Invasion of Extracellular Matrix

Slide 1 · Invasion of Extracellular Matrix

How carcinomas cross tissue barriers, reshape their microenvironment, and acquire motility

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Identify the successive extracellular barriers encountered by an invasive carcinoma.

Explain the four interdependent steps of extracellular matrix invasion.

Relate E-cadherin, proteases, integrins, and actin-based motility to invasive behavior.

Interpret stromal cooperation and the transition to intravasation.

Slide 3 · Local invasion and distant metastasis are distinct

Local invasion

Direct penetration of adjacent tissue compartments

Requires altered adhesion, ECM remodeling, and motility

Can destroy structures at the primary site

Distant metastasis

Requires additional vascular dissemination and colonization

Only a minority of entering tumor cells form deposits

Depends on interactions with distant host environments

Slide 4 · Invasion is an active cellular program

Carcinoma cells do not simply expand through a pre-existing opening.

They alter contacts with neighboring cells and extracellular matrix.

Proteolysis, receptor engagement, and movement are coordinated with stromal responses.

Schematic

Epithelial compartment

Epithelial basement membrane

Interstitial ECM

Vascular compartment

A breached boundary requires tumor-cell behavior—not growth alone.

Slide 5 · Two extracellular matrix compartments

Basement membrane

Separates epithelial and vascular compartments from adjacent tissue

Contains type IV collagen and laminin

An early and later barrier to disseminating cells

Interstitial connective tissue

Lies between epithelial structures and blood vessels

Includes collagens, glycoproteins, and proteoglycans

Must be crossed during movement toward a vessel

Slide 6 · The epithelial basement membrane defines a boundary

The basement membrane separates epithelial cells from the underlying connective tissue.

Carcinoma invasion requires penetration of this barrier.

Matrix organization also shapes cell attachment, signaling, and polarity.

Schematic

Epithelial compartment

Epithelial basement membrane

Interstitial connective tissue

Normal boundary

Crossing an epithelial basement membrane is a topologic change.

Slide 7 · Interstitial matrix is more than empty space

Connective tissue matrix occupies the path between an epithelial tumor and its vascular access.

Its constituents provide both physical resistance and binding sites for cells.

Matrix cleavage creates a route and biologically active fragments.

Schematic

Epithelial compartment

Epithelial basement membrane

Interstitial connective tissue

Slide 8 · The route from epithelium to circulation

Epithelial basement membrane

Interstitial connective tissue

Vascular basement membrane

Vascular lumen

In a distant organ, exiting the vessel requires barrier traversal in reverse.

Slide 9 · Matrix components have structural and signaling roles

Structural barrier

Type IV collagen supports basement membranes

Interstitial matrix maintains tissue compartmentation

Continuity limits unrestrained tissue traversal

Biologic interface

Laminin and collagen serve as receptor ligands

Proteolysis uncovers additional binding sites

Stored growth factors can be released by degradation

Slide 10 · Four linked steps drive local invasion

Loosen cell–cell contacts

Proteolytically degrade ECM

Attach to remodeled matrix

Migrate through tissue

The steps cooperate; The diagram is a teaching sequence, not four isolated switches.

Slide 11 · Adhesion loss enables tumor-cell detachment

Normal epithelial cells maintain strong cell–cell junctions.

Altered intercellular adhesion can dissociate tumor cells from one another.

This is the initiating step in the Robbins four-step model of invasion.

Schematic

Cell–cell adhesion

Dissociation

Slide 12 · E-cadherin mediates homotypic epithelial adhesion

E-cadherin is a transmembrane glycoprotein expressed by epithelial cells.

Its interactions help preserve cohesion between cells of the same epithelial compartment.

Disruption of its function weakens the contacts that restrain dissociation.

Schematic

Homotypic E-cadherin bonds

Cohesive epithelium

Slide 13 · E-cadherin also transmits intercellular signals

E-cadherin participates in signaling as well as physical adhesion.

Loss of function affects coordinated epithelial behavior, not only mechanical cohesion.

Adhesion molecules therefore connect tissue architecture to cell phenotype.

Schematic

Cell–cell adhesion

Adhesion-linked signaling

Slide 14 · Two paths to impaired E-cadherin function

E-cadherin mutation in selected epithelial tumors

Functional loss or expression silencing

Weakened tumor-cell cohesion

Greater opportunity for dissociation

The source describes both genetic loss and hypothesized, sometimes transient, silencing.

Slide 15 · Loss-of-function mutations are tumor-specific examples

Certain gastric and breast adenocarcinomas with E-cadherin loss due to mutation.

