Checkpoint effectors CDKN1A and Gadd45 correlate with oxidative DNA damage in human prostate carcinoma

Although cellular oxidative stress is a major cause of DNA damage, it is still not clear to what degree it affects genetic instability and malignant progression in established prostate carcinoma (PCa).

We examined the expression of CDKN1A and Gadd45 proteins acting on cell cycle checkpoints and DNA repair in PCa relative to the presence of oxidative DNA damage, as measured by the detection of the DNA adduct 8-hydroxy-2-deoxyguanosine (8-OHdG.). Sixteen PCa and 28 benign prostate hyperplasias (BPH) were analyzed. RT-PCR was used to evaluate WAF1 and Gadd45 transcripts. Western blot and ELISA were used to analyze proteins and 8-OHdG adducts. Proliferation was studied by Ki67 image cytometry; telomerase activity was detected by TRAP- ELISA.

Multivariate factor analysis provided evidence that, in PCa, DNA checkpoint proteins were associated with 8-OHdG and did not prevent neoplastic cells proliferation. Conversely, in BPH, oxidative DNA damage was inversely correlated with DNA checkpoint proteins and proliferation, suggesting the presence of energy-depleted senescent cells.

Although in non-malignant tissue extensive oxidative DNA damage drives cells to a metabolic blockage, in PCa neoplastic cells it activates repair mechanisms favoring the escape from senescence and the expansion of DNA-damaged clones.