Chapter 10-cancer epidemiology

Question 0

Epigenetics

Answer 0

• epigenetic changes collaborate with genetic changes and environmental factors to cause the development cancer
• 3 types of epigenetic changes
  
  • 1: methylation (the addition of a methyl group [CH3] to the cytosine ring);aberrant methylation can lead to silencing of tumor suppressor genes
  • 2: Histone modifications: (histone acetylation, alterations in chromatin) can result in gene silencing
  • 3: Micro-ribonucleic acids (miRNA’s) are small RNA molecules that can target gene expression post-transcriptionally. MicroRNA’s act like a volume control lever to modulate the production of defined proteins in cells. The expression of miRNA’s has been linked to carcinogenesis because they act as either oncogenes or tumor suppressing genes
• epigenetic process can be modified by lifestyle, diet, environment, pharmacological interventions
• environmental factors can alter the epigenome
• transgenerational inheritance: heritable transmission to future generations of environmentally-caused phenotypes
• transgenerational effects: an alteration in germline cells (sex gametes)
• biologically active food components modify DNA methylation directly

Question 1

Cancer risk factors-objective 1

Answer 1

• cigarette smoking/tobacco exposure: linked to cancer of the lower urinary tract (bladder, penis, and renal), upper aerodigestive tract (oral cavity, pharynx, larynx, nasal cavity, paranasal sinuses, esophagus, and stomach), liver, kidney, pancreas, cervix, uterus, and myeloid leukemia
• non-smokers who live w/smokers are at greatest risk for lung cancer as well as numerous noncancerous conditions
• ionizing radiation exposure
• UV radiation: causes basal cell carcinoma (head/neck of individuals with light complexions, light eyes, & fair hair) and squamous cell carcinoma (men who work outdoors, head and neck of exposed areas of upper extremities. Melanoma (most dangerous type of skin cancer)
• excessive alcohol consumption: liver of alcoholics is fatty
  
  • esophageal cancer
  • stomach cancer
  • mouth cancer
• poor diet which can lead to obesity and diabetes: cancer producing agents in the diet
• lack of exercise
• sexual behavior that increases exposure to certain viruses
• hormones
• medical drugs
• viruses:
  
  • HIV: only people who have moved onto AIDS develop Kaposi’s sarcoma. This is indication of AIDS in the pt that has not been diagonosed
  • Epstein Barr virus (EBV): Burkitt’s lyymphoma
  • HPV human papilloma virus: squamos cell carcinomas- >cervical cancer
  • Heptatitis B hepatocellular carcinoma
  • Herpes simplex:genital cancer, typically cervical cancer
• Bacteria: Helicobactor pylori: (chronic untreated or undertreated)
  
  • peptic ulcer disease: constant irritation (prematre cell death, cell hyperplasia leading to cancer)
  • gastric lymphomas
  • gastric carcinomas
• pesticides
• environmental chemicals present in air, water, food, soil, & workplace
• genetic predispositions
• age: more exposure, body has also been making cells for a while, the change of making dysfunctional cells increase
• immunity: defects in the immune system increases the incidence of lymphomas, herpes virus causes cancers, HPV cancer but little or no increase in organ cancers

Question 2

Radiation-risk factor for cancer

Answer 2

• ionizing radiation is a mutagen and carcinogen and can penetrate cells and tissues and deposit energy in tissues at random in the form of ionizations (excitation or removal of an electron from the target atom)
• this can lead to irreversible or indirect damage from formation and attack by water-based free-radicals (radiolysis)
• it affects many cell processes->gene expression, disruption of mitochondrial function, cell cycle arrest, and cell death
• it is a potent DNA damaging agent causing cross-linking, nucleotide base damage, and single-and double strand breaks–> damage to DNA and disrupted cellular regulation processes can lead to carcinogenesis

Question 3

Genomic instability

Question 4

Xenobiotics

Answer 4

• include toxic, mutagenic, and carcinogenic chemicals, many found in human diet
• they are transported in the blood by lipoproteins and penetrate lipid membranes
• dietary sources include compounds produced in cooking of fat, meat, or protein, and naturally occurring carcinogens associated with plant food substances, such as alkaloids or mold byproducts
• dietary components can act directly as mutagens or interfere with mutagen elimination
• nutritional factors ma alter cellular environments by modulating hormonal axes or influencing cellular proliferation

Question 5

Obesity associated cancer risks

Answer 5

• may vary by type of tumor and distribution of body fat
• abdominal obesity has been shown to be more strongly related to some tumor types than obesity defined by BMI
• may include: insulin resistance, hyperinsulinemia, increased insulin-like growth factors, increased steroid hormones, increased tissue derived hormones, and cytokines or inflammatory mediators

Question 6

Ionizing Radiation

Answer 6

• it is a mutagen and carcninogen and can penetrate cells and tissues and deposit energy in tissues at random in the formation of ionizations
• this can lead to irreversible or indirect damage from the formation and attack by water-based free radicals or radiolysis
• it affects many cell processes, including gene expression, a disruption of mitochondrial function, cell cycle arrest, and cell death
• IR is a potent DNA-damaging agent causing cross linking, nucleotide base damage, and single-and double-strand breaks
• DNA damage disrupted cellular regulation processes can lead to carcinogenesis
• double strand break is considered the characteristic lesion observed for the effects of IR