Repositioning proton pump inhibitors as anticancer drugs by targeting the thioesterase domain of human fatty acid synthase

Repositioning of proton pump inhibitors in cancer therapy

Drug repositioning, as a smart way to exploit new molecular targets of a known drug, has been gaining increasing attention in the discovery of anti-cancer drugs. Proton pump inhibitors (PPIs) as benzimidazole derivatives, which are essentially H⁺-K⁺-ATPases inhibitors, are commonly used in the treatment of acid-related diseases such as gastric ulcer. In recent years, exploring the new application of PPIs in anti-cancer field has become a hot research topic. Interestingly, cancer cells display an alkaline intracellular pH and an acidic extracellular pH. The extracellular acidity of tumors can be corrected by PPIs that are selectively activated in an acid milieu. It is generally believed that PPIs might provoke disruption of pH homeostasis by targeting V-ATPase on cancer cells, which is the theoretical basis for PPIs to play an anti-cancer role. Numerous studies have shown specialized effects of the PPIs on tumor cell growth, metastasis, chemoresistance, and autophagy. PPIs may really represent new anti-cancer drugs due to better safety and tolerance, the potential selectivity in targeting tumor acidity, and the ability to inhibit mechanism pivotal for cancer homeostasis. In this review, we focus on the new therapeutic applications of PPIs in multiple cancers, explaining the rationale behind this approach and providing practical evidence.

In silico investigation of lavandulyl flavonoids for the development of potent fatty acid synthase-inhibitory prototypes

BACKGROUND

Inhibition of fatty acid synthase (FAS) is regarded as a sensible therapeutic strategy for the development of optimal anti-cancer agents. Flavonoids exhibit potent anti-neoplastic properties.

METHODS

The MeOH extract of Sophora flavescens was subjected to chromatographic analyses such as VLC and HPLC for the purification of active flavonoids. The DP4 chemical-shift analysis protocol was employed to investigate the elusive chirality of the lavandulyl moiety of the purified polyphenols. Induced Fit docking protocols and per-residue analyses were utilized to scrutinize structural prerequisites for hampering FAS activity. The FAS-inhibitory activity of the purified flavonoids was assessed via the incorporation of [³H] acetyl-CoA into palmitate.

RESULTS

Six flavonoids, including lavandulyl flavanones, were purified and evaluated for FAS inhibition. The lavandulyl flavanone sophoraflavanone G (2) exhibited the highest potency (IC₅₀ of 6.7±0.2μM), which was more potent than the positive controls. Extensive molecular docking studies revealed the structural requirements for blocking FAS. Per-residue interaction analysis demonstrated that the lavandulyl functional group in the active flavonoids (1-3 and 5) significantly contributed to increasing their binding affinity towards the target enzyme.

CONCLUSION

This research suggests a basis for the in silico design of a lavandulyl flavonoid-based architecture showing anti-cancer effects via enhancement of the binding potential to FAS.

GENERAL SIGNIFICANCE

FAS inhibition by flavonoids and their derivatives may offer significant potential as an approach to lower the risk of various cancer diseases and related fatalities. In silico technologies with available FAS crystal structures may be of significant use in optimizing preliminary leads.

In vivo and in vitro protective effects of omeprazole against neuropathic pain

Apart from reducing the acid secretion, omeprazole inhibits activation of the nuclear factor-κB, release of inflammatory cytokines, and chemotaxis of neutrophils. These mechanisms prompted us to evaluate antineuropathic effect of omeprazole in the chronic constriction injury (CCI)-induced rat model of neuropathic pain and LPS mediated ROS-induced U-87 cells. Omeprazole at 50 mg/kg/day/oral for 14 days significantly reduced the intensity of neuropathic pain estimated as paw withdrawal latency, withdrawal pressure threshold and restored the motor nerve conduction velocity in the constricted nerve, when compared with respective groups. The histological findings revealed the protective effect of omeprazole against the CCI-induced damage. Omeprazole significantly decreased the levels of tumor necrosis factor (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) as compared to their respective control groups. It also reduced the oxidative stress by up regulating the SOD, catalase activity and decreasing MDA content. Similarly, in-vitro study, LPS mediated ROS-induced U-87 cells, omeprazole reduced the oxidative stress as well as the release of TNF-α, IL-1β and IL-6. Altogether, these results suggest that, neuroprotective effect of omeprazole is mediated through preventing release of proinflammatory cytokines, augmenting endogenous anti-oxidant defense system, and maintain the structural integrity of sciatic nerve from the CCI-induced structural damage and inflammatory changes.

