Letitia Smith

Use of Molecular Tumor Characteristics to Prioritize Mismatch Repair Gene Testing in Early-Onset Colorectal Cancer

PURPOSE The relationships between mismatch repair (MMR) protein expression, microsatellite instability (MSI), family history, and germline MMR gene mutation status have not been studied on a population basis. METHODS We studied 131 unselected patients with colorectal cancer diagnosed younger than age 45 years. For the 105 available tumors, MLH1, MSH2, MSH6, and PMS2 protein expression using immunohistochemistry (IHC) and MSI were measured. Germline DNA was screened for hMLH1, hMSH2, hMSH6, and hPMS2 mutations for the following patients: all from families fulfilling the Amsterdam Criteria for hereditary nonpolyposis colorectal cancer (HNPCC); all with tumors that were high MSI, low MSI, or that lacked expression of any MMR protein; and a random sample of 23 with MS-stable tumors expressing all MMR proteins. RESULTS Germline mutations were found in 18 patients (nine hMLH1, four hMSH2, four hMSH6, and one hPMS2); all tumors exhibited loss of MMR protein expression, all but one were high MSI or low MSI, and nine were from a family fulfilling Amsterdam Criteria. Sensitivities of IHC testing, MSI (high or low), and Amsterdam Criteria for MMR gene mutation were 100%, 94%, and 50%, respectively. Corresponding positive predictive values were 69%, 50%, and 75%. CONCLUSIONS Tumor IHC analysis of four MMR proteins and MSI testing provide a highly sensitive strategy for identifying MMR gene mutation-carrying, early-onset colorectal cancer patients, half of whom would have been missed using Amsterdam Criteria alone. Tumor-based approaches for triaging early-onset colorectal cancer patients for MMR gene mutation testing, irrespective of family history, appear to be an efficient screening strategy for HNPCC.

Risk of estrogen receptor-positive and -negative breast cancer and single-nucleotide polymorphism 2q35-rs13387042

BACKGROUND A recent genome-wide association study identified single-nucleotide polymorphism (SNP) 2q35-rs13387042 as a marker of susceptibility to estrogen receptor (ER)-positive breast cancer. We attempted to confirm this association using the Breast Cancer Association Consortium. METHODS 2q35-rs13387042 SNP was genotyped for 31 510 women with invasive breast cancer, 1101 women with ductal carcinoma in situ, and 35 969 female control subjects from 25 studies. Odds ratios (ORs) were estimated by logistic regression, adjusted for study. Heterogeneity in odds ratios by each of age, ethnicity, and study was assessed by fitting interaction terms. Heterogeneity by each of invasiveness, family history, bilaterality, and hormone receptor status was assessed by subclassifying case patients and applying polytomous logistic regression. All statistical tests were two-sided. RESULTS We found strong evidence of association between rs13387042 and breast cancer in white women of European origin (per-allele OR = 1.12, 95% confidence interval [CI] = 1.09 to 1.15; P(trend) = 1.0 x 10(-19)). The odds ratio was lower than that previously reported (P = .02) and did not vary by age or ethnicity (all P > or = .2). However, it was higher when the analysis was restricted to case patients who were selected for a strong family history (P = .02). An association was observed for both ER-positive (OR = 1.14, 95% CI = 1.10 to 1.17; P = 10(-15)) and ER-negative disease (OR = 1.10, 95% CI = 1.04 to 1.15; P = .0003) and both progesterone receptor (PR)-positive (OR = 1.15, 95% CI = 1.11 to 1.19; P = 5 x 10(-14)) and PR-negative disease (OR = 1.10, 95% CI = 1.06 to 1.15; P = .00002). CONCLUSION The rs13387042 is associated with both ER-positive and ER-negative breast cancer in European women.

