Final Flashcards
what is stroma
- tumor microenvironment
- refers to everything in the tumor environment that does not include non-neoplastic cells
What are the cell types
- immune cells
- fibroblasts (connective tissue)
- endothelial cells (blood vessels)
- adipocytes (fat tissue)
what is the extracellular components of the stroma
extra-cellular matrix (ECM)
What is the ECM made of?
secreted proteoglycans (proteins with added sugars)
what does the stroma play an active role in?
in development and maintenance of tumors
neoplastic and non-neoplastic cells are present in comparable number (50/50) in what kind of tumor
carcinomas
what is the pdx model
Transplantation of human cancer cells into live mice
why is the pdx model typically done
to model an in vivo microenvironment
- because tissue culture plastic (in vitro models) do not accurately recapitulate a tumor microenvironment
definition of heterotypic signaling
communication between dissimilar cell types
generally, what do cancer cells release
chemokines and growth factors that attract stromal cells and cause the proliferation of stromal cells
what do stromal cells contain
receptors for growth factors that cancer cells release
neoangiogenesis
formation of new blood vessels
What do stromal cells release
growth factors that cause the proliferation of cancer cells
what do cancer cells contain
receptors for growth factors that stromal cells release
endothelial cells
cells that line blood vessels and capillaries (smaller blood vessels)
pericytes
the outer layer of blood vessels and capillaries (support blood vessels)
angiogenesis signlaing
epithelial cells and stromal cells signal endothelial cells to proliferate
what do endothelial cells secrete
growth factors and attract pericytes
what do pericytes secrete
pro-survival signals to endothelial cells (including VEGF1)
what does heterotypic signaling generally promote
the development and maintenance of blood vessels in tumors
capillaries in tumors are constructed _____ compared to normal tissues
haphazardly
characteristics of tumor capillaries
- pericytes do not completely cover the capillaries
- pericytes are more loosely associated with the capillaries
- endothelial cells do not form a continuous sheet; there are gaps between neighboring cells
- tumor capillaries are 3x bigger than normal capillaries
- results in leakage of fluid into tumor microenvironment
- causes tumors to have high hydrostatic pressure
- complicates delivery of anti-cancer therapeutic drugs
- prevent formation of pressure-gradient
what does the hazardous formation of tumor capillaries result in
results in inefficient transfer of anti-cancer therapeutic drugs to the site of the tumor (anti-cancer drugs would preferentially accumulate in normal tissue compared to tumor tissue)
similarities between wound healing and angiogenesis
- recruitment of stromal cells
- stromal cells recruit and activate endothelial cells
- immune cells
what do stromal cells recruit and activate
endothelial cells
- partially because stromal cells secrete VEGF
- which stimulates neoangiogenesis
what do immune cells promote
neoangiogenesis via VEGF
what do immune cells secrete
MMPs (matric metalloproteases) which release growth factors tethered to the ECM
angiogenic switch
a property that pre-malignant cells must acquire to be able to form a tumor
most normal cells do not have the ability to…
make blood vessels around them (promote neoangiogenesis)
in order for a cancer cell to progress towards malignancy they must first acquire
the ability to make blood vessels around them (promote neoangiogenesis)
what is an example of the angiogenic switch
RIP-tag mouse model of pancreatic cancer (beta cells)
how often does hyperplasias actually progress to form tumors?
only a few percent
what flips the angiogenic switch
macrophage recruitment to the microenvironment flips the angiogenic switch
what do macrophages secrete
MMPs release VEGF that was trapped in the ECM
what does VEGF promote?