This is not presented as a universal mechanism in every carcinoma.

Many other epithelial cancers may reduce E-cadherin through different regulatory routes.

Schematic

Mutation

Expression silencing

E-cadherin function decreases

Weakened cell–cell adhesion

Slide 16 · Epithelial–mesenchymal transition is a proposed route

Epithelial–mesenchymal transition (EMT) changes epithelial-marker expression and motility-associated traits.

That EMT contributes to carcinoma invasion and metastasis.

Its role is expressed as a hypothesis, not an invariant requirement for all metastases.

Schematic

Epithelial state

Mesenchymal traits

E-cadherin ↓

Vimentin ↑

Smooth muscle actin ↑

More migratory potential

Slide 17 · SNAIL and TWIST participate in EMT regulation

The transcription factors SNAIL and TWIST are named regulators of the EMT program.

Their activity is linked to altered epithelial and mesenchymal marker expression.

The phenotypic consequence is thought to favor a migratory carcinoma cell.

Schematic

SNAIL / TWIST

Marker-expression changes

Promigratory phenotype

Slide 18 · EMT changes a coordinated marker pattern

Epithelial-associated

E-cadherin expression

Cohesive cell–cell interactions

Maintained epithelial organization

Mesenchymal-associated

Vimentin expression

Smooth muscle actin expression

Promigratory traits

Markers describe a coordinated phenotype; No single marker establishes metastatic behavior.

Slide 19 · EMT links transcription to cellular behavior

SNAIL / TWIST activity

Reduced epithelial markers

Increased mesenchymal markers

Promigratory phenotype

The causal framing follows the hypothesized mechanism.

Slide 20 · EMT is not identical to successful metastasis

Enhanced motility helps local tissue invasion but does not guarantee distant colonization.

The metastatic cascade also requires circulation, survival, homing, and growth.

Different tumor-cell phenotypes and even cohesive groups may participate.

Schematic

Local ECM invasion

Circulation

Distant colonization

Separate later steps

Slide 21 · Adhesion changes create an invasive opportunity

A carcinoma retains proliferation but shows reduced intercellular cohesion. Which invasion step is directly facilitated?

Mechanistic interpretation

The first step: Loosening tumor cell–tumor cell interactions.

Reduced cohesion alone does not demonstrate ECM proteolysis or migration.

Additional processes are required to breach the basement membrane.

Slide 22 · ECM degradation removes physical obstacles

Proteolysis acts on epithelial basement membrane and interstitial connective tissue.

Breaches in matrix permit tumor cells to enter neighboring tissue compartments.

The same principle applies when approaching a vascular basement membrane.

Schematic

Extracellular matrix barrier

Tumor / stromal proteases

Matrix breach / remodeled ECM

Slide 23 · Proteases originate from tumor cells and stroma

Tumor-cell contribution

Secretion of matrix-degrading proteases

Signals that induce protease release from stroma

Participation in remodeling at the invasion front

Stromal contribution

Fibroblasts can produce proteases

Inflammatory cells can produce proteases

The tumor microenvironment participates actively

Slide 24 · Three protease systems highlighted by Robbins

Matrix metalloproteinases

Remodel basement membrane and interstitial matrix

Cathepsin D

A protease implicated in tumor-cell invasion

Urokinase plasminogen activator

A proteolytic system implicated in tumor-cell invasion

Slide 25 · Matrix metalloproteinases do more than digest

MMP-mediated ECM cleavage

Physical remodeling of barriers

Release of matrix-held factors

Generation of signaling fragments

Proteolysis is simultaneously structural remodeling and biologic signaling.

Slide 26 · MMP9 acts on type IV collagen

MMP9 is described as a gelatinase that cleaves type IV collagen.

Type IV collagen is present in epithelial and vascular basement membranes.

This action supports penetration of basement-membrane barriers.

Schematic

Type IV collagen (basement membrane)

MMP9

Matrix breach / remodeled ECM

Slide 27 · Epithelial and vascular basement membranes share vulnerability

At the primary epithelium

Basement-membrane cleavage permits invasion into stroma

Loss of compartment boundary enables local tissue infiltration

At the vessel

Vascular basement-membrane remodeling assists entry

Subsequent endothelial transmigration gives vascular access

Slide 28 · MMP9 can mobilize matrix-sequestered VEGF

ECM can retain vascular endothelial growth factor (VEGF).

MMP9-mediated release of VEGF from these stores.

