Leukotriene A4 hydrolase: an emerging target of natural products for cancer chemoprevention and chemotherapy

Pathological and pharmacological functions of the metabolites of polyunsaturated fatty acids mediated by cyclooxygenases, lipoxygenases, and cytochrome P450s in cancers

Oxylipins have garnered increasing attention because they were consistently shown to play pathological and/or pharmacological roles in the development of multiple cancers. Oxylipins are the metabolites of polyunsaturated fatty acids via both enzymatic and nonenzymatic pathways. The enzymes mediating the metabolism of PUFAs include but not limited to lipoxygenases (LOXs), cyclooxygenases (COXs), and cytochrome P450s (CYPs) pathways, as well as the down-stream enzymes. Here, we systematically summarized the pleiotropic effects of oxylipins in different cancers through pathological and pharmacological aspects, with specific reference to the enzyme-mediated oxylipins. We discussed the specific roles of oxylipins on cancer onset, growth, invasion, and metastasis, as well as the expression changes in the associated metabolic enzymes and the associated underlying mechanisms. In addition, we also discussed the clinical application and potential of oxylipins and related metabolic enzymes as the targets for cancer prevention and treatment. We found the specific function of most oxylipins in cancers, especially the underlying mechanisms and clinic applications, deserves and needs further investigation. We believe that research on oxylipins will provide not only more therapeutic targets for various cancers but also dietary guidance for both cancer patients and healthy humans.

Patent highlights October-November 2022

A snapshot of recent noteworthy developments in the patent literature of relevance to pharmaceutical and medical research and development.

Isolation of lymph shows dysregulation of STAT3 and CREB pathways in the spleen and liver during leukemia development in a rat model

BACKGROUND AND AIMS

Acute myeloid leukemia (AML) is a heterogeneous malignant condition characterized by massive infiltration of poorly differentiated white blood cells in the blood stream, bone marrow, and extramedullary sites. During leukemic development, hepatosplenomegaly is expected to occur because large blood volumes are continuously filtered through these organs. We asked whether infiltration of leukemic blasts initiated a response that could be detected in the interstitial fluid phase of the spleen and liver.

MATERIAL AND METHODS

We used a rat model known to mimic human AML in growth characteristics and behavior. By cannulating efferent lymphatic vessels from the spleen and liver, we were able to monitor the response of the microenvironment during AML development.

RESULTS AND DISCUSSION

Flow cytometric analysis of lymphocytes showed increased STAT3 and CREB signaling in spleen and depressed signaling in liver, and proteins related to these pathways were identified with a different profile in lymph and plasma in AML compared with control. Additionally, several proteins were differently regulated in the microenvironment of spleen and liver in AML when compared with control.

CONCLUSION

Interstitial fluid, and its surrogate efferent lymph, can be used to provide unique information about responses in AML-infiltered organs and substances released to the general circulation during leukemia development.

An enzyme activated fluorescent probe for LTA4H activity sensing and its application in cancer screening

Early diagnosis of cancer is an efficient strategy to prevent tumor progression and improve the survival rate of patients. However, to discovery of reliable tumor-specific biomarkers remains a great challenge. Leukotriene A4 hydrolase (LTA₄H) is a bifunctional zinc metalloenzyme with epoxide hydrolase activity and aminopeptidase activity, which plays important roles in allergic and inflammatory reactions and showed strong relevance with carcinoma progression. We thus sought to investigate the possibility of application LTA₄H activity detection in cancer diagnosis. To achieve this, we herein develop an enzyme activated fluorescent probe for LTA₄H activity sensing by incorporating the specific recognition unit of LTA₄H with a red-emitting fluorophore. The acquired probe (named as ADMAB) showed high sensitivity and specificity toward LTA₄H in vitro. By further application of ADMAB in living cells, significantly elevated LTA₄H activity in cancer cell lines was observed when compared with normal cell lines and in vivo tracing A549 tumor in nude mice was also realized by ADMAB. Meanwhile, the wound-healing assay further revealed the importance of LTA₄H in tumor metastasis. Moreover, the LTA₄H activity in human serum sample was successfully detected by ADMAB and significantly elevated LTA₄H activity in patients diagnosed with cancer was firstly found, which demonstrated ADMAB to be a useful tool for cancer diagnosis and LTA₄H related biological study.

