Chapter 20 Smartwork (Exam 4)

Endothelial cells stimulated by VEGF extend

filopodia and eventually form a capillary sprout

Pinocytic vesicles in the capillary sprout fuse to form a

large vacuole, eventuually forming a lumen that runs through the snout

Blocking VEGF function would inhibit formation of

new capillaries to the tumor and starve the tumor cells of oxygen

Formation of new capillaries is a regulated process that occurs in a series of steps. Put the steps of angiogenesis in the correct order

1. stimulation of endothelial cells by VEGF

2. endothelial cell extension of filopedia

3. formation of capillary sprout

4. pinocytic vesiclees fusing to form large vacuoles

5. creation of a lumen that runs through capillary sprout

The drug Avastin binds and inhibits VEGF. How does this drug help treat cancer?

• angiogenesis is inhibited, blocking the formation of new capillaries to the tumor

• the cancer cells are starved of oxygen

A gain-of-function mutation in a proto-oncogene converts it into an

oncogene that causes unregulated cell proliferation and contributes to cancer

A malignant tumor invades and colonizes

other tissues while a benign tumor does not

Secondary tumors, called metastases,

can be difficult to eradicate, as they may invadxe multiple organs

Cancer arises as a consequence of changes to DNA. These changes to NA nucleotide sequences are

collectively referred to as mutations

Cancer cells have an abnormal metabolism that fuels their

excessive growth and proliferation. They do NOT ingest neighboring cells as a source of nutrients

What are key behaviors of cancer cells?

• most are genetically unstable, with a greatly increased mutation rate

• are abnormally invasive

• less prone than normal cells to kill themselves by apoptosis

• they can proliferate indefinitely

What can give rise to cancer-promoting mutations?

• DNA replication errors

• exposure to excess sunlight

• exposure to ionizing radiation

• inhalation of tobacco smoke

Which cancer-causing gene can be activated by a single mutation in only one allele?

proto-oncogene

Proto-oncogenes can be activated to form

oncogenes with a single mutation. This type of gain-of-function mutation can stimulate cell survival, proliferation, or both

What class of cancer-critical gene must be inactivated to promote the development of cancer?

tumor suppressor gene

Both copies of a tumor suppressor gene must be

inactivated to contributee to cancer development

Many of the genes mutated in individual tumors are involved with which regulatory pathways?

• pathways governing the initiation of cell division

• pathways regulating the cells response to DNA damage or stress

Some cancer cells are missing a key protein needed to repair

double-strand DNA breaks. They survive by relying on alternative DNA repair mechanisms

Some cancer cells are missing a key protein needed to repair double-strand DNA breaks. They survive by relying on alternative DNA repair mechanisms. To treat these cancers, researchers have developed drugs that do what?

inhibit alternative DNA repair mechanisms

Reactivation of telomerase allows cancer cells to

break through the proliferation barrier faced by normal human cells that have turned off telomerase

By re-expressing telomerase, cancer cells avoid

the progressive telomere shortening that would otherwwise occur as the cells proliferate

What type of mutation(s) would NOT be involved in the inactivation of a tumor suppressor gene?

duplication of the gene

What type of mutation(s) wouuld be involvede in the inactivation of a tumor suppressor gene?

• loss-of-function mutation in tumor suppressor gene

• chromosomal deletion of a region containing the tumor suppressor gene

• loss of a whole chromosome containing the tumor suppressor gene

• silencing the genes activity by epigenetic changes