NIBR
POSTDOCTORAL PROGRAM

RalphTiedtRalph Tiedt, PhD
(Co-Mentor: Moriko Ito, PhD)

Oncology
Basel, Switzerland

Genetic alterations, such as mutations or translocations, in genes encoding transcriptional regulators are often encountered in human cancer and are thought to cause aberrant gene expression profiles that maintain a cancerous state. While transcription factor complexes were traditionally deemed “undruggable”, it has recently been recognized that some transcriptional – or epigenetic – regulators are indeed interesting potential drug targets for cancer treatment, among these histone methyltransferases and histone demethylases. Cancer-specific gain-of-function alterations that result in dependence on such epigenetic enzymes have mainly been found in hematological malignancies. As an example, rearrangements of the MLL gene in a subset of acute leukemias result in fusion proteins that critically depend on the histone methyltransferase Dot1L as a co-factor. Loss-of-function mutations affecting epigenetic regulators are more broadly observed across cancer types.

In our group we are utilizing RNAi, CRISPR, low molecular weight inhibitor-based screening approaches, and genomic techniques such as chromatin immunoprecipitation and next-generation sequencing in order to identify novel epigenetic regulators that are specifically required for cancer growth and survival. Furthermore, we strive to elucidate the molecular mechanisms leading to dependence on such epigenetic enzymes in different cancer settings. In our current work we are using deep-coverage shRNA pools to screen for new targets in leukemias and lymphomas as well as to characterize the mechanism of oncogenesis for epigenetic regulators with a well-established role in cancer.

Selected Publications

Rescue screens with secreted proteins reveal compensatory potential of receptor tyrosine kinases in driving cancer growth.
Harbinski F, Craig VJ, Sanghavi S, Jeffery D, Liu L, Sheppard KA, Wagner S, Stamm C, Buness A, Chatenay-Rivauday C, Yao Y, He F, Lu CX, Guagnano V, Metz T, Finan PM, Hofmann F, Sellers WR, Porter JA, Myer VE, Graus-Porta D, Wilson CJ, Buckler A, Tiedt R.
Cancer Discov. 2012 Oct;2(10):948-59.

A drug resistance screen using a selective MET inhibitor reveals a spectrum of mutations that partially overlap with activating mutations found in cancer patients.
Tiedt R, Degenkolbe E, Furet P, Appleton BA, Wagner S, Schoepfer J, Buck E, Ruddy DA, Monahan JE, Jones MD, Blank J, Haasen D, Drueckes P, Wartmann M, McCarthy C, Sellers WR, Hofmann F.
Cancer Res. 2011 Aug 1;71(15):5255-64.

Ratio of mutant JAK2-V617F to wild-type Jak2 determines the MPD phenotypes in transgenic mice.
Tiedt R, Hao-Shen H, Sobas MA, Looser R, Dirnhofer S, Schwaller J, Skoda RC.
Blood. 2008 Apr 15;111(8):3931-40.

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