TOPIC F: Cancer Flashcards
What are the physical characteristics of a cancer cell compared to a normal cell
Enlarged nucleus Changes to cytoskeleton Loss of specialised features Little cytoplasm Evidence of mitosis
No growth constraints (not limited by neighbouring cells or environment)
No physical attachment
What is a carcinoma
A cancer arising from epithelial cells of the skin and lining of organs
85% of all cancers
breast, lung, colon cancers
What is a sarcoma
Cancers arising from bone, muscle and blood vessels
What is a Lymphoma
Cancer arising from lymphoid cells and leukemias from white cells of the bone marrow
Do cancer cells require growth factors
No, can have greatly reduced requirement for growth factors
What is the relationship between cancer cells and telomeres
Cancer cells have chromosomal aberrations
- change in no. of chromosomes
- change in chromosome structure
Telomere shortening regulates how many round of cell division can occur. Cancer cells can ignore telomere shortening and keep dividing
What are the basic transitions of cancer progression
A single mutant cell
to a tumour
to metastasis (cancer spreads throughout body)
At least 4-6 mutations to reach the tumour state. process can decades for single mutant cell to proliferate into palpable tumour
What are the 2 types of tumours
Benign: look like original tissues. Localised (do not spread). Don’t cause problems unless in confined space (like brain)
Malignant: Do not look like original tissue. Physical changes, spread
Explain metastasis
When cancers invade other issues and spread throughout body.
Depends on type of cancer
Takes a lot of energy to proliferate and spread so angiogenesis occurs
Explain angiogenesis
The mechanism where tumours direct capillaries to travel into the tumour so it can have nutrients and oxygen for growth.
Angiogenesis can be targeted to stop cancer from growing
What are some of the implications of cancer genetic alteration
Increased cell growth
Resistance to apoptosis
Altered tissue invasiveness
Angiogenic proliferation
Ability to escape immune surveillance
What are 2 main causes of cancer
DNA damage
Viruses
Explain the types of DNA damage that can lead to cancer
Inherited (germ lime errors): every cell in body carries one copy of DNA with defect. 10% of cancers
Acquired (somatic errors): may lead to cancer in that tissue. only cancer cells carry mutation
How can acquired DNA damage leading to cancer be caused
Environmental exposure to:
radiation
viruses
bacteria
chemical carcinogenesis
age and diet
UV light
Cancer cells accumulate more and more errors over time. Why does this occur?
Ususally DNA repair enzymes can correct but
- substantial mutations
- loss of DNA repair enzymes
- less time for repair mechanism (rapid cell cycle to divide)
can lead to further DNA damage
Explain how viruses can lead to cancer
Infectious agents like viruses are causal agents in some cancers.
15% of cancers like nasopharynx, cervical, liver and lymphomas
Explain what an oncogene, tumour suppressor gene, mismatch repair gene, and proto-oncogene are.
Oncogene: promotes cancer
Tumour suppressor gene: act to prevent cancer
Mismatch repair gene: repair mutated DNA
Proto-oncogene: Normal genes that promote cell growth and division that could become an oncogene
What mutations can occur on a proto-oncogene
Deletion or point mutation = hyperactivity
Gene amplification = normal protein overproduced
Chromosome rearrangement = changes in regulation
Oncogenes are dominant meaning…
that one gain-of-function mutation can predispose a cell to cancer as it overrides the rest of cellular function
What cell functions are tumour suppressor genes involved in
Control cell cycle check points
Induce transcription of regulatory inhibitory genes
Overall, negatively control cell growth
What mutation can occur for a tumour suppressor gene
Loss of function mutation
Can be inherited or acquired
Both copies of gene must be lost for cancer to develop (two hit hypothesis)
Explain the two hit hypothesis
Loss of one copy of a tumour suppressor gene causes a slight cell progression advantage
Loss of both copies causes complete inactivation, significant growth advantage and predisposition to cancer
What is retinoblastoma
Rare childhood tumour of the retina (neural precursor cells of retina)
Caused by non-function retinoblastoma (Rb) tumour suppressor gene
2 forms: hereditary and sporadic
Both copies of gene must be lost
Explain the 2 types of retinoblastoma
Hereditary: young age, tumours in both eyes, mutant Rb allele on chromosome 13 in every cell of body
Non-hereditary/sporadic: 1 tumour in 1 eye, later age, mutant only in tumour cells
