Reversion of transformed phenotype of human adenocarcinoma A549 cells by expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase complementary DNA.
3-Hydroxy-3-methylglutaryl CoA reductase (HMG-CoA reductase) plays a rate-limiting role in isoprenoid biosynthesis and is associated with cell proliferation and transformation. Although an elevated level of HMG-CoA reductase activity is consistently detected in cancer cell lines and tumors, the question remains whether HMG-CoA reductase activity may have a causative role in cell transformation. We have stably transfected the A549 human adenocarcinoma cells with both bicistronic and retroviral expression vectors, including the whole cDNA of human HMG-CoA reductase. Stably transfected cells showed strong morphological changes and disorganization in the filamentous actin architecture, became contact inhibited, and had a lower doubling time. Moreover, they exhibited anchorage-independent growth reduction and lost their capability to induce tumors in nude mice. Surprisingly, no quantitative modification of enzyme activity was observed following transfection, although expression of HMG-CoA reductase cDNA was shown by Northern blot analysis. When endogenous and transfected reductase activity was bypassed by the addition of mevalonate and compactin, a competitive inhibitor, the filamentous actin distribution in HMG-CoA reductase-transfected cells became very similar to that of control cells, demonstrating the role of exogenous HMG-CoA reductase activity in this process. All of our data together strongly suggest that phenotype reversion is dependent on exogenous HMG-CoA reductase expression and that enzymatic activity is implied in this mechanism. HMG-CoA reductase cDNA expression, by expression of a particular form of reductase, might be a negative regulator of cell growth and thus reverse the phenotype of tumor cells.