LTA4H extensively associates with mRNAs and lncRNAs indicative of its novel regulatory targets

The RNA-binding metabolic enzyme LTA4H is a novel target for cancer chemoprevention and chemotherapy. Recent research shows that the increased expression of LTA4H in laryngeal squamous cell carcinoma (LSCC) promotes tumor proliferation, migration, and metastasis. However, its mechanism remains unclear. To investigate the potential role of LTA4H in LSCC, we employed the improved RNA immunoprecipitation and sequencing (iRIP-Seq) experiment to get the expression profile of LTA4H binding RNA in HeLa model cells, a cancer model cell that is frequently used in molecular mechanism research. We found that LTA4H extensively binds with mRNAs/pre-mRNAs and lncRNAs. In the LTA4H binding peak, the frequency of the AAGG motif reported to interact with TRA2β4 was high in both replicates. More notably, LTA4H-binding genes were significantly enriched in the mitotic cell cycle, DNA repair, RNA splicing-related pathways, and RNA metabolism pathways, which means that LTA4H has tumor-related alternative splicing regulatory functions. QRT-PCR validation confirmed that LTA4H specifically binds to mRNAs of carcinogenesis-associated genes, including LTBP3, ROR2, EGFR, HSP90B1, and lncRNAs represented by NEAT1. These results suggest that LTA4H may combine with genes associated with LSCC as an RNA-binding protein to perform a cancer regulatory function. Our study further sheds light on the molecular mechanism of LTA4H as a clinical therapy target for LSCC.

RNAseq analysis of treatment-dependent signaling changes during inflammation in a mouse cutaneous wound healing model

BACKGROUND

Despite proven therapeutic effects in inflammatory conditions, the specific mechanisms of phytochemical therapies are not well understood. The transcriptome effects of Traumeel (Tr14), a multicomponent natural product, and diclofenac, a non-selective cyclooxygenase (COX) inhibitor, were compared in a mouse cutaneous wound healing model to identify both known and novel pathways for the anti-inflammatory effect of plant-derived natural products.

METHODS

Skin samples from abraded mice were analyzed by single-molecule, amplification-free RNAseq transcript profiling at 7 points between 12 and 192 h after injury. Immediately after injury, the wounds were treated with either diclofenac, Tr14, or placebo control (n = 7 per group/time). RNAseq levels were compared between treatment and control at each time point using a systems biology approach.

RESULTS

At early time points (12-36 h), both control and Tr14-treated wounds showed marked increase in the inducible COX2 enzyme mRNA, while diclofenac-treated wounds did not. Tr14, in contrast, modulated lipoxygenase transcripts, especially ALOX12/15, and phospholipases involved in arachidonate metabolism. Notably, Tr14 modulated a group of cell-type specific markers, including the T cell receptor, that could be explained by an overarching effect on the type of cells that were recruited into the wound tissue.

CONCLUSIONS

Tr14 and diclofenac had very different effects on the COX/LOX synthetic pathway after cutaneous wounding. Tr14 allowed normal autoinduction of COX2 mRNA, but suppressed mRNA levels for key enzymes in the leukotriene synthetic pathway. Tr14 appeared to have a broad 'phytocellular' effect on the wound transcriptome by altering the balance of cell types present in the wound.

