Chapter 20: Cancer

Question 1

What is cancer?

Answer 1

result of genetic alteration (mutations) that allow a cell to survive and divide when it should not

Question 2

What are the two properties of cancer cell?

Answer 2

1. Proliferate independent of normal constraints
2. Invade and colonize areas normally reserved for other cells

Question 3

What are the three types of cancer cells?

Answer 3

1. Benign
2. Malignant
3. Metastasis

Question 4

What are benign tumor

Answer 4

cells that remain cluster in a single mass but are not invasive

Question 5

What are malignant tumors?

Answer 5

invasive tumor

Question 6

What does it mean for a tumor to metastasis?

Answer 6

Tumor break off and colonize different area

Question 7

What are the factors that can cause cancer?

Answer 7

Environment
Life style
Genetic predisposition
Birth place
Virus infection

Question 8

What does the conversion of normal cell to cancerous cell require?

Answer 8

multiple mutations

Question 9

Why does the chance that a cell becoming cancerous increase greatly with age?

Answer 9

cells are continually experiencing accidental changes to their DNA—which accumulate and are passed on to progeny cells when the mutated cells divide

Question 10

What is genetic instability?

Answer 10

mutations that interfere with the accurate replication and maintenance of the genome and thereby increase the rate at which mutations accumulate.

Question 11

How does sequential accumulation of tumor lead to cancer?

Answer 11

at each step, a mutation can enhance a cell’s ability to proliferate, or survive, or both, so that its progeny become a dominant clone in the tumor.

Question 12

What are the two main class of gene critical for cancer?

Answer 12

Oncogene and tumor surpressor gene

Question 13

What are oncogene?

Answer 13

mutated gene that has the potential to cause cancer

Question 14

what are proto-oncogene

Answer 14

The normal form of the oncogenes
ex: ras

Question 15

What are Tumor-suppressor genes

Answer 15

gene that regulates a cell during cell division and replication
ex: p53

Question 16

What might happen if ras is mutated?

Answer 16

The oncogene is hyperactive, causing excess cell survival or proliferation

Question 17

What happens if one of the p53 gene is mutated?

Answer 17

There will be no effect because p53 mutant are recessive. No effect is done unless another mutation comes in

Question 18

What are the three ways a proto-oncogene can be converted to an oncogene

Answer 18

1. Mutation in coding sequence
2. Gene Amplification
3. Chromosome Rearrangement

Question 19

How can virus cause tumor?

Answer 19

the src gene in src containing virus triggers uncontrolled growth in abnormal host cells.

Question 20

What distinguishes cancer cells from normal cells?

Answer 20

1. Cancer cells have a reduced dependence on signals from other
   cells for their survival, growth and division
2. Cancer cells can survive levels of stress and internal derangement that
   would cause normal cells to undergo apoptosis.
3. Cancer cells can proliferate indefinitely.
4. Cancer cells are genetically unstable.
5. Cancer cells are abnormally invasive.
6. Cancer cells are abnormally avid for nutrients, which they use to generate
   ATP by glycolysis, useful in an oxygen-deprived environment of the center of
   a fast growing tumor.
7. Cancer cells can survive and proliferate in abnormal locations.
8. Cancer cells influence the behavior of their environment, producing signals
   that support their survival.

Question 21

Compare a normal ras from a mutated ras

Answer 21

Normal ras are rtk dependent and is activated by GDP/GTP exchange stimulated by GEFs. However, mutated ras can activate without GTP hydrolysis

Question 22

What is causing cancer cell to survive stress conditions that would normally lead to normal cell undergoing apoptosis

Answer 22

mutations in p53 that
regulate the intracellular death program responsible for apoptosis

Question 23

What would be the effect
of a mutation that
inactivate Rb on cell
division?

Answer 23

increased cell proliferation or increased cell death

Question 24

Why can cancer cell proliferate indefinitely if normal cell can lose the ability to produce telomerase?

Answer 24

Telomerase is reactivated by cancer cell even if its activity is decreased, by passing cell senescence

Question 25

What can cause genetic instability?

Answer 25

1. Defect in DNA replication
2. Defect in DNA repair
3. Defect in cell cycle checkpoint mechanism
4. Mistakes in mitosis
5. Abnormal chromosome number

Question 26

Why are cancer cells invasive?

Answer 26

Cancer cell. lack cadherins, that
help hold normal cells in their proper place, allowing them to move around the connective tissue and metasasis

Question 27

What are collagen?

Answer 27

a major constituent of connective
tissue

Question 28

What are cadherin?

Answer 28

proteins that mediate cell
attachment.

Question 29

Why are cancer cell so avid for nutrients?

Answer 29

So they can generate ATP by glycolysis. ATP by glycolysis is less efficient than oxidative phosphorylation but is good for cancer cell since they are usually oxygen deprived

Question 30

What is unique about cancer cell when they are placed in an area their regular self are not suppose to be in?

Answer 30

They can survive.

Most normal cells die when misplaced.
Cancer cell colonization of new territory may result from their ability to produce their own extracellular survival signals and to suppress their apoptosis
programs

Question 31

How does cancer cells influence the behavior of their environment

Answer 31

They secrete signal influence the behavior of the surrounding cell in the connective tissue. The environment is then modified causing the environment to, produce signals that support the survival and proliferation
of the cancer cells

Question 32

Why is treating cancer a challenge

Answer 32

1. Cancer cells are highly mutated, so they can develop resistant
2. Most cancers are undetectable until the primary tumor has reached, which by the time mutation may have caused the cancer cells to become resistant
3. Due to random mutations, each cancer is heterogeneous, has different types of mutations, thus harder to target

Question 33

To treat cancer, why would Gleevec ibe designed to blocks activation of this kinase.

Answer 33

tyrosine kinase signal for cell proliferation and survival leading to leukemia