Introduction to Screening Models Of Anti Cancer Drugs Need for novel anti cancer drugs, In - vitro methods, In - vivo methods, Advantages and disadvantages Presented by T. Niranjan Reddy Department of Pharmacology

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Presented by
T. Niranjan Reddy
(Reg. No: 20L81S0109)
Under the guidance of
Dr. k.Somasekhar Reddy, M. Pharm., PhD
Associate Professor and Head,
Department of pharmacology.
SCREENING MODELS OF ANTI CANCER
DRUGS
A seminar as a part of curricular requirement for 1st year
M. Pharm 1st semester

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1. Introduction.
2. Need for novel anti cancer drugs.
3. In - vitro methods.
4. In - vivo methods.
5. Advantages and disadvantages.
6. References.
Contents

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Cancer is a disease which is characterized by uncontrolled proliferation of
cells that have transformed from the normal cells of the body.
Causes
• External Factors - chemicals, radiation, viruses, and lifestyle
• Internal Factors - hormones, immune conditions, and inherited mutations
Types of tumors
 Benign
 premalignant
 malignant
Cancer

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Although 92 approved anti cancer drugs are available today for
the treatment of more than 200 different tumor entities, effective
therapies for most of these tumors are lacking.
Thus, the need for novel drugs to treat malignant disease
requiring systemic therapy is still pressing.
A preselection, called the screening process, is therefore
required.
The aim of screening efforts is to identify products that will
produce antitumor effects matching the activity criteria used to
define which compounds can progress to the next stage in the
preclinical development program.

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• Development of multidrug resistance in patients.
• Long-term treatment with cancer drugs is also associated with severe side
effects.
• Cytotoxic drugs have the potential to be very harmful to the body unless
they are very specific to cancer cells.
• New drugs that will be more selective for cancer cells
NEED FOR NOVELANTI-CANCER
DRUG

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METHODS
In Vitro:
1. Tetrazolium salt assay.
2. Sulphorhodamine B assay.
3. 3H-Thymidine uptake.
4. Dye exclusion test.
5. Clonogenic test
6. Cell counting assay.
7. Morphological assay
Anti – Tumor models

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In Vivo:
1. Carcinogen induced models
2. Viral infection models
3. Transplantation Models
4. Genetically Engineered Mouse Models
5. In vivo hollow fibre assay

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1. Tetrazolium salt assay
• This assay is a sensitive, quantitative and reliable colorimetric assay that measures
viability, proliferation and activation of cells.
• The assay is based on the capacity of mitochondrial dehydrogenase enzymes in
living cells to convert the yellow water-soluble substrate 3-(4,5-dimethylthiazol-2
yD)-2,5-diphenyl tetrazolium bromide (MTT) into a dark blue formazan product
which is insoluble in water.
• The amount of formazan produced is directly proportional to the cell number in
range of cell lines.
IN-VITRO METHODS

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It is performed to determine the Enzymatic properties.
Cells from particular cell lines in log phase of growth are trypsinised,
It is counted in a hemocytometer and adjusted multiwell plates
(96 well plates)
The cells are treated with a various concentration of drug for specified
duration
METHOD

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After MTT dye is added in each well and plates are incubated at 37° C for 4
hrs in a Co, incubator.
The plates are taken out from ne incubator and dark blue colored formazan
crystal are thoroughly dissolved in DMSO in room temperature.
The plates are then read with ELISA reader at 570 nm
To calculate the percent cell viability with respect to control is calculated.

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Hemocytometer
• The most common routine method for cell counting which is efficient and
accurate is with the use of a hemocytometer.
 O % cell viability =(OD of treated cells/ OD of control cells)× 100
Hemocytometer Cell Counts

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Untreated Treated
Viable cells

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The Sulphorhodamine B assay measures whole-culture protein
content, which should be proportional to the cell number.
Cell culture are stained with a protein staining dye, Sulphorhodamine
B.
SRB is a bright pink anionic dye that binds to basic amino acid of cell.
Unbound dye is then removed by washing with acetic acid.
Sulphorhodamine B Assay

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• During the dead cell either lyse or are lost during procedure, the
amount of SRB binding is proportional to the number of live cells left
in a culture after drug exposure.

