Cancer Biology

Introduction to cancer

Our bodies are made up of millions of tiny cells. Most of our cells divide and multiply from time to time - when an old cell is worn out or damaged, a new cell is formed to replace it. Each cell contains genes (made up from DNA). The proteins inside the gene control when the cell should divide and multiply.

If the gene is damaged or altered, the cell becomes abnormal. This abnormal cell can then divides and multiply, without knowing when to stop. When a group of abnormal cells clump together and grow, a tumour forms.

 

Cancer

Cancer is marked by the unrestrained growth of cells, often with invasion of healthy tissues, locally or throughout the body. Cancer is the common term of all malignant tumors.

Tumor

Tumor is a new growth of tissue in which the multiplication of cells is uncontrolled and progressive; neoplasm.

 

Types of tumor

There are two types of tumours:

1.      Benign tumours are not cancerous, and will not invade or spread to other parts of the body.

2.      Malignant tumours are the real cancers. They can grow very quickly, invade nearby tissues and organs, and cause damage. They may even spread to other parts of the body and cause secondary tumours (metastases

Types of cancer

There are about 200 different types of cancer. Some types are more serious than others, some are more easily treated, and others have better survival rates.

They include: bladder, breast, colon, rectal, kidney (renal cell) cancer, leukaemia, lung, pancreatic, prostate, melanoma, and thyroid cancer.

 

Cancer Types

Categorized based on the functions/locations of the cells from which they originate:

a)      Carcinoma: a tumor derived from epithelial cells, those cells that line the surface of our skin and organs (80-90% of all cancer cases reported)

b)      Sarcoma: a tumor derived from muscle, bone, cartilage, fat or connective tissues.

c)      Leukemia: a cancer derived from white blood cells or their precursors.

d)      Lymphoma: a cancer of bone marrow derived cells that affects the lymphatic system.

e)      Myelomas: a cancer involving the white blood cells responsible for the production of antibodies (B lymphocytes).

 

 

Characteristics of Cancer Cells

(1)    Excessive autonomous cell growth

Ø  tumor cells produce growth factors that stimulate their own proliferation (i.e. autocrine stimulation)

Ø  malfunction in cell regulatory systems (i.e. abnormal receptors signal cell division in absence of growth factor)

Ø  loss of growth inhibitory signals (i.e. contact inhibition)

(2) Invasiveness (means tendency to spread)

Ø  ability to grow into adjacent tissue

(3) Ability to metastasize (means to invade distance structure of the body)

Ø  spread to new sites and form new growths

Ø  lack of cell-cell contact inhibition (i.e. disorderly migration over adjacent cells)

Ø  production of enzymes that degrade protein barriers

Ø  production of growth factors that stimulate blood vessel in growth

(4)  Defective differentiation and immortality

Ø  related to uncontrolled proliferation (i.e. differentiated cells don't divide)

Ø  failure of cancer cells to undergo programmed cell death

(5)  Genetic instability

 

Cancer Detection and Diagnosis

1. One of the key problems in the treatment of cancer is the early detection of the disease.
2. Often, cancer is detected in its later stages, when it has compromised the function of one or more vital organ systems and is widespread throughout the body.

Symptoms

1. unexplained lumps and swellings,
2. tiredness,
3. weight loss,
4. poor appetite,
5. night sweats,
6. fever, and
7. Anaemia

Causes

1. Hereditary. 
2. Smoking.
3. Diet.
4. Environmental factors such as UV light from the sun.

Diagnosis

1. X-ray.
2. Ultrasound.
3.  Computerised tomography (CT) scan.
4. Magnetic resonance imaging (MRI) scans.
5. Positron emission tomography scans (PET).
6. Once the problem area is found, blood and tissue samples (biopsy) will be taken for analysis and testing to determine if, or how far, the cancer has spread in the body (this is called staging).

Prevention

1. Stop smoking.
2. Eating a healthy diet.
3. Reducing alcohol intake.
4. Using protection from the harmful effects of the sun

An Introduction to Cancer Treatments

The treatment given for cancer is highly variable and dependent on the type, location and amount of disease and the health status of the patient.

The treatments are designed to either:

q  directly kill/remove the cancer cells or

q  to lead to their eventual death by depriving them of signals needed for cell division or

the treatments work by stimulating the body's own defenses

 

Treatment

1. Surgery

            -the main treatment for most solid tumours, especially when the cancer is in the early stages and has not spread to other areas of the body.

2. Radiotherapy

-aims to destroy the cancerous cells with radiation from X-rays.  

3. Chemotherapy

-Different drug combinations are given depending on the type of cancer. The drugs are given either by mouth, or more commonly by IV, to try and kill cancer cells or stop them from spreading.

4.  Hormonal Treatments

-These drugs are designed to prevent cancer cell growth by preventing the cells from receiving signals necessary for their continued growth and division.

5.      Prevent metastasis

           -Metastasis is a process of malignant cells spread to a new location from original organ. We can stop cancer by prevent metastasis.

6.      Block angiogenesis

                     -Growth of new blood vessels generated for tumor cells is called angiogenesis. We can                          prevent cancer by block angiogenesis.

 

New types of cancer treatment

1. Specific Inhibitors: Drugs targeting specific proteins and processes that are limited primarily to cancer cells or that are much more prevalent in cancer cells.
2. Antibodies:  The antibodies used in the treatment of cancer have been manufactured for use as drugs.
3. Biological Response Modifiers: The use of naturally occuring, normal proteins to stimulate the body's own defenses against cancer.

4.      Vaccines: Stimulate the body's defenses against cancer. Vaccines usually contain proteins found on or produced by cancer cells. By administering these proteins, the treatment aims to increase the response of the body against the cancer cells.     

 

Growth fraction

Tumor cells can be classified as proliferating cells and non-proliferating cells.

The ratio of proliferating cells in the whole tumor tissue is called growth fraction (GF).

The faster the tumor cells proliferate, the bigger the GF is and the higher the sensitivity of tumor to a drug is. Generally, in the early stage, the GF of a tumor is bigger and the effect of a drug on the tumor is better.