cAMP-PKA/EPAC signaling and cancer: the interplay in tumor microenvironment

Cancer is a complex disease resulting from abnormal cell growth that is induced by a number of genetic and environmental factors. The tumor microenvironment (TME), which involves extracellular matrix, cancer-associated fibroblasts (CAF), tumor-infiltrating immune cells and angiogenesis, plays a critical role in tumor progression. Cyclic adenosine monophosphate (cAMP) is a second messenger that has pleiotropic effects on the TME. The downstream effectors of cAMP include cAMP-dependent protein kinase (PKA), exchange protein activated by cAMP (EPAC) and ion channels. While cAMP can activate PKA or EPAC and promote cancer cell growth, it can also inhibit cell proliferation and survival in context- and cancer type-dependent manner. Tumor-associated stromal cells, such as CAF and immune cells, can release cytokines and growth factors that either stimulate or inhibit cAMP production within the TME. Recent studies have shown that targeting cAMP signaling in the TME has therapeutic benefits in cancer. Small-molecule agents that inhibit adenylate cyclase and PKA have been shown to inhibit tumor growth. In addition, cAMP-elevating agents, such as forskolin, can not only induce cancer cell death, but also directly inhibit cell proliferation in some cancer types. In this review, we summarize current understanding of cAMP signaling in cancer biology and immunology and discuss the basis for its context-dependent dual role in oncogenesis. Understanding the precise mechanisms by which cAMP and the TME interact in cancer will be critical for the development of effective therapies. Future studies aimed at investigating the cAMP-cancer axis and its regulation in the TME may provide new insights into the underlying mechanisms of tumorigenesis and lead to the development of novel therapeutic strategies.

Current progress of pig models for liver cancer research

Preclinical trials play critical roles in assessing the safety and efficiency of novel therapeutic strategies for human diseases including live cancer. However, most therapeutic strategies that were proved to be effective in preclinical cancer models failed in human clinical trials due to the lack of appropriate disease animal models. Therefore, it is of importance and urgent to develop a precise animal model for preclinical cancer research. Liver cancer is one of the most frequently diagnosed cancers with low 5-year survival rate. Recently, porcine attracted increasing attentions as animal model in biomedical research. Porcine liver cancer model may provide a promising platform for biomedical research due to their similarities to human being in body size, anatomical characteristics, physiology and pathophysiology. In this review, we comprehensively summarized and discussed the advantages and disadvantages, rationale, current status and progress of pig models for liver cancer research.

Daphnetin attenuates intestinal inflammation, oxidative stress, and apoptosis in ulcerative colitis via inhibiting REG3A-dependent JAK2/STAT3 signaling pathway

Daphnetin is a natural coumarin compound with anti-inflammatory, anti-oxidant, and anti-apoptotic effects, which has been previously demonstrated to ameliorate DSS-induced ulcerative colitis (UC). However, the molecular mechanism involved in the daphnetin-mediated pathological process of UC remains unclarified. The current study used DSS-induced mice and LPS-challenged Caco-2 cells as UC models. Bodyweight, disease activity index (DAI) score, and colon length were used to evaluate the severity of colitis. The histological changes in colon tissues were observed using H&E and PAS staining. Protein levels were detected by western blot. The malondialdehyde (MDA) and superoxide dismutase (SOD) activities were used to assess oxidative stress. Inflammatory responses were evaluated by detecting the levels of inflammatory cytokines (IFN-r, IL-1β, IL-6, and TNF-α) using flow cytometry. CCK-8 and TUNEL assay were employed to determine cell growth and cell death, respectively. The results showed that daphnetin could ameliorate the severity of colitis and attenuate the damage to intestinal structure in DSS-induced mice. Compared with the DSS group, the expression of ZO-1, occludin, and anti-apoptotic protein (BCL-2) was increased while the level of pro-apoptotic proteins (Bax and cleaved caspase 3) was decreased in DSS + daphnetin group. The activity of MDA and SOD, as well as the levels of inflammatory cytokines were substantially suppressed by daphnetin. In consistency, in vitro assays indicated that daphnetin protected Caco-2 cells from LPS-stimulated viability impairment, apoptosis, oxidative stress, and inflammation. Furthermore, daphnetin suppressed the activity of JAK2/STAT signaling in LPS-induced Caco-2 cells in a REG3A-dependent manner. REG3A overexpression abated the ameliorative effects of daphnetin while JAK2/STAT signaling inhibition functioned synergically with daphnetin in LPS-stimulated Caco-2 cells. Collectively, this study deepened the understanding of the therapeutic effects of daphnetin on UC and uncovered for the first time that daphnetin functioned through REG3A-activated JAK2/STAT3 signaling in UC, which may provide novel insights for the treatment of UC.

