Identifying Susceptibility Genes for Familial Pancreatic Cancer Using Novel High-resolution Genome Interrogation Platforms

• Main Author: Al-Sukhni, Wigdan
• Other Authors: Gallinger, Steven
• Language: en_ca
• Published: 2012
• Subjects: familial pancreatic cancer; tumor suppressor genes; oncogenes; copy number variation; exome sequencing; 0369; 0564
• Online Access: http://hdl.handle.net/1807/33905

Familial Pancreatic Cancer (FPC) is a cancer syndrome characterized by clustering of pancreatic cancer in families, but most FPC cases do not have a known genetic etiology. Understanding genetic predisposition to pancreatic cancer is important for improving screening as well as treatment. The central aim of this thesis is to identify candidate susceptibility genes for FPC, and I used three approaches of increasing resolution. First, based on a candidate-gene approach, I hypothesized that BRCA1 is inactivated by loss-of-heterozygosity in pancreatic adenocarcinoma of germline mutation carriers. I demonstrated that 5/7 pancreatic tumors from BRCA1-mutation carriers show LOH, compared to only 1/9 sporadic tumors, suggesting that BRCA1 inactivation is involved in tumorigenesis in germline mutation carriers. Second, I hypothesized that the germline genomes of FPC subjects differ in copy-number profile from healthy genomes, and that regions affected by rare deletions or duplications in FPC subjects overlap candidate tumor-suppressors or oncogenes. I found no significant difference in the global copy-number profile of FPC and control genomes, but I identified 93 copy-number variable genomic regions unique to FPC subjects, overlapping 88 genes of which several have functional roles in cancer development. I investigated one duplication to sequence the breakpoints, but I found that this duplication did not segregate with disease in the affected family. Third, I hypothesized that in a family with multiple pancreatic cancer patients, genes containing rare variants shared by the affected members constitute susceptibility genes. Using next-generation sequencing to capture most bases in coding regions of the genome, I interrogated the germline exome of three relatives who died of pancreatic cancer and a relative who is healthy at advanced age. I identified a short-list of nine candidate genes with unreported mutations shared by the three affected relatives and absent in the unaffected relative, of which a few had functional relevance to tumorigenesis. I performed Sanger sequencing to screen an unrelated cohort of approximately 70 FPC patients for mutations in the top two candidate genes, but I found no additional rare variants in those genes. In conclusion, I present a list of candidate FPC susceptibility genes for further validation and investigation in future studies.