Notes on Tumour immunology

1. Tumor Immunology
Lilian Nkinda BSc MSc
Department of Microbiology and Immunology

2. Tumor Immunology
→Tumor-immune system interaction
Questions:
• Does immune system play a role in the
control of cancer?
• Are sufficient tumor targets (antigens)
available?
• Can immune system be utilized to attack
cancer?
• What are the obstacles for effective cancer
immunotherapy?

3. 1.Does immune system play a role in the
control of cancer?
• Increased cancer incidence in immuno-
compromised patients.
• Occasional spontaneous regressions of
cancers in immunocompetent hosts.

4. Immune system role in controlling cancer
Nature 2001, 410: 1107

5. ARE TUMORS IMMUNOGENIC?

6. 2. Tumor Antigens
• Tumor-specific antigen: Antigen that are expressed on
tumor cells but not on normal cells; some of these antigens
are unique to individual tumors, whereas others are shared
among tumors of the same type.
• Tumor-associated antigen: Tumor antigens that are also
expressed on normal cells; these antigens are normal
cellular constituents whose expression is aberrant or
dysregulated in tumors
• The modern classification is relies on the molecular
structure and source of the antigen

7. Tumor Ags arise from many ways:
(1) Mutations or translocations on self genes
(2) Abnormal expression of self gene products
(3) Reactivation of germ cell genes
(4) Viral oncogenes

8. Type of antigen Examples of human tumor antigens
Products of oncogenes,
tumor suppressor genes
Oncogenes: Ras mutations (∼10% of human carcinomas), p210
product of Bcr/Abl rearrangements (CML), overexpressed Her-
2/neu (breast and other carcinomas)
Tumor supressor genes: mutated p53 (present in ∼50% of
human tumors)
Products of overexpressed
genes
Tyrosinase, gp100, MART in melanomas (normally expressed in
melanocytes)
Products of oncogenic
viruses
Papillomavirus E6 and E7 proteins (cervical carcinomas)
EBNA-1 protein of EBV (EBV-associated lymphomas,
nasopharyngeal carcinoma)
SV40 T antigen (SV40-induced rodent tumors)
Oncofetal antigens Carcinoembryonic antigen (CEA) on many tumors, also
expressed in liver and other tissues during inflammation
Alpha-fetoprotein (AFP)
Glycolipids and
glycoproteins
GM2 GD2 on melanomas
Differentiation antigens
normally present in tissue of
origin
Prostate-specific antigen
Markers of lymphocytes: CD10, CD20, Ig idiotypes on B cells

9. Tumor Markers
Tumor markers : are
Tumor antigens
They are either or
Tumor products
(enzymes and hormones)
Gene expression
found in body fluids or tissues of patients
They are used for diagnosis and follow up the
response to therapy, or recurrence

10. Tumor markers -Tumor antigens
1) Alpha fetoprotein antigen (AFP) in cases of hepatoma, germ
cell tumor
2) Carcinoembryoinic antigen (CEA) in gastrointestinal tumors,
tumors of biliary system and cancer breast
3) Cancer antigen 125 (CA 125) in ovarian carcinoma
4) Cancer antigen 15-3 (CA15-3) in breast cancer
5) Cancer antigen 19-9 in colon and pancreatic tumor
6) Prostatic specific antigen (PSA) in prostatic tumors

11. Tumor marker-Tumor products
a) Hormones :
- β-Human chorionic gonadotrophins (β-HCG) are
secreted in cases of choriocarcinoma, testicular
cancer
- Thyroxin (T3 & T4) in cases of cancer
of thyroid gland
b) Enzymes :
- Acid phosphatase enzymes in cases of cancer
prostate
- Alkaline phosphatase, lipase and amylase
enzymes in cases of cancer pancreas

12. Tumor marker –Genes/DNA
• 21-gene signature –Breast cancer, to
evaluate risk of recurrence
• 70-gene signature (Mammaprint), to
evaluate risk of recurrence
• BCR-ABL gene fusion – chronic myeloid
leukemia- confirm diagnosis and monitor
treatment

13. Cancer Immunosurveilance
• Hypothesis was first proposed by Ehrlich in
1909, and modified by Thomas and Burnet in
1957.
• Immunosurveilance: the immunological
resistance of the host against the development of
cancer,
• Also referred to “cancer immunoediting”
encompassing 3 phases: elimination, equilibrium
and escape.

