High prevalence of BRCA1 and BRCA2 germline mutations with loss of heterozygosity in a series of resected pancreatic adenocarcinoma and other neoplastic lesions

Abstract

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is associated with the breast ovarian cancer syndrome (BRCA1/BRCA2) mutations. It is unknown if this association is causal.

Experimental design: This is a single-site study of patients who underwent surgical pancreatic tumor resection and self-identified as Ashkenazi Jewish. DNA from normal pancreatic tissue was genotyped for the three Ashkenazi Jewish BRCA1/2 founder mutations BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT, and loss of heterozygosity (LOH) was determined by sequencing DNA from microdissected tumor. When additional tumor tissue was available, p53 immunohistochemistry (IHC) was conducted.

Results: Thirty-seven patients underwent surgery for PDAC, seven for intraductal papillary mucinous neoplasm (IPMN), and 19 for other diseases. A high prevalence of BRCA1/2 mutations was found in the surgical cohort (12/63; 19.0%; P < 0.001), PDAC cohort (8/37; 21.6%; P < 0.001), and IPMN cohort (2/7; 28.6%; P = .01) compared with published control mutation frequency. A high prevalence of BRCA1 185delAG (8.1%; P < 0.001) and BRCA2 6174delT (10.8%; P < 0.001) in Ashkenazi Jewish patients with PDAC was shown. BRCA1/2 LOH was found in 2 of 4 BRCA1-associated PDACs and 3 of 4 BRCA2-associated PDACs. Positive p53 IHC was found in 5 of 8 BRCA1/2 PDACs.

Conclusions: We show a high prevalence of BRCA1/2 mutations with LOH in an Ashkenazi Jewish cohort of surgically resected PDAC and neoplastic lesions, suggesting that these germline mutations are causal in selected individuals.

Figure 1

BRCA1 185delAG LOH. A, chromatogram showing the wild-type sequence of BRCA1 gene at region of 185delAG deletion. This patient does not carry a germline BRCA1 185delAG mutation. Highlighted nucleotides indicate area to be deleted in heterozygote or LOH. B, chromatogram showing sequence in germline BRCA1 185delAG carrier. This sequence was generated from normal pancreatic DNA. Arrow indicates mutation site. C, chromatogram showing LOH at BRCA1 185delAG. DNA was obtained from microdissected PDAC tumor tissue from the same patient as in B. Arrow indicates mutation site. D, chromatogram showing the wild-type sequence of BRCA1 gene at region of 5382insC mutation. This patient does not carry a germline BRCA1 5382insC mutation. E, representative chromatogram showing sequence in the patient with PDAC with germline BRCA1 5382insC mutation. Arrow indicates mutation site. DNA from multiple normal pancreas tissue blocks showed the same sequence. F, chromatogram showing the wild-type sequence at BRCA1 5382insC site in the same patient. Arrow indicates mutation site. Microdissected DNA from multiple tumor blocks showed the same sequence. DNA profiling conrmed that the samples in D and E belong to the same subject.

Figure 2

Representative immunohistochemistry studies from a 59-year-old man with PDAC and a BRCA2 6174delT mutation with LOH. A, representative H&E stain of tumor region. B, extensive staining for p53 in same tumor region, counterstained with hematoxylin only. C, H&E stain of different tumor section. D, greater heterogeneity in p53 staining.