No abstract

Dysfunctional homologous recombination DNA repair (HRR), frequently due to BRCA mutations, is a determinant of sensitivity to platinum chemotherapy and poly(ADP-ribose) polymerase inhibitors (PARPi). In cultures of ovarian cancer cells, we have previously shown that HRR function, based upon RAD51 foci quantification, correlated with growth inhibition ex vivo induced by rucaparib (a PARPi) and 12-month survival following platinum chemotherapy. The aim of this study was to determine the feasibility of measuring HRR dysfunction (HRD) in other tumours, in order to estimate the frequency and hence wider potential of PARPi. A total of 24 cultures were established from ascites sampled from 27 patients with colorectal, upper gastrointestinal, pancreatic, hepatobiliary, breast, mesothelioma, and non-epithelial ovarian cancers; 8 were HRD. Cell growth following continuous exposure to 10 μM of rucaparib was lower in HRD cultures compared to HRR-competent (HRC) cultures. Overall survival in the 10 patients who received platinum-based therapy was marginally higher in the 3 with HRD ascites (median overall survival of 17 months, range 10 to 90) compared to the 7 patients with HRC ascites (nine months, range 1 to 55). HRR functional assessment in primary cultures, from several tumour types, revealed that a third are HRD, justifying the further exploration of PARPi therapy in a broader range of tumours.

IntroductionNeuroblastoma originates from neural crest cells which go on to form the sympathetic nervous system and is the most common extra-cranial solid tumor in children. One of the clinical hallmarks of neuroblastoma is heterogeneity, varying from highly aggressive chemoresistant disease to spontaneous regression in infants. 1 Despite advances in the treatment of other childhood cancers, high-risk neuroblastoma remains one of the most difficult cancers to cure with long-term survival still less than 40%.p53 is an important tumor suppressor gene, frequently referred to as the 'guardian of the genome,' exerting an important role in preventing the replication of cells with DNA damage. p53 has evolved the ability to integrate distinct environmental signals, including DNA damage and cytokine signaling which mediate phosphorylation of p53 at key sites in the N-terminal transactivation domain at serine 15 and 20 (reviewed in refs. 2 and 3). In response, p53 levels are rapidly upregulated and activate transcription of a large number of downstream genes including p21, a cyclin-dependent kinase inhibitor that binds Cdk-cyclin Background: MYCN oncogene amplification occurs in 20-25% of neuroblastomas and is associated with a poor prognosis. We previously reported that MYCN amplified (MNA) p53 wild-type neuroblastoma cell lines failed to G 1 arrest in response to irradiation, but this could not be attributed to MYCN alone.Hypothesis: Genes co-amplified with MYCN and/or the predominant cell type, neuronal (N) or substrate adherent (S) phenotypes determine the downstream response to DNA damage in neuroblastoma cell lines.results: No genes with a potential role in cell cycle regulation were consistently co-amplified in the MNA cell lines studied. High MYCN expressing NBLW-N cells failed to G 1 arrest following irradiation and showed impaired induction of p21 and MDM2, whereas low MYCN expressing NBLW-S cells underwent a G 1 arrest with induction of p21 and MDM2. Conversely N-type cells underwent higher levels of apoptosis than S-type cells. Following p53 knockdown in SHSY5Y Ntype cells there was a decrease in apoptosis.Methods: the MYCN amplicons of five MNA and two non-MNA cell line were mapped using 50K Single Nucleotide Polymorphism (SNP) arrays. one MNA (NBL-W) and one non-MNA neuroblastoma cell line (SKNSH) were sub-cloned into N and S-type cells and the p53 pathway investigated after irradiation induced DNA damage. to determine the role of p53 it was knocked down using sirNA.Conclusions: the downstream response to DNA damage in p53 wild-type neuroblastoma cell lines is p53-dependent, and determined both by the morphological subtype and MYCN expression.