neoangeogenesis
SHORT ANSWER: Be able to briefly describe the details of this figure using the following terms: tumor,
oxygen, capillaries. Be able to describe what occurs to cancer cells in normoxic and
hypoxic conditions
picture of blood vessels in tumors
green - capillaries
red- regions with low oxygen levels
- the cells located more than 0.2mm from the blood vessels stop dividing and begin to die due to low O2 and low pH (these condition promote cell death)
metastasis
the process by which cancers that travel to distant sites and form new tumor colonies
what is responsible for 10% of cancer deaths
primary tumors
what are 90% of cancer deaths caused by
metastases
general process of metastasis formation
- primary tumor formation
- localized invasion, breaching the basement membrane
- intravasation into blood or lymph ducts
- transport through circulation
- arrest in microvessels of various organs
- extravasation out of the microvessel into the secondary site
- formation of micrometastasis
- colonization- formation of a macrometastasis
what is a good predictor of metstasis
loss of the basement membrane
what kind of patients did not form metastases
patients with rectal carcinomas that were removed and had evidence of intact basement membranes
what kind of patients developed metastases 50%
patients with rectal carcinomas that were removed and had evidence of loss of basement membranes
what does invasion require
secretion of MMPs
what are MMPs
- matrix metalloproteases
- enzymatic proteins that can degrade proteins in ECM
How are MMPs secreted
- can be secreted by neoplastic cells or nearby non-neoplastic cells in the microenvironment
why does invasion rely on the secretion of MMPs
this allows the carving out of physical space for cancer cells to move into during metastasis
metastasis requires cancer cell to undergo
a partial EMT (epithelial to mesenchymal transition)
EMT and mesenchymal characteristics
when epithelial cells lose their epithelial morphology and gain a morphology similar to mesenchymal cells
- loss of cell-cell contacts
- cells become less plump and more flat
- loss of epithelial markers (E-cadherin)
- gain of mesenchymal markers (N-cadherin)
what are the results of EMT
cells are no longer attached to one another and are more capable of motility/migration
What is EMT important for in normal cells
development and wound healing
cadherin proteins
transmembrane proteins that are capable of homophilic interactions in their extracellular domains
- meaning they can interact and make physical contact with a cadherin protein of the same type
ex: the extracellular domain of E-cadherin on one cell interacts with extracellular E-cadherin domain of another cell; forming a junction which is responsible for keeping epithelial cells connected to one another so they form a continuous sheet of cells
E-cadherin
the cadherin expressed in epithelial cells
- strong interactions with each other
- contributes to epithelial cells being stationary
- generally not expressed in cancers
N-cadherin
- cadherin expressed in mesenchymal cells
- interactions are relatively weak
- contributes to motility
- generally expressed in cancers
E-cadherin interacts with
the transcription factor B-catenin
- this sequesters B-catenin to the plasma membrane so B-catenin cannot act as a transcription factor
what happens to E-cadherin in EMT
E-cadherin is lost, B-catenin can enter the nucleus and activate the txn of genes that further promote an EMT
FREE RESPONSE: Be able to briefly describe metastatic inefficiency and if it is generally good or bad for
us.
- once cells enter the blood vessels, they become circulating tumor cells but for metastasis to occur, these cells must extravasate the blood vessel and invade surrounding tissue
- inefficiency is that only a small portion of circulating tumor cells will actually succeed in making a new tumor
- this is generally good for us
FREE RESPONSE: Be able to briefly describe metastatic tropism.
