Mutagenicity and carcinogenicity

1. DRUG DISCOVERY AND DEVELOPMENT
MUTAGENICITY AND CARCINOGENICITY
BY,
R.RAKSHANA
S.SANTHIYA
R.SHANKAR

2. INTRODUCTION:
Humans take a number of drugs for health
reasons, it is practically guaranteed that useful
drug will produce unwanted effects, but some
can produce dangerous effects.
Toxicity refers to these sometimes deadly
effects: though all drugs have adverse effects
at normal doses, it is only the dangerous ones
which is referred as toxic.

3. These are the result of action of drug due to
overdosing or prolonged use.
Toxicity may results from therapeutic effect of
the drug
example: coma by barbiturates
complete Atrioventicular block by
digitoxin.
bleeding due to heparin

4. DRUG TOXICITY: TYPES
Cytotoxicity
Carcinogenicity
Mutagenicity
Teratogenicity

5. CARCINOGENICITY:
A carcinogen is any substance, radionuclide or
radiation that is an agent directly involved in
causing cancer. This may be due to ability to
damage the genome or to the disruption of
cellular metabolic processes.
Radioactive substances are gamma rays and
alpha particles .
Non- radioactive substances are certain
dioxins and tobacco smoke.

6. Classes of chemical tends to be
carcinogens
 Epoxides:
Ethylene oxide
Propylene oxide
 Organohalogen compounds:
vinyl chloride
carbon tetrachloride
chloroform
 Hydrazines:
1,2-Dimethylhydrazine
Hydrazine and salts

7.  N- Nitroso compounds:
N- Nitrosodimethylamine
 Aromatic Amines:
Benzidine
Aniline
o- Anisidine
o- Toluidine
 Aromatic Hydrocarbons:
Benzene
Benz[a] anthracene
Bonzo[a] pyrene

8. How Do Carcinogen enter the body??
Skin absorption: Many solvents and other
chemicals go directly through the skin.
Ingestion: Swallowing of a carcinogen.
Inhalation: Breathing gases, fumes and vapour
is the most common form of exposure.

9. Organs to carcinogens attack:
Liver
Lungs
Kidney
Reproductive system
Skin
Many other organs and tissues

10. MUTAGENICITY:
Some drugs can cause permanent changes to
the DNA of germ cells- Egg cells and sperm
cells- leading to mutation which are inherited
by a patient’s children.
Example: nitrogen mustard-destroys cancer
cells by linking their DNA strands together
with a nitrogen atom, but can also link the
DNA of germ cells, leading to deletion of DNA
bases, thereby causing mutation.

11. Classes of mutations:
• Spontaneous mutation: Cause during DNA
replication or incorporation of incorrect
nucleotide in the growing DNA chain. They
occurs in the DNA sequence.
• Induced mutation: Caused by the changes in
the DNA brought by some environmental
factors called mutagens.
• Example: UV Light

12. TYPES OF MUTATION:
1. Chromosomal mutation:
changes the structure of
chromosome. Loss or
gain of part of
chromosome.
Deletion
Inversion
Translocation
Duplication
Nondisjunction

13. Deletion: due to breakage a piece of
chromosome is lost.
Inversion: chromosome segment breaks and
reattached.
Duplication: occurs when a gene sequence is
repeated.
Translocation: involves two chromosomes that
are not homologous and a part of one is
transferred to another chromosome.
Nondisjunction: failure of chromosome to
separate during meiosis.

14. 2. Point mutation: changes in a single
nucleotide.
Example: Sickle cell disease is the result of
one nucleotide substitution.

15. 3. Frame shift mutation: Insertion or deletion of
one or more nucleotides.

16. Mutagenicity testing:
• Two types:
1. Invitro method
. Bacterial reverse mutation assay
(salmonella typhimurium, E.coli)
. Mammalian cells assay (mouse lymphoma
thymidine kinase)
2. Invivo method
. Micronuclei test
. Comet assay
eg: Ames test

17. AMES TEST:
• A test for determining if a chemical is a mutagen.
• The bacterium used in the test is a strain of
Salmonella typhimurium that caries a defective
mutant gene making unable to synthesize the
amino acid Histamine from the ingredient from
the culture.
• Some type of mutations can be reversed, a back
mutation, with the gene regaining its function.
These revertants are able to grow on a medium
lacking histidine.

18. AMES TEST:
• Utilizes a histidine auxotroph of Salmonella
• Determine if a chemical agent is a mutagen.
• Appearance of many colonies of the microbe
on the minimal plate after the addition of the
test chemical is an indication that the
chemical is a mutagen.

20. SPOT TEST:
• It consist of the incubation of a suitable tester
strain of salmonella tyhimurium+ test agent
place on the agar.
• Chemical is tested on one Petri plate.
• The zone of inhibition is indicated of the
toxicity for the bacterial growth.

21. HOST MEDIATED TEST:
• Methodology:
salmonella are injected intraperitonealy into
a rat or a hamster.
The animal is treated with the test substance
orally.
After sample is withdrawn from peritoneal
cavity and mutation is salmonella is measured.

22. COLIFORM ASSAY:
• Coliform is a bacteria, it measures the E.coli
present in media.
• METHOD: Tester strains of E.coliPQ37+ test
substance incubation with or without S-9 liver
fraction, may show control for protein
synthesis.

23. APPLICATIONS:
• Genetic toxicology (DNA Damage)
In vitro and In vivo evaluation of genotoxic
chemicals .
• DNA Damage
• DNA repair
strand break repair
Excision repair

24. THANK YOU