Multistep Model of Cancer Development PDF

4/11/2015 Zarqa University Faculty of Allied Medical Sciences Department of Medical Analysis THE MULTISTEP MODEL OF CANCER DEVELOPMENT Course topic # 3 Instructor: Dr. Khalid M. Alqaisi...

4/11/2015 Zarqa University Faculty of Allied Medical Sciences Department of Medical Analysis THE MULTISTEP MODEL OF CANCER DEVELOPMENT Course topic # 3 Instructor: Dr. Khalid M. Alqaisi The Multistep Model of Cancer Development For cancer to develop, a multiple mutations are generally needed for full-fledged cancer; therefore, the cancer incidence increases with age At the DNA level, a cancerous cell is usually characterized by at least one active oncogene and the mutation of several tumor-suppressor genes E.g. A multi-step model for the development of colorectal cancer (affecting the colon and/or rectum) Dr. Khalid M. Alqaisi (1) 1  4/11/2015 The Multistep Model of Cancer Development Colon 1 Loss of tumor- 4 Loss suppressor 2 Activation of tumor- gene APC of ras suppressor (or other) oncogene gene p53 3 Loss 5 Additional Colon wall of tumor- mutations Normal colon Small benign suppressor Larger Malignant epithelial cells growth gene DCC benign growth tumor (polyp) (adenoma) (carcinoma) APC: adenomatous polyposis coli DCC: deleted in colorectal cancer Dr. Khalid M. Alqaisi (2) The Multistep Model of Cancer Development Dr. Khalid M. Alqaisi (3) 2  4/11/2015 Inherited Predisposition and Other Factors Contributing to Cancer Individuals can inherit oncogenes or mutant alleles of tumor-suppressor genes The fact that multiple genetic changes are required to produce a cancer cell helps explain the predispositions to cancer that run in some families. An individual inheriting an oncogene or a mutant allele of a tumor-suppressor gene will be one step closer to accumulating the necessary mutations for cancer to develop. Dr. Khalid M. Alqaisi (4) Inherited Predisposition and Other Factors Contributing to Cancer Inherited mutations in the tumor-suppressor gene adenomatous polyposis coli are common in individuals with colorectal cancer Mutations in the BRCA1 or BRCA2 gene are found in at least half of inherited breast cancers, and tests using DNA sequencing can detect these mutations Dr. Khalid M. Alqaisi (5) 3 4/11/2015 4