Lecture 10: Cancer Flashcards
Define neoplasm.
Abnormal mass of tissue produced when cells divide more than they should or do not die when they should.
AKA the tissue/cell is lacking its normal regulatory control.
Define neoplasia.
Process of formation of an abnormal growth.
Define proliferation.
The process by which cells divide and reproduce.
What are the two ways by which cells proliferate?
Meiosis and Mitosis
What mediates cell proliferation?
Gene expression, growth factors, and signaling molecules.
What is the specific kinase that regulates cell division?
mTOR, which also changes depending on local nutrition.
Define differentiation.
The process by which cells are transformed into different and more specialized cells.
What causes a cell to be differentiated?
Gene expression.
Influenced by growth factors and other stimuli
As a cell becomes MORE specialized, is it more or less likely to divide?
Less likely!
Important!!!!!!!!
What are stem cells?
Highly undifferentiated cells with SELF-RENEWAL
They have the potential to divide into multiple types of cells, which will eventually become fully differentiated cells.
What is a progenitor/parent cell? Why is it distinct from a stem cell?
It is still a cell that can divide, BUT parent cells have only a few options to differentiate into.
What are the 5 types of stem cells from most undifferentiated to most differentiated?
Totipotent: ALL CELL TYPES (AKA TOTAL RANGE)
Pluripotent: all adult cell types (PLENTY)
Multipotent: MULTIPLE cell types
Oligopotent: FEW cell types (Oligo means few/scanty)
Unipotent: ONE cell type
What are most progenitor cells in terms of stem cell ranking?
Oligopotent or unipotent.
Define carcinogenesis.
Origin and development of cancerous neoplasms
What kind of cells are most susceptible to neoplasia?
Rapidly dividing, labile cells
What percentage of cancers develop post birth?
95%
Define oncogenesis.
The mechanism by which normal cells BECOME cancer cells.
What is monoclonal origin?
The concept of cancer originating from a single cell with genetic mutations.
What 3 genes are responsible for making sure our cells do NOT develop into cancer?
Mutator genes
Protooncogenes
Tumor suppressor genes.
Define mutator genes.
They help repair mutated DNA and protect our genome.
The repair typically happens POST environmental insult.
Note: We have multiple mutator genes, so it is the failure of MULTIPLE that leads to us accumulating mutations and thus cancer.
Define protooncogenes.
Promote cell growth and development.
Specifically, they are normal genes that code for the proteins that regulate cell growth and differentiation, BUT they can become oncogenes.
Define tumor suppressor gene.
Control apoptosis, regulate cell division.
This is designed to ensure we have the optimal number of cells in our body. Therefore, failure of this gene = uncontrolled cell division = endless growth.
Does a single gene mutation usually cause cancer?
No!
What are the 3 tumor suppressor genes discussed in class? How are they distinct from each other?
TP53 (p53 protein) is found on chromosome 17.
It is often implicated in many colon, lung, and breast cancers.
Regulates apoptosis of CANCER cells post chemo/radiation.
RB Gene (Rb protein) is the first tumor suppressor gene ever discovered.
Associated with retinoblastoma and other cancers.
BCL2 gene (Bcl-2 protein) regulates apoptosis.
Mutation results in a POORER response to cancer therapy.
Often associated with leukemia and other cancers.
What is the two-hit hypothesis?
Example: Retinoblastoma.
Even if a child carries the susceptibility gene for retinoblastoma, that is only 1 of the 2 chromosomes.
The susceptible child needs just 1 mutation to get retinoblastoma.
However, for someone not born with the gene, they need 2 individual mutations to get retinoblastoma, hence two-hit.
Note: See slide 19 for a visual.
How do protooncogenes mutate? What do they become?
They become oncogenes via 3 methods:
Point mutation: damage of a single nucleotide pair (usually spontaneous or from environment)
Chromosomal translocation: chromosome breaks, relocates, and unites with another chromosome.
Gene amplification: accelerating replication of genes, leading to overproduction of proteins associated with that gene.
Define oncogenes.
Genes that promote UNregulated cell growth and development, inhibit cell death.
They encode growth factors to promote cell division.
Disturbing cell surface receptors and cell-to-cell communication.
Encoding proteins to alter cell cycle, restrict apoptosis, and impact differentiation.
How do I name an oncogene?
Viral ones = v, like v-src
Cellular ones = c, like c-neu
What are some general types of genetic mutations for chromosomes?
Duplication, Inversion, Deletion, Insertion, Translocation.
See slide 22 for visual.
What two events are required for a tumor to be called cancer?
Initiating event
Promoting event
Define initiating event and what cells are most susceptible.
Initiating events are the event that causes a mutation in a cell. This is usually caused by a carcinogenic agent or a sporadic mutation.
The cells most susceptible are the ones actively synthesizing.
Define promoting event and a common cause.
It is the event that causes the cell to actively grow and reproduce more.
Most commonly caused by chronic inflammation.
Also, complete carcinogens can do both initiation and promotion of neoplastic transformation.
Define Progression in terms of cancer.
Extension of promotion phase.
Important:
Cell no longer requires the promoter to be present AND
Cell acquires ability to invade tissue, metastasize, and grow autonomously.
Why is a functional immune response essential to prevent cancer?
A functional immune response allows us to fight many cancers, because most cancers express abnormal HLA-1 antigens that our body can still recognize and defeat.
Immunosuppressed patients have higher rates of cancer as a result.
What are the host factors that affect cancer susceptibility?
Immunologic response
Age
Chronic Inflammation
Genetic Predisposition
Genetic Disease
Hormones
Why does growing old make you more susceptible to cancer?
Older people have accumulated more mutations/DNA damage.
Increased methylation of genes, which turns them OFF.
Weaker immune responses overall.
Why does having chronic inflammation make you more susceptible to cancer?
During chronic inflammation, we have higher numbers of phagocytes floating around eating cells, but they can also damage other healthy cells while protecting us.
Inflammation also = cell proliferation, increased growth factor, more angiogenesis, increased nutrients and oxygen, increased ability to grow due to tissue remodeling.
When we say someone is predisposed to cancer, what do we mean?
Most common is that they probably have something like BRCA1 and/or BRCA2, which are tumor suppressor genes that greatly increase the risk of contracting breast and/or ovarian cancer.
It also includes more general INHERITED factors, such as:
Inefficient breakdown and disposal of carcinogens
Altered ability for DNA repair
Impaired cell proliferation and differentiation
Which BRCA gene results in higher incidences of breast/ovarian cancer?
BRCA1, which has a 55-65% breast cancer rate, 39% ovarian.