1. Uncontrolled Growth and Division:
* Dysregulation of Cell Cycle Checkpoints: Normal cells have checkpoints that regulate the cell cycle, ensuring proper DNA replication and damage repair. Cancer cells bypass these checkpoints, leading to uncontrolled and rapid division.
* Mutations in Genes Regulating Growth and Division: Genes like p53 (a tumor suppressor) and oncogenes (genes promoting growth) are often mutated in cancer cells. This disrupts the balance of cell cycle control, leading to unrestrained growth.
2. Genomic Instability:
* Frequent DNA Mutations: Cancer cells accumulate a high number of mutations in their DNA, often due to defects in DNA repair mechanisms. These mutations can lead to increased proliferation, resistance to cell death, and invasion into other tissues.
* Chromosomal Abnormalities: Cancer cells often display abnormal chromosome numbers (aneuploidy) or structural changes, like translocations, deletions, and amplifications. These abnormalities further contribute to uncontrolled growth and division.
3. Evasion of Cell Death:
* Resistance to Apoptosis: Normal cells undergo programmed cell death (apoptosis) when damaged or abnormal. Cancer cells often evade apoptosis, allowing them to survive and multiply despite defects.
* Increased Telomerase Activity: Telomeres are protective caps at the ends of chromosomes that shorten with each cell division. Cancer cells often have increased activity of telomerase, an enzyme that maintains telomere length, allowing them to divide indefinitely.
4. Angiogenesis and Metastasis:
* Formation of New Blood Vessels: Cancer cells release signals that stimulate the growth of new blood vessels (angiogenesis), providing them with nutrients and oxygen to sustain their growth.
* Spread to Other Tissues (Metastasis): Cancer cells can invade surrounding tissues and spread to distant sites through the bloodstream or lymphatic system, establishing new tumors (metastases).
Consequences:
These abnormalities in cell division lead to the hallmarks of cancer:
* Uncontrolled growth and proliferation: The formation of tumors.
* Invasion and metastasis: The spread of cancer to other parts of the body.
* Resistance to therapy: Cancer cells can become resistant to chemotherapy and radiation therapy due to mutations and other changes.
It's important to note that these are just some of the key features of cancerous cell division. Cancer is a complex disease with a wide range of mutations and abnormalities, and each type of cancer can have its own unique characteristics.
