Page 143 - Molecular features of low-grade developmental brain tumours

DYSREGULATION OF MMP/TIMP IN SEGA: MODULATION BY MIR-320D IN VITRO
75. Furthermore, it has been shown that TIMP2, is also involved in the activation of pro‐ MMP2 together with MMP14 76,77. We found a higher expression of MMP inhibitors TIMP1, TIMP2 and TIMP3 in SEGA as compared to control tissue. The higher expression of TIMPs may act as a compensatory mechanism for higher MMP expression, which could explain why the higher expression of MMP2, MMP11, MMP14, MMP15 and MMP19 does not lead to metastases and excessive growth in SEGA. Interestingly, we found that MMP19 was highly expressed in recurrent/regrown SEGA as compared to non-recurrent/regrown SEGA using RT-qPCR analysis. Previous studies found a correlation between MMP19 expression and tumour malignance/invasion 72,74,78. Therefore, MMP19 expression could potentially be utilized as a biomarker for recurrence/regrowth. However, our sample size of recurrent/ regrown SEGA was small and this effect was not found in the RNA-Seq data, indicating that further investigation is required.
miR-320d is a predictive regulator of MMPs and is lower expressed in SEGA compared to control
Previous research has shown the importance of miRNAs in TSC and SEGA 26,29 and their role in regulating MMP expression 28,79. In this study we identified six miRNAs (miR-320d, miR- 320b, miR-320c, miR-625-5p, miR-330-5p and miR-3200-3p) with lower expression in SEGA as compared to controls that could potentially target MMP expression. Research from Qin et al. 2017 has shown that downregulation of miR-320d in gliomas predicted lower survival rates and increased growth and proliferation 49. However, in our study we did not find a correlation between the expression of miR-320d and the size of tumour or tumour recurrence/regrowth. Furthermore, Qin et al. 2017 indicated miR-320d as a regulator of MMP2, decreasing MMP2 protein expression in glioma cell lines, inducing cell apoptosis and suppressing cell growth and migration49. In accordance with this study, we found that miR-320d can target MMP2 in human fetal astrocytes, but did not affect the expression of MMP11, MMP14, MMP15 and MMP19. Since the interaction of miR-320d was based on prediction tools, it could be that these MMPs are not responsive to this miRNA, however further investigation is needed. Alternatively, it could be of interest to combine miR-320d with the other 5 miRNAs predicted to target MMP2, MMP11, MMP14, MMP15 and MMP19 (miR-320b, miR-625-5p, miR-320c, miR- 330-5p and miR-3200-3p) in order to increase the regulatory effect on MMP expression.
Conclusions
Taken together, this study provides evidence that both MMPs and TIMPs are highly expressed in SEGA compared to control tissue, indicating that the MMP/TIMP proteolytic system is dysregulated in SEGA as observed in tubers of TSC patients. The MMP-targeting miR-320d is down-regulated in SEGA. In human fetal astrocytes, the dysregulation of MMP2 can be normalized by miR-320d. We therefore conclude that targeting MMPs potentially with miR- 320d alone or in combination with other MMP targeting miRNAs, could be of interest as a therapeutic intervention for TSC patients with SEGA.
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