Kathleen Conway

Number of Nevi and Early-Life Ambient UV Exposure Are Associated with BRAF-Mutant Melanoma

Malignant melanomas often contain BRAF or NRAS mutations, but the relationship of these mutations to ambient UV exposure in combination with phenotypic characteristics is unknown. In a population-based case series from North Carolina, 214 first primary invasive melanoma patients in the year 2000 were interviewed regarding their risk factors. Ambient solar UV exposures were estimated using residential histories and a satellite-based model. Cases were grouped on the basis of BRAF and NRAS somatic mutations, determined using single-strand conformation polymorphism analysis and radiolabeled DNA sequencing, and the risk profiles of these groups were compared. Mutually exclusive BRAF-mutant and NRAS-mutant cases occurred at frequencies of 43.0% and 13.6% with mean ages at diagnosis of 47.3 and 62.1 years, respectively. Tumors from patients with >14 back nevi were more likely to harbor either a BRAF mutation [age-adjusted odds ratio (OR), 3.2; 95% confidence interval (95% CI), 1.4-7.0] or an NRAS mutation (age-adjusted OR, 1.7; 95% CI, 0.6-4.8) compared with patients with 0 to 4 back nevi. However, BRAF-mutant and NRAS-mutant tumors were distinctive in that BRAF-mutant tumors were characteristic of patients with high early-life ambient UV exposure (adjusted OR, 2.6; 95% CI, 1.2-5.3). When ambient UV irradiance was analyzed by decadal age, high exposure at ages 0 to 20 years was associated with BRAF-mutant cases, whereas high exposure at ages 50 and 60 years was characteristic of NRAS-mutant cases. Our results suggest that although nevus propensity is important for the occurrence of both BRAF and NRAS-mutant melanomas, ambient UV irradiance influences risk differently based on the age of exposure. The association of BRAF mutations with early-life UV exposure provides evidence in support of childhood sun protection for melanoma prevention. (Cancer Epidemiol Biomarkers Prev 2007;16(5):991–7)

HER-2/neu Amplification in Benign Breast Disease and the Risk of Subsequent Breast Cancer

PURPOSE The purpose of this study was to determine whether the presence of HER-2/neu gene amplification and/or overexpression in benign breast disease was associated with an increased risk of subsequent breast cancer. PATIENTS AND METHODS We conducted a nested case-control study of a cohort of women who were diagnosed with benign breast disease at the Mayo Clinic and who were subsequently observed for the development of breast cancer. Patients who developed breast cancer formed the case group, and a matched sample from the remaining cohort served as controls. Benign tissue samples from 137 cases and 156 controls and malignant tissues from 99 cases provided DNA or tissue for evaluation of HER-2/neu amplification and protein overexpression. RESULTS Among the controls, seven benign tissues (4.5%) demonstrated low-level HER-2/neu amplification, whereas 13 benign (9.5%) and 18 malignant (18%) tissue specimens from cases exhibited amplification. HER-2/neu amplification in benign breast biopsies was associated with an increased risk of breast cancer (odds ratio ¿OR = 2.2; 95% confidence interval ¿CI, 0.9 to 5.8); this association approached statistical significance. The risks for breast cancer associated with benign breast histopathologic diagnoses were OR = 1.1 (95% CI, 0.6 to 1.9) for lesions exhibiting proliferation without atypia and OR = 1.5 (95% CI, 0.4 to 5.6) for the diagnosis of atypical ductal hyperplasia. For women having both HER-2/neu amplification and a proliferative histopathologic diagnosis (either typical or atypical), the risk of breast cancer was more than seven-fold (OR = 7.2; 95% CI, 0.9 to 60.8). Overexpression of the HER-2/neu protein product, defined as membrane staining in 10% or more of epithelial cells, was found in 30% of the breast tumors but was not detected in any of the benign breast tissues. Case patients who had HER-2/neu gene amplification in their malignant tumor were more likely to have had HER-2/neu amplification in their prior benign biopsy (P =.06, Fishers exact test). CONCLUSION Women with benign breast biopsies demonstrating both HER-2/neu amplification and a proliferative histopathologic diagnosis may be at substantially increased risk for subsequent breast cancer.

