Establishing novel test systems to functionally analyze direct and reciprocal MLL fusion proteins

We have set up a series of sleeping beauty vector systems that allow us to quickly analyze direct and reciprocal MLL fusions by cloning only the corresponding partner cDNAs. Here we present first data cellular properties exerted by MLL-MAML2, MAML2-MLL, MLL-NEBL, NEBL-MLL, MLL-LASP1 and LASP2-MLL. All fusion genes were either tested alone or in combination. Stable cell lines were established and proper integration and correct splicing of all transgenes was verified. Successful expression of all fusion proteins was induced by adding Doxycycline. We analyzed for growth properties, focus formation capacity and colony forming capacity. In all cases, the reciprocal MLL fusion displayed a higher oncogenic activity, indicating for a role in leukemia development. Future in vivo studies will prove their oncogenic properties.

This work is supported by a grant DKS 2011.09 from the German Children Cancer Aid.