Molecular evidence of apoptotic death in malignant brain tumors including glioblastoma multiforme: upregulation of calpain and caspase-3.
Cell death in the core of human brain tumors is triggered by hypoxia and lack of nutrients, but the mode of cell death whether necrosis or apoptosis is not clearly defined. To identify the role of apoptosis in brain tumor cell death, we investigated macromolecular (RNA and protein) synthesis and activity in the central to peripheral region of benign [desmoplastic infantile ganglioglioma (DIG) and transitional meningioma (TMG)] and malignant [ependymoma (END), anaplastic astrocytoma (APA), and glioblastoma multiforme (GBM)] brain tumors derived from five patients who had not received previously radiotherapy or chemotherapy. Normal brain tissue (NBT) served as control. RT-PCR analysis of tumor tissues covering central to peripheral regions detected mRNA overexpression of pro-apoptotic gene bax in malignant tumors, indicating a commitment to apoptosis. The mRNA expression of calpain (a Ca(2+)-dependent cysteine protease) and calpastatin (endogenous calpain inhibitor) was altered resulting in an elevated calpain/calpastatin ratio. Calpain content and activity were increased, suggesting a role for calpain in cell death. In the mitochondria-dependent death pathway, caspase-9 and caspase-3 were also overexpressed in tumors. The increased caspase-3 activity cleaved poly(ADP-ribose) polymerase (PARP). Agarose gel electrophoresis detected a mixture of random and internucleosomal DNA fragmentation in malignant brain tumors. Overexpression of pro-apoptotic bax, upregulation of calpain and caspase-3, and occurrence of internucleosomal DNA fragmentation are now presented indicating that one mechanism of cell death in malignant brain tumors is apoptosis, and that enhancement of this process therapeutically may promote decreased tumor growth.
Department of Neurology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Swapan K
SK
Ray
Sunil J
SJ
Patel
Cynthia T
CT
Welsh
Gloria G
GG
Wilford
Edward L
EL
Hogan
Naren L
NL
Banik
D017209:Apoptosis; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002154:Calpain / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D053938:DNA Fragmentation; D004587:Electrophoresis, Agar Gel; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000378:metabolism; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D002135:Calcium-Binding Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; C033668:calpastatin; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D002154:Calpain; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases