Favorable prognostic significance of high-level retinoic acid receptor beta expression in neuroblastoma mediated by effects on cell cycle regulation.
We have previously shown that ectopic overexpression of retinoic acid receptor (RAR) subtypes alpha, beta and gamma in human neuroblastoma cells had different effects on growth and retinoid sensitivity. Only overexpressed RAR beta induced profound growth inhibition in the absence of additional retinoid, and increased retinoid sensitivity. In this study, we measured mRNA expression levels of RAR alpha, beta, and gamma in 50 primary neuroblastoma tumor samples, and found a strong correlation between favorable patient prognosis and high-level RAR beta expression. Human neuroblastoma cells transfected with a vector expressing RAR beta demonstrated irreversible growth arrest following a 1 week exposure to all-transretinoic acid, whereas control cells continued to proliferate. In the absence of additional retinoid, RAR beta transfectants demonstrated a higher proportion of cells in the G0/G1 phase of the cell cycle, increased p21WAF1/CIP1 expression and specific binding to a retinoic acid response element. These were changes which we also observed in control neuroblastoma cells following retinoid treatment. Our data indicate that RAR beta is an important factor mediating the growth inhibitory effects of retinoids in neuroblastoma cells. The favorable effect of high-level RAR beta expression on prognosis in primary tumor tissue may occur through RAR beta effects on p21 expression and consequent G0/G1 cell cycle arrest.
Cheung
B
B
Children's Cancer Institute Australia, Sydney Children's Hospital, Randwick, Australia.
Hocker
J E
JE
Smith
S A
SA
Norris
M D
MD
Haber
M
M
Marshall
G M
GM
D002453:Cell Cycle; D002648:Child; D002675:Child, Preschool; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis; D006801:Humans; D007223:Infant; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000175:diagnosis* / Q000401:mortality; D011379:Prognosis; D012333:RNA, Messenger / Q000032:analysis; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology*; D000097768:Retinoic Acid Receptor gamma
D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D011994:Recombinant Proteins; D000072482:Retinoic Acid Receptor alpha; D014212:Tretinoin; D000097768:Retinoic Acid Receptor gamma; C493956:CDKN1A protein, human; C000607071:RARA protein, human; C082925:retinoic acid receptor beta