Clinical significance of DNA repair genes expressions in neurofibromatosis TYPE 1 cases

Clinical Significance of DNA Repair Genes Expressions in Neurofibromatosis Type 1 Cases Duygu Dursun DEU, Institute of Health Sciences, Oncology Institute, Fundamental Oncology Departure Corresponding Adress: Egitim Quarter/ Ekrem Guer street No:42/5 Murat Oz Apartment Balcova IZMIR/ TURKEY OBJECTIVE: Neurofibromatosis Type 1 (NF1) is a a common autosomal dominant genetic disorder that has a variable phenotype. The genetical causes of clinical variability of NF1 patients is questioned. DNA repair genes are responsible for proofreading the missing in the DNA. We aimed to analyze expression of DNA repair genes and their clinical significance in NF1 patients; comparing exsistance of neurofibroma or hamartomatous lesions or other tumours or existance of NF1 in the family. The other aim of this study was to determine whether any relationship between gene expressions and clinical findings. METHOD: NF1 patients and malignancy with NF1 pateints were included and in this study. In the control gruop children that they are in the similar age group and they have no disease and no malignacy group were included. This study included total 46 cases. 36 NF1 patients (30 children; 6 parents), 8 control cases without any disease, two control cases with rhabdomyosarcoma without NF1 were included in this study. The mean age of control group was 17±7,03 (10-30 age) (median 13 age). In the NF1 pateints gruop 17 of them are female, and 19 are male. The mean age at diagnosis is 10,08±8,86 (9 months- 38 age)(median age 8) for children and 40,50±1,22 (39-42 age) (median age 40) for parents. Among 36 patients, 17 had neurofibromas, 17 had hamartomatous lesions. Rhabdomyosarcoma (RMS) was observed in one patient, breast cancer in one patient and four patients suffered optic glioma. Peripheral blood was obtained from each cases and mononuclear cells were separated. After RNA isolation and cDNA converting, expressions of 84 genes related with DNA Repair in standard array (SABiosciences) were determined by Real-Time PCR for each case. Fold changes and p values compared with control groups and fold changes evaluated with T test and p value in the comperative groups. RESULTS: 36 NF1 patients, 8 healty children as a control and 2 cases no NF1 realtionship with malignancy (rhabdomyosarcoma) were included in the study group. In NF1 cases PNKP, RAD18, XAB2, XRCC3, XRCC4 and XRCC5 genes were downregulated compared with control group. In NF1 cases having neurofibromas, POLB was overexpressed; while ERCC3, LIG1, MGMT, MRE11A, MPG, MSH6, PARP2, PRKDC, RAD51B, RAD52, RPA3, SMUG1, TREX1, UNG were downregulated compared with the NF1 cases without neurofibromas (p<0.05, T test). RAD18 is the downregulated and statistical significant gene for existance of NF1 in the family. There are gene expression fold change differences determined when malign tumor cases with/without NF1 were compared. DDB2, MGMT, MLH1, POLB UNG, XPA are increased. CONCLUSION: Our results may point toward a role of gene expression changes of DNA repair system to be predictive for clinical manifestations in NF1 cases. KEY WORDS: neurofibromatosis type 1, DNA repair genes, clinical relationship