The lichen compound evernic acid in combination with temozolomide regulates Wnt signaling in the glioblastoma cell line U-87

Background Glioblastoma (GBM) is one of the most heterogeneous tumours and develops frequently resistance to chemotherapy, especially to temozolomide (TMZ). Evernic acid (EA) was shown to reduce TMZ dosages in a TMZ resistant glioblastoma cell line (U-87) [1]. Wnt is involved in resistance development.

Aim We investigated the effect of EA, TMZ and their combinations on Wnt (Wingless-related integration site) signaling in U-87 cells.

Methods Cells were treated with EA, TMZ and their combinations. After 24 hours of treatment RNA was isolated. Transcriptom analysis was performed by deep sequencing. Sequence alignment was performed by HISAT2-tool (data base: Homo sapiens hg38). Differential gene expression was calculated (DESeq2). Pathway enrichment and gene ontology analyses were performed in BioJupies.The Wnt inhibitory factor 1 (WIF1) release was measured by ELISA.

Results EA, TMZ and their combinations modulated the canonical Wnt signaling pathway (GO:0060070). Among these the combinations EA (35µM) -TMZ(320µM) (EA₃₅TMZ₃₂₀) and EA₂₀TMZ₅₈₀ downregulated the pathway significantly (p<0.05).

EA₃₅TMZ₃₂₀ downregulated Wnt5A (0.6f, p<0.05). Wnt3 was upregulated by EA₄₅ (2.6f, p<0.05). All combinations downregulated FZD7, a receptor for the Wnt proteins (0.4–0.6f, p<0.05). TMZ₆₀₀, EA₄₅, EA₃₅TMZ₃₂₀ and EA₂₀TMZ₅₈₀ downregulated (TCF7L1), a downstream protein of the pathway.

Single compounds slightly upregulated the WIF1 protein, whereas combinations increased the WIF1 release. The combination EA (35µM)-TMZ(320µM) showed the highest upregulation of WIF1 (10.5 f, p<0.001).

Conclusion The combination of EA and TMZ is a potential candidate to reverse the TMZ-resistance of U-87 cells through the regulation of the Wnt pathway.

Publication History

Article published online:
13 December 2021

• References

• 1 Shcherbakova et al. Oncol Res Treat 2019;42 (suppl4):275-276:P9