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MINI 35 - Biology (ID 161)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
MINI35.01 - Genetic Alterations in the Fanconi Anemia Pathway in Lung Cancers (ID 2325)
18:30 - 20:00 | Author(s): B. Aguila
The FA pathway contains 17 complementation groups, referred to as FA subtypes A, B, C, D1/BRCA2, D2, E, F, G, I, J, L, M, N, O, P, Q and S. Cells with FA deficiency are hypersensitive to DNA damaging agents such as cisplatin and mitomycin C (MMC). Disruptions of the FA pathway may involve epigenetic silencing of the FA-core complex, mutations or deletion of one or several FA genes. Recently we developed a FA triple-staining immunofluorescence (FATSI) method to detect FANCD2 foci formation using formalin fixed paraffin embedded (FFPE) tumor samples. We screened 139 non-small cell lung cancer (NSCL) FFPE tumors for FANCD2 foci formation by FATSI analysis. Based on the FATSI analysis, 104 of 139 tumor samples were evaluable (lack of Ki67 was defined as non-evaluable samples) for FANCD2 foci status. Among 104 evaluable tumors, 23 (22%) were FANCD2 foci negative. However, further investigation and confirmation of the genetic and epigenetic alterations involved in the FANCD2 foci defective tumors is critical for supporting application of this selection process to justify subsequent clinical treatment strategies for cancer patients.
The aim of the study is to investigate the genetic alterations in the FANCD2 foci defective lung tumors and matching non-tumors. The FANCD2 foci defective tumors were identified with the FATSI method. DNA samples isolated from frozen tumor and matching non-tumor tissues were analyzed with whole exome sequencing. All 17 genes involved in the FA pathway were analyzed.
To investigate the gene involved in disrupting the FA pathway in patient tumors, we applied exome sequencing to 18-paired DNA samples (15 paired foci-negative non-small cell lung tumor and non-tumor frozen tissues, and 3 paired foci-positive non-small cell lung tumor and non-tumor frozen tissues). Among the 15 foci negative tumors, 7 tumors contain 9 somatic mutations including FANCA, FANCC, FANCD2, FANCM, FANCM, FANCP/ SLX4 and FANCS/BRCA1. There was no mutation detected among the three foci positive tumors. Loss of heterozygosity (LOH) events were detected in nine tumors, including one foci positive and eight foci negative tumors. The LOHs occurred in FANCA, FANCD1, FANCD2, FANCM, FANCI, FANCP/SLX4, FANCQ/ERCC4. LOHs on FANCA gene were found in three tumors and LOHs on FANCD2 gene were detected in four tumors including one foci positive tumor.
Based on our preliminary study, 7 of the 15 FANCD2 foci negative lung tumors contained somatic mutation and 8 of the 15 foci negative tumors contained LOHs in the FA genes. A higher frequency of somatic mutation (2 of 7 tumors) and LOHs (3 of 9 tumors) was detected in FANCA gene. In addition, 4 of 9 tumors contained LOHs on FANCD2 indicating the importance of this gene in maintaining FA foci formation. However, we are uncertain if these alterations are functional. Given that FA pathway disruptions may also involve epigenetic silencing of the FA-core complex, plus its collaboration with other proteins, it is necessary to investigate the genetic alteration in the FA associated proteins and promoter methylation status of these genes.
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