Characterization and antitumor activity of camptothecin from endophytic fungus Fusarium solani isolated from Camptotheca acuminate. Xueqin Ran1, Gen Zhang2, Sheng Li2, Jiafu Wang2,3 1. College of Animal Science, Guizhou University, Guiyang, 550025, China; 2. Institute of Agro-Bioengineering, Guizhou University, Guiyang, 550025, China; 3. Tongren College, Tongren, 554300, China Abstract Background: Camptothecin (CPT) is a potent drug against cancers, originally from plants. The endophytic fungi could produce the secondary metabolite same as the host and is used as medicine. Objectives:The aim of this paper was to investigate an endophytic fungal CPT with anti-neoplastic activity. Methods: Endophytic fungi were isolated from Camptotheca acuminata in China. CPT from strain S-019 was characterized by TLC, HPLC and EI-MS analysis. Anti-tumor activity of fungal CPT was detected by MTT and fluorescent dye methods using Vero and PC-3 cells. Results: A total of 94 endophytic fungi strains were isolated from tissues of C. acuminata and 16 fungi strains displayed cytotoxic activity on Vero or PC3 cells. Of which, the fungal strain S-019, classified asFusarium solani, displayed impressive cytotoxic activ- ity on cancer cells and was found to produce CPT by analysis of TLC, HPLC and EI-MS methods. Bioassay studies confirmed that the fungi CPT had potent cytotoxicity on Vero cells and induced apoptosis of Vero cells. Conclusion: The endophytic fungi from camptotheca trees are a reliable source for natural anticancer compounds. The endophyt- ic fungi could produce CPT same as plant. The fungal CPT exhibited effective activity at inhibiting cell growth and inducing apoptosis on Vero cells. Keywords: Endophytic fungi, camptothecin, anti-tumor, Camptotheca acuminate. DOI: https://dx.doi.org/10.4314/ahs.v17i2.34 Cite as: Ran X, Zhang G, Li S, Wang J. Characterization and antitumor activity of camptothecin from endophytic fungus Fusarium solani isolated from Camptotheca acuminate. Afri Health Sci. 2017;17(2): 566-574. https://dx.doi.org/10.4314/ahs.v17i2.34 Introduction drug against several types of cancer2-4. It is reported that Camptotheca acuminata is a species of medium-sized decid- CPT can induce apoptosis or death in various cancer cells uous trees indigenous to the Southern China1. It is usually by interfering with the topoisomerase I, an essential en- classified in the tupelo family Nyssaceae, which includes zyme in the DNA replication process5-8. Although CPT two species: Camptotheca acuminata Decne and Camptotheca is present in many plants, but two of the plants used for lowreyana. Camptotheca acuminata has been used as tradition- the commercial isolation of CPT are Camptotheca acuminate ally Chinese medicine for centuries, all parts of this fast and Nothapodytes foetida9. Because the over exploitation has growing tree contain the secondary metabolite, camp- resulted in these plant sources to be endangered in Chi- tothecin (CPT, an indole alkaloid), which is an effective na10. It is indispensable to look for alternate sources for this class of natural products. Endophytic fungi have attracted attention for their po- Corresponding author: tentials for producing the secondary metabolite same as Jiafu Wang, the host plant, or novel metabolites11. Endophytic fungi Institute of Agro-Bioengineering are a large group of micro-organisms colonizing in the Guizhou University tissue of plants without causing overt symptoms or ap- Xueshi Road, Guiyang 550025, China parent injury to the host. The plant is thought to provide Tel: +86-851-88298070 nutrients to the endophytic fungi, while the microbe may Fax: +86-851-88298005 produce factors that protect the host plant from attack by E-mail: [email protected] animals, insects or other microbes12. It has been proven African Health Sciences Vol 17 Issue 2, June, 2017 566 that endophytic fungi are a source of providing second- ing. The endophytes from C. acuminata were examined ary metabolites diverse in structure and biologic activi- under light microscope stained with lactophenol cotton ty13,14. Thus, the endophytic fungi in C. acuminata plant are blue16. The total genomic fungal DNA was then extracted expected to be a potential source for CPT or new natural by CTAB method17. The endophytic fungus was identified bioactive agents. This paper described the screening of by analysis of 18S ribosomal genes with primers 5’-TC- endophytic fungi with antitumor activity isolated from C. CGTAGGTGAACCTGCGG-3’ and 5’-TCCTCCGCT- acuminata collected from Guizhou province, SouthWest TATTGATATGC-3’. The amplified products were pu- of China, and demonstrated that an endophytic Fusarium rified utilizing Gel Extraction Kit (Omega, USA), and solani was capable of producing camptothecin which pos- sequenced using ABI 3730 DNA Analyzer (ABI, USA) as sessed of inhibitory activity to cancer cells. per the manufacturer’s instructions. The DNA sequenc- es were submitted to Genbank for homology