Mechanisms of sensitivity and resistance to CDK4/CDK6 inhibitors in hormone receptor-positive breast cancer treatment.

Cell cycle dysregulation is a hallmark of cancer that promotes eccessive cell division. Cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6) are key molecules in the G1-to-S phase cell cycle transition and are crucial for the onset, survival, and progression of breast cancer (BC). Small-molecule CDK4/CDK6 inhibitors (CDK4/6i) block phosphorylation of tumor suppressor Rb and thus restrain susceptible BC cells in G1 phase. Three CDK4/6i are approved for the first-line treatment of patients with advanced/metastatic hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) BC in combination with endocrine therapy (ET). Though this has improved the clinical outcomes for survival of BC patients, there is no established standard next-line treatment to tackle drug resistance. Recent studies suggest that CDK4/6i can modulate other distinct effects in both BC and breast stromal compartments, which may provide new insights into aspects of their clinical activity. This review describes the biochemistry of the CDK4/6-Rb-E2F pathway in HR+ BC, then discusses how CDK4/6i can trigger other effects in BC/breast stromal compartments, and finally outlines the mechanisms of CDK4/6i resistance that have emerged in recent preclinical studies and clinical cohorts, emphasizing the impact of these findings on novel therapeutic opportunities in BC.

PI3K/AKT/mTOR signaling transduction pathway and targeted therapies in cancer.

The PI3K/AKT/mTOR (PAM) signaling pathway is a highly conserved signal transduction network in eukaryotic cells that promotes cell survival, cell growth, and cell cycle progression. Growth factor signalling to transcription factors in the PAM axis is highly regulated by multiple cross-interactions with several other signaling pathways, and dysregulation of signal transduction can predispose to cancer development. The PAM axis is the most frequently activated signaling pathway in human cancer and is often implicated in resistance to anticancer therapies. Dysfunction of components of this pathway such as hyperactivity of PI3K, loss of function of PTEN, and gain-of-function of AKT, are notorious drivers of treatment resistance and disease progression in cancer. In this review we highlight the major dysregulations in the PAM signaling pathway in cancer, and discuss the results of PI3K, AKT and mTOR inhibitors as monotherapy and in co-administation with other antineoplastic agents in clinical trials as a strategy for overcoming treatment resistance. Finally, the major mechanisms of resistance to PAM signaling targeted therapies, including PAM signaling in immunology and immunotherapies are also discussed.

Knowledge and attitude regarding organ donation among medical students in Hong Kong: a cross-sectional study.

OBJECTIVES: The rate of organ donation in Hong Kong is among the lowest in developed regions. Since medical students will play an important role in counselling patients for organ donation and identifying potential donors in the future, their knowledge, attitudes and action for organ donation are important. This study aims to understand knowledge, attitudes and actions with regard to organ donation among medical students and investigate the factors determining the knowledge and attitudes. DESIGN: A cross-sectional study. SETTING AND PARTICIPANTS: Medical students in Hong Kong were invited to complete a questionnaire. 377 medical students participated in the study. METHODS: The questionnaire assessed their attitudes, knowledge, action of organ donation, belief and perception on organ donation, and other factors. Linear regression analyses and logistic regression were performed to analyse the effect of the variables on knowledge, attitudes and action for organ donation. RESULTS: Almost all medical students (99.5%) held a positive attitude towards organ donation, but only 28.1% have signed up as organ donors. Determinants of knowledge of organ donation included belief in preservation of intact body after death (ß = -0.14, 95% CI = -0.24 to -0.04) and perceived confidence and competence of organ donation discussion (ß = -0.12, 95% CI = -0.22 to -0.02). Predictors of organ donor registration status included knowledge of organ donation (OR=1.03, 95% CI=1.00 to 1.06), perceived convenience of organ donation registration (OR=3.75, 95% CI=1.62 to 8.71), commitment to organ donation (OR=3.81, 95% CI=2.01 to 7.21) and exposure to organ donation (OR=4.28, 95% CI=2.37 to 7.74). CONCLUSIONS: Knowledge is positively associated with organ donation action. The above determinants of organ donation could be emphasised in medical education.

Biomimetic synthesis of the non-canonical PPAP natural products yezo'otogirin C and hypermogin D, and studies towards the synthesis of norascyronone A.

