Oncogenic KRAS Induces Arginine Auxotrophy and Confers a Therapeutic Vulnerability to SLC7A1 Inhibition in Non-Small Cell Lung Cancer.

The urea cycle is frequently rewired in cancer cells to meet the metabolic demands of cancer. Elucidation of the underlying mechanism by which oncogenic signaling mediates urea cycle reprogramming could help identify targetable metabolic vulnerabilities. In this study, we discovered that oncogenic activation of KRAS in non-small cell lung cancer (NSCLC) silenced the expression of argininosuccinate synthase 1 (ASS1), a urea cycle enzyme that catalyzes the production of arginine from aspartate and citrulline, and thereby diverted the utilization of aspartate to pyrimidine synthesis to meet the high demand for DNA replication. Specifically, KRAS signaling facilitated a hypoacetylated state in the promoter region of the ASS1 gene in a histone deacetylase 3-dependent manner, which in turn impeded the recruitment of c-MYC for ASS1 transcription. ASS1 suppression in KRAS-mutant NSCLC cells impaired the biosynthesis of arginine and rendered a dependency on the arginine transmembrane transporter SLC7A1 to import extracellular arginine. Depletion of SLC7A1 in both patient-derived organoid and xenograft models inhibited KRAS-driven NSCLC growth. Together, these findings uncover the role of oncogenic KRAS in rewiring urea cycle metabolism and identify SLC7A1-mediated arginine uptake as a therapeutic vulnerability for treating KRAS-mutant NSCLC. SIGNIFICANCE: ASS1 deficiency is induced by mutant KRAS in NSCLC to facilitate DNA synthesis and creates a dependency on SLC7A1, revealing dietary arginine restriction and SLC7A1 inhibition as potential therapeutic strategies.

Tetrandrine synergizes with MAPK inhibitors in treating KRAS-mutant pancreatic ductal adenocarcinoma via collaboratively modulating the TRAIL-death receptor axis.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal malignancies lacking effective therapies. KRAS mutations that occur in over 90% of PDAC are major oncogenic drivers of PDAC. The MAPK signaling pathway plays a central role in KRAS-driven oncogenic signaling. However, pharmacological inhibitors of the MAPK pathway are poorly responded in KRAS-mutant PDAC, raising a compelling need to understand the mechanism behind and to seek new therapeutic solutions. Herein, we perform a screen utilizing a library composed of 800 naturally-derived bioactive compounds to identify natural products that are able to sensitize KRAS-mutant PDAC cells to the MAPK inhibition. We discover that tetrandrine, a natural bisbenzylisoquinoline alkaloid, shows a synergistic effect with MAPK inhibitors in PDAC cells and xenograft models. Mechanistically, pharmacological inhibition of the MAPK pathway exhibits a double-edged impact on the TRAIL-death receptor axis, transcriptionally upregulating TRAIL yet downregulating its agonistic receptors DR4 and DR5, which may explain the limited therapeutic outcomes of MAPK inhibitors in KRAS-mutant PDAC. Of great interest, tetrandrine stabilizes DR4/DR5 protein via impairing ubiquitination-mediated protein degradation, thereby allowing a synergy with MAPK inhibition in inducing apoptosis in KRAS-mutant PDAC. Our findings identify a new combinatorial approach for treating KRAS-mutant PDAC and highlight the role of TRAIL-DR4/DR5 axis in dictating the therapeutic outcome in KRAS-mutant PDAC.

Discovery of Novel Drug-like PHGDH Inhibitors to Disrupt Serine Biosynthesis for Cancer Therapy.

Being the rate-limiting enzyme within the serine biosynthesis pathway, phosphoglycerate dehydrogenase (PHGDH) is abnormally overexpressed in numerous malignant tumor cells and is a promising target for cancer treatment. Here, we report a series of novel PHGDH inhibitors using a focused compound screening and structural optimization approach. The lead compound D8 displayed good enzymatic inhibitory activity (IC50 = 2.8 ± 0.1 µM), high binding affinity (Kd = 2.33 µM), and sensitivity to the cell lines with the PHGDH gene amplification or overexpression. Furthermore, D8 was proven to restrict the de novo serine synthesis from glucose within MDA-MB-468 cells. X-ray crystallographic analysis, molecular dynamics simulations, and mutagenesis experiments on PHGDH revealed the binding site at D175 inside the NAD+-binding pocket. Finally, D8 exhibited excellent in vivo pharmacokinetic properties (F = 82.0%) and exerted evident antitumor efficacy in the PC9 xenograft mouse model.

