Cell Biology Exam 3
Answer all three parts
Please keep the parts separate and put your name on the first page (at least) of each answer
Part 1. Dr Kim Creek
Your Ph.D. advisor is interested in transforming growth factor-beta (TGF-beta)
signaling in cancer cells and has just obtained a pancreatic cancer cell line
that no longer responds to TGF-beta (i.e., it is TGF-beta resistant). Your
advisor wants you to determine how these cancer cells became resistant to TGF-beta.
In no more than four double spaced type written pages first describe several
different cellular and molecular mechanisms that cancer cells have utilized to
become refractory to TGF-beta and then outline a series of experiments that one
might use to determine exactly how the pancreatic cancer cells became TGF-beta
resistant. It will be helpful to do some literature searching/reading to help
you with this question.
Part 2. Dr Paul Housley
You are studying a new compound (“MoreDop”) which has activity in the brain. In particular, you have preliminary evidence that MoreDop causes the release of Dopamine from specific neurons in the hypothalamus. You obtain the following data from administering MoreDop to rats and measuring the release of Dopamine from the hypothalamus:
Dopamine released (pmoles) MoreDop (mg)
100 1000
100 700
100 300
90 120
80 80
70 60
60 50
50 40
40 30
30 20
20 13
10 7
0 3
0 1
Question 1(50%):
What is the ED50 for hypothalamic dopamine release mediated by MoreDop? Show how you estimated this value.
A new synthetic compound (Estostim) exhibits appreciable estrogenic activity at doses of 10 mg or higher. Administration of Estostim to rats at varying doses up to 100 mg had NO effect on hypothalamic dopamine release. However, when 10 mg of Estostim is administered together with varying amounts of MoreDop, you obtain the following results:
Dopamine released (pmoles) Estostim (10 mg) plus Indicated amount of MoreDop (mg)
100 3000
100 2000
100 1600
90 620
80 400
70 300
60 250
50 200
40 152
30 104
20 64
10 37
0 16
0 8
Question 2 (50%):
For this experiment, does Estostim act through the same receptor as MoreDop? What type of ligand is Estostim in this experiment? Show how you arrived at your explanations for this question.
Part 3. Dr Wayne Carver
You have generated data suggesting that the composition of the extracellular matrix can promote the differentiation of mesenchymal stem cells into cardiac myocytes. In these experiments, stem cells cultured within a 3-dimensional collagen type I matrix differentiate into beating cardiac myocytes while stem cells cultured in a laminin or other 3-dimensional matrix remain undifferentiated. Preliminary proteomics data suggest that the cells cultured in the collagen matrix express a unique protein that may be a novel matrix metalloprotease. You hypothesize that this putative protease is involved in collagen remodeling necessary for the differentiation of the stem cells into cardiac myocytes. Please discuss the features that you would expect this protein to have if it is indeed a matrix metalloprotease. Also, please briefly describe two experiments you could perform to test whether this protein in fact plays a role in the conversion of stem cells into cardiac myocytes.
Have a good holiday season and a happy New year