Oxidative degradation and rearrangement of polycyclic polyprenylated acylphloroglucinols (PPAPs) has created diverse families of unique natural products that are attractive targets for biomimetic synthesis. Herein, we report a racemic synthesis of hyperibrin A and its oxidative radical cyclization to give yezo'otogirin C, followed by epoxidation and House-Meinwald rearrangement to give hypermogin D. We also investigated the biomimetic synthesis of norascyronone A via a similar radical cyclization pathway, with unexpected results that give insight into its biosynthesis.

Efficacy of physical therapy interventions on quality of life and upper quadrant pain severity in women with post-mastectomy pain syndrome: a systematic review and meta-analysis.

PURPOSE: To determine the efficacy of physical therapy interventions on quality of life (QoL) and pain severity in post-mastectomy pain syndrome (PMPS). METHODS: Multiple databases were searched from database inception to October 2020. Searches were limited to human studies published in either English or Chinese in peer-reviewed journals with full text available for randomized controlled trials conducted on females. Trials comparing the effectiveness of physical therapy interventions against control conditions on QoL and pain were included. RESULTS: Eighteen trials were included in the review. The pooled analysis of the four exercise trials revealed a significant effect of the intervention on general [standardized mean difference [SMD]: 0.87 (95%CI: 0.36, 1.37); p = 0.001], physical [SMD: 0.34 (95%CI: 0.01, 0.66); p = 0.044], and mental health components [SMD: 0.27 (95%CI: 0.03, 0.51); p = 0.027] of QoL compared with the control condition. Meta-analyses of six exercise trials, two myofascial release trials, and two acupuncture trials revealed a significant improvement in pain severity in the treatment group than in the control group. However, meta-analyses of two studies revealed a non-significant effect of compression therapy compared to control on pain severity. CONCLUSION: Our meta-analyses found that exercise is beneficial for improving the QoL and pain severity of women with PMPS. Future studies are needed to determine the optimal parameters for exercise interventions designed to improve QoL and pain severity in women with PMPS. The effect of acupuncture, myofascial release, and compression therapy remains inconclusive, and future research is required to validate the effect of these interventions on PMPS.

Mast cells: Therapeutic targets for COVID-19 and beyond.

Mast cells (MCs) are innate immune cells that widely distribute throughout all tissues and express a variety of cell surface receptors. Upon activation, MCs can rapidly release a diverse array of preformed mediators residing within their secretory granules and newly synthesize a broad spectrum of inflammatory and immunomodulatory mediators. These unique features of MCs enable them to act as sentinels in response to rapid changes within their microenvironment. There is increasing evidence now that MCs play prominent roles in other pathophysiological processes besides allergic inflammation. In this review, we highlight the recent findings on the emerging roles of MCs in the pathogenesis of coronavirus disease-2019 (COVID-19) and discuss the potential of MCs as novel therapeutic targets for COVID-19 and other non-allergic inflammatory diseases.

Dissecting Programmed Cell Death with Small Molecules.