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• This assay is based on the structural integrity of the cells.
• Live cells possess intact cell membranes that exclude certain dyes,
such as tryphan blue, Eosin, or propidium, whereas dead cells would
have lost membrane integrity.
• Hence they would take up the dyes while the live cells exclude it.
Dye exclusion test

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Cell lines are counted, cultured and inoculated in 96 well plates as above.
Cells were incubated with different concentrations of test compounds for
4days.
Number of cultured cells in different wells were counted using
hemocytometer after staining with suitable dyes.
METHOD
%cell viability = no. of viable cell ÷ Total no.of cells X100

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Tryphan blue dye
Untreated live cells Treated cells
HOECHST DYE

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Advantages:
• Reduce the usage of animals.
• Less time consuming, cost effective & easy to manage
• Able to process a larger number of compounds quickly
• with minimum quantity. Range of concentrations used are comparable to
that expected for in vivo studies.
Disadvantages:
• Difficulty in Maintaining of cultures. Show Negative results for the
compounds which gets activated after body metabolism and vice versa.
• Impossible to ascertain the Pharmacokinetics

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DMBA induced mouse skin papillomas
• Two stage experimental carcinogenesis
 Initiator - DMBA (dimethylbenzajanthracene),
 Promotor - TPA (12-O-tetradecanoyl-phorbol-13 acetate)
• Mice : Single dose - 2.5 ug of DMBA, 5 to 10 ug of TPA in 0.2 ml of
acetone twice weekly.
• Papilloma begins to appear after 8 to 10 wks - Tumor incidence &
multiplicity of treatment group is compared with DMBA control group
Chemical carcinogen model

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Mice are topically applied a single dose of 2.5 ug DMBA in acetone, followed
by 5-10 ug of TPA in 0.2 ml acetone twice weekly on the same site starting
one week after DMBA application.
Percent tumor incidence and multiplicity of treatment groups is compared
with DMBA control group.
Drug under test can be administered either topically or oral route.

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The tumor incidence in this model is usually about 100% DMBA controls.
In repeated topical application of DMBAAlone has also been shown to
induced carcinogenesis.
Drug efficacy is measured as percent reduction in carcinoma incidence,
compared with that of carcinogen control.

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Mouse skin papillomas RAT mammary gland CA

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• Mouse Mammary Tumor Virus (MMTV) was the first mouse virus,
isolated at Jackson labs as the "non chromosomal factor” that caused
mammary tumors in the C3H strain of mice.
• Some viruses cause cancer via random integration in certain cells
• Some viruses carry cellular oncogenes
 Abelson murine leukemia virus – Abl
 Moloneymurine sarcoma virus - Raf ©
• Engineered viruses now used routinely in the laboratory to induce cancer.
Viral infection models

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• Tumor cells or tissues (mouse or human) transplanted into a host mouse.
• Ectopic - Implanted into a different organ than the original (typically
subcutaneous or kidney capsule) o Orthotopic - Implanted into the
analogous organ of the original tumor.
• Advantages :
 Typically cheap, fast & easy to use.
 Not covered by patents
Transplantation Models

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• In vivo screening tool implemented in 1995 by NCI.
• 12 human tumor cell lines (lung, breast, colon, melanoma, ovary, and
glioma.
• Cells suspended into hollow polyvinylidene fluoride fibers implanted IP or
SC in lab mice
• After in vivo drug treatment, fibers are removed and analyzed in vitro
• Antitumor (growth inhibitory) activity assessed
In Vivo Hollow Fibre Assay

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Subcutaneous hollow fibre implants

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• Currently, pharmaceutical firms spend a large amount of money on the
compound efficacy and cytotoxicity test.
• There is still a 78% failure rate for all drugs, which may be devastating to
developing companies.
• Effective compounds in vitro may be non-effective in vivo for many
reasons, including differences between in vitro and in vivo target biology,
interrelated biochemical mechanism, metabolism, poor penetration into
solid tissues, etc.
2-D and 3-D Cell-based Assays in
Drug Screening

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• Currently, almost all cell-based assays or biosensors are developed in 2-D
culture systems, although conventional 2 D cultures usually suffer from
contact inhibition and a loss of native cell morphology and functionality.
• In comparison with 2-D cultures, 3-D cell models create a more realistic
representation of real human tissues, which is critical to many important
cell functions, including morphogenesis, cell metabolism, gene expression,
differentiation and cell-cell interactions.

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1. Ashish A., Sonia SY, Mark AH, and Minas TC., Pressure Related apoptosis in
Neuronal Cell Lines., Journal of Neuroscience Research 2000 60: 495-503
2. KD Tripathi ,Essentials of medical pharmacology , 7th edition page no :85
3. http://www.emblheidelberg.de/ExternalInfo/karsenti/countingcells.html
References

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