CHIR99021, trough GSK-3β Targeting, Reduces Epithelioid Sarcoma Cell Proliferation by Activating Mitotic Catastrophe and Autophagy

Abstract

Epithelioid sarcoma (ES) is a rare disease representing <1% of soft tissue sarcomas. Current therapies are based on anthracycline alone or in combination with ifosfamide or other cytotoxic drugs. ES is still characterized by a poor prognosis with high rates of recurrence. Indeed, for years, ES survival rates have remained stagnant, suggesting that conventional treatments should be revised and improved. New therapeutic approaches are focused to target the key regulators of signaling pathways, the causative markers of tumor pathophysiology. To this end, we selected, among the drugs to which an ES cell line is highly sensitive, those that target signaling pathways known to be dysregulated in ES. In particular, we found a key role for GSK-3β, which results in up-regulation in tumor versus normal tissue samples and associated to poor prognosis in sarcoma patients. Following this evidence, we evaluated CHIR99021, a GSK-3 inhibitor, as a potential drug for use in ES therapy. Our data highlight that, in ES cells, CHIR99021 induces cell cycle arrest, mitotic catastrophe (MC) and autophagic response, resulting in reduced cell proliferation. Our results support the potential efficacy of CHIR99021 in ES treatment and encourage further preclinical and clinical studies.

Regulation of Autophagy by the Glycogen Synthase Kinase-3 (GSK-3) Signaling Pathway

“…ER stress is also known to induce GSK-3β activation and phosphorylate ULK1 leading to induction of autophagy [91]. On the other hand, several studies have also shown that inhibition of GSK-3β upregulates autophagy flux [11,12]. Moreover, GSK-3β can be also regulated by PKC and elF4A3 to trigger TFEB nuclear localization and activation [65,66].…”

“…TSC2, a GTPase-activating protein (GAP), regulates mTORC1 through Rheb, which converts Rheb-guanosine triphosphate (GTP) into Rheb-guanosine diphosphate (GDP) form to inactivate Rheb, leading to mTORC1 inactivation [97,98]. The inhibition of GSK-3 α/β using the CHIR99021 GSK-3 α/β inhibitor was shown to enhance the ratio of LC3 A/B-II to LC3 A/B-I and effectively decrease p62 expression in epithelioid sarcoma cells [11], suggesting that induction of autophagy occurs in epithelioid sarcoma cells [11]. Moreover, this study also examined the mTORC1 expression and found downregulation of mTOR and p-mTOR expression in CHIR99021 GSK-3 α/β inhibitor treatment [11].…”

“…The inhibition of GSK-3 α/β using the CHIR99021 GSK-3 α/β inhibitor was shown to enhance the ratio of LC3 A/B-II to LC3 A/B-I and effectively decrease p62 expression in epithelioid sarcoma cells [11], suggesting that induction of autophagy occurs in epithelioid sarcoma cells [11]. Moreover, this study also examined the mTORC1 expression and found downregulation of mTOR and p-mTOR expression in CHIR99021 GSK-3 α/β inhibitor treatment [11]. On the other hand, some reports show that activation of GSK-3 phosphorylates and activates TSC2, leading to downregulation of mTORC1 [95,96].…”

“…Studies have shown that GSK-3β nuclear localization can be induced by inhibition of mTORC1 using mTORC1 inhibitor rapamycin, resulting in the reduction of c-Myc and Snail [4,10]. Inhibition of GSK-3β is also known to enhance autophagy and lysosomal acidification [11,12]. GSK-3β is known to be involved in neuronal development and suppression of GSK-3β showed the ability to reduce αsynuclein in cellular models of Parkinson's disease [2,[13][14][15].…”

Targeting glycogen synthase kinase 3 with CHIR99021 negatively regulates allergen‐induced mast cell activation

“…CHIR99021, an ATP-competitive inhibitor, has been well established as a selective and potent inhibitor of GSK3 activity [19]. Due to the mechanism of action, to determine if CHIR99021 was in fact targeting and inhibiting GSK3 in our mast cell model, we investigated GSK3 kinase activity by measuring total protein levels of the downstream target β-catenin.…”