Role of a novel benzoxazine derivative in the chemosensitization of colon cancer

Cycloaddition of 4-Acyl-1H-pyrrole-2,3-diones Fused at [e]-Side and Cyanamides: Divergent Approach to 4H-1,3-Oxazines

4-Acyl-1H-pyrrole-2,3-diones fused at [e]-side with a heterocyclic moiety are suitable platforms for the development of a hetero-Diels–Alder-reaction-based, diversity-oriented approaches to series of skeletally diverse heterocycles. These platforms are known to react as oxa-dienes with dienophiles to form angular 6/6/5/6-tetracyclic alkaloid-like heterocycles and are also prone to decarbonylation at high temperatures resulting in generation of acyl(imidoyl)ketenes, bidentate aza- and oxa-dienes, which can react with dienophiles to form skeletally diverse products (angular tricyclic products or heterocyclic ensembles). Based on these features, we have developed an approach to two series of skeletally diverse 4H-1,3-oxazines (tetracyclic alkaloid-like 4H-1,3-oxazines and 5-heteryl-4H-1,3-oxazines) via a hetero-Diels–Alder reaction of 4-acyl-1H-pyrrole-2,3-diones fused at [e]-side with cyanamides. The products of these transformations are of interest for drug discovery, since compounds bearing 4H-1,3-oxazine moiety are extensively studied for inhibitory activities against anticancer targets.

Discovery of sertraline and its derivatives able to combat drug-resistant gastric cancer cell via inducing apoptosis

Resistance phenomena during chemotherapy of tumor has been severely hampering the applications of chemotherapeutics. Due to advantage of drug repurposing, discovery of new chemosensitizers based on approved drugs is an effect strategy to find new candidates. Herein, we found antidepressant drug - sertraline, could sensitize drug-resistant gastric cancer cell (SGC-7901/DDP) with the IC₅₀ value of 18.73 μM. To understand the structure-activity relationship and improve the activity, 30 derivatives were synthesized and evaluated. The IC₅₀ value of the best compound was improved to 5.2 μM. Moreover, we found apoptosis induction and cell cycle arrest was the reason for the cell death of the drug-resistant cells after treatment of sertraline and derivatives, and PI3K/Akt/mTOR pathway was involved.

Benzoxazine Formation Mechanism Evaluation by Direct Observation of Reaction Intermediates

Benzoxazine formation is a fundamental step in the preparation of polybenzoxazine resins, and a detailed description of the mechanism governing the formation of benzoxazine and side products is vital for improving the properties and performance of these resins. Determination of the nature and properties of reaction intermediates is not trivial. Therefore, a Mannich-type condensation of aniline, formaldehyde, and phenol was evaluated as a potential method to form benzoxazine. Coupling positive mode electrospray ionization mass spectrometry (ESI(+)-MS) with infrared multiple photon dissociation (IRMPD) spectroscopy allowed unambiguous determination of an iminium-based mechanism and the direct observation of iminium intermediates. The benzoxazine formation mechanism was indirectly confirmed by the observation of side products that are relevant to the polymerization step, and directly confirmed by the identification of four distinct reaction intermediates that were completely characterized by IRMPD spectroscopy. The benzoxazine monomer was also shown to undergo isomerization under standard ESI-MS analysis conditions, suggesting the presence of a mixture of three isomers during their usual ESI-MS analysis.

Inhibition of AKT signalling by benzoxazine derivative LTUR6 through the modulation of downstream kinases

Many compounds structurally similar to chromones have been developed to enhance the sensitizing effect of cancer cells to chemotherapeutic agents. Most of these compounds have been shown to promote this sensitization by targeting the repair pathways. One such compound is LTUR6, which enhances the sensitization of doxorubicin to colon cancer cells HT29, by inhibiting the phosphorylation of the double stranded break (DSB) repair enzyme AKT. The downstream regulatory targets of AKT that enhance doxorubicin mediated cytotoxicity in the presence of LTUR6 remains elusive. In this study, we performed comparative analyses of 43 kinase phosphorylation sites using the human phospho-kinase array proteome profiler. Results revealed altered expression levels of multiple proteins that regulated apoptotic signalling pathways. Increased activation of mTOR, RSK1/2/3, p38α and PRAS40 after combination treatment with LTUR6 and doxorubicin over doxorubicin alone was observed. This study provides a deeper insight into the key proteins involved and presents a novel molecular pathway.

Antitumour, Immunomodulatory activity and in silico studies of naphthopyranones targeting iNOS, a relevant target for the treatment of Helicobacter pylori infection

The naphthopyranones paepalantine and 5-methoxy-3,4-dehydroxanthomegnin isolated from Paepalanthus sp, showed in previous studies antioxidant, anti-inflammatory, antitumour and antimicrobial potential, such as anti-Helicobacter pylori activity. H. pylori infection is one of the main causes of gastric cancer, causing an excessive inflammatory response through the neutrophils and macrophages infiltration, increasing the release of reactive species and thus inducing the production of pro-inflammatory mediators. In the present study, immunomodulatory activity of naphthopyranones in LPS-stimulated macrophages and cytotoxic action in gastric adenocarcinoma cell lines was evaluated. The potential of interaction of these substances in the iNOS binding site was investigated by molecular docking. Cytotoxic activity in gastric adenocarcinoma cells (AGS) was evaluated by the MTT assay. The results evidenced immunomodulatory potential by inhibiting the pro-inflammatory cytokines and nitric oxide produced by LPS-stimulated macrophages. Cytotoxic activity in AGS cell line was also reported. The results indicated that the studied naphthopyranones are viable alternatives in the treatment and prevention of H. pylori infection as well as the diseases related to this infection, especially gastric cancer.

Doxorubicin resistance induces IL6 activation in the colon cancer cell line LS180

Despite improvements in the development of drugs for the treatment of cancer, drug resistance remains a major obstacle. In colon cancer, following an initially promising response, patients develop drug resistance, which impacts the efficacy and halts the response of cancerous cells towards drugs. In the present study, a phosphatase and tensin homolog (PTEN) knockdown model of LS180 cells, doxorubicin-resistant models of LS180 cells as well as doxorubicin-resistant LS180 (PTEN) knockdown model were established. The present study demonstrated that doxorubicin resistance led to the activation of interleukin (IL)6 signalling pathway which was enhanced by knockdown of PTEN. There was also an increase in the levels of IL8 and IL2 which were further enchanced by knockdown of PTEN. Doxorubicin resistance also led to an increase in the population of cancer stem cells in LS180 and shPTEN-treated LS180 cells. Notably, doxorubicin resistance also induced epithelial to mesenchymal transition and increased the formation of mammospheres. Furthermore, the present study also reported that IL6 receptor antibody not only decreased IL6 levels but also led to a significant decreased number of cancer stem cell like population and mammosphere formation. In conclusion, in the present study it was demonstrated that doxorubicin resistance led to activation of IL6 signalling pathway which was further elevated by the knockdown of PTEN in the colon cancer cell line LS180. Thus, inhibiting the IL6 loop may provide an alternative pathway to tackle doxorubicin resistance.