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Genomics
Lecture 7
By Ms. Shumaila Azam
Tumor
• Tumor – abnormal proliferation of cells that results
from uncontrolled, abnormal cell division
• A tumor is the name for a swelling formed by an
abnormal growth of cells.
• Types of tumor
 Benign
 Malignant tumor
 Metastasis
Benign tumor
• A benign tumor is a mass of cells (tumor) that
lacks the ability to invade neighboring tissue.
• benign tumors are non-cancerous.
• benign tumors generally have a slower growth
rate the tumor cells are usually more
differentiated.
• Benign tumors are typically surrounded by an
outer surface (fibrous sheath of connective
tissue) or remain with the epithelium.
• Common examples of benign tumors include
moles and uterine fibroids (leiomyomas).
Benign Tumor
• The growth of benign tumors produce a "mass
effect" that can compress tissues and may cause
nerve damage, reduction of blood to an area of
the body (ischaemia), tissue death (necrosis) and
organ damage.
• most benign tumors are not life-threatening,
many types of benign tumors have the potential
to become cancerous (malignant) through a
process known as tumour progression.
Treatment
• Some benign tumors need no treatment
– Surgery
– sclerotherapy, a treatment in which chemicals are used to
shrink blood vessels in order to cut off the blood supply.
– Cryotherapy: use of low temperatures in medical
therapy.
– Electrodesiccation: the process of destroying tissue using
heat conduction from a metal probe heated by electric
current.
– laser therapy
– chemical peels
– topical medication are used.
Cancer (malignant tumor)
• Leading cause of death in the United States.
• Cancer is the uncontrolled growth of abnormal cells
anywhere in a body.
• A genetic disease caused by a mutation in the genes
that control cell division.
• cancer cells can break away from original mass of cells,
travel through the blood and lymph systems, and lodge
in other organs where they can again repeat the
uncontrolled growth cycle.
• This process of cancer cells leaving an area and
growing in another body area is termed metastatic
spread or metastatic disease.
•
In normal cells, that frequency of cell division
is governed by several factors:
1. Adequate nutrition
2. Attachment to other cells, membranes or
fibers
3. Division stops if cell become crowded
(usually after 20 – 50) divisions
• Cancer cell continue dividing and ignore the
normal messages to stop dividing.
Types of cancer
• Carcinoma: Cancer that begins in the skin or in tissues that
line or cover internal organs
• Sarcoma: Cancer that begins in bone, cartilage, fat, muscle,
blood vessels, or other connective or supportive tissue
• Leukemia: Cancer that starts in blood-forming tissue such
as the bone marrow and causes large numbers of abnormal
blood cells to be produced and enter the blood
• Lymphoma and myeloma: Cancers that begin in the cells of
the immune system
• Central nervous system cancers: Cancers that begin in the
tissues of the brain and spinal cord
What Causes Cancer?
• There are two types of genes that control cell division
Proto-oncogens
A proto-oncogene is a normal gene that can become
an oncogene due to mutations or increased
expression. Proto-oncogenes code for proteins that
help to regulate cell growth and differentiation.
Tumor suppressing genes (p53 gene)
A tumor suppressor gene, or anti-oncogene, is a
gene that protects a cell from one step on the path
to cancer. When this gene is mutated to cause a loss
or reduction in its function, the cell can progress to
cancer.
What causes cancer?
• Mutations that alter the genes coding for growth
factors.
 May occur spontaneously
 Result from exposure to an carcinogen
( any substance that increases the risk of cancer.)
• Usually there is more than one mutation.
Treatment
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Surgery
Radiotherapy
Chemotherapy
Hormone therapy
Immunotherapy
Gene therapy
Not all tumors are cancerous
• It is important to understand that not all
tumors are cancerous.
– benign tumors where the growth is limited to
certain part of the body.
– A tumor becomes cancer when it is malignant.
This means that the primary growth can generate
several secondary growths thus invading vital
parts of your body and spreading everywhere.
Not all tumors are cancerous
• Just as all tumors are not cancerous, all cancer
cases are also not characterized by tumor growth.
For example, in case of blood cancer, there is no
tumor involved.
• on appearance of a tumor, biopsy becomes very
important to determine if its growth is malignant
or benign.
• A tumor may or may not develop into cancer.
Cancer on the other hand is a malignant
condition in which the spread of abnormal
cellular growth could become uncontrollable.
Metastatic tumor
• Metastasis, or metastatic disease, is the spread of a
cancer from one organ or part to another non-adjacent
organ or part.
• The new occurrences of disease thus generated are
referred to as metastases.
• Some cancer cells acquire the ability to penetrate the
walls of lymphatic and/or blood vessels, after which
they are able to circulate through the bloodstream
(circulating tumor cells) to other sites and tissues in the
body. This process is known (respectively) as lymphatic
or hematogeneous spread.
Metastatic tumors
• After the tumor cells come to rest at another site, they repenetrate the vessel or walls and continue to multiply,
eventually forming another clinically detectable tumor. This
new tumor is known as a metastatic (or secondary) tumor.
• When tumor cells metastasize, the new tumor is called a
secondary or metastatic tumor, and its cells are similar to
those in the original tumor.
• This means, for example, that, if breast cancer metastasizes
to the lungs, the secondary tumor is made up of abnormal
breast cells, not of abnormal lung cells. The tumor in the
lung is then called metastatic breast cancer, not lung
cancer.