ch 23

Question 1

Palladin

Answer 1

encodes an essential component of a cell’s cytoskeleton; when
mutated, palladin contributes to the spread of pancreatic cancer

Question 2

Why might this cancer rate differ between men and women?

Answer 2

Cancer is not a single disease; rather, it is a
heterogenous group of disorders characterized by
the presence of cells that do not respond to the
normal controls of cell division.

Question 3

Normal cells in tumor formation

Answer 3

: grow, divide, mature, and die in response to internal and external signals.

Stimulatory and inhibitory signals regulate growth

Question 4

Cancer cells in tumor formation

Answer 4

one or more of these signals has been disrupted.

Cell proliferates at an abnormally high rate.

Question 5

Benign tumor

Answer 5

the tumor remains localized. A benign tumor is an abnormal (but noncancerous) collection of
cells

Question 6

Malignant tumor

Answer 6

tumor cells invade other tissues.

Question 7

Metastasis

Answer 7

the tumor cells induce secondary tumors

Question 8

Alfred Knudson’s

Answer 8

• proposed cancer is the result of a multistep process that requires several mutations.

If one or more of the mutations
are inherited, fewer additional
mutations are required to
produce cancer, and the cancer
tends to “run in the family”.

Question 9

“Two-Hit Hypothesis”

Answer 9

– only two mutations necessary
to cause the tumor.

Question 10

Clonal Evolution

Answer 10

tumor cells accumulate
somatic mutations that
allow them to become
increasingly more
aggressive in their
proliferate properties.

Question 11

Retrovirus

Answer 11

RNA virus that inserts a copy of its
genome into the DNA of a host cell that it invades,
changing the genome of that cell.

Question 12

Retroviruses cause cancer by

Answer 12

• mutating and rearranging proto-oncogenes
  − inserting strong promoters near proto-oncogenes
• Human papilloma virus and cervical cancer

Question 13

At least three types of
chromosome rearrangements with cancer

Answer 13

-deletions, inversions, and
translocations are associated
with certain types of cancer.

Question 14

Epigenetic changes in cancer

Answer 14

Alterations to DNA methylation or chromatin structure are seen in many
cancers

Histone proteins are also often abnormally modified in cancer cells.

Question 15

Hypomethylation

Answer 15

• an overall lower level of DNA methylation
  − It is suspected that hypomethylation leads to activation of
  oncogenes!
  − Some evidence also suggest it causes chromosome instability –
  a hallmark of many cancers.

Question 16

Hypermethylation

Answer 16

• some specific CpG islands have extra methylation

− May deactivate tumor-suppressor genes

Question 17

Two processes control the rate at which mutations
arise within a cell

Answer 17

1.The rate at which errors arise during and after
the course of DNA replication.

2.The efficiency with which these errors are
corrected.

Question 18

Defects in genes that encode components of
DNA repair systems have been consistently
associated with a number of cancers.

Answer 18

13% of colorectal, endometrial, and stomach cancers have
cells that are defective in mismatch repair

DNA-repair system defects may also contribute to
chromosome rearrangements and genomic instability

Question 19

Sequences that regulate the expression of the
telomerase gene are mutated in many tumor
cells.

Answer 19

This allows telomerase to be expressed and allows
cancer cells to divide indefinitely!

Many high risk neuroblastoma cancers in child

Question 20

Oxygen and nutrients, essential to tumor survival,
are supplied by blood vessels, and the growth of new
blood vessels (angiogenesis) is important to tumor
progression

Answer 20

Angiogenesis is stimulated by growth factors and other
proteins encoded by genes whose expression is carefully regulated in normal cells.

In tumor cells, the genes encoding these proteins are
often overexpressed

Question 21

Many tumor cells exhibit widespread
reduction in the expression of many miRNAs

Answer 21

Lower levels of miRNAs may contribute to
cancer by allowing oncogenes that are normally
controlled by miRNAs to be expressed at high
levels

Question 22

Many cancers are caused by defects in this cell cycle
machinery!

Answer 22

– Mutations in the gene that encodes the RB protein are
associated with many cancers, including retinoblastoma.

– The gene that encodes cyclin D is overexpressed in
about 50% of all breast cancers.

– The tumor-suppressor gene p53 is mutated in about 75%
of all colon cancers

Question 23

Oncogenes

Answer 23

mutated, dominant-acting,
stimulatory genes that cause cancer

– Proto-oncogenes: responsible for basic cellular
functions in normal cells; when mutated, they become oncogenes

driving transcription forward

Question 24

Tumor-suppressor genes:

Answer 24

mutated recessive-acting inhibitory genes that are inactive

fixing the DNA

Question 25

What causes the uncontrolled
cell growth?

Answer 25

1) Activation of Oncogenes

2) Inactivation of Tumor Suppressor Genes

Question 26

Signal-transduction pathways

Answer 26

involve an external signal
triggering a cascade of intracellular reactions, producing a
specific response

Question 27

Ras signal-transduction

Answer 27

pathway is activated when a
growth factor (such as epidermal
growth factor), binds to a
receptor on the cell membrane

Question 28

Imagine you have a mutation in
this RAS gene.

Answer 28

The RAS proteins become
automatically activated and the cascade becomes almost continuous. What do you expect to happen to this cell?

This is an example of Oncogene Activation!

Too much gas pedal!

Mutations in genes encoding Ras
protein leads to cancer:

95% of tumors of the pancreas
45% of colorectal tumors

Question 29

Cells have mechanisms to stop abnormal cells
from progressing through the cell cycle.

Answer 29

Tumor suppressor genes!

Question 30

Role of environmental factors in cancer