Aurovertin B sensitizes colorectal cancer cells to NK cell recognition and lysis

Defueling the cancer: ATP synthase as an emerging target in cancer therapy

Reprogramming of cellular metabolism is a hallmark of cancer. Mitochondrial ATP synthase (MAS) produces most of the ATP that drives the cell. High expression of the MAS-composing proteins is found during cancer and is linked to a poor prognosis in glioblastoma, ovarian cancer, prostate cancer, breast cancer, and clear cell renal cell carcinoma. Cell surface-expressed ATP synthase, translocated from mitochondrion to cell membrane, involves the angiogenesis, tumorigenesis, and metastasis of cancer. ATP synthase has therefore been considered a therapeutic target. We review recent various ATP synthase inhibitors that suppress tumor growth and are being tested for the clinic.

The diterpenoid adenanthin upregulates the expression of natural killer group 2D receptor ligands in hepatocellular carcinoma cells

OBJECTIVE

The natural killer (NK) group 2D (NKG2D) receptor plays a crucial role in NK cell-mediated anti-tumor immunity. NKG2D anti-proliferative effect is mediated by direct interactions of the receptor with its ligands that may be considered as a potential target for NK-based immunotherapeutic strategy in cancer cells.

METHODS

Here we report that a natural product adenanthin significantly promotes NKG2D ligands expression in hepatoma cells. The effect was determined using flow cytometry analysis. The activity of NK cell was evaluated by measuring its degranulation activity and cytotoxicity.

RESULTS

Our data indicates that the induction of NKG2D ligand binding to liver cancer cell surface receptors greatly improves the killing activity of NK cells against the cancer cells.

CONCLUSIONS

This is the first report of a new mechanism anti-cancer effects of adenanthin mediated by an indirect activation of NK cells. Our data suggests that adenanthin may be used to sensitize NK cells in tumor immunotherapy.

Natural products and other inhibitors of F1FO ATP synthase

F₁F_O ATP synthase is responsible for the production of >95% of all ATP synthesis within the cell. Dysregulation of its expression, activity or localization is linked to various human diseases including cancer, diabetes, and Alzheimer's and Parkinson's disease. In addition, ATP synthase is a novel and viable drug target for the development of antimicrobials as evidenced by bedaquiline, which was approved in 2012 for the treatment of tuberculosis. Historically, natural products have been a rich source of ATP synthase inhibitors that help unravel the role of F₁F_O ATP synthase in cellular bioenergetics. During the last decade, new modulators of ATP synthase have been discovered through the isolation of novel natural products as well as through a ligand-based drug design process. In addition, new data has been obtained with regards to the structure and function of ATP synthase under physiological and pathological conditions. Crystal structure studies have provided a significant insight into the rotary function of the enzyme and may provide additional opportunities to design a new generation of inhibitors. This review provides an update on recently discovered ATP synthase modulators as well as an update on existing scaffolds.

Anticancer fungal natural products: Mechanisms of action and biosynthesis

Many fungal metabolites show promising anticancer properties both in vitro and in animal models, and some synthetic analogs of those metabolites have progressed into clinical trials. However, currently, there are still no fungi-derived agents approved as anticancer drugs. Two potential reasons could be envisioned: 1) lacking a clear understanding of their anticancer mechanism of action, 2) unable to supply enough materials to support the preclinical and clinic developments. In this review, we will summarize recent efforts on elucidating the anticancer mechanisms and biosynthetic pathways of several promising anticancer fungal natural products.

Astragaloside III Enhances Anti-Tumor Response of NK Cells by Elevating NKG2D and IFN-γ

Natural killer (NK) cells play an irreplaceable role in the development of colon cancer, in which antitumor function of NK cells was impaired. Astragaloside III is a natural compound from Astragalus that has been shown to have immunomodulatory effects in various systems. However, few studies have evaluated the antitumor effects of Astragaloside III through stimulating systemic immunity and regulating NK cells. In this study, flow cytometry, immunohistochemical analysis, and immunofunctional assays were performed to elucidate the functions of Astragaloside III in restoring antitumor function of NK cells. We demonstrated that Astragaloside III significantly elevated the expression of natural killer group 2D (NKG2D), Fas, and interferon-γ (IFN-γ) production in NK cells, leading to increased tumor-killing ability. Experiments in cell co-culture assays and CT26-bearing mice model further confirmed that Astragaloside III could effectively impede tumor growth by increasing infiltration of NK cells into tumor and upregulating the antitumor response of NK cells. We further revealed that Astragaloside III increased IFN-γ secretion of NK cells by enhancing the expression of transcription factor T-bet. In conclusion, the effective anti-tumor function of Astragaloside III was achieved through up-regulation of the immune response of NK cells and elevation of NKG2D, Fas, and IFN-γ production.