Understanding Cell Signals in Cancer Growth

1. Signals and Cancer • http://learn.genetics.utah.edu/content/cells/signals/

2. 1) Look at your photosynthesis data-WHAT does it mean?-WHY did that happen?-Future experiments?2) Look at your packet, what are two ways to graph the data? What is E50?

3. Graph and calculate the rate

4. Warm Up: Solve using chi-squareShow work 2.71

6. Announcements • Last days to get stamps on 2A to get FRQ graded • Chapters 12-13 reading notes due this week • Photosynthesis lab due March 1

7. onion root tip—slides are the control, handout is treated with caffeine

8. Control Hypothesis: If we look at a 100 cells then________________________ Caffeine Null Hypothesis: If we compare an onion grown normally and in caffeine then________________________

9. Agenda • Finish mitosis lab counting • Calculate chi squared for lab—can you accept null? • Cell Cycle Coloring with Checkpoints (on stamp sheet) • DNA Replication presentation prep (on stamp sheet)

10. External signals Growth factors coordination between cells protein signals released by body cells that stimulate other cells to divide density-dependent inhibition crowded cells stop dividing each cell binds a bit of growth factor not enough activator left to trigger division in any one cell anchorage dependence to divide cells must be attached to a substrate “touch sensor” receptors

11. Growth Factors and Cancer Growth factors can create cancers proto-oncogenes normally activates cell division growth factor genes become oncogenes (cancer-causing) when mutated if switched “ON” can cause cancer example: RAS (activates cyclins) tumor-suppressor genes normally inhibits cell division if switched “OFF” can cause cancer example: p53

12. Cancer & Cell Growth Cancer is essentially a failure of cell division control unrestrained, uncontrolled cell growth What control is lost? lose checkpoint stops gene p53 plays a key role in G1/S restriction point p53 protein halts cell division if it detects damaged DNA options: stimulates repair enzymes to fix DNA forces cell into G0 resting stage keeps cell in G1 arrest causes apoptosis of damaged cell ALL cancers have to shut down p53 activity p53 is theCell CycleEnforcer p53 discovered at Stony Brook by Dr. Arnold Levine

13. p53 — master regulator gene NORMAL p53 p53 allows cells with repaired DNA to divide. p53 protein DNA repair enzyme p53 protein Step 2 Step 1 Step 3 DNA damage is caused by heat, radiation, or chemicals. Cell division stops, and p53 triggers enzymes to repair damaged region. p53 triggers the destruction of cells damaged beyond repair. ABNORMAL p53 abnormal p53 protein cancer cell Step 2 Step 1 Step 3 The p53 protein fails to stop cell division and repair DNA. Cell divides without repair to damaged DNA. DNA damage is caused by heat, radiation, or chemicals. Damaged cells continue to divide. If other damage accumulates, the cell can turn cancerous.

14. Development of Cancer Cancer develops only after a cell experiences ~6 key mutations (“hits”) unlimited growth turn on growth promoter genes ignore checkpoints turn off tumor suppressor genes (p53) escape apoptosis turn off suicide genes immortality = unlimited divisions turn on chromosome maintenance genes promotes blood vessel growth turn on blood vessel growth genes overcome anchor & density dependence turn off touch-sensor gene It’s like anout-of-controlcar with manysystems failing!

15. What causes these “hits”? Mutations in cells can be triggered by • UV radiation • chemical exposure • radiation exposure • heat • cigarette smoke • pollution • age • genetics

16. Tumors Mass of abnormal cells Benign tumor abnormal cells remain at original site as a lump p53 has halted cell divisions most do not cause serious problems &can be removed by surgery Malignant tumor cells leave original site lose attachment to nearby cells carried by blood & lymph system to other tissues start more tumors =metastasis impair functions of organs throughout body

17. Cancer: breast cancer cell & mammogram

18. Traditional treatments for cancers Treatments target rapidly dividing cells high-energy radiation kills rapidly dividing cells chemotherapy stop DNA replication stop mitosis & cytokinesis stop blood vessel growth

19. New “miracle drugs” Drugs targeting proteins (enzymes) found only in cancer cells Gleevec treatment for adult leukemia (CML)& stomach cancer (GIST) 1st successful drug targeting only cancer cells withoutGleevec withGleevec Novartes

22. The mitotic spindle at metaphase • Each of the two joined chromatids of a chromosome has a kinetochore. • Anaphase: proteins holding together the sister chromatids of each chromosome are inactivated and they are now full chromosomes.

