Pharmacological modulation of oncogenic Ras by natural products and their derivatives: renewed hope in the discovery of novel anti-Ras drugs

Oncogenic rat sarcoma (Ras) is linked to the most fatal cancers such as those of the pancreas, colon, and lung. Decades of research to discover an efficacious drug that can block oncogenic Ras signaling have yielded disappointing results; thus, Ras was considered “undruggable” until recently. Inhibitors that directly target Ras by binding to previously undiscovered pockets have been recently identified. Some of these molecules are either isolated from natural products or derived from natural compounds. In this review, we described the potential of these compounds and other inhibitors of Ras signaling in drugging Ras. We highlighted the modes of action of these compounds in suppressing signaling pathways activated by oncogenic Ras, such as mitogen-activated protein kinase (MAPK) signaling and the phosphoinositide-3-kinase (PI3K) pathways. The anti-Ras strategy of these compounds can be categorized into four main types: inhibition of Ras–effector interaction, interference of Ras membrane association, prevention of Ras–guanosine triphosphate (GTP) formation, and downregulation of Ras proteins. Another promising strategy that must be validated experimentally is enhancement of the intrinsic Ras–guanosine triphosphatase (GTPase) activity by small chemical entities. Among the inhibitors of Ras signaling that were reported thus far, salirasib and TLN-4601 have been tested for their clinical efficacy. Although both compounds passed phase I trials, they failed in their respective phase II trials. Therefore, new compounds of natural origin with relevant clinical activity against Ras-driven malignancies are urgently needed. Apart from salirasib and TLN-4601, some other compounds with a proven inhibitory effect on Ras signaling include derivatives of salirasib, sulindac, polyamine, andrographolide, lipstatin, levoglucosenone, rasfonin, and quercetin

In silico and saturation transfer difference NMR approaches to unravel the binding mode of an andrographolide derivative to K-Ras oncoprotein

Background: Andrographolide and its benzylidene derivatives, SRJ09 and SRJ23, potentially bind oncogenic K-Ras to exert anticancer activity. Their molecular interactions with K-Ras oncoproteins that lead to effective biological activity are of major interest. Methods & results: In silico docking and molecular dynamics simulation were performed using Glide and Desmond, respectively; while saturation transfer difference NMR was performed using GDP-bound K-RasG12V. SRJ23 was found to bind strongly and selectively to K-RasG12V, by anchoring to a binding pocket (namely p2) principally via hydrogen bond and hydrophobic interactions. The saturation transfer difference NMR analysis revealed the proximity of protons of functional moieties in SRJ23 to K-RasG12V, suggesting positive binding. Conclusion: SRJ23 binds strongly and interacts stably with K-RasG12V to exhibit its inhibitory activity

Injectable liposomal docosahexaenoic acid alleviates atherosclerosis progression and enhances plaque stability

Atherosclerosis is a chronic inflammatory vascular disease that is characterized by the accumulation of lipids and immune cells in plaques built up inside artery walls. Docosahexaenoic acid (DHA, 22:6n-3), an omega-3 polyunsaturated fatty acid (PUFA), which exerts anti-inflammatory and antioxidant properties, has long been purported to be of therapeutic benefit to atherosclerosis patients. However, large clinical trials have yielded inconsistent data, likely due to variations in the formulation, dosage, and bioavailability of DHA following oral intake. To fully exploit its potential therapeutic effects, we have developed an injectable liposomal DHA formulation intended for intravenous administration as a plaque-targeted nanomedicine. The liposomal formulation protects DHA against chemical degradation and increases its local concentration within atherosclerotic lesions. Mechanistically, DHA liposomes are readily phagocytosed by activated macrophages, exert potent anti-inflammatory and antioxidant effects, and inhibit foam cell formation. Upon intravenous administration, DHA liposomes accumulate preferentially in atherosclerotic lesional macrophages and promote polarization of macrophages towards an anti-inflammatory M2 phenotype, resulting in attenuation of atherosclerosis progression in both ApoE−/− and Ldlr−/− experimental models. Plaque composition analysis demonstrates that liposomal DHA inhibits macrophage infiltration, reduces lipid deposition, and increases collagen content, thus improving the stability of atherosclerotic plaques against rupture. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) further reveals that DHA liposomes can partly restore the complex lipid profile of the plaques to that of early-stage plaques. In conclusion, DHA liposomes offer a promising approach for applying DHA to stabilize atherosclerotic plaques and attenuate atherosclerosis progression, thereby preventing atherosclerosis-related cardiovascular events

