Anne Kallioniemi

Mutations in BRCA1 and BRCA2 genes predispose to breast and ovarian cancer (BC/OC) with a high lifetime risk, whereas mutations in PALB2, CHEK2, ATM, FANCM, RAD51C and RAD51D genes cause a moderately elevated risk. In the Finnish population, recurrent mutations have been identified in all of these genes, the latest being CHEK2 c.319+2T>A and c.444+1G>A. By genotyping 3,156 cases and 2,089 controls, we estimated the frequencies of CHEK2 c.319+2T>A and c.444+1G>A in Finnish BC patients. CHEK2 c.319+2T>A was detected in 0.7% of the patients, and it was associated with a high risk of BC in the unselected patient group (OR = 5.40 [95% CI 1.58–18.45], p = 0.007) and similarly in the familial patient group. CHEK2 c.444+1G>A was identified in 0.1% of all patients. Additionally, we evaluated the combined prevalence of recurrent moderate‐risk gene mutations in 2,487 BC patients, 556 OC patients and 261 BRCA1/2 carriers from 109 families. The overall frequency of the mutations was 13.3% in 1,141 BRCA1/2‐negative familial BC patients, 7.5% in 1,727 unselected BC patients and 7.2% in 556 unselected OC patients. At least one moderate‐risk gene mutation was found in 12.5% of BRCA1 families and 7.1% of BRCA1 index patients, as well as in 17.0% of BRCA2 families and 11.3% of BRCA2 index patients, and the mutations were associated with an additional risk in the BRCA1/2 index patients (OR = 2.63 [1.15–5.48], p = 0.011). These results support gene panel testing of even multiple members of BC families where several mutations may segregate in different individuals.

Human epidermal growth factor receptor HER3 (ErbB3), especially in association with its relative HER2 (ErbB2), is known as a key oncogene in breast tumour biology. Nonetheless, the prognostic relevance of HER3 remains controversial. NEDD4–1 and NRDP1 are signalling molecules closely related to the degradation of HER3 via ubiquitination. NEDD4–1 and NRDP1 have been reported to contribute to HER3-mediated signalling by regulating its localization and cell membrane retention. We studied correlations between HER3, NEDD4–1, and NRDP1 protein expression and their association with tumour histopathological characteristics and clinical outcomes. The prevalence of immunohistochemically detectable expression profiles of HER3 (n = 177), NEDD4–1 (n = 145), and NRDP1 (n = 145) proteins was studied in primary breast carcinomas on archival formalin-fixed paraffin-embedded (FFPE) samples. Clinicopathological correlations were determined statistically using Pearson’s Chi-Square test. The Kaplan-Meier method, log-rank test (Mantel-Cox), and Cox regression analysis were utilized for survival analysis. HER3 protein was expressed in breast carcinomas without association with HER2 gene amplification status. Absence or low HER3 expression correlated with clinically aggressive features, such as triple-negative breast cancer (TNBC) phenotype, basal cell origin (cytokeratin 5/14 expression combined with ER negativity), large tumour size, and positive lymph node status. Low total HER3 expression was prognostic for shorter recurrence-free survival time in HER2-amplified breast cancer (p = 0.004, p = 0.020 in univariate and multivariate analyses, respectively). The majority (82.8%) of breast cancers demonstrated NEDD4–1 protein expression - while only a minor proportion (8.3%) of carcinomas expressed NRDP1. NEDD4–1 and NRDP1 expression were not associated with clinical outcomes in HER2-amplified breast cancer, irrespective of adjuvant trastuzumab therapy. Low HER3 expression is suggested to be a valuable prognostic biomarker to predict recurrence in HER2-amplified breast cancer. Neither NEDD4–1 nor NRDP1 demonstrated relevance in prognostics or in the subclassification of HER2-amplified breast carcinomas.

Nucleocytoplasmic transport is a tightly regulated process carried out by specific transport machinery, the defects of which may lead to a number of diseases including cancer. Karyopherin alpha 7 (KPNA7), the newest member of the karyopherin alpha nuclear importer family, is expressed at a high level during embryogenesis, reduced to very low or absent levels in most adult tissues but re-expressed in cancer cells. We used siRNA-based knock-down of KPNA7 in cancer cell lines, followed by functional assays (proliferation and cell cycle) and immunofluorescent stainings to determine the role of KPNA7 in regulation of cancer cell growth, proper mitosis and nuclear morphology. In the present study, we show that the silencing of KPNA7 results in a dramatic reduction in pancreatic and breast cancer cell growth, irrespective of the endogenous KPNA7 expression level. This growth inhibition is accompanied by a decrease in the fraction of S-phase cells as well as aberrant number of centrosomes and severe distortion of the mitotic spindles. In addition, KPNA7 depletion leads to reorganization of lamin A/C and B1, the main nuclear lamina proteins, and drastic alterations in nuclear morphology with lobulated and elongated nuclei. Taken together, our data provide new important evidence on the contribution of KPNA7 to the regulation of cancer cell growth and the maintenance of nuclear envelope environment, and thus deepens our understanding on the impact of nuclear transfer proteins in cancer pathogenesis.