Missense Variants in ATM in 26,101 Breast Cancer Cases and 29,842 Controls

Background: Truncating mutations in ATM have been shown to increase the risk of breast cancer but the effect of missense variants remains contentious. Methods: We have genotyped five polymorphic (minor allele frequency, 0.9-2.6%) missense single nucleotide polymorphisms (SNP) in ATM (S49C, S707P, F858L, P1054R, and L1420F) in 26,101 breast cancer cases and 29,842 controls from 23 studies in the Breast Cancer Association Consortium. Results: Combining the data from all five SNPs, the odds ratio (OR) was 1.05 for being a heterozygote for any of the SNPs and 1.51 for being a rare homozygote for any of the SNPs with an overall trend OR of 1.06 (Ptrend = 0.04). The trend OR among bilateral and familial cases was 1.12 (95% confidence interval, 1.02-1.23; Ptrend = 0.02). Conclusions: In this large combined analysis, these five missense ATM SNPs were associated with a small increased risk of breast cancer, explaining an estimated 0.03% of the excess familial risk of breast cancer. Impact: Testing the combined effects of rare missense variants in known breast cancer genes in large collaborative studies should clarify their overall contribution to breast cancer susceptibility. Cancer Epidemiol Biomarkers Prev; 19(9); 2143–51. ©2010 AACR.

Morphological predictors of BRCA1 germline mutations in young women with breast cancer

Background:Knowing a young woman with newly diagnosed breast cancer has a germline BRCA1 mutation informs her clinical management and that of her relatives. We sought an optimal strategy for identifying carriers using family history, breast cancer morphology and hormone receptor status data.Methods:We studied a population-based sample of 452 Australian women with invasive breast cancer diagnosed before age 40 years for whom we conducted extensive germline mutation testing (29 carried a BRCA1 mutation) and a systematic pathology review, and collected three-generational family history and tumour ER and PR status. Predictors of mutation status were identified using multiple logistic regression. Areas under receiver operator characteristic (ROC) curves were estimated using five-fold stratified cross-validation.Results:The probability of being a BRCA1 mutation carrier increased with number of selected histology features even after adjusting for family history and ER and PR status (P<0.0001). From the most parsimonious multivariate model, the odds ratio for being a carrier were: 9.7 (95% confidence interval: 2.6–47.0) for trabecular growth pattern (P=0.001); 7.8 (2.7–25.7) for mitotic index over 50 mitoses per 10 high-powered field (P=0.0003); and 2.7 (1.3–5.9) for each first-degree relative with breast cancer diagnosed before age 60 years (P=0.01).The area under the ROC curve was 0.87 (0.83–0.90).Conclusion:Pathology review, with attention to a few specific morphological features of invasive breast cancers, can identify almost all BRCA1 germline mutation carriers among women with early-onset breast cancer without taking into account family history.

Microsatellite Instability Markers for Identifying Early-Onset Colorectal Cancers Caused by Germ-Line Mutations in DNA Mismatch Repair Genes

Purpose: Microsatellite instability (MSI) testing of colorectal cancer tumors is used as a screening tool to identify patients most likely to be mismatch repair (MMR) gene mutation carriers. We wanted to examine which microsatellite markers currently used to detect MSI best predict early-onset colorectal cancer caused by germ-line mutations in MMR genes. Experimental Design: Invasive primary tumors from a population-based sample of 107 cases of colorectal cancer diagnosed before age 45 years and tested for germ-line mutations in MLH1, MSH2, MSH6, and PMS2 and MMR protein expression were screened for MSI using the National Cancer Institute panel and an expanded 10-microsatellite marker panel. Results: The National Cancer Institute five-marker panel system scored 31 (29%) as NCIMSI-High, 13 (12%) as NCIMSI-Low, and 63 (59%) as NCIMS-Stable. The 10-marker panel classified 18 (17%) as 10MSI-High, 17 (16%) as 10MSI-Low, and 72 (67%) as 10MS-Stable. Of the 26 cancers that lacked the expression of at least one MMR gene, 24 (92%) were positive for some level of MSI (using either microsatellite panel). The mononucleotide repeats Bat26, Bat40, and Myb were unstable in all 10MSI-High cancers and all MLH1 and MSH2 mutation carriers (100% sensitive). Bat40 and Bat25 were unstable in all tumors of MSH6 mutation carriers (100% sensitive). Bat40 was unstable in all MMR gene mutation carriers (100% sensitive). By incorporating seven mononucleotide repeats markers into the 10-marker panel, we were able to distinguish the carriers of MSH6 mutations (all scored 10MSI-Low) from the MLH1 and MSH2 mutation carriers (all scored 10MSI-High). Conclusions: In early-onset colorectal cancer, a microsatellite panel containing a high proportion of mononuclear repeats can distinguish between tumors caused by MLH1 and MSH2 mutations from those caused by MSH6 mutations.

