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We studied loss of heterozygosity (LOH) on chromosome arm 1p in 108 neuroblastomas using 14 polymorphic DNA markers. One-hundred and four tumors with one or more informative loci; 21 (20%) of the 104 tumors showed LOH on 1p, and were classified into three groups on the basis of interstitial or terminal allelic loss, and presence or absence of LOH on 1p. Seven of the 21 tumors showed an interstitial deletion which encompassed a small region in 1p36 (group A), and the other 14 showed a terminal deletion which encompassed the region from 1pter to 1p32 (group B). Eighty-three tumors without LOH on 1p were classified as group C. The group A patients were mostly less than 12 months of age (6/7), were frequently found by a mass screening program for infants (5/7), had a tumor of non-adrenal origin, and rarely progressed to stage IV (1/7). Most group B patients were 12 months or older (11/14), were found clinically (11/14), had tumors of adrenal origin, and progressed to stage IV (10/14). Analysis of biologic characteristics in group C tumors suggested that they may comprise group A and B tumors. While all group A tumors were in the triploid range (3n) (4/4), most group B tumors were diploid (2n) or tetraploid (4n) (7/10). MYCN amplification was found in 8 group B tumors, but in none of group A tumors. Event-free survivals of groups A, B, and C patients at 3 years were 86, 49, and 74%, respectively (P = 0.0287). These findings suggest that there may be two tumor suppressor genes on 1p which are closely associated with two biologically distinct subtypes of neuroblastoma.

Recombinant phages that carry the human smooth muscle (enteric type) -y-actin gene were isolated from human genomic DNA libraries. The amino acid sequence deduced from the nucleotide sequence matches those of cDNAs but differs from the protein sequence previously reported at one amino acid position, codon 359. The gene containing one 5' untranslated exon and eight coding exons extends for 27 kb on human chromosome 2. The intron between codons 84 and 85 (site 3) is unique to the two smooth muscle actin genes. In the 5' flanking region, there are several CArG boxes and E boxes, which are regulatory elements in some muscle-specific genes. Hybridization with the 3' untranslated region, which is specific for the human smooth muscle -y-actin gene, suggests the single gene in the human genome and specific expressions in enteric and aortic tissues. From characterized molecular structures of the six human actin isoform genes, we propose a hypothesis of evolutionary pathway of the actin gene family. A presumed ancestral actin gene had introns at at least sites 1, 2, and 4 through 8. Cytoplasmic actin genes may have directly evolved from it through loss of introns at sites 5 and 6. However, through duplication of the ancestral actin gene with substitutions of many amino acids, a prototype of muscle actin genes had been created. Subsequently, striated muscle actin and smooth muscle actin genes may have evolved from this prototype by loss of an intron at site 4 and acquisition of a new intron at site 3, respectively.

Background. Telomeric deletions contribute to genetic instability and may represent an important mechanism of carcinogenesis. Amplification of the c‐erbB‐2 gene has been demonstrated in breast carcinoma. The clinical significance of telomeric deletions and c‐erbB‐2 gene amplification therefore was studied in patients with breast disorders. Methods. The Southern blot analysis was used to measure telomeric length as well as the c‐erbB‐2 gene amplification of breast carcinomas, adjacent normal breast tissues, fibroadenomas, and cases of gynecomastia. Results. Significant reductions in telomeric length and concentration were observed in all breast tissues when compared to placental DNA. Mean telomeric lengths were lowest in carcinomas and fibroadenomas. There were no significant differences, however, in the telomeric lengths among tissues from patients with breast carcinomas, fibroadenomas, or gynecomastia. The degree of telomeric deletion correlated significantly with histologic grade and was most notable in Grade 3 (scirrhous) breast carcinoma. The extent of telomeric deletion reflects the histologic aggressiveness of breast carcinoma, and telomeric reduction already can be seen in the adjacent normal breast tissues from patients with breast cancer. c‐erbB‐2 gene amplification was observed in 26.8% of the patients with breast carcinoma. c‐erbB‐2 gene amplification was not observed, however, in patients with fibroadenomas or gynecomastia. The degree of telomeric deletion did not correlate with c‐erbB‐2 gene amplification, tumor size, clinical stage, steroid receptors, or prognosis. Telomeric length was shorter in lymph node‐negative tumors than in lymph node‐positive tumors. Conclusions. These findings indicate that a shorter telomere length reflects growth advantage in breast cancer tissue, and telomeric reduction may promote cancer progression. Cancer 1994; 73:2978–84.

