3. INTRODUCTION
INVASIVENESS OF CANCER CELLS
Tumor invasion is an intrinsic property cancer cell
progression to metastasis after intravasation into the blood
vessels.
INVASIVENESS is a phenomenon which involves the
dissemination of cancer cells through the destruction of the
basement membrane.
Invasion is when the cancer growth goes into a new part
within an organ, as the tumor gets larger and larger it spread
through the organ.
3
4. INVAPODIA or invasive feet are protrusions in the cancer cell
membrane that are rich in actin and extend into the
extracellular matrix (ECM).
The assembly of actin core structures, followed by the
accumulation of matrix metalloproteinase promote ECM
degradation.
These structures are very similar to the PODOSOMES formed
by normal cells that need to cross tissue barriers such as
MACROPHAGES,
MONOCYTES,
OSTEOCLASTS that remodel tissue.
4
5. However podosomes are short – lived and do not cause
major degradation of ECM.
These assembly of actin core structures in invapodia of
transformed tumor cells are associated with high levels of
proteolysis and cell signaling
COMPONENTS OF INVASIVENESS
ACTIN REGULATION: Cofilin, Profilin, Thymosine –
β4, Ar2/3, NWASP
5
7. Src (SCHIMIDT RUPPIN A – 2 PROTEIN)
c-Src tyrosine kinase also known as proto-oncogene c-Src, is
a nonreceptor tyrosine kinase protein that in humans is
encoded by the SRC gene.
Src is a potent inducer of tumor invasion which would
eventually progress to metastasis.
It includes an SH2 domain, an SH3 domain, and a tyrosine
kinase domain.
7
9. The binding of Arp2/3 to NWASP recruits CDC42/CIP4 to
induce EGRF which activates the mutated Src through the
integrin homing receptor present on the ECM (Extracellular
Matrix).
The assembly of F – Actin is induced by Src. F – Actin recruits
MMPs and proteases leading to tumor cell invasion.
9
10. C – Src is regulated by phosphorylation of tyrosine 527 on its
SH2 domain
Mutation of tyrosine 527 by tumor cells converts the proto –
oncogen c – Src to Src. Initiate invasion and promote
metastasis.
STABILITY OF INVAPODIA: The polymerization of F – Actin by
formins and fascin and barbed ends generated by cofilins
stabilizes invapodia and promotes invasion of tumor cells.
10
25. Malignant tumors secrete proteolytic enzymes to degrade
basement membrane thus allowing invasive behavior.
CLASSES OF PROTEOLYTIC ENZYMES
MATRIX METTALLOPRTEINASES:
They are expressed in all forms of cancer and can be
classified according to their structure into eight different
classes of MMPs.
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26. PROTEINASES OF FIBRINOLYTIC SYSTEM.
The components of the fibrinolytic system is zymogene
plasmogen which is secreted in the liver and deposited in
tumor in response to hyper permeability
The conversion of plasminogen to plasmin is regulated by two
plasminogen activators TPA and UPA.
Plasmin facilitate tumor cell migration, invasion metastasis by
degrading fibrin and other matrix protein directly by
activating several metalloproteinases that additionally
degrades extracellular matrix .
26
27. Exposure of breast carcinoma cells to estrogens induces upper
and uta which is required for the activation of plaminogen
which is responsible for the degradation of the extracellular
matrix.
In ovarian cancer lysophosphatidic acid may induce the
secretion of UPA through EDG (endothelial cell differentiation
gene).
27
29. Gastric carcinomata also expresses high plasminogen activator
The UPA system is also associated with the development of
melanoma.
CATHEPSINS
They are all glycoproteins and contain essential cycteine
residue in their active site but they differ in their substrate
specifities and PH stability.
29
30. There are 11 cathepsins (B,C,F,H,K,L,O,S,V,W,X) and they are
synthesized as inactive precursors consisting of a signal
sequence a pro – peptide and a catalytic active mature region
Activation normally occur after cleavage of the amino
terminal region.
Cathepsin D is regulated by intracellular growth
factors, hormones and endogenous inhibitors and it is
induced in hepatomata ,thyroid cancer, bladder cancer, gastric
and colon carcinomata.
30
31. Cathepsin B (Myeloid precursor protein secretase APPS). It is
secreted in an inactive form of 42kD proform. Elevated levels
of cathepsin B is occur in
gliomata, lungs, pancreas, prostate, breast, and stomach
carcinomata
KALLIKREINS
They are a family of several single chain proteases. They
contain conserved serine proteases. Conserved disulfide
bonds
The expression of kallikreins is regulated steriod hormones.
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32. ENZYME TARGET STRUCTURAL
CLASS
TUMOR
MATRIX
METALLOPROTEINA
SES
MMP – 1
(INTESTINAL
COLLAVGENASES)
Collagen type
1,2,3,7 and 10
Simple hemopexin
domain
Head and neck
cancer
MMP – 2 Collagen 4,5,7,9,10 Gelatin binding Skin cancer, colon
cancer, stomach
cancer, ovarian
cancer
MMP – 7 (Matrilysin,
PUMP – 1)
Gelatin type
1,3,4,5
Minimal domain Gastric cancer and
colon cancer
MMP – 9 92KD
Collagenase type 4.
Collagen 4,5,7,9,10 Gelatin binding Skin cancer
32
33. ENZYME TARGET STRUCTURAL
CLASS
TUMOR
MMP – 10
Sromelysin
Laminin,fibronectin,
proteoglycan core
protein
Simple hemopexin
domain
Head and neck
cancer
FIBRINOLYTIC
PROTEINASES
Urokinase Type Plasminogen Breast cancer
melanoma
Plasminogen
activator tissue
type
Plasminogen Breast cancer
Plasminogen
activator plasmin
Laminin type 4
collagen
Thrombin PAR – 1 Pancreas
cancer, oral cancer
33
35. ENZYME TARGET STRUCTURAL
CLASS
TUMOR
CATHEPSINS
Cathepsin D Glioblastoma,
hepatoma,
melanoma and
thyroid cancer
Cathepsin B Amyloid β pro -
Urokinase
Glioblastoma, lung
cancer
Cathepsin K Breast cancer,
prostate cancer
Cathepsin S Elastin Astrocytoma
35
36. ENZYME TARGET STRUCTURAL
CLASS
TUMOR
OTHER PROTEASES
Elastase Elastin Colorectal
carcinoma, breast
cancer
PROTEASE
INHIBITORS
TIMP – 1 92 kD Collagenase
Type 4 intestinal
collagenase
stromelysin
TIMP – 2 72 kD Collagenase
Type 4
PAI – 1 Plaminogen
activator
36
37. SURVIVAL DURING INVASION
The binding of integrin (alpha 5,beta 1) to fibronectin induces
the expression of BCL – 2, which protect cells from apoptosis
during invasion
BIM and BMF released from the cytoskeleton of normal cells,
through the interaction between myosin and actin on the
contrary inhibits the anti – anoikis properties of BCL – 2 and
this initiates programmed cell death (apoptosis)
37
38. FAK signaling is also implicated in promoting cell survival
through its substrate PKB (Phosphtidylinositol 3 – kinase)
Cell – cell interaction through cadherin protect from apoptosis
through a pathway that depends on cytoskeletal integrity.
38
