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Allelotype of pancreatic adenocarcinoma using xenograft enrichment
S A Hahn1, A B Seymour, A T Hoque
1Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Abstract:
p53 and MTS1 are known to be mutationally inactivated in pancreatic adenocarcinoma. Other tumor suppressor genes are likely also to play a role. To define chromosomal arms which may harbor additional tumor suppressor genes, we performed an extensive allelotype on pancreatic cancer utilizing a xenograft enrichment technique. Eighty-eight percent (28/32) of primary tumors gave rise to xenografts. Eighteen cases were used in a PCR-based allelotype using 283 polymorphic markers, over 2800 informative assays, and an average coverage of 4.1 informative markers per chromosomal arm per case. Highly frequent allelic loss (> 60%) was seen at chromosomes 1p, 9p, 17p, and 18q. Moderately frequent allelic loss (40-60%) was seen at 3p, 6p, 6q, 8p, 10q, 12q, 13q, 18p, 21q, and 22q. The average fractional allelic loss was 0.36. Allelic and sequence stability was demonstrated among 64 parallel and second-passage xenografts derived from 12 cases of pancreatic adenocarcinoma with the ascertainment of over 3000 single alleles. The findings were confirmed in primary tumors. In only two instances were discrepancies revealed between the allelic loss data obtained from corresponding parallel xenografts, probably due to the xenografting of minor subpopulations, reflecting genetic heterogeneity of the primary tumor.
Insights
This study identified new chromosomal regions in pancreatic cancer that may contain additional tumor suppressor genes. Allelic loss analysis revealed frequent losses on chromosomes 1p, 9p, 17p, and 18q, offering targets for future research.
Area of Science:
- Oncology
- Genetics
- Cancer Research
Background:
- Pancreatic adenocarcinoma frequently involves mutations in tumor suppressor genes like p53 and MTS1.
- The role of other tumor suppressor genes in pancreatic cancer progression remains to be fully elucidated.
Purpose of the Study:
- To identify chromosomal arms potentially harboring novel tumor suppressor genes in pancreatic cancer.
- To perform an extensive allelotype analysis on pancreatic cancer using a xenograft enrichment technique.
Main Methods:
- Utilized a xenograft enrichment technique, successfully generating xenografts from 88% of primary pancreatic tumors.
- Conducted a Polymerase Chain Reaction (PCR)-based allelotype on 18 cases using 283 polymorphic markers.
- Analyzed over 2800 informative assays with an average coverage of 4.1 markers per chromosomal arm per case.
Main Results:
- Identified highly frequent allelic loss (>60%) on chromosomes 1p, 9p, 17p, and 18q.
- Observed moderately frequent allelic loss (40-60%) across several other chromosomal arms, including 3p, 6p, 6q, 8p, 10q, 12q, 13q, 18p, 21q, and 22q.
- Demonstrated allelic and sequence stability in xenografts, confirming findings in primary tumors and highlighting genetic heterogeneity.
Conclusions:
- The study pinpoints specific chromosomal regions with significant allelic loss, suggesting the presence of undiscovered tumor suppressor genes in pancreatic cancer.
- The xenograft enrichment technique proved effective for comprehensive allelotype analysis.
- Findings provide a foundation for further investigation into novel therapeutic targets for pancreatic adenocarcinoma.