Cancer: Causes, Risk Factors & DNA Damage

Study Notes

Cancer arises from mutations, disrupting normal cell proliferation. Proto-oncogenes promote cell growth, while tumor suppressor genes inhibit it. Mutations tip the balance towards uncontrolled growth.
Age is the primary risk factor for cancer. Incidence rates increase significantly with age.
Lifestyle choices heavily influence cancer risk. Unhealthy diets, lack of physical activity, and smoking contribute significantly to cancer development. Specific dietary factors, like processed and red meat, increase bowel cancer risk, while fiber and fruit/vegetables are protective. Alcohol is linked to several cancers.

DNA damage from various sources like replication errors, reactive oxygen species, UV light, and chemicals (like benzo[a]pyrene from tobacco smoke) initiates cancer.
Specialized DNA repair mechanisms attempt to fix these damages. Failure in these mechanisms leads to mutations that drive cancer development. Specific examples of repair mechanisms highlighted include: Homologous Recombination, Non-Homologous End Joining, Base Excision Repair, and Nucleotide Excision Repair
Tobacco use, obesity, UV radiation, certain infections, and insufficient fiber are amongst numerous recognized risk factors for cancer.

UV light, particularly UVB and UVA, can damage DNA, leading to skin cancer. The ozone layer protects against damaging UVC light.
Environmental mutagens like occupational chemicals, natural products (e.g., aflatoxin), and medical mutagens (e.g., chemotherapy and atmospheric particles) contribute to cancer development.

Certain viruses (e.g., Hepatitis B and C viruses, HPV, Epstein-Barr virus) can increase cancer risk. These viruses' integration into host DNA or chronic infections can cause genetic instability and loss of tumor suppressor genes.

Infections are linked to a substantial portion of cancers. Specific examples highlighted include human papillomavirus (HPV), hepatitis B and C viruses, and Epstein-Barr virus (EBV).

Some cancers are associated with inherited mutations in genes like BRCA1/2. Mutations in these genes impair DNA repair mechanisms, increasing susceptibility to cancer. Other inherited cancer risks highlighted include Lynch syndrome, Li-Fraumeni syndrome, PTEN Hamartoma tumour syndrome, and Von Hippel Lindau Syndrome.