Programmed cell death (PCD) is fundamentally an indispensable process in all cellular activities, including cell development, wound healing, and immune surveillance of tumors (Galluzzi, L. et al. Cell Death Differ. 2018, 25, 486-541). Malfunctioning of PCD has been shown to be closely related to human diseases such as acute pancreatitis, neurodegenerative diseases, and diverse types of cancers. To date, multiple PCD processes have been discovered and the corresponding regulatory pathways have been elucidated. For example, apoptosis and autophagy are two PCD mechanisms that have been well studied by sophisticated models and probe toolkits. However, limited genetic and chemical tools for other types of PCD hamper the elucidation of their molecular mechanisms. Our group has been studying PCD using both function-oriented synthesis and chemical biology strategies, including the development of diverse chemical probes based on novel PCD modulators. For instance, in the development of downstream programmed necrosis (or necroptosis) inhibitor necrosulfonamide, we used a chemical probe to unveil a functional protein that was not previously implicated in necroptosis, mixed lineage kinase domain-like protein (MLKL). In addition, high throughput screening and medicinal chemistry enabled the discovery of bioymifi, a small molecule agonist which selectively causes oligomerization of the death receptor 5 (DR5), to induce extrinsic apoptosis. Furthermore, we developed a biomimetic synthetic strategy based on diverse Diels-Alder reactions in the total syntheses of ainsliadimers A and B, ainsliatrimers A and B, and gonchnatiolides A-C, which are natural product inhibitors or activators for PCD. Using synthetic ainsliadimer A probe, we elucidated that ainsliadimer A inhibits the NF-κB pathway by covalently binding to Cys46 of IKKß and triggers apoptosis of cancer cells. We have also revealed that IKKß is allosterically inhibited by ainsliadimer A. In addition to total synthesis, we have developed a bioorthogonal click hetero-Diels-Alder cycloaddition of vinyl thioether and o-quinolinone quinone methide (TQ-ligation) to facilitate small molecule target identification. The combination of total synthesis and TQ-ligation enables subcellular imaging and identification of the cellular target of ainsliatrimer A to be PPARγ. In addition, TQ-ligation has been applied in the discovery of heat shock protein 90 (HSP90) as one of the functional target proteins for kongensin A. We also confirmed that kongensin A covalently attaches to Cys420 within HSP90 and demonstrated that kongensin A blocks the interaction between HSP90 and CDC37 and subsequently inhibits necroptosis. Our development of these diverse PCD modulators provides not only effective chemical tools for fundamental biomedical research, but also the foundation for drug discovery targeting important human diseases such as cancers and inflammation caused by malfunction of PCD.

Frequency and Distribution of Chest Radiographic Findings in Patients Positive for COVID-19.

Background Current coronavirus disease 2019 (COVID-19) radiologic literature is dominated by CT, and a detailed description of chest radiography appearances in relation to the disease time course is lacking. Purpose To describe the time course and severity of findings of COVID-19 at chest radiography and correlate these with real-time reverse transcription polymerase chain reaction (RT-PCR) testing for severe acute respiratory syndrome coronavirus 2, or SARS-CoV-2, nucleic acid. Materials and Methods This is a retrospective study of patients with COVID-19 confirmed by using RT-PCR and chest radiographic examinations who were admitted across four hospitals and evaluated between January and March 2020. Baseline and serial chest radiographs (n = 255) were reviewed with RT-PCR. Correlation with concurrent CT examinations (n = 28) was performed when available. Two radiologists scored each chest radiograph in consensus for consolidation, ground-glass opacity, location, and pleural fluid. A severity index was determined for each lung. The lung scores were summed to produce the final severity score. Results The study was composed of 64 patients (26 men; mean age, 56 years ± 19 [standard deviation]). Of these, 58 patients had initial positive findings with RT-PCR (91%; 95% confidence interval: 81%, 96%), 44 patients had abnormal findings at baseline chest radiography (69%; 95% confidence interval: 56%, 80%), and 38 patients had initial positive findings with RT-PCR testing and abnormal findings at baseline chest radiography (59%; 95% confidence interval: 46%, 71%). Six patients (9%) showed abnormalities at chest radiography before eventually testing positive for COVID-19 with RT-PCR. Sensitivity of initial RT-PCR (91%; 95% confidence interval: 83%, 97%) was higher than that of baseline chest radiography (69%; 95% confidence interval: 56%, 80%) (P = .009). Radiographic recovery (mean, 6 days ± 5) and virologic recovery (mean, 8 days ± 6) were not significantly different (P = .33). Consolidation was the most common finding (30 of 64; 47%) followed by ground-glass opacities (21 of 64; 33%). Abnormalities at chest radiography had a peripheral distribution (26 of 64; 41%) and lower zone distribution (32 of 64; 50%) with bilateral involvement (32 of 64; 50%). Pleural effusion was uncommon (two of 64; 3%). The severity of findings at chest radiography peaked at 10-12 days from the date of symptom onset. Conclusion Findings at chest radiography in patients with coronavirus disease 2019 frequently showed bilateral lower zone consolidation, which peaked at 10-12 days from symptom onset. © RSNA, 2020.

Biomimetic Synthesis of Rhytidenone†A and Mode of Action of Cytotoxic Rhytidenone†F.

