The development and progression of human malignant melanoma is believed to be due to multiple genetic alterations resulting in complex changes in expression of many genes. The parental malignant melanoma cell line UACC903 displays anchorage-independent growth and the chromosome 6-mediated suppressed subline Clone1 is anchorage-dependent1. The revertant cell line SRS3, derived from Clone1 by retroviral transduction, resembles the phenotype of UACC903 ref.2. Here we describe identification of the chromosome 6-encoded tumour-suppressor gene encoding connexin43 (Cx43) by cDNA microarray and suppression of the anchorage-independent growth of UACC903 by overexpression of this gene. We first measured expression of 4,536 genes between UACC903, Clone1 and SRS3 using cDNA microarrays, resulting in 7.08% of genes (321/4,536) showing changes in their expression levels. Notably, 12 genes displayed higher levels of expression in Clone1 than in both UACC903 and SRS3, providing candidates for further identification of tumour-suppressor genes. Genes encoding Cx43 (suppressor activity), monocyte chemotactic protein1 (MCAF/MCP1; suppressor activity) and cysteine proteinase CPP32a (apoptotic activity) were all upregulated in Clone1 in contrast to both UACC903 and SRS3. Transfection of Cx43, encoded on chromosome 6q21–q23, a region frequently altered in malignant melanoma, resulted in its overexpression and suppression of anchorage-independent growth of UACC903. Thus, our results demonstrate that the combination of the ability to alter cellular phenotype by successive genetic alterations and the ability to examine the gene expression patterns facilitates identification of a tumour-suppressor gene.
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