iPSC-Derived Hereditary Breast Cancer Model Reveals the BRCA1-Deleted Tumor Niche as a New Culprit in Disease Progression

Tumor progression begins when cancer cells recruit tumor-associated stromal cells to produce a vascular niche, ultimately resulting in uncontrolled growth, invasion, and metastasis. It is poorly understood, though, how this process might be affected by deletions or mutations in the breast cancer type 1 susceptibility (BRCA1) gene in patients with a lifetime risk of developing breast and/or ovarian cancer. To model the BRCA1-deleted stroma, we first generated induced pluripotent stem cells (iPSCs) from patients carrying a germline deletion of exon 17 of the BRCA1 gene (BRCA1+/− who, based on their family histories, were at a high risk for cancer. Using peripheral blood mononuclear cells (PBMCs) of these two affected family members and two normal (BRCA1+/+) individuals, we established a number of iPSC clones via non-integrating Sendai virus-based delivery of the four OCT4, SOX2, KLF4, and c-MYC factors. Induced mesenchymal stem cells (iMSCs) were generated and used as normal and pathological stromal cells. In transcriptome analyses, BRCA1+/− iMSCs exhibited a unique pro-angiogenic signature: compared to non-mutated iMSCs, they expressed high levels of HIF-1α, angiogenic factors belonging to the VEGF, PDGF, and ANGPT subfamilies showing high angiogenic potential. This was confirmed in vitro through the increased capacity to generate tube-like structures compared to BRCA1+/+ iMSCs and in vivo by a matrigel plug angiogenesis assay where the BRCA1+/− iMSCs promoted the development of an extended and organized vessel network. We also reported a highly increased migration capacity of BRCA1+/− iMSCs through an in vitro wound healing assay that correlated with the upregulation of the periostin (POSTN). Finally, we assessed the ability of both iMSCs to facilitate the engraftment of murine breast cancer cells using a xenogenic 4T1 transplant model. The co-injection of BRCA1+/− iMSCs and 4T1 breast cancer cells into mouse mammary fat pads gave rise to highly aggressive tumor growth (2-fold increase in tumor volume compared to 4T1 alone, p = 0.01283) and a higher prevalence of spontaneous metastatic spread to the lungs. Here, we report for the first time a major effect of BRCA1 haploinsufficiency on tumor-associated stroma in the context of BRCA1-associated cancers. The unique iMSC model used here was generated using patient-specific iPSCs, which opens new therapeutic avenues for the prevention and personalized treatment of BRCA1-associated hereditary breast cancer.

Breast-cancer risk in families with mutations in PALB2

BACKGROUND

Germline loss-of-function mutations in PALB2 are known to confer a predisposition to breast cancer. However, the lifetime risk of breast cancer that is conferred by such mutations remains unknown.

METHODS

We analyzed the risk of breast cancer among 362 members of 154 families who had deleterious truncating, splice, or deletion mutations in PALB2. The age-specific breast-cancer risk for mutation carriers was estimated with the use of a modified segregation-analysis approach that allowed for the effects of PALB2 genotype and residual familial aggregation.

RESULTS

The risk of breast cancer for female PALB2 mutation carriers, as compared with the general population, was eight to nine times as high among those younger than 40 years of age, six to eight times as high among those 40 to 60 years of age, and five times as high among those older than 60 years of age. The estimated cumulative risk of breast cancer among female mutation carriers was 14% (95% confidence interval [CI], 9 to 20) by 50 years of age and 35% (95% CI, 26 to 46) by 70 years of age. Breast-cancer risk was also significantly influenced by birth cohort (P<0.001) and by other familial factors (P=0.04). The absolute breast-cancer risk for PALB2 female mutation carriers by 70 years of age ranged from 33% (95% CI, 25 to 44) for those with no family history of breast cancer to 58% (95% CI, 50 to 66) for those with two or more first-degree relatives with breast cancer at 50 years of age.

CONCLUSIONS

Loss-of-function mutations in PALB2 are an important cause of hereditary breast cancer, with respect both to the frequency of cancer-predisposing mutations and to the risk associated with them. Our data suggest the breast-cancer risk for PALB2 mutation carriers may overlap with that for BRCA2 mutation carriers. (Funded by the European Research Council and others.).

