Natural Products and Gastric Cancer: Cellular Mechanisms and Effects to Change Cancer Progression.

Gastric cancer is a severe malignant tumor with high morbidity and mortality, which seriously affects people's health. At present, the most common treatment for gastric cancer is chemotherapy. However, chemotherapy is very harmful to the human body, and some of the injuries caused by chemotherapy are irreversible. Natural products have low toxicity and anti-cancer activity, so they are currently widely studied at present. Natural products are a large variety of compounds naturally found in fruits, vegetables, spices, and medicinal plants. It is reported that natural products have different anti-cancer properties. This review has summarized the study of natural products in inducing gastric cancer cell apoptosis, inhibiting gastric cancer cell metastasis, and inhibiting gastric cancer cell proliferation. The relevant references on gastric cancer and natural products were obtained from scientific databases, including Pub- Med, Web of Science, and Science Direct. This paper records dozens of natural products with anti-gastric tumor activity and describes the potential living anti-cancer chemical compounds, their element targets, and their underlying mechanism. This review may lay the foundation for future researchers to treat gastric cancer.

Rich Organic Nitrogen Impacts Clavulanic Acid Biosynthesis through the Arginine Metabolic Pathway in Streptomyces clavuligerus F613-1.

Clavulanic acid (CA) is the preferred clinical drug for the treatment of infections by ß-lactam antibiotic-resistant bacteria. CA is produced by Streptomyces clavuligerus, and although there have been many reports on the effects of carbon and nitrogen sources on CA production, the mechanisms involved remain unclear. In this study, we found that CA accumulation in S. clavuligerus F613-1 was increased significantly in MH medium, which is rich in organic nitrogen, compared with that in ML medium, which contains half the amount of organic nitrogen present in MH medium. Transcriptome analysis revealed that genes involved in CA biosynthesis, such as ceas1, ceas2, bls1, bls2, cas2, pah2, gcaS, and cad, and arginine biosynthesis, such as argB, argC, argD, argG, argH, argJ, and argR, were upregulated under rich organic nitrogen. Metabolome data revealed notable differences between cultures of F613-1 grown in MH and ML media with regard to levels of key intracellular metabolites, most of which are involved in arginine metabolic pathways, including arginine, glutamine, and glutamic acid. Additionally, supplementation of ML medium with arginine, glutamine, or glutamic acid resulted in increased CA production by S. clavuligerus F613-1. Our results indicate that rich organic nitrogen mainly affects CA biosynthesis by increasing the levels of amino acids associated with the arginine metabolic pathway and activating the expression of the CA biosynthetic gene cluster. These findings provide important insights for improving medium optimization and engineering of S. clavuligerus F613-1 for high-yield production of CA. IMPORTANCE The bacterium Streptomyces clavuligerus is used for the industrial production of the broad-spectrum ß-lactamase inhibitor clavulanic acid (CA). However, much remains unknown about the factors which affect CA yields. We investigated the effects of different levels of organic nitrogen on CA production. Our analyses indicate that higher organic nitrogen levels were associated with increased CA yields and increased levels of arginine biosynthesis. Further analyses supported the relationship between arginine metabolism and CA production and demonstrated that increasing the levels of arginine or associated amino acids could boost CA yields. These findings suggest approaches for improving the production of this clinically important antibiotic.