Thus matrix degradation can contribute to an angiogenic microenvironment.

Schematic

ECM-bound VEGF

MMP9 proteolysis

Released VEGF

Angiogenic signaling

Slide 29 · ECM cleavage products can act as signals

Cleavage of collagen and proteoglycans yields matrix-derived fragments.

Some products with chemotactic, angiogenic, and growth-promoting effects.

Degradation products can therefore influence subsequent cell behavior.

Schematic

Chemotactic / angiogenic / growth effects

Slide 30 · Protease activity reflects a balance

Protease abundance or activity

Reduced metalloproteinase inhibition

Net increase in matrix proteolysis

Greater potential for tissue remodeling

A greater net proteolytic drive favors invasion; The model is qualitative.

Slide 31 · Reduced inhibitors reinforce ECM degradation

Several cancers show decreased concentrations of metalloproteinase inhibitors.

Lower inhibition shifts the local balance toward proteolysis.

Invasion depends on the functional protease–inhibitor relationship, not a single enzyme in isolation.

Schematic

Protease activity

Inhibitor activity

Net ECM degradation reflects the balance

More degradation when proteolysis predominates

Slide 32 · MMP9 differs qualitatively by tumor behavior

Benign tumors

Little MMP9 activity in benign breast, colon, and stomach tumors.

This is a qualitative tissue comparison.

Malignant counterparts

The corresponding malignant tumors may overexpress MMP9.

The text provides no numerical test cutoff.

Do not infer a stand-alone diagnostic MMP9 threshold from this comparison.

Slide 33 · Proteolysis and motility must cooperate

Suppose matrix breakdown is extensive, but tumor cells cannot form new ECM attachments. What step remains impaired?

Mechanistic interpretation

Attachment to remodeled ECM components is still deficient.

Proteolysis alone does not provide traction for locomotion.

The sequence requires coordinated receptor binding and actin-based movement.

Slide 34 · Integrins link tumor cells to extracellular matrix

Integrins are transmembrane receptors that bind components of ECM.

They mediate adhesion and transmit intracellular signals.

Changes in integrin expression or localization alter tumor–matrix interactions.

Schematic

Integrin–ECM interactions

Receptors transmit matrix-derived signals

Slide 35 · Normal epithelial integrins are basally restricted

Basal integrins bind basement-membrane laminin and collagens.

Their polarized distribution supports the resting state of epithelial cells.

Loss of normal polarity is part of altered neoplastic cell–matrix interaction.

Schematic

Basal receptor polarity

Attachment supports epithelial polarity

Slide 36 · Cancer cells alter the integrin repertoire

Complex changes in integrin expression during invasion.

Alternative integrins can support attachment under abnormal ECM conditions.

Some integrin signals also promote survival when normal adhesion is lost.

Schematic

Altered integrin engagement

Different receptors can support survival

Slide 37 · Normal detached cells may undergo anoikis

Normal epithelial cells depend on appropriate ECM attachment.

Loss of adhesion can trigger a form of apoptosis termed anoikis.

Anoikis helps distinguish normal attachment dependence from free tumor-cell survival.

Schematic

Detached epithelial cell

Anoikis (apoptosis)

Slide 38 · Anoikis resistance favors invasive survival

Tumor cells may survive despite losing their customary matrix contacts.

This in part to alternative integrins delivering survival signals.

Resisting anoikis is useful as cells detach and traverse changing ECM niches.

Schematic

Detached epithelial cell

Alternative integrin survival signals

Slide 39 · MMP2 and MMP9 expose new attachment sites

MMP2 or MMP9 cleavage can modify type IV collagen and laminin.

Proteolysis creates novel sites that tumor-cell receptors can bind.

The newly available contacts may stimulate cell migration.

Schematic

MMP2 / MMP9 cleavage

Novel ligand sites

Tumor receptor binding

Slide 40 · Degradation and receptor binding reinforce one another

Proteases remodel collagen IV / laminin

Novel ECM binding sites appear

Altered tumor-cell receptors engage matrix

Migration signaling is supported

The matrix becomes an active migration substrate after remodeling.

Slide 41 · ECM serves as both barrier and migratory track

Before remodeling

Intact architecture separates tissue compartments

Polarized attachment supports epithelial organization

After remodeling

Proteolysis opens passages and exposes ligands

Tumor cells can attach to altered matrix and move

Slide 42 · Why detachment alone is insufficient

A cell loses E-cadherin but remains sensitive to anoikis. What limits its invasive fitness?

