Identification of novel candidate genes associated with cleft lip and palate using array comparative genomic hybridisation

AIM AND METHOD

We analysed DNA samples isolated from individuals born with cleft lip and cleft palate to identify deletions and duplications of candidate gene loci using array comparative genomic hybridisation (array-CGH).

RESULTS

Of 83 syndromic cases analysed we identified one subject with a previously unknown 2.7 Mb deletion at 22q11.21 coinciding with the DiGeorge syndrome region. Eighteen of the syndromic cases had clinical features of Van der Woude syndrome and deletions were identified in five of these, all of which encompassed the interferon regulatory factor 6 (IRF6) gene. In a series of 104 non-syndromic cases we found one subject with a 3.2 Mb deletion at chromosome 6q25.1-25.2 and another with a 2.2 Mb deletion at 10q26.11-26.13. Analyses of parental DNA demonstrated that the two deletion cases at 22q11.21 and 6q25.1-25.2 were de novo, while the deletion of 10q26.11-26.13 was inherited from the mother, who also has a cleft lip. These deletions appear likely to be causally associated with the phenotypes of the subjects. Estrogen receptor 1 (ESR1) and fibroblast growth factor receptor 2 (FGFR2) genes from the 6q25.1-25.2 and 10q26.11-26.13, respectively, were identified as likely causative genes using a gene prioritization software.

CONCLUSION

We have shown that array-CGH analysis of DNA samples derived from cleft lip and palate subjects is an efficient and productive method for identifying candidate chromosomal loci and genes, complementing traditional genetic mapping strategies.

CYP17 genotype is associated with short menstrual cycles, early oral contraceptive use and BRCA mutation status in young healthy women

The CYP17 gene is involved in steroid hormone metabolism and has been proposed as a low penetrance gene for breast cancer. We aimed to investigate the associations between the CYP17 genotype and breast cancer risk factors, such as age at menarche, menstrual cycle length, oral contraceptive (OC) use, and BRCA mutation status among 258 healthy young women, aged < or =40, from 158 breast cancer high-risk families. Questionnaires including questions on reproductive factors and OC use were completed and blood samples were obtained from all women. CYP17 (rs743572) was genotyped with sequencing in 254 women. The main findings were that short menstrual cycles (<27 days) were significantly more common with increasing number of variant A2 alleles (8%, 17% and 32%; P(trend) = 0.002, adjusted for family clustering). Each A2 allele was associated with a 7 months earlier OC start (17.8, 17.0, and 16.6 years; P(trend) = 0.014, adjusted for age at menarche, ever-smoking and family clustering). Homozygosity for the A2 allele was more common among known non-carriers from BRCA1/2 families compared with other high-risk women OR 2.92 (95% CI 1.49-5.73; P = 0.002, adjusted for family clustering). We found no association between CYP17 genotype and age at menarche. In conclusion, this study suggests that short menstrual cycles, age at first OC use and BRCA mutation status may need to be considered in studies exploring the relationships between CYP17 and risk factors for early onset breast cancer.

Genomic profiling of malignant melanoma using tiling-resolution arrayCGH

Malignant melanoma is an aggressive, heterogeneous disease where new biomarkers for diagnosis and clinical outcome are needed. We searched for chromosomal aberrations that characterize its pathogenesis using 47 different melanoma cell lines and tiling-resolution bacterial artificial chromosome-arrays for comparative genomic hybridization. Major melanoma genes, including BRAF, NRAS, CDKN2A, TP53, CTNNB1, CDK4 and PTEN, were examined for mutations. Distinct copy number alterations were detected, including loss or gain of whole chromosomes but also minute amplifications and homozygous deletions. Most common overlapping regions with losses were mapped to 9p24.3-q13, 10 and 11q14.1-qter, whereas copy number gains were most frequent on chromosomes 1q, 7, 17q and 20q. Amplifications were delineated to oncogenes such as MITF (3p14), CCND1 (11q13), MDM2 (12q15), CCNE1 (19q12) and NOTCH2 (1p12). Frequent findings of homozygous deletions on 9p21 and 10q23 confirmed the importance of CDKN2A and PTEN. Pair-wise comparisons revealed distinct sets of alterations, for example, mutually exclusive mutations in BRAF and NRAS, mutual mutations in BRAF and PTEN, concomitant chromosome 7 gain and 10 loss and concomitant chromosome 15q22.2-q26.3 gain and 20 gain. Moreover, alterations of the various melanoma genes were associated with distinct chromosomal imbalances suggestive of specific genomic programs in melanoma development.

