Leukaemia inhibitory factor or oncostatin M induction of Swiss 3T3 cells does not require mevalonic acid synthesis nor protein isoprenylation to initiate DNA replication

Leukaemia inhibitory factor (LIF) or Oncostatin M (OSM), both mitogens for Swiss mouse 3T3 cells, triggers initiation of DNA synthesis without the requirement for mevalonic acid. Thus, Lovastatin (LOV), an inhibitor of the hydroxy methylglutaryl CoA (HMGCoA) reductase, does not block LIF or OSM induced DNA replication and cell multiplication. In contrast, increasing concentrations of LOV from 1 to 60 microM block the mitogenic action of PGF(2alpha) by decreasing the number of cells capable of entering S-phase and dividing. This inhibition by LOV can be reversed by addition of mevanolactone (MEV), an analogue of mevalonic acid. Thus, LIF or OSM triggers initiation of DNA replication independently of mevalonic acid synthesis and therefore without the involvement of isoprenylation of various signalling proteins.