GPCRs as targets for flavonoids in cancer cells: new options for intervention

For a long time, the family of receptor tyrosine kinases, including epidermal growth factor receptor and insulin-like growth factor 1 receptor, was regarded as the main players stimulating cell proliferative signaling. Today, it is increasingly clear that many G protein-coupled receptors (GPCRs) are also involved in controlling the hallmarks of cancer by activating diverse intracellular signaling networks. GPCRs can therefore be considered as promising drug targets for fighting against diverse types of human malignancies. Although plant polyphenols, flavonoids, are well known for their diverse anticancer effects inhibiting the growth, proliferation, migration, and invasion of malignant cells, involvement of GPCRs in these activities has still remained largely unelucidated. Therefore, in this review article, the current knowledge about the role of GPCRs in anticancer action of structurally varied flavonoids is compiled, highlighting the ability of these natural polyphenols to modulate the expression levels of GPCRs but also suppress the action of endogenous ligands and downstream tumor-promoting events. These data show that targeting the respective GPCRs by specific flavonoids may open new perspectives in the therapeutic intervention in human malignancies.

Flavonoid-Mediated Suppression of Tumor Angiogenesis: Roles of Ang-Tie/PI3K/AKT

Angiogenesis is a process involved in the formation of new blood capillaries from pre-existing ones. It is regulated by several anti-angiogenic molecules involved in tumor growth and metastasis. The endothelial angiopoietin Ang-Tie/PI3K/AKT growth receptor pathway is necessary for healthy vascular development. The activation of AKT is controlled by a multistep process involving phosphoinositide 3-kinase (PI3K). This article aims to provide an overview of the role and mechanism of the Ang-Tie/PI3K/AKT signaling pathways and the potential of flavonoids as anti-angiogenic drugs. Flavonoids have shown great potential in preventing angiogenesis by targeting signaling pathways and exhibit additional anti-cancer properties. Research studies have revealed that the currently available anti-angiogenic drugs do not meet the safety and efficacy standards for treating tumor growth. Phytocompounds have long been a valuable resource for the development of novel therapeutic drugs. This article explores recent findings explaining the role and mechanism of the Ang-Tie/PI3K/AKT signaling pathways, as well as the interaction of flavonoids with angiogenic signaling pathways as a novel therapeutic approach. Several investigations have shown that synergistic studies of natural phytocompounds have great potential to target these pathways to inhibit tumor growth. Therefore, flavonoid-based medications may offer a more effective synergistic strategy to treat cancer.

Diabetes and cancer: two epidemic diseases requiring an opposite therapeutic approach to target cells

Diabetes and cancer are two chronic metabolic diseases with ever-increasing incidence rates worldwide. These disorders can often occur together, as diabetes presents an important risk factor for cancer and some cancers could in turn lead to diabetes. In this perspective article, many more commonalities between diabetes and cancer are highlighted, including the role of lifestyle and environmental factors in the pathogenesis, the presence of a rather long latency period before clinical diagnosis of invasive disease, as well as the ultimate progression to diabetic complications or malignant metastases. Moreover, both of these devastating disorders still lack curative treatment options, whereas several currently approved antidiabetic and anticancer drugs have been originally derived from different natural sources. However, while in the case of diabetes, the main therapeutic goal is to maintain the pancreatic islet mass by preserving β-cells survival, the major purpose of cancer therapy is to kill malignant cells and reduce the neoplastic mass of solid tumors. It is expected that both diabetes and cancer, two systemic diseases with epidemic proportions, would be managed more effectively through an integral approach, considering many different aspects related to their pathogenesis, including also lifestyle changes and dietary modifications.

High intake of sunflower seeds and low mortality from Alzheimer’s disease and dementia: is there a correlation?

Alzheimer’s disease, a progressive and irreversible neurodegenerative disorder, is the most prevalent form of dementia with an increasingly growing incidence rate worldwide. As no effective therapeutic modalities are still available for the treatment of this serious disabling condition, lifestyle modifications, especially nutritional interventions, have been shown to be important in its prevention and symptomatic alleviation. In this short perspective article, an inverse association between the intake of sunflower seeds and the mortality from Alzheimer’s disease and dementia is proposed, showing that in the countries with the highest consumption of sunflower seeds, the death rate from this neurodegenerative disorder is low. The bioactive ingredients of sunflower seeds and their possible neuroprotective mechanisms are further unraveled, highlighting the potent antioxidant, antiinflammatory and neurotrophic effects of tocopherols, unsaturated fatty acids and phytosterols. Among the latter agents, β-sitosterol might be particularly important in combating Alzheimer’s disease by enhancing the levels of nerve growth factor and thereby promoting neurite formation. If future epidemiological studies will confirm the proposed inverse association between the intake of sunflower seeds and the development of Alzheimer’s disease and dementia, it is easy to include appropriate sunflower seed products in the everyday diet to protect against the pathogenesis and progression of this neurodegenerative disorder, especially in individuals with a genetic predisposition. Considering the rather long latency period before clinical manifestation of Alzheimer’s disease, nutritional approaches with specific foods might be a promising strategy for fighting against dementia.

