Bcl-2 is a key regulator for the retinoic acid-induced apoptotic cell death in neuroblastoma.
Retinoic acid (RA) has been shown to induce neuronal differentiation and/or apoptosis, and is widely used as a chemotherapeutic agent for treating the patients with neuroblastoma. However, the therapeutic effect of RA is still limited. To unveil the molecular mechanism(s) inducing differentiation and apoptosis in neuroblastoma cells, we compared CHP134 and NB-39-nu cell lines, in which all-trans-RA (ATRA) induces apoptosis, with LA-N-5 and RTBM1 cell lines, in which it induces neuronal differentiation. Here, we found that Bcl-2 was strongly downregulated in CHP134 and NB-39-nu cells, whereas it was abundantly expressed in LA-N-5 and RTBM1 cells. ATRA-mediated apoptosis in CHP134 and NB-39-nu cells was associated with a significant activation of caspase-9 and caspase-3 as well as cytoplasmic release of cytochrome c from mitochondria in a p53-independent manner. Enforced expression of Bcl-2 significantly inhibited ATRA-mediated apoptosis in CHP134 cells. In addition, treatment of RTBM1 cells with a Bcl-2 inhibitor, HA14-1, enhanced apoptotic response induced by ATRA. Of note, two out of 10 sporadic neuroblastomas expressed bcl-2 at undetectable levels and underwent cell death in response to ATRA in primary cultures. Thus, our present results suggest that overexpression of Bcl-2 is one of the key mechanisms to give neuroblastoma cells the resistance against ATRA-mediated apoptosis. This may provide a new therapeutic strategy against the ATRA-resistant and aggressive neuroblastomas by combining treatment with ATRA and a Bcl-2 inhibitor.
Division of Biochemistry, Chiba Cancer Center Research Institute, Chuoh-ku, Chiba, Japan.
H
H
Niizuma
Y
Y
Nakamura
T
T
Ozaki
H
H
Nakanishi
M
M
Ohira
E
E
Isogai
H
H
Kageyama
M
M
Imaizumi
A
A
Nakagawara
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001483:Base Sequence; D015153:Blotting, Western; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D005455:Fluorescent Antibody Technique; D006801:Humans; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000473:pathology / Q000503:physiopathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000494:pharmacology*
D019253:Proto-Oncogene Proteins c-bcl-2; D014212:Tretinoin