biology of cancer

By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

 Synopsis:-
• Introduction
•Tumours
•Types of Tumours
•Formation of Tumours
•How cancer cell differ from normal cells
•Classification of cancer
•The causes of cancer
•Viruses and Cancer
• Cancer and Gene: A. Oncogene
B. Tumours suppressor gene
•Detection and Diagnosis
• Therapy of cancer
•How can cancer are prevented
•Conclusion
•References

• The term cancer, which means “crab” in Latin, was coined by Hippocrates in
the fifth century B.C.to describe diseases in which tissues grow and
spread unrestrained throughout the body eventually choking off life.
• Cancer can originate in almost any tissue of the body.
• Somatic cell of higher eukaryote has limited life span and their growth and
division and growth and an ability to grow in appropriate location. This are said
to be cancerous or tumorigenic cell and they produce cancer.
• Cancer results from a breakdown of the regulatory mechanism that governs
the division,differentiation and survival of individual cells. As a result of the
loss of regulation, cancer cells grow and divide in an uncontrolled manner.
Introduction:-

• The cells which undergo rapid, abnormal and uncontrolled growth at the cost
of remaining cells are called neoplastic cells. These proliferating cells form a mass
of undifferentiated cells.This cell mass is called tumour or neoplasm or cancerous growth.
OR
• Cancer is actually a group of diseases that involve uncontrolled division of cells.These
cells also lose their attachments to other cells and are capable of moving around. These
properties permit the spread of cancerous cells throughout the body.
Definition:-

Tumours:-
Types of Tumours:-

• Benign tumours have slow growing cells contained within layer of connective
tissue.
• Benign tumours can be removed effectively by surgery. They usually don’t
reappear.
• Benign tumours remain localized in a specific area at the site of origin forming a
single mass enclosed in a capsule. Usually these are not fatal.
a. Benign Tumours:-

• Malignant tumours are cancerous.
• Their cells are poorly differentiated with high rate of mitosis, nuclear
polymorphism and abnormal mitosis.
• Malignant tumors are a more serious problem because they can invade
surrounding tissues and enter into the circulatory system allowing them to
spread to distant parts of the body by the process of metastasis.
• The movement of malignant cells form their original site to other body areas is
called metastasis.
b. Malignant Tumours:-

Fig:- Diagram showing non malignant(benign) and malignant [www.google.com]

Generally cancer cells are produced due to following 3 types of changes:-
a. Immortalization : Acquisition of property of indefinite growth by animal cell is terme
immortalization.
b. Transformation : conversion of normal mammalian cell into a cell with cancer like
properties usually by a virus or other cancer causing agents.
c. Metastasis : When the tumours become malignant its cell detach and migrate to other part of
body where they produce secondary tumour this phenomena is
called metastasis.

Fig. Steps in the process of metastasis [Cell and molecular biology -Lewis J.Kleinsmith ]

• Tumor formations is multi stage process, and require several steps, which
is then followed by further changes to strengthen the tumorigenic state.
1. Tumor initiation (Due to genetic alteration & cell proliferation)
2. Tumor progression (Tumor progresses with mutation)
3. Clonal selection (Selection of rapid growing cell & they become
dominant within tumor,
producing mutated cells)
 Formation of Tumor:-
o STEPS ARE:-

Fig.Cancer cell
formation[www.wikipedia.co
m]

Fig- Showing tumor
formation[Gene 9-
Benjamin Lewin]

Signs and symptoms:-
Symptoms of cancer metastasis depend on the location of the tumor.
o Cancer symptoms can be divided into three groups:-
• Local symptoms : unusual lumps or swelling (tumor), hemorrhage (bleeding), pain
• Symptoms of metastasis(spreading) : enlarged lymph nodes
and hemoptysis, hepatomegaly(enlarged liver),bone
pain, fracture of affected bones and neurological symptoms.
•Systemic symptoms : weight loss, poor appetite, excessive sweating (night sweats), anemia and
specific paraneoplastic phenomena, i.e. specific conditions that are
due to an active cancer, such as thrombosis or hormonal changes.

 How cancer cell differ from normal cells:-
• The nucleus of cancer cells are usually enlarged and have irregularly distributed chromatin.
The interchromatin and perichromatin granules which are formed of RNA and proteins are
more abundant in the nucleus of cancer cells. The nucleolus of cancer cells displays hypertrophy.
It becomes more irregular and enlarged. Sometimes several nucleoli may be present in the nucleus
of cancer cells.
• The ergsatoplasm and ribosomes are more abundant in cancer cell.
• The normal cells have a cytoskeleton of microtubules and microfilaments arranged in some
regular fashion and help in coordinated cell movement. In cancer cells, the cytoskeleton
undergoes depolymerization and disintegration, thus cells become independent and their
movements uncoordinated.