Alterations of the p16 gene in head and neck cancer: frequency and association with p53, PRAD-1 and HPV

Alterations, especially homozygous deletions, of the putative tumor suppressor gene, p16 (p16INK4A, MTS1, CDKN2) have been found in tumor cell lines from a variety of neoplasms. Recent studies have reported frequent p16 gene deletions in cell lines from squamous cell carcinomas of the head and neck (SCCHN), although the prevalence of alterations was variable in primary tumors. This study determined the prevalence of point mutations and deletions of the p16 gene in 33 SCCHN. In addition, the association of p16 gene alterations and abnormalities of p53, PRAD-1 (cyclin D1), and the presence of human papillomavirus (HPV) was examined. We found an overall prevalence of p16 alterations of 36% (nine deletions, three single base substitutions, including one polymorphism). Seven tumors (of 29, 24%) had an alteration of p16 and p53; five (of 33, 15%) had alterations of p16 and PRAD-1; three (of 29, 10%) had alterations of all three genes. In addition, of the five tumors with human papillomavirus detected, only one also had a p16 gene alteration. The results indicate a potentially important role for the p16 gene in head and neck tumorigenesis. In addition, the presence of tumors with multiple somatic gene alterations suggest a possible interaction in the dysregulation of the cell cycle.

Polychlorinated biphenyls, cytochrome P450 1A1 (CYP1A1) polymorphisms, and breast cancer risk among African American women and white women in North Carolina: a population-based case-control study

IntroductionEpidemiologic studies have not shown a strong relationship between blood levels of polychlorinated biphenyls (PCBs) and breast cancer risk. However, two recent studies showed a stronger association among postmenopausal white women with the inducible M2 polymorphism in the cytochrome P450 1A1 (CYP1A1) gene.MethodsIn a population-based case-control study, we evaluated breast cancer risk in relation to PCBs and the CYP1A1 polymorphisms M1 (also known as CYP1A1*2A), M2 (CYP1A1*2C), M3 (CYP1A1*3), and M4 (CYP1A1*4). The study population consisted of 612 patients (242 African American, 370 white) and 599 controls (242 African American, 357 white).ResultsThere was no evidence of strong joint effects between CYP1A1 M1-containing genotypes and total PCBs in African American or white women. Statistically significant multiplicative interactions were observed between CYP1A1 M2-containing genotypes and elevated plasma total PCBs among white women (P value for likelihood ratio test = 0.02). Multiplicative interactions were also observed between CYP1A1 M3-containing genotypes and elevated total PCBs among African American women (P value for likelihood ratio test = 0.10).ConclusionsOur results confirm previous reports that CYP1A1 M2-containing genotypes modify the association between PCB exposure and risk of breast cancer. We present additional evidence suggesting that CYP1A1 M3-containing genotypes modify the effects of PCB exposure among African American women. Additional studies are warranted, and meta-analyses combining results across studies will be needed to generate more precise estimates of the joint effects of PCBs and CYP1A1 genotypes.

Cigarette smoking, cytochrome P4501A1 polymorphisms, and breast cancer among African-American and white women

IntroductionPrevious epidemiologic studies suggest that women with variant cytochrome P4501A1 (CYP1A1) genotypes who smoke cigarettes are at increased risk for breast cancer.MethodsWe evaluated the association of breast cancer with CYP1A1 polymorphisms and cigarette smoking in a population-based, case–control study of invasive breast cancer in North Carolina. The study population consisted of 688 cases (271 African Americans and 417 whites) and 702 controls (285 African Americans and 417 whites). Four polymorphisms in CYP1A1 were genotyped using PCR/restriction fragment length polymorphism analysis: M1 (also known as CYP1A1*2A), M2 (CYP1A1*2C), M3 (CYP1A1*3), and M4 (CYP1A1*4)ResultsNo associations were observed for CYP1A1 variant alleles and breast cancer, ignoring smoking. Among women who smoked for longer than 20 years, a modest positive association was found among women with one or more M1 alleles (odds ratio [OR] = 2.1, 95% confidence interval [CI] = 1.2–3.5) but not among women with non-M1 alleles (OR = 1.2, 95% CI = 0.9–1.6). Odds ratios for smoking longer than 20 years were higher among African-American women with one or more M3 alleles (OR = 2.5, 95% CI = 0.9–7.1) compared with women with non-M3 alleles (OR = 1.3, 95% CI = 0.8–2.2). ORs for smoking in white women did not differ appreciably based upon M2 or M4 genotypes.ConclusionsCigarette smoking increases breast cancer risk in women with CYP1A1 M1 variant genotypes and in African-American women with CYP1A1 M3 variant genotypes, but the modifying effects of the CYP1A1 genotype are quite weak.