DNA polymerase β deficiency promotes the occurrence of esophageal precancerous lesions in mice

Esophageal mucosa undergoes mild, moderate, severe dysplasia, and other precancerous lesions and eventually develops into carcinoma in situ, and understanding the developmental progress of esophageal precancerous lesions is beneficial to prevent them from developing into cancer. DNA polymerase β (Polβ), a crucial enzyme of the base excision repair system, plays an important role in repairing damaged DNA and maintaining genomic stability. Abnormal expression or deletion mutation of Polβ is related to the occurrence of esophageal cancer, but the role of Polβ deficiency in the esophageal precancerous lesions is still unclear. Here, esophageal mucosa Polβ-knockout mice were used to explore the relationship of Polβ deficiency with esophageal precancerous lesions. First, we found the degree and number of esophageal precancerous lesions in Polβ-KO mice were more serious than those in Polβ-Loxp mice after N-nitrosomethylbenzylamine (NMBA) treatment. Whole exome sequencing revealed that deletion of Polβ increased the frequency of gene mutations. Gene expression prolife analysis showed that the expression of proteins correlated to cell proliferation and the cell cycle was elevated in Polβ-KO mice. We also found that deletion of Polβ promoted the proliferation and clone formation as well as accelerated cell cycle progression of human immortalized esophageal epithelial cell line SHEE treated with NMBA. Our findings indicate that Polβ knockout promotes the occurrence of esophageal precancerous lesions.

Identification of key lipid metabolites during metabolic dysregulation in the diabetic retinopathy disease mouse model and efficacy of Keluoxin capsule using an UHPLC-MS-based non-targeted lipidomics approach

Diabetic retinopathy (DR) is an important complication of diabetes, and is currently the main cause of blindness among young adults in the world. Previous studies have shown that Keluoxin (KLX) capsules have a significant effect on DR in C57BL/KsJ/db-/- mice (db/db mice), however the unclear mechanism limits its further clinical application and actual value. Further research is urgently needed for the treatment of DR disease. Discovery of key lipid biomarkers and metabolic pathways can reveal and explore the molecular mechanisms related to DR development and discover the effect of Keluoxin (KLX) capsule against DR in db/db mice. Lipidomics has been used for characterizing the pathological conditions via identification of key lipid metabolites and the metabolic pathway. In this study, the high-throughput lipidomics using UHPLC-Q-TOF/MS combined with multivariate statistical analysis, querying multiple network databases and employing ingenuity pathway analysis (IPA) method for molecular target prediction. A total of 30 lipid biomarkers were identified and 7 metabolic pathways including arachidonic acid metabolism and steroid hormone biosynthesis were found. The preventive effect of KLX intervention can regulate 22 biomarkers such as LysoPA(16:0/0:0), prostaglandin D2, cortisol and γ-linolenic acid, etc. IPA platform has predicted that PI3K/MAPK pathway are closely related to DR development. It also showed that high-throughput lipidomics combined with multivariate statistical analysis could deep excavate of the biological significance of the big data, and can provide molecular targets information about the disease treatment.

Okra (Abelmoschus Esculentus) as a Potential Dietary Medicine with Nutraceutical Importance for Sustainable Health Applications

Recently, there has been a paradigm shift from conventional therapies to relatively safer phytotherapies. This divergence is crucial for the management of various chronic diseases. Okra (Abelmoschus esculentus L.) is a popular vegetable crop with good nutritional significance, along with certain therapeutic values, which makes it a potential candidate in the use of a variety of nutraceuticals. Different parts of the okra fruit (mucilage, seed, and pods) contain certain important bioactive components, which confer its medicinal properties. The phytochemicals of okra have been studied for their potential therapeutic activities on various chronic diseases, such as type-2 diabetes, cardiovascular, and digestive diseases, as well as the antifatigue effect, liver detoxification, antibacterial, and chemo-preventive activities. Moreover, okra mucilage has been widely used in medicinal applications such as a plasma replacement or blood volume expanders. Overall, okra is considered to be an easily available, low-cost vegetable crop with various nutritional values and potential health benefits. Despite several reports about its therapeutic benefits and potential nutraceutical significance, there is a dearth of research on the pharmacokinetics and bioavailability of okra, which has hampered its widespread use in the nutraceutical industry. This review summarizes the available literature on the bioactive composition of okra and its potential nutraceutical significance. It will also provide a platform for further research on the pharmacokinetics and bioavailability of okra for its possible commercial production as a therapeutic agent against various chronic diseases.

