Activin A induction of erythroid differentiation sensitizes K562 chronic myeloid leukemia cells to a subtoxic concentration of imatinib

Abstract

Chronic myeloid leukemia (CML) is a hematopoietic stem/progenitor cell disorder in which Bcr-Abl oncoprotein inhibits cell differentiation. Differentiation induction is considered an alternative strategy for treating CML. Activin A, a member of the transforming growth factor-β superfamily, induces erythroid differentiation of CML cells through the p38 MAPK pathway. In this study, treatment of the K562 CML stem/progenitor cell line with activin A followed by a subtoxic concentration of the Bcr-Abl inhibitor imatinib strongly induced growth inhibition and apoptosis compared with simultaneous treatment with activin A and imatinib. Imatinib-induced growth inhibition and apoptosis following activin A pretreatment were dose- and time-dependent. Imatinib-induced growth inhibition and apoptosis were also dependent on the pretreatment dose of activin A. More than 90% of the activin A-induced increases in glycophorin A-positive cells were sensitive to imatinib. However, only some of original glycophorin A-positive cells in the activin A treatment group were sensitive to imatinib. Sequential treatment with activin A and imatinib decreased Bcr-Abl, procaspase-3, Mcl-1, and Bcl-xL and also induced cleavage of procaspase-3/poly(ADP-ribose)polymerase. The reduction of erythroid differentiation in p38 MAPK dominant-negative mutants or by short hairpin RNA knockdown of p38 MAPK decreased the growth inhibition and apoptosis mediated by sequential treatment with activin A and imatinib. Furthermore, the same inhibition level of multidrug resistance 1 expression was observed in cells treated with activin A alone, treated sequentially with activin A and imatinib, or treated simultaneously with activin A and imatinib. The p38 MAPK inhibitor SB-203580 can restore activin A-inhibited multidrug resistance 1 expression. Taken together, our results suggest that a subtoxic concentration of imatinib could exhibit strong cytotoxicity against erythroid-differentiated K562 CML cells.

<p>Arsenic sulfide nanoformulation induces erythroid differentiation in chronic myeloid leukemia cells through degradation of BCR-ABL</p>

“…It is well-documented that p38 MAPK was involved in the erythroid differentiation of K562 cells;2,17,18 here consistently we observed that ee-As 4 S 4 increased the expression of p-p38 MAPK in K562 cells after 72 hr incubation (Figure 2E). When a p-38 inhibitor SB202190 was supplemented in the culture medium, the expression level of CD235a went down (Figure 2F), demonstrating that ee-As 4 S 4 induced erythroid differentiation through the phosphorylation of p38 MAPK.…”

Activin A: an emerging target for improving cancer treatment?

“…No effect of activin A treatment on the response to seven anticancer drugs (cisplatin, carboplatin, doxorubicin, taxol, SN38, terarubicin and etoposide) was found, in contrast, in an ovarian adenocarcinoma cell line, but a cisplatin-resistant derivative showed decreased activin A sensitivity by loss of activin receptor type 2 expression [81]. In diffuse large B-cell lymphoma, ectopic expression of activin A resulted in reduced cell growth and enhanced chemosensitivity [45], and in the Bcr-Abl-positive chronic myeloid leukemia cell line K562, activin A-induced differentiation sensitized the cells to imatinib treatment [82]. Apart from the K562 cell model, however, the impact of activin A on the response to kinase inhibitors or other targeted cancer therapeutics has remained largely unexplored so far.…”

A novel tubulin polymerization inhibitor, MPT0B206, downregulates Bcr-Abl expression and induces apoptosis in imatinib-sensitive and imatinib-resistant CML cells

“…We used an established method to measure soluble (depolymerized) and assembled (polymerized) tubulin [14]. After treatment, K562 and K562R cells were lysed with 200 ll of a lysis buffer (20 mM Tris-HCl at pH 6.8, 1 mM MgCl 2 , 2 mM EGTA, 1 mM PMSF, 1 mM orthovanadate, 0.5 % NP-40, and 20 lg/ml each of the proteinase inhibitors aprotinin, leupeptin, and pepstatin) and centrifuged at 12,000 9 g for 10 min at 4°C.…”

“…Western blotting was performed after total cell lysates were extracted, as described previously [14]. To detect specific proteins, the following antibodies were used according to the manufacturer's guidelines: a-tubulin and horseradish peroxidase-conjugated secondary antibodies (Sigma); procaspase-9, procaspase-3, cleaved caspase-3, PARP, cyclin B1, phospho-Cdc2, phospho-c-Abl, c-Abl, phospho-AKT, AKT, phospho-MAPK, MAPK, and Bcl-2 (Cell Signaling, Danvers, MA.…”