Allelic loss of chromosome 3p24 correlates with tumor progression rather than with retinoic acid receptor beta 2 expression in breast carcinoma

A tumor suppressor gene, retinoic acid receptor (RAR) beta2, has been mappe d to chromosome 3p24, a region where loss of heterozygosity (LOH) has been observed commonly in carcinomas of various tumor tissues. RAR beta2 express ion is reduced or lost in many malignant tumors including breast cancer, ho wever, whether LOH accounts for the loss of expression of RAR beta2 in brea st cancer is unknown. We, therefore, assessed LOH on chromosome band 3p24 t o correlate it with RAR beta2 expression and other established prognostic p arameters in 52 breast carcinomas. Based on three microsatellites, D3S 1283 , D3S 1293 and D3S 1286, all of the tumors were informative, of these, 12 ( 23%) exhibited LOH. RAR beta2 expression was lost in 42% (19/45) of these s amples. We found that LOH on chromosome band 3p24 was not correlated with l oss of RAR beta2, but correlated with higher histological grade, p53-positi vity, and loss of estrogen and progesterone receptors. Our findings suggest that LOH of the RAR beta2 gene does not account for the frequent loss of R AR beta2 expression in breast cancer but the genomic structural alteration at or close to the RAR beta2 gene locus are likely to be associated with tu mor progression and/or loss of hormonal dependency.