Mechanistic interpretation

Cell–cell dissociation may occur, but ECM detachment can still trigger apoptosis.

Resistance to anoikis provides a survival advantage under altered attachment.

Adhesion, survival, and movement are separate requirements.

Slide 43 · Locomotion closes the four-step invasion sequence

The final step is tumor-cell movement through regions of matrix breakdown.

Movement requires receptor signals and the actin cytoskeleton.

Adhesion must be dynamically assembled and disassembled.

Schematic

Matrix anchoring

Coordinated movement

Direction of movement →

Slide 44 · The migrating cell has a front and a rear

The leading edge creates new attachments to matrix.

The trailing edge releases previous attachments.

Actin-based contractility enables net displacement through tissue.

Schematic

Rear detaches

Front attaches

Direction of movement →

Slide 45 · Leading-edge adhesion provides traction

A migrating tumor cell must bind the matrix ahead of its body.

Receptor engagement anchors the leading edge during movement.

Remodeled ECM provides potential sites for these new attachments.

Schematic

Leading-edge traction

New ECM contacts

Direction of movement →

Slide 46 · Trailing-edge release allows forward movement

Persistent adhesion at the cell rear would oppose net translation.

Migrating cells therefore detach matrix contacts at their trailing edge.

Turnover of cell–matrix contacts is as important as their formation.

Schematic

Rear release

Old contacts disassemble

Direction of movement →

Slide 47 · Actin contraction generates cell translocation

Multiple signaling pathways converge on the actin cytoskeleton.

Contractile movement can draw the cell body forward relative to anchored contacts.

Migration depends on spatial coordination, not simply stronger adhesion.

Schematic

Actin contraction

Cell-body movement

Direction of movement →

Slide 48 · Motility cues can be autocrine

Tumor cells can produce cytokines and chemokines that affect their own movement.

Robbins also cites growth factors, including insulin-like growth factors.

Such self-derived signals are described as autocrine motility factors.

Schematic

Self-derived chemokines / IGF

Slide 49 · Matrix cleavage products provide another cue

Degradation of collagen or laminin can release biologically active fragments.

These matrix-derived products may influence tumor-cell movement.

Thus the physical path and the local guidance environment change together.

Schematic

Collagen / laminin fragments

Motility cues

Slide 50 · Stromal HGF stimulates tumor-cell MET

Stromal hepatocyte growth factor (HGF), also called scatter factor, is a paracrine cue.

HGF binds MET, a receptor tyrosine kinase on tumor cells.

This pathway as promoting tumor-cell motility.

Schematic

Stromal cell

Tumor cell: MET

HGF / scatter factor

Increased motility

Slide 51 · Three sources of directional/motility signals

Tumor-derived

Chemokines and cytokines

Insulin-like growth factors

Autocrine stimulation

Matrix- and stroma-derived

Collagen / laminin cleavage products

Stromal HGF / scatter factor

Paracrine and matrix-associated stimulation

Slide 52 · The relevant motility cues vary across tumors

Robbins does not assign one universal chemokine or growth-factor pathway to every tumor.

Multiple receptors and signaling systems can converge on the cytoskeleton.

Different cancers may achieve migration using different combinations of cues.

Schematic

Tumor factors

Matrix fragments

Stromal HGF

Receptors → actin cytoskeleton

Slide 53 · Invasion is a tumor–stroma collaboration

Tumor cells interact with fibroblasts, inflammatory cells, immune cells, and endothelium.

Host-cell participation supplies proteases, ECM alterations, and motility cues.

Invasion is therefore not a solely tumor-cell-autonomous process.

Schematic

Fibroblast / immune cell

ECM / growth factors / proteases

Slide 54 · Cancer-associated fibroblasts remodel the niche

Invading cancer cells can change fibroblast gene-expression programs.

Cancer-associated fibroblasts alter ECM molecules, proteases, inhibitors, and growth factors.

These changes may build a local environment that supports malignant behavior.

Schematic

Cancer-associated fibroblast

ECM, proteases, inhibitors, growth factors

Slide 55 · Tumor and stroma influence one another

Invading tumor-cell signals

Altered stromal-cell phenotype

Changed ECM / protease / growth-factor output

Further support for tumor invasion

A reciprocal interaction, not a fixed one-way process.

Slide 56 · Immune and endothelial cells are part of the niche

Innate and adaptive immune cells among interacting stromal populations.

Endothelial cells form the next barrier to vascular entry.

The exact cell-specific mechanisms remain incompletely defined account.

