Transcript Immune System and Cancer

Immune System and Cancer
J.club
07/29/03
What are NK cells?
A part of the native immune system, share a common early progenitor
with T cells but do not develop in the thymus
~ 10% of blood lymphocytes, defined by surface markers
(ex. CD56, NK 1.1, CD2, CD16)
Activated by IFN, IFN and IL-12
(IL-12 commonly used to activate NK cells in vitro)
Involved in early response
to infection with certain
viruses and intracellular bacteria
(first line of defense, giving CTLs
time to differentiate)
“Natural Killers”
NK discovered as tumor killer cells:
Mice were immunized against a tumor, then their lymphocytes tested
for ability to kill tumor cells in vitro.
But negative controls – lymphocytes from unimmunized mice or mice
Immunized against a different tumor – also killed tumor cells very well!
NK assay:
51Cr
release from YAC-1 cells
MHC/HLA review
NK receptor overview
KIR
CD94
+a/b
+c, e/h, f
NCR
NKG2d
NK receptors
Most inhibitory receptors
recognize MHC I molecules
2 groups:
•Killer Immunoglobulin Receptors (KIRs)
•C-type lectin receptors (CD94+NKG2 family member)
Both have activating counterparts, but inhibitory signals dominant.
Activation/inhibition depends on:
•KIRs - long cytoplasmic tail with ITIMs vs. short tails + adaptor with ITAMs
•C-type lectin receptors - NKG2 member: a/b activating, c, e/h, f inhibitory
NKG2d human and mouse ligands
RAE-1/H60 evidence:
•Tumors expressing RAE-1 or H60 are rejected, NK cell-dependent.
•Mice immune to re-challenge with the same tumor cells, even if
RAE-1/H60 are no longer expressed – a role for adaptive immune system
New activating receptor: NKG2d
•Low homology to other NKG2 receptors, an activating receptor
conserved between humans, mice and rats
•Expressed on NK cells, macrophages, / and / CTL’s
•Homodimer, forms an activating complex with DAP-10, which
contains SH2 domains and recruits PI3K
•Can override inhibitory signals from KIRs and C-type lectins
Killing pathways
(from Takeda et al, 2002)
Adhesion molecules may help NK get to tissue
•Human and rat NK cells synthesize fibronectin,
mAb’s against FN block NK cytotoxicity against YAC-1
•NK cells express 41 and 51 integrins, mediate adhesion to FN in an
in vitro assay
•NK cells express L-selectin, its expression is upregulated by IFN, IL-10
and IL-12
•IL-12 also promotes NK adhesion to P and E (endothelial) selectins
under flow conditions
•LFA-1
•N-CAM
Immune surveillance idea and NK cells
In 1909, Paul Ehrlich proposed that the immune system could repress
carcinomas. Idea was extended in 1957 by Burnet/Thomas – “immune
surveillance” as a way of maintaining tissue homeostasis.
NK cells a good candidate:
•Many virally infected and tumor cells express less MHC I, escape
CTL detection/killing
• NK cells kill MHC I – cells in vitro
•NK reject MHC I – tumor cells, not same cells MHC I+
(same experiment for mets.)
