19 Cancer and the Immune System

Question 1

What is cancer?

Answer 1

Cells that no longer respond to normal growth control factors give rise to clones of cells which lead to tumors

Question 2

True or False: benign tumors are capable of indefinite growth and invade healthy surrounding tissue

Answer 2

FALSE: these are malignant tumors, also known as cancer

Question 3

What is metastasis?

Answer 3

Small clusters of cancerous vessels that have been dislodged from a tumor, has invaded blood/lymphatic vessels, and carried to other tissues to proliferate

Question 4

Necessary characteristics of cancer cells

Answer 4

• stimulate their own growth
• ignore growth-inhibiting signals
• avoid death by apoptosis
• develop a blood supply (angiogenesis)
• leave site of origin to invade other tissues
• replicate continuously to expand numbers
• evade/outrun immune response

Question 5

What is transformation in the context of cancer? How does it come to be?

Answer 5

Change that a normal cell undergoes when becoming malignant. Can come to be by:

• radiation
• carcinogens
• viruses
• expression of oncogenes

Question 6

What is an oncogene?

Answer 6

gene that encodes a protein capable of inducing cellular transformation

Question 7

Explain the difference between v-onc and c-onc oncogenes

Answer 7

v-onc: oncogenes derived from viruses

c-onc: proto-oncogenes in normal cells, NOT made from viruses

Question 8

Tumor-specific antigens (TSAs)

Answer 8

• uncommon
• unique to tumor cells ONLY
• may result from mutations that generate altered cellular proteins through chemically or physically induced methods or virus induced methods
• novel peptides made that are presented with Class I MHC
• carcinogenic causes: methylcholanthrene and UV light

Question 9

Tumor-associated antigens (TAAs)

Answer 9

• common
• NOT unique to tumor cells
• may be antigens normally expressed on fetal cells, and immune system can’t react to them properly
• not normally expressed on adult cells
• ex. oncofetal and oncogen proteins as tumor antigens

Question 10

What is the immune response to cancer?

Answer 10

CD8+ T cells recognize and kill cells that express foreign peptides while Abs target tumor antigens
Additional help: NK cells and macrophages

Question 11

How do cytokines aid in battling/controlling cancer?

Answer 11

All interferon types enhance tumor-cell removal activities. Il-12 encourages DCs to activate TH1/CTL responses

Question 12

True or False: inflammatory responses can promote cancer

Answer 12

TRUE

Question 13

How do tumors evade the immune system?

Answer 13

1. reduced MHC expression in tumor cells
2. tumor cell subverts apoptosis signals by upregulating anti-apoptotic mediates and expressing mutated/absent death receptors
3. may provide poor costimulatory signals, leading to clonal anergy

Question 14

What are the 4 categories of cancer drug therapies?

Answer 14

1. Chemotherapy: block DNA synthesis/cell division
2. Hormonal therapy: interfere with tumor-cell growth
3. targeted therapy: target small molecule inhibitors of cancer
4. immunotherapies: induce/enhance anti-tumor immune response

Question 15

True or False: Tumor-specific T cells can be expanded and reintroduced into patients

Answer 15

TRUE