Tumor Biotherapy

肿瘤生物治疗

Limin Zheng

E-mail: zhenglm@mail.sysu.edu.cn

60. Gene therapy ( 基因治疗）61. Cancer vaccines ( 肿瘤疫苗 )

62. Cell transfer therapy ( 免疫细胞 )

63. Antiangiogenesis agents ( 抗血管生成 )

64. Focused ultrasound

65. Antisense inhibition of gene expres.

DeVitaDeVita Cancer: Cancer: Principles and Practice of OncologyPrinciples and Practice of Oncology

Part IV: Newer Approaches in Cancer TreatmentPart IV: Newer Approaches in Cancer Treatment

(most of them are tumor biotherapy)(most of them are tumor biotherapy)

Most active research area for cancer treatment

Hundreds protocols are in clinic trials

Why tumor Bio-therapy?

Current anti-tumor therapy used in Clinic:

Surgery: primary tumor, No metastases

Radiation ： surface, small and localized tumors

Chemotherapy: liquid tumor, metastases

Tumor Bio-therapy

Problems with chemotherapy: • Most drugs target nucleic acid

synthesis or mitosis, affect both tumor

and normal dividing cells, cause side-

effects on patients.

• Tumor cells: genetic instability,

heterogeneous, drug-resistant cells can

survive and grow

• Abnormal vessel structures & high

pressure in tumor resulted in lower

drug concentration in the lesion.

Tumor Bio-therapy

Influence of specific genesAntisense oligo or SiRNA,Gene therapy （ deliver target genes into tumor cells through vector)

Immuno-therapyTumor vaccines, Cytokines, Antibodies,

Anti-Angiogenesis Signal transduction: More active in Cancers

e.g. STI-571 (inhibit Bcr-Abl tyrosine kinase)

Gene Therapy: A Brief HistoryGene Therapy: A Brief History

Jesse Gelsinger ，1999

Ashanti de Silva ， 1990

Alain Fischer ，2003

1990 Ashanti de Silva ， USA

(ADA 所致联合免疫缺陷）1999 Jesse Gelsinger ， USA

2003 Alain Fischer ， France

2003 Adrian Thrasher ， UK

Gene Therapy• Genetic Disease ， single gene related• Present: most in Tumor (Multiple genes)• Method Ex vivo ： modify target cell in vitro

In situ ： directly introduce into local tumors（ most commonly used; p53-AV ）In vivo ： injected into blood (immune-genes)

Key ： target gene; vector; efficiency

Target Genes ：1. regulate immune response: cytokine, tumor Ag … etc

2. Differential expressed: TSG, apoptosis, angiogenesis etc.

How to introduce Genes into cells:

1. naked DNA ， liposome ， receptor …

2. Virus vector: replicate-deficient

(for transfection; no replication in human)

widely used: adenovirus (AV), AAV, Retrovirus

Obstacles in Gene Therapy - Obstacles in Gene Therapy - vectorvector

The major problem is the carrier （ vector ） ,not the Genes

Lack the efficient and specific vector. The most widely used vector is virus vector

(adenovirus 腺病毒载体 ) Major drawback of AV vector is

High immunogenecity andlow specificity for tumors

High immunogenecity of vectorHigh immunogenecity of vector

载体免疫原性强和靶向性差

Immunogenecity of Adenovirus

Adenovirus

Target - specificity

The problem with Gene therapy is mainly due to

vector (immunogenic and low specificity for tumor)

Tumor Bio-therapy

• Influence of specific genesAntisense oligo or SiRNA,Gene therapy

• Immuno-therapyTumor vaccines, Cytokines, Antibodies…

• Angiogenesis ( 抗血管生成 ):block new blood vessel （血管） formation

• Signal transduction: More active in Cancerse.g. STI-571 (inhibit Bcr-Abl tyrosine kinase)

The elimination phase of Cancer Immunoediting

Dunn et al, Nature Immunology, 2002; 3:991Dunn et al, Nature Immunology, 2002; 3:991

Effective immune responses eliminate

tumor

Tumors must escape from immune

recognition

Dunn et al, Nature Immunology, 2002; 3:991Dunn et al, Nature Immunology, 2002; 3:991

Mechanisms with host immune system

Ignorance: Immune system does not recognize t

he low levels of TAA at early phases of tumor

Tolerance of T cells to TAA, resulted from T-cel

l anergy or deletion (caused by host APC, T-reg)

