BACKGROUND: Considering previous result in Non-Small Cell Lung Cancer (NSCLC), 
we investigated in human cancer cells the role of PARP3 in the regulation of 
telomerase activity.
METHODS: We selected A549 (lung adenocarcinoma cell line) and Saos-2 
(osteosarcoma cell line), with high and low telomerase activity levels, 
respectively. The first one was transfected using a plasmid construction 
containing a PARP3 sequence, whereas the Saos-2 cells were submitted to shRNA 
transfection to get PARP3 depletion. PARP3 expression on both cell systems was 
evaluated by real-time quantitative PCR and PARP3 protein levels, by 
Western-blot. Telomerase activity was determined by TRAP assay.
RESULTS: In A549 cells, after PARP3 transient transfection, data obtained 
indicated that twenty-four hours after transfection, up to 100-fold increased 
gene expression levels were found in the transfected cells with 
pcDNA/GW-53/PARP3 in comparison to transfected cells with the empty vector. 
Moreover, 48 hours post-transfection, telomerase activity decreased around 33%, 
and around 27%, 96 hours post-transfection. Telomerase activity average ratio 
was 0.67 ± 0.05, and 0.73 ± 0.06, respectively, with significant differences. In 
Saos-2 cells, after shRNA-mediated PARP3 silencing, a 2.3-fold increase in 
telomerase activity was detected in relation to the control.
CONCLUSION: Our data indicated that, at least in some cancer cells, repression 
of PARP3 could be responsible for an increased telomerase activity, this fact 
contributing to telomere maintenance and, therefore, avoiding genome 
instability.