Calcium/Vitamin D, Biomarkers & Colon Polyp Prevention (PPS4B)

• COX-2 Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  Cyclo-oxygenase-2 (COX-2) is an enzyme that is elevated during periods of inflammation. Inflammation and inflammation regulation likely have important roles in colon cancer development. Control of inflammatory response suppresses COX-2.
  
  
• APC Protein Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  Adenomatous polyposis coli (APC) is a protein encoded by the APC gene and is part of the APC Pathway of colon cancer development. The APC Pathway accounts for familial adenomatosis polyposis (FAP) and approximately 80% of sporadic cancers. The APC protein regulates β-catenin.
  
  
• β-catenin Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  β-catenin is a protein encoded by the CTNNB1 gene and is part of the APC Pathway of colon cancer development. Overexpression and mutations of β-catenin are associated with multiple cancers, including colorectal cancer. An increase in the ratio of APC to β-catenin is indicative of a decrease of adenoma recurrence.
  
  
• E-cadherin Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  E-cadherin is a calcium-dependent cell adhesion molecule necessary for colon crypt structure and function. Regulated by β-catenin, E-cadherin is part of the APC Pathway of colon cancer development. An increase in the ratio of APC to E-cadherin is indicative of a decrease of adenoma recurrence.
  
  
• MLH1 Protein Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  MutL homolog 1 (MLH1) is a protein in the DNA Mismatch Repair (MMR) Pathway. MLH1 protein deficiencies have been found to be related multiple types of cancer, including colorectal cancer. The MMR Pathway accounts for hereditary non-polyosis colon cancer (HNPCC) and approximately 15% of sporadic cancers.
  
  
• Bax Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  Bax (bcl-2-like protein 4) is a protein that promotes apoptosis of cancer cells and is involved in the DNA Mismatch Repair (MMR) Pathway. Apoptosis is higher in colon neoplasms than in normal colon tissue so a lower expression of bax is indicative of decreased adenoma recurrence.
  
  
• hTERT Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  hTERT is a catalytic subunit of telomerase. Telomerase is normally present primarily in stem cells and at least some early daughter cells and is expressed in colon and other cancers. A decrease of hTERT is associated in decreased adenoma recurrence.
  
  
• Bcl-2 Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  B-cell CLL/lymphoma 2 (bcl-2) is a protein encoded by the BCL2 gene which regulates apoptosis. Bcl-2 inhibits apoptosis of abnormal cells. A decrease in the ratio of bax to bcl-2 may be associated with a decrease in adenoma recurrence.
  
  
• TGFα Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  Transforming growth factor alpha (TGFα), a potent stimulator of colonocyte growth/proliferation, can synergize with c-myc to promote malignant transformation in vitro. A decrease in the ratio of TGFα to TGFβ1 may be associated with a decrease in adenoma recurrence.
  
  
• TGFβ1 Levels [ Time Frame: Baseline to end of intervention (up to 5 years) ]
  Transforming growth factor beta 1 (TGFβ1), a potent inhibitor of colonocyte growth/proliferation, inhibits c-myc19,26 and induces p21,26 and the growth suppressive activity of TGFβ1 is inhibited by β-catenin (part of the APC Pathway of colon cancer development). A decrease in the ratio of TGFα to TGFβ1 may be associated with a decrease in adenoma recurrence.
  
  

This study is an add-on study ('adjunct study') to a clinical trial that is already being conducted (the 'parent study'). Study participants will be composed of persons who are already participating in the parent study, "Vitamin D/Calcium Polyp Prevention Study". In the parent study, a total of 1,964 people nationally are being randomly assigned to four different treatment groups: 1) calcium supplements, 600 mg twice a day; 2) vitamin D supplements, 500 IU twice a day; 3) both the calcium and vitamin D supplements twice a day; and 4) placebo tablets twice a day. The treatment period lasts three to five years at the end of which study participants undergo a follow-up colonoscopy to look for new polyps. The parent study began about a year prior to the start of this adjunct study, thus, there are already some patients in the trial who are receiving their study 'treatments' (i.e., have been 'randomized'), but more patients will be recruited into the parent study.

Depending on whether someone has already been randomized, participants of the parent study will be invited to take part in the adjunct study in one of two ways: 'Aim 1' only, or 'All Aims'. First, patients who have already been randomized will be asked to allow biopsies to be made of their rectal tissue during their 3- or 5-year follow-up colonoscopy (Aim 1). Biopsies, which will be used for our biomarker measurements, are very tiny pieces of tissue that can be examined under the microscope. Second, patients who have not yet been randomized will be invited to participate more fully (All Aims) in the adjunct study. This involves having outpatient rectal biopsies taken immediately after their first phone call, their 1-year follow-up visit, and 7 - 21 days before their 3- or 5-year follow-up colonoscopy. Finally, during their 3- or 5-year colonoscopy, biopsies will be taken from three areas of the colon: the rectum (same area as the outpatient biopsies), the sigmoid colon, and the ascending colon. From all of the biopsies taken from all of the visits and colon sites, biomarker measurements will be of normal proteins that occur in the surface cells lining the colon. Study researchers will then analyze whether calcium and/or vitamin D affect these biomarkers and whether the effects predict who gets new polyps.