The rhytidenone family comprises spirobisnaphthalene natural products isolated from the mangrove endophytic fungus Rhytidhysteron rufulum AS21B. The biomimetic synthesis of rhytidenone A was achieved by a Michael reaction/aldol/lactonization cascade in a single step from the proposed biosynthetic precursor rhytidenone F. Moreover, the mode of action of the highly cytotoxic rhytidenone F was investigated. The pulldown assay coupled with mass spectrometry analysis revealed the target protein PA28γ is covalently attached to rhytidenone F at the Cys92 residue. The interactions of rhytidenone F with PA28γ lead to the accumulation of p53, which is an essential tumor suppressor in humans. Consequently, the Fas-dependent signaling pathway is activated to initiate cellular apoptosis. These studies have identified the first small-molecule inhibitor targeting PA28γ, suggesting rhytidenone F may serve as a promising natural product lead for future anticancer drug development.

Biomimetic and Biocatalytic Synthesis of Bruceol.

The first total synthesis of bruceol has been achieved using a biomimetic cascade cyclization initiated by a stereoselective Jacobsen-Katsuki epoxidation (and kinetic resolution) of racemic protobruceol-I. A bacterial cytochrome P450 monooxygenase was also found to catalyze the conversion of protobruceol-I into bruceol. The first full analysis of the NMR data of natural bruceol suggested that "isobruceol" was a previously unrecognized natural product also isolated from Philotheca brucei. This was confirmed by the re-isolation, synthesis, and X-ray analysis of isobruceol. In total, eight stereoisomers and structural isomers of bruceol have been synthesized in a highly divergent approach.

Long-term clinical outcomes after fatty liver screening in patients undergoing coronary angiogram: A prospective cohort study.

UNLABELLED: There is ongoing debate on whether screening for nonalcoholic fatty liver disease (NAFLD) is worthwhile in high-risk groups. Because of shared risk factors, NAFLD is highly prevalent in patients with coronary artery disease. We aimed to test the hypothesis that NAFLD screening in patients requiring coronary angiogram would identify high-risk patients and predict long-term clinical outcomes. This was a prospective cohort study. NAFLD screening was performed by abdominal ultrasonography before coronary angiogram in 612 consecutive patients. At baseline, 356 (58.2%) patients had NAFLD. NAFLD patients, compared with those without, were more likely to have >50% stenosis in one or more coronary arteries (84.6% vs. 64.1%; P < 0.001) and therefore require percutaneous coronary intervention (68.3% vs. 43.4%; P < 0.001). During 3,679 patient-years of follow-up, 47 (13.2%) NAFLD patients and 59 (23.0%) patients without NAFLD died (age- and sex-adjusted hazard ratio [aHR]: 0.36; 95% confidence interval [CI]: 0.18-0.70; P = 0.003). Composite cardiovascular outcomes (cardiovascular deaths, nonfatal myocardial infarction, heart failure, or secondary interventions) were similar between groups (36.5% vs. 37.1%; aHR, 0.90; 95% CI: 0.69-1.18). Older age and diabetes were the only independent factors associated with cardiovascular events. Only 2 patients, both in the NAFLD group, died of primary liver cancer. No other patients developed liver-related complications. CONCLUSION: In patients with clinical indications for coronary angiogram, the presence of NAFLD is associated with coronary artery stenosis and need for coronary intervention, but not increased mortality or cardiovascular complications. Liver cancer and cirrhotic complications are rare. Our data do not support NAFLD screening in this patient group at present, but studies with a longer duration of follow-up are needed.

Structure-activity relationship of daptomycin analogues with substitution at (2S, 3R) 3-methyl glutamic acid position.

Daptomycin is a highly effective lipopeptide antibiotic against Gram-positive pathogens. The presence of (2S, 3R) 3-methyl glutamic acid (mGlu) in daptomycin has been found to be important to the antibacterial activity. However the role of (2S, 3R) mGlu is yet to be revealed. Herein, we reported the syntheses of three daptomycin analogues with (2S, 3R) mGlu substituted by (2S, 3R) methyl glutamine (mGln), dimethyl glutamic acid and (2S, 3R) ethyl glutamic acid (eGlu), respectively, and their antibacterial activities. The detailed synthesis of dimethyl glutamic acid was also reported.

Biosynthetically-inspired oxidations of capillobenzopyranol.