Daphnetin, a Coumarin with Anticancer Potential against Human Melanoma: In Vitro Study of Its Effective Combination with Selected Cytostatic Drugs

(1) The treatment of metastatic or drug-resistant melanoma is still a significant therapeutic problem. The aim of this study was to evaluate the anticancer potential of daphnetin (7,8-dihydroxycoumarin) and its combinations with five different cytostatic drugs (mitoxantrone, docetaxel, vemurafenib, epirubicin and cisplatin). (2) The viability, proliferation and cytotoxicity of daphnetin against four human malignant melanoma cell lines were evaluated. The interactions were assessed using isobolographic analysis for the combinations of daphnetin with each of the five cytostatic drugs. (3) Daphnetin showed anticancer activity against malignant melanoma, with IC₅₀ values ranging from 40.48 ± 10.90 µM to 183.97 ± 18.82 µM, depending on the cell line. The combination of daphnetin with either vemurafenib or epirubicin showed an antagonistic interaction. Moreover, additive interactions were observed for the combinations of daphnetin with cisplatin and docetaxel. The most desirable synergistic interactions for human melanoma metastatic cell lines were observed for the combination of daphnetin with mitoxantrone. (4) The obtained results suggest that daphnetin should not be combined with vemurafenib or epirubicin in the treatment of malignant melanoma due to the abolition of their anticancer effects. The combination of daphnetin with mitoxantrone is beneficial in the treatment of metastatic melanoma due to their synergistic interaction.

The anticarcinogenic effect of eugenol on lung cancer induced by diethylnitrosamine/2-acetylaminofluorene in Wistar rats: insight on the mechanisms of action

This study was designed to assess the ameliorative effects of eugenol and to propose the possible mechanisms of action of eugenol in diethylnitrosamine (DENA)/acetylaminofluorene (AAF)-caused lung cancer in Wistar rats. To induce lung cancer, DENA at a dose of 150 mg/kg body weight (b.wt) for 2 weeks were intraperitoneally injected once each week and AAF was administered orally at a dose of 20 mg/kg b.wt. four times each week for the next 3 weeks. DENA/AAF-administered rats were orally supplemented with eugenol at a dose of 20 mg/kg b.wt administered once a day until 17 weeks starting from the 1st week of DENA administration. Lung histological lesions, including sheets of tumor cells, micropapillary adenocarcinoma, and apoptotic cells, resulting from the DENA/AAF dosage, were ameliorated by eugenol treatment. However, a significant drop in the levels of LPO in the lungs and a remarkable rise in GSH content and GPx and SOD activities were observed in DENA/AAF-administered rats treated with eugenol compared with those in DENA/AAF-administered controls. Moreover, in DENA/AAF-administered rats, eugenol supplementation significantly reduced TNF-α and IL-1β levels and mRNA expression levels of NF-κB, NF-κB p65, and MCP-1 but significantly elevated the level of Nrf2. Furthermore, the DENA/AAF-administered rats treated with eugenol exhibited a significant downregulation of Bcl-2 expression levels in addition to a significant upregulation in P53 and Bax expression levels. Otherwise, the administration of DENA/AAF elevated the protein expression level of Ki-67, and this elevation was reversed by eugenol treatment. In conclusion, eugenol has effective antioxidant, anti-inflammatory, proapoptotic, and antiproliferative properties against lung cancer.

Daphnetin: A bioactive natural coumarin with diverse therapeutic potentials

Daphnetin (DAP), a coumarin derivative extracted from Daphne species, is biologically active phytochemical with copious bioactivities including anti-inflammatory, anti-oxidant, neuroprotective, analgesic, anti-pyretic, anti-malarial, anti-bacterial, anti-arthritic, neuroprotective, hepatoprotective, nephroprotective, and anti-cancer activities. A wide range of studies have been conducted exploring the significance and therapeutic potential of DAP. This study reviewed various databases such as NCBI, PubMed, Web of Science, Scopus and Google Scholar for published research articles regarding the sources, synthesis, and various bioactivities of DAP using different key words, including but not limited to “pharmacological activities,” “sources,” “neuroprotective effect,” “synthesis,” “cancer,” “anti-inflammatory effect” of “daphnetin.” Furthermore, this review encompasses both in-vivo and in-vitro studies on DAP for treating various diseases. A comprehensive review of the literature revealed that the DAP had a promising pharmacological and safety profile, and could be employed as a pharmaceutical moiety to treat a variety of illnesses including microbial infections, cancer, arthritis, hepatic damage, inflammation and neurological anomalies. The current review intends to provide an in-depth focus on all pharmacological activities and therapeutic approaches for the pharmaceutical and biomedical researchers.