Extracellular matrix, stiffness, fibrosis and cancer

desmoplasia

• fibrotic state showcased by tumours

• inc deposition, altered organisation, post translational modification of ECM proteins

receptors which bind to collagen

DDR1/DDR2 - discoidin domain receptors

what do integrins bind to

collagen, fibronectin and laminin

what are syndecans 

• family of heparan sulfate proteoglycans

• interact with fibronectin

what is the laminin receptor

67kDa receptor

What are the major signaling components for interacting with the intracellular signals and hallmarks of cancer?

VEGF, FAK, Rho/ROCK, ERK/P13K

How does the G1/S cell cycle in proliferation link to the ECM?

• adhesion to the ECM

• allows growth factor dependent activation of Ras

• stimulates Erk signalling

What happens in the absence of integrin mediated adhesion to the ECM?

• Src and Erk signalling is not activated

• tumour supressor inhibitors remain high

• prevents cell proliferation

role of focal adhesion in ECM signalling

• mediates signals to tumour cells

• promotes activation of P13K pathway

• inc glycolysis

• stiffened tumours have upregulation of this pathway

what are the 2 matrisome proteins

• core matrisome

• matrisome associated

core matrisome proteins

• structural components

• collagen - triple helical structures

• proteoglycans - long GAGs, provide lubrication by binding to water

• glycoproteins - shorter, more complex oligosaccharide side chains, ECM assembly, binding growth factors

matrisome associated proteins

• secreted proteins that associate or modify the ECM

mass spectrometry proteomics 

• tissue undergoes mechanical or chemical disruption (surfactant)

• protein is extracted

• trypsin digests to give complex peptide sequences

• liquid chromatography coupled tandem mass spectrometry 

  • 1st MS quantifies signal, 2nd breaks down the peptide for identification

• matrisome project database for composition of protein identification 

does ECM secretion have circadian rhythmicity

yes

can the matrisome be altered by disease

yes

what increases the stiffness of the ECM

• inc conc of matrix proteins

  • higher polymerisation

what features of the matric define the mechanical properties

1. identification of proteins

2. concentration of matrix proteins

3. organisation of matrix proteins

4. crosslinking of matrix proteins

5. mineral deposition 

hallmarks of cancer

most cancers acquire the same functional capabilities

• sustaining proliferative signalling

• evading growth suppressors

• avoiding immune destruction

• enabling replicative immortality

• tumour promoting inflammation

• activation invasion and metastasis

• inducing angiogenesis

• genome instability and mutation

• resisting cell death

• deregulating cellular energetics 

which cell behaviours can be influenced by mechanical signals

• cell morphology

• contractility 

• propagation rate and apoptosis

• cell movement 

• differentiation

which cancer hallmarks are influenced by matrix and matrix mechanics

• sustaining proliferative signalling 

• resisting cell death

• activating invasion and metastasis 

focal adhesion kinase FAK

• limits sensitivity to growth inhibitors and apoptosis

MAPK/ERK

• promotes cell proliferation

VEGF

• induces angiogenesis (formation of blood vessels)

Rho/ROCK and Rac

• drives invasion and metastasis (described in cell contractility lectures)

what is the most significant risk factor for breast cancer after ageing 

high mammographic density

what is associated with high mammographic density 

• increased fibrillar collagen

• higher fibre organisation

• much stiffer 

cancer matrix composition

• misregulated cell proliferation

• inc matrix production by fibroblasts

• inc crosslinking by LOX

• reorganisation by proteases

• inc stiffness 

limiting factors in metastasis

• invasion into surrounding tissue is limited by cells ability to degrade the matrix

what is the stiffest organelle

nucleus

• determined by the lamin proteins in the envelope

• lamin A and lamin B 

lamin a expression and migration

• overexpression of lamin A will impede migration

• knowckdown will make tumours grow more rapidly

  • cells which have least lamin A can spread into surrounding tissue, more easily deformed

transglutaminase TGM

• crosslinking protein

• links peptide P1 and P2

LOX proteins in cancer

• elevated in many cancers 

• tumour hypoxia drives inc secretion of LOX

MMP matrix metalloproteinase

• range of ECM substrates

• zinc dependent 

• regulated by TIMPs

• excessive activity found in tumour cells and metastasis 

ADAMTS function

• collagen processing

• proteoglycan cleavage