Cellular and molecular mechanisms of breast cancer susceptibility.

There is a plethora of recognized risk factors for breast cancer (BC) with poorly understood or speculative biological mechanisms. The lack of prevention options highlights the importance of understanding the mechanistic basis of cancer susceptibility and finding new targets for breast cancer prevention. Until now, we have understood risk and cancer susceptibility primarily through the application of epidemiology and assessing outcomes in large human cohorts. Relative risks are assigned to various human behaviors and conditions, but in general the associations are weak and there is little understanding of mechanism. Aging is by far the greatest risk factor for BC, and there are specific forms of inherited genetic risk that are well-understood to cause BC. We propose that bringing focus to the biology underlying these forms of risk will illuminate biological mechanisms of BC susceptibility.

Laser assisted pulmonary metastasectomy promises a low local recurrence rate.

Pulmonary metastasectomy (PM) is consensually performed in a parenchyma-sparing manner to preserve functionally healthy lung tissue. However, this may increase the risk of local recurrence at the surgical margin. Laser assisted pulmonary metastasectomy (LPM) is a relatively recent innovation that is especially useful to resect multiple metastatic pulmonary nodules. In this study we investigated the rate of local recurrence after LPM and evaluated the influence of various clinical and pathological factors on local recurrence. Retrospectively, a total of 280 metastatic nodules with different histopathological entities were studied LPM from 2010 till 2018. All nodules were resected via diode-pumped neodymium: yttrium-aluminum-garnet (Nd:YAG) 1,318 nm laser maintaining a safety margin of 5 mm. Patients included were observed on average for 44 ± 17 months postoperatively. Local recurrence at the surgical margin following LPM was found in 9 nodules out of 280 nodules (3.21%). Local recurrence at the surgical margin occurred after 20 ± 8.5 months post operation. Incomplete resection (p = < 0.01) and size of the nodule (p = < 0.01) were associated with significantly increased risk of local recurrence at the surgical margin. Histology of the primary disease showed no impact on local recurrence. Three and five-year survival rates were 84% and 49% respectively. Following LPM, the rate of local recurrence is low. This is influenced by the size of the metastatic nodules and completeness of the resection. Obtaining a safety margin of 5 mm seems to be sufficient, larger nodules require larger safety margins.

Configurational entropy is an intrinsic driver of tissue structural heterogeneity.

Tissues comprise ordered arrangements of cells that can be surprisingly disordered in their details. How the properties of single cells and their microenvironment contribute to the balance between order and disorder at the tissue-scale remains poorly understood. Here, we address this question using the self-organization of human mammary organoids as a model. We find that organoids behave like a dynamic structural ensemble at the steady state. We apply a maximum entropy formalism to derive the ensemble distribution from three measurable parameters - the degeneracy of structural states, interfacial energy, and tissue activity (the energy associated with positional fluctuations). We link these parameters with the molecular and microenvironmental factors that control them to precisely engineer the ensemble across multiple conditions. Our analysis reveals that the entropy associated with structural degeneracy sets a theoretical limit to tissue order and provides new insight for tissue engineering, development, and our understanding of disease progression.

Evidence for accelerated aging in mammary epithelia of women carrying germline BRCA1 or BRCA2 mutations.

During aging in the human mammary gland, luminal epithelial cells lose lineage fidelity by expressing markers normally expressed in myoepithelial cells. We hypothesize that loss of lineage fidelity is a general manifestation of epithelia that are susceptible to cancer initiation. In the present study, we show that histologically normal breast tissue from younger women who are susceptible to breast cancer, as a result of harboring a germline mutation in BRCA1, BRCA2 or PALB2 genes, exhibits hallmarks of accelerated aging. These include proportionately increased luminal epithelial cells that acquired myoepithelial markers, decreased proportions of myoepithelial cells and a basal differentiation bias or failure of differentiation of cKit+ progenitors. High-risk luminal and myoepithelial cells are transcriptionally enriched for genes of the opposite lineage, inflammatory- and cancer-related pathways. We have identified breast-aging hallmarks that reflect a convergent biology of cancer susceptibility, regardless of the specific underlying genetic or age-dependent risk or the associated breast cancer subtype.

Breast-Specific Molecular Clocks Comprised of ELF5 Expression and Promoter Methylation Identify Individuals Susceptible to Cancer Initiation.

A robust breast cancer prevention strategy requires risk assessment biomarkers for early detection. We show that expression of ELF5, a transcription factor critical for normal mammary development, is downregulated in mammary luminal epithelia with age. DNA methylation of the ELF5 promoter is negatively correlated with expression in an age-dependent manner. Both ELF5 methylation and gene expression were used to build biological clocks to estimate chronological ages of mammary epithelia. ELF5 clock-based estimates of biological age in luminal epithelia from average-risk women were within three years of chronological age. Biological ages of breast epithelia from BRCA1 or BRCA2 mutation carriers, who were high risk for developing breast cancer, suggested they were accelerated by two decades relative to chronological age. The ELF5 DNA methylation clock had better performance at predicting biological age in luminal epithelial cells as compared with two other epigenetic clocks based on whole tissues. We propose that the changes in ELF5 expression or ELF5-proximal DNA methylation in luminal epithelia are emergent properties of at-risk breast tissue and constitute breast-specific biological clocks. PREVENTION RELEVANCE: ELF5 expression or DNA methylation level at the ELF5 promoter region can be used as breast-specific biological clocks to identify women at higher than average risk of breast cancer.