Relationship between variant forms of estrogen receptor RNA and an apoptosis-related RNA, TRPM-2, with survival in patients with breast cancer.

Background: Although smaller variant forms of estrogen receptor (ER) messenger RNA (mRNA) have been detected in breast tumors, neither their prevalence nor their prognostic significance have been evaluated. Similarly, TRPM-2 mRNA, the product of a gene induced principally during the onset of apoptosis, is present in mouse and human breast cancer cell lines, but whether it also occurs in primary breast tumors and is related to disease outcome is unknown.

Methods: The relative expression and transcript size of ER mRNA and TRPM-2 mRNA in 126 primary breast tumors were measured by Northern analysis and compared with tumor grade, hormone receptor status, extent of tumor necrosis, and survival.

Results: In ER-positive tumors, 64% of the tumors had only the normal 6.5 kb ER mRNA, an additional 9% had the normal plus smaller ER mRNA, and 2% had variant forms. Only 8% of ER-negative tumors had ER mRNA transcripts. There were significant relationships between the occurrence of ER mRNA and low tumor grade, ER-positive receptor status, and better survival. In contrast, TRPM-2 mRNA was found in only 17% of breast tumors, none of which could be grouped with respect to grade, hormone receptor status, or survival.

Conclusions: The presence of smaller variant forms of ER mRNA either alone or in association with the normal ER transcript is not indicative of an unfavorable prognosis, whereas TRPM-2 mRNA occurs in many primary breast tumors, but has no apparent relationship to survival.