Cytotoxicity of SRJ23 and its derivatives, expression and SRJ23 binding of KRas G12V oncoprotein

Oncogenic KRas signaling is often associated with a poor prognosis of pancreatic cancer. Effort to target oncogenic KRas signaling persists for years but without much success due to its „undruggable‟ property. In recent years, several small-molecule KRas inhibitors such as SRJ23 were developed to inhibit oncogenic KRas signaling at the guanine nucleotide exchange level. MTT cell viability assay was used to evaluate the cytotoxicity of SRJ23 and its derivatives towards breast, colon, prostate and pancreatic cancer cell lines. SRJ23 is a semi-synthetic derivative of andrographolide (AGP) which lacks a distinct selectivity towards specific cancer type by demonstrating an equally good cytotoxicity in breast, colon, prostate, and pancreatic cancer cell lines. A few novel derivatives of SRJ23 were synthesised to improve its target specificity. One of the derivatives (SRS 151) shows selective total growth inhibition on pancreatic cancer cells harbouring oncogenic KRas (MIA PaCa-2 and Capan-2). SRS157 (GI50 = 2.4 μM), although is as equally potent as SRJ23 (GI50 = 2.1 μM) in pancreatic cancer cell lines, was found selectively targeting pancreatic cancer. Previous study has revealed a direct binding of SRJ23 to KRas in silico. To validate a physical interaction between oncogenic KRas G12V and SRJ23 in vitro, KRas G12V was expressed by using Champion pET SUMO protein expression system and was used for X-ray crystallography to study the physical interaction between KRas G12V and SRJ23. The hanging drop vapour diffusion method in X-ray crystallography did not yield diffractable protein crystals, therefore saturation transfer difference-nuclear magnetic resonance (STD-NMR) was applied to study KRas G12V-SRJ23 interaction. The STD-NMR suggested a potential physical interaction between KRas G12V and SRJ23 that involves mainly the three-membered ring and the hydroxyl group on the lactone ring of SRJ23. In conclusion, the findings of this study showed that SRJ23 could be a promising anti-Ras drug

Tissue factor cytoplasmic domain exacerbates post-infarct left ventricular remodeling via orchestrating cardiac inflammation and angiogenesis

10.7150/thno.63354Theranostics11199243-926

Injectable liposomal docosahexaenoic acid alleviates atherosclerosis progression and enhances plaque stability

Atherosclerosis is a chronic inflammatory vascular disease that is characterized by the accumulation of lipids and immune cells in plaques built up inside artery walls. Docosahexaenoic acid (DHA, 22:6n-3), an omega-3 polyunsaturated fatty acid (PUFA), which exerts anti-inflammatory and antioxidant properties, has long been purported to be of therapeutic benefit to atherosclerosis patients. However, large clinical trials have yielded inconsistent data, likely due to variations in the formulation, dosage, and bioavailability of DHA following oral intake. To fully exploit its potential therapeutic effects, we have developed an injectable liposomal DHA formulation intended for intravenous administration as a plaque-targeted nanomedicine. The liposomal formulation protects DHA against chemical degradation and increases its local concentration within atherosclerotic lesions. Mechanistically, DHA liposomes are readily phagocytosed by activated macrophages, exert potent anti-inflammatory and antioxidant effects, and inhibit foam cell formation. Upon intravenous administration, DHA liposomes accumulate preferentially in atherosclerotic lesional macrophages and promote polarization of macrophages towards an anti-inflammatory M2 phenotype, resulting in attenuation of atherosclerosis progression in both ApoE−/− and Ldlr−/− experimental models. Plaque composition analysis demonstrates that liposomal DHA inhibits macrophage infiltration, reduces lipid deposition, and increases collagen content, thus improving the stability of atherosclerotic plaques against rupture. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) further reveals that DHA liposomes can partly restore the complex lipid profile of the plaques to that of early-stage plaques. In conclusion, DHA liposomes offer a promising approach for applying DHA to stabilize atherosclerotic plaques and attenuate atherosclerosis progression, thereby preventing atherosclerosis-related cardiovascular events.</p