Studies on Screening, Isolation and Molecular Characterization of Anticancerous Compound Producing Marine Bacteria

Studies on Screening, Isolation and Molecular Characterization of Anticancerous Compound Producing Marine Bacteria

Sai Lakshman Mithun V1, C.S V Rama Chnadra Rao2

Department of Biotechnology, DVR & Dr.HS MIC College of Technology, Kanchikacherla, Andhra Pradesh, India.

Abstract

Extracts from microorganisms have served as a valuable source of diverse molecules in many drug discoveries. Identification of microbial strains having promising biological activities and purifying the bio-molecules which are responsible for the biological activities, have led to the discovery of many bioactive molecules. Extracts of bacteria in vitro tested on various cancer cell lines. The lyophilized bacterial extract powder was dissolved in various chemical solvents like Methanol, Chloroform and Ethyl acetate. From them cytotoxic assays was performed the extracts were screened on HCT 15 and MES- SA cancer cell lines to study the cytotoxic potential. Where the Ethyl acetate showed the inhibition when compared to other solvents. The Ethyl acetate extract of isolate showed promising results by MTT assay and Trypan blue staining. Identification of the microorganism, the selected isolates was characterized by using the 16s rRNA sequencing based on microbial characterization. The organism was identified as Micrococcus luteus and biochemical tests of the extracts were also carried out.

Key words: Anticancer, Bacterial extracts, MTT assay, HCT 15 cell line, MES-SA cell line.

INTRODUCTION

Cancer is a disease in which a cell, or a group of cells represents uncontrolled growth invasion (intrusion on and distortion of adjacent tissues), and metastasis (spread from one part to another part in the body through lymph or blood). These three malignant properties differentiate cancer from benign tumors, which are self-limited and do not invade or metastasize while the malignant tumors are not self limited and metastasize. Most of cancers occur form a tumor; the oncology is deals with the study, diagnosis, treatment, and prevention of cancer and its a branch of medicine. Cancer is a human tragedy that affects people at all ages with the risk in most types increasing with age. Cancers are primarily an environmental disease with 90-95% of cases due to modification in lifestyle and environmental factors and 5-10% due to genetics. Cancer is caused by both external factors (tobacco, chemicals, radiation and infectious organisms) and internal

factors (inherited mutations, hormones, immune conditions and mutation that occurs from metabolism). Common environmental factors leading to cancer death include: tobacco 25-30%, diet and obesity 30-35%, infections 15-20%, radiation, stress, lack of physical activity and environmental pollutants. [B Dhorajiya et al., 2011].

Early discovery of carcinogens by John Hill, an English physician, 1761. In it he made the first causal link between substances in the environment and cancer when he described a relationship between tobacco snuff and nasal cancer. This brought about the awareness of carcinogens (chemical agents that have been demonstrated to cause cancer). That associated particular occupations with an increased risk of developing specific forms of cancer the forerunner to the field of public health and cancer.[C. A. Almeida and S. A. Barry, 2010].

Natural products have played an important role in treating and preventing human diseases. Natural products with medicinal value have come from various sources viz., terrestrial plants, terrestrial microorganisms, marine organisms, and terrestrial vertebrates and invertebrates the microbial extracts have served as a valuable source of diverse molecules in many drug discovery efforts and led to the isolation of several important drugs. [Newman et al., 2002]. The chemical composition of bioactive compounds of microbial origin is often highly complex. Organic compounds from aqua to terrestrial microorganisms have extensive use in the treatment of many diseases and serve as compounds of interest both in their natural form and as templates for synthetic modification. These compounds provided important contributions to the discovery of antibacterial agents like penicillins, cephalosporins, tetracyclines, and polyketides, immunosuppressive agents like cyclosporins, antidiabetic agent like acarbose, cholesterol-lowering agents like lovastatin and mevastatin and anti cancer agents like peplomycin, pentostatin, and epirubicin [Butler, 2005; Sneader, 2005]

MATERIALS AND METHODS

Screening and isolation of bacterial strains:

Collection of soil sample:

Marine soil samples were collected from Bay of Bengal coast of Machilipatnam, Krishna district, AP, India. About 15 grams of soil sediments were collected in a sterile polythene bags and stored at 4oC until further use. The soil samples were stored under sterile conditions for preventing the bacterial cross contamination. Then the sample was serially diluted to till 10-6 dilution by adding 1 gram of soil to 10ml of distilled water.

