Åke Borg

PURPOSE: Patients with breast cancer in Ethiopia are generally diagnosed with late-stage disease, and there is a high proportion of young female and male patients. The role of genetic predisposition is yet unknown in this setting. To increase the knowledge about hereditary breast cancer in Ethiopia, this study investigated germline pathogenic variants (PVs) in breast cancer–predisposing genes in a high-risk cohort of young women and men with breast cancer. MATERIALS AND METHODS: One hundred women (age 18-39) and men (all ages) diagnosed with breast cancer at the Tikur Anbessa Specialized Hospital, Addis Ababa, were included. Basic patient and tumor characteristics, and family history were collected, and blood samples drawn. DNA was extracted locally before transport to Lund University, Sweden, for DNA analysis using next-generation sequencing. Type and frequency of PVs in breast cancer–related genes ( ATM, BARD1, BRCA1, BRCA2, CDH1, CHEK2, PALB2, PTEN, RAD51C, RAD51D, STK11 , and TP53 ) were analyzed. RESULTS: A high proportion of the 89 study participants with successful genetic analysis carried PVs in breast cancer susceptibility genes (23.6%; 95% CI 15.2 to 33.8). In total, 22 PVs were detected in BRCA1 (n = 7), BRCA2 (n = 8), PALB2 (n = 4), BARD1 (n = 1), PTEN (n = 1), and ATM (n = 1). Potential founder variants and two novel PVs were found ( BRCA1 c.5278-864_5332+621del and PALB2 c.1169_1170del). CONCLUSION: Genetic predisposition plays an important role among young women and men in the study setting, with nearly one in four patients carrying a PV. The results call for further research and interventions targeting individuals at high risk, with the long-term potential of reduced morbidity and mortality.

There are two text errors in the original publication

Background: Homologous recombination deficiency (HRD) originating from inactivation of genes like BRCA1 / BRCA2 is a targetable abnormality common in triple-negative breast cancer (TNBC). In estrogen-receptor (ER)-positive HER2-negative (ERpHER2n) breast cancer (BC), HRD prevalence and clinical impact are unclear. Methods: We analyzed 502 ERpHER2n tumors from patients recruited via the population-representative Swedish SCAN-B study by whole genome sequencing (WGS), defining mutational signatures-based HRD, as well as matched transcriptional, DNA methylation, clinicopathological, adjuvant treatment, and outcome data. Results: We show that HRD is much less frequent in ERpHER2n BC (8.4%) compared to TNBC, though induced by similar genetic/epigenetic mechanisms acting on mainly BRCA1 / BRCA2 / RAD51C / PALB2 together, providing a plausible HR-inactivation mechanism for 71.4% of HRD tumors. Our modelled estimate of HRD in Western European/Nordic BC is ~10-13%. HRD tumors were observed across all PAM50 gene expression subtypes with the exception of Luminal A tumors ( < 1%) and did not exhibit a unique, defining transcriptional or DNA methylation profile. While HRD status was not statistically associated with differences in patient outcome for patients treated with combined chemotherapy and endocrine therapy, a nonsignificant trend of poorer outcome for patients with HRD tumors was observed for patients treated with adjuvant endocrine therapy only. Conclusions: ERpHER2n HRD tumors show features of aggressive disease, but do not display a distinct transcriptional or DNA methylation profile that clearly differentiates them from HR-proficient tumors. Though numbers are limited, we present early evidence that HRD stratification by WGS could impact therapeutic strategies, as HRD BCs trended to poorer outcomes when not treated with chemotherapy.

Triple-negative breast cancer (TNBC) is a clinically challenging and molecularly heterogenous breast cancer subgroup. Here, we investigate the DNA methylation landscape of TNBC. By analyzing tumor methylome profiles and accounting for the genomic context of CpG methylation, we divide TNBC into two epigenetic subtypes corresponding to a Basal and a non-Basal group, in which characteristic transcriptional patterns are correlated with DNA methylation of distal regulatory elements and epigenetic regulation of key steroid response genes and developmental transcription factors. Further subdivision of the Basal and non-Basal subtypes identifies subgroups transcending genetic and proposed TNBC mRNA subtypes, demonstrating widely differing immunological microenvironments, putative epigenetically-mediated immune evasion strategies, and a specific metabolic gene network in older patients that may be epigenetically regulated. Our study attempts to target the epigenetic backbone of TNBC, an approach that may inform future studies regarding tumor origins and the role of the microenvironment in shaping the cancer epigenome.

