The histone methyltransferase DOT1L is required for proper DNA damage response, DNA repair, and modulates chemotherapy responsiveness

Clin Epigenetics. 2019 Jan 7;11(1):4. doi: 10.1186/s13148-018-0601-1.

Vijayalakshmi Kari ¹, Sanjay Kumar Raul ¹ ², Jana Maria Henck ¹, Julia Kitz ³, Frank Kramer ⁴ ⁵, Robyn Laura Kosinsky ¹, Nadine Übelmesser ⁶, Wael Yassin Mansour ⁷ ⁸, Jessica Eggert ¹, Melanie Spitzner ¹, Zeynab Najafova ¹, Holger Bastians ⁶, Marian Grade ¹, Jochen Gaedcke ¹, Florian Wegwitz ¹, Steven A Johnsen ⁹

Affiliations

1 Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, 37075, Göttingen, Germany.
2 Department of Biotechnology, Rama Devi Women's University, Bhubaneswar, 751022, India.
3 Department of Pathology, University Medical Center Göttingen, 37075, Göttingen, Germany.
4 Department of Medical Statistics, University Medical Center Göttingen, 37075, Göttingen, Germany.
5 Department of Computer Science, University Augsburg, 86159, Augsburg, Germany.
6 Institute of Molecular Oncology, Section for Cellular Oncology, Göttingen Center for Molecular Biosciences (GZMB) and University Medical Center, University of Göttingen, 37077, Göttingen, Germany.
7 Laboratory of Radiobiology and Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany.
8 Tumor Biology Department, National Cancer Institute, Cairo University, Cairo, 11796, Egypt.
9 Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, 37075, Göttingen, Germany. steven.johnsen@med.uni-goettingen.de.

PMID: 30616689 DOI: 10.1186/s13148-018-0601-1

Abstract

Background: Disruptor of telomeric silencing 1-like (DOT1L) is a non-SET domain containing methyltransferase known to catalyze mono-, di-, and tri-methylation of histone 3 on lysine 79 (H3K79me). DOT1L-mediated H3K79me has been implicated in chromatin-associated functions including gene transcription, heterochromatin formation, and DNA repair. Recent studies have uncovered a role for DOT1L in the initiation and progression of leukemia and other solid tumors. The development and availability of small molecule inhibitors of DOT1L may provide new and unique therapeutic options for certain types or subgroups of Cancer.

Methods: In this study, we examined the role of DOT1L in DNA double-strand break (DSB) response and repair by depleting DOT1L using siRNA or inhibiting its methyltransferase activity using small molecule inhibitors in colorectal Cancer cells. Cells were treated with different agents to induce DNA damage in DOT1L-depleted or -inhibited cells and analyzed for DNA repair efficiency and survival. Further, rectal Cancer patient samples were analyzed for H3K79me3 levels in order to determine whether it may serve as a potential marker for personalized therapy.

Results: Our results indicate that DOT1L is required for a proper DNA damage response following DNA double-strand breaks by regulating the phosphorylation of the variant histone H2AX (γH2AX) and repair via homologous recombination (HR). Importantly, we show that small molecule inhibitors of DOT1L combined with chemotherapeutic agents that are used to treat colorectal cancers show additive effects. Furthermore, examination of H3K79me3 levels in rectal Cancer patients demonstrates that lower levels correlate with a poorer prognosis.

Conclusions: In this study, we conclude that DOT1L plays an important role in an early DNA damage response and repair of DNA double-strand breaks via the HR pathway. Moreover, DOT1L inhibition leads to increased sensitivity to chemotherapeutic agents and PARP inhibition, which further highlights its potential clinical utility. Our results further suggest that H3K79me3 can be useful as a predictive and or prognostic marker for rectal Cancer patients.

Keywords

Colorectal cancer; DNA damage; DNA double-strand breaks; DOT1L; FOLFIRI; H3K79me; Homologous recombination; PARP inhibition; γH2AX.

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