Screening for bacterial single isolates:

From the serially diluted samples, 100µl of sample was poured on Nutrient Agar plates (Himedia). From the 10-5 and 10-6 dilutions the single isolated bacterial colonies were obtained on agar plates by the procedure according to [Shirai et al. (1989).]

Sub culturing of bacterial isolates:

The inoculum was prepared by transferring a single colony of the isolates into 5 ml of the corresponding medium. This inoculum was transferred to 95 ml of the corresponding broth and bacterial isolates were incubated at c for 2 -3 days .this broth was used for the extraction of bioactive metabolites.

Extraction of bioactive principles:

The culture broth was centrifuged at 3000 rpm for 15 min to obtain a clear supernatant. Com- ponents were extracted successively dissolved with chemical solvents such as chloroform (C), Methanol (M) and Ethyl acetate (E) and followed by vacuum evaporation of these extracts to obtain the dry extracts by vacuum rotary evaporator. [Angel TreasaThomas etal., 2011]

Sample preparation for biological studies:

The bacterial crude extracts were dissolved in 1 ml DMSO and transferred to sterile vials of 2 ml capacity; these samples were stored at room temperature for further use, protected from light.

Maintenance of cancer cell lines:

Human colarecta adeno carcinoma Cancer cells (HCT 15) and Human uterine cancer cells (MES-SA) were maintained in Dulbeccos modified essential medium (DMEM) supplemented with 4.5 g/l glucose and 2mm 1-glutamine and 5% fetal bovine serum (FBS) (growth medium) at c in 5% incubator.

Trypan blue dye exclusion technique:

A cell suspension was made with a fixed volume of cells (e.g. 1ml). Although an aseptic technique is not essential in all stages of this procedure, 50uL of cell suspension was taken and mixed it with an equal volume of trypan blue. Mix solution well using a pipette. It transfers to a hemocytometer and then counted live cell as clear form and dead cell as blue cells. After staining with trypan blue solution counting should commence <5minutes as after that time the cells will begin to take up the dye. A pipette was used to place some of the cell suspension: trypan blue mix into the hemocytometer and overlay with a coverslip. The cell suspension will pass under the coverslip by capillary action unless there is an air bubble. Make sure the wells are no overfilled and that the coverslip is not moved once it was placed on the grid and the cell solution is added. The hemocytometer was placed on the stage of an inverted microscope. Fcus was

adjusted and power until a single counting square fills the field. The number of cells per ml, and the total number of cells were counted using the following formula:

Calculate percent viability by using formula:

% viability = (live cell count/total cell count) ×100

Anticancer assay:

Microculture tetrazolium (MTT) assay:

The monolayer cell culture was trypsinized and the cell count was adjusted to 1ml using medium. To each well of 96 well microtitre plates, 0.1ml of diluted cell suspension was added. After 72 hour, the sample solution in wells was flicked off and 50l of MTT dye was added to each well. The plates were gently shaken and incubated for 4 hours at 37 c in 5% CO2 incubator. The supernatant was removed, 50 l of Propanol was added, and the plates were gently shaken to solubilize the formed formazan. The absorbance was measured using a micro plate reader at a wavelength of 490 nm. The percentage growth inhibition was calculated using the Formula below:

The percentage growth inhibition was calculated using following formula:

%cell inhibition= 100-{(At-Ab)/ (Ac- Ab)} x100 Where,

At= Absorbance value of test compound Ab= Absorbance value of blank

Ac=Absorbance value of control [T. Mosmann, J. Immunol. Methods]

Identification of microorganism:

Biomass culture for anticancer activity assays was carried out in 500 mL conical flasks at 37°C temperature. Total DNA was extracted and PCR amplification was performed according to the method described by[ Fawley and Fawley (2004)] using following primers:

Forward primer- 51 GGCGAACGGGTGAGTAA 31

Reverse primer- 51 ACTGCTGCCTCCCGTAG 31

The Genomic DNA was isolated from the overnight grown bacterial culture was amplified with universal bacterial primers. A 25l of reaction mixture contains 15l of master mix (10 x assay buffer, dntps, Taq polymerease and MgCl2), 1l of forward primer, 1l of reverse primer, 2l of template DNA and 6l of distilled water. PCR was carried out by the thermal cycler under the following conditions- An intialization step at 94ºC for 4min followed by 30 cycles of 94ºC for 1min, 52ºC for 1min, 72ºC for 1.15min followed by final extension at 72ºC for 1min and holding temperature at 10ºC for 1min. The amplified DNA fragments were observed by agarose gel electrophoresis in 2% agarose gel and sequenced. The unknown bacterium was identified using

