Cytogenetic studies of individuals from four kindreds with multiple endocrine neoplasia type II syndrome

Cytogenetics of multiple endocrine neoplasia syndromes

In short-term cultures of tumor tissue from a medullary thyroid carcinoma (MTC), we found a large clone of cells with a balanced translocation t(9;12)(p24;q22). A large clone with a balanced translocation t(10;16)(p11;q24) was also found in cultures from a C-cell thyroid hyperplasia. No clearcut evidence for chromosome instability was observed in the lymphocytes of the two patients. The mother of the first patient died of MTC; two relatives of the second patient had MTC and one of them had pheochromocytoma. These findings classify the two subjects as MEN 2A patients with different phenotypic expression but with the same type of chromosomal abnormality.

Hypodiploid, pseudodiploid, and normal karyotypes prevail in cytogenetic studies of medullary carcinomas of the thyroid and metastatic tissues

Medullary carcinoma of the thyroid (MCT), often a dominantly inherited neoplasm, derived from intrathyroid C-cells of neural crest origin, is one of the solid tumors least studied cytogenetically. The cells are difficult to grow in culture, only two cell lines having ever been established. Cytogenetic studies of only 5 tumors have been reported previously. In this paper we report on the cytogenetic analyses of 8 specimens of primary and/or metastatic MCT tumor tissue from 6 patients with familial disease, including more recent metastatic tumors in lymph node and femur of a patient whose thyroid and earlier lymph node metastases were described previously. Some of these specimens were harvested sequentially over time. Hypodiploid or diploid modal numbers prevailed with normal, pseudodiploid, or hypodiploid karyotypes.

Constitutional chromosome instability and cancer risk

Acquired, clonal chromosome abnormalities are thought to be of pathogenetic importance in human cancer; at the cellular level, neoplasia is best viewed as a genetic disease. It is therefore logical to suggest that cancer risk must somehow be related to individual variations in genomic stability. Those persons whose chromosomes are less stable will, on average, be the ones who are most likely to develop cancer. The testing of this hypothesis shows that, apart from the autosomal recessive chromosome breakage syndromes, only patients with adenomatosis of the colon and rectum have, consistently and by different groups, been found to display elevated spontaneous and clastogen-induced chromosome breakage frequencies. Some evidence indicates a similar tendency in patients with dysplastic nevus syndrome, basal cell carcinoma, cervix cancer, and Kaposi's sarcoma. For several other cancers the data strongly argue against any inherent genomic instability. Although most results thus fail to support constitutional chromosome fragility as a factor of importance in tumorigenesis, conclusive falsification of the hypothesis cannot be said to have been obtained. The possibility remains that variations in chromosome stability and clastogen sensitivity between different cell types, and also difficulties in selecting the most appropriate carcinogens in clastogen-exposure tests, may have masked systematic constitutional differences between patients and controls in the breakage assays.

Analysis of chromosome breakage in the Prader-Labhart-Willi syndrome

Analysis of chromosome breakage with mitomycin C (MMC) and folate-deficient culture conditions was undertaken on 18 Prader-Labhart-Willi syndrome (PLWS) patients (10 with 15q12 deletion [5 females, 5 males; mean age = 17.9 yr, range of 0.3 to 40 yr] and 8 without deletion [2 females, 6 males; mean age = 18.6 yr, range of 7 to 26 yr]), 21 PLWS parents with an average age of 39.2 yr and a range of 25 to 70 yr (12 fathers [8 fathers of PLWS children with the 15q12 deletion and 4 fathers of PLWS children with normal chromosomes] and 9 mothers [4 mothers of PLWS children with the 15q12 deletion and 5 mothers of PLWS children with normal chromosomes]), and age-matched control individuals. There was no difference between PLWS patients and control individuals in the number of chromosome and chromatid aberrations in cells grown at 48 and/or 96 hr in either 20 ng/ml or 50 ng/ml of MMC or between the PLWS parents and control individuals in cells grown in 50 ng/ml MMC for 96 hr, although a small increase (P less than 0.05) in chromosome breakage was found in cells from the total PLWS parental group compared with control individuals exposed for 48 hr in 50 ng/ml MMC. There was also no significant difference in chromosome fragile site frequency in cells grown in folate-deficient culture conditions in PLWS patients, their parents, or controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of age, sex and multiple endocrine neoplasia type-II on silver stained nucleolar organizer regions