SLC1A1-mediated cellular and mitochondrial influx of R-2-hydroxyglutarate in vascular endothelial cells promotes tumor angiogenesis in IDH1-mutant solid tumors.

Mutant isocitrate dehydrogenase 1 (mIDH1) drives tumorigenesis via producing oncometabolite R-2-hydroxyglutarate (R-2-HG) across various tumor types. However, mIDH1 inhibitors appear only effective in hematological tumors. The therapeutic benefit in solid tumors remains elusive, likely due to the complex tumor microenvironment. In this study, we discover that R-2-HG produced by IDH1-mutant tumor cells is preferentially imported into vascular endothelial cells and remodels mitochondrial respiration to promote tumor angiogenesis, conferring a therapeutic vulnerability in IDH1-mutant solid tumors. Mechanistically, SLC1A1, a Na+-dependent glutamate transporter that is preferentially expressed in endothelial cells, facilitates the influx of R-2-HG from the tumor microenvironment into the endothelial cells as well as the intracellular trafficking of R-2-HG from cytoplasm to mitochondria. R-2-HG hijacks SLC1A1 to promote mitochondrial Na+/Ca2+ exchange, which activates the mitochondrial respiratory chain and fuels vascular endothelial cell migration in tumor angiogenesis. SLC1A1 deficiency in mice abolishes mIDH1-promoted tumor angiogenesis as well as the therapeutic benefit of mIDH1 inhibitor in solid tumors. Moreover, we report that HH2301, a newly discovered mIDH1 inhibitor, shows promising efficacy in treating IDH1-mutant cholangiocarcinoma in preclinical models. Together, we identify a new role of SLC1A1 as a gatekeeper of R-2-HG-mediated crosstalk between IDH1-mutant tumor cells and vascular endothelial cells, and demonstrate the therapeutic potential of mIDH1 inhibitors in treating IDH1-mutant solid tumors via disrupting R-2-HG-promoted tumor angiogenesis.

Discovery of PHGDH inhibitors by virtual screening and preliminary structure-activity relationship study.

Phosphoglycerate dehydrogenase (PHGDH) is abnormally expressed in numerous malignant tumor cells and catalyzes the first step of serine biosynthesis, thus becoming a key drug target for antitumor treatment. In this study, compound B2 bearing a benzene-1,3-diamine scaffold was identified by structure-based virtual screening as a novel PHGDH inhibitor with moderate enzymatic activity. The structure-activity relationship study led to the discovery of compound C25 possessing improved enzymatic inhibitory activity and potent inhibitory activity on the proliferation of cells overexpressing PHGDH. The enzyme kinetic assay confirmed that C25 inhibited PHGDH in a nicotinamide adenine dinucleotide (NAD+) competitive manner. Molecular docking and mutagenesis experiment on PHGDH collectively revealed the binding site and key interaction residues of C25 in the PHGDH catalytic site. Taken together, this study provides information on the structural diversity for a further development of potent PHGDH inhibitors.

Identification of metabolic vulnerabilities of receptor tyrosine kinases-driven cancer.

One of the biggest hurdles for the development of metabolism-targeted therapies is to identify the responsive tumor subsets. However, the metabolic vulnerabilities for most human cancers remain unclear. Establishing the link between metabolic signatures and the oncogenic alterations of receptor tyrosine kinases (RTK), the most well-defined cancer genotypes, may precisely direct metabolic intervention to a broad patient population. By integrating metabolomics and transcriptomics, we herein show that oncogenic RTK activation causes distinct metabolic preference. Specifically, EGFR activation branches glycolysis to the serine synthesis for nucleotide biosynthesis and redox homeostasis, whereas FGFR activation recycles lactate to fuel oxidative phosphorylation for energy generation. Genetic alterations of EGFR and FGFR stratify the responsive tumors to pharmacological inhibitors that target serine synthesis and lactate fluxes, respectively. Together, this study provides the molecular link between cancer genotypes and metabolic dependency, providing basis for patient stratification in metabolism-targeted therapies.

