related gene activation may represent the malignant transformation from benign pleomorphic adenoma. This report describes the establishment and molecular characterization of this novel cell line from carcinoma in pleomorphic adenoma exhibiting squamous-cell differentiation. This could represent a useful model for investigating the cause of malignant transformation from human salivary-gland mixed tumors.