The role of SMAD4 in early-onset colorectal cancer.

Objective  Chromosomal loss within the region of 18q and loss of SMAD4 expression have been reported to be frequent somatic events during colorectal cancer tumour progression; however, their associations with age at onset have not been widely studied.

Dependence of colorectal cancer risk on the parent‐of‐origin of mutations in DNA mismatch repair genes

Genetic diseases associated with dynamic mutations in microsatellite DNA often display parent‐of‐origin effects (POEs) in which the risk of disease depends on the sex of the parent from whom the disease allele was inherited. Carriers of germline mutations in mismatch repair (MMR) genes have high risks of colorectal carcinoma (CRC). We investigated whether these risks depend on the parent‐of‐origin of the mutation. We studied 422 subjects, including 89 MMR gene mutation carriers, from 17 population‐based families who were each recruited via a CRC case diagnosed before age 45 years and found to carry a MMR gene mutation. The POE hazard ratio (HRPOE), defined to be the CRC incidence for carriers with maternally derived mutations divided by the corresponding paternal incidence, was estimated using a novel application of modified segregation analysis. HRPOE (95% confidence interval) was estimated to be 3.2 (1.1–9.8) for males (P = 0.03) and 0.8 (0.2–2.8) for females (P = 0.5) and the corresponding cumulative risks to age 80 years were 88% (54%–100%) for male carriers with maternally derived mutations and 38–48% for all other carriers. If confirmed by larger studies, these results will have important implications for the etiology of CRC and for the clinical management of MMR gene mutation carriers.Hum Mutat 32: 1‐6, 2011.

Large genomic alterations in hMSH2 and hMLH1 in early-onset colorectal cancer: identification of a large complex de novo hMLH1 alteration.

To the Editor: The Victorian Colorectal Cancer Family Study is a population-based, case-family study of earlyonset colorectal cancer conducted in Australia during 1993–1997 (1). Eligible case patients comprised adult men and women living in the Melbourne metropolitan area who were under the age of 45 years when diagnosed with a histologically confirmed first primary adenocarcinoma of the colon or rectum (ICD-9 rubrics 153 and 154, respectively) who were identified through the population-wide Victorian Cancer Registry. Invasive tumour samples of primary colorectal adenocarcinoma were obtained from hospitals and private pathology laboratories for 118 case patients (90% of those recruited). The tumour protein expression of MLH1, MSH2, MSH6 and PMS2 was assessed as described and reported elsewhere (2). Microsatellite instability (MSI) was assessed utilizing a five-microsatellite marker panel (3, 4). All exonic and flanking intronic sequences of hMLH1, hMSH2, hMSH6 and hPMS2were screened for germline mutations using sequencing approaches, except for exon 4 of hMSH6 that was screened in eight overlapping fragments using denaturing high-performance liquid chromatography (DHPLC) (2). The multiplex ligation-dependent probe amplification (MLPA) assay (MRC-Holland, Amsterdam, The Netherlands) (5) was used to detect large genomic alterations in hMLH1 and hMSH2 and was performed on samples from 10 case patients that had tumours lacking expression of at least one mismatch repair (MMR) protein and for which no mutation had been identified byDNA-sequencing methods or DHPLC. Breakpoints were characterized by performing a long-range PCR encompassing the predicted genomic alteration, cloning and sequencing. PCR primer sequences and PCR product sizes are given in Table 1 panel a. The germline DNA from two individuals were found to have MLPA profiles consistent with having a large deletion in hMLH1. No alterations were identified in hMSH2. Case 1 was a male diagnosed with cancer of the transverse colon at the age of 24 years, with no reported family history of colorectal cancer in any firstor second-degree relative. The endoscopic biopsywasMSI high, displaying instability in four of the five markers tested (Bat25, Bat26, D5S345 and D17S250). The tumour expressed MSH2 and MSH6 protein, lacked the expression of PMS2, and some focal cells were negative for MLH1 as determined by immuno-histo-chemistry (IHC). MLPA analysis suggested that exon 15 of hMLH1 was deleted in the germline. Long-range PCR confirmed the deletion by identifying the breakpoint, a deletion of 1444 bp and a 264–269 bp insertion. Specifically, the genomic change was hMLH1, 50334del1444 and 50334ins264–269 (reference sequence accessionnumberAY217549).The insertion of 264–269 bp between the breakpoints identifiedhas99%homologyto theAlu-repeat subfamily Sb2 (accession number U14570). This complex mutation is illustrated in Fig. 1(a). A specific test was devised utilizing long-range PCR over the breakpoint region, and other participating family members were screened for hMLH1, 50334del1444ins264–269 (Table 1 panel a). Neither parent was found to carry this mutation. Two microsatellite markers, UT5013 and UT1699 (6), confirmed parentage, implying that thismutationwas de novo. Case 2 was a male diagnosed with cancer of the ascending colon at the age of 42 years, with a brother diagnosed with cancer of the caecum at age 36, a sister diagnosed with cancer of the colon at age 41, and father diagnosed with cancer of the stomach at age 67. This family history was sufficient to meet the Amsterdam II criteria for hereditary non-polyposis colorectal cancer

