-
What is cancer?
- 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
-
Neoplasia
Abnormal cell growth
Benign- slow growth, non-invasive, no metastasis (spread)
Malignant- rapid growth, invasive, potential metastasis
Benign tumors can become malignant
-
-
How do cancer cells gain this autonomy?
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)
-
Two requirements for cells to become cancerous
- Mutation affecting genes that induce cell division
- Mutation affecting genes that suppress cell division
" their accelerators must get stuck and their breaks must fail"
-
Target Genes
- 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
-
-
-
The Six Halmarks of Cancer
- 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
-
What is tumor angiogenesis?
-
-
Successive Rounds of Mutation
- 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.
-
What can cause these mutations?
- 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
-
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
-
Genes, Lifestyle, & Environment
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 Therapies
- 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
-
Chemotherapy (Cytotoxics)
- Use of chemicals to kill rapidly dividing cells
- -like cancer cells
- but also can affect normal tissue
- -bone marrow, digestive tract, hair follicles
-
Chemotherapy
- 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
-
Chemotherapy Efficacy
- 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.
-
Targeted Therapies
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
-
Types of Targeted Therapies
- 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
-
Reducing Your Risk
- 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
|
|