Mutation analysis of the ERCC4/FANCQ gene in hereditary breast cancer

The ERCC4 protein forms a structure-specific endonuclease involved in the DNA damage response. Different cancer syndromes such as a subtype of Xeroderma pigmentosum, XPF, and recently a subtype of Fanconi Anemia, FA-Q, have been attributed to biallelic ERCC4 gene mutations. To investigate whether monoallelic ERCC4 gene defects play some role in the inherited component of breast cancer susceptibility, we sequenced the whole ERCC4 coding region and flanking untranslated portions in a series of 101 Byelorussian and German breast cancer patients selected for familial disease (set 1, n = 63) or for the presence of the rs1800067 risk haplotype (set 2, n = 38). This study confirmed six known and one novel exonic variants, including four missense substitutions but no truncating mutation. Missense substitution p.R415Q (rs1800067), a previously postulated breast cancer susceptibility allele, was subsequently screened for in a total of 3,698 breast cancer cases and 2,868 controls from Germany, Belarus or Russia. The Gln415 allele appeared protective against breast cancer in the German series, with the strongest effect for ductal histology (OR 0.67; 95%CI 0.49; 0.92; p = 0.003), but this association was not confirmed in the other two series, with the combined analysis yielding an overall Mantel-Haenszel OR of 0.94 (95% CI 0.81; 1.08). There was no significant effect of p.R415Q on breast cancer survival in the German patient series. The other three detected ERCC4 missense mutations included two known rare variants as well as a novel substitution, p.E17V, that we identified on a p.R415Q haplotype background. The p.E17V mutation is predicted to be probably damaging but was present in just one heterozygous patient. We conclude that the contribution of ERCC4/FANCQ coding mutations to hereditary breast cancer in Central and Eastern Europe is likely to be small.

Etiology of familial breast cancer with undetected BRCA1 and BRCA2 mutations: clinical implications

BACKGROUND

Familial breast cancer accounts for 20-30 % of all breast cancer cases. Mutations in the BRCA1 and BRCA2 genes account for the majority of high risk families with both early onset breast cancer and ovarian cancer. Most of the families with less than six breast cancer cases and no ovarian cancer do not carry BRCA1 or BRCA2 mutations that can be detected using routine sequencing protocols. Here, we aimed to review the etiology of familial breast cancer in cases without BRCA1 and BRCA2 mutations.

RESULTS

After excluding BRCA1 and BRCA2 mutations, factors proposed to contribute to familial breast cancer include: chance clustering of apparently sporadic cases, shared lifestyle, monogenic inheritance, i.e., dominant gene mutations associated with a high risk (TP53, PTEN, STK11), dominant gene mutations associated with a relatively low risk (ATM, BRIP1, RLB2), recessive gene mutations associated with horizontal inheritance patterns (sister-sister), and polygenic inheritance where susceptibility to familial breast cancer is thought to be conferred by a large number of low risk alleles.

CONCLUSIONS

Current evidence suggests that in the majority of cases with BRCA1 and BRCA2 negative familial breast cancer the etiology is due to interactions of intermediate or low risk alleles with environmental and lifestyle factors. Thus, a careful selection of patients submitted to genetic testing is needed. Clearly, further research is required to fully elucidate the etiology of non-BRCA familial breast cancer.

Exploring the underlying hormonal mechanisms of prenatal risk factors for breast cancer: a review and commentary

Prenatal factors have been hypothesized to influence subsequent breast cancer development. Directly evaluating the associations of in utero exposures with risk, however, presents several methodologic and theoretical challenges, including the long induction period between exposure and disease and the lack of certainty regarding the critical timing of exposure. Indirect evaluation of these associations has been achieved by use of proxies such as gestational and neonatal characteristics. Evidence suggests that preeclampsia is associated with a reduced breast cancer risk, whereas high birth weight and dizygotic twinning seem associated with an increased risk. Asians born in Asia have substantially lower breast cancer risks than women born in the West. Although data thus far are few, what exists is not consistent with a unifying hypothesis for a particular biological exposure (such as estrogens or androgens) during pregnancy as mediating the observed associations between pregnancy factors and breast cancer risk. This suggests that additional studies of prenatal factors should seek to broaden the range of hormones, growth, and other endocrine factors that are evaluated in utero. Once candidate biomarkers are identified, assessing them with respect to breast cancer and with intermediate end points in carcinogenesis should be a priority. In addition, investigations should explore the possibility that in utero exposures may not act directly on the breast, but may alter other physiologic pathways such as hormone metabolism that have their effect on risk later in life.