The relationship between cytogenetic findings and prognosis in 51 pediatric patients with neuroblastoma is described. Patients were classified into the following four groups based on karyotypic findings: (1) near diploidy, 42 to 47 chromosomes (n = 11); (2) hyperdiploidy, 50 to 56 chromosomes (n = 4); (3) near triploidy, 60 to 77 chromosomes (n = 33); and (4) hypotetraploidy, 80 to 83 chromosomes (n = 3). Patients with near diploid or hypotetraploid karyotypes also had several structural abnormalities including marker chromosome 1, with or without double minutes (DM) or homogeneously staining regions (HSR). Most of these patients were 1 year of age or older and had advanced tumors. The patients who were in the hyperdiploid or near triploid category had few structural abnormalities; all of them, except one, were younger than 1 year of age, had localized tumors, and are long-term, disease-free survivors. Kaplan-Meier analysis of survival rates disclosed a significant difference favoring the latter group (P < 0.001).

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The partial nucleotide sequence encoding the rod portion of the entire amino acid sequence of human smooth muscle myosin heavy chain (MHC) which corresponds to MYH11, according to Human Gene Mapping nomenclature, has been determined by cloning a complementary DNA (cDNA) and sequencing the cDNA (UMYHSM). Northern blot analysis with the UMYHSM fragment (4.3 Kb) showed that the smooth muscle MHC of the human umbilical artery is expressed in the human umbilical artery, bladder, esophagus and trachea. Southern blot analysis of human genomic DNA from human-mouse or human-Chinese hamster somatic cell hybrids demonstrated that the human smooth muscle MHC was mapped to human chromosome 16. Regional mapping of UMYHSM was performed using human cell lines with partial deletion and trisomy of chromosome 16. As a result, the human smooth muscle MHC gene segregated with 16p11-q12. In situ hybridization of biotin-labeled human smooth muscle MHC probe (UMYHSM fragment) to normal human metaphase chromosome independently showed that the human smooth muscle MHC gene (MYH11) is assigned to chromosome region 16q12. Analysis of early metaphase chromosomes showed that hybridization signals were in 16q12.1. In the human, although skeletal, cardiac, smooth muscle, and nonmuscle MHC genes are mapped to chromosomes 17, 14, 16, and 22, respectively, structural similarities of these MHC genes strongly suggest the common origin of these genes.

We studied 96 infants and children with untreated neuroblastomas. Chromosomes of tumor cells were analyzed in 68, and N-myc copy numbers were determined in 67 patients. Patients found by a mass screening program for 6-month-old infants (group A1, 39 patients) or those less than 12 months of age found clinically (group A2, 13 patients) were rarely in the disseminated stage (A1, three of 39; A2 one of 13); their tumors usually had near-triploid (3n) or hypertetraploid (greater than 4n) karyotypes (A1, 28 of 37; A2, nine of 11), and never had N-myc amplification (A1, zero of 34; A2, zero of 11). In contrast, children 12 months or over (group B, 27 patients) were usually in the disseminated stage (19 of 27) (P less than .0001); their tumors usually had near-diploid (2n) or near-tetraploid (4n) karyotypes (16 of 20) (P = .0027), and often had N-myc amplification (nine of 22) (P less than .0001). Of the 40 clinically found patients (A2 and B), six had undergone the screening with a negative result at the age of 6 months. Two of the six patients had N-myc amplification in the tumors. Most tumors found by the screening showed known characteristics predicting a good prognosis, and the majority of tumors showing characteristics predicting a poor prognosis were found in patients aged between 12 and 36 months. Our chromosome and N-myc amplification studies suggest that a low-risk tumor does not usually evolve to a high-risk tumor. Thus, the current mass screening program may be detecting only a small portion of highly malignant neuroblastomas at the earliest stage. Infants should be screened twice, at 6 months as well as at 12 months of age, for the early detection of high-risk neuroblastomas.