Buckling forces and the wavy folds between pleural epithelial cells.

Cell shapes in tissues are affected by the biophysical interaction between cells. Tissue forces can influence specific cell features such as cell geometry and cell surface area. Here, we examined the 2-dimensional shape, size, and perimeter of pleural epithelial cells at various lung volumes. We demonstrated a 1.53-fold increase in 2-dimensional cell surface area and a 1.43-fold increase in cell perimeter at total lung capacity compared to residual lung volume. Consistent with previous results, close inspection of the pleura demonstrated wavy folds between pleural epithelial cells at all lung volumes. To investigate a potential explanation for the wavy folds, we developed a physical simulacrum suggested by D'Arcy Thompson in On Growth and Form. The simulacrum suggested that the wavy folds were the result of redundant cell membranes unable to contract. To test this hypothesis, we developed a numerical simulation to evaluate the impact of an increase in 2-dimensional cell surface area and cell perimeter on the shape of the cell-cell interface. Our simulation demonstrated that an increase in cell perimeter, rather than an increase in 2-dimensional cell surface area, had the most direct impact on the presence of wavy folds. We conclude that wavy folds between pleural epithelial cells reflects buckling forces arising from the excess cell perimeter necessary to accommodate visceral organ expansion.

Repression of LSD1 potentiates homologous recombination-proficient ovarian cancer to PARP inhibitors through down-regulation of BRCA1/2 and RAD51.

Poly (ADP-ribose) polymerase inhibitors (PARPi) are selectively active in ovarian cancer (OC) with homologous recombination (HR) deficiency (HRD) caused by mutations in BRCA1/2 and other DNA repair pathway members. We sought molecular targeted therapy that induce HRD in HR-proficient cells to induce synthetic lethality with PARPi and extend the utility of PARPi. Here, we demonstrate that lysine-specific demethylase 1 (LSD1) is an important regulator for OC. Importantly, genetic depletion or pharmacological inhibition of LSD1 induces HRD and sensitizes HR-proficient OC cells to PARPi in vitro and in multiple in vivo models. Mechanistically, LSD1 inhibition directly impairs transcription of BRCA1/2 and RAD51, three genes essential for HR, dependently of its canonical demethylase function. Collectively, our work indicates combination with LSD1 inhibitor could greatly expand the utility of PARPi to patients with HR-proficient tumor, warranting assessment in human clinical trials.

Synthesis and biological evaluation of novel pyrazole amides as potent mitochondrial complex I inhibitors.

Targeting mitochondrial complex I (CI) is emerging as an attractive anticancer strategy, and CI inhibitor IACS-010759 has achieved breakthrough success. However, the narrow therapeutic index of IACS-010759 seriously hinders its further application. In this study, a series of novel pyrazole amides were designed and optimized based on IACS-010759, and their potential CI inhibitory effects were biologically evaluated. Among them, the maximum tolerated dose (MTD) values of SCAL-255 (compound 5q) and SCAL-266 (compound 6f) were 68 mg/kg, which was nearly 10 times that of IACS-010759 (6 mg/kg), showing good safety. In addition, SCAL-255 and SCAL-266 significantly inhibited the proliferation of HCT116 and KG-1 cells in vitro and exerted satisfactory inhibitory activity against KG-1 cells in vivo. These results suggested that the optimized compounds might serve as promising CI inhibitors against oxidative phosphorylation (OXPHOS)-dependent cancer, which merits further study.

Pharmacological inhibition of LSD1 suppresses growth of hepatocellular carcinoma by inducing GADD45B.

