Michael Dewaele1,2,*, Tommaso Tabaglio3,4,*, Karen Willekens1,2,*, Marco Bezzi3,4,*, Shun Xie Teo3, Diana H.P. Low3,Cheryl M. Koh3, Florian Rambow1,2, Mark Fiers32, Aljosja Rogiers1,2, Enrico Radaelli5, Muthafar Al-Haddawi6, Soo Yong Tan6,7, Els Hermans8, Frederic Amant8,9, Hualong Yan10, Manikandan Lakshmanan11, Ratnacaram Chandrahas Koumar11, Soon Thye Lim12, Frederick A. Derheimer13, Robert M. Campbell13, Zahid Bonday13, Vinay Tergaonkar11, Mark Shackleton10, Christine Blattner14, Jean-Christophe Marine1,2, and Ernesto Guccione3,4
1 Laboratory for Molecular Cancer Biology, VIB Center for the Biology of Disease, KU Leuven, Leuven, Belgium.
2 Laboratory for Molecular Cancer Biology, Department of Human Genetics, KU Leuven,Leuven, Belgium.
3 Division of Cancer Genetics and Therapeutics, Laboratory of Methyltransferases in Development and Disease, Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), Singapore.
4 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
5 Mouse Histopathology Core Facility, VIB Center for the Biology of Disease, KU Leuven, Leuven, Belgium.
6 Advanced Molecular Pathology Laboratory, IMCB, Singapore.
7 Department of Pathology, Singapore General Hospital, Singapore.
8 Gynaecologische Oncologie, UZ Leuven, Leuven, Belgium.
9 Centre for Gynecologic Oncology Amsterdam (CGOA), Antoni Van Leeuwenhoek – Netherlands Cancer Institute, Amsterdam, Netherlands.
10 Karlsruhe Institute of Technology, Institute of Toxicology and Genetics, Karlsruhe, Germany.
11 Mouse Models of Human Cancer Unit, IMCB, Proteos, Singapore.
12 Department of Medical Oncology,National Cancer Centre Singapore, Singapore.
13 Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA.
14 Melanoma Research Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Australia.
Published in The Journal of Clinical Investigations on 23 November 2015
MDM4 is a promising target for cancer therapy, as it is undetectable in most normal adult tissues but often upregulated in cancer cells to dampen p53 tumor-suppressor function. The mechanisms that underlie MDM4 upregulation in cancer cells are largely unknown. Here, we have shown that this key oncogenic event mainly depends on a specific alternative splicing switch. We determined that while a nonsense-mediated, decay-targeted isoform of MDM4 (MDM4-S) is produced in normal adult tissues as a result of exon 6 skipping, enhanced exon 6 inclusion leads to expression of full-length MDM4 in a large number of human cancers. Although this alternative splicing event is likely regulated by multiple splicing factors, we identified the SRSF3 oncoprotein as a key enhancer of exon 6 inclusion. In multiple human melanoma cell lines and in melanoma patient–derived xenograft (PDX) mouse models, antisense oligonucleotide–mediated (ASO-mediated) skipping of exon 6 decreased MDM4 abundance, inhibited melanoma growth, and enhanced sensitivity to MAPK-targeting therapeutics. Additionally, ASO-based MDM4 targeting reduced diffuse large B cell lymphoma PDX growth. As full-length MDM4 is enhanced in multiple human tumors, our data indicate that this strategy is applicable to a wide range of tumor types. We conclude that enhanced MDM4 exon 6 inclusion is a common oncogenic event and has potential as a clinically compatible therapeutic target.
Figure legend:Targeting MDM4 splicing in cancer therapy.
Whereas MDM4 is unproductively spliced in most normal adult tissues, MDM4 protein is highly expressed in embryonic tissues and in cancers as a result of enhanced exon 6 inclusion. SRSF3, among other SRSF family members, is the only one that promotes exon 6 inclusion. TG003 is a CLK inhibitor that affects the phosphorylation of multiple SR proteins. Inducing MDM4 exon 6 skipping via ASO is a very specific, efficient, and clinically compatible approach to inhibiting p53-dependent MDM4 oncogenic functions.
For more information on Ernesto GUCCIONE 's lab, please click here.