Nordic collaborative study of the BARD1 Cys557Ser allele in 3956 patients with cancer: enrichment in familial BRCA1/BRCA2 mutation-negative breast cancer but not in other malignancies

BACKGROUND

BARD1 was originally identified as a BRCA1-interacting protein but has also been described in tumour-suppressive functions independent of BRCA1. Several studies have indicated that the BARD1 gene is a potential target for germline changes predisposing to breast and ovarian cancer. The C-terminal Cys557Ser change has previously been uncovered to associate with an increased risk of breast cancer and was recently shown to result in defective apoptotic activities.

AIM AND METHODS

Conformation-sensitive gel electrophoresis, minisequencing, TaqMan assays, denaturing high-performance liquid chromatography analysis and DNA sequencing were used to investigate the prevalence of the Cys557Ser allele in a large Nordic case-control study cohort consisting of 2906 patients with breast or ovarian cancer, 734 with prostate cancer, 188 with colorectal cancer, 128 men with breast cancer, and 3591 controls from Finland, Iceland, Denmark, Sweden and Norway.

RESULTS

The frequency of the BARD1 Cys557Ser variant seemed to increase among patients from families with breast or ovarian cancer lacking BRCA1 or BRCA2 mutations: a significant difference was obtained compared with controls (6.8% v 2.7%; p<0.001; odds ratio (OR) 2.6; 95% confidence interval (CI) 1.7 to 4.0) and with patients from BRCA1/BRCA2 mutation-positive families (6.8% v 2.2%; p = 0.01; OR 3.2; 95% CI 1.2 to 8.3). In contrast, no major association with male breast, ovarian, colorectal or prostate cancer was observed. Additionally, a novel BARD1 allele resulting in Ser558Pro was identified in familial breast cancer cases.

CONCLUSION

These results provide further evidence that BARD1 Cys557Ser confers a slightly increased risk of breast cancer in women.

High D-dimer levels at presentation in patients with venous thromboembolism is a marker of adverse clinical outcomes

Qualitative D-dimer results, together with clinical probability scores, are well established in the diagnosis of venous thromboembolism (VTE). The predictive value of quantitative D-dimer levels for various clinical outcomes in VTE patients is not fully understood. D-dimer levels obtained at presentation were analysed in 699 (360 men; 339 women) VTE patients for survival and occurrence of malignancy. Patients were followed for a median of 23 months. 17.2% patients had a D-dimer level >8000 ng FEU/mlat presentation, which was associated with decreased overall survival (OS) (P < 0.001) and event-free survival (EFS) (P < 0.001). 25.4% patients had malignancy and 4% subsequently developed malignancy following VTE. 29.9% of patients with VTE and malignancy had a D-dimer level >8 mg/l when compared with 13.4% of patients with VTE without malignancy (P < 0.001). 50% of patients who developed subsequent malignancy following VTE had a presentation D-dimer >8000 ng FEU/mlas compared with 13.3% of patients with VTE with out malignancy (P = 0.009). In conclusion, D-dimer >8000 ng FEU/ml at presentation in patients with VTE is a marker of poor OS, EFS and underlying malignancy. Consideration of screening for malignancy is recommended in patients with VTE with a presentation D-dimer >8000 ng FEU/ml and age >60 years.