•Irradiated mice get MHC I – lymphocytes, rapid NK-mediated
disappearance
•Atomic bomb/ Chernobyl survivors have mutations in many different
genes, except HLA loss in T cells
Tumor/NK evidence in mice
Direct:
•NK cells kill MHC I - tumor cells in vitro
•Eliminate tumor cells from circulation of mice/rats
•Protect mice from MCA skin carcinogenesis
•CTL knockouts have OK control of carcinogen-induced sarcoma growth,
perforin knockouts (no CTL or NK activity) have deficient control
Correlative:
•A/J mice have low NK activity and high rate of lymphoma,
C57/BL6 mice have high NK cell activity and low rate of lymphoma
•Mice selected for low acute inflammatory response (AIR) are more
susceptible to skin carcinogenesis by DMBA/TPA, and have more lung
metastases than wt. or mice selected for high AIR
Tumor/NK evidence in mice
Drawbacks:
•No good data on protection from spontaneous tumors (except MCA)
•Good stimulation by blood cells but few other (ex. Not by low MHC I liver)
•In vitro models often activated by cytokines at far above physiological
levels
•NK cells require homing signals (MIP-1 for homing to CMV foci in liver)
•No good mouse model lacking NK cells
(until very recently: a group was using a granzyme A promoter to express
Ly49A cDNA, and got a mouse that’s specifically NK-deficient, both by
FACS and by functional assays
The mouse has impaired control of tumor growth/mets., confirmed NK
role by adaptive transfer)
Tumor/NK evidence in people
Direct:
•In vitro, IL-12 activated human NK cells are capable of killing MHCtumor cells
•Chediak-Higashi syndrome – impaired NK degranulation, susceptible to
highly metastatic lymphomas
Correlative in vivo:
•Patients on immunosuppressants get more blood tumors
•People with congenital or acquired immunodeficiencies have a
significantly higher incidence of malignancies (viral infection?)
•NK is impaired in cancer patients, by in vitro studies on YAC-1 and
IFN response
•High peripheral blood NK activity (in treated, apparently disease-free
patients) correlates with longer metastasis-free survival
NKT cells
A recently discovered subpopulation of  T cells that express NK
markers (ex. NK 1.1, Ly49 in mice), CD44, Ly6C
Originate in bone marrow, differentiate in the thymus
Express a limited set of T cell receptors, CD4+/DN (60%/40%)
CD1-dependent activation (MHC I – like proteins conserved in mammals)
Implicated in immunoregulation and tumor growth, although
not clear if alone or NK-regulated
CD1 ligand details
Sites of constitutive expression in mouse: thymus, liver, spleen, lung
NKT recognize CD1 bound to glycolipid
(experimentally used - -galactosylceramide, -GalCer)
NKT function
Specialized regulatory component of immune system?
•Secrete large amounts of Th1 and Th2 cytokines upon stimulation, fast
Th1 – inflammatory, IFN main cytokine, involves CTLs and macrophages
Th2 – humoral, IL-4 main cytokine, stimulates T-helper cells and Ab
production
•Can rapidly stimulate T and B cells in antigen-nonspecific manner
•Activate NK cells, macrophages, recruit dendritic cells
•Can induce Fas-mediated killing of CD1+ thymocytes
Experimentally activated by anti-CD3
NKT evidence in cancer
•Rag -/- mice (lack NKT, T and B cells) get more metastases than wt mice
with low IL-12 stimulation. Corrected by adoptive transfer of NKT cells.
•-GalCer is beneficial in preventing tumor growth/mets. in mice
(stimulation of dendritic cells to release IL-12 and activate NK?)
•IFN release also important (stimulate TRAIL expression on NK?)
•Important in resistance to MCA-induced fibrosarcomas (no exogenous
-GalCer or IL-12 stimulation)
•Purified NKTs cytotoxic to syngeneic MCA-induced tumor line
NK/NKT big picture:
Immune System
• Innate Immune Responses -- components:
Macrophage, Dendritic cells, Neutrophils,
Mast cells, Eosinophils, Basophils
NK cells, NKT cells
Complement system
Acquired Immune Responses
• B cells
• CD4+ T cells
• CD8+ T cells
Cancer Immunosurveillance Hypothesis
•
“It is an evolutionary necessity that there should be some
mechanism for eliminating or inactivating such potentially
dangerous mutant cells and it is postulated that this mechanism is
of immunological character” -- Macfarlane Burnet and
Lewis Thomos (1957)
•
Data disfavored the hypothesis: studies using nude mice
1) Osias Stutman used CBA/H background, look atMCA
carcinogen-induced tumor
wt/nude
nu/nu
7/39, 95days
5/27, 90days
2)10,800nu/nu ~ wt mice in spontaneous tumor develp.
