Isolation of ketomycin from Actinomycetes as an inhibitor of 2D and 3D cancer cell invasion

Prephenate decarboxylase: An unexplored branchpoint to unusual natural products

Prephenate decarboxylases are a small family of enzymes which initiate a specialized divergence from the shikimate pathway, where prephenate (2) is decarboxylated without aromatization. In addition to effecting a challenging chemical transformation, prephenate decarboxylases have been implicated in the production of rare specialized metabolites, sometimes directly constructing bioactive warheads. Many of the biosynthetic steps to natural products derived from prephenate decarboxylases remain elusive. Here, we review prephenate decarboxylase research thus far and highlight natural products that may be derived from biosynthetic pathways involving prephenate decarboxylases. We also highlight commonly encountered challenges in the structure elucidation of these natural products. Prephenate decarboxylases are a gateway into understudied biosynthetic pathways which present a high potential for the discovery of novel and bioactive natural products, as well as new biosynthetic enzymes.

Bioactive Metabolites from Terrestrial and Marine Actinomycetes

Actinomycetes inhabit both terrestrial and marine ecosystems and are highly proficient in producing a wide range of natural products with diverse biological functions, including antitumor, immunosuppressive, antimicrobial, and antiviral activities. In this review, we delve into the life cycle, ecology, taxonomy, and classification of actinomycetes, as well as their varied bioactive metabolites recently discovered between 2015 and 2023. Additionally, we explore promising strategies to unveil and investigate new bioactive metabolites, encompassing genome mining, activation of silent genes through signal molecules, and co-cultivation approaches. By presenting this comprehensive and up-to-date review, we hope to offer a potential solution to uncover novel bioactive compounds with essential activities.

Induction of apoptosis and cell cycle arrest in colorectal cancer cells by novel anticancer metabolites of Streptomyces sp. 801

Background

Colorectal cancer is the third and most significant cause of death and fourth most common cancer in the world. Chemotherapy can be introduced in the cases of locally or distantly invasive colorectal cancer. In recent years Actinomycetes, especially the genus Streptomyces, contain numerous bioactive compounds, some of which are known as important anti-tumor chemotherapy drugs. In this research, we aimed to explore the anti-cancer mode of action of Streptomyces sp. 801 on colorectal cancer cells in vitro conditions.

Methods

Fermented supernatant of strain Streptomyces sp. 801 isolated from soil showed maximum growth inhibition on human colorectal cancer cells. The cytotoxic effects of various concentrations of EtOAc extract from bacterial culture supernatant on HT-29, HCT 116 and SW480 cancer cells were surveyed using the MTT assay. Moreover, flow cytometry assays and Bax, Bcl-2, Cyclin D1 and P21 gene expressions were carried out to assess the apoptotic and cell cycle effects. Also, the scratch assay was performed to measure migration. Finally, Ethyl acetate (EtOAc) extract was analyzed by LC–MS to identify anti-cancer compounds.

Results

The cell viability of all three cell lines were decreased in a dose-dependent manner. The successful induction of apoptosis and cell cycle arrest at IC₅₀ values, were confirmed by flow cytometry as well as by the mRNA expression levels of the genes involved in these processes. Scratch assays indicated the inhibition of cell migration in the cancer cell lines treated by Streptomyces sp. 801. Nine anti-cancer compounds of Streptomyces sp. 801 were detected by liquid chromatography–mass spectrometry (LC–MS) analysis.

Conclusions

These findings suggest that Streptomyces sp. 801 can be a source of promising anticancer metabolites.

Graphical Abstract

Marine Actinomycetes, New Sources of Biotechnological Products

The Actinomycetales order is one of great genetic and functional diversity, including diversity in the production of secondary metabolites which have uses in medical, environmental rehabilitation, and industrial applications. Secondary metabolites produced by actinomycete species are an abundant source of antibiotics, antitumor agents, anthelmintics, and antifungals. These actinomycete-derived medicines are in circulation as current treatments, but actinomycetes are also being explored as potential sources of new compounds to combat multidrug resistance in pathogenic bacteria. Actinomycetes as a potential to solve environmental concerns is another area of recent investigation, particularly their utility in the bioremediation of pesticides, toxic metals, radioactive wastes, and biofouling. Other applications include biofuels, detergents, and food preservatives/additives. Exploring other unique properties of actinomycetes will allow for a deeper understanding of this interesting taxonomic group. Combined with genetic engineering, microbial experimental evolution, and other enhancement techniques, it is reasonable to assume that the use of marine actinomycetes will continue to increase. Novel products will begin to be developed for diverse applied research purposes, including zymology and enology. This paper outlines the current knowledge of actinomycete usage in applied research, focusing on marine isolates and providing direction for future research.

Inhibition of matrix metalloproteinase expression and cellular invasion by NF-κB inhibitors of microbial origin

Matrix metalloproteinases (MMPs) are zinc-dependent extracellular matrix remodeling endopeptidases. MMPs cleave various matrix proteins such as collagen, elastin, gelatin and casein. MMPs are often implicated in pathological processes, such as cancer progression including metastasis. Meanwhile, microorganisms produce various secondary metabolites having unique structures. We designed and synthesized dehydroxymethylepoxyquinomicin (DHMEQ) based on the structure of epoxyquinomicin C derived from Amycolatopsis as an inhibitor of NF-κB. This compound inhibited cancer cell migration and invasion. Since DHMEQ is comparatively unstable in the body, we designed and synthesized a stable DHMEQ analog, SEMBL. SEMBL also inhibited cancer cell migration and invasion. We also looked for inhibitors of cancer cell migration and invasion from microbial culture filtrates. As a result, we isolated a known compound, ketomycin, from Actinomycetes. DHMEQ, SEMBL, and ketomycin are all NF-κB inhibitors, and inhibited the expression of MMPs in the inhibition of cellular migration and invasion. These are all compounds with comparatively low toxicity, and may be useful for the development of anti-metastasis agents.