Dlx-2 and glutaminase upregulate epithelial-mesenchymal transition and glycolytic switch

Abstract

Most cancer cells depend on enhanced glucose and glutamine (Gln) metabolism for growth and survival. Oncogenic metabolism provides biosynthetic precursors for nucleotides, lipids, and amino acids; however, its specific roles in tumor progression are largely unknown. We previously showed that distal-less homeobox-2 (Dlx-2), a homeodomain transcription factor involved in embryonic and tumor development, induces glycolytic switch and epithelial-mesenchymal transition (EMT) by inducing Snail expression. Here we show that Dlx-2 also induces the expression of the crucial Gln metabolism enzyme glutaminase (GLS1), which converts Gln to glutamate. TGF-β and Wnt induced GLS1 expression in a Dlx-2-dependent manner. GLS1 shRNA (shGLS1) suppressed in vivo tumor metastasis and growth. Inhibition of Gln metabolism by shGLS1, Gln deprivation, and Gln metabolism inhibitors (DON, 968 and BPTES) prevented Dlx-2-, TGF-β-, Wnt-, and Snail-induced EMT and glycolytic switch. Finally, shDlx-2 and Gln metabolism inhibition decreased Snail mRNA levels through p53-dependent upregulation of Snail-targeting microRNAs. These results demonstrate that the Dlx-2/GLS1/Gln metabolism axis is an important regulator of TGF-β/Wnt-induced, Snail-dependent EMT, metastasis, and glycolytic switch.

Biological role of metabolic reprogramming of cancer cells during epithelial‑mesenchymal transition (Review)

“…In addition to directly regulating expression of metabolic enzymes, c-Myc stimulates the conversion of glutamine to glutamate in tumor cells, and its entry into the TCA cycle. This results in generation of ATP to support proliferation via inhibition of miR-23a/b transcription and upregulation of GLS1 expression (180) (Fig. 2), which has been confirmed to serve a key role in the induction of Snail-dependent EMT and promotion of tumor metastasis (181).…”

EMT Factors and Metabolic Pathways in Cancer

“…Glutaminases 1 and 2 (cytosolic GLS1, mitochondrial GLS2) catalyze the hydrolysis of glutamine to glutamate and ammonia. GLS1 can be induced by TGFβ and Wnt and can promote EMT in a SNAIL-dependent manner while silencing of GLS1 prevents EMT (279). In contrast with GLS1 which is ubiquitously expressed, GLS2 is mainly expressed in brain, liver and pancreas and is inversely associated with EMT in breast cancer and hepatocellular carcinoma cells (279,280).…”

“…GLS1 can be induced by TGFβ and Wnt and can promote EMT in a SNAIL-dependent manner while silencing of GLS1 prevents EMT (279). In contrast with GLS1 which is ubiquitously expressed, GLS2 is mainly expressed in brain, liver and pancreas and is inversely associated with EMT in breast cancer and hepatocellular carcinoma cells (279,280). Interestingly, GLS2 levels are inversely correlated with GLS1 levels in breast cancer and it seems that at least in breast cancer cells GLS2 downregulation is the result and not the driver of EMT; silencing of FOXC2 led to increased levels of GLS2, did not affect GLS1 levels and led to inhibition of EMT (280).…”

Erratum: From Krebs to clinic: glutamine metabolism to cancer therapy

“…While invasive and metastatic cells have not specifically been studied for their sensitivity to glutaminolysis inhibition, it has been shown that highly invasive ovarian cancer cells have increased glutamine dependence compared to less invasive cells 181 , and metastatic prostate tumors show increased glutamate availability and dependence on glutamine uptake 93,182 . Indeed, genetic inhibition of glutaminase was shown to prevent epithelial-to-mesenchymal transition, a key step in tumor cell invasiveness and eventual metastasis 183 . Thus, prevention of metastasis may be another avenue to focus on the development of combinatorial strategies in glutamine metabolic inhibition.…”

“…Upregulates glutamine metabolism enzymes and transporters 6,31,48,145,177 KRAS mutations Drives dependence on glutamine metabolism, suppresses GLUD, and drives NADPH via malic enzyme 1 (ME1) 34,108,119,157,158 HIF1α or HIF2α stabilization Drives reductive carboxylation of glutamine to citrate for lipid production [89][90][91] HER2 upregulation Activates glutamine metabolism through MYC and NF-κB 156,220 p53, p63, or p73 activity Activates GLS2 expression 55,56,62,63 JAK2-V617F mutation Activates GLS and increases glutamine metabolism 221 mTOR upregulation Promotes glutamine metabolism via induction of MYC 155 and GLUD 69,73 or aminotransferases 117 NRF2 activation Promotes production of glutathione from glutamine 222 TGFβ-WNT upregulation Promotes SNAIL and DLX2 activation, which upregulate GLS and activates epithelial-mesenchymal transition 183 PKC zeta loss Stimulates glutamine metabolism through serine synthesis 223 …”