Differences of L-myc polymorphic patterns of neuroblastoma in patients under 1 year versus older ages: a preliminary report.

Abstract The age of the patient at the onset of symptoms or at diagnosis is generally accepted as one of the most important prognostic factors of neuroblastomas (NBs). Children less than 1 year of age have a better survival rate than older patients, but the reason for this is unknown. Forty-eight unselected NB patients were divided into two groups: less than 1 year (younger NB patient) and over 1 year (older NB patient) of age at diagnosis. Two of 12 younger NB patients and 18 of 36 older NB patients had N- myc amplification in their tumors. To elucidate further the possible genetic difference between younger and older NB patients, studies of restriction fragment length polymorphism (RFLP) of the L- myc gene was carried out in these two groups. The L- myc locus showed 2-allele polymorphism, allele L(10 kb) and S (6.6 kb), after digestion with EcoRI. Patients homozygous for L-band have been reported as individuals having less metastatic potential in some cancers. The allele frequencies of L and S in neuroblastomas of younger NB patients were 0.50 and 0.50, while those of older NB patients were 0.35 and 0.65, respectively. Although we did not determine L- myc RFLP in normal tissue of individual patients, we expect that the distribution of allele L and S is partly affected by possible allelic loss involving the L- myc region. However, the L- myc RFLP patterns in younger NB patients were the same as those of normal individuals and significantly differed from those of older NB patients. When the loss of heterozygosity was not taken into account, the frequency of S allele in L- myc in NB containing N- myc amplification was higher than in those without amplification. L- myc RFLP did not correlate with either the disease stage or histological types of NB. The present study indicated that NBs in younger NB patients might have some basic, intrinsic differences such as L- myc RFLP pattern from those in older NB patients and also L- myc RFLP may be a useful indicator for prognosis of NB patients.