Functional analysis of candidate antigens identified by DNA microarray for highly expression in melanoma

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The identification of molecules that are preferentially expressed in melanoma cells and involved in their malignant phenotypes is important for understanding of melanoma biology and the development of new diagnostic and therapeutic methods. By comparing the expression profile of a melanoma cell line with those of various normal tissues using GeneChip, and by confirming the actual expression of the selected genes by RT-PCR, we identified FABP7,MMA1 and KU-MEL-3. These genes were analyzed for their function by RNA interference and recombinant transduction. By down-regulating the FABP7 expression with FABP7 specific siRNAs, in vitro cell proliferation and Matrigel invasion were suppressed in melanoma cell lines. Over-expression of FABP7 in a FABP7 negative embryonic kidney cell line 293T by transfecting with the FABP7 cDNA, resulted in enhanced cell proliferation and Matrigel invasion, indicating that FABP7 plays a role in the malignant phenotype of some melanoma cell lines. MMA1 down-regulation with MMA1 specific siRNAs suppressed in vitro cell proliferation and cell adhesion in melanoma cell lines. Over-expression of MMA1 in the melanoma cell lines with low MMA1 expression by transfecting with the MMA1 recombinant resulted in enhanced cell proliferation and adhesion, indicating that MMA1 also plays a role in the malignant phenotype of melanoma cells. Immunohistochemical examination revealed that FABP7 was expressed in 11 of 15 melanoma tissues. IgG Antibodies specific for the phage or bacterial recombinant FABP7 protein were detected in 14 of 25 (56%) or 8 of 31 (26%) sera from melanoma patients, respectively, but not in sera from healthy individuals, indicating that FABP7 is an immunogenic antigen in melanoma patients. These results demonstrated that FABP7 and MMA1 frequently expressed in melanoma may be potential targets for development of diagnostic and therapeutic methods.