Identification of cryptic aberrations and characterization of translocation breakpoints using array CGH in high hyperdiploid childhood acute lymphoblastic leukemia

High hyperdiploidy, characterized by non-random trisomies, is the largest cytogenetic subgroup in childhood acute lymphoblastic leukemia (ALL). It is not known whether the gained chromosomes are sufficient for leukemogenesis or if additional genetic aberrations are necessary. However, the suboptimal chromosome morphology of hyperdiploid ALLs makes detection of structural abnormalities difficult if using cytogenetic techniques; alternative methods are, therefore, needed. We performed array comparative genome hybridization (CGH) analyses, with a resolution of 100 kb, of eight cases of high hyperdiploid childhood ALL to characterize structural abnormalities found with G-banding/multicolor fluorescence in situ hybridization (FISH) and to detect novel changes. The non-centromeric breakpoints of four rearrangements, including three translocations and one 1q duplication, were narrowed down to <0.2 Mb. Furthermore, four submicroscopic imbalances involving 0.6-2.7 Mb were detected, comprising two segmental duplications involving 1q22 and 12q24.31 in one case and two hemizygous deletions in 12p13.2-31 - including ETV6 - and in 13q32.3-33.1 in another case. Notably, FISH analysis of the latter revealed an associated reciprocal t(3;13)(q?;32.2-33.1). In conclusion, the array CGH analyses revealed putative leukemia-associated submicroscopic imbalances and rearrangements in 2/8 (25%) hyperdiploid ALLs. The detection and characterization of these additional genetic aberrations will most likely increase our understanding of the pathogenesis of high hyperdiploid childhood ALL.

Insulin-like growth factor-1 genotype predicts breast volume after pregnancy and hormonal contraception and is associated with circulating insulin-like growth factor-1 levels: implications for risk of early-onset breast cancer in young women from hereditary breast cancer families

BACKGROUND

BRCA1/2 mutations predispose to early-onset breast cancer, especially after oral contraceptive (OC) use and pregnancy. However, the majority of breast cancers might be due to more prevalent low penetrance genes that may also modify the risk in BRCA1/2 mutation carriers. The absence of the IGF1 19-CA repeat allele has been associated with high insulin-like growth factor-1 (IGF-1) levels during OC use in nulliparous women of four different ethnic groups. High IGF-1 levels are linked to an increased risk of early-onset breast cancer and to larger breast volumes in the general population. It has also been hypothesized that women whose breast size increases while exposed to OCs may be at increased risk of future breast cancer.

AIM

We explored the effect of the IGF1 genotype, specifically the absence of the common 19-CA repeat allele in the promoter region of the IGF1 gene, in combination with oral contraceptive (OC) use or parity on breast volume and IGF-1 levels.

MATERIALS AND METHODS

Two hundred fifty-eight healthy women, </=40 years old, from hereditary breast cancer families participated in this prospective study. Twenty-three women were known BRCA1 mutation carriers, 7 women were known BRCA2 mutation carriers, 54 women were noncarriers from BRCA1/2 families, 111 women belonged to breast cancer families where no BRCA1 or BRCA2 mutations were detected, and 63 women were untested from high-risk breast cancer families. All women completed a questionnaire including information on reproductive factors and OC use. We measured height, weight, breast volumes, and plasma IGF-1 levels once during menstrual cycle days 5-10 and once again during menstrual cycle days 18-23. The IGF1 genotype was successfully analyzed with polymerase chain reaction and fragment analyses in 254 women.

