K-ras codon 12 mutation induces higher level of resistance to apoptosis and predisposition to anchorage-independent growth than codon 13 mutation or proto-oncogene overexpression.

摘要: The position of the point mutation in c-K-ras gene appears associated with different degrees aggressiveness human colorectal tumors. In addition, colon tumors carrying K-ras codon 12 mutations associate lower levels apoptosis than lacking this mutation. To test hypothesis a distinct transforming capacity forms an vitro system, we generated stable transfectants NIH3T3 cells expressing plasmid containing mutated at (K12) or 13 (K13), overexpressing proto-oncogene (Kwt-oe). We evaluated changes morphology, proliferative capacity, contact inhibition, and predisposition to anchorage-independent growth K12, K13, Kwt-oe transformants. studied alterations expression and/or activation proteins that participate signal transduction downstream Ras are involved regulation cell-cell (E-cadherin beta-catenin) cell-substrate (focal adhesion kinase) interactions. observed K13 transformants died synchronically 24-48 h after reaching confluency. Their death was apoptotic. contrast, K12 grew, forming bigger colonies higher cell densities; before confluency, spontaneously formed spheroids showed no sign apoptosis. enhanced resistance apoptosis, loss were AKT/protein kinase B activation, bcl-2, E-cadherin, beta-catenin, focal overexpression, RhoA underexpression, whereas increased sensitivity c-Jun-NH2-terminal 1 pathway. All similar overactivation mitogen-activated protein kinases bax endogenous level. Therefore, our model, localization predisposes level phenotype. may increase not by altering pathways, but differential K-Ras pathways lead inhibition growth. These results offer molecular explanation for clinical setting.