Cancer is one of the most significant diseases studied in cell biology and pathology. It refers to a group of disorders characterized by the uncontrolled growth and division of abnormal cells in the body. Normally, cell division and death are regulated by genetic control, but in cancer, these controls fail, leading to the formation of a mass of abnormal cells called a tumor.
Definition of Cancer:
Cancer is defined as a disease caused by uncontrolled and abnormal cell proliferation, which may invade and destroy surrounding tissues and spread to other parts of the body through a process known as metastasis.
Characteristics of Cancer Cells
1. Loss of cell cycle control – Cancer cells divide continuously without regulation.
2. Lack of contact inhibition – They continue to grow even when in contact with neighboring cells.
3. Immortality – Cancer cells do not undergo normal programmed cell death (apoptosis).
4. Ability to metastasize – They can spread from their original site to distant organs.
5. Genetic mutations – Oncogenes and tumor suppressor genes are often mutated in cancer cells.
Types of Cancer
1. Carcinomas – Cancers arising from epithelial tissues (e.g., skin, lungs, breast).
2. Sarcomas – Cancers of connective tissues like bone, cartilage, or muscle.
3. Leukemias – Cancers of blood-forming tissues (bone marrow).
4. Lymphomas – Cancers of lymphatic tissues.
5. Melanomas – Cancers originating from pigment-producing melanocytes.
Causes of Cancer (Carcinogens)
Cancer can be caused by a combination of genetic and environmental factors, including:
Chemical carcinogens – e.g., tobacco smoke, aflatoxins.
Physical agents – e.g., radiation, UV light.
Biological agents – e.g., viruses like Human Papilloma Virus (HPV) and Epstein-Barr Virus (EBV).
Genetic mutations – in proto-oncogenes or tumor suppressor genes.
Definition of Carcinogen
A carcinogen is any physical, chemical, or biological agent that can cause cancer by inducing genetic mutations or altering cellular metabolism leading to uncontrolled cell division.
Definition of Proto-oncogene
A proto-oncogene is a normal gene that regulates cell growth and division. When mutated or abnormally expressed, it can become an oncogene, which promotes uncontrolled cell proliferation leading to cancer.
Conclusion:
Cancer remains a major health problem worldwide due to its complex nature and varied causes. Understanding its cellular and molecular basis is essential for the development of effective prevention, diagnosis, and treatment strategies. For B.Sc students, studying cancer helps in understanding how normal cellular mechanisms go wrong, leading to malignant transformation.
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