Classification of Cancer:-
• Cancers can be classified on the basis of the original tissue from where
they arose:-
o Carcinoma: which are the most common types of cancer, arise form the epithelial cells
that cover external and internal body surfaces.
• Lung, breast, prostate, and colon cancer are the most frequent cancers of this type.
o Sarcoma: Origin in supporting connective tissues of mesoderm origin, such as bone, cartilage,
fat, connective tissue and muscle.
o Lymphoma and leukemia’s : arise from cells of blood and lymphate origin.
• These are tumours of the haematopoeitic cells.

THE CAUSES OF CANCER:-
• Cancer is ultimately the result of cells that uncontrollably grow and do
not die.
• Normal cells in the body follow an orderly path of growth, division, and
death.Programmed cell death is called apoptosis, and when this
process breaks down,cancer begins to form.
A. Heredity:-
• Most forms of cancer are sporadic, meaning that there is no inherited cause of the
cancer.
• There are, however, a number of recognised syndromes where there is an inherited
predisposition to cancer, often due to a defect in a gene that protects against tumor
formation.
• Examples:-Familial adenomatous polyposis an inherited mutation of the APC gene
that leads to early onset of colon carcinoma.
•Retinoblastoma, when occurring in young children, is due to a hereditary mutation in
the retinoblastoma gene.

• Chromosomal aberration occurring in somatic cell, non-reproductive cells,
results somatic mutation.
• The abnormal chromosome helps the somatic cells to get transformed into cancer.
C. Chromosomal Aberrations:-
•. Chromosomes are observed best at the metaphase stage of cell division because
the chromosomes are most condensed at this stage.
• .In human chromosomal abnormalities of tumours include both number and
structure.
• During anaphase of mitosis , one/many chromosome fail to migrate at distant
places resulting in production of daughter cells which may be
trisomic(containing both of the chromosomes of a pair i.e.2n+1)or monosomic
(devoid of a pair of chromosome i.e.2n-1)
B. Somatic and Multiple mutations:-

• The environmental factors that are the probable cause of cancer include
ionizing radiations,diets, personal habits, occupation, smoking, etc.
All the agents that cause cancer are known as carcinogens.
• UV light and IFR break chromosomes and delete the genetic material
resulting in Changes in genes. Occasionally; the damaged cells are also
killed. This results in cancer.
D. Environmental factors:-

Fig. Effects of ionizing radiation on (A) Normal cells(B)cancer cells[www.wikipedia.com]

E. Chemicals:-
• The incidence of lung cancer is highly correlated with smoking.
• Cancer pathogenesis is traceable back to DNA mutations that impact cell
growth and metastasis.Substances that cause DNA mutations are known
as mutagens, and mutagens that cause cancers are known as
carcinogens.
Viruses and Cancer:-
• Certain families of viruses can infect vertebrate cells and transform
them into cancer cells.
• The transforming viruses have been divided into two groups :-
a. DNA tumour viruses
b. RNA tumour viruses
• On the basis of their genomic nucleic acid.

• Transformation by a virus may be defined as:-Changes in the biologic function of a cell that
result from regulation of the cell by viral genes and that confer on the infected cell
certain properties characteristic of neoplasia. These changes often (but not always) result
from integration of the viral genome into the host cell genome.
• DNA tumour viruses :- The viruses that contain DNA as their genetic material and induce
tumour are called DNA tumour viruses.
• For example :- Papova viruses (SV 40, polyoma and papilloma-viruses), Adenoviruses,
Herpes viruses, Poxviruses and hepatitis B virus.
• RNA tumour viruses (Retroviruses):-All RNA tumour viruses belong to the retrovirus family.
• They cause adult T-cell leukemia in humans.

Cancer and gene:-
• Cancer are the result of a disruption of the normal restraints on cellular
proliferation.
• It is apparent that the number of way in which such disruption can occur is
strictly limited and there may be as few as forty cellular genes in which
mutation or some other disruption of their expression leads to unrestrained
cell growth.
• There are two classes of these genes in which altered expression can lead to
loss of growth control:-
(A)Oncogene
(B)Tumour suppressor gene

(A) Oncogene:-
• Those genes that are stimulatory for growth and which cause cancer when
hyperactive.mulations in these genes will be dominant.These genes are called
oncogens.
• The name is derived from the Greek word oncos, meaning bulk or mass, because of the
ability to cause tumor growth.
• The oncogene was discovered in 1970 and was termed src (sarcoma). Src was first
disease as an oncogene in a chicken virus.
• When proto-oncogene mutated [changes] into one oncogene, it become permanently
“Turned on” or activated when it is not supposed to be. When this occurs, the cell
divides so quickly, this can lead to cancer
• Activation of proto-oncogenes by point mutation,amplification or dysregulation
converts the proto- oncogenes into oncogenes(tumour-causing genes)