RESULTS

Thirteen percent had no IGF1 19-CA repeat allele. The absence of the 19-CA repeat allele was more common among women with known BRCA1 mutations compared to other women (26% versus 12%; P= 0.05). See updated and revised Table 1 from original publication. IGF-1 levels were similar among parous and nulliparous women not using OCs, which is in contrast to results from women in the general population, where parous women have lower IGF-1 levels than nulliparous women. Furthermore, OC use did not affect IGF-1 levels in parous women in our study. BRCA mutation status did not affect age-adjusted IGF-1 levels in either cycle phase among nonusers. Most of the nulliparous OC users had lower IGF-1 levels than nonusers. However, there was an interaction between IGF1 genotype and OC use on IGF-1 levels in nulliparous women (P= 0.026). Compared with nonusers, IGF-1 levels were highly suppressed in OC users with a 19-CA repeat allele (P < 0.001), but not among women lacking the 19-CA repeat allele (P= 0.81). We also observed an interaction between parity and IGF1 genotype on breast volume (P= 0.01). Absence of the 19-CA repeat allele was associated with larger breast volumes in parous versus nulliparous women and OC users, while parous women and OC users with the 19-CA repeat allele had smaller breast volumes than nulliparous women and nonusers adjusted for body weight. During follow-up, six incident breast cancers cases occurred, four in known BRCA1 mutation carriers and two in untested women. Incident breast cancers were associated with absence of the 19-CA repeat allele (log-rank; P= 0.002).

CONCLUSION

Our results suggest that absence of the IGF1 19-CA repeat allele modifies IGF-1 levels, breast volume, and possibly early-onset breast cancer risk after hormone exposure in young, high-risk women. These results warrant confirmation in a larger prospective cohort of high-risk women. If confirmed, the IGF1 genotype could be incorporated as an additional marker to improve risk estimates for early-onset breast cancer during genetic counseling of women from high-risk breast cancer families.

Testosterone levels in relation to oral contraceptive use and the androgen receptor CAG and GGC length polymorphisms in healthy young women

BACKGROUND

The combined effect from the androgen receptor (AR) CAG and GGC length polymorphisms on testosterone levels has not been studied in young women.

METHODS

Testosterone levels were measured in blood drawn on both menstrual cycle days 5-10 and 18-23 in 258 healthy women, aged < or =40 years, from high-risk breast cancer families. CAG and GGC length polymorphisms were analysed by PCR and fragment analyses. All women completed a questionnaire including information on oral contraceptive (OC) use and reproductive factors.

RESULTS

OC users had lower median testosterone levels than non-users during cycle days 5-10 and 18-23 (P < or = 0.005 for both). The BRCA mutation status was associated neither with testosterone levels nor with CAG or GGC length polymorphism. The CAG length polymorphism was not associated with testosterone levels. The cumulative number of long GGC alleles (> or =17 repeats) was significantly associated with lower testosterone levels in OC users during cycle days 5-10 (P(trend) =0.014), but not during cycle days 18-23 or in non-users. The interaction between the GGC length polymorphism and OC status was highly significant during cycle days 5-10 (P = 0.002) and near-significant during days 18-23 (P = 0.07). Incident breast cancer was more common in women with two short GGC alleles (log-rank P = 0.003).

CONCLUSION

The GGC repeat length was the only significant genetic factor modifying the testosterone levels in current OC users from high-risk families. Homozygosity for the short GGC allele may be linked to the increased risk of early-onset breast cancer after OC exposure in high-risk women.

Molecular characterization of early-stage bladder carcinomas by expression profiles, FGFR3 mutation status, and loss of 9q

We used gene expression profiling, mutation analyses of FGFR3 and TP53, and LOH analyses of chromosome 9 and the TP53 region on chromosome arm 17p, to molecularly characterize 75 Ta and T1 bladder carcinomas. We identified four major cellular processes related to cell cycle, protein synthesis, immune response, and extra cellular components that contribute to the expressional heterogeneity of early-stage urothelial cell carcinoma (UCC). Activating FGFR3 mutations were found at the highest frequency in G1 tumors (80%), and showed a strong correlation with FGFR3 expression. In contrast, G3 tumors displayed mutations in less than 10% of the cases and a low level of FGFR3 expression. Even though LOH on chromosome 9 was not associated with any specific expression pattern, our data indicate that loss of chromosome 9 is associated with tumor development rather than initiation. The combined analyses suggest the existence of two types of UCC tumors, one which is characterized by FGFR3 mutation or expression, high expression of protein synthesis genes, and low expression of cell cycle genes. Furthermore, the presented data underscore FGFR3 receptor involvement in urothelial cell transformation as the presence of FGFR3 mutations has a major impact on the global gene expression profile of bladder carcinomas.

