CANCER

Cancer is one of the most dreaded (deadly) diseases in this world. Lots of people are due to cancer. It is the major cause of death, all over the world. More than a million Indians suffer from cancer and so many of them die due to this. Cancer is an incurable disease, I any person detected cancer then their life got ruined by this disease.

What do you mean by cancer?

  • Uncontrolled, abnormal, and excessive mitotic(Equational) divisions of cells 
  • Study of cancer: Carcinology/Oncology
  • The mechanisms that underlie the development of cancer or oncogenic transformation of cells, its treatment, and control have been some of the most intense areas of research in biology and medicine. 

Types of Cancer


Points About Cancer


  1. Most fatal Cancer:- Leukemia
  2. Most common fatal Cancer:- Lung Cancer 
  3. Most common Cancer (worldwide):- Lung Cancer 
  4. Most common cancer in females (worldwide):- Breast Cancer 
  5. Most common cancer in males (worldwide):-Prostate Cancer 
  6. Most common cancer in females (India):- Cervical Cancer 
  7. Most common cancer in males (India):- Oral Cancer   


Mechanism of Cancer


In our body, cell growth and differentiation are highly controlled and regulated. In cancer cells, there is a breakdown of these regulatory mechanisms. Several genes called cellular oncogenes (c-onc) or proto-oncogenes have been identified in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells. Tumor suppressor genes inhibit cellular proliferation
Agents that promote the proliferation of cells, which have already undergone genetic alternations responsible for oncogenic transformation. These agents are called tumor promoters.
eg. Some growth factors and hormones.
  

Property of Cancer cells

  1. Normal cells show a property called contact inhibition under which contact with other cells inhibits their uncontrolled growth. Cancer cells appear to have lost this property. As a result of this, cancerous cells just continue to divide giving rise to masses of cells called tumors.
  2. Cancer cells are anchorage-independent and insensitive to population density.
  3. Cancer cells are immortalized by the mechanism that maintains the length of telomeres (HeLa cells, 1951).
  4. Cancer cells are spread by invasion and metastasis.

Tumors

Tumors are of two types: benign and malignant. Benign tumors normally remain confined to their original location and do not spread to other parts of the body and cause little damage. The malignant tumors, on the other hand, are a mass of proliferating cells called neoplastic or tumor cells. These cells grow very rapidly, invading and damaging the surrounding normal tissues. As these cells actively divide and grow they also starve the normal cells by competing for vital nutrients.

Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property called metastasis is the most feared property of malignant tumors.

Difference between a benign tumor and malignant tumor


Carcinogens


Cancer-causing agents are known as carcinogens. There are 3 types of carcinogens
  1. Physical agents 
  2. Chemical agents 
  3. Biological agents

Physical Agents


Ionizing radiations like X-rays and gamma rays and non-ionizing radiations like UV rays cause DNA damage leading to neoplastic transformation. For e.g. Xeroderma pigmentosum is caused by UV rays in which thymine dimer is formed. Agents: e.g.  Sometimes, injury due to sharp teeth causes tongue cancer.    
 Kashmiri people keep 'Kangri' close to the skin that causes skin cancer and this skin cancer is called kangri cancer.

Chemical Agents


The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer. Tobacco and betel chewing cause oral cancer. Combustion products of coal and pesticides, artificial flavor, sweeteners, synthetic food, etc cause cancer. Hormonal imbalance or estrogen excess causes breast cancer. Urinary bladder cancer is common in dye workers.


Biological Agents 

It includes oncogenic viruses. Oncogenic viruses have genes called viral oncogenes. 
e.g.

  1. Rous sarcoma virus
  2. Hepatitis B & C viruses
  3. Human papilloma virus
  4. Epstein Barr virus
  5. Herpes virus, etc.
  6. Helicobacter pylori bacteria can cause gastric carcinoma. 

Cancer detection and diagnosis 

Early detection of cancers is essential as it allows the disease to be treated successfully in many cases. Following are the techniques for cancer detection and diagnosis :

  1.  Blood examination:-
(a)Test for increased cell counts in case of leukemias

(b) Detection of the tumor markers in blood like 

  •  α-fetoprotein (AFP) for liver cancer
  • PSA (prostate-specific antigen) for prostate cancer
  • Alkaline phosphatase for bone metastasis 

     2.   Imaging (X-Ray, Sonography, CT Scan, MRI, etc.):-

These techniques are very useful to detect cancers of the internal organs. 
  • In sonography, high-frequency sound waves (ultrasound) are used to produce dynamic visual images of internal organs
  • In X-rays scan and CT (Computed Tomography) scan, X-rays are used to generate, respectively, a two-dimensional (2D) and three-dimensional (3D) image of the internals of an object.
  • In MRI (Magnetic Resonance Imaging), strong magnetic fields and non-ionizing radiations are used to accurately detect pathological and physiological changes in the living tissue.

  3. Biopsy and histopathological study:-

  •  In a biopsy, a piece of the suspected tissue cut into thin sections is stained and examined under the microscope (histopathological studies) by a pathologist.
 

4. Modern techniques

  • Antibodies against cancer-specific antigens are also used for the detection of certain cancers.
  • Techniques of molecular biology can be applied to detect genes in individuals with inherited susceptibility to certain cancers. Identification of such genes, which predispose an individual to certain cancers, may be very helpful in the prevention of cancers. Such individuals may be advised to avoid exposure to particular carcinogens to which they are susceptible. e.g.: Tobacco smoke in case of lung cancer 
 Treatment of cancer

  1. Surgery
  2. Radiotherapy
  3. Chemotherapy
  4. Immunotherapy
  5. Cancer vaccine(Research is in progress to develop cancer vaccines.)