Mechanisms of targeting the MDM2-p53-FOXM1 axis in well-differentiated intestinal neuroendocrine tumors

Item Type:	Article
Title:	Mechanisms of targeting the MDM2-p53-FOXM1 axis in well-differentiated intestinal neuroendocrine tumors
Creators Name:	Briest, F. and Grass, I. and Sedding, D. and Moebs, M. and Christen, F. and Benecke, J. and Fuchs, K. and Mende, S. and Kaemmerer, D. and Saenger, J. and Kunze, A. and Geisler, C. and Freitag, H. and Lewens, F. and Worpenberg, L. and Iwaszkiewicz, S. and Siegmund, B. and Walther, W. and Hummel, M. and Grabowski, P.
Abstract:	BACKGROUND/AIMS: The tumor suppressor p53 is rarely mutated in gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) but they frequently show a strong expression of p53 negative regulators, rendering these tumors excellent targets for a p53 recovery therapy. Therefore, we analyzed the mechanisms of a p53 recovery therapy on intestinal neuroendocrine tumors in vitro and in vivo. METHODS: By western blot and immunohistochemistry, we found that in GEP-NEN biopsy material overexpression of MDM2 was present in intestinal NEN. Therefore, we analyzed the effect of a small-molecule inhibitor, nutlin-3a, in p53 wild type and mutant GEP-NEN cell lines by proliferation assay, flow cytometry, immune fluorescence, western blot and multiplex gene expression analysis. Finally, we analyzed the anti-tumor effect of nutlin-3a in a xenograft mouse model in vivo. During the study, the tumor volume was determined. RESULTS: The midgut wild type cell line KRJ-I responded to the treatment with cell cycle arrest and apoptosis. By gene expression analysis, we could demonstrate that nutlins re-activated an anti-proliferative p53 response. KRJ-I-derived xenograft tumors showed a significantly decrease tumor growth upon treatment with nutlin-3a in vivo. Furthermore, our data suggest that MDM2 also influences the expression of the oncogene FOXM1 in a p53-independent manner. Subsequently, a combined treatment of nutlin-3a and cisplatin (as chemoresistance model) resulted in synergistically enhanced anti-proliferative effects. CONCLUSION: In summary, MDM2 overexpression is a frequent event in p53 wild type intestinal neuroendocrine neoplasms and therefore recovery of a p53 response might be a novel personalized treatment approach in these tumors.
Keywords:	Neuroendocrine Tumors, Signaling, MDM2, p53, FOXM1, Targeted Therapy, Animals, Mice
Source:	Neuroendocrinology
ISSN:	0028-3835
Publisher:	Karger
Volume:	107
Number:	1
Page Range:	1-23
Date:	July 2018
Official Publication:	https://doi.org/10.1159/000481506
PubMed:	View item in PubMed

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