Genomic profiling of bone and soft tissue tumors with supernumerary ring chromosomes using tiling resolution bacterial artificial chromosome microarrays

Ring chromosomes and/or giant marker chromosomes have been observed in a variety of human tumor types, but they are particularly common in a subgroup of mesenchymal tumors of low-grade or borderline malignancy. These rings and markers have been shown to contain amplified material predominantly from 12q13-15, but also sequences from other chromosomes. Such amplified sequences were mapped in detail by genome-wide array comparative genomic hybridization in ring-containing tumor samples from soft tissue (n = 15) and bone (n = 6), using tiling resolution microarrays, encompassing 32 433 bacterial artificial chromosome clones. The DNA copy number profiles revealed multiple amplification targets, in many cases highly discontinuous, leading to delineation of large numbers of very small amplicons. A total number of 356 (median size: 0.64 Mb) amplicons were seen in the soft tissue tumors and 90 (median size: 1.19 Mb) in the bone tumors. Notably, more than 40% of all amplicons in both soft tissue and bone tumors were mapped to chromosome 12, and at least one of the previously reported recurrent amplifications in 12q13.3-14.1 and 12q15.1, including SAS and CDK4, and MDM2, respectively, were present in 85% of the soft tissue tumors and in all of the bone tumors. Although chromosome 12 was the only chromosome displaying recurrent amplification in the bone tumors, the soft tissue tumors frequently showed recurrent amplicons mapping to other chromosomes, that is, 1p32, 1q23-24, 3p11-12, 6q24-25 and 20q11-12. Of particular interest, amplicons containing genes involved in the c-jun NH2-terminal kinase/mitogen-activated protein kinase pathway, that is, JUN in 1p32 and MAP3K7IP2 (TAB2) in 6q24-25, were found to be independently amplified in eight of 11 cases with 12q amplification, providing strong support for the notion that aberrant expression of this pathway is an important step in the dedifferentiation of liposarcomas.

Breast and ovarian cancer risks to carriers of the BRCA1 5382insC and 185delAG and BRCA2 6174delT mutations: a combined analysis of 22 population based studies

A recent report estimated the breast cancer risks in carriers of the three Ashkenazi founder mutations to be higher than previously published estimates derived from population based studies. In an attempt to confirm this, the breast and ovarian cancer risks associated with the three Ashkenazi founder mutations were estimated using families included in a previous meta-analysis of populatrion based studies. The estimated breast cancer risks for each of the founder BRCA1 and BRCA2 mutations were similar to the corresponding estimates based on all BRCA1 or BRCA2 mutations in the meta-analysis. These estimates appear to be consistent with the observed prevalence of the mutations in the Ashkenazi Jewish population.

Classification of BRCA1 missense variants of unknown clinical significance

BACKGROUND

BRCA1 is a tumour suppressor with pleiotropic actions. Germline mutations in BRCA1 are responsible for a large proportion of breast-ovarian cancer families. Several missense variants have been identified throughout the gene but because of lack of information about their impact on the function of BRCA1, predictive testing is not always informative. Classification of missense variants into deleterious/high risk or neutral/low clinical significance is essential to identify individuals at risk.

OBJECTIVE

To investigate a panel of missense variants.

METHODS AND RESULTS

The panel was investigated in a comprehensive framework that included (1) a functional assay based on transcription activation; (2) segregation analysis and a method of using incomplete pedigree data to calculate the odds of causality; (3) a method based on interspecific sequence variation. It was shown that the transcriptional activation assay could be used as a test to characterise mutations in the carboxy-terminus region of BRCA1 encompassing residues 1396-1863. Thirteen missense variants (H1402Y, L1407P, H1421Y, S1512I, M1628T, M1628V, T1685I, G1706A, T1720A, A1752P, G1788V, V1809F, and W1837R) were specifically investigated.

