Telomerase activity in human leukemic cells with or without monosomy 7 or 7q-

In bone marrow material from patients with various leukemias we noted that samples with either a deletion on the long arm of one chromosome 7 (7q-) or a monosomy 7 had a higher telomerase activity. Considering that introduction of a chromosome 7 into a cancer cell line had been reported to eliminate telomerase activity, that 7q- is a common negative prognostic finding in cancers, and that the deleted segment (band 7q31) contains an unidentified tumor suppressor gene, we wondered if this gene might be a telomerase inhibitor.

We found no significant difference in telomerase activity between the three groups of patient samples. In contrast to reports on tumor cell lines we observed no amplification of the telomerase genes.

We analyzed telomerase activity and copy number of the telomerase genes hTERT and hTR in frozen archival bone marrow samples from leukemia patients with a referral diagnosis of AML, and either a monosomy for chromosome 7, a deletion on the long arm of chromosome 7 (7q-), or none of these aberrations. Telomerase activity was measured with a commercially available kit, and the copy number of the telomerase genes was tested by FISH.

We found no evidence of a telomerase inhibitor in band 7q31. The lack of telomerase gene amplification found in cell lines from solid tumors could reflect that this amplification is a property of solid tumors, not of hematological cancers.