● `color{Violet}"Cancer"` is one of the most `color{Violet}"dreaded diseases"` of human beings and is a major`color{Violet}" cause of death"` all over the globe.

● `color{Violet}"More than a million"` Indians `color{Violet}"suffer from cancer"` and a large number of them die from it `color{Violet}"annually"`.

● The mechanisms that underlie development of cancer or `color{Violet}"oncogenic transformation of cells"`, its treatment and control have been some of the most `color{Violet}"intense areas of research"` in biology and medicine.

● In our body, `color{Violet}"cell growth"` and `color{Violet}"differentiation"` is highly `color{Violet}"controlled and regulated"`.

● In cancer cells, there is `color{Violet}"breakdown"` of these `color{Violet}"regulatory mechanisms"`.



● Normal cells show a property called `color{Brown}"contact inhibition"` by virtue of which contact with other cells inhibits their `color{Violet}"uncontrolled growth"`.

● Cancer cells appears to have `color{Violet}"lost this property"`.

● As a result of this, cancerous cells just `color{Violet}"continue to divide"` giving rise to masses of cells called `color{Brown}"tumors"`.

● `color{Violet}"Tumors"` are of two types: `color{Violet}"benign"` and `color{Violet}"malignant"`.

`star` `color{Brown}"Benign tumors"` normally `color{Violet}"remain confined"` to their original location and `color{Violet}"do not spread"` to other parts of the body and `color{Violet}"cause little damage"`.

`star` The `color{Brown}"malignant tumors"`, on the other hand are a `color{Violet}"mass of proliferating cells"` called `color{Violet}"neoplastic"` or `color{Violet}"tumor cells"`.

● These cells `color{Violet}"grow very rapidly"`, invading and damaging the surrounding normal tissues.

● As these cells `color{Violet}"actively divide and grow"` they also starve the normal cells by `color{Violet}"competing"` for vital nutrients.

● `color{Violet}"Cells sloughed"` from such tumors reach `color{Violet}"distant sites"` through blood, and wherever they `color{Violet}"get lodged"` in the body, they start a `color{Violet}"new tumor"` there.

● This property called `color{Brown}"metastasis"` is the most feared property of `color{Violet}"malignant tumors"`.

● `color{Violet}"Transformation"` of normal cells into `color{Violet}"cancerous neoplastic cells"` may be induced by `color{Violet}"physical"`, `color{Violet}"chemical"` or `color{Violet}"biological agents"`.

● These agents are called `color{Brown}"carcinogens"`.

● `color{Violet}"Ionising radiations"` like `color{Violet}"X-rays and gamma rays"` and `color{Violet}"non-ionizing radiations"` like `color{Violet}"UV"` cause DNA damage leading to neoplastic transformation.



● The chemical carcinogens present in `color{Violet}"tobacco smoke"` have been identified as a major cause of `color{Violet}"lung cancer"`.

● Cancer causing viruses called `color{Violet}"oncogenic viruses"` have genes called `color{Violet}"viral oncogenes"`.

● Furthermore, several genes called `color{Violet}"cellular oncogenes"` (`color{Violet}"c-onc"`) or `color{Violet}"proto oncogenes"` have been identified in normal cells which, when activated under certain conditions, could lead to `color{Violet}"oncogenic transformation"` of the cells.

● `color{Violet}"Early detection"` of cancers is essential as it allows the disease to be `color{Violet}"treated successfully"` in many cases.

● Cancer detection is based on `color{Violet}"biopsy and histopathological studies"` of the tissue and blood and bone marrow tests for `color{Violet}"increased cell counts"` in the case of `color{Violet}"leukemias"`.

● In biopsy, a piece of the `color{Violet}"suspected tissue"` cut into `color{Violet}"thin sections"` is stained and examined under microscope (`color{Violet}"histopathological studies"`) by a pathologist.

● Techniques like `color{Violet}"radiography"` (use of X-rays), `color{Violet}"CT"` (computed tomography) and `color{Violet}"MRI"` (magnetic resonance imaging) are very useful to
detect cancers of the internal organs.

● `color{Violet}"Computed tomography"` uses `color{Violet}"X-rays"` to generate a `color{Violet}"three-dimensional image"` of the internals of an object.

● `color{Violet}"MRI"` uses `color{Violet}"strong magnetic fields"` and `color{Violet}"non-ionising radiations"` to accurately detect pathological and physiological changes in the living tissue.

● `color{Violet}"Antibodies"` against `color{Violet}"cancer-specific antigens"` are also used for detection of certain cancers.

● Techniques of molecular biology can be applied to detect `color{Violet}"genes in individuals"` with inherited susceptibility to certain cancers.

● `color{Violet}"Identification of such genes"`, which predispose an individual to certain cancers, may be very `color{Violet}"helpful in prevention"` of cancers.

● Such individuals may be `color{Violet}"advised to avoid exposure"` to particular carcinogens to which they are `color{Violet}"susceptible"` (e.g., tobacco smoke in case of lung cancer).

● The common approaches for `color{brown}"treatment of cancer"` are `color{Violet}"surgery"`, `color{Violet}"radiation therapy"` and `color{Violet}"immunotherapy"`.

In radiotherapy, tumor cells are `color{Violet}"irradiated lethally"`, taking proper care of the `color{Violet}"normal tissues"` surrounding the tumor mass.

● Several `color{Violet}"chemotherapeutic drugs"` are used to kill cancerous cells.

● Some of these are `color{Violet}"specific"` for `color{Violet}"particular tumors"`.

● Majority of drugs have `color{Violet}"side effects"` like `color{Violet}"hair loss, anemia"`, etc.

● Most cancers are treated by combination of `color{Violet}"surgery, radiotherapy"` and `color{Violet}"chemotherapy"`.

● Tumor cells have been shown to `color{Violet}"avoid detection"` and destruction by `color{Violet}"immune system"`.

● Therefore, the patients are given substances called `color{Violet}"biological response modifiers"` such as `color{Violet}"ã-interferon"` which activate their `color{Violet}"immune system"` and help in destroying the tumor.