- for a cancer cell to colonize a new tissue it must find a suitable environment
- tropism is the tendency of cancer cells from one primary tumor type to colonize
what is evidence that immune cells help fight against cancer
TIL - tumor infiltrating lymphocytes
- the more TILs someone had, the higher fraction of them surviving ovarian carcinomas
immune cells are complicated ro what reason
- some immune cells promote an anti-cancer immune response while other immune cells can actually inhibit an anti-cancer immune response
innate immune system
branch of the immune system that helps fight off multiple types of foreign invaders based on a similar property
adaptive immune system
branch of the immune system that helps fight off a specific foreign invader by developing a defense against a specific protein on the foreign invader - antigen
immune response
if a cancer cell produces a protein that has a mutation and is different than the host protein sequence (neoantigen) this can cause an immune response
MHC class I
transmembrane protein that presents intracellular proteins on the outside of a cell
cytotoxic T-cells
will detect if a neo-antigen displayed by a MHC class I protein is foreign and will mount an immune defense
(ex: cancers with mutated RAS)
natural killer cells
will target and kill any cancer cell that has downregulated their MHC class I system
- by releasing cytotoxic granules that will kill target cells
regulatory T cells (Treg)
immune cells that function to decrease the immune response
what are Tregs important for normally
important in normal situations so that our body stops the immune response when it is not necessary
How do cancer cells take advantage of Tregs
- cancer cells secrete chemokines that specifically recruit Tregs which will promote an immunosuppressive environment
- Tregs will inhibit the function of other anti-cancer immune cells in the area
- cancer cells signal immune precursor cells in the tumor microenvironment to differentiate into Tregs
macrophage
phagocytic cells that can phagocytose and digest target cells
What are the different states of macrophages
M0 - undifferentiated
M1 - cytotoxic and phagocytic state (kill/eat cancer)
M2 - immunosuppressive state (protect cancer cells)
What do successful cancer generally contain more of?
M2s than M1s
- the more M2s, the more deadly
How do cancer cells escape death by M1s
they display dont eat me signals on the surface of their cells
CD47
“dont eat me” signal; cell surface receptor that tells M1s to not attack
Be able to describe the general function of Tregs. Be able to describe a specific
mechanism how cancer cells upregulate Tregs. Be able to describe that recruitment of
Tregs cause a general immunosuppressive environment so immune cells that function to
attack/kill cancer cells are inhibited.
-Tregs are immune cells that function to decrease the immune response
- cancer cells upregulate Tregs by secreting chemokine CCL22 that specifically recruit Tregs
- or TGFB ligands are secreted by the tumor that signal lymphocyte precursor cells to differentiate into Tregs
- this promotes an immunosuppressive environment b/c Tregs will inhibit the function of other anti-cancer immune cells in the area
JC4:
experiment/results/general conclusion
experiment:
cells in s-phase are treated with UV and collected every 10 minutes. Western blot performed using an anti-BRCA1 antibody to detect levels of BRCA1 protein and the size
results:
- BRCA1 protein runs slower over time (getting larger)
- BRCA1protein is phosphorylated in response to UV treatment/DNA damage
- largest shift after 30 minutes
- the time corresponds to a change in physical location of BRCA1 in the cell
conclusion:
- in response to DNA damage BRCA1 is phosphorylated and moves to sites of DNA damage
JC5:
description of graph, results, interpretation/significance
description:
- stipple bars (small dots): quantification of % islets that are angiogenic (in vitro)
- slashed bars: quantifications of % of islets that are angiogenic tumors (in vitro)
- black bar: incidence of hyperplastic islets (in vivo)
- slashed bar: incidence of tumors (in vivo)
results:
- 3% are angiogenic
- 1% are angiogenic tumors
- 75% are hyperplastic by 12 weeks
- 1% form tumors at 12 weeks
significance:
- suggests that there are a high amount of hyperplasia’s in the RIP-Tag model of pancreatic cancer
- but only a few percent of the hyperplasia’s will progress to tumors
- this suggests that the acquisition of angiogenesis is important for a hyperplasia to be able to progress to a tumor.
JC6:
experiment, results, results of whole paper
experiment:
- percent of macrophages that are cathepsin-ABP positive were quantified
results:
- cathepsin-ABP tends to colocalize with the macrophade marker
- cathepsin is secreted by macrophages
- the number of macrophages increase with progression
- the number of cells that are Cath-ABP+ increases with progression
- suggests successful tumor progression involves the presence of macrophages that secrete cathepsin
results of whole paper:
- successful tumors find a way to recruit macrophages that secrete cathepsin
- cathepsin likely degrades the extracellular matrix
- this likely promotes angiogenesis
- this likely also promotes metastasis
