Phragmunis a suppresses glioblastoma through the regulation of MCL1-FBXW7 by blocking ELK1-SRF complex-dependent transcription.

Glioblastoma (GBM) is a highly aggressive brain tumor. During screening work, we found a new compound named phragmunis A (PGA), which is derived from the fruitbody of Trogia venenata, exhibits a potential cytotoxic effect on patient-derived recurrent GBM cells and temozolomide (TMZ)-resistant cell lines. The present study was designed to investigate the potential molecular mechanism of the anti-glioma effects of PGA in vitro and in vivo. Studies investigating the mechanism revealed that PGA diminished the binding efficiency of ETS family of transcription factor (ELK1) and Serum response factor (SRF), and suppressed ELK1-SRF complex-dependent transcription, which decreased the transcriptional levels of downstream genes Early growth response protein 1 (EGR1)-Polycomb ring finger (BMI1), thus inducing the imbalanced regulation between Myeloid cell leukaemia-1 (MCL1) and F-Box and WD repeat domain containing 7 (FBXW7). Finally, orthotopic xenograft models were established to confirm the anti-glioma effect of PGA on tumour growth. We showed, for the first time, that the cytotoxic effects of PGA occurred by inducing MCL1 inhibition and FBXW7 activation by blocking ELK1-SRF complex-dependent transcription. The blockage of ELK1-mediated transcription resulted in the suppression of EGR1-BMI1, which led to the upregulation of FBXW7 expression and downregulation of MCL1. These findings suggested that PGA could be a therapeutic drug candidate for the treatment of recurrent GBM by targeting the ELK1-SRF complex.

[Effects of ELK-1/JNK/c-Fos on apoptosis of rat hippocampal neurons cultured in vitro with Zuogui Jiangtang Jieyu Formula in simulated diabetes mellitus complicated with depression].

OBJECTIVE: To study the effects of Zuogui Jiangtang Jieyu Formula (ZGJTJYF, the Chinese Medicine) on hippocampal neuron apoptosis in diabetes mellitus complicated with depression (DD). METHODS: The primary cultured hippocampal neurons were treated with high glucose (150 mmol/L) and corticosterone (200 micromol/L) to establish the cell model of DD in vitro. The cultured hippocampal neurons were randomly divided into five groups: blank serum group, normal group, Zuogui Jiangtang Jieyu recipe drug-containing serum group, positive drug (metformin + fluoxetine) drug-containing serum group and model group (three compound holes in each group). The model group and the normal group were given the same amount of culture medium, and the other groups were given the corresponding serum with 10% volume fraction for 18 hours. Hoechst staining, high content cell imaging and RT-PCR were used to detect the apoptosis of hippocampal neurons and the expressions of apoptosis-related ETS-like 1 transcription factor(ELK-1), C-Jun N-terminal kinase(JNK) and c-Fos proteins and genes. RESULTS: Compared with the blank group, the apoptotic number of hippocampal neurons in the model group was increased significantly, and the expression levels of ELK-1, JNK and c-Fos were increased significantly (P＜0.05). Compared with the model group, the local bright spots of hippocampal neurons in the Zuogui Jiangtang Jieyu recipe-containing serum group and the positive drug-containing serum group were decreased significantly, and the number of apoptotic cells was decreased significantly. The expressions of JNK, c-fos protein and mRNA were down-regulated significantly (P＜ 0.05), and the neural network and dendritic junction were improved significantly. CONCLUSION: Zuo Gui Jiang Tang Jie Yu Formula can reverse the expressions of ELK-1, JNK and c-Fos signals in hippocampal neurons under DD environment and play an anti-apoptotic effect.