Lysine-specific histone demethylase 1 (LSD1) is an attractive target for malignancies therapy. Nevertheless, its role in hepatocellular carcinoma (HCC) progression and the potential of its inhibitor in HCC therapy remains unclear. Here, we show that LSD1 overexpression in human HCC tissues is associated with HCC progression and poor patient survival. ZY0511, a highly selective and potent inhibitor of LSD1, suppressed human HCC cell proliferation in vitro and tumor growth in cell-derived and patient-derived HCC xenograft models in vivo. Mechanistically, ZY0511 induced mRNA expression of growth arrest and DNA damage-inducible gene 45beta (GADD45B) by inducing histone H3 at lysine 4 (H3K4) methylation at the promoter of GADD45B, a novel target gene of LSD1. In human HCC tissues, LSD1 level was correlated with a decreased level of GADD45B, which was associated with HCC progression and predicted poor patient survival. Moreover, co-administration of ZY0511 and DTP3, which specifically enhanced the pro-apoptotic effect of GADD45B, effectively inhibited HCC cell proliferation both in vitro and in vivo. Collectively, our study revealed the potential value of LSD1 as a promising target of HCC therapy. ZY0511 is a promising candidate for HCC therapy through upregulating GADD45B, thereby providing a novel combinatorial strategy for treating HCC.

Discovery of potent human dihydroorotate dehydrogenase inhibitors based on a benzophenone scaffold.

Blocking the de novo biosynthesis of pyrimidine by inhibiting human dihydroorotate dehydrogenase (hDHODH) is an effective way to suppress the proliferation of cancer cells and activated lymphocytes. Herein, eighteen teriflunomide derivatives and four ASLAN003 derivatives were designed and synthesized as novel hDHODH inhibitors based on a benzophenone scaffold. The optimal compound 7d showed a potent hDHODH inhibitory activity with an IC50 value of 10.9 nM, and displayed promising antiproliferative activities against multiple human cancer cells with IC50 values of 0.1-0.8 µM. Supplementation of exogenous uridine rescued the cell viability of 7d-treated Raji and HCT116 cells. Meanwhile, 7d significantly induced cell cycle S-phase arrest in Raji and HCT116 cells. Furthermore, 7d exhibited favorable safety profiles in mice and displayed effective antitumor activities with tumor growth inhibition (TGI) rates of 58.3% and 42.1% at an oral dosage of 30 mg/kg in Raji and HCT116 cells xenograft models, respectively. Taken together, these findings provide a promising hDHODH inhibitor 7d with potential activities against some tumors.

A novel series of teriflunomide derivatives as orally active inhibitors of human dihydroorotate dehydrogenase for the treatment of colorectal carcinoma.

Human dihydroorotate dehydrogenase (hDHODH) is a key enzyme in the de novo synthesis pathway of pyrimidine nucleotide in cells. The moderate efficiency of teriflunomide, an approved hDHODH inhibitor for the treatment of multiple sclerosis, limited its therapeutic application of malignancy. Herein, thirty-seven novel teriflunomide derivatives with a biphenyl scaffold were designed, synthesized and evaluated. As a result, the optimal compound A37 exhibited a potent hDHODH inhibitory activity with an IC50 value of 10.2 nM, which was about 40-fold stronger than that of teriflunomide (IC50 = 407.8 nM), and showed favorable antiproliferative activities against HCT116 cells with an IC50 value of 0.3 µM. Meanwhile, A37 displayed an acceptable safety profile at an oral dosage of 400 mg/kg in the acute toxicity assay, and exhibited a promising antitumor effect with tumor growth inhibition rate of 54.4% at an oral dosage of 30 mg/kg in HCT116 xenograft model. These results indicate that A37 is an efficacious hDHODH inhibitor with potential in the treatment of colorectal carcinoma.

Biophysical and biochemical properties of PHGDH revealed by studies on PHGDH inhibitors.

The rate-limiting serine biogenesis enzyme PHGDH is overexpressed in cancers. Both serine withdrawal and genetic/pharmacological inhibition of PHGDH have demonstrated promising tumor-suppressing activities. However, the enzyme properties of PHGDH are not well understood and the discovery of PHGDH inhibitors is still in its infancy. Here, oridonin was identified from a natural product library as a new PHGDH inhibitor. The crystal structure of PHGDH in complex with oridonin revealed a new allosteric site. The binding of oridonin to this site reduced the activity of the enzyme by relocating R54, a residue involved in substrate binding. Mutagenesis studies showed that PHGDH activity was very sensitive to cysteine mutations, especially those in the substrate binding domain. Conjugation of oridonin and other reported covalent PHGDH inhibitors to these sites will therefore inhibit PHGDH. In addition to being inhibited enzymatically, PHGDH can also be inhibited by protein aggregation and proteasome-mediated degradation. Several tested PHGDH cancer mutants showed altered enzymatic activity, which can be explained by protein structure and stability. Overall, the above studies present new biophysical and biochemical insights into PHGDH and may facilitate the future design of PHGDH inhibitors.

