Induction of apoptosis in a neuroblastoma and hepatocyte coculture model.
BACKGROUND
The dysregulation of apoptosis may alter the progression of tumor growth and explain the clinical dichotomy observed in children with neuroblastoma (NB). An overexpression of the bcl-2 proto-oncogene induces resistance to apoptosis and has been observed in unfavorable NB. We hypothesized that alterations in apoptosis may be a result of the interactions between NB and the tissues surrounding it.


METHODS
Human Chang liver cells (HCL, 10(4) cells/cm2) were plated in two-chamber slides for 3 days. Human NB cells (10(5) cells/cm2) were added to one of the chambers and incubated for 3 more days. Control NB were plated under identical conditions in its own medium and in the HCL medium with growth curves measured. DNA fragmentation was detected via the TUNEL method (TdT-mediated nick end-labeling) and bcl-2 expression was determined by immunostaining.


RESULTS
NB growth was unaltered by the change in medium. NB stained mildly positive for bcl-2 when plated alone but became markedly positive in coculture. Histologically, HCL and NB appeared healthy when plated alone, but a halo of apoptotic HCL was seen around NB in the coculture. When plated alone, both NB and HCL demonstrated minimal apoptotic activity as detected via the TUNEL method. In the coculture, a halo of HCL surrounding the NB exhibited markedly increased DNA fragmentation and this intensity diminished in cells distant from the NB.


CONCLUSIONS
The regulation of apoptosis was altered in this coculture model of NB and HCL. HCL stimulated NB to overexpress bcl-2 and presumably become resistant to apoptosis. Conversely, NB induced the surrounding HCL to undergo apoptosis. The interaction between the local tissue and NB induced alterations in apoptosis in both cell types and resulted in a survival advantage for NB.
Chen
M K
MK
Department of Surgery, University of Medicine and Dentistry of New Jersey, Camden, New Jersey, 08103, USA.
Strande
L
L
Kain
M
M
Whalen
T V
TV
Doolin
E J
EJ
D017209:Apoptosis / Q000502:physiology*; D001710:Biotin; D018929:Cell Culture Techniques / Q000379:methods; D053938:DNA Fragmentation; D003856:Deoxyuracil Nucleotides; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D008099:Liver / Q000166:cytology; D008113:Liver Neoplasms; D009447:Neuroblastoma; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D013194:Staining and Labeling; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000502:physiology
D003856:Deoxyuracil Nucleotides; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D001710:Biotin