Identification of Novel Dual-Target Estrogen Receptor α Degraders with Tubulin Inhibitory Activity for the Treatment of Endocrine-Resistant Breast Cancer.

Endocrine resistance remains a significant problem in the clinical treatment of estrogen receptor α-positive (ERα+) breast cancer (BC). In this study, we developed a series of novel dual-functional ERα degraders based on a bridged bicyclic scaffold with selenocyano (SeCN) side chains. These compounds displayed potent ERα degradation and tubulin depolymerization activity. Among them, compounds 35s and 35t exhibited the most promising antiproliferative and ERα degradation activity in multiple ERα+ BC cell lines bearing either wild-type or mutant ERα. Meanwhile, compounds 35s and 35t disrupted the microtubule network by restraining tubulin polymerization, evidenced by 35t inducing cell cycle arrest in the G2/M phase. In MCF-7 and LCC2 xenograft models, compounds 35s and 35t remarkably suppressed tumor growth without noticeable poisonousness. Finally, this study provided guidance for developing new dual-target antitumor drug candidates for the ERα+ BC therapy, especially for the resistant variant.

Discovery of a Novel Class of PROTACs as Potent and Selective Estrogen Receptor α Degraders to Overcome Endocrine-Resistant Breast Cancer In Vitro and In Vivo.

The estrogen receptor (ER) is a well-established target for endocrine therapies of ER-positive breast cancer (ER+ BC), but endocrine resistance limits the efficacy of clinical drugs. Using proteolysis targeting chimera (PROTAC) technology to degrade ERα may be an effective alternative to endocrine therapies. Herein, we disclose a novel series of potent and selective ERα PROTACs based on an oxabicycloheptane sulfonamide (OBHSA) scaffold, with no associated ERß degradation. These PROTACs showed significant antiproliferation and ERα degradation activities against a broad spectrum of ER+ BC cells including tamoxifen-resistant and ERα mutant cell lines. Genomics analysis confirmed that these PROTACs inhibited the nascent RNA synthesis of ERα target genes and impaired genome-wide ERα binding. Compound ZD12 exhibited excellent antitumor potency and ERα degradation activity in both tamoxifen-sensitive and -resistant BC mice models, which are superior to fulvestrant. This study demonstrates the potential of these PROTACs as novel drug candidates for endocrine-resistant BC treatment.

CDK12 and Integrator-PP2A complex modulates LEO1 phosphorylation for processive transcription elongation.

Cyclin-dependent kinase 12 (CDK12) interacts with cyclin K to form a functional nuclear kinase that promotes processive transcription elongation through phosphorylation of the C-terminal domain of RNA polymerase II (Pol II). To gain a comprehensive understanding of CDK12's cellular function, we used chemical genetic and phosphoproteomic screening to identify a landscape of nuclear human CDK12 substrates, including regulators of transcription, chromatin organization, and RNA splicing. We further validated LEO1, a subunit of the polymerase-associated factor 1 complex (PAF1C), as a bona fide cellular substrate of CDK12. Acute depletion of LEO1, or substituting LEO1 phosphorylation sites with alanine, attenuated PAF1C association with elongating Pol II and impaired processive transcription elongation. Moreover, we discovered that LEO1 interacts with and is dephosphorylated by the Integrator-PP2A complex (INTAC) and that INTAC depletion promotes the association of PAF1C with Pol II. Together, this study reveals an uncharacterized role for CDK12 and INTAC in regulating LEO1 phosphorylation, providing important insights into gene transcription and its regulation.

OBHS Drives Abnormal Glycometabolis Reprogramming via GLUT1 in Breast Cancer.