analysis by Materials and methods BLASTN program. The ribosomal gene database (http// Acquisition of C. acuminata ncbi.nim.nih.gov/) was accessed and sequence alignment Samples of C. acuminata were collected in April from the was used as an underlying basis to identify the fungus. Botanical Garden, South of Guiyang, China. Small ter- The sequence data of strain S-019 had been submitted minal, limbs (1×25 cm) from one to two years old were to the GenBank databases under accession number of harvested and stored in a sealed plastic bag at room tem- EF062312. perature and processed within 2 days. Fungal cultivation and extraction Isolation of strains The fungi were statically cultured for 10 days at 28˚C in The endophytic fungi were isolated from different tis- petri dishes. They were incubated into 1000 mL flasks sues of C. acuminata according to a protocol described containing 500 mL of PDA broth. After 7 days of incu- previously15. Briefly, stem fragments were treated by sur- bation at 28 ± 1˚C on rotary shaker at 150 rotations per face disinfection with 70% (v/v) ethanol for 1 minute minute (rpm), mycelia and broth were separated by fil- to kill epiphytic micro-organisms. Epidermis layers of tration. Mycelia were thoroughly washed with sterile dis- tissues were removed with a sharp blade and the layers tilled water and homogenized in a cell disintegrator. Both of phloem-cambium and xylem tissues were cut into pieces cell homogenate and cell-free broths were extracted four and placed in Petri plates. Pieces of rhizome were thor- times with equal volume of chloroform: methanol (4:1 oughly washed using distilled water and followed by 70% v/v). After stripping off the solvent, a small quantity of (v/v) ethanol for 1 minute and 5% sodium hypochlorite the residue was applied on silica gel thin layer chromatog- for 5 minutes to accomplish adequate surface steriliza- raphy (TLC) plates. The chloroform: methanol (9:1 v/v) tion. They were subsequently rinsed in sterile deminer- solvent system was used for TLC. TLC analysis exhibit- alized water thrice for 1 minute. Small pieces (1 cm) of ed spots which were superimposable with the authentic inner tissue of rhizome were placed on aqueous agar in CPT. The spots were visualized under ultra violet (UV) petri plates and incubated at 28 ± 1 ˚C until the fungal light. The rest of the residue was used for quantification growth was initiated. After several days, individual hyphal of CPT by HPLC. tips were removed and placed on potato dextrose agar (PDA). They were incubated for 10 days, and periodically High performance liquid chromatographic analysis checked for purity. Again, each culture was transferred, HPLC separation was performed on a LC-8 (A) HPLC by hyphal tipping, to a water agar plate containing gam- of authentic CPT and system (Shimadzu, Japan). The ma-irradiated carnation leaves which usually permit the mobile phase was set as methanol: water, 60:40 (pH ≤ 5) development of fruiting structures. and separation was carried out at a flow rate of 1 mL min- 1 over a period of 30 min. The compounds were detected Identification of the endophytes using a UV detector at λmax of 360 nm. The electron The endophytic fungal strains were identified by the mor- ionization mass spectrometry (EI-MS) DATA were col- phological method and reinforced by 18S rDNA sequenc- lected on an HP 5973 mass spectrometer (Hewlett-Pack- ard, America). 567 African Health Sciences Vol 17 Issue 2, June, 2017 Cell lines and normal culture conditions with fermentation broth and mycelia extraction at vari- The cell lines used in this paper were two cancer cell lines: ous concentrations (2.5 to 50 μg mL-1) and at different Vero cell and human prostate cancer cell line pc-3 (PC3 periods (0 to 60 h), suspended cells and trypsinized ad- cell). The cells were grown in 96-well plates (6000 cells herent cells were harvested at previous determined time per well) in Dulbecco’s modified Eagle medium contain- periods, washed in phosphate-buffered saline (PBS) and ing 10% fetal calf serum supplemented with 1000 units centrifuged at 1000 rpm for 10 min to obtain a pellet, and mL-1 penicillin and 100 µg mL-1 streptomycin sulfates, in then resuspended in 0.5 mL of 1% PBS. EB/AO in PBS a humidified atmosphere in 5% CO2 at 37˚C. The expo- (5 µL of a 100 μg mL-1 solution) was added to a 0.1 mL nentially growing cells (1×103) were harvested for next cell suspension, and stained cells were observed by fluo- tests. rescence microscopy (Leica, wetzlar, Germany). A total of 300 cells were counted in multiple randomly selected Analysis of cytotoxic activity fields, and the percentage of apoptotic and dead cells was The cytotoxic effects of fermentation broth and mycelia then calculated. extraction were tested by 3-4, 5-dimethylthiazol-2, 5-di- phenyl tetrazolium bromide (MTT) assay and conven- Results tional ethidium bromide-acridine orange (EB/AO) stain- Screening of endophytic fungi having cytotoxic activity ing.