Cancer Biology

• Unrestrained division of cells
• -failure of the cell cycle
• -normal cells respond to signals that dictate whether to divide
• *cancer cells become autonomous from such signals

Abnormal cell growth

Benign- slow growth, non-invasive, no metastasis (spread)

Malignant- rapid growth, invasive, potential metastasis

Benign tumors can become malignant

Normal cells become cancerous through mutations to a cell's genome

• Generally from an accumulation of mutations
• -produce proteins that disrupt cell cycle
• -why cancer mostly affects midle-aged to elderly
• -mutations usually somatic (not heritable)

• Mutation affecting genes that induce cell division
• Mutation affecting genes that suppress cell division

"their accelerators must get stuck and their breaks must fail"

• Oncogenes
• -Normally induce cell division
• -When mutated, can cause cancer by being stuck "on"
• example: RAS

• Tumor Suppressor Genes
• -Normally suppress cell division
• -when mutated, can cause cancer by being stuck "off"
• example: p53

• Immortality
• -Continuous cell division & limitless replication

• Produce "Go" Signals
• -Growth factors & oncogenes

• Override "stop" signals
• -Anti-growth signals from tumor suppressor genes

• Resist Cell Death
• -Apoptosis

• Angiogensis
• -New blood vessel growth into cell

• Metastasis
• -Spread to other sites

• Cancer is a multi-gene, multi-step disease
• -from an orignal abnormal cell (clonal origin)
• -Accumulation of mutations result in progression from a mildly unusual cell to a tumor
• -tumor cells can further mutate and become malignant
• -Death from cancer generally from spread/invasion of malignant cells into normal tissue.

• Viruses
• -ex: HPV & Cervical cancer

• Bacteria
• -ex: H. pylori & stomach cancer

• Chemicals
• -ex: B[a]P (in coal tar) & lung cancer

• UV & Ionizing Radiation
• -ex: Skin cancer

these agents are all considered mutagens

• Can change an organism's DNA
• -exposure therefore increases mutation frequency

• Viruses: insertional mutation
• Chemicals: Bind to DNA
• Radiation: Breaks DNA strands

Carcinogen: directly involved in causing cancer

Cancer is a complex disease: no single cause

• Lots of risk factors:
• tobacco use
• alcohol consumption
• age
• genetic makeup & family history
• diet & physical activity
• exposure to infectious agents
• exposure to pollutants/toxins
• AND SEVERAL MORE

• Cancer is a systemic (whole body) disease
• -50% of patients experience metastasis

• Systemic therapy: distributed throughout body
• -normal and cancerous tissues
• EX: drug therapy (chemo)

• Local therapy: directed toward certain area
• EX: radiation, surgery

• ideal treatment
• -effective
• -tumor-specific
• -minimal toxicity

• Use of chemicals to kill rapidly dividing cells
• -like cancer cells
• but also can affect normal tissue
• -bone marrow, digestive tract, hair follicles

• Administration of chemotherapy
• -injected into veins, muscle, or tumor
• -or taken in pill form

• Toxicity effects
• -range from acute to long-term (chronic)
• *Nausea & vomiting
• *alopecia (hair loss)
• *Neurotoxicity
• *renal, cardiac, pulmonary, etc. toxicity
• *sterility

Some find chemo controversial due to the permanent damage it can cause

• Some cancers respond better than others
• -Testicular: 70-90% cure rate
• -Significantly prolongs patient life in others: leukemia in children, ovarian, colon
• -Depends heavily on how early cancer is detected.

Often in conjunction with chemotherapy

Several focus on molecular/genetic changes in cancer cells & tries to target them

• -Protein products specific to cancer cells
• -Cell components important to maintaining malignancy

• Radiation: ionizing radiation waves aimed at tumor
• -Cancer cells more sensitive to single-strand breaks in DNA

• Hormonal therapies for cancers of areas highly regulated by hormones
• -ex: breast & prostate cancers
• -to decrease cell growth & induce apoptosis

• Non-modifiable risk factors exist, but you can reduce your risk of cancer (or prolong getting it)
• -avoid tabacco use
• -avoid or limit alcohol consumption
• -protect yourself from the sun
• -avoid behaviors that will put you at risk of contraciting certain viruses/bacteria
• -consult doctors about any hormonal supplements
• -know your family history & get yourself examined often
• -maintain good physical health