Design, synthesis and biological evaluation of tetrahydronaphthyridine derivatives as bioavailable CDK4/6 inhibitors for cancer therapy.

CDK4/6 pathway is an attractive chemotherapeutic target for antitumor drug discovery and development. Herein, we reported the structure-based design and synthesis of a series of novel tetrahydronaphthyridine analogues as selective CDK4/6 inhibitors. Compound 5 was identified as a hit and then systematically structure optimization study was conducted. These efforts led to compound 28, which exhibited excellent in vitro potencies against CDK4/6 enzymatic activity with high selectivity over CDK1, and against Colo-205 cell growth. The compound demonstrated favorable in vitro metabolic and robust mice pharmacokinetic properties. In Colo-205 xenograft models, compound 28 showed potent tumor growth inhibition with acceptable toxic effects, which could serve as a novel anticancer agent for further preclinical study.

Discovery of a class of diheteroaromatic amines as orally bioavailable CDK1/4/6 inhibitors.

The discovery of a class of diheteroaromatic amines based on LY2835219 as cyclin-dependent kinase (CDK1/4/6) inhibitors was described. The series was found to have much more improved CDK1 inhibition and potent in vitro anti-proliferative effects against cancer cell lines. The synthesis and structure-activity relationship studies of these compounds were reported. One promising compound was selected to evaluate as a novel lead compound after in vitro and in vivo profiling.

Discovery and structure-activity-relationship study of novel conformationally restricted indane analogues for mutant isocitric dehydrogenase 1 (IDH1) inhibitors.

The discovery and optimization of various of indane amides as mutant IDH1 inhibitors via structure-based rational design were reported. The optimal compounds demonstrated both potent inhibition in IDH1R132H enzymatic activity and 2HG production in IDH1 mutant HT1080 cell line, favorable PK properties and great selectivity against IDH1wt and IDH2R140Q.

Feedback Activation of Leukemia Inhibitory Factor Receptor Limits Response to Histone Deacetylase Inhibitors in Breast Cancer.

Histone deacetylase (HDAC) inhibitors have demonstrated clinical benefits in subtypes of hematological malignancies. However, the efficacy of HDAC inhibitors in solid tumors remains uncertain. This study takes breast cancer as a model to understand mechanisms accounting for limited response of HDAC inhibitors in solid tumors and to seek combination solutions. We discover that feedback activation of leukemia inhibitory factor receptor (LIFR) signaling in breast cancer limits the response to HDAC inhibition. Mechanistically, HDAC inhibition increases histone acetylation at the LIFR gene promoter, which recruits bromodomain protein BRD4, upregulates LIFR expression, and activates JAK1-STAT3 signaling. Importantly, JAK1 or BRD4 inhibition sensitizes breast cancer to HDAC inhibitors, implicating combination inhibition of HDAC with JAK1 or BRD4 as potential therapies for breast cancer.

Merremins A-G, resin glycosides from Merremia hederacea with multidrug resistance reversal activity.

Five new pentasaccharide resin glycosides, named merremins A-E (1-5), two new pentasaccharide resin glycoside methyl esters, named merremins F and G (6, 7), and four known resin glycosides, murucoidin IV, murucoidin V, stoloniferin IV, and murucoidin XVII, were obtained from the aerial parts of Merremia hederacea. This is the first report of resin glycosides obtained from M. hederacea. In addition, the new compounds can be divided into three types: those possessing an 18-membered ring (1-4), compound 5 with a 20-membered ring, and those with an acyclic core (6, 7). Furthermore, the different types of resin glycosides were evaluated for their multidrug resistance reversal activities. Compounds 1, 5, 6, and murucoidin V were noncytotoxic and enhanced the cytotoxicity of vinblastine by 2.3-142.5-fold at 25 µM. Compound 5 and murucoidin V, with 20-membered rings, were more active than compound 1, with an 18-membered ring.