Translator Disclaimer
1 October 2003 Wortmannin-Enhanced X-Ray-Induced Apoptosis of Human T-Cell Leukemia MOLT-4 Cells Possibly through the JNK/SAPK Pathway
Author Affiliations +
Abstract

Tomita, M., Suzuki, N., Matsumoto, Y., Enomoto, A., Yin, H. L., Hosoi, Y., Hirano, K. and Sakai, K. Wortmannin-Enhanced X-Ray-Induced Apoptosis of Human T-Cell Leukemia MOLT-4 Cells Possibly through the JNK/SAPK Pathway. Radiat. Res. 160, 467–477 (2003).

We demonstrated that enhancement of X-ray-induced apoptosis/rapid cell death by wortmannin accompanied by increased activation of JNK/SAPK in human leukemia MOLT-4 cells. Rapid cell death/apoptosis was determined either by the dye exclusion test or by the appearance of Annexin V-positive cells and cleaved PARP fragments. Enhancement was observed only at higher concentrations of wortmannin, i.e. 1 μM or more. At these high concentrations, both DNA-PK and ATM were inhibited. X-ray-induced phosphorylation of Ser 15 of p53/TP53, accumulation of both p53/TP53 and p21/WAF1/CDKN1A, and phosphorylation of XRCC4 were all suppressed. The enhancement of apoptosis/rapid cell death by wortmannin was prevented by addition of caspase inhibitors, Z-VAD-FMK or Ac-DEVD-CHO, or by transfection and overexpression of mouse Bcl2, which is known as an anti-apoptosis protein. The requirement for a high concentration of wortmannin, i.e. 1 μM or more, indicates that inhibition of both DNA-PK and ATM was necessary for the enhanced apoptosis/rapid cell death. Phosphorylation of AKT/PKB was completely suppressed at a much lower concentration, i.e. 0.1 μM wortmannin, where no enhancement of X-ray-induced apoptosis/rapid cell death was observed. On the other hand, X-ray-induced phosphorylation of JNK and its kinase activity as well as apoptosis/rapid cell death were all significantly enhanced only at high concentrations of wortmannin, i.e. 1 μM or more. Furthermore, the extent of enhancement of both JNK phosphorylation and of apoptosis/rapid cell death by wortmannin was less in Rh1a cells, which are ceramide- and radiation-resistant variant cells compared to the parental MOLT-4 cells. Therefore, activation of the JNK pathway was considered important for the enhancement of X-ray-induced apoptosis/rapid cell death of MOLT-4 cells by wortmannin, because of the requirement for a higher concentration of wortmannin than that required for inhibition of AKT phosphorylation. The suppression of the AKT-dependent pathway by wortmannin may have some underlying role in activating the JNK pathway toward the enhancement of cell death in the current system.

Masanori Tomita, Norio Suzuki, Yoshihisa Matsumoto, Atsushi Enomoto, Hong Lan Yin, Yoshio Hosoi, Kazuya Hirano, and Kazuo Sakai "Wortmannin-Enhanced X-Ray-Induced Apoptosis of Human T-Cell Leukemia MOLT-4 Cells Possibly through the JNK/SAPK Pathway," Radiation Research 160(4), 467-477, (1 October 2003). https://doi.org/10.1667/RR3055
Received: 28 December 2001; Accepted: 1 April 2003; Published: 1 October 2003
JOURNAL ARTICLE
11 PAGES


SHARE
ARTICLE IMPACT
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top