Abstract 4807: BACH1 proline hydroxylation regulates the hypoxia response and metastasis in triple negative breast cancer

Hypoxia is an important hallmark of aggressive solid tumors. Here we show that the pro-metastatic BTB and CNC homology 1 (BACH1) transcription factor is prolyl-hydroxylated by the HIF Prolyl Hydroxylase 1 (PHD1) in an oxygen-dependent manner. Using mass spectrometry, we identified two major prolyl hydroxylation sites in BACH1 and demonstrate that prolyl hydroxylation increased protein turnover in normoxia. Notably, a clinically relevant BACH1 mutant (BACH1M) resistant to hydroxylation displays enhanced BACH1 DNA binding capacity. Triple-negative breast cancer (TNBC) cells expressing BACH1M showed higher invasion in vitro and increased metastasis in vivo. Loss of BACH1 reduced the cellular transcriptional hypoxic response. Under hypoxia, BACH1 increases chromatin accessibility and gene expression through chromatin remodeling involving direct BACH1 binding and indirect epigenetic regulation. These results indicate that hypoxia stabilizes and enhances the pro-metastatic transcriptional activity of BACH1 through loss of prolyl hydoxylation in TNBC. Our findings identify BACH1 as an oxygen sensitive effector of the hypoxia response and a clinically relevant target for attenuating hypoxia induced, pro-metastatic signaling and therapeutic resistance in cancers.

Citation Format: Long Chi Nguyen, Christopher Dann, Dongbo Yang, Emily Shi, Thomas Li, Joseph Wynne, Letícia Stock, Madeline Henn, Zeyu Qiao, Andrea Valdespino, Raven Watson, Wenchao Liu, Lydia Robinson-Mailman, Galina Khramtsova, Mitsuyo Matsumoto, Raymond Moellering, Olufunmilayo I. Olopade, Kazuhiko Igarashi, Marsha R. Rosner. BACH1 proline hydroxylation regulates the hypoxia response and metastasis in triple negative breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4807.

Concentration-Dependent Thermodynamic Analysis of the Partition Process of Small Ligands into Proteins

In the category of functional low-affinity interactions, small ligands may interact with multiple protein sites in a highly degenerate manner. Better conceived as a partition phenomenon at the molecular interface of proteins, such low-affinity interactions appear to be hidden to our current experimental resolution making their structural and functional characterization difficult in the low concentration regime of physiological processes. Characterization of the partition phenomenon under higher chemical forces could be a relevant strategy to tackle the problem provided the results can be scaled back to the low concentration range. Far from being trivial, such scaling demands a concentration-dependent understanding of self-interactions of the ligands, structural perturbations of the protein, among other molecular effects. Accordingly, we elaborate a novel and detailed concentration-dependent thermodynamic analysis of the partition process of small ligands aiming at characterizing the stability and structure of the dilute phenomenon from high concentrations. In analogy to an “aggregate” binding constant of a small molecule over multiple sites of a protein receptor, the model defines the stability of the process as a macroscopic equilibrium constant for the partition number of ligands that can be used to analyze biochemical and functional data of two-component systems driven by low-affinity interactions. Acquisition of such modeling-based structural information is expected to be highly welcome by revealing more traceable protein-binding spots for non-specific ligands.

Abstract 118: BACH1 is an oxygen-sensitive mediator of the hypoxia response in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive solid tumor characterized by a hypoxic phenotype that promotes metastatic progression and resistance to therapy. The canonical cellular response to hypoxia is largely driven by hypoxia inducible factors (HIFs) that stimulate transcription of genes related to angiogenesis, cancer stem cells, cell survival, and glucose and iron metabolism. There is growing evidence that several factors, in addition to HIFs, contribute to the tumor hypoxia response. Thus, identifying novel mechanisms that regulate this cellular response in addition to the HIFs is key to our understanding of hypoxia and could have direct clinical impact. High expression of BTB and CNC homology 1 (BACH1), a heme-regulated bZIP transcription factor, drives metastatic progression in various cancers including TNBC. While BACH1 has been shown to be induced under hypoxia in some cell lines, its regulation and role in hypoxia signaling, specifically with regards to cancer cells, is poorly understood. Here we report a novel regulatory pathway of the tumor hypoxia response in TNBC. We show that BACH1 is post-translationally prolyl-hydroxylated by the HIF prolyl-hydroxylases (PHDs) in an oxygen-dependent and NRF2/HMOX1-independent manner. Hypoxic exposure thus stabilizes BACH1 protein and enhances its DNA binding activity at loci of both canonical and hypoxia-specific downstream targets. We further show that BACH1 regulates the hypoxia response by promoting expression of both HIF-dependent and HIF-independent hypoxia-induced genes in TNBC cells. Our findings describe BACH1 as a novel oxygen-sensitive effector of the hypoxia response in TNBC that represents an alternative target for attenuating hypoxia-induced, pro-metastatic signaling and therapeutic resistance.