ER-positive/HER2-negative (ERpHER2n) breast cancer classified as PAM50 HER2-enriched (ERpHER2n-HER2E) represents a small high-risk patient subgroup. In this study, we investigate genomic, transcriptomic, and clinical features of ERpHER2n-HER2E breast tumors using two primary ERpHER2n cohorts comprising a total of 5640 patients. We show that ERpHER2n-HER2E tumors exhibit aggressive clinical features and poorer clinical outcomes compared to Luminal A and Luminal B tumors. Furthermore, ERpHER2n-HER2E breast cancer does not consist of misclassified or HER2-low cases, has little impact of ERBB2, is highly proliferative and less ER dependent than other luminal subtypes. It is not an obvious biological entity but is nevertheless associated with potentially targetable molecular features, notably a high immune response and high FGFR4 expression. Strikingly, molecular features that define the HER2E subtype in luminal disease are also consistent in HER2-positive disease, including an epigenetic mechanism for high FGFR4 expression in breast cancer.

Obesity is associated with an increased risk of developing breast cancer (BC) and worse prognosis in BC patients, yet its impact on BC biology remains understudied in humans. This study investigates how the biology of untreated primary BC differs according to patients’ body mass index (BMI) using data from >2,000 patients. We identify several genomic alterations that are differentially prevalent in overweight or obese patients compared to lean patients. We report evidence supporting an ageing accelerating effect of obesity at the genetic level. We show that BMI-associated differences in bulk transcriptomic profile are subtle, while single cell profiling allows detection of more pronounced changes in different cell compartments. These analyses further reveal an elevated and unresolved inflammation of the BC tumor microenvironment associated with obesity, with distinct characteristics contingent on the estrogen receptor status. Collectively, our analyses imply that obesity is associated with an inflammaging-like phenotype. We conclude that patient adiposity may play a significant role in the heterogeneity of BC and should be considered for BC treatment tailoring.

Worldwide, there is a growing proportion of women who are overweight or obese. While obesity has been associated with an increased risk of developing breast cancer (BC) and worse prognosis in BC patients, yet the impact of adiposity (abnormal or excess body fat) on BC biology remains understudied in humans. This retrospective study aimed to investigate how the biology of primary BC would differ according to patients’ body mass index (BMI). We examined clinicopathological data (including BMI at the time of diagnosis) and molecular data (including genomic, bulk and single-cell transcriptomic data) of treatment-naïve (early stage) BC patients from five cohorts (N = 2071). We identified several genomic alterations considered actionable or of potential clinical relevance which had a different prevalence in overweight or obese patients compared to lean patients, for instances, less PIK3CA gene mutations, and more CCND1, CCNE1 and IGFR1 amplifications. Moreover, we found evidence supporting an ageing accelerating effect of obesity at the genetic level, through its association with an age-associated mutational signature. We showed that BMI-associated differences in transcriptomic profile were subtle at the bulk resolution while single cell profiling allowed detection of more pronounced changes in different cell compartments. Investigation at the single cell resolution revealed an elevated and unresolved inflammation of the BC tumor microenvironment (TME) associated with obesity, which had distinct characteristics contingent on the estrogen receptor status. Collectively, analyses at both genomic and transcriptomic levels implied that obesity is associated with an inflammaging-like phenotype of the TME. Our results indicate that patient adiposity might play a significant role in the heterogeneity of BC and should be considered in the context of precision medicine.

In early breast cancer, a preoperative core-needle biopsy (CNB) is vital to confirm the malignancy of suspected lesions and for assessing the expression of treatment predictive and prognostic biomarkers in the tumor to choose the optimal treatments, emphasizing the importance of obtaining reliable results when biomarker status is assessed on a CNB specimen. This study aims to determine the concordance between biomarker status assessed as part of clinical workup on a CNB compared to a medically untreated surgical specimen. Paired CNB and surgical specimens from 259 patients that were part of the SCAN-B cohort were studied. The concordance between immunohistochemical (IHC) and gene expression (GEX) based biomarker status was investigated. Biomarkers of interest included estrogen receptor (ER; specifically, the alpha variant), progesterone receptor (PgR), Ki67, HER2, and tumor molecular subtype. In general, moderate to very good correlation in biomarker status between the paired CNB and surgical specimens was observed for both IHC assessment (83–99% agreement, kappa range 0.474–0.917) and GEX assessment (70–97% agreement, kappa range 0.552–0.800), respectively. However, using IHC, 52% of cases with low Ki67 status in the CNB shifted to high Ki67 status in the surgical specimen (McNemar’s p = 0.011). Similarly, when using GEX, a significant shift from negative to positive ER (47%) and from low to high Ki67 (16%) was observed between the CNB and surgical specimen (McNemar’s p = 0.027 and p = 0.002 respectively). When comparing biomarker status between different techniques (IHC vs. GEX) performed on either CNBs or surgical specimens, the agreement in ER, PgR, and HER2 status was generally over 80% in both CNBs and surgical specimens (kappa range 0.395–0.708), but Ki67 and tumor molecular subtype showed lower concordance levels between IHC and GEX (48–62% agreement, kappa range 0.152–0.398). These results suggest that both the techniques used for collecting tissue samples and analyzing biomarker status have the potential to affect the results of biomarker assessment, potentially also impacting treatment decisions and patient survival outcomes.