HER2 codon 655 polymorphism and risk of breast cancer in African Americans and whites.

AbstractBackground. Several recent epidemiologic studies examined the association between breast cancer risk and an inherited, single-nucleotide polymorphism in the HER2 gene, codon 655 G to A, which leads to an amino acid substitution of Ile to Val. Results of previous studies have been mixed, with most studies showing no association but some suggesting an association in younger women or women with a family history of breast cancer. Methods. We conducted an association study of HER2 codon 655 genotype and breast cancer within the Carolina Breast Cancer study, a population-based, case-control study of in situ and invasive breast cancer in African American and white women in North Carolina. A total of 2015 cases and 1808 controls were genotyped. Results. We observed no overall association between HER2 genotype and breast cancer. However, a modest positive association (OR = 2.3, 95% CI 1.0–5.3) was observed for Val/Val + Ile/Val versus Ile/Ile genotypes in women age 45 or younger with a family history of breast cancer. Val/Val homozygotes were more common among cases with in situ versus invasive disease (P = 0.002). Breast tumors from women with Val/Val genotype were more likely to exhibit HER2 overexpression, but the results were not statistically significant (P = 0.17). Conclusions. The HER2 codon 655 polymorphism may be one of many low-penetrant genes that make a minor contribution to breast cancer, particularly in subgroups of women. Additional large studies, as well as data pooling, will be needed to estimate the contribution of such genes to breast cancer risk.

DNA‐methylation profiling distinguishes malignant melanomas from benign nevi

DNA methylation, an epigenetic alteration typically occurring early in cancer development, could aid in the molecular diagnosis of melanoma. We determined technical feasibility for high‐throughput DNA‐methylation array‐based profiling using formalin‐fixed paraffin‐embedded tissues for selection of candidate DNA‐methylation differences between melanomas and nevi. Promoter methylation was evaluated in 27 common benign nevi and 22 primary invasive melanomas using a 1505 CpG site microarray. Unsupervised hierarchical clustering distinguished melanomas from nevi; 26 CpG sites in 22 genes were identified with significantly different methylation levels between melanomas and nevi after adjustment for age, sex, and multiple comparisons and with β‐value differences of ≥0.2. Prediction analysis for microarrays identified 12 CpG loci that were highly predictive of melanoma, with area under the receiver operating characteristic curves of >0.95. Of our panel of 22 genes, 14 were statistically significant in an independent sample set of 29 nevi (including dysplastic nevi) and 25 primary invasive melanomas after adjustment for age, sex, and multiple comparisons. This first report of a DNA‐methylation signature discriminating melanomas from nevi indicates that DNA methylation appears promising as an additional tool for enhancing melanoma diagnosis.