Citation Format: Christopher M. Dann, Long C. Nguyen, Dongbo Yang, Joseph P. Wynne, Andrea Valdespino, Letícia Stock, Marsha R. Rosner. BACH1 is an oxygen-sensitive mediator of the hypoxia response in triple-negative breast cancer [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 118.

SARS-CoV-2 diverges from other betacoronaviruses in only partially activating the IRE1α/XBP1 ER stress pathway in human lung-derived cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed over 6 million individuals worldwide and continues to spread in countries where vaccines are not yet widely available, or its citizens are hesitant to become vaccinated. Therefore, it is critical to unravel the molecular mechanisms that allow SARS-CoV-2 and other coronaviruses to infect and overtake the host machinery of human cells. Coronavirus replication triggers endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR), a key host cell pathway widely believed essential for viral replication. We examined the master UPR sensor IRE1α kinase/RNase and its downstream transcription factor effector XBP1s, which is processed through an IRE1α-mediated mRNA splicing event, in human lung-derived cells infected with betacoronaviruses. We found human respiratory coronavirus OC43 (HCoV-OC43), Middle East respiratory syndrome coronavirus (MERS-CoV), and murine coronavirus (MHV) all induce ER stress and strongly trigger the kinase and RNase activities of IRE1α as well as XBP1 splicing. In contrast, SARS-CoV-2 only partially activates IRE1α through autophosphorylation, but its RNase activity fails to splice XBP1. Moreover, while IRE1α was dispensable for replication in human cells for all coronaviruses tested, it was required for maximal expression of genes associated with several key cellular functions, including the interferon signaling pathway, during SARS-CoV-2 infection. Our data suggest that SARS-CoV-2 actively inhibits the RNase of autophosphorylated IRE1α, perhaps as a strategy to eliminate detection by the host immune system.

IMPORTANCE

SARS-CoV-2 is the third lethal respiratory coronavirus after MERS-CoV and SARS-CoV to emerge this century, causing millions of deaths world-wide. Other common coronaviruses such as HCoV-OC43 cause less severe respiratory disease. Thus, it is imperative to understand the similarities and differences among these viruses in how each interacts with host cells. We focused here on the inositol-requiring enzyme 1α (IRE1α) pathway, part of the host unfolded protein response to virus-induced stress. We found that while MERS-CoV and HCoV-OC43 fully activate the IRE1α kinase and RNase activities, SARS-CoV-2 only partially activates IRE1α, promoting its kinase activity but not RNase activity. Based on IRE1α-dependent gene expression changes during infection, we propose that SARS-CoV-2 prevents IRE1α RNase activation as a strategy to limit detection by the host immune system.

Cannabidiol inhibits SARS-CoV-2 replication through induction of the host ER stress and innate immune responses

The spread of SARS-CoV-2 and ongoing COVID-19 pandemic underscores the need for new treatments. Here we report that cannabidiol (CBD) inhibits infection of SARS-CoV-2 in cells and mice. CBD and its metabolite 7-OH-CBD, but not THC or other congeneric cannabinoids tested, potently block SARS-CoV-2 replication in lung epithelial cells. CBD acts after viral entry, inhibiting viral gene expression and reversing many effects of SARS-CoV-2 on host gene transcription. CBD inhibits SARS-CoV-2 replication in part by up-regulating the host IRE1α RNase endoplasmic reticulum (ER) stress response and interferon signaling pathways. In matched groups of human patients from the National COVID Cohort Collaborative, CBD (100 mg/ml oral solution per medical records) had a significant negative association with positive SARS-CoV-2 tests. This study highlights CBD as a potential preventative agent for early-stage SARS-CoV-2 infection and merits future clinical trials. We caution against use of non-medical formulations including edibles, inhalants or topicals as a preventative or treatment therapy at the present time.

