Molecular mechanisms of ZD1839 (Iressa)-induced apoptosis in human leukemic U937 cells.
OBJECTIVE
To investigate the molecular mechanisms of ZD1839-induced apoptosis in human leukemic U937 cells.


METHODS
The inhibition of human leukemic U937 cell growth was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphnyl-2H-tetrazolim bromide (MTT) assays, lactate dehydrogenase (LDH) release, and cell cycle distribution. The expression of anti- and pro-apoptotic proteins was detected by Western blot analysis.


RESULTS
This study demonstrated that ZD1839 induced apoptosis in leukemic U937 cells by the downregulation of Bcl-2, caspase activation and subsequent apoptotic features. Cotreatment with ZD1839 and the caspase-3 inhibitor z-DEVD-fmk blocked apoptosis, indicating that caspase-3 activation is at least partially responsible for ZD1839-induced apoptosis. The ectopic expression of Bcl-2 attenuated caspase-3 activation, PARP cleavage, and subsequent indicators of apoptosis, including sub-G1 DNA content and LDH release. These results indicate that the downregulation of Bcl-2 plays a major role in the initiation of ZD1839-induced apoptosis, and that the activation of a caspase cascade is involved in the execution of apoptosis. Furthermore, ZD1839 treatment triggered the activation of p38 mitogen-activated protein kinase (MAPK) and the down-regulation of c-Jun-N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and phosphatidyl inositol 3-kinase (PI3K)/Akt. The inhibition of the ERK and PI3K/Akt pathways also significantly increased cellular death.


CONCLUSIONS
ZD1839 activated caspase-3 and the inhibited Bcl-2 in human leukemic U937 cells through the downregulation of the ERK and PI3K/Akt pathways.
Moon
Dong-oh
DO
Faculty of Applied Marine Science, Cheju National University, Jeju Special Self-Governing Province, Republic of Korea.
Kim
Moon-ok
MO
Lee
Jae-dong
JD
Choi
Yung-hyun
YH
Lee
Min-ki
MK
Kim
Gi-young
GY
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D002867:Chromones / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D000077156:Gefitinib; D006801:Humans; D020935:MAP Kinase Signaling System; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D011799:Quinazolines / Q000494:pharmacology*; D020298:U937 Cells; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000502:physiology
D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D002867:Chromones; D009025:Morpholines; D019253:Proto-Oncogene Proteins c-bcl-2; D011799:Quinazolines; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D000077156:Gefitinib