Cancer and the Immune System

Question 1

What is the incidence of cancer?

Answer 1

2 cause of death behind CV disease

Question 2

What are causes of cancer?

Answer 2

1) Lifestyle
2) Environmental pollutants
3) Genetics
4) Impaired immune surveillance

Question 3

When does cancer arise?

Answer 3

When multiple control systems are corrupted within a single cell

Question 4

What are the 2 basic types of control systems?

Answer 4

1) Systems that promote normal cell growth

2) Safeguard systems that protect against uncontrolled cell growth

Question 5

When does most cell proliferation cease in cancer?

Answer 5

When the cancer is full grown but there are exceptions…. Skin cells and cells that line mucous membranes must be continually replaced as these surfaces are under erosion due to constant wear and tear

Question 6

When do cells usually begin to proliferate inappropriately?

Answer 6

Usually due to a genetic mutation causing a protein mutation

Question 7

What are examples of gene mutation that causes a protein mutation?

Answer 7

1) Proto- oncogene- when mutated causes a cell to proliferate inappropriately
2) Oncogene
3) Tumor supressor gene- prevents tumors

Question 8

What is the estimates amount of mutations required to produce most common cancers?

Answer 8

Between 4 and 7 mutations

Question 9

How long does it take to accumulate multiple mutations?

Answer 9

A long time!

Question 10

What happens if a genetic mutation disrupts proteins that repair mutated DNA?

Answer 10

Insidious and can lead to a marked rise in accumulated mutations which increases the formation of cancer

Question 11

What happens in immunosuppressed individuals?

Answer 11

There is an increased incidence of lymphoma and virus associated with cancer

Question 12

What cancer is associated with AIDS patients?

Answer 12

Karposi sarcome associated with human herpes virus 8

Question 13

What cancer is caused by human papilloma virus?

Answer 13

Cervical caner

Question 14

What cancer is associated with chronic hepatitis B in about 20% of cases?

Answer 14

Liver cancer

Question 15

What percentage of viral infections contribute to all human cancers?

Answer 15

15-20%

Question 16

How can the immune system control cancer?

Answer 16

1) By destroying viruses that are known to transform cells
2) By eliminating pathogens and reducing pro-tumor inflammation
3) By actively identifying and eliminating cancerous cells (immunosurveillance)

Question 17

What is immunosurveillance?

Answer 17

The immune system continually monitors for and destroys neoplastic cells

Question 18

How does pro tumor influence the immune system?

Answer 18

Results in chronic inflammation and immune-mediated selection for malignant cells

Question 19

What is immunoediting?

Answer 19

Nuanced hypothesis that incorporated both protection against and promotion of tumor growth. It incorporates observations of both tumor-inhibiting and tumor-enhancing processes mediated by the immune system

Question 20

In humans with cancer, what is associated with longer survival with a tumor?

Answer 20

Higher lymphocyte counts

Question 21

What type of tumors is responsible for the majority of cancers?

Answer 21

Spontaneous tumors

Question 22

Are CTL’s and spontaneous tumors effective?

Answer 22

Probably not due to:
Traffic pattern issues
Conflict between self tolerance and surveillance
Unable to supply co stimulation

Question 23

Are CTL’s and cancerous blood cells effective?

Answer 23

More effective due to:
Traffic patterns of cancer cells in blood virgin T cells intersect
Some cancerous blood cells express high levels of B7 (co-stimulation)

Question 24

Are CTL’s and virus associated tumors effective?

Answer 24

They are probably limited due to hiding viruses associated with cancer. CTL’s are generally not effective

Question 25

What is the importance of macrophages and cancer?

Answer 25

May provide surveillance against some cancers.

Question 26

How do the hyperactivated macrophages provide surveillance against some cancers?

Answer 26

They secrete TNF and express it on their surface which can kill certain types of cancer. May work my preventing angiogenesis.

Question 27

How does abnormal expression of surface molecules on tumors provide surveillance against some cancers?

Answer 27

It may allow activated macrophages to differentiate between cancer cells and normal cells

Question 28

What are other ways can macrophages provide surveillance against cancer?

Answer 28

1) Quick acting (unlike CTL’s)
2) Recognize diverse target structures
3) Located out in the tissues where most tumors arise and therefore can intercept at an early stage

Question 29

RECAP: Name the 5 ways macrophages may provide surveillance against some cancers.

Answer 29

1) Hyperactivated macrophages secrete TNF and express it on their surface
2) Abnormal expression of surface molecules on tumors
3) Quick acting
4) Recognize diverse target structures
5) Located out in tissues where most tumors arise

Question 30

Can NK cells destroy cancer cells in vitro?

Answer 30

Yes

Question 31

What types of cells do NK cells target?

Answer 31

They target cells that express low levels of class I MHC molecule and display unusual surface molecules. They recognize diverse targets

Question 32

Are NK cells quick acting like macrophages?

Answer 32

Yes, they could take out wannabe cancer cells before they rev up

Question 33

Where do the NK cells stay until activated?

Answer 33

NK cells stay circulating in the blood like neutrophils until they are activated. They are activated during inflammation

Question 34

When is vaccination used to prevent cancer?

Answer 34

Used in virally associated cancer:

• Hepatitis B and liver cancer
• HPV and cervical cancer

Question 35

When is BCG vaccine used?

Answer 35

Injected in superficial bladder cancer and sometimes used in TB.