Telomerase activity in ductal carcinoma in situ and invasive breast cancer

The increasing number of breast carcinoma in situ detected by screening pro cedures makes it imperative to develop improved markers to stratify the ris k of invasive cancer, Telomerase is detectable in invasive cancer, but not in normal tissues. We have microdissected frozen tissue blocks containing b oth DCIS and invasive cancer to assay the telomerase activity of these two lesions. The 46 available cases of concurrent DCIS and invasive breast canc er resulted in 43 DCIS samples and 38 invasive cancer samples adequate for analysis. Seventy per cent of the DCIS and all invasive cancer samples test ed had detectable telomerase activity. In addition, we analysed telomerase activity in ten cases of DCIS that were not associated with invasive cancer , and detected telomerase activity in seven (70%). Mixing experiments showe d no evidence of telomerase inhibitors in telomerase negative samples. Furt hermore, periductal inflammatory infiltrates were shown to be a potential c onfounding source of telomerase activity. Since DCIS lesions appear to be h eterogeneous with respect to telomerase activity, and telomerase activation appears to precede the development of invasive cancer, telomerase activity may be a useful adjunct in stratifying the risk of developing invasive bre ast cancer in patients with DCIS.