Oncology Flashcards
Define cancer (2 points)
Cancer – abnormal cells divide in an uncontrolled way; some cancers may eventually spread into other tissues.
List 7 risk factors for cancer
Risk factors for cancer:
- Smoking
- Excess alcohol intake
- Carcinogenic diet
- Excess sunlight
- Physical inactivity
- Chronic infection
- Genetic predisposition
Recall the cell cycle
The cell cycle:
- How a cell grows and divides – ‘life cycle’
- Interphase:
- Growth of cell, no division (includes G1, S, G2)
- Cells in this phase most of time
- Except cancer cells (division)
- G1: duplicate cell contents (e.g. organelles)
- S: duplicate chromosomes (23 to 46 pairs)
- G2: prepare for mitosis
- G0: no cell division (e.g. neurones)
- Mitosis: active cell division (cytokinesis)
List the two classes of molecule which regulate the cell cycle
Two classes of molecule regulate the cell cycle through various checkpoints:
- Cyclins (Cyc)
- Specific Cyc are made at specific times.
- Cyclin-dependent kinases (CDKs)
- Inactive CDKs always present in cell, activated by Cyc
List the 3 cell cycle checkpoints
Cell cycle checkpoints (3 points):
- M checkpoint
- G1 checkpoint
- G2 checkpoint
Describe positive cell cycle regulation
Positive regulation at internal checkpoints (allows for progression):
- The cell progresses through the cell cycle regulated through various checkpoints:
- Cyclins (Cyc)
- Cyclin-dependant kinases (CDKs)
Describe negative regulation of the cell cycle at G1 checkpoint
Negative regulation of the cell cycle (prevents progression from G1 phase to S phase):
- At G1 checkpoint:
- Tumour suppressor genes control the cell cycle
- Retinoblastoma protein (pRb) normally bound to E2F transcription factors
- When phosphorylated, pRb releases E2F transcription factors which bind to DNA and regulate expression of S phase proteins → progress to S phase
- When unphosphorylated, pRb remains bound to E2F transcription factors → halts progress to S phase
- Therefore, pRb is able to halt cell cycle if conditions are unfavourable (i.e. potential cancer).
Describe the role of tumour suppressor genes (5 points)
Tumour suppressor genes control the cell cycle, p53 (“guardian of the genome”):
- Activated p53 binds to DNA directly, leading to downstream activation of p21
- p21 complexes to CDK2, inhibiting it
- This prevents cell continuing onto cell division
- Mutated p53 → means p21 not available to halt cell division → cancer
- Mutated p53 is in > 50% human cancers.
List 7 types of cancer cell
Types of cancer cells (7 points):
- Carcinoma
- Sarcoma
- Leukaemia
- Lymphoma and myeloma
- Brain and spinal cord (CNS)
- Mixed tumours
- Teratoma
Describe carcinoma and list 4 types
Carcinoma – originates in epithelial tissues (85% of UK cancers):
“Some Apples Taste Bad”
- Squamous cell carcinoma
- Adenocarcenoma
- Transitional cell carcinoma
- Basal cell carinoma
Describe sarcoma and list 2 types
Sarcoma – originates in connective tissues e.g. bones, cartilage, tendons, and muscles (1% of UK cancers):
- Bone sarcoma
- Soft tissue sarcoma
Describe leukaemia
Leukaemia – originates in blood-forming tissues, bone marrow (3% of UK cancers)
Describe lymphoma and myeloma
Lymphoma and myeloma – cancers of the lymphatic system (5% lymphoma and 1% myeloma)
Describe cancer of the central nervous system and name one type
Central nervous system cancers – originate in the cells of the brain or spinal cord (3% of UK cancers):
- Glioma
Describe mixed tumours and list 2 types
Mixed tumours – both epithelial and connective tissue components:
- Carcinosarcoma
- Pleomorphic adenoma
Describe teratoma
Teratoma – originates in the germ cells:
Recall the hallmarks of cancer (10 points)
Hallmarks of cancer are acquired functional capabilities that allow cancer cells to:
- Survive
- Proliferate
- Spread
These functions are acquired in different tumour types in the course of multistep tumourigenesis, via distinct mechanisms at different times (10 mechanisms; *considered in detail):
List the two main types of cancer characteristics
Characteristics of cancer are grouped into two main types:
- Emerging characteristics
- Enabling characteristics
List 2 emerging characteristics of cancer
Emerging characteristics of cancer:
- Avoiding immune destruction
- Deregulating cellular energetics
List 2 enabling characteristics of cancer
Enabling characteristics of cancer:
- Genome instability and mutation
- Tumour-promoting inflammation
Emerging characteristic of cancer
Describe how cancer cells avoid immune distruction
Avoiding immune destruction – active evasion by cancers cells from attack and elimination by immune cells (e.g. NK cells):
- Cancer immunoediting – tumour cells with downregulation or loss of MHC class I escape surveillance by cytotoxic T cells
Emerging characteristic of cancer
Describe how cancer cells derugulate cellular energetics
Deregulation of cellular energetics
Cancer cells favour aerobic glycolysis pathway over normal respiration – inefficient but fast:
- Produces a lot less ATP per glucose but they make it much faster
- Increases glucose transporters to take in more glucose
- Produces intermediate precursors for building proteins and DNA needed by rapidly dividing cells
This phenomenom is referred to as the Warburg effect
Describe the Warbug effect
The Warburg effect
Refers to the fact that cancer cells, somewhat counter intuitively, prefer fermentation as a source of energy rather than the more efficient mitochondrial pathway of oxidative phosphorylation.
