Over-expression of hTERT in CHO K1 results in decreased apoptosis and reduced serum dependency.
The enzyme telomerase plays a crucial role in cellular proliferation. By adding hexameric repeats to the chromosome ends, it prevents telomeric loss and, thus entry into senescence of limited life span cells. It is unclear, however, what would be the effect of over-expressing telomerase in an immortalised cell line, characterised by unlimited life span and high levels of apoptosis under sub-optimal growth conditions. In order to address this question, we have transfected the immortal cell line CHO K1 with the human telomerase reverse transcriptase (hTERT) catalytic subunit. Differences in the growth profile and apoptosis levels between the cells over-expressing hTERT (Telo) and the cells containing mock vector were found under standard growth conditions. Similarly, the Telo cells showed lower levels of apoptosis, greater attachment tendency and higher viable cell density under serum-deprived conditions compared to the control cell line, suggesting a major role for hTERT over-expression in stressed cultures. Using a mouse cDNA microarray, the collagen type III and V genes were shown to have at least a 10-fold higher expression in the Telo cells than the control cells, suggesting a role of hTERT in the cell attachment pathways.