Allelotypic evaluation of loss of heterozygosity (LOH) has been instrumental in the identification of tumour suppressor genes. Here we report a high incidence of LOH at chromosome 11q23 in non-familial breast cancers with in situ, invasive, and metastatic tumour cells microdissected from archival haematoxylin and eosin (H & E) sections for polymerase chain reaction (PCR)-LOH analysis at polymorphic microsatellite loci. Ninety-four cases of non-familial breast cancer were examined at the D11S29 microsatellite locus on chromosome 11q23. Eighty-three cases (88 per cent) were informative and 35 cases overall (42 per cent) had LOH at this locus, comprising 23 per cent of in situ, 36 per cent of invasive, and 28 per cent of metastatic cancers. The DNA from those cancer cells with LOH was amplified at microsatellite loci D11S554 (11p12-p11.2) and D11S534 (11q13). In 19 of 67 cases overall (28 per cent), LOH occurred solely at 11q23. There was an association between LOH at 11q23 and tumour size > or = 2 cm (P < 0.01) in the overall results and the invasive cancers. The data revealed heterogeneity for LOH at D11S29 in in situ, invasive, and metastatic cells from the same case. In general, however, there was concordance between LOH (or its absence) in in situ and invasive disease. We conclude that the distal part of the long arm of chromosome 11 contains a region involved in breast carcinogenesis and that there is molecular heterogeneity at this chromosomal region in individual breast cancer cells.
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