Inhibition of the sonic hedgehog pathway activates TGF-β-activated kinase (TAK1) to induce autophagy and suppress apoptosis in thyroid tumor cells

Abstract

The sonic hedgehog (Shh) pathway is highly activated in a variety of malignancies and plays important roles in tumorigenesis, tumor growth, drug resistance, and metastasis. Our recent study showed that the inhibitors of the Shh pathway such as cyclopamine (CP), a Smothened (SMO) inhibitor, and GANT61, a Gli1 inhibitor, have modest inhibitory effects on thyroid tumor cell proliferation and tumor growth. The objective of this study was to determine whether autophagy was induced by inhibition of the Shh pathway and could negatively regulate GANT61-induced apoptosis. Here we report that inhibition of the Shh pathway by Gli1 siRNA or by cyclopamine and GANT61 induced autophagy in SW1736 and KAT-18 cells, two anaplastic thyroid cancer cell lines; whereas Gli1 overexpression suppressed autophagy. Mechanistic investigation revealed that inhibition of the Shh pathway activated TAK1 and its two downstream kinases, the c-Jun-terminal kinase (JNK) and AMP-activated protein kinase (AMPK). GANT61-induced autophagy was blocked by TAK1 siRNA and the inhibitors of TAK1 (5Z-7-oxozeaenol, 5Z), JNK (SP600125), and AMPK (Compound C, CC). Inhibition of autophagy by chloroquine and 5Z and by TAK1 and Beclin-1 siRNA enhanced GANT61-induced apoptosis and its antiproliferative activity. Our study has shown that inhibition of the Shh pathway induces autophagy by activating TAK1, whereas autophagy in turn suppresses GANT61-induced apoptosis. We have uncovered a previously unrecognized role of TAK1 in Shh pathway inhibition-induced autophagy and apoptosis.

GANT61 suppresses cell survival, invasion and epithelial-mesenchymal transition through inactivating AKT/mTOR and JAK/STAT3 pathways in anaplastic thyroid carcinoma

“… 22 Besides, another recently published study finds that silencing Gli1 induces autophagy by activating transforming growth factor-β-activated kinase 1 (TAK1) and its downstream protein c-Jun N-terminal kinase (JNK) and adenosine monophosphate-activated protein kinase (AMPK). 12 According to these studies, Gli1 might be a potential target for inhibiting the progression of several cancers, including ATC.…”

“…The present study revealed that GANT61 treatment suppressed proliferation but promoted apoptosis in ATC cells. Furthermore, due to the fact that ATC is characterized by a high level of invasion and Gli1 modulates EMT (a critical pathway that regulates invasion in various cancers) in ATC, 12 , 21 , 23 the regulation of GANT61 on invasion and EMT markers was also explored, which revealed that GANT61 repressed invasion and regulated EMT markers in ATC cells. These data highlighted the potential of GANT61 as a treatment option for ATC; however, further in vivo studies should be conducted to verify these findings.…”

“…To assess the effect of GANT61 (Merck, Germany), cells were cultured with 10 µM GANT61 12 , 13 for 48 hours (h) and collected for RNA sequencing (RNA-seq). For the rescue experiments, cells were incubated with 10 µM SC79 14 , 15 (Beyotime, China) or 0.5 μM colivelin 16 (Tocris, UK).…”

Targeting GLI1 Transcription Factor for Restoring Iodine Avidity with Redifferentiation in Radioactive-Iodine Refractory Thyroid Cancers

“…In addition, GANT61 has shown the inhibitory effect on the growth of several cancers, including ovarian cancer and neuroblastoma [ 14 , 48 , 49 ]. In thyroid cancer, treatment with GANT61 was shown to induce autophagy and to suppress tumor growth with apoptosis [ 50 , 51 , 52 ]. In addition, it was shown to affect the crosstalk with other signaling pathways, such as PI3K/AKT and TGF-β-activated kinase (TAK1) [ 51 , 52 ].…”

“…In thyroid cancer, treatment with GANT61 was shown to induce autophagy and to suppress tumor growth with apoptosis [ 50 , 51 , 52 ]. In addition, it was shown to affect the crosstalk with other signaling pathways, such as PI3K/AKT and TGF-β-activated kinase (TAK1) [ 51 , 52 ]. However, the effects of GANT61 for inducing redifferentiation in thyroid cancer are not known.…”