Indian Morinda species: A review

Morinda is a largest genus of Rubiaceae family, and its 11 species are found in India. In India, plant species are known by several common names as great morinda, Indian mulberry, noni, beach mulberry and cheese fruit. Various Morinda products (capsules, tablets, skin products and fruit juices) are available in the market, used by people for treatment of several health complaints. A diversity of phytochemicals including iridoids, flavonoids, flavonoid glycosides, anthraquinones, coumarins, lignanas, noniosides, phenolics and triterpenoids have been reported from Morinda species. Morinda species are used in the treatment of inflammation, cancer, diabetes, psyquiatric disorders, and bacterial and viral infections. The noni fruit juice (Morinda citrifolia) and its products are used clinically in the treatment of cancer, hypertension and cervical spondylosis affecting patients. M. citrifolia fuit juice, with different doses, is used in the maintaining blood pressure and reducing of superoxides, HDL and LDL levels. Similarly, oligosaccharide capsules and tablets of root extract of M. officinalis are recommended as medicine for the treatment of kidney problems and sexual dysfunctions of patients. The toxicological studies revealed that higher doses of fruit juice (4,000 or 5,000 mg/kg) of M. citrifolia for 2 or more months cause toxic effects on liver and kidneys. M. officinalis root extracts (ethanolic and aqueous) are found fully safe during treatment of diseases. A large number of reviews are available on M. citrifolia but very few studies are conducted on other Indian Morinda species. This review reports the comprehensive knowledge on state-wise distribution, botany, ethnomedicinal uses, phytochemistry, pharmacological activities, clinical applications and toxicological evaluations of 11 species of Morinda found in India.

Ornithine decarboxylase inhibition downregulates multiple pathways involved in the formation of precancerous lesions of esophageal squamous cell cancer

The high incidence and mortality of esophageal squamous cell cancer (ESCC) is a major health problem worldwide. Precancerous lesions of ESCC may either progress to cancer or revert to normal epithelium with appropriate interventions; the bidirectional instability of the precancerous lesions of ESCC provides opportunities for intervention. Reports suggest that the upregulation of ornithine decarboxylase (ODC) is closely related to carcinogenesis. In this study, we investigated whether ODC may act as a target for chemoprevention in ESCC. Immunohistochemistry (IHC) assays indicate that ODC expression is higher in esophageal precancerous lesions compared with normal tissue controls. Its overexpression promotes cell proliferation and transformation of normal esophageal epithelial cells, and its activity is increased after N-nitrosomethylbenzylamine (NMBA) induction in Shantou human embryonic esophageal cell line (SHEE) and human immortalized cells (Het1A) cells. In addition, p38 α, extracellular regulated kinase (ERK1/2) in the mitogen-activated protein kinase pathway and protein kinase B (AKT)/mammalian target of rapamycin (mTOR)/ribosomal protein S6 kinase (p70S6K) pathways are activated in response to NMBA treatment. Difluoromethylornithine (DFMO) is an ODC inhibitor, which inhibits NMBA-induced activation of p38 α, ERK1/2 and AKT/mTOR/p70S6K pathways; this has been verified by Western blotting. DFMO was also found to suppress the development of esophageal precancerous lesions in an NMBA-induced rat model; IHC demonstrated p38 α, ERK1/2, and AKT/mTOR/p70S6K pathways to be downregulated in these rats. These findings indicate the mechanisms by which ODC inhibition suppresses the development of esophageal precancerous lesions by downregulating p38 α, ERK1/2, and AKT/mTOR/p70S6k signaling pathways, ODC may be a potential target for chemoprevention in ESCC.

