New Antitumor Antibiotics Nc0604 Separation And Purification, Structure Elucidation And Biological Activity Of,

Bleomycins are a family of glycopeptides originally isolated from Streptomyces verticillus by Umezawa et al in 1966.As a family of antitumor antibiotics,the bleomycins have been widely used clinically in combination with a number of other agents for the treatment of several types of tumors,notably squamous cell carcinoma, malignant lymphoma,testicular carcinomas and ovarian cancer since their discovery. Bleomycins are attractive therapeutics,as they exhibit both low myelosuppression and low immunosuppression with their unique structures and properties in mediating dioxygen activation and sequence selective degradation of DNA.However,the therapeutic efficacy of bleomycins is limited by the development of dose-dependent lung fibrosis.So,more and more research has been focused on the development of a more potent,less toxic compound ofbleomycin group.In the course of a screening program for new compounds of bleomycins,we found a new component from the culture broth of Streptomyces verticillus var.pingyangensis n.var-Q835.The objective component was isolated by ion exchange resins, macroporous resins and CM-Sephadex C-25[NH4⁺]chromatography.And the structure was then elucidated by spectroscopic analyses including IR,UV,ESI-Q-TOF2-MS and NMR.The results showed that it had the same kernel structure as bleomycin,but a different terminal amine moiety determined as amidepropyl spermidine.It was confirmed as a new compound ofbleomycin group and was named as NC0604.The antibacterial spectrum study revealed that NC0604 exhibited antibacterial activity against members of a wide range of bacterial species.Better antibacterial activities were observed against members of Bacillus species and some Gram-negative bacteria.The growth-inhibitory activity in vitro of NC0604 toward various human tumor cells was determined by MTT assay and clonogenic assay.NC0604 showed better activities against a wide range of human tumor species,especially human HepG2,KB, MCF-7,HCT116,BGC-823 and MCF-7/DOX.Tumor inhibitory effect of NC0604 in vivo was evaluated by using the model of subcutaneously transplanted hepatoma H22 in Balb/c female mice.And the tumor inhibitory rates of NC0604 at concentrations of 10.0 mg·kg^-1,5.0 mg·kg^-1 and 2.0 mg·kg^-1 were 91.45%,79.69%and 69.97%,respectively,which were 1.20,1.35 and 1.48 times higher,respectively,than those of bleomycin(75.96%,59.01%and 47.41%, respectively) under the same administration and dosage.The pulmonary toxicity for mice was determined in male Kunming mice.The pulmonary toxicity was evaluated by determining the content of hydroxyproline(HYP) and observing the histopathological changes of the lung tissues at day 28 after administration of the test compounds.Compared with the other members of bleomycins including bleomycin,pingyangrnycin and boanmycin,NC0604 showed reduced pulmonary toxicity but a little bit severe than boningrnycin.We explored primarily the molecular mechanism of action of NC0604 against tumor cells.The results indicated that NC0604 could increase the ROS level,change the mitochondrial transmembrane potential(△ψm) in HepG2 cells and block the cell cycle at G2/M phase.Features of apoptosis such as chromatin condensation in HepG2 cells were observed under florescent microscope following staining with Hochest 33342. Determination of protein molecules related to cell apoptosis further indicated that NC0604 could induce apoptosis of HepG2 cells in vitro.These indicated that inducing increase of the ROS level,interfering with the△ψm and further inducing cell apoptosis may be one antitumor mechanism of NC0604.Since the bleomycin family has special antitumor activations and each member has its strong point,more further research and exploration on the mechanism of action of NC0604 were expected to be continued.