GenBank database. The amplified PCR products were directly sequenced in an ABM Prism 3100-Avant Sequencer. The obtained sequences were analysed using BLAST tool to get the relative identification of each bacterial species. After this the bacterial extracts were subjected to thin layer chromatography for detecting the activity of extract and their components

Screening of Bacterial metabolite with GC-MS:

The active bacterial extract which was showing the maximum inhibition on cancer cell lines growth was analysed by Gas Chromatography and Mass Spectrophotometer, using this technique the main compound having the anticancerous activity can be detected

RESULTS AND DISCUSSION

Cancer cells were tested with Chloroform, Methanol and Ethyl acetate bacterial extracts cell viability was evaluated by MTT assay. A gradual decrease in the viability of HCT 15 and MES-SA cancer cells were observed in for all the bacterial extracts used in the study. The bacteria was identified as Micrococcus luteus by 16s r RNA sequencing.

MTT cell growth inhibition assay was taken as in vitro measure of anticancer activity of bacterial extracts by using different cancer cell lines. Ethyl acetate extracts of bacteria are effective in inhibiting cancer cell growth of the two cancer cell lines. Therefore present invitro studies on ethyl acetate bacterial extracts demonstrate the remarkable anticancer potentials due to the presence of active principles may responsible for this anti cancer activity. Hence Micrococcus luteus Ethyl acetate extracts can be used as a potent natural source of anticancer agent. The GC-MS analyses the bacterial extract and compound identified as pyrrolo (1,2-alpha) pyrazine1,4 dione hexahydro 3-(2-methylpropyl)

Trypan blue staining Report:

The trypan blue staining was performed and the cancer cell line viability cell proliferation as shown below

Table 1: Trypan blue staining % of Viability of cancer cells

MTT assay Report:

From the Table 2 and graph 1: we can say that as the concentration of Chloroform, Methanol and Ethyl acetate bacterial extracts increased from 50 to 500 µl/ml, the % MES-SA cancer cell growth inhibition was increased from 36.40% to 70.61% in chloroform bacterial extract, 39.35 % to 73.22 % in Methanol bacterial extract and 37.52 % to 78.94 % in Ethyl acetate bacterial extract, that means they induces a cell arrest to inhibit the growth of the MES-SA cancer cells.

From the Table 3 and graph 2: we can say that as the concentration of Chloroform, Methanol and Ethyl acetate bacterial extracts increased from 50 to 500 µl/ml, the % HCT 15 cancer cell growth inhibition was increased from 33.24 % to 73.56 % in chloroform bacterial extract, 37.52

% to 78.94 % in Methanol bacterial extract and 43.67 % to 89.65 % in Ethyl acetate bacterial extract, that means they induces a cell arrest to inhibit the growth of the HCT 15cancer cells

Table 2: Percentage of MES-SA cell inhibition at various concentrations

Percentage of MES-SA cell inhibition vs conc. of C,M and E

90

80

% of MES-SA cell inhibition

70

60

Chloroform bacterial

50 extract

Methanol bacterial

40 extract

30 Ethyl acetate bacterial

extract

20

10

0

50 100 250 500

Concentration (µl/ml)

Figure 1: Effect of Chloroform, Methanol and Ethyl acetate bacterial extracts on MES-SA cancer cell growth inhibition

Table 3: Percentage of HCT 15 cell inhibition at various concentrations

100

% 0f HCT 15 cell inhibition

90

80

70

60

50

40

30/p>

20

10

0

Percentage of HCT 15 cell inhibition vs conc.of C, M and E

Chloroform bacterial extract

Methanol bacterial extract

Ethyl acetate bacterial extract

50 100 250 500

Concentration (µl/ml)

Figure 2: Effect of Chloroform, Methanol and Ethyl acetate bacterial extracts on HCT 15 cancer cell growth inhibition

CONCLUSION

Bacterial extracts of the metabolites were in vitro tested for their cytotoxic potential on various cancer cell lines. The extracts were screened on HCT 15 and MES-SA cell lines. The Ethyl acetate extract of bacterial isolate showed promising results by MTT assay and Trypan blue staining. The isolate was identified as Micrococcus luteus sp. showing promising results were obtained showing anti cancerous activity

ACKNOWLEDGEMENTS

SAI LAKSHMAN MITHUN V would like to thank Department of Biotechnology, DVR& Dr.HS MIC College of Technology, Kanchikacherla, Andhra Pradesh for their cooperation to complete this work For Masters degree

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