Abundant expression of hTERT in ATL tumor cells. (A) Expression of hTERT mRNA in ATL/HTLV-I infected cell lines (▪), freshly isolated ATL tumor cells from patients (▲), normal PBMCs (○), and CB-CD34⁺ cells (△) were examined by qRT-PCR. The level of hTERT mRNA expression in the K562 leukemia cell line (●) was used as an internal control. The expression level of hTERT mRNA in each sample was calculated relative to that of PBMCs. hTERT mRNA expression relative to normal PBMCs was 21.3 ± 17.9 for the ATL/HTLV-I–infected cell line, 7.48 ± 6.89 for freshly isolated ATL tumor cells, and 1.10 ± 0.12 for CB-CD34⁺ (mean ± standard deviation [SD]). The ATL/HTLV-I–infected cell line and freshly isolated ATL tumor cells expressed hTERT mRNA abundantly and significantly (*P < .01). (B) Expression of hTERT protein in ATL cell lines and normal PBMCs was confirmed by western blotting.