Colonic Degradation as Reverse Process to Flavone Biosynthesis in Plants: Similarities and Differences

BACKGROUND

For many years, it was thought that the main function of the colon is the reabsorption of water and salt and the elimination of unused food materials. Only very recently, a crucial role of the human intestinal microbiota in the metabolism of different food constituents, including plant foods-derived flavonoids, was discovered. Currently, the knowledge about colonic degradation of ingested flavonoids, involved bacteria and produced catabolites is rapidly increasing. In general, flavonoids unabsorbed in the small intestine reach the colon, where they are exposed to the gut microbiota.

CONCLUSION

In this perspective article, colonic degradation of flavonoids is considered a reverse process to their biosynthesis in plants, with a special focus on the subclass of flavones. According to this approach: what is composed in plants, will be decomposed in the human colon. Several inverse similarities are highlighted, including hydrolysis of flavonoid glycosides as the first step in the gut degradation contrasted with the attachment of sugar moiety as the last reaction of flavonoid biosynthesis in plants, colonic reduction contrasted with plant introduction of C2-C3 double bond in the central heterocyclic ring, or microbial ring fission contrasted with plant ring closure of the heterocyclic ring of flavones. Despite these inverse similarities, precursors of flavonoid pathway in plants are different from the spectrum of gut microbial catabolites in humans. In the human colon, a wide variety of phenolic acids are produced from the ingested flavonoids, due to the diverse enzymatic capacity of intestinal microbiota. The bioactivities and potential health impacts of these catabolites are still largely unknown.

Anti-tumor potential of Harmine and its derivatives: recent trends and advancements

Harmine is a β-carboline alkaloid derived from Peganum harmala, showing a solid antitumor potential in different types of human cancer cells. Unfortunately, the clinical application of this natural alkaloid has been impeded till now by severe toxic side effects, especially neurotoxicity, besides its poor water solubility. Therefore, over the recent years, several semisynthetic derivatives of harmine have been prepared and studied concerning their abilities to inhibit tumor cell proliferation, survival, angiogenesis, migration, and invasion in diverse preclinical models. This review article summarizes the anticancer effects of harmine and its synthetic derivatives, demonstrating their high potential to be developed as novel anticancer drugs to supplement our current therapeutic arsenal in the fight against the globally increasing rate of malignant disorders.

Immunotherapeutics in lung cancers: from mechanistic insight to clinical implications and synergistic perspectives

BACKGROUND

Lung cancer is one of the highly lethal forms of cancer whose incidence has worldwide rapidly increased over the past few decades. About 80-85% of all lung cancer cases constitute non-small cell lung cancer (NSCLC), with adenocarcinoma, squamous cell carcinoma and large cell carcinoma as the main subtypes. Immune checkpoint inhibitors have led to significant advances in the treatment of a variety of solid tumors, significantly improving cancer patient survival rates.

METHODS AND RESULTS

The cytotoxic drugs in combination with anti-PD-(L)1 antibodies is a new method that aims to reduce the activation of immunosuppressive and cancer cell prosurvival responses while also improving direct cancer cell death. The most commonly utilized immune checkpoint inhibitors for patients with non-small cell lung cancer are monoclonal antibodies (Atezolizumab, Cemiplimab, Ipilimumab, Pembrolizumab etc.) against PD-1, PD-L1, and CTLA-4. Among them, Atezolizumab (TECENTRIQ) and Cemiplimab (Libtayo) are engineered monoclonal anti programmed death ligand 1 (PD-L1) antibodies that inhibit binding of PD-L1 to PD-1 and B7.1. As a result, T-cell proliferation and cytokine synthesis are inhibited leading to restoring the immune homeostasis to fight cancer cells.

CONCLUSIONS

In this review article, the path leading to the introduction of immunotherapeutic options in lung cancer treatment is described, with analyzing the benefits and shortages of the current immunotherapeutic drugs. In addition, possibilities to co-administer immunotherapeutic agents with standard cancer treatment modalities are also considered.