The synthesis of verrubenzospirolactone from its proposed biosynthetic precursor, capillobenzopyranol, has been shown to be chemically feasible via a simple reaction sequence. The key steps are a chemoselective furan oxidation mediated by NaClO2, a stereoselective dehydration of a γ-methoxybutenolide, and an intramolecular Diels-Alder reaction.

Biomimetic Total Synthesis of (±)-Verrubenzospirolactone.

A five-step total synthesis of (±)-verrubenzospirolactone has been achieved using a biomimetic, intramolecular Diels-Alder reaction of a 2H-chromene to form two rings and four stereocenters in the final step. This Diels-Alder reaction occurs spontaneously at 30 °C "on-water", and thus suggests that it is likely to be non-enzymatic in nature. The structure of (±)-verrubenzospirolactone was also used to inspire a quadruple cascade reaction to generate seven stereocenters, four rings, three C-C bonds, and two C-O bonds in one step.

Covalent Ras Dimerization on Membrane Surfaces through Photosensitized Oxidation.

Ras, a small GTPase found primarily on the inner leaflet of the plasma membrane, is an important signaling node and an attractive target for anticancer therapies. Lateral organization of Ras on cellular membranes has long been a subject of intense research; in particular, whether it forms dimers on membranes as part of its regulatory function has been a point of great interest. Here we report Ras dimer formation on membranes by Type II photosensitization reactions, in which molecular oxygen mediates the radicalization of proteins under typical fluorescence experimental conditions. The presence of Ras dimers on membranes was detected by diffusion-based fluorescence techniques including fluorescence correlation spectroscopy and single particle tracking, and molecular weights of the stable covalently coupled species were confirmed by gel electrophoresis. Fluorescence spectroscopy implicates interprotein dityrosine as one of the dimerization motifs. The specific surface tyrosine distribution on Ras renders the protein especially sensitive to this reaction, and point mutations affecting surface tyrosines are observed to alter dimerization potential. The photosensitization reactions are reflective of physiological oxidative stress induced by reactive oxygen species, suggesting such processes may occur naturally and influence signaling pathways in cells.

Protein chemical synthesis by serine and threonine ligation.

An efficient method has been developed for the salicylaldehyde ester-mediated ligation of unprotected peptides at serine (Ser) or threonine (Thr) residues. The utility of this peptide ligation approach has been demonstrated through the convergent syntheses of two therapeutic peptides--ovine-corticoliberin and Forteo--and the human erythrocyte acylphosphatase protein (∼11 kDa). The requisite peptide salicylaldehyde ester precursor is prepared in an epimerization-free manner via Fmoc-solid-phase peptide synthesis.

Biomimetic Total Synthesis of Hyperjapones†A-E and Hyperjaponols†A and†C.

Hyperjapones A-E and hyperjaponols A-C are complex natural products of mixed aromatic polyketide and terpene biosynthetic origin that have recently been isolated from Hypericum japonicum. We have synthesized hyperjapones A-E using a biomimetic, oxidative hetero-Diels-Alder reaction to couple together dearomatized acylphloroglucinol and cyclic terpene natural products. Hyperjapone A is proposed to be the biosynthetic precursor of hyperjaponol C through a sequence of: 1) epoxidation; 2) acid-catalyzed epoxide ring-opening; and 3) a concerted, asynchronous alkene cyclization and 1,2-alkyl shift of a tertiary carbocation. Chemical mimicry of this proposed biosynthetic sequence allowed a concise total synthesis of hyperjaponol C to be completed in which six carbon-carbon bonds, six stereocenters, and three rings were constructed in just four steps.

Serine/threonine ligation for natural cyclic peptide syntheses.

Covering: 2000 to 2014Cyclic peptides are a class of abundant natural products, often exhibiting attractive biological activities. The challenges in the total synthesis of cyclic peptides lie in the preparation of unnatural amino acids if present and the peptide cyclization. Cyclization is an entropy-disfavoured process, with competition between intermolecular and intramolecular reactions. Biological methods can utilize the pre-organized conformation of the side chain unprotected peptide, which brings the reacting termini into proximity, while chemical synthesis requires protecting groups, often large-size and hydrophobic in nature. In this regard, performing peptide cyclization can be an arbitrary and trial-and-error practice. In this highlight, we discuss the application of chemoselective ligation-mediated peptide cyclization in the total synthesis of natural cyclic peptides.