Familiäre Brustkrebserkrankung: klinische Grundlagen und Früherkennung

About 10 % of breast cancers are "hereditary", i. e. caused by a pathogenic mutation in one of the "breast and ovarian cancer susceptibility genes" (BRCA). The BRCA genes 1 and 2 identified to date follow an autosomal dominant inheritance pattern. A clustering of breast cancer in a family without a documented mutation and without a recognizable inheritance pattern is usually referred to as "familial cancer". A distinction between hereditary and familial is difficult in the individual case because not all of the genetic mutations that cause breast cancer susceptibility are known and thus amenable to genetic testing. Women who are suspected of or documented as carrying a breast cancer susceptibility gene face a substantially increased lifetime risk of breast (and ovarian) cancer ranging from 60-80 % for breast and up to 40 % for ovarian cancer. In addition, the disease develops at a young age (the personal risk starts increasing at age 25; average age of diagnosis is 40). BRCA-associated breast cancers tend to exhibit histologic and histochemical evidence of aggressive biologic behavior (usually grade 3, receptor negative) with very fast growth rates. In particular BRCA1-associated breast cancer may be indistinguishable from fibroadenomas: they appear as well-defined, roundish, hypoechoic masses with smooth borders, without posterior acoustic shadowing on ultrasound, without associated microcalcifications on mammography, and with strong wash-out phenomenon on breast MRI. This article reviews the different options that exist for the prevention of familial or hereditary breast cancer and the specific difficulties that are associated with the radiological diagnosis of these cancers. Lastly, an overview is given of the current evidence regarding the effectiveness of the different imaging modalities for early diagnosis of familial and hereditary breast cancer.

Report of a nipple nevus and an overview of accessory mammary tissue

Supernumerary nipples, also known as accessory nipples, are the most frequently encountered congenital anomaly of the breast. Once associated with fertility or divine powers, they are now widely held to be of cosmetic significance only. During the past 20 years, however, there has been a steady number of articles reporting the suspected association of supernumerary nipples with numerous benign and malignant medical conditions. We describe a previously unreported accessory nipple variant occurring as a nevoid nodule surmounting an otherwise normal primary nipple. The patient was otherwise healthy. The embryogenesis of this anomaly is hypothesized to result from in utero nipple dichotomy, rather than a failure of regression along the embryonic milk line.

Congenital epulis and granular cell tumor: a histologic and immunohistochemical study

OBJECTIVES

Although it is now reasonably certain that granular cell tumors derive from Schwann cells, the histogenesis of congenital epulis, which is largely isomorphic with granular cell tumor, remains unclear. A study was undertaken to compare the immunophenotype of these tumors with particular emphasis on the expression of matrix proteins and macrophage markers because such information is not available in the literature.

STUDY DESIGN

Four granular cell tumors and two congenital epulis were immunostained with a panel of 29 antibodies. Two congenital epulis and one granular cell tumor were investigated by electron microscopy, the latter also by immunoelectron microscopy.

RESULTS

Many similarities in immunostaining were found, for example, both tumor types were CD68+, Ki-M1P+, lysozyme-, vimentin+, fibronectin+, laminin+, lectin PHAE+, and lectin WGA+. However, differences were also noted, for example, granular cell tumor was always S100 protein+, but only one congenital epulis case was reactive (weak reactivity after microwave treatment), and staining with the proliferation markers anti-proliferating cell nuclear antigen and MIB 1 was found only in congenital epulis. Both tumor types exhibited pericellular and diffuse cytoplasmic staining for fibronectin and laminin.

CONCLUSIONS

The hypothesis that congenital epulis and granular cell tumor would exhibit similar reactivity for macrophage markers was confirmed: both were reactive with anti-CD68 and Ki-M1P and nonreactive with MAC387, anti-lysozyme, and 3A5. Intracytoplasmic staining for fibronectin and laminin, which has not been described previously in these tumors, appears to be a characteristic feature common to both tumors. This finding suggests that there could be a disturbance of synthesis and secretion of extracellular matrix proteins or a derangement of their receptor systems. This theory could be supported by the finding of intracytoplasmic CD49e-positive material in two cases.

Vascular tumors of the breast. III. Angiomatosis

This report describes three female patients who were treated for diffuse vascular lesions of the breast. The lesion was congenital in one patient. Two were adults (40 and 59 years old). Each presented with a mass within the breast. Microscopically, the tumors were composed of vascular channels growing diffusely in breast parenchyma. The vessels were lined by flat, inconspicuous endothelium with sparse supporting mural tissue virtually devoid of smooth muscle. The lesions consisted of hemangiomatous (erythrocyte-containing) and lymphangiomatous (seemingly empty) channels with lymphoid aggregates. This combination of a mixed pattern of vessels and diffuse growth is similar to that seen in lesions that have been called angiomatosis in other anatomic sites. Because the microscopic distinction between very orderly angiosarcomas and angiomatosis may be difficult, complete excision of the tumor is necessary. For bulky lesions, this may require mastectomy. In one patient congenital angiomatosis has persisted and recurred twice in the mammary region over 39 years. The other two patients remain well 3 years after local excision and 2 years and 4 months after mastectomy, respectively. Angiomatosis of the breast has not exhibited clinically malignant behavior since no metastases have been observed.