Comparison of radiation-induced chromosomal damage between normal individuals and patients with familial polyposis coli

Normal genetic response to gamma irradiation in familial adenomatous polyposis

The present study, a co-operative project between three European institutes, was aimed at elucidating whether the APC gene in carriers of familial adenomatous polyposis coli (FAP) also causes some genetic sensitivity revealed by DNA damage and the yield of chromosome aberrations in peripheral blood lymphocytes exposed to gamma rays. In addition, it seemed of interest to study whether DNA repair is modified after irradiation of lymphocytes from FAP patients compared to controls. To this end, we have used the inhibition of the poly(ADP-ribose) polymerase (ADPRP) by 3-aminobenzamide (3ABA) and studied the effect of 3ABA on the frequency of DNA strand breaks and chromosome aberrations. The data indicate that FAP is not associated with an increased chromosomal sensitivity towards ionising radiation.

Chromosome instability in lymphocytes from patients affected by or genetically predisposed to colorectal cancer

To determine whether there are chromosomal clues to inherited forms of colorectal cancer, we studied chromosome instability in lymphocytes cultured from persons with sporadic colorectal cancer before treatment and from persons with a genetic predisposition to colorectal cancer due to adenomatous polyposis coli, Peutz-Jeghers syndrome, or juvenile polyposis. Spontaneous aberrations of chromosome number and structure were scored and compared to control studies by the same methods. Sex chromosome aneuploidy was found increased in patients. Autosomal aneuploidy was not increased. Chromosome breakage was elevated in young persons genetically predisposed to colorectal cancer compared to young patients with sporadic colorectal cancer. Chromosome rearrangements, other than those of chromosomes 7 and/or 14, rose with age, particularly in patients. Despite considerable interindividual variations, it would seem that increased chromosome breakage and rearrangement in addition to sex chromosome aneuploidy may be signs of chromosome instability in the predisposition to colorectal cancer.

Genotoxic effects of radiotherapy and chemotherapy on the circulating lymphocytes of breast cancer patients. II. Alteration of DNA repair and chromosome radiosensitivity

Lymphocytes from 43 breast cancer patients were tested for their DNA-repair ability and in vitro chromosomal radiosensitivity. Lymphocytes were collected before and after treatment with radiotherapy or chemotherapy or both, and then irradiated in vitro. The aim was to detect alterations of these 2 indicators of radiosensitivity, in relation to cancer status or medical treatment. Patients before treatment were significantly deficient in DNA-repair ability but had a normal chromosomal radiosensitivity as compared to healthy donors. When assessed after treatment, DNA-repair ability and the frequency of in vitro-induced chromosome anomalies were modified according to the type of treatment. A reduced DNA-repair ability was observed for patients after radiotherapy but not after chemotherapy. In vitro-induced dicentrics and acentrics were not modified to the same extent according to the treatment. A decreased number of acentrics (the most frequently observed alteration) was preferentially associated with a more reduced DNA-repair ability. Interindividual differences of response to in vitro irradiation tested by both assays were observed between patients who had undergone similar treatments. The possibility that these assays could be used for predicting individual susceptibility to radiation or chemotherapy drug exposure is discussed.