Silver stained nucleolar organizer regions (AgNORs) were studied in phytohemagglutinin (PHA)-stimulated lymphocytes from 55 Caucasian control individuals (34 females with average age of 24 years and age range 19 weeks gestation to 87 years; 21 males with average age of 31 years and age range 29 weeks gestation to 72 years) and 13 individuals (7 females, 6 males; average age 38.8 years with age range 25-58 years) with multiple endocrine neoplasia-type II (MEN-II), an autosomal dominant malignancy with increased chromosome breakage. For the first time, AgNORs were examined in lymphocytes from normal fetuses and patients with MEN-II in order to determine the effects of age, sex or malignancy on the number of AgNORs. No significant difference in the average number of AgNORs were found in fetal cells (8.2 +/- S.D. 0.7/cell) when compared with cells from older individuals including those over 65 years of age (8.0 +/- S.D. 0.8/cell). There was a statistically significant negative correlation (P less than 0.05) between the modal number of AgNORs on G but not D chromosomes in both males and females. A negative correlation was also found between the mean number of AgNORs and age but was not statistically significant. The average number of AgNORs in the MEN-II individuals was 8.5 +/- S.D. 0.7/cell, which was not significantly different than 8.2 +/- S.D. 0.7/cell observed in age-matched control subjects.

Frequency and distribution of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced structural chromosome aberrations in fibroblasts from sarcoma and non-Hodgkin's lymphoma patients

The frequency and distribution of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced structural aberrations, i.e., chromatid and chromosome gaps, breaks, and exchanges, were studied in fibroblasts from 16 patients with sarcoma, 15 with non-Hodgkin's lymphoma (NHL), and 14 controls. The mean frequencies of aberrant cells, and gap, break, and gap + break events per 100 cells were 22.9, 5.1, 28.6, and 33.7 in the sarcoma group; 19.1, 5.0, 22.5, and 27.5 in the NHL group; and 23.5, 6.1, 33.5, and 39.6 in the control group. None of the differences between the groups were statistically significant. The distribution of MNNG-induced aberrations was non-random (P less than 0.001) in all 3 groups. Eight, 11, and 17 chromosome bands in the sarcoma, NHL, and control groups, respectively, were particularly break-prone. Only 2 hot spots in the sarcoma group (1p32, 11q23), and 3 in the NHL group (1p36, 3q25, 6p21), coincided with the 25 and 60 bands known to be involved in primary rearrangements in sarcomas and NHL. We conclude that neither the frequency nor the distribution of MNNG-induced chromosomal aberrations indicates any latent chromosomal instability in sarcoma and NHL patients.

Ring chromosome in a patient with MEN IIA S

Three patients with MEN IIA S belonging to the same family, which has five affected subjects in two generations, have been studied. Constitutional karyotype examination identified an extra ring chromosome in 3% of the cells in one of the affected subjects. The number of rings for each cell varied, and different evolutionary aspects of the ring, such as doubling and interlocking, were present. Furthermore, asynchronous DNA replication of doubling rings was observed. This nonhomogeneous, nonrandom chromosome abnormality found in normal tissue of patients with MEN IIA S could be indicative of sensitivity to structural alteration of some chromosome regions.

