The HDM2 (MDM2) Inhibitor NVP-CGM097 Inhibits Tumor Cell Proliferation and Shows Additive Effects with 5-Fluorouracil on the p53-p21-Rb-E2F1 Cascade in the p53^{wild type} Neuroendocrine Tumor Cell Line GOT1

Abstract

Background/Aims: The tumor suppressor p53 is depleted in many tumor cells by the E3 ubiquitin ligase mouse double minute 2 homolog (MDM2) through MDM2/p53 interaction. A novel target for inhibiting p53 degradation and for causing reexpression of p53^{wild type} is inhibition of MDM2. The small molecule NVP-CGM097 is a novel MDM2 inhibitor. We investigated MDM2 inhibition as a target in neuroendocrine tumor cells in vitro. Methods: Human neuroendocrine tumor cell lines from the pancreas (BON1), lung (NCI-H727), and midgut (GOT1) were incubated with the MDM2 inhibitor NVP-CGM097 (Novartis) at concentrations from 4 to 2,500 n<smlcap>M</smlcap>. Results: While p53^{wild type} GOT1 cells were sensitive to NVP-CGM097, p53^mutated BON1 and p53^mutated NCI-H727 cells were resistant to NVP-CGM097. Incubation of GOT1 cells with NVP-CGM097 at 100, 500, and 2,500 n<smlcap>M</smlcap> for 96 h caused a significant decline in cell viability to 84.9 ± 9.2% (p < 0.05), 77.4 ± 6.6% (p < 0.01), and 47.7 ± 9.2% (p < 0.01). In a Western blot analysis of GOT1 cells, NVP-CGM097 caused a dose-dependent increase in the expression of p53 and p21 tumor suppressor proteins and a decrease in phospho-Rb and E2F1. Experiments of co-incubation of NVP-CGM097 with 5-fluorouracil, temozolomide, or everolimus each showed additive antiproliferative effects in GOT1 cells. NVP-CGM097 and 5-fluorouracil increased p53 and p21 expression in an additive manner. Conclusions: MDM2 inhibition seems a promising novel therapeutic target in neuroendocrine tumors harboring p53^{wild type}. Further investigations should examine the potential role of MDM2 inhibitors in neuroendocrine tumor treatment.

Mechanisms of Targeting the MDM2-p53-FOXM1 Axis in Well-Differentiated Intestinal Neuroendocrine Tumors

“…A combinatory effect has been described to be effective in several other cancer entities [26-28, 39, 40]. Furthermore, Reuther et al [41] have recently demonstrated analogous effects concerning antiproliferative and chemosensitizing effects of another MDM2 antagonist, NVP-CGM097, on the p53 wild-type GOT-1 cell line, to which unfortunately only a limited number of research groups have access.…”

The selective PI3Kα inhibitor BYL719 as a novel therapeutic option for neuroendocrine tumors: Results from multiple cell line models

“…For the combination experiments with BYL719/everolimus co-treatment, cell viability was assessed by “Cell Titer 96 Aqueous One Solution” MTS cell viability assay (Promega, Madison, WI, USA) according to the manufacturer`s instructions as previously described in detail [ 43 ]. Cells were treated with various concentrations of 1 μM—20 μM BYL719, 1 nM -10 nM everolimus, or a combination of both drugs for the indicated incubation times.…”

Targeted therapy of gastroenteropancreatic neuroendocrine tumours: preclinical strategies and future targets

“…Therefore, inhibition of p53 modulators as MDM2 and induction of re-expression of p53 wild-type in GEP-NETs might be a promising therapeutic strategy ( 207 ) and should be investigated. Unfortunately, the majority of available GEP-NET cell lines do not reflect the wild-type TP53 status ( 208 ) or have not been assessed so far, making it difficult to estimate possible targets in those cell lines and thus limiting the possibilities for a transferable in vitro drug assessment ( 209 ).…”

“…In the human SI-NET cell line KRJ-I, the MDM2 inhibitor nutlin-3 caused upregulation of p21 and inhibition of cell proliferation ( 209 ). In the human SI-NET cell line GOT1, the MDM2 inhibitor NVP-CGM097 caused upregulation of p53 and p21 and inhibition of cell proliferation ( 208 ). Furthermore, NVP-CGM097 showed additive effects with 5-fluorouracil on cellular survival decrease because of enhanced downregulation of the p53-p21-Rb-E2F1 cascade in the p53 wild-type NET cell line GOT1 ( 208 ).…”