Telomerase activity and expression and telomere analysis in situ in the course of treatment of childhood leukemias

Samples of blood and marrow from children with leukemia were assayed for te lomerase activity and expression on the day of diagnosis and during the cou rse of chemotherapy. A strong correlation between either variables and clin ical response was observed in most patients. A unique case was observed in which telomerase activity was only moderately increased on diagnosis; it gr adually increased in the course of therapy, and a subsequent decrease occur red only after application of intensified therapy. This patient did not res pond to therapy, his disease progressed, and he finally died during intensi fied therapy. In another patient, analysis of telomere lengths using dideox y-PRINS revealed a single telomere expansion on a long arm of chromosome 4, suggesting involvement of a telomerase-independent mechanism of telomere e longation. (C) 2000 Academic Press.