CPEC induces erythroid differentiation of human myeloid leukemia K562 cells through CTP depletion and p38 MAP kinase

Abstract

Cyclopentenyl cytosine (CPEC) is a carbocyclic cytidine analog inhibitor of CTP synthetase and experimental drug for combination chemotherapy. CPEC treatment (50 nM) depleted intracellular CTP and induced a specific S-phase arrest and erythroid differentiation of human erythroleukemia K562 cells. The equilibrative nucleoside transporters (ENT1, 2) facilitated uptake of CPEC into K562 cells as evidenced by both NBMPR and dipyridamole inhibition of CPEC-mediated CTP depletion and erythroid differentiation. Incubation with the pyridinylimidazole p38 MAPK inhibitors, SB203580 or SB220025, suppressed both the CPEC-induced cell cycle arrest and differentiation of K562 cells. SB203580 also prevented the cell cycle arrest and erythroid differentiation of K562 cells induced by Leflunomide (LEF), a non-nucleoside inhibitor of the de novo pyrimidine pathway, without affecting LEF-induced depletion of pyrimidine pools. Finally, selective knockdown of p38 MAPK by using Smart Poolt siRNA to p38 MAPK significantly decreased the CPEC-induced differentiation of K562 cells. These results suggest that endogenous activity of p38 MAP kinases may be required for committing K562 cells to cell cycle arrest and erythroid differentiation under conditions of CTP depletion.

Cyclopentenyl Cytosine Induces Senescence in Breast Cancer Cells through the Nucleolar Stress Response and Activation of p53

“…1). The addition of cytidine, shown previously to replenish intracellular CTP pools through its phosphorylation to CMP via uridine/cytidine kinase (Huang et al, 2004), almost completely prevented both the differentiation of MDA-MB-231 cells ( Fig. 2A) and the senescence of MCF-7 cells (Fig.…”

“…Cyclopentenyl cytosine (CPEC) is an analog of cytidine (Kang et al, 1989) and enters cells preferentially through the equilibrative nucleoside transporters, including equilibrative nucleoside transporters 1 and 2 (Huang et al, 2004). CPEC is intracellularly metabolized into its mono-, di-, and triphosphate forms (Kang et al, 1989).…”

“…In its triphosphate form, it serves as a specific noncompetitive inhibitor of CTP synthetase, which catalyzes the conversion of UTP to CTP as the predominant pathway for CTP synthesis in proliferating cells (Schimmel et al, 2007). As a result, the intracellular CTP pool is depleted rapidly (Kang et al, 1989;Huang et al, 2004). Previous studies have established the antitumor effects of CPEC using a number of tumor cell lines (Schimmel et al, 2007) and several tumor models (Schimmel et al, 2007;Van Bree et al, 2009).…”

A survey of the signaling pathways involved in megakaryocytic differentiation of the human K562 leukemia cell line by molecular and c-DNA array analysis

“…PMA-induced differentiation of K562 cells is intimately associated with the expression of several genes (Alitalo, 1990;Cheng et al, 1994;Namciu et al, 1994;Belhacene et al, 1998;Jacquel et al, 2003). To date, very few studies have analysed at a large scale (c-DNA array or DNA biochips) gene expression in K562 cells undergoing differentiation towards the megakaryocytic or erythroid lineage (Jacquel et al, 2003;Pettiford and Herbst, 2003;Huang et al, 2004). It is well established that in vitro differentiation of K562 cells is characterized by morphological changes such as an increase in cell size and adhesion properties of the differentiating cells.…”

“…As previously mentioned, Erk1/2 activation is required for PMA-induced differentiation of K562 cells towards the megakaryocytic lineage, while both inhibition of this pathway and activation of the p38 MAPK are likely to play a role in signal transduction mechanisms leading to erythroid differentiation (Park et al, 2001;Huang et al, 2004;Uddin et al, 2004). Although Erk1/2 activation is thought to be important for differentiation of K562 cells towards the megakaryocytic lineage, the role of other pathways such as p38 MAPK and JNK is far less documented.…”