Generation and characteristics of RCC23 cells expressing ectopic hTERT (A) Distinct PCR primer design between endogenous and exogenous hTERT genes. Native UTR sequence was shown in gray rectangle. Additional sequences only in exogenous hTERT cDNA were shown in dark rectangle. Solid allow heads, primers for endogenous hTERT. Open allow heads, primers for endogenous hTERT. (B) Detection of ectopic hTERT expression in RCC23-exohTERT cells. RT-PCR was performed with (+) or without (-) reverse transcriptase (RT). endohTERT, endogenous hTERT. exohTERT, exogenous hTERT. (C) Upregulation of telomerase activity in RCC23-exohTERT cells. Enzymatic activity was heat-inactivated for a negative control. (D) Maintenance of exohTERT expression in RCC23-exohTERT cells during long-term culture. RCC23-exohTERT cells were cultured in the presence or absence of hygromycine B (Hyg, drug resistant marker of retroviral vector) until 25 PDs or 50 PDs and RT-PCR was performed for hTERT expression.