Abstract 4233: Mef2C enhances 1,25-dihydroxyvitamin D3-induced monocytic differentiation of human myeloid leukemia cells by regulating C/EBP{beta} expression

Myogenic enhancer factors 2 (Mef2) are members of the family of MADS (MCM1-agamous-deficiens-serum response factor)-box transcription factors known to have multiple roles in morphogenesis of skeletal, cardiac and smooth muscle cells. Recently, Mef2C was found to be also involved in hematopoiesis. Bone marrow cells isolated from Mef2C knockout mice demonstrated decreased monocytic differentiation in response to cytokine stimulation, whereas constitutive expression of Mef2C promoted monopoiesis. The above findings led us to examine the role of Mef2C in 1,25-dihydroxyvitamin D3 (1,25D)-induced monocytic differentiation. Human acute myeloid leukemia (AML) cell lines, HL60 and U937, were used in this study. We found that knockdown of Mef2C with small interfering RNA (siRNA) significantly decreased the expression of the monocytic marker CD14, as well as of nonspecific esterase (NSE), suggesting that Mef2C is required for 1,25D-induced monocytic differentiation in AML cells. Our laboratory has previously demonstrated that optimal monocytic differentiation induced by 1,25D requires ERK5, and that ERK5 expression shows positive correlation with Mef2C expression. Here we show that Mef2C knockdown demonstrates similar inhibition of CD14 expression as ERK5 knockdown. CCAAT-enhancer-binding proteins (C/EBPs) α and β are two major transcription factors that can directly regulate CD14 expression. Since 1,25D has been shown to increase both C/EBPα and β expression, and these two transcri...
Source: Cancer Research - Category: Cancer & Oncology Authors: Tags: Molecular and Cellular Biology Source Type: research