Investigation of (hypo-)methylation and overexpression of the novel melanoma cell survival gene ASK/Dbf4

• Applicant: Dr. Alireza Mirmohammadsadegh
• Subject Area: Dermatology
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 118087221

Activator of S phase kinase (ASK/DBF4) is a gene that encodes a regulatory subunit required for the activation of cell division cycle 7 (Cdc7) (Jackson, Pahl et al. 1993; Yoon, Loo et al. 1993; Sclafani 2000). ASK/DBF4 is expressed poorly in normal cells but is over-expressed in multiple cancers and tumor cell lines (Kumagai, Sato et al. 1999; Nambiar, Mirmohammadsadegh et al. 2007; Bonte, Lindvall et al. 2008; Sheu and Stillman 2010). A 611 bp CpG island in the promoter of ASK/DBF4 encompasses major transcription factor binding sites reported and represented a pro-oncogenic gene that was putatively hypermethylated and repressed in normal quiescent cells and hypomethylated in certain cancers. Our data from the first phase of the project demonstrate that (1) that repression of ASK/DBF4 mRNA production in normal cells can be attributed to direct methylation-mediated silencing (2) ASK/DBF4 minimal promoter methylation prevents E2F1 mediated induction of ASK/DBF4 (3) the prevalence of ASK/DBF4 promoter methylation during tumor-progression decreases significantly in cancers of ectodermal lineage. Our observations gain significant importance in light of the emerging interest in cancer therapies to decrease DNA methylation, as in certain tissues demethylation based therapy may result in reactivation of developmentally repressed proto-oncogene targets (Eden, Gaudet et al. 2003; Smith, Glazer et al. 2009). In the second phase of the project, we propose to further investigate (1) Polycomb repression complex components involved in the lineage specific methylation/demethylation of ASK/DBF4 in normal and cancer cells (2) relative contribution of gene copy number variation and DNA demethylation in ASK/DBF4 over expression.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Ulrich R. Hengge