hTERT in necessary for cell proliferation. (A) 1301, MyLa, FE-PD, and Hut78 cell line proliferation was determined by a direct cell-counting assay after viral infection for hTERT overexpression (DsRed used as control; solid lines) or for telomerase inhibition: shTERC, shhTERT1, and shhTERT2 vs Scramble (dotted lines). Nonparametric Friedman test *P < .05. (B-C) Expression of hTERT, Ki67, and tubulin were measured by western blot analysis after (B) 10 days of telomerase inhibition or (C) hTERT overexpression. (D) Telomerase inhibition induces senescence markers: p53 and p21 expression levels (relative to EF1α) were determined on 1301 and My-La cell lines by qRT-PCR after 6 days of viral infection. Gene-specific mRNA concentration in cells infected with shTERC or shhTERT1/2 (compared with cells infected with shScramble) was calculated by the 2^–ΔΔCt method.