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Cancer Control Research

Abstract

DESCRIPTION: (Applicant's Description) Radiation and chemotherapy are mutagenic towards germ cells of experimental animals and cause genetic disease in their offspring. However, in humans the assessment of the mutagenic effects of these therapies has been limited by the low frequency of mutations, small numbers of offspring, and limited follow-up of offspring. To overcome such difficulties, genetic changes at the highly mutable DNA repeat loci (mini- and microsatellites) directly in the DNA of individual sperm cells from men exposed to radiation or chemotherapeutic drugs will be measured. Efficient detection of DNA sequence mutations in individual cells is now possible with a novel method called the small-pool polymerase chain reaction (SP-PCR). DNA from up to 100 sperm is amplified at a repeat locus by PCR, separated in one lane by electrophoresis, and analyzed for bands representing individual mutant sperm. Thousands of sperm can be screened in one experiment and mutation frequencies as low as 0.2 percent can be accurately determined. The objective of this pilot study is to test the hypothesis that DNA repeat loci in humans are very sensitive to the induction of repeat number mutations by genotoxic agents. The mutation frequencies in sperm will be measured by SP-PCR. A longitudinal study design will be employed. Semen samples will be obtained from patients after radio or chemotherapy, and the mutation frequencies will be compared with those obtained before treatment. If elevations are observed after therapy, additional samples will be obtained to determine whether there are changes in the mutation frequency with time. The study population includes men with Hodgkin's disease, seminoma, and chronic myelogenous leukemia who receive alkylating or non-alkylating agent chemotherapy or radiotherapy. Mutation analysis will be performed at the mini-satellite M5205, M532, and CEB1 loci and at the microsatellite trinucleotide repeats associated with the myotonic dystrophy and Huntington disease loci and the androgen receptor gene. The results will be used to compare the mutagenic potentials of different cancer treatment regimens and determine whether the mutagenic effects are persistent or decline with time; eventually these data may be used for estimation of mutagenic risks. This information would be extremely valuable in the reproductive counseling of long-term survivors of cancer therapy.