The aim of the present study was to investigate the regulation of Wilms Tumor 1 (WT1) by serine protease high-temperature requirement protein A2 (HtrA2), a member of the Htr family, in K562 cells. In addition, the study aimed to observe the effect of this regulation on cell biological functions and its associated mechanisms. Expression of WT1 and HtrA2 mRNA, and proteins following imatinib and the HtrA2 inhibitor 5‑[5‑(2‑nitrophenyl) furfuryl iodine]‑1, 3‑diphenyl‑2‑thiobarbituric acid (UCF‑101) treatment was detected with reverse transcription‑quantitative polymerase chain reaction and western blot analysis. Subsequent to treatment with drugs and UCF‑101, the proliferative function of K562 cells was detected using MTT assays, and the rate of apoptosis was detected using Annexin V with propidium iodide flow cytometry in K562 cells. The protein levels in the signaling pathway were analyzed using western blotting following treatment with imatinib and UCF‑101. In K562 cells, imatinib treatment activated HtrA2 gene at a transcription level, while the WT1 gene was simultaneously downregulated. Following HtrA2 inhibitor (UCF‑101) treatment, the downregulation of WT1 increased gradually. At the protein level, imatinib induced the increase in HtrA2 protein level and concomitantly downregulated WT1 protein level. Subsequent to HtrA2 inhibition by UCF‑101, the WT1 protein level decreased temporarily, but eventually increased. Imatinib induced apoptosis in K562 cells, but this effect was attenuated by the HtrA2 inhibitor UCF‑101, resulting in the upregulation of the WT1 protein level. However; UCF‑101 did not marke­dly change the proliferation inhibition caused by imatinib. Imatinib activated the p38 mitogen activated protein kinase (p38 MAPK) signaling pathway in K562 cells, and UCF‑101 affected the activation of imatinib in the p38 MAPK signaling pathway. Imatinib inhibited the extracellular signal‑related kinase (ERK1/2) pathway markedly and persistently, but UCF‑101 exhibited no notable effect on the inhibition of the ERK1/2 pathway. HtrA2 and its regulatory effect on WT1 may affect the sensitivity of BCR/ABL(+) cell lines to target therapy drugs through different mechanisms. Regulation of WT1 by HtrA2 occurs in K562 cells, and the regulation may affect the apoptosis of K562 cells under the stress caused by chemotherapeutic treatment. The p38 MAPK signaling pathway, which serves an important role in cell apoptosis, is a downstream pathway of this regulation.

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