Bone morphogenetic proteins (BMPs) are a family of growth factors, some of which are known by the name growth and differentiation factor (GDF). BMPs were discovered in the 1960s in an attempt to find factors capable of inducing bone formation. By the end of 1980s, several different BMPs had been found and to date, around 20 members are known. Together with TGFβ, nodal, and activins, they comprise the TGFβ superfamily. BMPs are known to regulate cell fate both in development and adult tissues, and as such they are also involved in many disease states. Understanding the impact of BMPs in these processes requires intimate knowledge of the regulation of the BMP signaling pathway. The intracellular BMP pathway has been studied extensively but the various transcription factors (TFs) necessary for the BMP‐mediated gene expression changes have remained under less scrutiny. Most of the studies have focused on specific TFs in the context of differentiation or development. Varying cell types and BMPs have been used, but no large‐scale studies have yet been performed. Here we aim to summarize the current knowledge on BMP pathway‐related TFs, focusing on those involved in the canonical BMP signaling pathway through the SMAD proteins.

Purpose The FANCM c.5101C>T nonsense mutation was previously found to associate with breast cancer in the Finnish population, especially among triple-negative cases. Here, we studied the prevalence of three other FANCM variants: c.5791C>T, which has been reported to predispose to familial breast cancer, and the c.4025_4026delCT and c.5293dupA variants recently identified in Finnish cancer patients. Methods We genotyped the FANCM c.5791C>T mutation in 4806 invasive breast cancer patients, including BRCA1/2 mutation negative familial cases and unselected cases, and in 2734 healthy population controls from four different geographical areas of Finland. The association of the mutation with breast cancer risk among patient subgroups was statistically evaluated. We further analyzed the combined risk associated with c.5101C>T and c.5791C>T mutations. We also genotyped 526 unselected ovarian cancer patients for the c.5791C>T mutation and 862 familial breast cancer patients for the c.4025_4026delCT and c.5293dupA variants. Results The frequency of the FANCM c.5791C>T mutation was higher among breast cancer cases than in controls (OR 1.94, 95% CI 0.87–4.32, P = 0.11), with a statistically significant association with triple-negative breast cancer (OR 5.14, 95% CI 1.65–16.0, P = 0.005). The combined analysis for c.5101C>T and c.5791C>T carriers confirmed a strong association with breast cancer (OR 1.86, 95% CI 1.32–2.49, P = 0.0002), especially among the triple-negative patients (OR 3.08, 95% CI 1.77–5.35, P = 0.00007). For the other variants, only one additional c.4025_4026delCT carrier and no c.5293dupA carriers were observed. Conclusions These results support the role of FANCM as a breast cancer susceptibility gene, particularly for triple-negative breast cancer.

Several known breast cancer susceptibility genes encode proteins involved in DNA damage response (DDR) and are characterized by rare loss-of-function mutations. However, these explain less than half of the familial cases. To identify novel susceptibility factors, 39 rare truncating mutations, identified in 189 Northern Finnish hereditary breast cancer patients in parallel sequencing of 796 DDR genes, were studied for disease association. Mutation screening was performed for Northern Finnish breast cancer cases (n = 578–1565) and controls (n = 337–1228). Mutations showing potential cancer association were analyzed in additional Finnish cohorts. c.7253dupT in TEX15, encoding a DDR factor important in meiosis, associated with hereditary breast cancer (p = 0.018) and likely represents a Northern Finnish founder mutation. A deleterious c.2715 + 1G > A mutation in the Fanconi anemia gene, FANCD2, was over two times more common in the combined Finnish hereditary cohort compared to controls. A deletion (c.640_644del5) in RNF168, causative for recessive RIDDLE syndrome, had high prevalence in majority of the analyzed cohorts, but did not associate with breast cancer. In conclusion, truncating variants in TEX15 and FANCD2 are potential breast cancer risk factors, warranting further investigations in other populations. Furthermore, high frequency of RNF168 c.640_644del5 indicates the need for its testing in Finnish patients with RIDDLE syndrome symptoms.