Multigene assays for molecular subtypes and biomarkers can aid management of early invasive breast cancer. Using RNA-sequencing we aimed to develop single-sample predictor (SSP) models for clinical markers, subtypes, and risk of recurrence (ROR). A cohort of 7743 patients was divided into training and test set. We trained SSPs for subtypes and ROR assigned by nearest-centroid (NC) methods and SSPs for biomarkers from histopathology. Classifications were compared with Prosigna in two external cohorts (ABiM, n = 100 and OSLO2-EMIT0, n = 103). Prognostic value was assessed using distant recurrence-free interval. Agreement between SSP and NC for PAM50 (five subtypes) was high (85%, Kappa = 0.78) for Subtype (four subtypes) very high (90%, Kappa = 0.84) and for ROR risk category high (84%, Kappa = 0.75, weighted Kappa = 0.90). Prognostic value was assessed as equivalent and clinically relevant. Agreement with histopathology was very high or high for receptor status, while moderate for Ki67 status and poor for Nottingham histological grade. SSP and Prosigna concordance was high for subtype (OSLO-EMIT0 83%, Kappa = 0.73 and ABiM 80%, Kappa = 0.72) and moderate and high for ROR risk category (68 and 84%, Kappa = 0.50 and 0.70, weighted Kappa = 0.70 and 0.78). Pooled concordance for emulated treatment recommendation dichotomized for chemotherapy was high (85%, Kappa = 0.66). Retrospective evaluation suggested that SSP application could change chemotherapy recommendations for up to 17% of postmenopausal ER+/HER2-/N0 patients with balanced escalation and de-escalation. Results suggest that NC and SSP models are interchangeable on a group-level and nearly so on a patient level and that SSP models can be derived to closely match clinical tests.

An estimated 5-10% of breast cancer cases carry germline mutations in genes associated with a moderate to strong breast cancer risk, like BRCA1 and BRCA2. These mutations can influence disease onset, progression, biology of the tumor, potential for therapy, risk of recurrence and cancer risk of close relatives. This warrants clinical germline screening for such gene variants according to national guidelines on patient selection. In this study we aimed to molecularly and clinicopathologically contrast clinically screened patients and their tumors against unscreened patients. For this we used a population-based breast cancer cohort from southern Sweden with 6660 patients (14% of which had been screened) with accompanying RNA-sequencing and clinicopathological registry data. Screening subsets were analyzed within five clinically relevant breast cancer subgroups based on hormone receptor and lymph node status. Among other features, we investigated clinicopathological characteristics, risk of tumor recurrence, survival outcomes, tumor proliferation markers, immune cell content, genes differentially expressed and the pathways in which they were involved. Most differences were found in the triple negative breast cancer (TNBC) subgroup: when compared to patients that had not been screened, the screened subset contained younger individuals showing better overall survival, more proliferative tumors with upregulated genes that belong to DNA replication and double-strand break repair processes, lower proportion of M2 macrophages and higher proportion of T-helper 2 cells. As so, Swedish screening guidelines divide TNBC cases into two separate subsets possibly by selecting distinct underlying biological and mutational mechanisms associated with DNA repair deficiency (e.g., through BRCA1/2-deficiency), a disparity not seen in other breast cancer clinical subgroups. Understanding the molecular landscape of defined screening populations may improve future guideline updates, which in turn would also improve patient and resource handling. Citation Format: Deborah F. Nacer de Oliveira, Johan Vallon-Christersson, Hans Ehrencrona, Anders Kvist, Åke Borg, Johan Staaf. Molecular characteristics of breast cancer patients subjected to screening for germline predisposition in a population-based observational study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1434.