Bcl-xL is expressed in neuroblastoma cells and modulates chemotherapy-induced apoptosis.
bcl-x is a new member of the bcl-2 gene family and is highly expressed in neural tissues. The present study was designed to determine the expression of the bcl-x gene products in neuroblastoma (NB) and their role in the modulation of chemotherapy-induced apoptosis. Twenty-seven NB cell lines were screened by quantitative immunoprecipitation for Bcl-xL, Bcl-xS, and Bcl-2 expression. None of the cell lines expressed Bcl-xS. Twenty-four of 27 (88%) of the NB cell lines expressed Bcl-xL and 21 of 27 (78%) were positive for Bcl-2. The level of Bcl-xL and Bcl-2 expression was variable among the lines analyzed. Bcl-2 expression was restricted to cells of chromaffin lineage, whereas Bcl-xL was seen in both chromaffin and nonchromaffin lines. To determine whether Bcl-xL could mediate chemotherapy resistance, a NB cell line expressing negligible levels of Bcl-xL was transfected with a bcl-xL expression vector, and unique clones were generated expressing variable levels of Bcl-xL. Cells were treated either with cisplatinum (CP), 4-hydroperoxy-cyclophosphamide (4-HC), or etoposide (VP-16) to induce apoptosis, and cell viability and DNA degradation were determined. Following treatment with CP or 4-HC, Bcl-xL-expressing cells showed significantly increased viability as compared to vector-transfected controls (P < 0.005). Flow cytometric analysis of propidium iodide-stained nuclei following CP or 4-HC treatment revealed significantly increased DNA degradation in controls as compared to Bcl-xL-expressing lines (P < 0.004). DNA analysis by pulsed-field gel electrophoresis revealed high molecular weight (approximately 40 kb) DNA degradation in controls, whereas the DNA in cells expressing Bcl-xL was largely intact. In contrast to CP and 4-HC, results with VP-16 revealed a short-term delay in the onset of apoptosis in Bcl-xL-expressing cells with no long-term survival advantage. The results of these studies indicate Bcl-xL is expressed in NB cells and functions in a manner analogous to Bcl-2 by inhibiting chemotherapy-induced apoptosis.
Dole
M G
MG
Department of Pediatrics, University of Michigan, Ann Arbor 48109-0684, USA.
Jasty
R
R
Cooper
M J
MJ
Thompson
C B
CB
Nuñez
G
G
Castle
V P
VP
D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000633:toxicity; D003520:Cyclophosphamide / Q000031:analogs & derivatives / Q000633:toxicity; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000032:analysis; D005047:Etoposide / Q000633:toxicity; D005434:Flow Cytometry; D006801:Humans; D005810:Multigene Family; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; D004273:DNA, Neoplasm; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D005047:Etoposide; D003520:Cyclophosphamide; D002945:Cisplatin; C011272:perfosfamide