51P - Marine-derived bioactive compound MB-E5 as a cytotoxic agent in glioblastoma cell lines

Date 10 October 2016
Event ESMO 2016 Congress
Session Poster display
Topics Cancer Biology
Basic Scientific Principles
Presenter Shu Yu Cheng
Citation Annals of Oncology (2016) 27 (6): 1-14. 10.1093/annonc/mdw362
Authors S.Y. Cheng1, W. Chen2, P. Sung3, Z. Wen4
  • 1Doctoral Digress Program In Marine Biotechnoogy, National Sun Yat-sen University, 804 - Kaohsiung/TW
  • 2Department Of Neurosurgery, Chang Gung Memorial Hospital-Kaohsiung, Kaohsiung/TW
  • 3Graduate Institute Of Marine Biology, National Dong Hwa University, Pingtung/TW
  • 4Department Of Marine Biotechnology And Resources, National Sun Yat-sen University, Kaohsiung/TW

Abstract

Background

Glioblastoma multiforme (GBM) is the most common primary central nervous system tumor. Even with standard and aggressive treatment strategies the 5-year survival rate is less than 30%. Also, previous results reveal that glutathione S-transferase M3 (GSTM3) is highly expressed in brain tissue and represents the predominant activity of GSTs, a group of enzymes that mainly facilitates detoxification, in the human brain. The compound studied here, ME-E5, is extracted from cultured Vibrio psychroerythrus, a marine bacterial species.

Methods

In this study, the cytotoxic activity of MB-E5 in U87MG and GBM8401 glioblastoma cell lines were investigated using MTT assay and TUNEL assay. Tumor sphere assay were performed to determine the impact of MB-E5 on in vitro neuron cancer stem cell growth. Immunofluorescence assay and western blotting were used to evaluate the level of autophagy-related proteins and the PI3K/Akt pathway. gstm3 gene expression levels were measured in TMZ-resistant glioblastoma cell line by semi-quantitative polymerase chain reaction (PCR).

Results

MTT assays show that MB-E5 exhibits higher cytotoxic activity than Temozolomide (TMZ), a first-line drug in the treatment of gliomas, in GBM cell lines. Neurosphere formation is significantly reduced at low MB-E5 levels. TUNEL assay and western blot analysis show that MB-E5 induces apoptosis and reduces glioblastoma cell survival rate by inhibiting the PI3K/AKT/mTOR signaling pathway. Also, immunofluorescence assay and western blotting results indicate that MB-E5 promotes the expression of autophagy marker LC3-II. Furthermore, MB-E5 demonstrates higher cytotoxicity against TMZ resistant-GBM8401 cells. The results of semi-quantitative PCR indicate a decrease in the expression of gstm3 after 3 days of 200 µM TMZ treatment, but the expression level recovers after 15 days of continuous TMZ treatment in the survival population of GBM cell lines. Moreover, GSTM3 mRNA expression is reduced after MB-E5 treatment.

Conclusions

These results suggest that the marine-derived bioactive compound MB-E5 may be effective as a cancer therapeutic agent in glioblastoma. We also theorize that MB-E5 may reduce gstm3, which could play a key role in TMZ-resistant glioblastoma cells.

Clinical trial identification

Legal entity responsible for the study

Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University, Taiwan

Funding

Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan

Disclosure

All authors have declared no conflicts of interest.