Atomistic Model for Simulations of the Sedative Hypnotic Drug 2,2,2-Trichloroethanol

2,2,2-Trichloroethanol (TCE) is the active form of the sedative hypnotic drug chloral hydrate, one of the oldest sleep medications in the market. Understanding of TCE's action mechanisms to its many targets, particularly within the ion channel family, could benefit from the state-of-the-art computational molecular studies. In this direction, we employed de novo modeling aided by the force field toolkit to develop CHARMM36-compatible TCE parameters. The classical potential energy function was calibrated targeting molecular conformations, local interactions with water molecules, and liquid bulk properties. Reference data comes from both tabulated thermodynamic properties and ab initio calculations at the MP2 level. TCE solvation free energy calculations in water and oil reproduce a lipophilic, yet nonhydrophobic, behavior. Indeed, the potential mean force profile for TCE partition through the phospholipid bilayer reveals the sedative's preference for the interfacial region. The calculated partition coefficient also matches experimental measures. Further validation of the proposed parameters is supported by the model's ability to recapitulate quenching experiments demonstrating TCE binding to bovine serum albumin.

Binding of the general anesthetic sevoflurane to ion channels

The direct-site hypothesis assumes general anesthetics bind ion channels to impact protein equilibrium and function, inducing anesthesia. Despite advancements in the field, a first principle all-atom demonstration of this structure-function premise is still missing. We focus on the clinically used sevoflurane interaction to anesthetic-sensitive Kv1.2 mammalian channel to resolve if sevoflurane binds protein’s well-characterized open and closed structures in a conformation-dependent manner to shift channel equilibrium. We employ an innovative approach relying on extensive docking calculations and free-energy perturbation of all potential binding sites revealed by the latter, and find sevoflurane binds open and closed structures at multiple sites under complex saturation and concentration effects. Results point to a non-trivial interplay of site and conformation-dependent modes of action involving distinct binding sites that increase channel open-probability at diluted ligand concentrations. Given the challenge in exploring more complex processes potentially impacting channel-anesthetic interaction, the result is revealing as it demonstrates the process of multiple anesthetic binding events alone may account for open-probability shifts recorded in measurements.

General anesthetics are central to modern medicine, yet their microscopic mechanism of action is still unknown. Here, we demonstrate that a clinically used anesthetic, sevoflurane, binds the mammalian voltage-gated potassium channel Kv1.2 effecting a shift in its open probability, even at low concentrations. The results, supported by recent experimental measurements, are promising as they demonstrate that the molecular process of direct binding of anesthetic to ion channels play a relevant role in anesthesia.

Conduction in a biological sodium selective channel

The crystal structure of NavAb, a bacterial voltage gated Na(+) channel, exhibits a selectivity filter (SF) wider than that of K(+) channels. This new structure provides the opportunity to explore the mechanism of conduction and help rationalize its selectivity for sodium. Recent molecular dynamics (MD) simulations of single- and two-ion permeation processes have revealed that a partially hydrated Na(+) permeates the channel by exploring three SF binding sites while being loosely coupled to other ions and/or water molecules; a finding that differs significantly from the behavior of K(+) selective channels. Herein, we present results derived from a combination of metadynamics and voltage-biased MD simulations that throws more light on the nature of the Na(+) conduction mechanism. Conduction under 0 mV bias explores several distinct pathways involving the binding of two ions to three possible SF sites. While these pathways are very similar to those observed in the presence of a negative potential (inward conduction), a completely different mechanism operates for outward conduction at positive potentials.

Health-related predictors of falls and fractures in women over 40

SUMMARY

A longitudinal study of women aged 40-80 predicted single falls from a previous fall history and deficient vestibular integration. Multiple falls were predicted by a fall history, low activity levels, more medical conditions and deficient vestibular integration. Low bone mineral density, more medical conditions and fall history predicted fractures.

INTRODUCTION

The purpose of this study was to identify potentially modifiable health-related factors predicting falls and fractures, focussing on women over 40.