Due to the poor metabolic conditions fomenting the emergence of the Warburg effect (WE) phenotype, abnormal glycometabolism has become a unique and fundamental research topic in the field of tumor biology. Moreover, hyperglycemia and hyperinsulinism are associated with poor outcomes in patients with breast cancer. However, there are a few studies on anticancer drugs targeting glycometabolism in breast cancer. We hypothesized that Oxabicycloheptene sulfonate (OBHS), a class of compounds that function as selective estrogen receptor modulators, may hold potential in a therapy for breast cancer glycometabolism. Here, we evaluated concentrations of glucose, glucose transporters, lactate, 40 metabolic intermediates, and glycolytic enzymes using an enzyme-linked immunosorbent assay, Western blotting, and targeted metabolomic analysis in, in vitro and in vivo breast cancer models. OBHS significantly inhibited the expression of glucose transporter 1 (GLUT1) via PI3K/Akt signaling pathway to suppress breast cancer progression and proliferation. Following an investigation of the modulatory effect of OBHS on breast cancer cells, we found that OBHS suppressed the glucose phosphorylation and oxidative phosphorylation of glycolytic enzymes, leading to the decreased biological synthesis of ATP. This study was novel in highlighting the role of OBHS in the remodeling of tumor glycometabolism in breast cancer, and this is worth further investigation of breast cancer in clinical trials.

Discovery of Novel Bicyclic Phenylselenyl-Containing Hybrids: An Orally Bioavailable, Potential, and Multiacting Class of Estrogen Receptor Modulators against Endocrine-Resistant Breast Cancer.

Breast cancer (BC) is a multifactorial disease and is prone to drug resistance during treatment. In this study, we described a new class of multifunctional estrogen receptor (ER) modulators ground on a prerogative indirect antagonism skeleton (OBHS, oxabicycloheptene sulfonate) of ER containing a phenylselenyl group. Compound 34b showed significant antiproliferative activities against tamoxifen-sensitive (MCF-7) and -resistant (LCC2) cells. Moreover, hexokinase 1 (HK1) was identified as a direct target of 34b. Further mechanism investigations proved that 34b induced apoptosis, which was associated with mitochondrial dysfunction caused by the synergistic effects of downregulating mitochondrial-bound HK1 protein and promoting reactive oxygen species generation. In vivo, 34b had a favorable pharmacokinetic profile with a bioavailability of 23.20% and exhibited more potent tumor suppression than tamoxifen both in MCF-7 and LCC2 tumor xenograft models. Collectively, our studies showed that 34b is a promising new multifunctional candidate compound for ERα+ BC treatment, particularly for tamoxifen-resistant BC.

Ligand-induced native G-quadruplex stabilization impairs transcription initiation.

G-quadruplexes (G4s) are noncanonical DNA secondary structures formed through the self-association of guanines, and G4s are distributed widely across the genome. G4 participates in multiple biological processes including gene transcription, and G4-targeted ligands serve as potential therapeutic agents for DNA-targeted therapies. However, genome-wide studies of the exact roles of G4s in transcriptional regulation are still lacking. Here, we establish a sensitive G4-CUT&Tag method for genome-wide profiling of native G4s with high resolution and specificity. We find that native G4 signals are cell type-specific and are associated with transcriptional regulatory elements carrying active epigenetic modifications. Drug-induced promoter-proximal RNA polymerase II pausing promotes nearby G4 formation. In contrast, G4 stabilization by G4-targeted ligands globally reduces RNA polymerase II occupancy at gene promoters as well as nascent RNA synthesis. Moreover, ligand-induced G4 stabilization modulates chromatin states and impedes transcription initiation via inhibition of general transcription factors loading to promoters. Together, our study reveals a reciprocal genome-wide regulation between native G4 dynamics and gene transcription, which will deepen our understanding of G4 biology toward therapeutically targeting G4s in human diseases.

Genomic profiling of native R loops with a DNA-RNA hybrid recognition sensor.

An R loop is a unique triple-stranded structure that participates in multiple key biological processes and is relevant to human diseases. Accurate and comprehensive R loop profiling is a prerequisite for R loops studies. However, current R loop mapping methods generate large discrepancies, therefore an independent method is in urgent need. Here, we establish an independent R loop CUT&Tag (Tn5-based cleavage under targets and tagmentation) method by combining CUT&Tag and GST-His6-2×HBD (glutathione S-transferase-hexahistidine-2× hybrid-binding domain), an artificial DNA-RNA hybrid sensor that specifically recognizes the DNA-RNA hybrids. We demonstrate that the R loop CUT&Tag is sensitive, reproducible, and convenient for native R loop mapping with high resolution, and find that the capture strategies, instead of the specificity of sensors, largely contribute to the disparities among different methods. Together, we provide an independent strategy for genomic profiling of native R loops and help resolve discrepancies among multiple R loop mapping methods.