14. .ç

15. Immune responses to cancer

16. Cells that mediate innate immunity
to tumor cells

17. Adaptive responses
CTL destroy cancer cells by perforating the membrane with enzymes or by
triggering an apoptotic pathway, IFN –Y inhibit angiogenesis
Cytotoxic T Cells

18. killing of tumor cells by CD8+ CTL

19. CD4 T cell
CD4 T cell secrete Th1 and Th2 cytokines

20. Dendritic cells
Dendritic cells [IFN-producing killer DC] (IKDC):TRAIL& perforin- tumor cell lysis
via T cells; IFNγ-angiogenesis

21. Natural killer cells
• NK cells directly kill many
types of tumor
cells,especially cells that
have reduced class I MHC
expression and can escape
killing CTLs.
• engagement of inhibitory
NK cell receptors such as
KIR and CD94/NKG2 by
class I MHC molecules
delivers an inhibitory signal
that counteracts the
activation signa

22. NKT
NKT- TRAIL/perforin- tumor cell lysis, IFNγ-
angiogenesis

23. Macrophage
Macrophages: antigen presenting

24. Cytokines
• By regulating the innate immune system: NK cells,
macrophages, and neutrophils; and the adaptive immune
system, T and B cells
– IFN-α -- upregulating MHC class I, tumor antigens, and
adhesion molecules; promoting activity of B and T cells,
macrophages, and dendritic cells.
– IL-2 -- T cell growth factor that binds to a specific tripartite
receptor on T cells.
– IL-12 – promoting NK and T cell activity, and a growth factor for
B cells
– GM-CSF (Granulocyte-monocyte colony stimulating factor) --
reconstituting antigen-presenting cells.

25. Plasma cell

26. Antibody mechanisms
• Direct attack: blocking growth factor receptors, arresting
proliferation of tumor cells, or inducing apoptosis.-- is not
usually sufficient to completely protect the body
• Indirect attack: -- major protective efforts
ADCC (antibody-dependent cell mediated cytotoxicity )--
recruiting cells that have cytotoxicity, such as monocytes
and macrophages.
• Complement dependent Lysis -- binding to receptor,
initiating the complement system, 'complement cascade’,
resulting in a membrane attack complex, causing cell
lysis and death.

27. Mechanisms of antibody mediated anti
tumor effects
Activation of complement
ADCC
Blocking growth factor
Induction of apoptosis

28. Evasion Mechanisms
Privileged sites
• Some tumors arise in sites or locations like the eyes and
central nervous system inaccessible to potent immune
attack.
• Factors secreted by tumors cells create a physical
barrier to immune attack
Tolerance induction
• through re-expression of embryonic tumour associated
antigens (TAAg) or expression of novel antigens on
normal cells.
• TGF-, prostaglandin E2 generalized inhibition of
immune response and local anergy or tolerance in
tumor specific CTLs is associated with colorectal
carcinoma, prostate adenocarcinoma and glioblastoma.

29. Reduced immunogenicity
• Non-immunogenic tumors appear gradually
and persist while immunogenic ones emerge
rapidly and are eliminated faster.
• Down-regulation of MHC antigens promote of
tumour growth and proliferation.
Antibody mediated modulation
• Surface membrane changes/capping on the
tumor cells. Antibodies form immune
complexes with the surface tumor associated
antigens which then move towards the edges
or periphery of the tumor cells involving the
“capping” phenomenon.They are
subsequently either endocytosed or shed off.

30. Interference with antigen presentation
• Interference with antigen presentation
through down regulation of MHC Class I
molecules leads to protection of
neoplastic cells against CTL killing.
Expression of FasL molecules
• Binding of ligand (FasL) or anti-Fas
antibodies to Fas leads to apoptosis of
the Fas bearing cells.

31. • Expression of Fas molecules on
neoplastic cells induces apoptosis of
FasL expressing T cells that infiltrate
the tumors and escape CTL damage,
thereby promoting their growth.
• Apoptosis resistance: over expression
of Bcl-2

32. Expression of HLA-G molecules
• Expression of HLA-G antigens by tumor
melanoma cells, glioma and skin
malignancies protects against NK cell
cytoxicity.
Immunosuppression
• Blocking factors including immune
complexes may mask surface tumor
antigens or prevent cytotoxic cells or
cytotoxic antibodies.

33. • Immunosuppressive factors such as
prostaglandins and alpha-fetoproteins are also
produced and promote tumor growth.
• Defective cellular mechanisms during
pregnancy may exacerbate various
transformed and neoplastic cells leading to
increase in the frequency of virus-induced
tumours such as Burkitt’s lymphoma, genital
warts, mammary cancer, cervical
carcinoma, hepatomas and adenomas.

34. • Cancer cells grow faster than they can be killed.
• NK-cells have limited capacity for clonal
expansion.
• Altered glycosylation masks TSA recognition.
• Cancer cells lose contact inhibition and
requirement for attachment and can rapidly
spread by blood or lymph to other sites (liver,
lung, brain, etc).