CONCLUSIONS

While individual classification schemes for BRCA1 alleles still present limitations, a combination of several methods provides a more powerful way of identifying variants that are causally linked to a high risk of breast and ovarian cancer. The framework presented here brings these variants nearer to clinical applicability.

High-resolution genome-wide array-based comparative genome hybridization reveals cryptic chromosome changes in AML and MDS cases with trisomy 8 as the sole cytogenetic aberration

Although trisomy 8 as the sole chromosome aberration is the most common numerical abnormality in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), little is known about its pathogenetic effects. Considering that +8 is a frequent secondary change in AML/MDS, cryptic--possibly primary--genetic aberrations may occur in cases with trisomy 8 as the apparently single anomaly. However, no such hidden anomalies have been reported. We performed a high-resolution genome-wide array-based comparative genome hybridization (array CGH) analysis of 10 AML/MDS cases with isolated +8, utilizing a 32K bacterial artificial chromosome array set, providing >98% coverage of the genome with a resolution of 100 kb. Array CGH revealed intrachromosomal imbalances, not corresponding to known genomic copy number polymorphisms, in 4/10 cases, comprising nine duplications and hemizygous deletions ranging in size from 0.5 to 2.2 Mb. A 1.8 Mb deletion at 7p14.1, which had occurred prior to the +8, was identified in MDS transforming to AML. Furthermore, a deletion including ETV6 was present in one case. The remaining seven imbalances involved more than 40 genes. The present results show that cryptic genetic abnormalities are frequent in trisomy 8-positive AML/MDS cases and that +8 as the sole cytogenetic aberration is not always the primary genetic event.

Successful treatment of a patient with chronic lymphocytic leukaemia (CLL) presenting with bony metastases with aggressive antibody and chemotherapy

Osteolytic lesions are rare in chronic lymphocytic leukaemia (CLL) and thought to result from Richter's transformation or metastatic disease from nonlymphoid malignancies. We report a patient who presented with a large femoral metastatic lesion and hypercalcaemia caused by CLL itself. Complete remission of CLL with resolution of the osteolytic lesion was achieved with rituximab and cyclophosphamide, adriamycin, oncovin and prednisolone [CHOP (R-CHOP)] combination chemotherapy.

Fine mapping and SNP analysis of positional candidates at the preeclampsia susceptibility locus (PREG1) on chromosome 2

Genome scans in Icelandic, Australian and New Zealand, and Finnish families have localized putative susceptibility loci for preeclampsia/ eclampsia to chromosome 2. The locus mapped in the Australian and New Zealand study (designated PREG1) was thought to be the same locus as that identified in the Icelandic study. In both these studies, two distinct quantitative trait locus (QTL) regions were evident on chromosome 2. Here, we describe our fine mapping of the PREG1 locus and a genetic analysis of two positional candidate genes. Twenty-five additional microsatellite markers were genotyped within the 74-cM linkage region defined by the combined Icelandic and Australian and New Zealand genome scans. The overall position and shape of the localization evidence obtained using nonparametric multipoint analysis did not change from that seen previously in our 10-cM resolution genome scan; two peaks were displayed, one on chromosome 2p at marker D2S388 (107.46 cM) and the other on chromosome 2q at 151.5 cM at marker D2S2313. Using the robust two-point linkage analysis implemented in the Analyze program, all 25 markers gave positive LOD scores with significant evidence of linkage being seen at marker D2S2313 (151.5 cM), achieving a LOD score of 3.37 under a strict diagnostic model. Suggestive evidence of linkage was seen at marker D2S388 (107.46 cM) with a LOD score of 2.22 under the general diagnostic model. Two candidate genes beneath the peak on chromosome 2p were selected for further analysis using public single nucleotide polymorphisms (SNPs) within these genes. Maximum LOD scores were obtained for an SNP in TACR1 (LOD = 3.5) and for an SNP in TCF7L1 (LOD = 3.33), both achieving genome-wide significance. However, no evidence of association was seen with any of the markers tested. These data strongly support the presence of a susceptibility gene on chromosome 2p11-12 and substantiate the possibility of a second locus on chromosome 2q23.