No Association Between the MDM2 −309 T/G Promoter Polymorphism and Breast Cancer in African-Americans or Whites

MDM2, a protein that binds and inactivates the tumor suppressor p53, is overexpressed in a variety of human cancers ([1][1]). Bond et al. ([2][2]) recently identified a single nucleotide polymorphism in the MDM2 gene, −309 T/G within the MDM2 promoter (database for single nucleotide polymorphism

The estrogen receptor-α A908G (K303R) mutation occurs at a low frequency in invasive breast tumors: results from a population-based study

IntroductionEvidence suggests that alterations in estrogen signaling pathways, including estrogen receptor-α (ER-α), occur during breast cancer development. A point mutation in ER-α (nucleotide A908G), producing an amino acid change from lysine to arginine at codon 303 (K303R) results in receptor hypersensitivity to estrogen. This mutation was initially reported in one-third of hyperplastic benign breast lesions, although several recent studies failed to detect it in benign or malignant breast tissues.MethodsWe screened 653 microdissected, newly diagnosed invasive breast tumors from patients in the Carolina Breast Cancer Study, a population-based case-control study of breast cancer in African American and white women in North Carolina, for the presence of the ER-α A908G mutation by using single-strand conformational polymorphism (SSCP) analysis and 33P-cycle sequencing.ResultsWe detected the ER-α A908G mutation in 37 of 653 (5.7%) breast tumors. The absence of this mutation in germline DNA confirmed it to be somatic. Three tumors exhibited only the mutant G base at nucleotide 908 on sequencing, indicating that the wild-type ER-α allele had been lost. The ER-α A908G mutation was found more frequently in higher-grade breast tumors (odds ratio (OR) 2.83; 95% confidence interval (CI) 1.09 to 7.34, grade II compared with grade I), and in mixed lobular/ductal tumors (OR 2.10; 95% CI 0.86 to 5.12) compared with ductal carcinomas, although the latter finding was not statistically significant.ConclusionThis population-based study, the largest so far to screen for the ER-α A908G mutation in breast cancer, confirms the presence of the mutant in invasive breast tumors. The mutation was associated with higher tumor grade and mixed lobular/ductal breast tumor histology.

DNA methylation profiling in the Carolina Breast Cancer Study defines cancer subclasses differing in clinicopathologic characteristics and survival

IntroductionBreast cancer is a heterogeneous disease, with several intrinsic subtypes differing by hormone receptor (HR) status, molecular profiles, and prognosis. However, the role of DNA methylation in breast cancer development and progression and its relationship with the intrinsic tumor subtypes are not fully understood.MethodsA microarray targeting promoters of cancer-related genes was used to evaluate DNA methylation at 935 CpG sites in 517 breast tumors from the Carolina Breast Cancer Study, a population-based study of invasive breast cancer.ResultsConsensus clustering using methylation (β) values for the 167 most variant CpG loci defined four clusters differing most distinctly in HR status, intrinsic subtype (luminal versus basal-like), and p53 mutation status. Supervised analyses for HR status, subtype, and p53 status identified 266 differentially methylated CpG loci with considerable overlap. Genes relatively hypermethylated in HR+, luminal A, or p53 wild-type breast cancers included FABP3, FGF2, FZD9, GAS7, HDAC9, HOXA11, MME, PAX6, POMC, PTGS2, RASSF1, RBP1, and SCGB3A1, whereas those more highly methylated in HR-, basal-like, or p53 mutant tumors included BCR, C4B, DAB2IP, MEST, RARA, SEPT5, TFF1, THY1, and SERPINA5. Clustering also defined a hypermethylated luminal-enriched tumor cluster 3 that gene ontology analysis revealed to be enriched for homeobox and other developmental genes (ASCL2, DLK1, EYA4, GAS7, HOXA5, HOXA9, HOXB13, IHH, IPF1, ISL1, PAX6, TBX1, SOX1, and SOX17). Although basal-enriched cluster 2 showed worse short-term survival, the luminal-enriched cluster 3 showed worse long-term survival but was not independently prognostic in multivariate Cox proportional hazard analysis, likely due to the mostly early stage cases in this dataset.ConclusionsThis study demonstrates that epigenetic patterns are strongly associated with HR status, subtype, and p53 mutation status and may show heterogeneity within tumor subclass. Among HR+ breast tumors, a subset exhibiting a gene signature characterized by hypermethylation of developmental genes and poorer clinicopathologic features may have prognostic value and requires further study. Genes differentially methylated between clinically important tumor subsets have roles in differentiation, development, and tumor growth and may be critical to establishing and maintaining tumor phenotypes and clinical outcomes.