12 11 2012 Oncogenes Tumor suppressors How can they be affected genes whose products promotes cell growth genes whose products retard ell growth Positive and negative signals control cell growth o Oncogenes control positive signals o Tumor suppressors control negative signals Proto oncogenes can be affected by increased expression levels mutations o Ex Cmyc o Overamplification activates pro growth gene represses antigrowth sgenes o Protooncongenes can also promote cell death Are mutations the only way to affect cancer genes Cancer and Stem Cells All tissues have stem cells o Non specialized self renewing cells o Division produces unequal daughter cells o One remains a self renewing stem cells one becomes a differentiating cell Prominent theory cancer arises from transformation of stem cells would cause proliferation and under differentiation In terms of causation WHAT IS THE ROOT CAUSE OF CANCER Mutations Epigenetics aneuploidy some viruses express oncoproteins changes in the amount of DNA What kinds of events can produce this cause What causes mutagens o Carcinogens compounds associated with cancer Typically cause cancer by changing DNA sequence Chemical modification of DNA Misincorporation of bases during DNA replica