Design, Synthesis, and Biological Evaluation of a Novel Series of Teriflunomide Derivatives as Potent Human Dihydroorotate Dehydrogenase Inhibitors for Malignancy Treatment.

Human dihydroorotate dehydrogenase (hDHODH), as the fourth and rate-limiting enzyme of the de novo pyrimidine synthesis pathway, is regarded as an attractive target for malignancy therapy. In the present study, a novel series of teriflunomide derivatives were designed, synthesized, and evaluated as hDHODH inhibitors. 13t was the optimal compound with promising enzymatic activity (IC50 = 16.0 nM), potent antiproliferative activity against human lymphoma Raji cells (IC50 = 7.7 nM), and excellent aqueous solubility (20.1 mg/mL). Mechanistically, 13t directly inhibited hDHODH and induced cell cycle S-phase arrest in Raji cells. The acute toxicity assay indicated a favorable safety profile of 13t. Notably, 13t displayed significant tumor growth inhibition activity with a tumor growth inhibition (TGI) rate of 81.4% at 30 mg/kg in a Raji xenograft model. Together, 13t is a promising inhibitor of hDHODH and a preclinical candidate for antitumor therapy, especially for lymphoma.

Discovery of novel inhibitors of human phosphoglycerate dehydrogenase by activity-directed combinatorial chemical synthesis strategy.

Serine, the source of the one-carbon units essential for de novo purine and deoxythymidine synthesis plays a crucial role in the growth of cancer cells. Phosphoglycerate dehydrogenase (PHGDH) which catalyzes the first, rate-limiting step in de novo serine biosynthesis has become a promising target for the cancer treatment. Here we identified H-G6 as a potential PHGDH inhibitor from the screening of an in-house small molecule library based on the enzymatic assay. We adopted activity-directed combinatorial chemical synthesis strategy to optimize this hit compound. Compound b36 was found to be the noncompetitive and the most promising one with IC50 values of 5.96 ± 0.61 µM against PHGDH. Compound b36 inhibited the proliferation of human breast cancer and ovarian cancer cells, reduced intracellular serine synthesis, damaged DNA synthesis, and induced cell cycle arrest. Collectively, our results suggest that b36 is a novel PHGDH inhibitor, which could be a promising modulator to reprogram the serine synthesis pathway and might be a potential anticancer lead worth further exploration.

DHODH and cancer: promising prospects to be explored.

Human dihydroorotate dehydrogenase (DHODH) is a flavin-dependent mitochondrial enzyme catalyzing the fourth step in the de novo pyrimidine synthesis pathway. It is originally a target for the treatment of the non-neoplastic diseases involving in rheumatoid arthritis and multiple sclerosis, and is re-emerging as a validated therapeutic target for cancer therapy. In this review, we mainly unravel the biological function of DHODH in tumor progression, including its crucial role in de novo pyrimidine synthesis and mitochondrial respiratory chain in cancer cells. Moreover, various DHODH inhibitors developing in the past decades are also been displayed, and the specific mechanism between DHODH and its additional effects are illustrated. Collectively, we detailly discuss the association between DHODH and tumors in recent years here, and believe it will provide significant evidences and potential strategies for utilizing DHODH as a potential target in preclinical and clinical cancer therapies.

[Confocal microprobe Raman spectroscopic study of electrochemical reduction of benzene on a platinum electrode].

The electrochemical reduction of benzene on a smooth Pt electrode has been studied by confocal microprobe Raman spectroscopy. The results show that benzene can be reduced directly to cyclohexane, which is insoluble in water, adhered onto the electrode surface to form the third phase. After the drops have been formed on the electrode surface, the relative concentration of benzene to cyclohexane in the drops will rather increase with prolonging the time at a certain electrode potential, although it decreases with the negative shift of the electrode potential at first.