Schematic

Epithelial compartment

Epithelial basement membrane

Interstitial connective tissue

Vascular compartment

Slide 57 · Intravasation is the local-phase endpoint

Invading carcinoma cells penetrate the endothelial basement membrane.

They then transmigrate into the vascular space.

After vascular entry, survival and distant colonization are separate steps of the metastatic cascade.

Schematic

Epithelial compartment

Epithelial basement membrane

Interstitial ECM

Vascular compartment

Slide 58 · Different barriers must be distinguished

Epithelial barrier

Basement membrane below the primary epithelium

Crossed during initial local invasion

Vascular barrier

Endothelium and its basement membrane

Crossed to reach the circulation

The first breach does not automatically mean intravasation.

Slide 59 · A schematic boundary tests the concept of invasion

In two conceptual epithelial lesions, one has an intact basement membrane and the other has tumor cells beyond it. Which depicts stromal invasion?

Mechanistic interpretation

Tumor cells beyond a breached epithelial basement membrane represent stromal invasion in this schematic.

This is a topological teaching example, not a patient specimen or full diagnostic rubric.

The same matrix interactions explain how cells then move toward vessels.

Slide 60 · Why high invasion does not imply high metastasis

Local tissue invasion is necessary but not sufficient for hematogenous metastasis.

Cells still face survival, transport, arrest, extravasation, and colonization challenges.

The overall inefficiency and complexity of successful metastasis.

Schematic

Local ECM invasion

Circulation

Distant colonization

Separate later steps

Slide 61 · Integrated mechanism: From cohesion loss to migration

E-cadherin loss / EMT-associated changes

Tumor- and stroma-derived proteolysis

Integrin binding to remodeled ECM

Actin-driven locomotion and vascular access

Sequential model of invasion (schematic)

Slide 62 · Predicting the effect of restoring cell adhesion

Which step of invasion would be most directly opposed if functional epithelial E-cadherin contacts were restored?

Mechanistic interpretation

The dissociation/loosening stage would be most directly opposed.

Effects on degradation or migration should not be assumed from E-cadherin restoration alone.

The invasion phenotype integrates multiple pathways.

Slide 63 · Predicting the effect of lower protease activity

What immediate ECM-level consequence is expected when functional matrix degradation is reduced?

Mechanistic interpretation

Basement membrane and interstitial matrix are less readily remodeled.

Generation of matrix cleavage fragments and liberation of stored factors may also decrease.

Compensation by other proteases or stromal pathways is possible.

Slide 64 · Predicting the effect of failed rear-edge release

A tumor cell makes new leading-edge attachments but cannot release its trailing edge. Why may net movement be impaired?

Mechanistic interpretation

Movement requires coordinated formation and disassembly of adhesions.

A persistently attached rear can oppose cell-body translocation.

Motility reflects the entire actin–adhesion cycle.

Slide 65 · Predicting the effect of impaired MET signaling

If HGF–MET motility signaling is reduced, which input is directly affected?

Mechanistic interpretation

The stromal HGF/scatter-factor paracrine motility input is affected.

Other autocrine or matrix-derived cues may still operate.

Robbins does not imply that MET is the only route to invasion.

Slide 66 · Four mechanisms, four representative molecules

Adhesion / proteolysis

E-cadherin: Epithelial cell–cell cohesion

MMP9: Collagen IV cleavage and growth-factor release

ECM interaction / movement

Integrins: Attachment and survival signaling

MET: Receptor for stromal HGF motility cue

Representative examples are not exclusive biomarkers of invasive cancer.

Slide 67 · Common interpretive errors

Do not equate reduced E-cadherin with proof of completed metastasis.

Do not treat MMP9 expression as a universal quantitative diagnostic cutoff.

Do not portray proteolysis as merely mechanical, or EMT as mandatory in every tumor.

Do not omit fibroblasts and immune cells from an invasion mechanism.

Slide 68 · Four-step mechanism at a glance

Cohesion decreases

ECM is proteolytically remodeled

Altered integrins engage new matrix sites

Cytoskeletal motility advances the tumor

A coordinated, microenvironment-dependent process leading toward vascular access.

Slide 69 · References and interpretation boundary

Robbins, Cotran & Kumar: Pathologic Basis of Disease, 11th ed. (2026), Chapter 7, “Invasion of Extracellular Matrix,” printed pp. 274–275.

Context: Chapter 7, “Invasion and Metastasis”; Chapter 1, ECM/integrin background.

Original editable schematics in this lecture are conceptual representations, not source-figure reproductions or histologic specimens.