Second Neoplasms After Childhood Cancer And Gene Expression Differences In Primary Fibroblasts

Treatment of the primary neoplasm with radiotherapy or chemotherapy is an established risk factor for second neoplasms (SNs) after childhood cancer. As only a small percentage of the treated children suffer from SN, other shared risk factors must be involved. A predisposition for the occurrence of a SN might be a pre-existing somatic genetic defect associated with DNA repair. We investigated the association between gene expression involved in DNA-repair and the development of SNs after childhood cancer. Designed as a feasibility study this project addressed the possibility of obtaining samples for genetic analyses from former patients through the German Childhood Cancer Registry. We recruited 20 patients with two neoplasms (the first occurring in childhood) and 20 matched patients with one neoplasm in childhood. Matching was by first neoplasm, age and year of first diagnosis. Registered SN were confirmed to be no relapses or alternative manifestations of the primary neoplasm. Participants were not given financial rewards (except travel expense compensation). Genetic counselling was offered independently of consent to skin biopsy. We compared the DNA repair gene expression in cultivated untreated primary fibroblasts of both patients groups using customized cDNA microarrays (800 genes). For each sample of each subject, trimmed means of the log-ratios were calculated for comparison between the matched samples with paired sample t-tests, regarding the normalized gene expression values (print-tip loess with variance stabilization normalization and quantile normalization with the R package Arraymagic). We used false discovery rate control by explorative Simes procedure to account for multiple testing. Additionally, we used hierarchical cluster analysis (complete linkage and two way clustering) to analyse whether subjects group into the two groups using the 40 sequences with lowest p-values in the paired-sample t-tests. We validated the results for five selected genes by real-time PCR. Overall, 46% of the 52 contacted SN and 18 % of the 132 single neoplasm patients participated in the study. The DNA-repair gene results showed small differences in the basal gene expression of FTH1 and CDKN1A. As the study subjects were very heterogeneous regarding their first and second neoplasms, we performed two subgroup analyses in the most common groups: Subjects with lymphoid leukaemia as a fist neoplasm (n=10) and subjects with thyroid carcinoma as second neoplasm (n=6). FTH1 displayed a small p-value in both subgroups, CDKN1A in the lymphoid leukaemia sample only. To our knowledge, this is the first study using gene expression arrays in untreated primary fibroblasts regarding second neoplasms after a childhood neoplasm. We were able to recruit childhood cancer patients for genetic analyses long after diagnosis. The biological importance of the differences in the DNA-repair gene expression has to be elucidated yet. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5504. doi:1538-7445.AM2012-5504