Lecture24: Cancer I Flashcards
What is the deadliest form of cancer
Lung cancer
What is Cancer
A disease in which an individual mutant clone of cells begin by prospering at the expense of its neighbor cells
Properties of cancer cells
- Cells growing out of control
- Become self-sustaining
- do not need signals ot grow
- Release autocrine growth factor signals
- These cells should stop growing with anti-growth signals- but cancer cells ignore them
- Cancer cells ignore apoptosis signals
Normal vs. Cancer cells
- Cancer cells require little growth factors
- Normal cells have strong requirement
- Cancer cells become independent of stimulation that is normally required by cells to proliferate
- Cancer cells have decontrolled proliferation
What are the two heritable properties of cancer
- Reproduce in defiance of normal restraints on cell division and cell growth
- Invade areas normally reserved for other cells
a tumor is considered cancer if it is
malignant (ability to invade surrounding tissues)
An abnormal cell that grows (increases in mass) and proliferates (divides) out of control will give rise to a
tumor or neoplastic growth
Classification of cancers
- Carcinomas:
- From epithelial cells (most common)
- Sarcomas:
- From Connective tissue and muscle tissue
- Leukemias and Lymphomas:
- From white blood cells and their precursors
Adenoma
- Adenoma
- benign epithelial tumor with glandular organization
- (note a malignant tumor of the same type is adenocarcinoma)
Basal cell carcinoma
Cancer of keratinocyte stem cell in skin
Melanoma
cancer of pigment cells in skin
What is more likely to metastasize Basal-cell carcinoma or malignant melonomas
Basal-cell carcinomas rarely metastasize whereas malignant melonomas metastasize widely
What is Metastases
- Invasiveness is property of cancer
- Cancer cells can break loose, enter into blood or lymph, travel to new areas and form secondary tumors
Development of Colon Cancer
- Mutation in APC gene (tumor suppressor)
- Cells with APC mutation gain an advantage in growth
- Form polyps
- at this stage the tumor is a benign tumor
- mutation in Ras- becomes a cancer gene
- lose p53 (a tumor suppressor )
- Tumor moves out into blood stream
- Gains capacity to invade
- is now a malignant tumor
Do cancer arise form a single heritable cell
- Yes
- (evidence of this is found in the philadelphia chromosome)
Philadelphia chromosome
- Translocation between chromosome 9 + 22
- Responsible for chronic myelogenous leukemia
What are two types of carcinogens
- Chemical carcinogens
- Radiation (x-rays, UV)
What is the best weapon against cancer
early detection
What is angiogenesis
Formation of new blood vessels from pre-existing blood vessels
What is neovascularization
Formation of new blood vessels basically from scratch
High fat/low fiber accounts for ___ % of bowel, pancreas, prostate and breast cancer
37%
HIV causes ____ sarcoma
Kaposi’s sarcoma
Genes whose alteration frequently results in cancer
Cancer critical genes
What are the two broad types of mutations in cancer
- Overactivity mutations
- Gain of function
-
oncogenes
- involves single mutaiton event and activation of gene causing proliferation (dominant)
- Underactivity mutations
- loss of function
-
Tumor suppressor genes
- involve genes that inhibit growth
Genetic causes of cancer
- Mutations of genes that regulate cell proliferation
- overactivity/ gain of function mutation
- Oncogenes
- Underactivity/loss of function mutation
- Tumor suppressor genes
- overactivity/ gain of function mutation
- Mutation event:
- one gene= no effect
- second mutaiton causes problems (thus is recessive)
What is the third group of genes responsible for cancer
- DNA maintenance genes
- subset of tumor suppressor genes
- Mutations involve inactivation of caretaker genes that create genomic stability
- include DNA repair genes, checkpoint genes
What is the first human oncogene
Ras
What is Ras
- Ras is monomeric GTPase for signal transduction
Ras oncogenes
cannot shut off by hydrolyzing GTP to GDP (this is similar to cholera)
Activation of proto-oncogenes
- Proto-oncogenes, when activated or overexpressed, can become oncogenes to drive cell proliferation
Bcl2 oncogenes
- Bcl2 (promotes survival despite DNA damage)
- overproduction allows cancerous cells to survive and grow
- In cancer cells Bcl2 locus on Chr 18 undergoes a reciprocal translocation with part of Chr 14 gene
- example of rearrangement mutation
