Tumors

Question 1

malignant transformation:

Answer 1

when a cell has become able to form a cancer, it is said to have undergone malignant transformation

Question 2

metastasis:

Answer 2

spreading of cancer cells thru the lymph or bloodstream to distant parts of the body other than the original site

Question 3

proto-oncogenes:

Answer 3

genes that normally contribute positively to the initiation and execution of cell division

Question 4

oncogenes:

Answer 4

mutant forms of proto-oncogenes that contribute to malignant transformation

Question 5

mutagens:

Answer 5

a chemical or physical agent that increases mutation rate

Question 6

carcinogens:

Answer 6

a mutagen that increases the risk of cancer cell formation

Question 7

How does cancer arise?

Answer 7

from a single cell that has accumulated multiple mutations in genes that are involved in cell multiplication and cell survival

Question 8

there are two types of genes that if mutated or mis-expressed can contribute to malignant transformation. name them

Answer 8

1. proto-oncogenes: normally function in either initiation or execution of cell division
2. tumor suppressor genes: these are genes that normally function to prevent unwanted proliferation of cells

Question 9

chemical carcinogens typically give rise to what type of mutations?

Answer 9

give rise to single base change mutations

Question 10

How can viruses cause cancer?

Answer 10

human oncoviruses infect cells and begin to express virally encoded proteins that can over-ride the cell’s normal mechanisms for regulating cell division

some viruses prevent the normal tumor suppression mechanisms of infected cells from operating; gives rise to abnormally-proliferating cells

Question 11

many tumor cells can be easily recognized and killed by what?

Answer 11

allogeneic CD8 T cells

Question 12

if a tumor cell from one strain of mice is injected into a mouse of a different strain, the tumor cells can be killed (much like a transplant rejection). what does this show?

Answer 12

tumor cells can be recognized by immune effector cells

Question 13

What is the difference in tumor specific antigens and tumor associated antigens?

Answer 13

antigens present on tumor cells but not on normal cells are referred to as tumor- specific antigens

antigens that are found on tumor cells, but are also found on normal cells (often in smaller amounts) are termed tumor-associated antigens

Question 14

What is the most common tumor antigens?

Answer 14

peptides bound to MHC class I molecules;

recognized by CD8+ T cells

Question 15

What are the surface determinants on tumor cells for?

Answer 15

recognized by antibody molecules (and B cell receptors)

Question 16

What experiment proves that the immune system can kill tumor cells if a tumor immune response can be generated?

Answer 16

mice can be effectively immunized by injecting irradiated tumor cells;

an anti-tumor immune response is produced that can prevent subsequent transfer of live tumor cells of the same type

Question 17

WRT HLA expression, how can tumor cells escape the immune response?

Answer 17

between 1/3 and 1/2 of the cells in a tumor have defects in expression of one or more of their HLA molecules (MHC class I molecules)

selective pressure for cells that do not present tumor antigens on their surface, and therefore cannot be recognized by CTLs

Question 18

tumor cells that do not express MHC class I cannot be recognized by effector CTLs. how are they killed?

Answer 18

killed by NK cells

Question 19

some tumors actually create a zone of immunosuppression around the borders of the tumor. How?

Answer 19

by producing cytokines that suppress or mis-direct immune responses

Question 20

How are monoclonal Abs used in tumor recognization and therapy?

Answer 20

tumor-specific mAbs can be used to detect tumors

tumor-specific mAbs can also be used to target tumor cells for destruction

mAbs conjugated to a toxin molecule can be injected into a patient. When the MAb:toxin conjugate binds to a tumor cell, the toxin molecule can be taken up by the cell and the cell is poisoned from the inside

Question 21

What is a drawback to monoclonal Ab treatments?

Answer 21

immune system will produce acquired immune responses specific for the foreign antibodies;

no further treatments with that antibody can be performed successfully.

Question 22

BOOSTING T CELL RESPONSES IS ANOTHER APPROACH TO IMMUNOTHERAPY. How is this done?

Answer 22

if T cells specific for tumor antigens can be isolated from a patient, they can be grown and expanded in vitro

this expanded population of effector T cells can then be injected back into the patient

Question 23

a recombinant DNA approach that has promise is to transfect tumor cells with cytokines or chemokines that either stimulate or chemattract dendritic cells to the tumor. What does this do?

Answer 23

this facilitates uptake and eventual presentation of tumor-specific antigens to naïve T cells