Anti-Apoptosis and Cell Survival Gene Expression Profile in LAD2 Cells

For over 10 years, LAD2 cells have been used for human mast cell research. Unlike HMC1 cells which are presumed immortalized by D816V KIT mutations, LAD2 cells have no mutations in KIT to explain their survival. We therefore examined anti-apoptosis and cell survival gene expression as a first step to understand LAD2 cell persistence in culture. RNA was prepared from both LAD2 cells and CD34-derived human mast cells (HuMCs) from normal subjects (98-I-0027). Analysis of genes participating in anti-apoptotic and cell survival functions was performed using cDNA and Affymetrix GeneChip RNA Array following normalization. Hierarchically clustered displays of differentially expressed genes were compared for HuMCs and LAD2 cells. In LAD2 cells, two subunits of the anti-apoptotic gene NF-kappaB, NFKB1 and NFKB2, were highly upregulated concurrent with downregulation of the pro-apoptotic genes p53 and CDKN2A. CASP3 was downregulated while its substrate CDKN1A was upregulated, contributing to anti-apoptosis. Telomere lengthening remained a stable process. Hierarchical clustering showed strong grouping and significant enrichment in LAD2 cells of differentially expressed genes participating in anti-apoptosis and cell survival. The overall gene expression profile in LAD2 cells showed enrichment for anti-apoptosis. The observation that LAD2 cells survive without rhSCF but require rhSCF for growth, suggests that NF-kappaB activation, reduced cell cycle inhibition, decreased p53-induced apoptosis and stable telomere lengthening may contribute to LAD2 cell immortalization. Additional research to identify controls on the expression of these genes may help us further understand aberrant mast cell development in mastocytosis.