The map of chromosome 20

The number of gene assignments to human chromosome 20 has increased slowly until recently. Only seven genes and one fragile site were confirmed assignments to chromosome 20 at the Ninth Human Gene Mapping Workshop in September 1987 (HGM9). One fragile site, 13 additional genes, and 10 DNA sequences that identify restriction fragment length polymorphisms (RFLPs), however, were provisionally added to the map at HGM9. Five mutated genes on chromosome 20 have a relation to disease: a mutation in the adenosine deaminase gene results in a deficiency of the enzyme and severe combined immune deficiency; mutations in the gene for the growth hormone releasing factor result in some forms of dwarfism; mutations in the closely linked genes for the hormones arginine vasopressin and oxytocin and their neurophysins are probably responsible for some diabetes insipidus; and mutations in the gene that regulates both alpha-neuraminidase and beta-galactosidase activities determine galactosialidosis. The gene for the prion protein is on chromosome 20; it is related to the infectious agent of kuru, Creutzfeld-Jacob disease, and Gertsmann-Straussler syndrome, although the nature of the relationship is not completely understood. Two genes that code for tyrosine kinases are on the chromosome, SRC1 the proto-oncogene and a gene (HCK) coding for haemopoietic kinase (an src-like kinase), but no direct relation to cancer has been shown for either of these kinases. The significance of non-random loss of chromosome 20 in the malignant diseases non-lymphocytic leukaemia and polycythaemia vera is not understood. Twenty-four additional loci are assigned to the chromosome: five genes that code for binding proteins, one for a light chain of ferritin, genes for three enzymes (inosine triphosphatase, s-adenosylhomocysteine hydrolase, and sterol delta 24-reductase), one for each of a secretory protein and an opiate neuropeptide, a cell surface antigen, two fragile sites, and 10 DNA sequences (one satellite and nine unique) that detect RFLPs.

Fragile sites and high-resolution chromosome studies in multiple endocrine neoplasia type 2A

Affected individuals from four kindreds with multiple endocrine neoplasia type 2A syndrome (MEN-2A), were studied for the possible existence of a specific fragile site that might be associated with the MEN-2A gene. The chromosomes were also examined with high-resolution banding with particular emphasis on those chromosomes (#1, 10, 20, and 22) that have been implicated by previous studies from several laboratories as being associated with this disease. There was no evidence for a unique fragile site or a unique high-resolution banding pattern in subjects with MEN-2A. These findings, in combination with all previous cytogenetic studies, indicate that it is unlikely that current techniques will be useful in developing a simple cytogenetic test for this disease.

Normal frequency of chromosome breakage in lymphocytes from patients with musculoskeletal sarcoma

Spontaneous chromosome aberrations were studied in lymphocytes from 23 untreated patients with musculoskeletal sarcoma and 27 controls. Among the sarcoma patients, the mean gap, break, and gap + break events per 100 metaphases were 0.9, 2.2, and 3.0, respectively. The corresponding values for the control group were 1.3, 1.6, and 2.8. The mean number of aberrant mitoses was 2.4% in the sarcoma group and 2.5% in the controls. None of the differences between patients and controls were statistically significant. Thus, we found no evidence of inherent chromosome instability in patients with malignant mesenchymal tumors.

CHROMOSOME BREAKAGE AND SISTER CHROMATID EXCHANGE ANALYSIS IN COMPUTER OPERATORS

Chromosome breakage analysis with Mitomycin C (MMC) and sister chromatid exchanges (SCE) were obtained on 10 computer operators with computer exposure for a minimum of 3 hours per day for 4 years and 10 control subjects matched for age and personal lifestyle. No difference was found between the two groups in the total number of chromatid and chromosome aberrations in cells grown at 48 and/or 96 hours in Mitomycin C (20 or 50 ng/ml-final concentration). The average number of SCE per cell in approximately 30 cells from each person was 6.4 ± 1.1 (mean ± standard deviation) for the computer operators and 9.2 ± 1.6 for the controls. This difference was significant (p <.001). The replicative index was significantly higher (p<.01) in computer operators than in control subjects. The number of SCE appeared not to be influenced by the years of computer exposure. Additional studies with larger sample sizes will be needed to identify if significant differences exist in cell kinetics and sister chromatid exchanges in individuals employed as computer operators.