Mass Spectrometric Analysis Identifies AIMP1 and LTA4H as FSCN1-Binding Proteins in Laryngeal Squamous Cell Carcinoma

Dysregulation of fascin actin-bundling protein 1 (FSCN1) enhances cell proliferation, invasion, and motility in laryngeal squamous cell carcinoma (LSCC), while the mechanism remains unclear. Here, co-immunoprecipitation and mass spectrometry is utilized to identify potential FSCN1-binding proteins. Functional annotation of FSCN1-binding proteins are performed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Furthermore, the protein-protein interaction network of FSNC1-binding proteins is constructed and the interactions between FSCN1 and novel identified interacting proteins AIMP1 and LTA4H are validated. Moreover, the expression and functional role of AIMP1 and LTA4H in LSCC are investigated. A total of 123 proteins are identified as potential FSCN1-binding proteins, and functional annotation shows that FSCN1-binding proteins are significantly enriched in carcinogenic processes, such as filopodium assembly-regulation and GTPase activity. Co-IP/western blotting and immunofluorescence confirm that AIMP1 and LTA4H bind and colocalize with FSCN1. Furthermore, both AIMP1 and LTA4H are upregulated in LSCC tissues, and knockdown of AIMP1 or LTA4H inhibits LSCC cell proliferation, migration, and invasion. Collectively, the identification of FSCN1-binding partners enhances understanding of the mechanism of FSCN1-mediated malignant phenotypes, and these findings indicate that FSCN1 binds to AIMP1 and LTA4H might promote the progression of LSCC.

Inhibition of LTA4H by bestatin in human and mouse colorectal cancer

Background

Our preclinical data showed that the leukotriene A4 hydrolase (LTA4H) pathway plays a role in colorectal cancer (CRC). High expression of LTA4H and leukotriene B4 receptor type 1 (BLT1) were also associated with CRC survival probability. Clinical samples were evaluated to determine whether LTA4H could serve as a therapeutic target and whether leukotriene B4 (LTB4) could be used as a biomarker for evaluating the efficacy of bestatin in CRC.

Methods

Patients with Stage I-III CRC did or did not receive bestatin prior to surgery. Evaluable pairwise CRC patient blood samples were collected to evaluate LTB4 concentration. Tissues were processed by immunohistochemistry to detect the LTA4H pathway and Ki-67 expression. We also determined whether LTA4H or BLT1 was associated with CRC survival probability and explored the mechanism of bestatin action in CRC.

Findings

Samples from 13 CRC patients showed a significant decrease in LTB4, the LTA4H signaling pathway, and Ki-67 in the bestatin-treated group compared with the untreated group. LTA4H and BLT1 are overexpressed in CRC and associated with CRC survival probability. Bestatin effectively inhibited LTB4 and tumorigenesis in the Apc^Min/+ and CRC patient-derived xenograft mouse model.

Interpretation

These results demonstrate that LTB4 could serve as a biomarker for evaluating bestatin efficacy in CRC and the antitumor effects of bestatin through its targeting of LTA4H and support further studies focusing on LTA4H inhibition in CRC.

Hypoxia-induced tumor exosomes promote M2-like macrophage polarization of infiltrating myeloid cells and microRNA-mediated metabolic shift

Developing tumors rapidly outgrow their oxygen supply and are subject to hypoxia, which stimulates hypersecretion of tumor-derived exosomes that promote angiogenesis, metastasis, and immunosuppression, but the molecular mediators of these pathological effects remain poorly defined. Using quantitative proteomics, we identified that exosomes produced by hypoxic tumor cells are highly enriched in immunomodulatory proteins and chemokines including CSF-1, CCL2, FTH, FTL, and TGFβ. Modeling exosome effects on tumor-infiltrating immune cells, we observed a potent ability of these hypoxia-induced vesicles to influence macrophage recruitment and promote M2-like polarization both in vitro and in vivo. In addition, hypoxic, but not normoxic, tumor exosomes enhanced oxidative phosphorylation in bone marrow-derived macrophages via transfer of let-7a miRNA, resulting in suppression of the insulin-Akt-mTOR signaling pathway. Together, these data demonstrate that hypoxia promotes tumor secretion of biomolecule-loaded exosomes that can modify the immunometabolic profile of infiltrating monocyte-macrophages to better evade host immunity and enhance tumor progression.