METHODS

Four hundred and forty-nine women aged 40-80 years from the Longitudinal Assessment of Women study participated. Demographic information (age, BMI, medications, medical conditions and activity level), balance assessments (including timed up & go and modified clinical test for sensory interaction of balance) and measurements of bone mineral density and body composition were collected in 2001; fall and fracture data were gathered in 2003, 2005, 2007, 2008 and 2010 to determine incidence.

RESULTS

Multinomial logistic regression revealed that single falls could be predicted by a history of previous falls (OR 3.08) and being unsteady in bipedal stance on foam with eyes closed (OR 1.99). Multiple falls were predicted by a history of falls at baseline (OR 4.69), low levels of activity (OR 2.17), greater number of medical conditions (OR 1.12) and being unsteady in bipedal stance on foam with eyes closed (OR 4.21). Low bone mineral density (OR 3.13), greater number of medical conditions (OR 1.32) and a history of falls (OR 3.04) were predictive of fractures.

CONCLUSIONS

Poor health, decreased balance, and inactivity are predictive of falls and low bone mineral density, low activity level and poor health predictive fractures. Results suggest failing the balance test bipedal stance on foam with eyes closed in the presence of low activity and poor health is a valid quick screening tool for detecting potential fallers for referral for in-depth balance assessment and intervention.

Hardware to hard hats: training workers for action (from offices to construction sites)

A university-based labor education program provides training to unionists, emphasizing the skills needed by workers and their representatives in order to promote their rights to health and safety on the job. The article describes two examples of this training approach. The first example is a training program for video display terminal (VDT) operators which prepares them to take a leadership role in advancing policies to regulate working conditions for VDT users. The second is a program designed to improve the quality of safety, or "tailgate" meetings in the construction industry by promoting an approach that encourages active worker participation in identifying potential hazards and developing solutions. The methodologies used to achieve action-oriented outcomes are described.

Early intraocular pressure rise after trabeculectomy

Intraocular pressure (IOP) was measured 4 to 6 hours after surgery and on the first postoperative day in 35 eyes of 35 consecutive patients undergoing initial trabeculectomy. In 27 eyes, the anterior chamber was re-formed at the completion of surgery with balanced salt solution, and in eight eyes it was reformed with hyaluronate sodium. A total of six eyes (17%) had an IOP of 40 mm Hg or greater 4 to 6 hours after surgery. Patients who received hyaluronate to maintain the depth of the anterior chamber had a significantly greater chance of experiencing a marked postoperative IOP rise, both at 4 to 6 hours (P = .005) and on the first postoperative day (P = .0038). There was no correlation between the postoperative IOP rise and the patient's age, sex, glaucoma diagnosis, preoperative IOP, use of 5-fluorouracil, or the number of sutures used to close the scleral flap. Hyaluronate may contribute to an early increase in IOP that could result in further visual field loss in eyes with severe glaucomatous damage. We recommend early monitoring of IOP after trabeculectomy and avoiding the routine use of hyaluronate.

Hispanic Americans: A Brief Profile

The latest population statistics show the Hispanic population in the US to be fast-growing, young and very diverse in nature. While the Hispanic group lags behind the general population in average education and employment rates, many gains have been made in the past decade. The growing numbers and attainments of Hispanics will mean an increased demand for better education, employment and training programs, housing and family services.

Studies of blood pressure in Tecumseh, Michigan. I. Blood pressure in young people and its relationship to personal and familial characteristics and complications of pregnancy in mothers

Relationships between blood pressures (BPs) of young people and a number of personal, parental and familial characteristics have been assessed in the population of Tecumseh, Michigan. Systolic and fifth phase diastolic BPs were measured in 4500 persons under 20 years of age at the time of their first examination. Body size, fatness and heart rates of the subjects themselves were significantly related to their age- and sex-adjusted BP scores. The parents' BP scores were also correlated with those of the young subjects, and scores were significantly higher in those whose mothers had had high BP or toxemia in pregnancy of a stillbirth. A weak association between BP and socioeconomic circumstances was suggested by the slightly higher mean BP scores found in sons and daughters of men in blue collar jobs and of men and women with the least education. BP levels were not associated with birth order, sibship size or birth weight nor with the numbers of pregnancies, live births or abortions experienced by the mothers of young subjects. In a stepwise multiple regression, the most important determinants of BP were weight/height ratios of the subjects themselves and BP levels of their parents; a small additional effect of complications of pregnancy in the mother was detectable in the offspring 0--19 years laters.