Interstitial deletion of the short arm of chromosome 3 as a primary chromosome abnormality in carcinomas of the breast

Physical map of small cell lung cancer deletion region on short arm of human chromosome 3 (3p13-22) based on radiation fusion hybrid analysis

Deletion of DNA sequences from various regions of the short arm of human chromosome 3 (3p13-14, 3p21, and 3p25) has been observed during the development of a variety of solid tumors, including lung and renal cell carcinomas. In this study we have used a set of radiation fusion hybrids to generate a physical map of chromosome 3p to orient the search for putative tumor suppressor genes. Eighty-six human-hamster radiation fusion hybrids were screened on Southern blots for the retention of 55 human chromosome 3p DNA markers. The high marker density enabled us to identify a set of successively overlapping chromosome fragments in the 3p13-22 area guided by eight markers with previously known order. Twenty-four map intervals were suggested using breakpoints determined by partial fragment overlaps. The final order between the markers derived is consistent with previous information about localizations for 26 of the markers to three larger cytogenetic intervals.

Chromosomal aneuploidy in proliferative breast disease

Although some forms of proliferative breast disease have been associated with increased risk of breast cancer, substantial confirmatory evidence that the lesions are biologically premalignant has not been presented. Our intent was to identify cytogenetic aberrations in proliferative breast disease using fluorescence in situ hybridization probes selected for their relationship to aberrations previously reported in breast cancer. Application of fluorescence in situ hybridization techniques to paraffin tissue sections using pericentromeric probes for chromosomes 1, 16, 17, 18, and X revealed chromosome aneuploidy in proliferative and malignant lesions of the breast. Sectioning artifact that may result in nuclear truncation was controlled by establishing expected baseline frequencies for gain and loss in normal tissues from the same breast. Localization of chromosomal aberrations to proliferative breast disease lesions with concomitant retention of a normal chromosome complement in corresponding normal breast tissues indicates biologic significance of the results. The similarities of losses involving chromosomes 16, 17, and 18 in hyperplastic lesions and in malignant breast lesions suggest that some hyperplasias may be part of a sequence of progression to malignancy in breast cancer. Gains of chromosome 1 in both in situ and invasive carcinoma are consistent with reports of polysomy 1q as a common cytogenetic change in breast cancer. Its localization to advanced lesions suggests that this trisomy is probably not the initial cytogenetic change in breast cancer tumorigenesis.

Molecular biology of breast cancer

BACKGROUND

A gene responsible for an inherited predisposition to breast and ovarian cancer has been localized to the long arm of chromosome 17 and termed BRCA1. As well as being closely linked to breast/ovarian cancer cases, this gene may be involved in up to 45% of site-specific breast cancers. The identification and cloning of the BRCA1 gene is imminent, and will facilitate the screening and counselling of families at risk of breast cancer, and in the longer term may open up new therapeutic possibilities. The tumour suppressor gene TP53 is mutated in 25%-40% of cases of sporadic breast cancer, and is associated with an aggressive tumour phenotype and poor prognosis in both node-positive and node-negative cases. The pattern of mutations in this tumour suppressor gene shows a higher than expected frequency of G to T transversions, mostly restricted to the highly conserved domain in exons 5 to 8. In many, but not all cases, point mutation of one allele is accompanied by deletion of the remaining normal allele at chromosome 17p13. Abnormalities of TP53 appear to be relatively early events in tumorigenesis, being present in ductal carcinoma in situ lesions. The retinoblastoma gene RB1 shows a variety of abnormalities in about 20% of breast cancers, and there may be an association with TP53 mutations. Other abnormalities which occur with a particularly high incidence in breast cancer include allele loss at chromosome 1p/1q, 3p, 6q, 11p, 16q and 18q. The ERBB2 oncogene encodes a transmembrane receptor tyrosine kinase whose ligand has recently been claimed to be the heregulin family in man.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosome abnormalities in oral squamous cell carcinomas

Strong evidence in favour of the somatic mutation theory of cancer, which states that genomic rearrangements are early and essential events in tumour development, has during the past two decades been obtained from both cytogenetic and molecular genetic studies of neoplastic cells. More than 14,000 neoplasms with acquired clonal chromosome aberrations have been reported; the majority have, however, been haematological malignancies, whereas still little is known about the karyology of the quantitatively more important carcinomas. For oral squamous cell carcinomas (SCC), which constitute a substantial subset of human malignancies, only 63 short-term cultured tumours with karyotypic aberrations have been described. Simple numerical changes, mostly -Y, +Y, or +7, have been detected as the sole anomalies in 19 tumours, but these aberrations are probably not causally related to the neoplastic process. The remaining 44 SCC have had structural changes of varying complexity, often together with numerical aberrations. An assessment of the karyotypic imbalances resulting from these aberrations reveals that chromosomes 9, 13, 18 and Y are recurrently lost, and that deletions frequently involve chromosome arms 3p, 7q, 8p, 11q, 17p and the short arms of all acrocentric chromosomes. The chromosomal breakpoints in structural rearrangements frequently involve the centromeric regions of chromosomes 1, 3, 8, 14 and 15 as well as bands 1p22, 11q13 and 19p13. At least one of these bands has been rearranged in 70% of SCC with structural aberrations and they probably contain loci of importance in oral squamous cell carcinogenesis. A comparison of data obtained from oral and other types of SCC--laryngeal, oesophageal, lung, cervical, and anal canal--indicates that some of the events in the multistep process of SCC development involve the same genetic pathways irrespective of site of origin.