O-GlcNAc modification of oncogenic transcription factor Sox2 promotes protein stability and regulates self-renewal in pancreatic cancer

Abstract

Pancreatic cancer is among the 3rd leading cause of cancer related deaths in the United States along with a 5-year survival rate of 7%. The aggressive biology of the disease is responsible for such dismal outcome and is manifested by an increase in self-renewal capacity of the cancer cells, which leads to an increased rate of tumor-recurrence, contributing to poor prognosis. Transcription factor SOX2 maintains a critical balance between differentiation and “stemness” and is thus tightly regulated within a cell. In cancer, SOX2 is aberrantly “turned-on” leading to activation of self-renewal pathways in cancer. Regulation of Sox2 in cancer is poorly understood. In the current study, we show for the first time that in pancreatic cancer, Sox2 is modified by addition of O-GlcNAc moiety, catalyzed by OGT (O-GlcNAc Transferase) at S246. This activates Sox2 transcriptional activity by stabilizing the protein in the nucleus. A CRISPR-OGT knockout in pancreatic cancer cell line S2VP10 resulted in a delayed tumor initiation. We further showed that mutation of this site (S246A) prevents the modification of Sox2 and its downstream activity. Our study also demonstrated that targeting OGT in vivo with a small molecule inhibitor OSMI, results in decreased tumor burden, delayed tumor progression and a decreased expression of SOX2 in pancreatic cancer cells. Our study highlights for the first time that that the O-GlcNAc transferase dependent SOX2 glycosylation has a profound effect on the transcriptional activity of SOX2 and is instrumental in determining self-renewal in pancreatic cancer.SignificanceOur study highlights for the first time that that the O-GlcNAc transferase dependent SOX2 glycosylation determines self-renewal in pancreatic cancer which is responsible for tumor initiation.

High Glucose Triggers Nucleotide Imbalance through O-GlcNAcylation of Key Enzymes and Induces KRAS Mutation in Pancreatic Cells

“…This novel modulation of RNR activity through O-GlcNAcylation of RRM1 at T734 links glucose and nucleotide metabolism in cancer initiation. Interestingly, it was reported that O-GlcNAcylation of oncogenic transcription factor Sox2 in pancreatic cancer cells is responsible for tumor initiation (Nikita Sharma et al, 2018;Qian et al, 2018). It would be worthwhile to investigate whether O-GlcNAcylation of RRM1, similar to Sox2, has a significant impact on cancer initiation and progression in general.…”

The glycosylation landscape of pancreatic cancer (Review)

“…When pancreatic cancer develops increased O-GlcNAcylation may block cancer cell apoptosis and lead to oncogenic activation of NF-κB signalling (66). Several proteins with defined roles in pancreatic cancer have been shown to be modified by O-GlcNAc including the heat shock protein HSP70 (67), the transcription factor Sp1 (68), the Wnt signalling proteins β-catenin and LRP6 (69), and more recently the transcription factor Sox2 that determines self-renewal in pancreatic cancer and is responsible for tumour initiation (70). Inhibiting O-GlcNAcylation can reduce pancreatic tumour growth and progression suggesting HBP is promising potential therapeutic target (66,71,72).…”

Targeting tumor-intrinsic metabolic node sensitizes pancreatic cancer to anti-PD1 therapy

“…Further, since UDP-GlcNAc is used by O-GlcNAc transferase (OGT) to glycosylate and regulate a large number of oncogenic proteins (like Myc), inhibition of UDP-GlcNAc production will affect the survival of the cancer cells (31). Consistent with this, previous studies from our laboratory have shown that HBP-fueled UDP-GlcNAc synthesis can be used by OGT to drive tumor growth and self-renewal (32,33). Thus, HBP forms an integral metabolic node, inhibition of which will affect the tumor and its microenvironment alike.…”

“…These are dependent on the genes that regulate self-renewal. Our previous results (32) show that OGT, an enzyme dependent on UDP-GlcNAc and thus HBP, was instrumental in regulating self-renewal in pancreatic cancer via its effect on Sox2. Our results showed that inhibition of GFAT1, the rate-limiting enzyme of HBP, using siRNA resulted in inhibition of a number of self-renewal genes like Sox2, Oct4 and KLF4 in the pancreatic cancer cell lines MIA-PaCa2 and S2VP10 (Figure 2A).…”