Deck 5: Growth Factors,receptors,and Cancer

Question 1

Overexpression of growth receptors helps to promote cancer growth by

A)Stimulating the dimerization and transphosphorylation of the receptors.
B)Turning off downstream signaling.
C)Promoting mitogenic signaling.
D)A and C.
E)None of the above.

Answer 1

A and C.

Question 2

Which of the following is NOT true of the Src protein?

A)Src operates as a protein kinase.
B)Src phosphorylates ADP to make ATP.
C)Src can serve as a kinase substrate.
D)A and C.
E)None of the above.

Answer 2

Src phosphorylates ADP to make ATP.

Question 3

Which of the following statements is FALSE regarding Ras mutations in cancer patients?

A)Mutations often occur at codons 12,13,or 61.
B)Oncogenic mutations usually result in higher levels of GDP-bound Ras.
C)Oncogenic mutations usually result in higher levels of GTP-bound Ras.
D)Cells often have compromised activity of GTPase-activating proteins GAPs).
E)None of the above.

Answer 3

Oncogenic mutations usually result in higher levels of GDP-bound Ras.

Question 4

Mutations in the EGF receptor EGF-R)that contribute to the development of cancer are MOST often due to

A)Truncation of the ectodomain of the receptor.
B)Elongation of the ectodomain of the receptor.
C)Point mutations in the C-terminus of the receptor.
D)Point mutations in the tyrosine kinase domain of the receptor.
E)C and D.

Question 5

Which of the following is NOT an example of a tyrosine kinase growth factor receptor that is often altered in cancer cells?

A)ErbB2
B)Kit
C)FGF-R2
D)VEGF
E)PDGF-Rβ

Question 6

In cells infected with simian sarcoma virus,the sis oncogene causes the cells to release increased amounts of Sis protein,which is recognized by PDGF-receptor molecules on the cells' surface.This type of signaling loop is an example of

A)Endocrine signaling.
B)Paracrine signaling.
C)Autocrine signaling.
D)Trans-receptor signaling.
E)None of the above.

Question 7

Which of the following statements about TGF-β receptors is FALSE?

A)They have an extracellular ligand-binding and a transmembrane domain.
B)Their kinase domains phosphorylate serine and threonine residues.
C)Type I and Type II TGF-β receptors form heterodimers.
D)A and C.
E)None of the above.

Question 8

When a growth factor receptor is not bound to ligand,it is MOST likely in what configuration?

A)Monomeric
B)Dimeric
C)Trimeric
D)Heterodimeric
E)None of the above

Question 9

You are growing NIH 3T3 mouse embryonic fibroblasts)in a Petri dish.You provide these cells with a medium containing amino acids,glucose,vitamins,and salts necessary for their survival,but you run out of serum to supplement the medium.Without the addition of serum,what will MOST likely happen to these cells?

A)The cells will die.
B)The cells will continue to grow and proliferate as usual.
C)The cells will remain viable,but will not grow and divide.
D)The cells will proliferate at a higher than normal rate.
E)None of the above.

Question 10

Which of the following statements is TRUE of the ligands of nuclear receptors?

A)They are hydrophobic.
B)They may activate transcription factors.
C)They include steroid sex hormones,retinoids,and vitamin D.
D)A,B,and C.
E)None of the above.

Question 11

Ligand-independent signaling of receptor-tyrosine kinases can result from

A)Fusion events that prevent dimerization.
B)Mutations resulting in truncation of the receptor ectodomain.
C)Amino acid substitutions in the cytoplasmic domains of receptors.
D)B and C.
E)None of the above.

Question 12

Cell surface receptors that are able to create mechanical stability by tethering cells to the extracellular matrix ECM)are known as

A)Adhesions.
B)Matrix metalloproteinases.
C)Integrases.
D)Integrins.
E)Cytokines.