Cancer Immunosurveillance Hypothesis
Data supporting the hypothesis
• INF-γ data: block, KO, DN IFNGR1,or
STAT-1 KO mice have more spon. Or
induced tumors ;
• Perforin-/- more prone to MCA-tumor
• Rag2-/- increased rate of spontaneous
tumor in aged mice
• Other KO mice researches
Cancer Immunosurveillance Hypothesis
Correlative data supporting the hypothesis:
• Immune-suppressed patients have higher
incidence of melanoma, lung cancer;
• Positive correlation between tumor infiltrating
lymphocyte response and increased survival
(melanoma, breast, colon, prostate…)
Cancer Immunoediting
Acquired Immune System?
Not enough!
• CD8-/- mice seems to have
similar rate of MCA induced
tumor to WT; (low MHC I!!)
• CD4-/- mice can reject syngeneic tumor graft
while CD8-/- can’t;
• Rag2-/• In PND patients, CTLs targeting neuornal
antigen cdr2 seem to protect the patients from
tumor growth.
Innate Immune Responses and Cancer
--- Inflammation and Cancer
• Again, the hypothesis that “tumor: wounds that fail
to heal” is around for a long time. Virchow
hypothesized that the origin of cancer was at sites
of chronic inflammation. –1863
• But, is it true? Is inflammation helping or
hindering tumor growth?
Innate Immune Responses and Cancer
--- Inflammation and Cancer
•Again, like everything else, two opposite views:
1) Inflammatory infiltrations contribute to tumor
growth by inducing DNA damage, providing
growth and surviving factors, angiogenic/
lymphangiogenic factor, and proteases; -- “Foes”
2) Inflammatory infiltrations help to kill
transformed cells, therefore limiting the growth
of tumor. – “Friends”
Innate Immune Responses and Cancer
--- Inflammation and Cancer
• Data supporting “Foes”
1) Association between chronic inflammation and cancer risk
Malignancy
Inflammatory stimulus
Bladder
schistosomiasis
Cervical
papillomavirus
Colorectal
inflammatory bowel disease
Pancreatic
chronic pancreatitis
Lung
bronchitis
etc…
Coussens LM and Werb Z, Nature, 2002, 420:860
Balkwill F and Mantovani A, Lancet, 2001, 357:539
Inflammation and Cancer
Cellular components
Polymorphonucleates (PMNs)
Chemokines (IL8, IP-10, MIG,
MIP-1a,b etc)
Recruit TAMs
VEFG
MMPs
Angiogenesis
Mast cells
Tryptase
Chymase
TFN-a,
VEGF,
FGF-2,
IL-8
Angiogenesis
ECM remodeling,
Facilitate migration
Macrophages (TAMs)
Angiogenesis
Thrombospondin-1
IL-2
IFN-g
IL-12
Kill tumor cells
IL-10
(tumor
as well)
CTLs
MMPs, uPA
TGF-b1
TNF-a
PDG
bFGF IL-1
TGF-a
IGF-I/II
ECM remodeling,
Facilitate migration
Tumor growth
Inflammation and Cancer
• Data supporting “Friends”
1) Individual cytokines been shown to mediate
tumoricidal activity (TRAIL);
2) Activated macrophages mediate tumor rejection;
3) Some report says TAM positively correlate
disease-free probability after surgery (while
others report not informative, both prostate
cancer);
Why all these conflicting data?
• They are looking at different stages;
Csf1op/csf1op(do not express CSF1 which recruits MAPs): does not
affect the incidence or the growth of the primary tumors, but delayed
the dev. to invasive, metastatic carcinomas.  2 stages: CSF-1
promote the later stage. - Lin EY et al., 2001
Why all these conflicting data?
• Depend on the type of tumor and the stage
of tumor– secrete cytokines, chemokines to
attract leukocytes,actively involved in the
modulation of immune responses (Th1 vs.
Th2 etc..)