Analysis of 3p allelic loss in papillary and nonpapillary renal cell carcinomas - Correlation with tumor karyotypes

Nonpapillary renal cell carcinomas (RCCs) are characterized by deletions of the short arm of chromosome 3 (3p) and papillary RCCs by increased numbers of selected chromosomes. Although recent molecular genetic studies have reported some papillary RCCs to show loss of heterozygosity (LOH) on 3p, a 3p deletion has not been demonstrated in a papillary RCC by karyotype analysis. To investigate this apparent discrepancy between molecular methods and chromosomal changes in the genetic evaluation of RCC, a series of 13 papillary and nonpapillary RCCs was investigated for 3p LOH by PCR-based restriction fragment length polymorphism (PCR-RFLP) analysis and for 3p and 3q LOH by microsatellite analysis. Karyotypes were obtained in six cases. Loss of 3p but not of 3q alleles was found in 8 of 10 nonpapillary RCCs. The region of overlapping deletion was 3p14-p21, and in six cases the deletion involved 3pter loci. One papillary RCC displayed 3p and 3q LOH, but the tumor had two morphologically normal chromosomes 3 and several trisomies. This indicated that nondisjunction of a chromosome from one parent compensated a whole chromosome loss from the other parent during tumor development. LOH in this papillary RCC constituted a reduction of chromosome 3 alleles to homozygosity, but the karyotype change, consisting of an increased number of whole chromosomes and an absence of a structural chromosome 3 abnormality, is regarded as being more characteristic of papillary than nonpapillary RCC.