Cancer Causes and Risk Factors

Cancer: Causes and Risk Factors

• 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.

DNA Damage and Repair Mechanisms

• 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.

Risk Factors

• 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.

Viral Carcinogenesis

• 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.

Inherited Risk Factors

• 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.