A Small-Molecule Tankyrase Inhibitor Reduces Glioma Stem Cell Proliferation and Sphere Formation

Abstract

Evidence suggests that the growth and therapeutic resistance of glioblastoma (GBM) may be enabled by a population of glioma stem cells (GSCs) that are regulated by typical stem cell pathways, including the WNT/β-catenin signaling pathway. We wanted to explore the effect of treating GSCs with a small-molecule inhibitor of tankyrase, G007-LK, which has been shown to be a potent modulator of the WNT/β-catenin and Hippo pathways in colon cancer. Four primary GSC cultures and two primary adult neural stem cell cultures were treated with G007-LK and subsequently evaluated through the measurement of growth characteristics, as well as the expression of WNT/β-catenin and Hippo signaling pathway-related proteins and genes. Treatment with G007-LK decreased in vitro proliferation and sphere formation in all four primary GSC cultures in a dose-dependent manner. G007-LK treatment altered the expression of key downstream WNT/β-catenin and Hippo signaling pathway-related proteins and genes. Finally, cotreatment with the established GBM chemotherapeutic compound temozolomide (TMZ) led to an additive reduction in sphere formation, suggesting that WNT/β-catenin signaling may contribute to TMZ resistance. These observations suggest that tankyrase inhibition may serve as a supplement to current GBM therapy, although more work is needed to determine the exact downstream mechanisms involved.

Identification of response signatures for tankyrase inhibitor treatment in tumor cell lines

“…YAP signaling target gene expression was reduced in all cell lines. Together, these observations are in line with recent reports that TNKSi induced accumulation of nuclear YAP correlating with reduced YAP target gene expression (Kierulf-Vieira et al, 2020;Waaler et al, 2020b). However, the observations are at odds with earlier reports that TNKSi induced a reduction of nuclear YAP leading to reduced YAP target gene expression (Wang et al, 2015(Wang et al, , 2016.…”

“…To evaluate the effect of G007-LK on YAP signaling, the selected cell line panel was first examined by Western blot analysis. Treatment of each cell line with G007-LK stabilized AMOT, AMOTL1, and AMOTL2 proteins in both cytoplasmic and nuclear extracts (Figures 5B and S5A), consistent with earlier reports using HEK293T cells (Wang et al, 2015), Nuclear YAP accumulation was enhanced in UO-31, OVCAR-4, and ABC-1 cells, similar to recent observations (Kierulf-Vieira et al, 2020;Waaler et al, 2020b), while no change in nuclear YAP levels were observed in COLO 320DM or RKO cells. Moreover, cytoplasmic YAP was not affected in any cell lines following TNKSi (Figure S5A).…”

Identification of Response Signatures for Tankyrase Inhibitor Treatment in Tumor Cell Lines

“…To evaluate the effect of G007-LK on YAP signaling, the selected cell line panel was first examined by Western blot analysis. Treatment of each cell line with G007-LK stabilized AMOT, AMOTL1, and AMOTL2 proteins in both cytoplasmic and nuclear extracts (Figures 5B and S5A), consistent with earlier reports using HEK293T cells (Wang et al, 2015), Nuclear YAP accumulation was enhanced in UO-31, OVCAR-4, and ABC-1 cells, similar to recent observations (Kierulf-Vieira et al, 2020;Waaler et al, 2020b), while no change in nuclear YAP levels were observed in COLO 320DM or RKO cells. Moreover, cytoplasmic YAP was not affected in any cell lines following TNKSi (Figure S5A).…”

TRPM7 Induces Tumorigenesis and Stemness Through Notch Activation in Glioma

“…High heterogenous GBM contains GSC and non-stem tumor cells as well as other non-tumor cells, where GSC interreact with other cells in the microenvironment can further potentiate the malignancy of GBM ( Tao et al, 2020 ). Targeting GSCs and their interactions with other components may serve as the strategy for current GBM therapy ( Kierulf-Vieira et al, 2020 ). In summary, TRPM7 is responsible for sustained Notch1 signaling activation, enhanced expression of GSC markers, and regulation of glioma stemness, all of which contribute to malignant glioma cell growth and invasion.…”