Capture-RT-PCR assay of mRNA in breast tumors:int-2 and HERV-Kenv mRNA

Gene expression at the mRNA level is likely to be a rapidly responding intermediate biomarker for use as a surrogate endpoint in Phase II clinical trials of breast cancer. Using a technology called “capture-RT-PCR,” we have been able to show ectopic int-2 mRNA expression in 7/9 breast tumors, including two fibroadenomas. The level of expression varied, high expression being observed in three tumors. Frequent expression of int-2 in breast tumors is contrary to published reports, possibly reflecting differences in technology. int-2 expression in fibroadenomas suggests that the marker may precede malignancy. Conversely, if fibroadenomas are not premalignant, int-2 expression may be gratuitous. These alternatives need to be tested in a clinical trial. Human endogenous retrovirus K (HERV-K) env gene expression was detected in only 1/7 breast tumors. Expression of this retroviral gene is more restricted than int-2 expression. c-myc was expressed in all 10 tumors studied, albeit at widely varying levels. Expression of prad1 and erbB-2 are under study. Gene expression will be compared with gene amplification. It is anticipated that a capture-RT-PCR assay simultaneously signifying levels of expression of several oncogenes/anti-oncogenes will be a most informative surrogate endpoint biomarker. In particular, chaotropic salt methods that simplify sample preparation and mRNA isolation and reduce these combined steps to a 10 minute procedure will be presented.