Abstract 778: DNA repair capacity, chromosomal damage, methylation and gene expression levels in bladder cancer: An integrated analysis
Authors: Matullo Giuseppe , Viberti Clara , Pardini Barbara , Allione Alessandra , Guarrera Simonetta , Turinetto Valentina , Giachino Claudia , Fiorito Giovanni , Naccarati Alessio , Russo Alessia , Critelli Rossana , Destefanis Paolo , Oderda Marco , Gontero Paolo , Vineis Paolo , Sacerdote Carlotta 
Published: July 2016

Bladder cancer (BC) is the sixth most commonly diagnosed tumor worldwide. DNA repair capacity (DRC) refers to the ability of a cell to protect the integrity of the genome and DNA repair pathways have been implicated in BC risk. It has been observed that individuals with low DRC tend to accumulate more damage than those with a more efficient DRC. This inter-individual variability is modulated by the genetic background, as well as differential gene expression and epigenetic regulation.

We aimed at studying the relationship between DRC and DNA damage (evaluated by H2AX phosphorylation and micronucleus assays) and BC risk and clinical outcome, integrating with gene expression and epigenetic profile data in 159 BC cases and 159 matched controls, enrolled in the Turin Bladder Cancer Study (TBCS).

We investigated ã-H2AX phosphorylation levels and MN frequencies in cryopreserved peripheral blood mononuclear cells. We found significant differences in micronuclei and nuclear buds frequencies, with higher number of these damages in cases compared to controls (p = 0.0002 and p = 0.002 respectively).

On the other hand, we observed a significant association between ã-H2AX basal levels and risk of disease recurrence/progression in both BC patients as a whole and the subgroup of non-muscle invasive BC (NMIBC) (for all BC HR 0.70, 95% CI 0.52-0.94, p = 0.02; for NMIBC HR 0.68, 95% CI 0.50-0.92, p = 0.01): this suggests a protective effect of DNA double strand breaks signalling in terms of preventing BC recurrence or progression.

In order to evaluate the genetic and epigenetic role in modulation of DRC we performed whole genome methylation and gene expression analyses on the same BC cases and controls. Preliminary analyses on methylation levels did not show any significant difference between cases and controls. Two metalloproteinases (MMP23A and MMP23B) resulted significantly under-expressed in BC compared to healthy controls (logFC = -0.23, p = 0.01; logFC = -0.37, p = 0.007, respectively). Interestingly, the expression levels of these genes were also significantly correlated with the relative CpGs methylation.

Further analyses focusing on the integration of whole genome data with DRC assays are ongoing to unravel new prognostic biomarkers of disease.

Citation Format: Giuseppe Matullo, Clara Viberti, Barbara Pardini, Alessandra Allione, Simonetta Guarrera, Valentina Turinetto, Claudia Giachino, Giovanni Fiorito, Alessio Naccarati, Alessia Russo, Rossana Critelli, Paolo Destefanis, Marco Oderda, Paolo Gontero, Paolo Vineis, Carlotta Sacerdote. DNA repair capacity, chromosomal damage, methylation and gene expression levels in bladder cancer: An integrated analysis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 778.