Abstract A40: Profile of DNA repair status in a recently established panel of patient-derived ovarian carcinoma xenografts
Authors: Guffanti Federica , Fratelli Maddalena , Ganzinelli Monica , Ricci Francesca , Cappelletti Maria Rosa , Generali Damiele , Bizzaro Francesca , Giavazzi Raffaella , Damia Giovanna 
Published: April 2017

Background and Purpose: A xenobank of patient derived (PDX) ovarian tumor samples has recently been established and shown to recapitulate the biological, histological, molecular and pharmacological features of human epithelial ovarian cancer (EOC). This EOC-xenobank consists of tumors with different sensitivity to cisplatin (DDP) from very responsive, responsive to resistant tumors. As DNA repair pathway represents an important driver in tumor response to DDP, we analyzed the mRNA expression of 20 genes involved in Nucleotide Excision Repair (NER), in Fanconi Anemia (FA), in Homologous Recombination (HR), in Base Excision Repair (BER), in Mismatch Repair (MMR) and Translesion Repair (TLR) pathways and the methylation pattern of some of these genes. The correlation with the response to a platinum-based therapy was also investigated.

Methods: The genes selected have a key role in the BER (OGG1 and PARP1); in the NER pathway (ERCC1, XPA, XPF, XPD and XPG); the FA pathway (BRCA1, FANCA, FANCC, FANCD2 and FANCF); in TLR (PolEta), in MMR (MLH1), in MMEJ (PolQ) and in the transcription of some genes (CDK12). The mRNA levels were evaluated by RT-PCR with ad hoc validated primers. The promoter methylation of BRCA1, XPA, ERCC1 and MLH1 was studied by pyrosequencing, while for XPG and FANCF no predesigned assays were available and we evaluated their methylation status following reported assays.

Results: We demonstrated: i) all the DNA genes considered were variably expressed in all the 44 PDX analyzed, with no specific istotype-specific cluster of expression; ii) in high grade seros/endometriod PDXs, the CDK12 mRNA expression levels positively correlated with the expression of TP53BP1, PALB2, XPF and PolB; iii) high grade serous/endometriod PDXs with TP53 mutation had statistically significant higher levels of PolQ, FANC-D2, RAD51 and Pol beta than high grade TP53 wild type PDXs; iv) BRCA1 was found to be hypermethylated in 48% of the xenografts. However, no correlation between mRNA levels and methylation status of the considered CpG islands was found; v) only the mRNA levels of CDK12, PALB2 and XPF inversely correlated with the in vivo DDP antitumor activity.

Conclusions: These data suggest the mRNA expression levels of targeted DNA repair pathway-related genes as PALB2, XPF and CDK12 predict the response to a platinum based therapy in ovarian cancer, even if they need to be prospectively validated in cohort of ovarian cancer patients.

Citation Format: Federica Guffanti, Maddalena Fratelli, Monica Ganzinelli, Francesca Ricci, Maria Rosa Cappelletti, Damiele Generali, Francesca Bizzaro, Raffaella Giavazzi, Giovanna Damia. Profile of DNA repair status in a recently established panel of patient-derived ovarian carcinoma xenografts [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr A40.