Bone morphogenetic protein 4 (BMP4) plays an important role in cancer pathogenesis. In breast cancer, it reduces proliferation and increases migration in a cell line-dependent manner. To characterize the transcriptional mediators of these phenotypes, we performed RNA-seq and DNase-seq analyses after BMP4 treatment in MDA-MB-231 and T-47D breast cancer cells that respond to BMP4 with enhanced migration and decreased cell growth, respectively. The RNA-seq data revealed gene expression changes that were consistent with the in vitro phenotypes of the cell lines, particularly in MDA-MB-231, where migration-related processes were enriched. These results were confirmed when enrichment of BMP4-induced open chromatin regions was analyzed. Interestingly, the chromatin in transcription start sites of differentially expressed genes was already open in unstimulated cells, thus enabling rapid recruitment of transcription factors to the promoters as a response to stimulation. Further analysis and functional validation identified MBD2, CBFB, and HIF1A as downstream regulators of BMP4 signaling. Silencing of these transcription factors revealed that MBD2 was a consistent activator of target genes in both cell lines, CBFB an activator in cells with reduced proliferation phenotype, and HIF1A a repressor in cells with induced migration phenotype. Integrating RNA-seq and DNase-seq data showed that the phenotypic responses to BMP4 in breast cancer cell lines are reflected in transcriptomic and chromatin levels. We identified and experimentally validated downstream regulators of BMP4 signaling that relate to the different in vitro phenotypes and thus demonstrate that the downstream BMP4 response is regulated in a cell type-specific manner.

Background. Breast cancer is the most common cancer in women worldwide. Bone morphogenetic proteins (BMPs), members of the transforming growth factor β superfamily, are known to regulate cell proliferation, differentiation and motility, and have also been shown to be involved in cancer pathogenesis, also in breast cancer. We have previously demonstrated that BMP4 is able to consistently reduce breast cancer cell proliferation through G1 cell cycle arrest and to simultaneously induce migration and invasion in a subset of breast cancer cell lines. Similarly, our clinical data revealed a correlation between elevated BMP4 expression in primary breast tumors and reduced proliferation as well as increased risk of recurrence. The growth inhibitory effects of BMP4 have also been demonstrated in vivo but its possible metastasis promoting functions are less well characterized. Here we set out to investigate this topic using a xenograft mouse model. Methods. MDA-MB-231 breast cancer cells were transduced with a luciferase-expressing vector to allow monitoring of the metastasis formation using bioluminescence imaging. Cells (2 × 10⁵) were injected into the mice intracardially and BMP4 (100 ng/g, 10 animals) or vehicle control (11 animals) was administered through tail vein three times a week. After seven weeks, the mice were sacrificed and metastases collected for histological analyses. Results. The overall amount of metastases was similar in both groups (13 in BMP4-treatment group vs. 12 in control group). There was a slight but non-significant trend of metastases developing earlier in the BMP4 group compared to controls. Most of the metastases occurred in bone and adrenal glands. There were somewhat more metastases in bone in the BMP4-treated mice (10 vs. 7) and more adrenal gland metastases in vehicle-treated animals (5 vs. 1). To assess the contribution of BMP4 to the characteristics of the metastases, the tumors were stained for pSMAD1/5/9 (BMP signaling activation), Ki67 (proliferation), MECA32 (blood vessels), mesenchymal marker vimentin, α-SMA (cancer-associated fibroblasts) and basal markers K5 and K14. No major dissimilarities were observed between the BMP4 and vehicle tumor groups in the staining patterns. Interestingly, the osteoclast marker Tartrate-resistant acid phosphatase (TRAP) was expressed in both groups in the cancer cells whereas Toluidine Blue staining revealed that the bone morphology was not detrimentally affected by BMP4 treatment. Conclusions. Despite its ability to enhance breast cancer cell migration and invasion in vitro, BMP4 does not seem to have a dramatic impact on in vivo metastasis formation, although a small acceleration in appearance of the metastases was observed. However, the limitations of the xenograft model do not allow us to exclude the possible long-term effects of BMP4 that might be more applicable to human situation. Citation Format: Minna Ampuja, Emma L. Alarmo, Philip Owens, Riikka Havunen, Agnes E. Gorska, Harold L. Moses, Anne Kallioniemi. The impact of BMP4 on breast cancer metastasis in an in vivo xenograft mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 629.