Cancer Dormancy
8/28/08
Does Tumor dormancy Exist?
20-45% of breast cancer and prostate cancer will relapse years or
decades later after initial tumor removal – can not be explained by
continuous tumor cells proliferation – dormancy makes sense ;
Disseminated/cirulating cancer cells (DTCs, CTCs) can be detected
in 30% of breast cancer patients at the time of diagnosis in a large
study with 4703 patiens;
In some studies, all CTCs identified after surgery are negative for
Ki67 staining;
Aguirre-Ghiso JA, 2007, Nature Review Cancer; Braun S et al, 2005, NEJM; Muller V et al, 2005, Clin Cancer Res
Does Tumor dormancy Exist?
• In mouse models,
dormancy certainly
exists.
• With better technology,
you can find them and
follow them too.
M
NM
Macro-metastasis
Micro-metastasis
M4A4
62% mice form
mets from
orthotopic tumor
Single cells, to 1-4
cell culsters, mean
73
micro- can persist upto 6 months
NM2C5
0%
Single to 1-4 cells,
mean 50
Can be recovered as proliferating cells in
vitro; still tumorigenic in vivo at s.c and
fat pad(better), and still only form micromets
Goodison S, et al, 2003, Clin Cancer Res
MPIO(micron-sized iron oxide
particle)-label GFP tagged MDAMB-231BR cells;
Inject into left ventricle of mouse
Monitor tumor cells in the brain
with MRI.
Fate of the cells
Heyn C et al, 2006, Mag Res Medicine
Cancer Dormancy
• Cellular dormancy:
cells probably enter G0 –G1 arrest – cells are
truly inactive
• Tumor mass dormancy:
cell proliferation is counterbalanced by
apoptosis due or poor vasculature or immune
response to the tumor cells
cells are still active, just tumor as a mass can
not expand beyond certain size.
Potential mechanisms
• Tumor cells fail to recognize the environment,
therefore disrupting crosstalk between growth
factor signaling and adhesion signaling.
G0-G1 arrest
differentiation
senescence?
• Immunosurveillance
• Tumor cells fail to recruit blood vessles.
Microenvironment – story #1 integrin beta1
Nonmalignant
Tumorigenic
3-D
After 10-12 days in matrigel:
Weaver VM et al, 1997, JCB
Integrin beta 1
E-cad
S-1
T4-2 IgG
T4-2 beta1 blocking Ab
F-actin
nuclei
E-cad
beta-cat
Reversible!
Weaver VM et al, 1997, JCB
• When tumor cells fail to engage integrin
signaling (fail to talk with ECM), cells can
assume a differentiated phenotype, and undergo
growth arrest through induction of p21cip.
• In vitro – nothing to do with metastasis per se
Microenvironment – story #2 integrin beta 1
White DE et al, 2004, cancer cell
Conclusion
• In the primary tumor setting:
• Inactivation of integrin (fail to communicate with
ECM) render epithelial cells dormant – persist in the
tissue but fail to proliferate in vitro.
• These data hint that failure to engage integrin
signaling allows the cells to either differentiate or
become dormant.
• Not clear if true in metastatic dormant cells.
• Not shown in patients.
Microenvironment – story #3 uPAR
Reduce uPAR expression
Expected: reduced invasion
Unexpected: tumor become dormant for a while
Yu W et al, 1997,JCB
Although in vitro proliferation is not affected.
Similar % live or dead cells
Much reduced proliferating cells when reducing uPAR
Yu W et al, 1997,JCB
Met cells have strong ERK
activation but not uPARlow cells
Soluble uPA activates ERK pathway –time/conc.-dep
Aguirre-Ghiso et al, 1999 JCB, 2001 MCB
Adhesion on FN associates with
expression level of uPAR,
although no diff. in surface
expression level of alpha5 beta1
Co-IP of uPAR and beta1 integrin
Reduced pERK if disrupt uPAR and
integrin interaction using peptide.
ERK
Aguirre-Ghiso et al, 1999 JCB, 2001 MCB
conclusions
• Using cell lines that either metastasize or remain
dormant in chick CAM:
• uPAR seems to activated integrin (low uPAR,
integrins are there but not as active), to “talk” with
ECM.
• This induces strong ERK signaling.
• Fits the idea that diminished “talk” with the
microenvironment renders the cells domant.
• Patients: uPAR is a poor prognostic marker for breast,
lung, colon, esophageal and gastric cancer.
Microenvironment – story #4
CD82-DARC interaction as metastasis suppressor
AT6.1-vector
AT6.1-KAI1
Prostate cancer interact with endothelial
cells in KAI-1 dependent manner
DARC expression
– vessels only
Bandyopadhyay S et al, 2006, Nature Med
Interaction between KAI1 and DARC
results in reduced proliferation in
prostate cancer cell line
No diff. in primary tumor growth
Less met from DARC +/+ or +/- mice
Senescence?
Probably by downTBX2 and up p21Cip
Conclusion
• Suggests endothelial cells can function as one
of the metastasis-suppressive mechanism that
contribute to upregulation of p21Cip and
reduction of tumor cell proliferation.- dormant
• Maybe senenscence?
Microenvironment – story #5
Secreted Kiss function as metastasis suppressor
Full-length
No signal sequence – not secreted
Conditioned medium
C8161.9 human melanoma cells
Secreted Kiss blocks metastasis (iv model), but not
non-secreted form
Cells expressing Kiss
persist in the lung for
at least 120days but
fail to manifest into
full mets – induces
dormancy in the cells?
Extra information and hypothesis
• In these melanoma cells, could not detect the
receptor GPR54.
• See strong systemic anti-metastasis effect –
other organs: kidney, eye, bone.
• So maybe (just maybe) secreted Kiss function
through other common cells in the
microenvironment? (or different receptor on
the cells)
What is the cellular machinery that allows
the cells undergo dormancy?
Stress!!
p38
Oncogenic
ERK
Dormant
Meta.
D-HEp3
T-HEp3
AS24
LK25
High p38 signaling
correlates low ERK
signaling in these cells
Aguirre-Ghiso et al, 1999 JCB, 2001 MCB
ERK reporter
p38 reporter
Aguirre-Ghiso et al, 2004, Cancer Research
In another study by Rinker-Schaeffer’s group, identify JNKK1/MKK4 and
MKK7 as metastasis suppressor – using prostate cancer cell lines.
Fits broadly in the idea that stress signal may suppress tumor cells colonization.
Mechanisms regulating cellular
dormancy…
Environment:
• Tumor - ECM interactions:
integrin activation ERK vs p38
• Tumor cells – vasculature interaction
• Tumor cells – others?
Other speculations???
• How about contact inhibition?
Normal organ size control;
Cells retreat to G0-G1 arrest
And in fact, dissemination probably occurs early (as
well as later) during primary tumor formation
Clues from other organism?
Worms undergo diapause when the environment is not
suitable – p38 (sensing oxidative stress) induces
diapause; ER stress signal; DAF and IGF1 involved
in diapuse…
Plant seeds undergo dormancy.
Tumor mass dormancy
• Immunosurveillance - been shown in B cell
lymphoma mouse model
• Angiogenic dormancy