The Natural Products Withaferin A and Withanone from the Medicinal Herb Withania somnifera Are Covalent Inhibitors of the SARS-CoV-2 Main Protease.

The current COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) created a global health crisis. The ability of vaccines to protect immunocompromised individuals and from emerging new strains are major concerns. Hence antiviral drugs against SARS-CoV-2 are essential. The SARS-CoV-2 main protease Mpro is vital for replication and an important target for antivirals. Using CMap analysis and docking studies, withaferin A (wifA) and withanone (win), two natural products from the medicinal herb Withania somnifera (ashwagandha), were identified as promising candidates that can covalently inhibit the viral protease Mpro. Cell culture, enzymatic, LC-MS/MS, computational, and equilibrium dialysis based assays were performed. DFT calculations indicated that wifA and win can form stable adducts with thiols. The cytotoxicity of Mpro was significantly reduced by wifA and win. Both wifA and win were found to irreversibly inhibit 0.5 µM Mpro with IC50 values of 0.54 and 1.8 µM, respectively. LC-MS/MS analysis revealed covalent adduct formation with wifA at cysteines 145 and 300 of Mpro. The natural products wifA and win can irreversibly inhibit the SARS-CoV-2 main protease Mpro. Based on the work presented here we propose that both wifA and win have the potential to be safely used as preventative and therapeutic interventions for COVID-19.

Opposing Interplay between Nuclear Factor Erythroid 2-Related Factor 2 and Forkhead BoxO 1/3 is Responsible for Sepantronium Bromide's Poor Efficacy and Resistance in Cancer cells: Opportunity for Combination Therapy in Triple Negative Breast Cancer.

Survivin, a cancer-cell-specific multifunctional protein, is regulated by many oncogenic signaling pathways and an effective therapeutic target. Although, several types of survivin-targeting agents have been developed over the past few decades, none of them received clinical approval. This could be because survivin expression is tightly controlled by the feedback interaction between different signaling molecules. Of the several signaling pathways that are known to regulate survivin expression, the phosphatidylinositol 3-kinase/AKT serine-threonine kinase/forkhead boxO (PI3K/AKT/FoxO) pathway is well-known for feedback loops constructed by cross-talk among different molecules. Using sepantronium bromide (YM155), the first of its class of survivin-suppressant, we uncovered the existence of an interesting cross-talk between Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) and FoxO transcription factors that also contributes to YM155 resistance in triple negative breast cancer (TNBC) cells. Pharmacological manipulation to interrupt this interaction not only helped restore/enhance the drug-sensitivity but also prompted effective immune clearance of cancer cells. Because the YM155-induced reactive oxygen species (ROS) initiates this feedback, we believe that it will be occurring for many ROS-producing chemotherapeutic agents. Our work provides a rational explanation for the poor efficacy of YM155 compared to standard chemotherapy in clinical trials. Finally, the triple drug combination approach used herein might help reintroducing YM155 into the clinical pipeline, and given the high survivin expression in TNBC cells in general, it could be effective in treating this subtype of breast cancer.

Senescence-Induced Chemoresistance in Triple Negative Breast Cancer and Evolution-Based Treatment Strategies.

Triple negative breast cancer (TNBC) is classically treated with combination chemotherapies. Although, initially responsive to chemotherapies, TNBC patients frequently develop drug-resistant, metastatic disease. Chemotherapy resistance can develop through many mechanisms, including induction of a transient growth-arrested state, known as the therapy-induced senescence (TIS). In this paper, we will focus on chemoresistance in TNBC due to TIS. One of the key characteristics of senescent cells is a complex secretory phenotype, known as the senescence-associated secretory proteome (SASP), which by prompting immune-mediated clearance of senescent cells maintains tissue homeostasis and suppresses tumorigenesis. However, in cancer, particularly with TIS, senescent cells themselves as well as SASP promote cellular reprograming into a stem-like state responsible for the emergence of drug-resistant, aggressive clones. In addition to chemotherapies, outcomes of recently approved immune and DNA damage-response (DDR)-directed therapies are also affected by TIS, implying that this a common strategy used by cancer cells for evading treatment. Although there has been an explosion of scientific research for manipulating TIS for prevention of drug resistance, much of it is still at the pre-clinical stage. From an evolutionary perspective, cancer is driven by natural selection, wherein the fittest tumor cells survive and proliferate while the tumor microenvironment influences tumor cell fitness. As TIS seems to be preferred for increasing the fitness of drug-challenged cancer cells, we will propose a few tactics to control it by using the principles of evolutionary biology. We hope that with appropriate therapeutic intervention, this detrimental cellular fate could be diverted in favor of TNBC patients.