Quantifying Induced Polarization of Conductive Inclusions in Porous Media and Implications for Geophysical Measurements.

Induced polarization (IP) mapping has gained increasing attention in the past decades, as electrical induced polarization has been shown to provide interesting signatures for detecting the presence of geological materials such as clay, ore, pyrite, and potentially, hydrocarbons. However, efforts to relate complex conductivities associated with IP to intrinsic physical properties of the corresponding materials have been largely empirical. Here we present a quantitative interpretation of induced polarization signatures from brine-filled rock formations with conductive inclusions and show that new opportunities in geophysical exploration and characterization could arise. Initially tested with model systems with solid conductive inclusions, this theory is then extended and experimentally tested with nanoporous conductors that are shown to have a distinctive spectral IP response. Several of the tests were conducted with nano-porous sulfides (pyrite) produced by sulfate-reducing bacteria grown in the lab in the presence of a hydrocarbon source, as well as with field samples from sapropel formations. Our discoveries and fundamental understanding of the electrode polarization mechanism with solid and porous conductive inclusions suggest a rigorous new approach in geophysical exploration for mineral deposits. Moreover, we show how induced polarization of biologically generated mineral deposits can yield a new paradigm for basin scale hydrocarbon exploration.

Modeling Oil Recovery for Mixed Macro- and Micro-Pore Carbonate Grainstones.

In general, modeling oil-recovery is a challenging problem involving detailed fluid flow calculations with required structural details that challenge current experimental resolution. Recent laboratory experiments on mixed micro- and macro-pore suggest that there is a systematic relationship between remaining oil saturation (ROS) and the fraction of micro-pores. Working with experimental measurements of the pores obtained from X-ray tomography and mercury intrusion capillary pressure porosimetry, we define a digital rock model exemplifying the key structural elements of these carbonate grainstones. We then test two fluid-flow models: invasion percolation model and effective medium model. Although invasion percolation identifies the important impact of macro-pore percolation on permeability, it does not describe the dependence of ROS on micro-pore percentage. We thus modified the effective medium model by introducing a single-parameter descriptor, reff. Oil from pores r ≥ reff is fully removed, while for the remaining pores with r < reff, their contribution is scaled by (r/reff)2. Applying this straightforward physics to pore size distributions for the mixed-pore grainstones reproduces the experimental ROS dependence.

Intrinsic electron-phonon resistivity of Bi2Se3 in the topological regime.

We measure the temperature-dependent carrier density and resistivity of the topological surface state of thin exfoliated Bi(2)Se(3) in the absence of bulk conduction. When the gate-tuned chemical potential is near or below the Dirac point, the carrier density is strongly temperature-dependent, reflecting thermal activation from the nearby bulk valence band, while, above the Dirac point, unipolar n-type surface conduction is observed with negligible thermal activation of bulk carriers. In this regime, linear resistivity vs temperature reflects intrinsic electron-acoustic phonon scattering. A quantitative comparison with a theoretical transport calculation including both phonon and disorder effects gives the ratio of deformation potential to Fermi velocity D/hν(F)=4.7 Å(-1). This strong phonon scattering in the Bi(2)Se(3) surface state gives intrinsic limits for the conductivity and charge carrier mobility at room temperature of ~550 µS per surface and ~10,000 cm(2)/V s.

Theory of 2D transport in graphene for correlated disorder.

We theoretically revisit graphene transport properties as a function of carrier density, taking into account possible correlations in the spatial distribution of the Coulomb impurity disorder in the environment. We find that the charged impurity correlations give rise to a density-dependent graphene conductivity, which agrees well qualitatively with the existing experimental data. We also find, quite unexpectedly, that the conductivity could increase with increasing impurity density if there is sufficient interimpurity correlation present in the system. In particular, the linearity (sublinearity) of graphene conductivity at lower (higher) gate voltage is naturally explained as arising solely from impurity correlation effects in the Coulomb disorder.