CYCLIN D1 AND ESTROGEN-RECEPTOR MESSENGER-RNA LEVELS ARE POSITIVELY CORRELATED IN PRIMARY BREAST-CANCER

The CCND1 gene, encoding the cell cycle regulatory protein cyclin D1, maps to chromosome 11q13, a locus that is amplified in about 13% of br east cancers, Because several studies have indicated a relationship be tween 11q13 amplification and markers of phenotype including estrogen receptor (ER) status, we tested the relationship between CCND1 and ER gene expression in 364 primary breast cancers using Northern blot anal ysis, Seventy-three % of samples were positive for ER mRNA, and cyclin D1 mRNA levels in the ER-positive group were significantly higher tha n those in the ER-negative group (P = 0.0001), When the samples were d ivided into quartiles of cyclin D1 expression, 58% of samples were ER positive in the lowest quartile and 87% in the highest quartile, The t umors expressing the highest levels of cyclin D1 (7%) were all ER posi tive, Furthermore, ER mRNA levels in the half with lower cyclin D1 mRN A were significantly less than in the half with higher cyclin D1 level s (P = 0.0001), Using simple regression analysis, there was a signific ant positive correlation between cyclin D1 and ER mRNA levels in the t otal population (P = 0.0001), This study demonstrates that cyclin D1 m RNA and ER mRNA are positively correlated in primary breast cancer, bu t the functional relationship between these genes remains to be elucid ated.