35. Loss/down-regulation of HLA Class I
• Total loss: β2 microglobulin mutation,
alteration in antigen processing machinery
• Haplotype loss: LOH in chromosome 6
• HLA allelic loss: mutations of HLA class I
genes
• HLA-A, B, C locus down-regulation:
alteration of transcriptional factors
• Compound phenotype: 2 or more
independent mechanisms

36. Down-regulation, mutation or loss of
tumor antigens
• Tumor antigens (TA)
• Tumor associated antigen (TAA)
–complete loss
–Down-modulation

37. Loss of co-stimulation
• Costimulatory molecules B7 1
– B7.1(CD80)
– B7.2(CD86)
– CD40 B7 family
• CD27, CD30
• 4-1BB
• OX40
• ICAM-1

39. Immunosuppressive cytokines
• IL-10 inhibits antigen presentation and IL-
12 production.
• TGF-beta induces overproduction of IL-10
• VEGF (vascular endothelial growth factor),
avoid immune recognition, inhibit the
effector function, prevent T cell activation
& cytokine production

40. Induction of Immunosuppressive cells
• CD4+CD25+ T cells (constitute 5-10% of CD4+ T cells):
immunological tolerance to self-antigens, inhibition of T
cell proliferation.
• Gr1+CD11b+ myeloid cells:
Expressing the granulocyte-monocyte markers
Gr1+CD11b+,
accumulate in spleens, lymph nodes and blood of tumor
bearing mice.
• Inhibiting antibody production, CTL generation, T cell
function, lymphocytic proliferation, CD3 ζ chain
expression

41. Other suppressive factors
• IDO (Indoleamine 2, 3-dioxygenase):
expressed in most human tumour tissues
and splenic DC subsets, leading to
blockage of proliferation of T cells
• ganglioside (sialic acid containing
glycosphingolipids)

42. • The tumor TSAs are usually weakly immunogenic.
• The early response to low amounts of TSAs may
be slow to start or expand in quantity and affinity.
• The Tc-cell mediated cytotoxic response to TSAs
may be weak, low affinity or absent.
• The immune response to TSAs in anergic patients
with established tumors can’t be augmented.
• Therefore the immune system may NOT reject a cancer!
IF ALL CANCER CELLS ARE IMMUNOGENIC WHY IS CANCER
SUCH A BIG PROBLEM?

44. • Mechanics -- surgery,1600BC
• Physics -- radiotherapy,1896
• Chemistry -- chemotherapy,1942
• Biology -- immunotherapy,1976
Current strategies to combat cancers

45. Cancer Immunotherapy

46. Immunotherapy of cancer
• Passive immunotherapy:
– Antibodies (standard therapy in certain
cancer)
– cytokines (e.g. IL2/IL15, IFN-alpha)
– Cells (Adoptive transfer of autologous T cells)
• Active immunotherapy:
– Allogeneic bone marrow transplantation
– Specific tumor vaccines (i.e. peptides,
idiotype vaccine etc)
– Assisted antigen presentation (DC)

50. Current Immunotherapeutic
strategies in clinic or clinical trials
• Antibody Therapy
• Cytokine Therapy
• Adoptive Therapy
• Vaccination
• Combinational therapy

51. Antibody therapy of cancer
1.Rituximab(anti-CD20)-B-cell non-
Hodgkin’s lymphoma
2.CAMPATH 1H (CDw52)-CLL,
Prolymphocytic leukemia
3.Bevacizumab(VEGF)-metastatic
colorectal cancer
4.Trastuzumab(HER2/NEU)-breast cancer
5.Edrecdomab(EPCAM-1, KSA)-Colon
cancer

53. Adoptive T cell therapy of cancer
• The most promising immunotherapy for solid tumors. >50% of
patients with metastatic melanoma refractory to other therapies
obtained objective responses
Advantages
• High numbers of T cells can be generated in vitro
• T cells are activated in vitro, therefore bypass immune tolerance
• Select high avidity, antigen specific T cells
• Manipulate the host
Problems
• Labor intensive, technically demanding and expensive
• Adoptively transferred T cells fail to persist
• Tumor evasion

54. Cytokine therapy of cancer
• IFN-alpha: 90% hairy cell leukemia
• IL-2: Renal cell carcinoma, melanoma
• IL-15?

55. Obstacles of current T cell-based therapy
of cancer
1.Self-tolerance
2.Suppressor cells
– Myeloid suppressor cells (MSC)
– Granulocyte suppressors (GS)
– TR (CD4+CD25+)
– Ts: Qa-1-restricted
– Tr1: TGF-β producer (class II-restricted)
– Th3: IL-10 producer (class II-restricted)
– NKT: (CD1d-restricted) IL-13 producer
3. Immune evasion

56. Antitumor Vaccines
• Administration of some form of antigen
to induce a specific anti-tumour
immune response.
• e.g. Gardasil® vaccine– Human Papilloma
Virus (HPV) induced cervical cancer

57. Advantages of Immunotherapy
for cancer
• Cancer cells are immunogenic
• Single cell kill
• Migrate to tissue
• Memory
• Specific
• Life-long protection

58. Thank you