23. Experimental evidence supports the hypothesis that kinetochores use motor proteins that "walk" a chromosome along the attached microtubules toward the nearest pole. • Meanwhile, the microtubules shorten by depolymerizing at their kinetochore ends • In a dividing animal cell,non kinetochore microtubules are responsible for elongating the whole cell during anaphase

24. Kinetochores use motor proteins that “walk” chromosome along attached microtubule microtubule shortens by dismantling at kinetochore (chromosome) end Chromosome movement

25. Look at the steps of mitosisBook pgs 210-211Write and draw what happens in each part of mitosisHow is cytokinesis different in plants and animal? Page 214 10 minutes

26. Announcements • Last days to get stamps on 2A to get FRQ graded • Chapters 12-13 reading notes due this week • Photosynthesis lab due March 1 • Sub Friday—a friend so be good  • Thanks for the b-day poster period 4 

27. Team Whiteboard • Cytokinesis in Animals • Metaphase • Cytokinesis in Plants • Prophase • Anaphase • Telophase

29. The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinase • Fluctuations in the abundance and activity of cell cycle control molecules pace the sequential events of the cell cycle. • Protein kinases, give the go-ahead signals at the G1 and G2 checkpoints • The kinases are present at a constant concentration in the growing cell, but much of the time they are in inactive form. • To be active, such a kinase must be attached to a cyclin, a protein that gets its name from its cyclically fluctuating concentration in the cell. • These kinases are called cyclin-dependent kinases, or Cdks. The activity of a Cdk rises and falls with changes in the concentration of its cyclin partner. Cdks are relatively constant Cyclins vary in the cycle

30. The stages of mitotic cell division in an animal cell The light micrographs show dividing lung cells from a newt, which has 22 chromosomes in its somatic cells. The chromosomes appear blue and the microtubules green. (Know the characteristics of the phases)

31. Review the details of each mitotic phase animal cells (Know the characteristics of the phases) Mitosis flash animation (Purves)

32. Cytokinesis divides the cytoplasm How does it differ in animal and plant cells?

33. In animal cells, cytokinesis occurs by cleavage • The cleavage furrow, which begins as a shallow groove in the cell surface. • On the cytoplasmic side, a contractile ring of actin microfilaments and molecules of the protein myosin • The contraction of the dividing cell’s ring of microfilaments is like the pulling of drawstrings Cytokinesis animation

34. Cytokinesis Cytoplasmic division Animals constriction belt of actin microfilaments around equator of cell cleavage furrow forms splits cell in two like tightening a draw string

35. Cytokinesis in Plants Plants cell plate forms vesicles line up at equator derived from Golgi vesicles fuse to form 2 cell membranes new cell wall laid down between membranes new cell wall fuses with existing cell wall

36. Going to calculate statistically if a phase is overrepresented • Chi-squared

37. Statistical Test • We want to determine if a coin is fair. In other words, are the odds of flipping the coin heads-up the same as tails-up. • We collect data by flipping the coin 200 times. The coin landed heads-up 108 times and tails-up 92 times. • At first glance, we might suspect that the coin is biased because heads resulted more often than tails. • To analyze our results use a chi-squared test.

38. "The null hypothesis in a chi-square goodness-of-fit test states that the sample of observed frequencies supports the claim about the expected frequencies.   • The alternative hypothesis states that there is no support for the claim pertaining to the expected frequencies."

39. Null hypothesis--The coin should be equally likely to land head-up or tails-up every time • Alternate Hypothesis— The coin is rigged and will not land equally on heads or tails

41. Chi-squared = (108-100)2/100 + (92-100) 2/100 = (8) 2/100 + (-8) 2/100 = 0.64 + 0.64 = 1.28 The next step is to prepare a table as follows.

42. Bio uses 0.05 Degrees of freedom by subtracting one from the number of classes. In this example, we have two classes (heads and tails), so our degrees of freedom is 1. Our chi-squared value is 1.28. Because the chi-squared value we obtained in the coin example is greater than 0.05, we accept the null hypothesis as true and conclude that our coin is fair.

43. So for mitosis lab • Create null hypothesis about cells treated with caffeine vs not treated with caffeine

44. Interpret diagram from notes or book pg 209

45. THE MITOTIC CELL CYCLE The mitotic phase alternates with interphase in the cell cycle What are the key parts of each phase? Mitosis animation

47. How does our body regulate the cell cycle?

48. Cell Cycle regulation Checkpoints cell cycle controlled by STOP & GO chemical signals at critical points signals indicate if key cellular processes have been completed correctly

49. Checkpoint control system 3 major checkpoints: G1/S can DNA synthesis begin? G2/M has DNA synthesis been completed correctly? commitment to mitosis spindle checkpoint are all chromosomes attached to spindle? can sister chromatids separate correctly?

50. G1/S checkpoint G1/S checkpoint is most critical primary decision point “restriction point” if cell receives “GO” signal, it divides internal signals: cell growth (size), cell nutrition external signals: “growth factors” if cell does not receive signal, it exits cycle & switches to G0 phase non-dividing, working state