Cyclodipeptide (CDP) composed of two amino acids is the simplest cyclic peptide. These two amino acids form a typical diketopiperazine (DKP) ring by linking each other with peptide bonds. This characteristic stable ring skeleton is the foundation of CDP to display extensive and excellent bioactivities, which is beneficial for CDPs' pharmaceutical research and development. The natural CDP products are well isolated from actinomycetes. These bacteria can synthesize DKP backbones with nonribosomal peptide synthetase (NRPS) or cyclodipeptide synthase (CDPS). Moreover, actinomycetes could produce a variety of CDPs through different enzymatic modification. The presence of these abundant and diversified catalysis indicates that actinomycetes are promising microbial resource for exploring CDPs. This review summarized the pathways for DKP backbones biosynthesis and their post-modification mechanism in actinomycetes. The aim of this review was to accelerate the genome mining of CDPs and their isolation, purification and structure identification, and to facilitate revealing the biosynthesis mechanism of novel CDPs as well as their synthetic biology design.
Actinobacteria/metabolism* ; Actinomyces/metabolism* ; Biological Products/metabolism* ; Bacteria/metabolism* ; Diketopiperazines/metabolism* ; Amino Acids

Aspergillus fumigatus, a type of endophytic fungi from Erthrophleum fordii, was fermented with GPY culture medium. Fermented liquid and mycelium were extracted from fermented products after freezing and thawing treatment. After alcohol extraction, mycelium was extracted with ethyl acetate and n-butyl alcohol, respectively. According to the results of cytotoxity of tumor cells, ethyl acetate extracts were studied for their chemical constituents. Five diketopiperazine compounds were separated and purified with silica gel, MCI and Sephadex LH-20 column chromatography, reversed-phase chromatographic column and preparative HPLC, their structures were identified as cyclo- (R-Pro-R-Phe) (1), cyclo- (trans-4-OH-D-Pro-D-Phe) (2), cyclo- (R-Tyr-S-Ile) (3), cyclo-(R-Phe-S-Ile) (4), and cyclo-(R-Val-S-Tyr) (5) by using spectral methods.
Aspergillus fumigatus ; chemistry ; growth & development ; metabolism ; Cell Line, Tumor ; Diketopiperazines ; chemistry ; isolation & purification ; metabolism ; pharmacology ; Endophytes ; chemistry ; growth & development ; metabolism ; Fabaceae ; microbiology ; Humans ; Mycelium ; chemistry ; growth & development ; metabolism

ATP-Binding Cassette Transporters ; metabolism ; Adenosine ; analogs & derivatives ; therapeutic use ; Animals ; Antineoplastic Agents ; therapeutic use ; Biomarkers, Tumor ; analysis ; Cell Differentiation ; Diketopiperazines ; Heterocyclic Compounds, 4 or More Rings ; Humans ; Neoplasms ; drug therapy ; pathology ; Neoplastic Stem Cells ; cytology ; metabolism ; Protein Kinase Inhibitors ; therapeutic use ; Pyrimidinones ; therapeutic use ; Quinazolines ; therapeutic use ; Signal Transduction ; Triazines ; therapeutic use ; Wnt Proteins ; metabolism

S1-M1-80 cells, derived from human colon carcinoma S1 cells, are mitoxantrone-selected ABCG2-overexpressing cells and are widely used in in vitro studies of multidrug resistance(MDR). In this study, S1-M1-80 cell xenografts were established to investigate whether the MDR phenotype and cell biological properties were maintained in vivo. Our results showed that the proliferation, cell cycle, and ABCG2 expression level in S1-M1-80 cells were similar to those in cells isolated from S1-M1-80 cell xenografts (named xS1-M1-80 cells). Consistently, xS1-M1-80 cells exhibited high levels of resistance to ABCG2 substrates such as mitoxantrone and topotecan, but remained sensitive to the non-ABCG2 substrate cisplatin. Furthermore, the specific ABCG2 inhibitor Ko143 potently sensitized xS1-M1-80 cells to mitoxantrone and topotecan. These results suggest that S1-M1-80 cell xenografts in nude mice retain their original cytological characteristics at 9 weeks. Thus, this model could serve as a good system for further investigation of ABCG2-mediated MDR.
ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; antagonists & inhibitors ; metabolism ; Adenosine ; analogs & derivatives ; pharmacology ; Animals ; Antineoplastic Agents ; pharmacology ; Cell Cycle ; Cell Line, Tumor ; Cell Proliferation ; Cell Survival ; drug effects ; Cisplatin ; pharmacology ; Colonic Neoplasms ; metabolism ; pathology ; Diketopiperazines ; Doxorubicin ; metabolism ; Drug Resistance, Multiple ; Drug Resistance, Neoplasm ; Female ; Heterocyclic Compounds, 4 or More Rings ; Humans ; Inhibitory Concentration 50 ; KB Cells ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Mitoxantrone ; pharmacology ; Neoplasm Proteins ; antagonists & inhibitors ; metabolism ; Neoplasm Transplantation ; Rhodamine 123 ; metabolism ; Topotecan ; pharmacology