Invariant natural killer T infiltration in neuroblastoma with favorable outcome.

<bold>Background: </bold>Tumor immunity has been suggested to play a key role in clinical and biological behavior of neuroblastomas. Given that CD1-restricted invariant natural killer T (iNKT) cells enhance both innate and acquired tumor immunity, we investigated the expression of the iNKT-cell-specific T-cell receptor Vα24-Jα18 in neuroblastoma tissues and its correlation with clinical and biological characteristics.<bold>Methods: </bold>Using real- time quantitative PCR, we quantified the expression of Vα24-Jα18 in untreated tumor samples from 107 neuroblastoma cases followed in our institution and analyzed the correlation between the presence of infiltrated iNKT cells and clinical characteristics or patients' outcome.<bold>Results: </bold>Vα24-Jα18 receptor was detected in 62 untreated cases (57.9%). The expression was significantly higher in stages 1, 2, 3, or 4S (P = 0.0099), in tumors with low or intermediate risk (P = 0.0050), with high TrkA expression (P = 0.0229), with favorable histology (P = 0.0026), with aneuploidy (P = 0.0348), and in younger patients (P = 0.0036). The overall survival rate was significantly higher in patients with iNKT-cell infiltration (log-rank; P = 0.0089).<bold>Conclusions: </bold>Since tumor-infiltrating iNKT cells were predominantly observed in neuroblastomas undergoing spontaneous differentiation and/or regression, we suggest that iNKT cells might play a key role in these processes. [ABSTRACT FROM AUTHOR]