A non‐apoptotic function of caspase‐3 in pharmacologically‐induced differentiation of K562 cells

Abstract

Background and purpose: Several anticancer drugs with diverse chemical structures can induce differentiation of cancer cells. This study was undertaken to explore the potential contribution of caspase-3 to pharmacologically-induced differentiation of K562 cells. Experimental approach:We assessed differentiation by measuring the expression of glycophorin A and haemoglobin synthesis in K562 cells treated with low concentrations of doxorubicin, hydroxyurea, cytosine arabinoside, cisplatin and haemin. Caspase-3 activation, mitochondrial membrane potential dissipation and viability were assessed by FACS. GATA-1-binding activity was evaluated by EMSA. Key results: Treatment of K562 cells with low concentrations of the tested drugs activated caspase-3 but did not trigger detectable apoptosis. Instead, elevated levels of haemoglobin-positive and glycophorin A/caspase-3-double-positive cells were observed, suggesting involvement of caspase-3 in drug-induced differentiation. Inhibition of caspase-3 activity significantly reduced the ability of K562 cells to execute the differentiation programme. Mitochondrial membrane potential dissipation was observed, indicating involvement of the mitochondrial pathway. Binding activity of GATA-1, transcription factor responsible for differentiation and cell survival, was not diminished by increased caspase-3 activity during drug-stimulated differentiation. Conclusions and implications:Our results could explain how anticancer drugs, with diverse structures and modes of action, can stimulate erythroid differentiation in leukaemic cells with appropriate genetic backgrounds. Our findings imply that some similarities exist between pharmacologically-induced differentiation of erythroleukaemic cells and normal erythropoiesis, both involving caspase-3 activation at high levels of anti-apoptotic protein Bcl-X L and chaperone protein Hsp70 (heat shock protein 70). Therefore, the functions of caspase-3, unrelated to cell death, can be extended to pharmacologically-induced differentiation of some cancer cells.

A high concentration of triiodothyronine attenuates the stimulatory effect on hemin-induced erythroid differentiation of human erythroleukemia K562 cells

“…As shown in Table 2, cells were strongly positive for CD71 and rarely positive for CD235a. Treatment with 40 μM hemin for 72 h did not change the MFI or the CD235a-positive rate, but increased the CD71-positive rate, as seen in previous studies in K562 cells [17,[23][24][25].…”

“…This conclusion is compatible with the welldid not differ between T3-pretreated and control cells after hemin induction. This is probably because benzidine positivity with hemin treatment may be affected by free hemin diffusing into the cells, which may cause misleading results [25,29]. Overall, these findings indicate that T3 at a lower concentration acts as an enhancer of hemin and that 100 nM T3 blocks this effect in our model of erythroid differentiation.…”

Caspase-3 cleaves hnRNP K in erythroid differentiation

“…Additionally, we show that hnRNP K is not ubiquitinated in K562 cells and proteasome inhibitors fail to stabilize the protein. Caspases not only catalyze site-specific protein cleavage in apoptosis, 11 but were also shown to be activated in terminal erythroid differentiation, 12, 13, 14 which is not associated with apoptosis. 15 Interestingly, a specific N-terminal hnRNP K fragment that migrates at 48 kD accumulates during erythroid differentiation.…”

The differentiation effect of low-dose cytosine arabinoside is disturbed in PU.1-knockdown K562 cells

“…1A. The range of the Ara-C dose and time of incubation for erythroid differentiation was based on the results published by Sztiller-Sikorska et al (8). Based on the data presented in Fig.…”

“…Several studies indicated that low concentrations of cytosine arabinoside (Ara-C) induce erythroid differentiation of K562 cells (7,8). In this study, we investigated whether the effects of Ara-C are also associated with the expression level of PU.1.…”