Suppression of T cells: tumor-derived factors, i

mmunosuppressive myeloid cells or T-reg

Defects in antigen presentation by professional a

ntigen-presenting cells

Tumor Vaccine （ treatment, not prevention)Cell based vaccine: Best and most widely used so far

tumor cell based vaccine: hard to get enough cells;

DC ( 树突状细胞） based vaccinewidely used in clinic

Anti-tumor effector arms of the immune response

Tumor vaccines:Use Dendritic cells, the most powerful APC, to elicit anti-tumor immune responses

DC

DC

Tc

Interaction between DC and lymphocytes

DC uptake tumor cells, digest and processed tumor Ag into smaller peptide, form a complex with MHC, and present to the effectors ( 效应细胞 ).

Two Critical factors that affect DC vaccine1. Antigen loading2. Stimulating effective anti-tumor imm

unity (high affinity CD8+ CTL)

Ex vivo loading of DC with tumor Ag

Some Facts about Tumor Antigens

• Complete repertoire of tumor Ags and their

encoding genes is far from being fully

defined.

• The gene profiles from different types of

cancers or even from the same type in

different individuals are significantly

diversified.

• Only a small fraction of genes have been

repeatedly cloned from different cDNA

libraries prepared from distinct, or even the

same type of cancer in different individuals.

• Use a single Tumor antigen to load DC, can easily generate tumor cells that loss this Ag (immune pressure/selection)

• So, whole cells antigens are used in

most studies/clinical trials.

• Include: tumor cell lysates, apoptotic tumor cells, necrotic tumor cells, tumor-DC fusion

Adaptive immune responses can be divided into

two related activities—recognition and response.

require co-operation between Lymphocytes and

Ag presenting cell (APC, 抗原递呈细胞 )

Activation of T cells by dendritic cells

Antigen-presentation alone is NOT sufficient

to trigger immune response

The host immune response is tightly regulated by

1. Inhibitory (抑制 ) signals (e.g for NK cells)

2. Co-stimulatory (共刺激 ) factors (two signals):

without them, Ag presentation resulted in

Anergy (无反应 ) or immuno-tolerance (耐受 )

3. Danger Signals

危险？自己人？抗原

处理抗原摄取抗原

S1

S2

效应细胞APC 免疫应答

APC 双信号

?

Can we use adjuvant ( 佐剂） to activate APC,

(increase the co-stimulatory signals),

during the Ag loading?

Tumor Vaccine: Limited success obtained in clinic, more challenges remain

Other Vaccines:• DNA vaccine• Protein/peptide vaccine (8-12 AA): tumors

may not express peptide (heterogeneity 异质性 )

• Others: virus, xenogeneic ( 异种） vaccine etc

Get more “fighter”?

culture immune cells in vitro (>1010)

Problem:

functional activity? Reach the tumor?

In vivo, only high affinity CD8+ CTL can response to low levels of Tumor Ag, proliferate, and provide protective immunity;

Generation of these CTL dependent on the expression of co-stimulatory molecules on DC

Thus ， effective loading of tumor Ag, helping the maturation and expression of co-stimulatory molecules on DC simultaneously ( 同

时） are the dreams of tumor-immunologists.

Cytokines:• Interferon ( 干扰素 ), activate NK cells, M

• IL-2 ， IL-12: activate T-cells;• TNF: direct or via M and CTL to kill tumor

These cytokines are Not specific for tumor cellsUsually need high doses; with side-effectsMainly used as assistant therapy

Antibody: several Ab are in clinic use(e.g., for Her-2 in breast cancer)

篦麻毒素

Problems in using Antibody to treat

cancer:

1. Difficulty of Ab to penetrate into

solid tumor

2.Only minority of tumor cells

express the targeted Ag, due to

heterogeneity of tumor cell

population

3. Blocking effect of high circulating

tumor Ag

4. Formation of anti-IgG Ab and

toxicity of immune complexes

Cancer immunotherapy: moving beyond

current vaccinesNATURE MEDICINE 2004 ， 10 ： 909-915

Great progress has been made in the field of tumor

immunology in the past decade, but .......

In our cancer vaccine trials of 440 patients

(NCI), the objective response rate was low

(2.6%), and comparable to the results

obtained by others.

Promising, Great efforts still needed