What is Cancer Flashcards
Define cancer
uncontrolled growth of abnormal cells in a tissue, invasive and spreading
which tissues do the majority of tumours arise from
epithelial tissue
what type of cells are epithelial tumours
Squamous cell carcinomas (epithelial tissues) and adenocarcinomas (organs/glands)
two types of tumours
- benign
- malignant (spread)
What are 4 other tumours that arise from non-epithelial cells
- Sarcomas
- Leukemias (Lymphoid and myeloid)
- Nueroectodermal tumours
- Brain Tumours
what types of body cells does cancer occur in
- mutations causing cancer occur in germline and in somatic cells
- cancer is a genetic disease
how does cancer begin and develop (cellular level)
mutations in cells → microevolution process (leads to accumulation of 5-10 critical mutations - requires many years)
what types of genes do mutations usually occur in
genes controlling:
- Cell growth and division
- Genome integrity and DNA repair
- (apoptosis) Programmed cell death
- The cell cycle
- Stem cell-like properties (stemness)
What are the 3 main ways mutation arises
- Copying errors occur during DNA replication
- Spontaneous depurination → chemical changes (results in damage to DNA)
- Exposure to different agents (ionising radiation, UV light, Tobacco)
what are monoclonal vs polyclonal tumours
- monoclonal: mutation occurs in just one cell and it proceeds to produce clones
- polyclonal: where the mutations take place in many different cells in the tissue and they all transform from normal to malignant cells
is cancer a monoclonal or polyclonal growth
- Monoclonal
What is the evidence for cancer being a monoclonal growth
In females, one X chromosome is randomly inactivated in each cell early in development.
Some X-linked genes (like G6PD) are polymorphic, and heterozygous individuals have both maternal and paternal alleles.
In tumour cells from such individuals, only one isotype of G6PD is found across all tumour cells.
This shows the tumour originated from a single cell, proving cancer is monoclonal in origin.
how is cancer heterogenous
cancer quickly becomes heterogeneous due to genetic instability of cancer cells masking monoclonal origin of this cell population
describe how cancer is a progressive disease
IDKKKK
what are tumour suppressor genes (protein)
- These are genes/proteins that control cell growth.
- Normal function: negative regulator of cell growth (prevents cell growth)
- even protein from one of the two alleles is enough (a cell needs to lose function in both alleles to lose the suppressor effect and therefore allow for tumour progression.
what are oncogenes
- These are Positive regulator of cell growth (makes cells grow).
- They are found in normal cells but are under strict regulation.
- However when there are mutations or epigenetic changes then they become oncogenes and they promote cancer (can cause problems even when only one allele is mutated)
what are the hallmarks of cancer, how many are there
- The acquired ability of tumour cells to have an advantage over surrounding cells and thus help them to progress, and metastasise
- There were 6 original hallmarks (circled in red) but then 2 more were added after further research (circled in green) and 2 enabling characteristics (circled in blue).
What is the mnemonic to remember the 8 hallmarks of cancer?
Some Evil Rats Eat Incredibly Amazing Donuts Always
Sustaining Proliferative Signalling
Evading growth suppressors
Resisting Cell death
Enabling replicative immortality
Inducing angiogenesis
Activating tissue invasion and metastasis
Deregulating Cellular energetics
Avoiding Immune destruction
what is hallmark 1
Sustaining Proliferative Signaling
describe hallmark 1’s mechanism
Hallmark 1 involves cancer cells gaining the ability to proliferate independently of external signals. They make 3 main alterations to achieve this:
1. Autocrine signaling: Cancer cells produce their own growth factors (GFs) and signal themselves to keep growing.
2. Constitutively active receptors: Mutations in growth factor receptors make them always active, so they don’t need external signals to trigger cell division.
3. Altered intracellular circuits: Signaling pathways inside the cell become constantly activated, enabling the cell to maintain growth-promoting signals even without external stimulation.
what is hallmark 2
Evading Growth Suppressors
describe hallmark 2’s mechanism
- pRb regulates the cell’s restriction-point gate and makes the decision on if the cell should move into the active cycle or not depending on the level of phosphorylation of pRb.
- In many tumours pRb is mutated meaning a loss of control over the progression between G1 and S phases –> Tumours don’t rely on decisions they just go through.
what is hallmark 3
Resisting Cell Death (Apoptosis)
What is the normal mechanism that would occur without hallmark
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