Contribution of large genomic BRCA1 alterations to early-onset breast cancer selected for family history and tumour morphology: a report from The Breast Cancer Family Registry

IntroductionSelecting women affected with breast cancer who are most likely to carry a germline mutation in BRCA1 and applying the most appropriate test methodology remains challenging for cancer genetics services. We sought to test the value of selecting women for BRCA1 mutation testing on the basis of family history and/or breast tumour morphology criteria as well as the value of testing for large genomic alterations in BRCA1 .MethodsWe studied women participating in the Breast Cancer Family Registry (BCFR), recruited via population-based sampling, who had been diagnosed with breast cancer before the age of 40 years who had a strong family history of breast or ovarian cancer (n = 187) and/or a first primary breast tumour with morphological features consistent with carrying a BRCA1 germline mutation (n = 133; 37 met both criteria). An additional 184 women diagnosed before the age of 40 years who had a strong family history of breast or ovarian cancer and who were not known to carry a germline BRCA1 mutation were selected from among women who had been recruited into the BCFR from clinical genetics services. These 467 women had been screened for BRCA1 germline mutations, and we expanded this testing to include a screen for large genomic BRCA1 alterations using Multiplex Ligation-dependent Probe Amplification.ResultsTwelve large genomic BRCA1 alterations were identified, including 10 (4%) of the 283 women selected from among the population-based sample. In total, 18 (12%), 18 (19%) and 16 (43%) BRCA1 mutations were identified in the population-based groups selected on the basis of family history only (n = 150), the group selected on the basis of tumour morphology only (n = 96) and meeting both criteria (n = 37), respectively.ConclusionsLarge genomic alterations accounted for 19% of all BRCA1 mutations identified. This study emphasises the value of combining information about family history, age at diagnosis and tumour morphology when selecting women for germline BRCA1 mutation testing as well as including a screen for large genomic alterations.

7q21-rs6964587 and breast cancer risk: An extended case-control study by the Breast Cancer Association Consortium

Background Using the Breast Cancer Association Consortium, the authors previously reported that the single nucleotide polymorphism 7q21-rs6964587 (AKAP9-M463I) is associated with breast cancer risk. The authors have now assessed this association more comprehensively using 16 independent case–control studies. Methods The authors genotyped 14 843 invasive case patients and 19 852 control subjects with white European ancestry and 2595 invasive case patients and 2192 control subjects with Asian ancestry. ORs were estimated by logistic regression, adjusted for study. Heterogeneity in ORs was assessed by fitting interaction terms or by subclassifying case patients and applying polytomous logistic regression. Results For white European women, the minor T allele of 7q21-rs6964587 was associated with breast cancer risk under a recessive model (OR 1.07, 95% CI 1.00 to 1.13, p=0.04). Results were inconclusive for Asian women. From a combined analysis of 24 154 case patients and 33 376 control subjects of white European ancestry from the present and previous series, the best-fitting model was recessive, with an estimated OR of 1.08 (95% CI 1.03 to 1.13, p=0.001). The OR was greater at younger ages (p trend=0.01). Conclusion This may be the first common susceptibility allele for breast cancer to be identified with a recessive mode of inheritance.