PREVALENCE OF ESTROGEN-RECEPTOR VARIANT MESSENGER-RNAS IN HUMAN BREAST-CANCER

A new approach, based on the competitive amplification of wild-type an d exon deleted estrogen receptor (ER) variant cDNAs, was used to scree n 100 human breast tumors for the presence of ER variants. Already des cribed exon 4-deleted ER mRNA was preferentially detected in tumors wi th lower grades (P < 0.05) or higher progesterone receptor levels (P < 0.01), whereas new ER variants, deleted in exons 2-4 or in regions wi thin exons 3-7 were associated with higher grades (P < 0.025) and high er ERs (P < 0.001), This approach allows investigation of the expressi on of multiple ER variant mRNAs and may implicate them as new prognost ic markers and as possible contributors to tumor progression.