Fig- Showing ‘turning on’ of oncogene.[www.oncogene.com]

(B)Tumour suppressor gene:-
• Those genes that inhibit cell growth and which cause cancer when they are
turned off.Mutations in these will be recessive.These are the anti-oncogenes
or tumour suppressor gene.
• When tumor suppressor genes don’t work properly, cells can grow out of
control, which can lead to cancer or malignancy.
 EXAMPLES OF TUMOR SUPPRESSOR GENES:-
1) RB-the Retinoblastoma gene:-
Retinoblastoma is a cancerous tumor of the retina i.e. a childhood disease in
which tumor form at retina.

Also, two gene homologous to RB have their protein products, p107 & p130 (based on mass), and
they also play key roles in cell-cycle regulation.
Fig:-A child with retinoblastoma.[www.oncogene.com]
It occurs in two forms:-
•Familial Retinoblastoma
•Sporadic Retinoblastoma

[fig.showing pathognesis of retinoblastomawww.kbiotech.com]

2) p53 (guardian of the Genome)
• Another major tumour suppressor gene is called p53 a gene that is more frequently
mutated in human cancer that any other known gene.
• The product of this gene is a cell cycle inhibitor.

Detection and Diagnosis:-
• Cancer diagnosis is based on the characteristic histological features of malignant cells.
Blood tests for abnormal WBCs and bone marrow biopsy are also used.
• Non -invasive techniques like X-rays (using injected dyes),CT scans and MRI scans can
be used to detect cancers of internal organs like kidneys and pancreas.
• Modern techniques monitor and detect the molecular changes that occur in
cancer cells.Monoclonal antibodies against cancer specific antigens are coupled to
appropriate radioistopes.These antibodies are then used for detection of cancer.

Therapy of cancer: -
• Treatments usually fall into one of the following categories:
surgery, radiation, chemotherapy, immunotherapy, hormone therapy,
or gene therapy.
A. Surgery:-
• Surgery is the oldest known treatment for cancer.
• If a cancer has not metastasized, it is possible to completely cure a
patient by surgically removing the cancer from the body.

• Radiation treatment, also known as radiotherapy, destroys cancer
by focusing high-energy rays on the cancer cells.
• Radiotherapy utilizes high-energy gamma-rays that are emitted
from metals such as radium or high-energy x-rays that are created in
a special machine.
B. Radiation:-

C. Chemotherapy:-
• Chemotherapy utilizes chemicals that interfere with the
cell division process-damaging proteins or DNA -so
that cancer cells will commit suicide.
D. Immunotherapy:-
• Immunotherapy aims to get the body's immune system to
fight the tumor.
• Systemic immunotherapy treats the whole body by
administering an agent such as the protein interferon alpha
that can shrink tumors.

• Hormone therapy is designed to alter hormone production in
the body so that cancer cells stop growing or are killed completely.
• Breast cancer hormone therapies often focus on reducing estrogen
levels and prostate cancer hormone therapies often focus on
reducing testosterone levels.
• Gene therapy is to replace damaged genes with ones that work
to address a root cause of cancer: damage to DNA.
E. Hormone therapy:-
F. Gene therapy:-

• Cancers that are closely linked to certain behaviors are
the easiest to prevent.
• For example, choosing not to smoke tobacco or drink
alcohol significantly lower the risk of several types of cancer –
most notably lung, throat, mouth, and liver cancer.
• Skin cancer can be prevented by staying in the shade,
protecting yourself with a hat and shirt when in the sun,
and using sunscreen.
• Certain vaccinations have been associated with the prevention
of some cancers.
• For example, Hepatitis B vaccines prevent the hepatitis B virus,
which can cause liver cancer.
How can cancer be prevented:-

• Cancer is a collection of disease in which cell growth and division are unregulated.
• Cancer is a lethal disease; it is caused due to various agents or by cellular or viral
oncogene conversion.
• Cancer cell loss the regulatory function and start to proliferate uncontrollably.
• Through various mechanisms a proto-oncogene can be converted into infections
‘oncogene’ which leads to cause cancer. Failure of ‘tumor suppressor gene’ also
causes cancer.
Conclusion:-

S. NO BOOKS AUTHORS
1 Gene IX Benjamin Lewin
2 The cell –A Molecular Approach-
4th edition
Geoffery M. Cooper Robert E.
Hausmen.
3 Molecular genetics of cancer
2nd edition
C. B powar
4 Principle of cell and molecular
biology
Lewis J. kleinsmith Valerie
M.
5 Molecular biology
4th edition
Gerald karp
•References :-
www.google.com
www.wikipedia.com
www.kbotech.com
www.oncogene.com
•INTERNET

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