1. ACHARIYA ARTS AND SCIENCE COLLEGE
(AFFILATED TO PONDICHERRY UNIVERSITY)
DEPARTMENTAL SEMINAR
BIOTECHNOLOGY DEPARTMENT
Topic:-Molecular Mechanism Of Cancer Metastasis
Presentation by
Gopi Krishna Giri

2. Overview
What is metastasis?
Molecular mechanisms of metastasis
Signalling pathways involved in
metastasis
2

3. I) What is cancer metastasis?
Cancer defines as a population of cells that
have lost their normal controls of growth and
differentiation and are proliferating without
check.
Metastasis is the process by which a tumor
cell leaves the primary tumor, travels to a
distant site via the circulatory system, and
establishes a secondary tumor.
3

4. Forms of cancer metastasis
4

5. Preferential metastatic sites
Primary tumour
Common distant site (s)
Breast’ adenocarcinoma
Bone, brain, adrenal
Prostate adenocarcinoma
Bone
Lung small cell carcinoma
Bone, brain, liver
Skin cutaneous melanoma
Brain, liver, Bowel
Thyroid adenocarcinoma
Bone
Kidney clear cell carcinoma
Bone, liver, thyroid
Testis carcinoma
Liver
Bladder carcinoma
Brain
Neuroblastoma
Liver, adrenal
5

6. Reason for organ selectivity
Mechanistic theory: determined by the
pattern of blood flow.
“Seed and soil” theory: the provision of a
fertile environment in which compatible
tumor cells could grow
6

7. Determining factors
Appropriate growth factors or
extracellular matrix environment
Compatible adhesion sites on the
endothelial lumenal surface
Selective chemotaxis at which the organ
producing some soluble attraction factors
to the tumor cells
7

8. II) Molecular mechanisms of
metastasis
8

9. 5 major steps in metastasis
1.
2.
3.
4.
5.
Invasion and infiltration of surrounding normal host
tissue with penetration of small lymphatic or
vascular channels;
Release of neoplastic cells, either or single cells or
small clumps, into the circulation;
Survival in the circulation;
Arrest in the capillary beds of distant organs;
Penetration of the lymphatic or blood vessel walls
followed by growth of the disseminated tumor cells
9

10. 10

11. Stages of metastasis
Invasion : primary tumour cells enter
circulation
Circulation to the secondary site of tumour
growth
Colonisation : formation of secondary
tumour
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12. Tumor invasion
1. Translocation of cells across extracellular
matrix barriers
2. Lysis of matrix protein by specific
proteinases
3. Cell migration
12

13. Components of invasion
a) Matrix degrading enzymes
b) Cell adhesion
c) Cell motility
13

14. a) Matrix degrading enzymes
Required for a controlled degradation of
components of the extracellular matrix
(ECM)
The proteases involved in this process are
classified into serine-, cysteine-, aspartyl-,
and metalloproteinase.
14

15. MMP family
15

16. Matrix metalloproteinases (MMP)
16 members, subdivided into 4 groups,
based on their structural characteristics and
substrate specificities
Soluble and secreted groups; collagenase,
gelatinase and stromelysins
Membrane type (MT-MMP) group are
anchored in the plasma membrane
A zinc ion in the active centre of the
protease is required for their catalytic
activities.
16

17. Regulation of MMP
MMP is controlled by an increased expression on a
transcriptional level.
MMPs are calcium-dependent proteases, which are
synthesized as a inactive proenzymes and are
activated by the cleavage of a propeptide.
MMP activity is regulated by specific inhibitors, the
tissue inhibitors of MMP (TIMPs). Binding TIMP to
MMP is in a 1:1 stoichiometry.
MMP2 and MMP9, which cleave type IV collagen
the major constituent of basement membrane, are
believed to be of special importance
17

18. Serine proteases
Serine protease involved in ECM degradation are
plasmin, plasminogen activators and cathepsin G.
Plasmin is believed to be the most important
serine protease, firstly because its ability to
degrade several matrix components like gelatin,
fibronectin or laminin, and secondly by the
possible activation of numerous proforms of MMPs
by propeptide cleavage.
Plasmin is synthesized in its inactive proform,
plasminogen, which can be converted to plasmin
by plasminogen activator.
18

19. Plasminogen activator
Two main types : urokinase (uPA) and
tissue (tPA).
uPA is bound to the surface of tumor cells
by means of a specific receptor (uPAR)
There are specific inhibitors (PAI-1 and
PAI-2) for the PA.
19

20. Interaction between tumour cells
and the surrounding connective
tissue
20

21. Cell adhesion and metastasis
21

22. b) Cell attachment
1. Integrin: cell-matrix adhesion
2. E- cadherin/catenin adhesion complex:
cell-cell adhesion
22

23. 1) Integrin
Heterodimeric transmembrane receptors
consists of α and β subunits
Function to provide interactions between
cells and macromolecules in the ECM
Integrin can affect the transcription of
MMP genes
23

24. Integrin signaling
24

25. 2) E- cadherin and catenin
complex
Most important cell-cell adhesion
molecules
Reduce expression of E-cadherin and
catenin increase the invasiveness of
tumor cells
25

26. Cadherin-mediated cell-cell
adhesion
26

27. p120 catenin
27

28. 28

29. c) Cell migration
1. Small Rho GTPase family
2. Motility promoting factors
29

30. Small Rho GTPase
Stimuli
Cdc42
Rac1
GTP
GTP
Pak1
MLC Kinase
LIM kinase
Stress fibers
MLC Phosphorylation Cofilin
Contraction
Filopodia
Actin polymerisation
Detachment
Lamellipodia
30

31. Model of Rho GTPase
regulation
31

32. Regulation of Rho GTPase
32

33. Rho GTPase is required for the
transition of invasive phenotype
33

34. Signaling pathways related to
integrin and small GTPase
34

35. E-cadherin and Rho GTPase
signaling
35

36. Rho GTPase at different stages of
tumour progression
36

37. 2) Motility promoting factors
Hepatocyte growth factor/scattering factor
Insulin-like growth factor II
Autotaxin
37

38. HGF/scatting factor
Heterodimer of α and β chains
HGF normally acts as a paracrine growth
factor, but in tumor cells it can act as an
autocrine
HGF binds to the c-Met receptor and
activated the downstream effectors
38

39. HGF induce cell scattering and
invasion
39

40. Signalling pathways responsible for
MET-dependent invasive growth
40