Enabling characteristic of cancer
Describe genetic instability and mutation for enabling cancer
Genetic instability and mutation:
- Certain genetic mutations confer selective advantage on a subset of cells, enabling outgrowth and dominance in local tissue environment.
Compare inherited vs acquired genetic mutations found in cancers
The appearance of abnormal characteristics reflects altered patterns of gene expression in cancer cells, resulting from inherited or acquired mutations:
Enabling characteristic of cancer
Describe how inflammation can enable tumour progression (4 key points)
Tumour-promoting inflammation:
- Historically thought that immune response was only to allow body to eradicate tumour (partly true)
“Inflammation Promotes Growth & Survival”
Inflammation enables tumours by supplying bioactive molecules to environment:
- Inductive signals activate epithelial mesenchymal transition
- Proangiogenic factors and ECM modifying enzymes facilitate angiogenesis, invasion and metastasis
- Growth factors sustain proliferative signalling
- Survival factors limit cell death
Recall the targeted therapies for the 10 different hallmarks of cancer
Compare benign tumour (4 points) vs malignant tumour (4 points)
Benign – non-cancerous tumour (4 points):
- Enclosed in connective tissue
- Confined to site of origin
- May grow but does not spread to other parts of body (i.e. does not metastasize)
- May turn malignant – best to resect when noticed
Malignant – cancerous tumour (4 points):
- Not enclosed in any tissue
- Not confined to site of origin
- Grows rapidly and spreads to other body parts via blood (metastases)
- Earlier intervention tends to have better prognosis
Describe DNA point mutations and list 3 key types
DNA point mutations:
- Common types of mutations to DNA sequence include:
- Substitution (a different nucleotide is substituted)
- Insertion (the addition of a new nucleotide)
- Deletion (the loss of a nucleotide)
Point mutations because only one nucleotide is substituted, added, or deleted
-
Insertions and deletions are usually more harmful than a substitution
- Results in a frame-shift that changes the reading of subsequent codons
- Alters the entire amino acid sequence following the mutation, producing abnormal protein
List and describe 3 types of germline mutation
Germline ⇒ germline is the population of a multicellular organism’s cells that pass on their genetic material.
Germline mutations can have large or small negative effects:
-
Neutral mutations:
- Non-coding sequence of DNA (intron)
- Changes in DNA sequence but no noticeable effect on the phenotype of an organism
-
Selected mutations:
- Coding sequence of DNA (exon)
- Defective gene, abnormal protein produced
-
Mutations to control genes:
- Control genes regulate expression of other genes
- Mutation causes big change occurs in phenotype
- HOX genes germ line mutations:
- Fly – legs instead of antennae – mutation in HOM-C
- Human – microtia → mutation in HOXA2
List 7 chromosome mutations
Chromosome mutations:
- Chromosomal aneuploidy (abnormal number of chromosomes in a cell)
- Point mutations
- Deletions
- Duplications
- Amplifications
- Translocations
- Inversions
Describe epigenetics in cancer (4 points)
Epigenetics – study of heritable changes in gene expression that do not involve changes in underlying DNA sequence:
- A change in phenotype without a change in genotype, which in turn affects how cells read the genes
- Inherited or environmental exposures during development and lifetime chemically modify DNA and the proteins bound to it