Gene expression profiling of leukemic cell lines reveals conserved molecular signatures among subtypes with specific genetic aberrations

Hematologic malignancies are characterized by fusion genes of biological/clinical importance. Immortalized cell lines with such aberrations are today widely used to model different aspects of leukemogenesis. Using cDNA microarrays, we determined the gene expression profiles of 40 cell lines as well as of primary leukemias harboring 11q23/MLL rearrangements, t(1;19)[TCF3/PBX1], t(12;21)[ETV6/RUNX1], t(8;21)[RUNX1/CBFA2T1], t(8;14)[IGH@/MYC], t(8;14)[TRA@/MYC], t(9;22)[BCR/ABL1], t(10;11)[PICALM/MLLT10], t(15;17)[PML/RARA], or inv(16)[CBFB/MYH11]. Unsupervised classification revealed that hematopoietic cell lines of diverse origin, but with the same primary genetic changes, segregated together, suggesting that pathogenetically important regulatory networks remain conserved despite numerous passages. Moreover, primary leukemias cosegregated with cell lines carrying identical genetic rearrangements, further supporting that critical regulatory pathways remain intact in hematopoietic cell lines. Transcriptional signatures correlating with clinical subtypes/primary genetic changes were identified and annotated based on their biological/molecular properties and chromosomal localization. Furthermore, the expression profile of tyrosine kinase-encoding genes was investigated, identifying several differentially expressed members, segregating with primary genetic changes, which may be targeted with tyrosine kinase inhibitors. The identified conserved signatures are likely to reflect regulatory networks of importance for the transforming abilities of the primary genetic changes and offer important pathogenetic insights as well as a number of targets for future rational drug design.

Insulin-like growth factor-1 (IGF1) genotype predicts breast volume after pregnancy and hormonal contraception and is associated with circulating IGF-1 levels: implications for risk of early-onset breast cancer in young women from hereditary breast cancer families

BRCA1/2 mutations predispose to early-onset breast cancer, especially after oral contraceptive (OC) use and pregnancy. However, the majority of breast cancers might be due to more prevalent low-penetrance genes, which may also modify the risk in BRCA mutation carriers. The absence of the IGF1 19-repeat allele has been associated with high insulin-like growth factor-1 (IGF-1) levels during OC use. High IGF-1 levels are linked to early-onset breast cancer and larger breast volumes in the general population. The goal of this study was to elucidate the relationships between IGF1 genotype, early-onset breast cancer, breast volume, circulating IGF-1 levels and OC use in a prospective cohort of 258 healthy women ⩽40 years old from high-risk breast cancer families. All women completed a questionnaire including information on reproductive factors and OC use. We measured the height, weight, breast volumes and plasma IGF-1 levels. IGF-1 levels were similar among parous and nulliparous women not using OCs. In all, 13% had no IGF1 19-repeat allele. There was an interaction between IGF1 genotype and OC use on IGF-1 levels (P=0.026) in nulliparous women and another interaction between IGF1 genotype and parity on breast volume (P=0.01). Absence of the 19-repeat allele was associated with high IGF-1 levels in nulliparous OC users and with larger breast volumes in parous women and OC users. Incident breast cancers were also more common in women without the 19-repeat allele (log rank P=0.002). Our results suggest that lack of the IGF1 19-repeat allele modifies IGF-1 levels, breast volume and possibly early-onset breast cancer risk after hormone exposure in young high-risk women.