Reprogramming of glucose, fatty acid and amino acid metabolism for cancer progression

Metabolic reprogramming is widely observed during cancer development to confer cancer cells the ability to survive and proliferate, even under the stressed, such as nutrient-limiting, conditions. It is famously known that cancer cells favor the "Warburg effect", i.e., the enhanced glycolysis or aerobic glycolysis, even when the ambient oxygen supply is sufficient. In addition, deregulated anabolism/catabolism of fatty acids and amino acids, especially glutamine, serine and glycine, have been identified to function as metabolic regulators in supporting cancer cell growth. Furthermore, extensive crosstalks are being revealed between the deregulated metabolic network and cancer cell signaling. These exciting advancements have inspired new strategies for treating various malignancies by targeting cancer metabolism. Here we review recent findings related to the regulation of glucose, fatty acid and amino acid metabolism, their crosstalk, and relevant cancer therapy strategy.

Loss of fatty acid synthase suppresses the malignant phenotype of colorectal cancer cells by down-regulating energy metabolism and mTOR signaling pathway

PURPOSE

Altered cellular metabolism has received increased attention as an important hallmark of cancer. Activation of FASN has been found to be involved in many human tumors. Despite extensive research in FASN function on cancer, the underlying mechanism is not entirely understood yet.

METHODS

Cerulenin was used to suppress the FASN expression in human colorectal cancer cell lines (HT29 and LoVo). Expression of PI3K, Akt, p-Akt, mTOR, p-mTOR, FASN, and AZGP1 was measured using western blotting and qPCR. ATP and lactic acid were assessed to investigate the activation of energy metabolism. Cell cytotoxicity assay was studied by cell counting kit-8 assay. The capacity of cell proliferation and migration was investigated by clonogenic and invasion assay. Analysis of apoptosis and the cell cycle was detected by flow cytometry.

RESULTS

We found that the expression of FASN was down-regulated, while the expression of PI3K, p-Akt, p-mTOR, and AZGP1 was down-regulated in HT29 and LoVo cells treated with FASN inhibitor. Proliferation was reduced in FASN inhibitor-treated cells, which is consistent with an increased apoptosis rate. Furthermore, the migration of FASN inhibitor-treated cells was decreased and the content of ATP and lactic acid was also dropped.

CONCLUSION

These findings suggest that inhibited FASN suppresses the malignant phenotype of colorectal cancer cells by down-regulating energy metabolism and mTOR signaling pathway. The results have paved the way to understand the relations of FASN, mTOR signaling pathway, and energy metabolism in colorectal cancer cells.

α-Carbonic Anhydrases Possess Thioesterase Activity

The α-carbonic anhydrases (CAs, EC 4.2.1.1) show catalytic versatility acting as esterases with carboxylic, sulfonic, and phosphate esters. Here we prove by kinetic, spectroscopic, and MS studies that they also possess thioesterase activity with a dithiocarbamate ester as a substrate (PhSO2NHCSSMe). Its CA-mediated hydrolysis leads to benzenesulfonamide, methyl mercaptan, and COS. The CA thioesterase activity may be useful for designing prodrug enzyme inhibitors, whereas some CA isoforms may use this activity for modulating physiologic/pathologic processes, which are possibly amenable to drug discovery of agents with multiple mechanisms of action.