LEDGF/p75 has increased expression in blasts from chemotherapy-resistant human acute myelogenic leukemia patients and protects leukemia cells from apoptosis in vitro

<p>Abstract</p> <p>Background</p> <p>Relapse due to chemoresistant residual disease is a major cause of death in acute myelogenous leukemia (AML). The present study was undertaken to elucidate the molecular mechanisms of chemoresistance by comparing differential gene expression in blasts from patients with resistant relapsing AML and chemosensitive AML.</p> <p>Results</p> <p>About 20 genes were identified as preferentially expressed in blasts pooled from patients with resistant disease, as compared to chemosensitive AML blasts, based on differential gene expression screening. Half of these genes encoded proteins related to protein translation, of these a novel protein related to the ribosomal stalk protein P0. Other upregulated mRNAs coded for cytochrome C oxidase III, the transcription factors ERF-2/TIS11d, and the p75 and p52 splice variants of Lens Epithelial Derived Growth Factor (LEDGF). Analysis of blasts from single patients disclosed that LEDGF/p75 was the most consistently upregulated mRNA in resistant AML. Transfection experiments demonstrated that LEDGF/p75 and p52b antagonized daunorubicin-induced and cAMP-induced apoptosis in an AML cell line. Also HEK-293 cells were protected against daunorubicin by LEDGF/p75 and p52b, whereas LEDGF/p52 splice variants lacking exon 6 had proapoptotic effects. Interestingly, full length LEDGF/p75 protected against truncated pro-apoptotic LEDGF/p75.</p> <p>Conclusion</p> <p>Our results provide evidence for an association between the overexpression of genes encoding survival proteins like LEDGF/p75 and chemo-resistance in acute myelogenous leukemia. LEDGF/p75 has previously not been shown to protect against chemotherapy, and is a potential drug target in AML.</p

Expression of the potential therapeutic target CXXC5 in primary acute myeloid leukemia cells -high expression is associated with adverse prognosis as well as altered intracellular signaling and transcriptional regulation

International audienceThe CXXC5 gene encodes a transcriptional activator with a zinc-finger domain, and high expression in human acute myeloid leukemia (AML) cells is associated with adverse prognosis. We now characterized the biological context of CXXC5 expression in primary human AML cells. The global gene expression profile of AML cells derived from 48 consecutive patients was analyzed; cells with high and low CXXC5 expression then showed major differences with regard to extracellular communication and intracellular signaling. We observed significant differences in the phosphorylation status of several intracellular signaling mediators (CREB, PDK1, SRC, STAT1, p38, STAT3, rpS6) that are important for PI3K-Akt-mTOR signaling and/or transcriptional regulation. High CXXC5 expression was also associated with high mRNA expression of several stem cell-associated transcriptional regulators, the strongest associations being with WT1, GATA2, RUNX1, LYL1, DNMT3, SPI1, and MYB. Finally, CXXC5 knockdown in human AML cell lines caused significantly increased expression of the potential tumor suppressor gene TSC22 and genes encoding the growth factor receptor KIT, the cytokine Angiopoietin 1 and the selenium-containing glycoprotein Selenoprotein P. Thus, high CXXC5 expression seems to affect several steps in human leukemogenesis, including intracellular events as well as extracellular communication. INTRODUCTION CXXC5 is a retinoid-responsive gene localized to the 5q31.3 chromosomal region [1] and encoding a retinoid-inducible nuclear factor (RINF) [2] that is a protein containing a CXXC-type zinc-finger domain and acting as a transcription regulator [3]. Expression studies as well as gene silencing experiments suggest that CXXC5 is important in normal myelopoiesis [2] and for differentiation of endothelial cells [3]. Furthermore, we recently described that CXXC5 is expressed in primary acute myeloid leukemia (AML) cells; this expression shows a wide variation between patients and high levels are associated with an adverse prognosis and resistance to chemotherapy-induced apoptosis [4]. Another study recently confirmed our observations and CXXC5 expression was then of independent prognostic significance in multivariate analyses after adjustmen