CARCINOGENS and it's types chemical,physical and biological carcinogens

1. PRESENTED BY:
Aishwarya H . A,
1st Msc, 1st sem,
Dept of Biotechnology,
Sahyadri Science College,
Shivamogga.
KUVEMPU UNIVERCITY
SAHYADRI SCIENCE COLLEGE
SEMINAR TOPIC
'Carcinogens’

2.  CONTENTS:
• INTRODUCTION
• TYPES OF CARCINOGENS
1. Chemical Carcinogens
A. INITIATORS
B. PROMOTER CARCINOGENS
3. Biological carcinogens
1. Radiation physical agents.
2. Non-radiation physical agents.
2. Physical carcinogens
1. DNA oncogenic viruses.
2. RNA oncogenic viruses.
• CONCLUSION
• REFERENCE

3.  A carcinogen is a substance or agent known to cause
cancer or produces an increase in incidence of cancer in
animals or humans.
 Carcinogens may be chemical substances; physical agents,
UV radiation; or biological agents, such as certain viruses
and bacteria.
 A carcinogen may be the initiator the agent that alters or
damages DNA, the basic coding system of cells.
Introduction
 Carcinogenesis / Oncogenesis / Tumorigenesis means mechanism of
Induction tumours (pathogenesis of cancer)

4. NORMAL CELLS CANCER CELLS
Carcinogenic agent
Mutations/ chromosomal
translocation
CARCINOGENESIS

5. Etiology and pathogenesis of cancer can be
discussed under following 3 headings:
1. Chemical carcinogens
2. Physical carcinogens
3. Biologic carcinogens

6. Chemical Carcinogens:
• Depending upon the mode of action of carcinogenic chemicals
they are divided into 2 broad groups:
CHEMICAL CARCINOGENS
A. INITIATORS B.PROMOTERS
1. DIRECT-ACTING
CARCINOGENS
These carcinogens don't require
any metabolic conversion to
become carcinogenic. They
directly damage the DNA causing
mutations
2. INDIRECT-ACTING
CARCINOGENS
These are chemical Substances
which require prior metabolic
activation before becoming
potent 'ultimate' carcinogens.
A process in which existing
tumors are stimulated to
grow tumor. promoters are
not able to cause tumors to
form.

7. A. INITIATORS
DIRECT-ACTING CARCINOGENS:
1. Nitrosamines

8. INDIRECT-ACTING CARCINOGENS
(PROCARCINOGENS):
i) Polycyclic Aromatic Hydrocarbons:

9. B. PROMOTER CARCINOGENS
• Chemical carcinogenesis can be learned in
three steps:
1. INITIATION OF CARCINOGENESIS
2. PROMOTION OF CARCINOGENESIS
3. PROGRESSION OF CARCINOGENESIS

10. 1. INITIATION OF CARCINOGENESIS:
• Pathogenesis is different with direct
and indirect carcinogens.
DIRECT CARCINOGENS
(ELECTRONPHILIC) DNA Damage.
INDIRECT CARCINOGENS
(INACTIVE FORMS)
ACTIVE CARCINOGENS
(ELECTRONPHILIC)
DNA
Damage
Activation
in liver

11. 2.Promotion of Carcinogenesis
• Promotion is the next sequential stage in the chemical
carcinogenesis.
• Promoters of carcinogenesis are substances such as
 Phenols,
 Hormones,
 Artificial Sweeteners,
 Drugs like Phenobarbital.

12. 3. Progression of Carcinogenesis
• Progression of cancer is the stage when mutated
proliferated cell shows phenotypic features of
malignancy.
• These features pertain to morphology, biochemical
composition and molecular features of malignancy
• The new progeny of cells that develops after such
repetitive proliferation inherits genetic and
biochemical characteristics of malignancy.

13. CHEMICAL
CARCINOGEN
NORMAL
CELL
MUTATED
CELL
MUTATE
D CELL
MUTATE
D CELL
CANCER
CELL
CANCER
CELL
PROMOTERS
DNA
DAMAGE
INTIATION PROMOTION
CELL DIVISION
PROGRESSIO
N
CHEMICAL CARCINOGENESIS

14. PHYSICAL CARCINOGENS :
Physical carcinogens are divided into 2 groups:
A. Radiation physical agents.
I. Ultraviolet light
II. Ionising radiation
B. Non-radiation physical agents.
I. Gallstones
II. Healed scars

15. A. Radiation physical agents
1. ULTRAVIOLET LIGHT
• The main source of UV radiation is the sunlight;
others are UV lamps and welder's arcs.
• Ex : Malignant melanoma , Skin cancer

16. 2. IONIZING RADIATION
• Ionizing radiation has enough energy to damage DNA
and cause cancer.
• Examples: Leukemias myeloid, Thyroid
• IONIZING RADIATION which can ionize atoms:
 X-rays
 Alpha rays (emitted by radioactive Uranium, Radium)
 Beta rays (emitted by decaying nuclear fuel)
 Gamma-rays (Sun, Nuclear explosions).
 Neutrons
 Protons

17. B. Non-Radiation physical agents
Examples (Rare).
 GALLSTONES: Stones in the gallbladder and in the urinary
tract having higher incidence of cancers of these
organs.(liver, pancreas )

18.  Healed scars: Healed scars following burns
or trauma for increased risk of carcinoma of
affected skin.

19. BIOLOGICAL CARCINOGENS :
• Various biological agents like VIRUSES, PARASITES,
FUNGI, BACTERIA are implicated in etiology of cancer.
• However, the role of viruses in the causation of
cancer is more significant.
• Therefore, biologic carcinogenesis is largely
viral carcinogenesis.

20. EXAMPLES OF BIOLOGICAL CARCINOGENS:
BIOLOGICAL
CARCINOGENS
VIRUSES
1. HPV (Anal cancer,
cervical cancer )
BACTERIA
like HELICOBACTER
PYLORI (Stomach
cancer)
FUNGUS
like ASPERGILLUS
FIAVUS (Liver cancer)
PARASITES
like SCHISTOSOMA
HAEMATOBIU( Bladder
squamous cell
carcinoma)M(Bladder

21. ONCOGENIC VIRUSES:
• 20% of all cancers worldwide are due to
persistent virus infection.
Oncogenic viruses are of two types:
1. DNA oncogenic viruses.
HEPADNAVIRUSES
 Hepatitis B Virus - Hepatocellular carcinoma
2 .RNA oncogenic viruses.
LYMPHOTROPIC VIRUS
 HTLV – I - Adult T- cell leukamea lymphoma

22. Conclusion
 According to this theory, the origin of cancer is due to
structural anomalies of the genes that regulate cell growth.
 Genetic changes can be hereditary or they can occur in
the course of life under the carcinogenic action of various
pathogenic factors.
 Cancer prevention is action taken to lower the risk of
getting cancer.
 This can include maintaining a healthy life style , avoiding
exposure to known cancer causing substances or taking
medicines or vaccines for prevention of cancer.

23. Reference
 Alice Marcus - Genetics
www.mjppublishers.com
 Dr . P. S Verma , Dr . V. K Agarwal - Molecular Biology S. Chand
Publication. (Publishing year 2014)
 Textbook of CELL and MOLECULAR BIOLOGY, Ajoy Paul, 4th edition.