Analysis for loss of heterozygosity (LOH) of p53 allele in tumors derived from p53+/- and CD-1 mice following repeated subcutaneous injections of solutions containing antioxidants

Genomic DNA was isolated From subcutaneous masses observed in CD-1 and p53/- heterozygous mice during the course of carcinogenicity studies in the ve hicle control groups. These masses resulted after daily subcutaneous inject ion of an antioxidant vehicle with a pH adjusted to 3-4. The vehicle was 1. 0% ascorbic acid plus 0.05% sodium metabisulfite in 0.75% saline in a dosin g volume of 10 ml/kg/day. These masses were first palpable after 13 and 37 weeks of dosing among p53+/- and CD-1 mice, respectively. By week 26, the i ncidence of these masses was 89% and 80% in male and Female p53+/- mice, re spectively (n = 15 mice/sex) and was 0% in both male and female CD-1 mice ( n = 60 mice/sex). These masses originated from panniculus carnosus muscle. Histopathological examination of the p53+/- mouse masses indicated the tumo rs to be sarcomas of spindle-cell origin. The histopathological examination of the masses in the CD-1 mice revealed fibrosarcomas. Five mice/sex/strai n were randomly selected from a pool of mice that developed these masses in the course of the two studies. Frozen tissues From these masses were used to examine the DNA for loss of the functional p53 allele in the p53+/- mice (i.e., loss of heterozygosity, or LOH) or For loss of one of the alleles i n the wild type (p53+/+) CD-1 mice by the polymerase chain reaction (PCR) t echnique. loss of the Functional allele was observed only in the tumor from one p53+/- male mouse. These results support a nongenotoxic mechanism for these injection site masses. (C) 2001 Wiley-liss, Inc.