Untersuchung des Wirkmechanismus der SETD5 Proteinmethyltransferase im duktalen Pankreasadenokarzinom.
Hämatologie, Onkologie
Zusammenfassung der Projektergebnisse
Pancreatic cancer is predicted to become the second leading cause of cancer related deaths by 2030. Despite intensive research efforts there are still no effective therapy options for pancreatic cancer patients. The chemotherapeutic drug Gemcitabine which has been introduced in 1997 is still the gold standard in the clinic. In recent years the main focus has been to develop targeted therapies for pancreatic cancer patients and since the majority of pancreatic cancer cases are driven by an activating mutation in the oncogene KRAS research has focused on targeting this oncogene. Except for a covalent inhibitor drugging the KRASG12C mutation which only represents <1% of pancreatic cancer patients, drugs directed against KRAS directly have been unsuccessful. However, due to the fundamental role of KRAS in initiating pancreatic cancer development many strategies have been developed to target downstream molecules of the Ras pathway with promising results in vitro and in mouse models. However, in patients these targeted therapies have failed due to high toxicity or development of resistance to the drugs. Therefore, there is an unmet need to identify novel molecules that could cooperate with the canonical KRAS pathway to drive pancreatic cancer and in the development of therapy resistance. Understanding the molecular mechanisms that lead to the development of adapted therapy resistance might help improve therapy options for pancreatic cancer patients. In this work we identified SETD5 as an epigenetic driver of therapy resistance in pancreatic cancer. SETD5 belongs to the SET domain of family of proteins and contains a Set-and PhD domain. Upon development of resistance to the MEK1/2 inhibitor trametinib SETD5 RNA and protein expression is upregulated in vitro and in vivo and depletion of SETD5 re-sensitizes MEK1/2 inhibitor resistant pancreatic tumor cells as well as pancreatic tumor mice to MEK1/2 inhibitor therapy. In contrast to a recent report that claimed enzymatic activity of SETD5 on Histone H3 lysine 36 we showed that SETD5 lacks any intrinsic methylation activity. Using nucleosomal and histone substrates as well as a protein array we demonstrated that SETD5 neither methylates histones nor has methylation activity on non-histone proteins. We found SETD5 to be present in a complex with the methyltransferases G9a/GLP and the histone deacetylase HDAC3. The interaction of SETD5 with these two repressive histone-modulating enzymes results in the selective deacetylation of H3K9 and H3K27 and demethylation of H3K9 thereby mediating gene repression. Furthermore, we identified the C-terminus of SETD5 to be essential in mediating H3K9 trimethylation while the N-terminus of SETD5 which contains the SET domain is dispensable. The identified SETD5 co-repressor complex regulates gene expression of genes that are involved in mediating drug resistance such as the cytochrome P450 pathway or glutathione metabolism. Targeting the enzymatic molecules in this complex, G9a/GLP and HDAC3, using small-molecule inhibitors we could show that inhibition of the enzymatic activity of this complex sustains trametinib therapy inhibition of pancreatic cancer growth in a mouse model of PDAC as well as of a patient-derived xenograft in mice. Taken together, I identified the putative methyltransferase SETD5 which belongs to the SET domain family proteins to scaffold a corepressor complex that regulates HDAC3 and G9a catalytic activities. In response to MEK1/2 inhibitor treatment in pancreatic ductal adenocarcinoma SETD5 gene and protein expression is upregulated and the repression of gene expression mediated by the SETD5 complex regulates drug resistance. Inhibition of the enzymatic activity of the SETD5 complex by using small molecule inhibitors renders pancreatic tumors vulnerable to MEK1/2 inhibitor treatment.
Projektbezogene Publikationen (Auswahl)
- SETD5-Coordinated Chromatin Reprogramming Regulates Adaptive Resistance to Targeted Pancreatic Cancer Therapy, June 8th 2020, Cancer Cell
Zhentian Wang, Simone Hausmann, Ruitu Lyu, Tie-Mei Li, Shane M. Lofgren, Natasha M. Flores, Mary E. Fuentes, Marcello Caporicci, Ze Yang, Matthew Joseph Meiners, Marcus Adrian Cheek, Sarah Ann Howard, Lichao Zhang, Joshua Eric Elias, Michael P. Kim, Anirban Maitra, Huamin Wang, Michael Cory Bassik, Michael-Christopher Keogh, Julien Sage, Or Gozani and Pawel K. Mazur
(Siehe online unter https://doi.org/10.1016/j.ccell.2020.04.014)
