L3: Transformed cells and replicative immunity Flashcards
early observations growth factor dependence
Normal cells are dependent on growth factors to proliferate in culture
Cancer cells lose growth factor dependence
Graphs: as we increase level of serum, promotion in the growth rate of that population. Within the serum are lots of growth factors. So normal cells respond to growth factors. Compared to normal cells in very low serum conditions, the transformed cells growed even in low serum conditions.
cancer cells lose growth factor dependence
early observations- anchorage dependence
Early observations- anchorage dependence
Haemopoietic cells and early stem cells can grow in suspension
Most normal cells cannot grow in suspension (agar, agarose, methylcellulose) a liquid-rich media with serum? Need to provide a scaffold /adhesion for them to make them grow.
Epithelial and endothelial cells undergo programmed cell death in suspension - apoptosis (“anoikis”)
Cancer cells lose anchorage dependence. Grow in very soft agar that normal cells cannot grow in.
early observations- cell-cell contact inhibition
Early observations- cell-cell contact inhibition
Cell contact causes regular alignment and patterning of cells
Normal cells- when grown together in culture these cells start to align and grow to a certain extent but do not grow over eachother. Not multiple layers of cells, a single layer where cells are contacting eachother.
Cancer cells will grow over eachother, patterning is irregular
Cancer cells lose contact inhibition
early observations- density inhibition
Early observations- density inhibition 1
In a dense culture they will stop growing so pop-growth curve will tail off. Sense that there is a confluency and go into growth arrest
Confluent cells enter G0/G1 of the cell cycle and arrest their growth.
Early oservations- densitiy inhibition 2
Density inhibition
mainly due to exhaustion of growth factors (*see growth factor lecture)
saturation density is proportional to the serum concentration. If add really high levels of serum then trigger more proliferation.
If you add more serum (contains growth factors) to dense cultures - growth resumes
Cancer cells lose density inhibition and divide undcontrollably
early observations-life span
Early observations- life-span
Growth phase, maintenance phase, after a no. cell gens. These are normal cells. Freshly isolated. Proliferate for a short time then they stop growing. These cells get very big but do not divide.
GRAPH
Cultured normal cells have a limited life-span
Freshly isolated normal cells only proliferate for a short time Cells stop growing, enlarge and survive for long periods, but do not divide
early observations- growth arrest
Image- fiborblast cells from human foreskin.
Control- 5th passage (how old they are/how much they have been growing)
28th passage: the cells have changed their morphology, large and flat and stain positivley for beta-galactosidase. A marker for cell senseence. Senesence is a anti-tumour mechanism, prevents runaway growth by triggering a pathway where cells do not die- important for tissue integrity, but do not die.
For cancer cells- manage to avoid replicative sensence and become immortal. Not the same limited lifespan as normal cells.
HeLa cells
Derived from aggressive cervical cancer in 1951 from henrietta lacks. These cells are being cultured in laboratories today and are one of the most used cell lines in cancer research. Immortal.
genomic changes
The reason these behaviours are happening: genomic changes
Genomic changes: mutation, epigenetics, deletion, translocation, amplification.
We know these can be inherited, semantically- during lifetime of patient (maybe in tissue as an adult0 or due to pathogenesis e.g: hpv inin cervical cancer or h polori? In gastric cancer, environmental exposures e.g: abestos, carcinogens like nicotine
These drive those changes in behaviours
sustained proliferative signalling
Hallmarks of a cancer cell: Sustained proliferative signalling
Oncogene: a gene whose expression contributes to the development of cancer
derived from a cellular “proto-oncogene”
dominant over the normal proto-oncogene
Exist in nromal biology. Cellular proto-oncogene is normal. But oncogene is generally dominant over the normal proto-oncogene. A mutation in a proto-oncogene has caused a change in the behaviour of the protein and therefore becomes a tumour-driver. Generally, when mistakes are made, mistakes do not matter as huge amount of genome is non-coding. If inside coding sequence and also change the amino acid then problematic. Key- change protein functionality, inappropriate expression or amount of protein.
why are oncogenes causing cancer when pro-oncogenes do not
Why are oncogenes causing cancer when proto-oncogenes do not?
Overexpression- could be because of changes in promoter regulation, or gene itself has become amplified so have more copies.
inappropriate expression – this could be where a cell is expressing a growth factor and another is expressing a receptor but suddenly expresses the growth factor so auto-stimulates itself.
deregulation through mutation-
altered specificity/novel function
maybe lok at image
Protein- ras
Protein mutation- g12v
In pancreatic cancer- almost 90% has mutations in ras
Mutation in ras leads to an activated uncontrolled protein that is dysregulated. Change in promoter activity so more protein is being produced that would be in the normal setting. Because the protein is bcl2- a protein that supports cell survival, an advantage to have more of this protein.
Translocation- on the right middle. No normal biology- caused by fusion so no regulatory pathways that control its activity, completely uncontrolled. If that protein happens to drive cell proliferation, problematic.
Bottom- example of gene amplification. Gene itself is normal, but amplified. End up with alot more protein than expected. Protein example here is: EGFR, a growth factor receptor so elevated signalling and activation of pathways.
oncogene co operation> transformation
Tumourgenesis- combination events. Coperation between different oncogenes.
Ras alone - morphologically transforms primary cells, but they soon die. By itself, difficult to transform cells. Eventually become senesent or die off.
Myc - get immortalized lines at high frequency, but cells otherwise look normal
Ras + Myc = transformation. Cooperation between these oncogenes.
