Cancer Biology Quiz

Cancer Definition and Types

• Cancer is a defect in mechanisms controlling cell survival, proliferation, and death.

Neoplasms (Tumors)

• Abnormal mass of tissue due to abnormal cell growth.

Leukemia

• A blood cancer that doesn't form a tumor.
• Widely spread in the bloodstream and bone marrow.

Causes of Cancer

• Environmental Factors
  • Ionizing radiation
  • Chemical carcinogens (e.g., tobacco smoke, alcohols, and asbestos)
• Chronic Infections (Viruses)
  • Hepatitis B and C are associated with Hepatocellular Carcinoma (HCC)
  • HIV is associated with certain types of lymphomas
  • Retroviruses (e.g., HIV) can transform bcl-2 → oncogene → uncontrolled cell growth and inhibition of cell apoptosis
• Genetic Factors
  • Mutation in tumor suppressor genes
  • Genes that suppress malignant cell growth (e.g., p53 gene mutation associated with various solid tumors)
• Lifestyle Factors
  • Unbalanced diet
  • Hormones

Pharmacology in Neonates

• Newborns exposed to caffeine during gestation have higher levels of CYP1A2 activity at birth, resulting in a shorter caffeine half-life of 4-5 hours, necessitating more frequent dosing.

Drug Metabolism

• Phase II: Lower UDP-glucuronosyl transferase (UGT) activity affects the metabolism of morphine, chloramphenicol, and acetaminophen.
• Phase I: Lower CYP3A4 activity leads to a slower rate of erythromycin metabolism, increasing the risk of adverse effects.
• Phase I: Genetic polymorphisms of CYP2D6 result in lower activity, affecting the metabolism of atomoxetine, leading to increased heart rate, blood pressure, and impaired weight gain in children with ADHD.
• Phase I: CYP1A2 activity is negligible in fetal liver tissue and in newborns not exposed to caffeine in utero.

Drug Elimination

• Kidneys are not fully developed at birth, resulting in lower GFR, immature tubular secretion, and decreased clearance of aminoglycosides and digoxin.
• Concomitant use of dexamethasone and indomethacin may alter the normal progress of renal maturation in neonates.

Pharmacodynamic Changes

• Reduction in adrenergic receptor density or downregulation of receptors in the myocardium of premature neonates, making them resistant to the effects of β-adrenergic agonists.
• GABA receptors are abnormal in infancy and develop with age, explaining why infants require relatively larger doses of anti-epileptic medications.

Drug Distribution

• Functionally immature blood-brain barrier, resulting in higher drug distribution into the CNS, making antibiotic therapy for sepsis and meningitis more effective.
• Higher total body water, leading to greater distribution of highly water-soluble drugs like linezolid and gentamicin.
• Plasma protein binding is reduced in neonates due to decreased circulating levels of albumin and decreased binding affinity, affecting the distribution of phenytoin and sulfonamides.

Drug Absorption

• Intramuscular & Subcutaneous Absorption:
  • Reduced muscle size, weaker muscle contractions, immature vasculature, and reduced skeletal muscle blood flow, leading to reduced absorption of I.M administered drugs in neonates.
  • Lower percentage of body fat in neonates, delaying subcutaneous drug absorption (e.g., insulin).
• Transdermal Absorption:
  • Greater skin to body surface area ratio, thinner epidermis, better hydration, and greater perfusion, enhancing skin absorption and increasing the risk of significant toxicity.
• Rectal Absorption:
  • High contractions in the rectum causing premature expulsion of solid rectal drug formulations (suppositories).
  • Rapid absorption of rectal solutions of drugs like diazepam gel.
  • Rapid absorption of rectal acetaminophen suppositories.