Diazoxide-mediated growth inhibition in human lung cancer cells via downregulation of beta-catenin-mediated cyclin D1 transcription

Discovery of Halogenated Benzothiadiazine Derivatives with Anticancer Activity*

Mitochondrial respiratory complex II (CII), also known as succinate dehydrogenase, plays a critical role in mitochondrial metabolism. Known but low potency CII inhibitors are selectively cytotoxic to cancer cells including the benzothiadiazine-based anti-hypoglycemic diazoxide. Herein, we study the structure-activity relationship of benzothiadiazine derivatives for CII inhibition and their effect on cancer cells for the first time. A 15-fold increase in CII inhibition was achieved over diazoxide, albeit with micromolar IC₅₀ values. Cytotoxicity evaluation of the novel derivatives resulted in the identification of compounds with much greater antineoplastic effect than diazoxide, the most potent of which possesses an IC₅₀ of 2.93±0.07 μM in a cellular model of triple-negative breast cancer, with high selectivity over nonmalignant cells and more than double the potency of the clinical agent 5-fluorouracil. No correlation between cytotoxicity and CII inhibition was found, thus indicating an as-yet-undefined mechanism of action of this scaffold. The derivatives described herein represent valuable hit compounds for therapeutic discovery in triple-negative breast cancer.

Dietary and pharmacological modification of the insulin/IGF-1 system: exploiting the full repertoire against cancer

As more and more links between cancer and metabolism are discovered, new approaches to treat cancer using these mechanisms are considered. Dietary restriction of either calories or macronutrients has shown great potential in animal studies to both reduce the incidence and growth of cancer, and to act synergistically with other treatment strategies. These studies have also shown that dietary restriction simultaneously targets many of the molecular pathways that are targeted individually by anticancer drugs. The insulin/insulin-like growth factor-1 (IGF-1) system has thereby emerged as a key regulator of cancer growth pathways. Although lowering of insulin levels with diet or drugs such as metformin and diazoxide seems generally beneficial, some practitioners also utilize strategic elevations of insulin levels in combination with chemotherapeutic drugs. This indicates a broad spectrum of possibilities for modulating the insulin/IGF-1 system in cancer treatment. With a specific focus on dietary restriction, insulin administration and the insulin-lowering drug diazoxide, such modifications of the insulin/IGF-1 system are the topic of this review. Although preclinical data are promising, we point out that insulin regulation and the metabolic response to a certain diet often differ between mice and humans. Thus, the need for collecting more human data has to be emphasized.

MicroRNA-33a inhibits lung cancer cell proliferation and invasion by regulating the expression of β-catenin

MicroRNAs (miRNAs) are short, non‑coding RNAs that are aberrantly expressed in tumors. miRNA‑33a (miR‑33a) is closely associated with cholesterol metabolism and is essential for cellular growth. The aim of the present study was to explore the role of miR‑33a and identify its clinical significance in lung cancer cells. miR‑33a was observed to be overexpressed in the lung cancer cell lines A549 and NCI‑H460. MTT assay results demonstrated that the overexpression of miR‑33a significantly inhibited the proliferation of A549 cells, and similar results were obtained from the colony formation assay. This suggests that transfection of miR‑33a may suppress the growth of lung cancer cells. Overexpression of miR‑33a was also observed to result in marked G1/S phase cell cycle arrest in A549 and NCI‑H460 cell lines using fluorescence‑activated cell sorting analysis. Western blot analysis revealed that overexpression of miR‑33a significantly reduced the expression of β‑catenin in A549 and NCI‑H460 cells, suggesting a direct or indirect regulation of β‑catenin by miR‑33a in lung cancer cells. In conclusion, the current study may provide strategies for the treatment of lung cancer and clarify the mechanism of its progression.

Diazoxide pretreatment enhances L6 skeletal myoblast survival and inhibits apoptosis induced by hydrogen peroxide

Skeletal myoblast (SKM) transplantation is a promising approach to regenerate tissue and improve the function of the injured heart. However, the number of survival cells transplanted to host myocardium is quite poor due to high rate of apoptosis; diazoxide (DZ) is a highly selective mito-KATP channel opener that may reduce cell apoptosis by relieving reactive oxygen species (ROS) damage. The aim of this study is to explore the protective effects of DZ on L6 SKM damage induced by hydrogen peroxide (H(2)O(2) ) in vitro. Different dose and time of H(2)O(2) and DZ treatment were performed and only 24 hr of 1.00 mmol/L H(2) O(2) treatment and 200 μmol/L DZ pretreatment for 30 min were used for further experiment. L6 SKMs were cultured and divided into control group (no treatment), H(2)O(2) group (24 hr of 1.00 mmol/L H(2) O(2) treatment) and DZ + H(2)O(2) group (pretreated with 200 μmol/L DZ for 30 min before 24 hr of 1.00 mmol/L H(2) O(2) treatment). Compared with control group, H(2)O(2) treatment caused cell damage, increased lactate dehydrogenase release, cell apoptosis, and bax gene expression, while reduced cell proliferation and decreased bcl-2 expression. DZ pretreatment may protect cells from damage induced by H(2)O(2) and reduce cell apoptosis by increasing bcl-2 and decreasing bax expression. DZ pretreatment may also promote cell proliferation measured by both PCNA expression and flow cytometry method. These results suggest that DZ may protect L6 SKMs from damage induced by H(2)O(2) by maintaining integrity of cell membrane, reducing apoptosis and increasing proliferation in vitro.

Inhibitors of succinate: quinone reductase/Complex II regulate production of mitochondrial reactive oxygen species and protect normal cells from ischemic damage but induce specific cancer cell death

Succinate:quinone reductase (SQR) of Complex II occupies a unique central point in the mitochondrial respiratory system as a major source of electrons driving reactive oxygen species (ROS) production. It is an ideal pharmaceutical target for modulating ROS levels in normal cells to prevent oxidative stress-induced damage or alternatively,increase ROS in cancer cells, inducing cell death.The value of drugs like diazoxide to prevent ROS production,protecting normal cells, whereas vitamin E analogues promote ROS in cancer cells to kill them is highlighted. As pharmaceuticals these agents may prevent degenerative disease and their modes of action are presently being fully explored. The evidence that SDH/Complex II is tightly coupled to the NADH/NAD+ ratio in all cells,impacted by the available supplies of Krebs cycle intermediates as essential NAD-linked substrates, and the NAD+-dependent regulation of SDH/Complex II are reviewed, as are links to the NAD+-dependent dehydrogenases, Complex I and the E3 dihiydrolipoamide dehydrogenase to produce ROS. This review collates and discusses diverse sources of information relating to ROS production in different biological systems, focussing on evidence for SQR as the main source of ROS production in mitochondria, particularly its relevance to protection from oxidative stress and to the mitochondrial-targeted anti cancer drugs (mitocans) as novel cancer therapies [corrected].