What is Cancer?
Cancer is a group of diseases characterized by the uncontrolled division and spread of abnormal cells. These cells can invade nearby tissues and spread to other parts of the body through the blood and lymph systems. The primary hallmark of cancer is the disruption of normal cellular processes which leads to malignancy.
-
Initiation: Genetic mutations in a cell's DNA occur due to exposure to carcinogens such as tobacco smoke, radiation, or certain chemicals. These mutations can activate oncogenes or deactivate
tumor suppressor genes.
-
Promotion: Mutated cells are stimulated to grow and divide uncontrollably. This stage may be influenced by factors like hormones, immune responses, and additional genetic changes.
-
Progression: Cancer cells acquire further mutations and become more aggressive. They develop the ability to invade surrounding tissues and spread, or
metastasize, to distant sites in the body.
1.
Cell Cycle Regulation: Normal cells undergo a controlled series of events leading to cell division. In cancer, this regulation is lost, leading to unchecked cell proliferation. Proteins like
cyclins and cyclin-dependent kinases (CDKs) play crucial roles in cell cycle control, and their dysregulation is common in cancer.
2. Apoptosis: Also known as programmed cell death, apoptosis is a mechanism that allows the body to remove damaged or unnecessary cells. In cancer, the pathways that regulate apoptosis are often altered, allowing cancer cells to evade this process and survive longer than they should.
3.
Angiogenesis: Tumors need a blood supply to grow beyond a certain size. Angiogenesis is the formation of new blood vessels, and it is often hijacked by cancer cells to supply nutrients and oxygen. The
VEGF (vascular endothelial growth factor) pathway is a critical regulator of this process.
4.
DNA Repair: The ability to repair DNA damage is essential for maintaining genomic integrity. Cancer cells often have defects in DNA repair mechanisms, leading to the accumulation of genetic mutations. Genes like
BRCA1 and BRCA2 are important for DNA repair, and mutations in these genes can increase the risk of cancer.
What Are the Hallmarks of Cancer?
In their seminal paper, researchers Hanahan and Weinberg described the "hallmarks of cancer," which are essential traits that cancer cells acquire during tumor development:
1.
Sustaining Proliferative Signaling: Cancer cells can continuously signal themselves to divide, often through mutations in growth factor pathways.
2.
Evading Growth Suppressors: Tumor suppressor genes like
p53 are often inactivated, removing the brakes on cell division.
3.
Resisting Cell Death: Cancer cells evade apoptosis, allowing them to survive longer.
4.
Enabling Replicative Immortality: Telomeres, protective caps on chromosomes, are maintained by cancer cells to avoid aging and death.
5.
Inducing Angiogenesis: Tumors promote the growth of new blood vessels to supply nutrients.
6.
Activating Invasion and Metastasis: Cancer cells gain the ability to migrate and spread to other parts of the body.
What Are the Implications for Treatment?
Understanding the biological processes involved in cancer is crucial for developing effective treatments. Targeted therapies are designed to interfere with specific molecules involved in cancer growth and progression. For example,
HER2 inhibitors target the HER2 protein in certain breast cancers, while PARP inhibitors are used for cancers with defects in DNA repair mechanisms.
Additionally, immunotherapy has emerged as a powerful treatment modality. By harnessing the body's immune system to recognize and destroy cancer cells, therapies like checkpoint inhibitors can provide durable responses in some patients.
Conclusion
Cancer is a complex disease involving numerous biological processes that are essential for its development and progression. By understanding these processes, researchers and clinicians can develop more targeted and effective treatments, ultimately improving outcomes for patients with cancer.
