1. Colon cancer is the second leading cause of cancer deaths in the U.S. Polyps, the first stage In tumor development http://www.clevelandclinic.org/registries/inherited/fap.htm

2. Colorectal cancer 150,000 cases diagnosed per year (i.e., your chances are 1/18) > 50,000 deaths (2nd to lung cancer) Early detection key >90% 5 year survival with early detection 60% if it has spread locally <10% if it has metastasized Data from ACS

3. Colorectal cancer treatment 1. Surgical removal of tumor 2.This can be followed by either Radiation or chemotherapy (fluorouracil) 3. Chemotherapy also used to slow the progress of metastatic disease Data from ACS

4. HNPCC 3% of all cases. Defects in mismatch repair. Familial adenomatous polyposis (FAP) 1% of all colon cancers Caused by mutation in a single gene = APC Colon cancer genetics 95% of cases sporadic (no genetic history)

5. Familial Adenomatous Polyposis (FAP)

6. Inheriting FAP-related mutations dramatically increases your risk of developing colorectal cancer. 0.2% colorectal cancers by age 50 6% colorectal cancers lifetime risk 93% colorectal cancers by age 50 100% colorectal cancers lifetime risk

7. Treatment with an aspirin-like drug called celecoxib (a COX2 inhibitor) led to a 25% reduction in polyp number, and 40% reduction in advanced adenomas. Problem--increased cardiovascular risk. The hope is this will allow doctors to Delay surgery till later in life New England Journal of Medicine 342, 1946 (2000) And NCI Cancer Bulletin, April 16, 2008. Until recently the only treatment Was to surgically remove the colon

8. So what causes Familial Adenomatous Polyposis (FAP)

9. Figure 7.23 The Biology of Cancer (© Garland Science 2007)

10. colon polyps Adenomatous Polyposis Coli (APC) tumor suppressor mutated in FAP and in 70% of sporadic cases of colon cancer

11. APC mutations are the earliest event in the development of the tumor

12. APC To find clues to APC’s function they went fishing for partners Cell extract

13. Fishing with APC WT Colon cancer cell line first, immunoprecipitation APC ?

14. Fishing with APC p95 =  -catenin co-immunoprecipitation Colon cancer cell line WT

15. APC Armadillo (ß-catenin) When they went fishing with APC, they pulled out Armadillo

17. Eric Wieschaus and Christiane Nüsslein-Volhard used genetics to identify proteins that set up the embryonic body plan

18. The mighty fruit fly

19. How is the body plan specified? Egg ---> animal in 24 hours!

20. Wieschaus and Nüsslein-Volhard removed single genes and looked for effects on the body plan

21. 2 young scientists 1 microscope 1 year 26,978 flies 139 new genes

22. Five Signal Transduction Pathways Shape virtually all cell fates choices RTK TGF-β Wnt Hedgehog Notch

23. Five Signal Transduction Pathways Shape virtually all cell fates choices RTK TGF-β Wnt Hedgehog Notch All also play key roles in many cancers

24. Wingless signaling specifies cell fates in the ventral epidermis arm mutantwild type

25. Wingless signal influences the fates of neighboring cells

31. Artist’s conception of an Armadillo

32. Epithelial cells at work

36. Elaine Fuch’s Hair Club for Men Rub ß-catenin here! BeforeAfter

37. Level of Wg signal Wingless signaling modulates the stability of Armadillo protein Armadillo

39. Wild-type APC mutant In the absence of APC, levels of Armadillo/ß-catenin rise dramatically

40. Our current model for Wnt signaling

41. Phosphorylation of Armadillo/ß-catenin By GSK3 creates a binding site for an E3 ubiquitin ligase

42. Arm Repeats APC is a complex protein 15 AA rpts Arm repeats protein-protein interaction motif also found in Arm !5 and 20 amino acids repeats bind to Arm SAMP repeats bind Axin 20 AA rpts SAMP rpts

43. Arm Repeats APC is a complex protein 15 AA rpts All tumors carry one allele that makes A truncated APC protein And truncations almost always occur in the “mutation cluster region” (MCR) 20 AA rpts SAMP rpts Arm Repeats MCR

44. Activated Wnt signaling triggers colon cancer

45. Crypt Villus Differentiated cells Proliferating cells A quick look at colon architecture

46. Begin with colon cancer cell line in which the Wnt pathway is ON Add an inducible dominant negative form of TCF4 that turns the Wnt pathway OFF Look for genes whose transcription is regulated by Wnt signaling Hans Clevers

47. Gene turned ON by WntGene turned OFF by Wnt signal The genes turned ON by Wnt signaling are expressed in crypts and those that are turned OFF are expressed in villi

48. Gene turned ON by WntGene turned OFF by Wnt signal The genes turned on by Wnt signaling are expressed in crypts and those that are turned off are expressed in villi

49. Wnt signaling turns OFF the transcription of an key cell cycle regulator: the CDK inhibitor p21 mRNA

50. The effect on p21 expression is indirectly mediated by the transcription factor c-myc. Transcription of the myc gene is directly regulated By TCF/beta-catenin

51. The data The model

52. Stromal cells send Wnt signals Cells that receive them Become stem cells As cells migrate Away from the crypt, they differentiate Let’s put this together to form a picture of normal colon biology and how it is perturbed by APC mutations