Genomics

Lecture 7By 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 tumorBenign Malignant tumorMetastasis

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 nutrition2. Attachment to other cells, membranes or

fibers3. 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-oncogensA 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 spontaneouslyResult from exposure to an carcinogen

( any substance that increases the risk of cancer.)• Usually there is more than one mutation.

Treatment

• 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 re-penetrate 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.