Cancer Causes and Risk Factors

Study Notes

Cancer arises from mutations, tipping the balance towards uncontrolled cell proliferation.
Proto-oncogenes promote cell growth, while tumor suppressor genes inhibit it.
Age is the leading risk factor for cancer, with incidence increasing with age.
Lifestyle choices significantly impact cancer risk.
Diet: Unhealthy diets (high in processed and red meat, low in fiber and fruits/vegetables) can increase the risk of several cancers (e.g., bowel, mouth, throat, lung).
Alcohol consumption is linked to several cancers (e.g., mouth, throat, esophagus, breast, liver, bowel).
Alcohol is converted to acetaldehyde, which damages the liver and other organs.
Tobacco use, overweight/obesity, UV radiation, certain infections, and occupational exposures are also major risk factors.
DNA damage is a key driver of cancer, originating from various sources like replication errors, reactive oxygen species, and environmental mutagens.
DNA repair mechanisms (e.g., nucleotide excision repair) attempt to fix these damages.
Environmental factors (e.g., air pollution, occupational exposure, natural products) can cause mutations leading to cancer.
Infections, like HPV, HBV, HCV, and EBV, are linked to various types of cancer.

Replication stress, reactive oxygen species and nitrogen species, ionizing radiation, chemotherapeutics, UV light, and polycyclic aromatic hydrocarbons are common causes of DNA damage.
DNA repair mechanisms (e.g., mismatch repair, base excision repair, homologous recombination, and non-homologous end joining) attempt to correct this damage.
Some DNA repair mechanisms are deficient in individuals with inherited genetic traits, increasing their susceptibility to cancer.

Tobacco use is strongly linked to lung cancer risk, and other cancers as well.
Unhealthy diets and obesity are linked to various types of cancer.
UV radiation significantly increases the risk of skin cancer.
Certain infections (e.g., HPV, HCV, HBV, EBV) increase the risk for specific cancers.
Specific occupational exposures can increase cancer risk.
Alcohol consumption is linked to a range of cancers.
Inadequate fiber intake might increase bowel cancer risk.

Certain viruses (e.g., HBV, HCV, HPV, EBV) are implicated in causing cancers.
Some viruses integrate their DNA into the host cell's genome, which can lead to uncontrolled cell growth.
Chronic infections can damage DNA and potentially contribute to cancer.

Some inherited genetic mutations (e.g., BRCA1/2) increase the susceptibility to certain cancers like breast, ovarian, and prostate cancer.
Inherited mutations can affect DNA repair mechanisms, impacting the body’s capacity to correct DNA damage, making individuals more prone to cancer.
Familial cancer syndromes, like Lynch syndrome and Li-Fraumeni syndrome, are characterized by inherited genes that increase the risk of various cancers.