Cancer (Cram Set) Flashcards
How do some tumour cell lines respond to presence and absence of ligand?
Same amount of phosphorylation in cells with and without ligand
Independent of ligand
Transduction pathway continues regardless
What does a kinase do?
Transfer a phosphate group
Opposite = phosphatase
What do tyrosine kinases do?
Phosphorylate tyrosine amino acids
What is the function of the receptor tyrosine kinase when it has bound to its ligand?
Signal transduction pathways ?> cell proliferation, survival and differentiation
How are receptor tyrosine kinases affected in cancerous cells?
Mutation that causes overexpression, transformed functions and autocrine and paracrine stimulation
What is the effect of this mutation at a cellular level?
Continuous proliferation and differentiation and survival ?> cell immortality
What is a proto?oncogene?
A gene that has the ability to become an oncogene due to mutation or increased expression
What is an oncogene?
Gene that has the ability to cause cancer by overriding apoptosis to make cells that undergo proliferation
What are tumour suppressor genes?
Genes that have the ability to slow down cell division, proliferation, repair DNA mistakes, apoptosis
Difference between oncogene and tumour suppressor gene?
Oncogene ? only one copy of gene needed
Tumour suppressor gene ? two copies needed
Cancer, cured or in remission?
In remission ? cancer could come back if not all cells killed, cancer could have metastasized, other types of mutation not killed ?> new cancer, needle could have missed cells, treatment itself could have cause cancers
Why might a single base pair change not actually alter gene expression?
May not change amino acid sequence because several codes may code for same amino acid sequence
Or different amino acids but have same function
What is the action of telomerase?
Adds a DNA sequence to 3’ end of telomere region of DNA strand ? protects terminal end of DNA from being broken down by enzymes
Telomerase in germ cells and embryonic stem cells?
Necessary for cell proliferation and so cells don’t go into senescence
In which tissues would telomerase most likely be found?
Skin, bone marrow, liver, gonads, gut lining
How might chromosomal instability lead to cancers?
Tumour suppressor genes may be deleted
Oncogenes may be amplified
Short telomeres in cancers?
Lots of chromosomal instability ? cancers
Lots of cell division ? shorter telomeres with every division
Telomerase in cancer cells
Slows cellular aging by extending dwindling telomere ends
What is VEGF?
A cytokine produced in cells with low oxygen to stimulate angiogenesis (formation of new blood vessels from preexisting ones)
Describe the ways in which viruses may transform cells to become oncogenic
Insertional mutagenesis ? insertion of viral DNA sequence next to a host’s proto?oncogene causes overexpression ?> uncontrolled cell growth
Transduction ? virus carries oncogene on genome ?> uncontrolled expression of a protein ?> rapid tumour formation
Transactivation ? expression of oncogenes upregulated by virus ?> uncontrolled cell growth
Why might overexpression of VEGF promote tumour growth?
Formation of blood vessels may lead to metastasis
May cause cells to survive and differentiate
If there is not sufficient VEGF for a rapidly growing tumour, what might happen?
Necrosis ? pus
What is e?cadherin?
Transmembrane protein that forms adherens junctions between adjacent cells using actin from cytoskeleton.
Requires calcium
How do the levels of cadherin expressed relate to metastasis of cancer?
Lower levels ? more metastasis
Cells less attached and more able to move in vessels and spread
Loss of cadherin can promote expression of transcription factors via epithelial?mesenchyme transition
