O-GlcNAcylation of the Tumor Suppressor FOXO3 Triggers Aberrant Cancer Cell Growth

Abstract

Posttranslational modifications of tumor suppressors can induce abnormal cell growth. Here, we identify site-specific -GlcNAcylation as a critical block of FOXO3 that may abrogate a part of the p53 pathway, resulting in aberrant cancer cell growth. Of seven-GlcNAcylation sites identified within the FOXO3 transactivation domain, we found that changes in -GlcNAcylation at Ser284 modulated p21-mediated cancer cell growth. Overexpression of either-GlcNAcylated FOXO3 (FOX-OV) or a Ser-to-Ala mutant (S284A) in PANC-1 cells indicated that S284 -GlcNAc acts as a critical block of the FOXO tumor suppressor and induces proliferation in PANC-1 cancer cells by stimulating the MDM2-p53-p21 axis. Furthermore, S284A mutant cells lacking S284-GlcNAc and FOX-OV cells exhibited opposing MDM2-p53-p21 axis expression patterns at both the mRNA and protein levels. Thus, our study provides evidence to support a role for S284 -GlcNAc as a critical block of FOXO3 to induce subsequent cancer cell growth via abrogation of the p53 regulatory circuit. These findings highlight a posttranslational mechanism for indirect abrogation of the p53 pathway, one that may occur with some frequency in human cancer cells. .

Fueling the fire: emerging role of the hexosamine biosynthetic pathway in cancer

“…In pancreatic cancer cells, FOXO3 is highly O-GlcNAc modified on S284 and this modification blocks FOXO3 function, leading to subsequent cancer cell growth (Fig. 4) [70]. O-GlcNAcylation can also directly regulate the activity of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor.…”

Real Talk: The Inter-play Between the mTOR, AMPK, and Hexosamine Biosynthetic Pathways in Cell Signaling

“…The addition and removal of O-GlcNAc is facilitated solely by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) ( 2 ), so the coordinated activity of these two enzymes creates a versatile signaling dynamic that can quickly alter signaling pathways ( 3 ). Therefore, a wide scope of cellular processes is controlled and fine-tuned by O-GlcNAc, including apoptosis, mitochondrial function, proliferation, and gene transcription ( 4 – 9 ). Because O-GlcNAc plays such a crucial and diverse role in eukaryotic cells, atypical O-GlcNAcylation can be a driving force in a variety of pathologies.…”

“…Because O-GlcNAc plays such a crucial and diverse role in eukaryotic cells, atypical O-GlcNAcylation can be a driving force in a variety of pathologies. Alzheimer's disease ( 10 ), diabetes, and several types of cancers have been linked to abnormal levels or behavior of O-GlcNAc, OGT, and OGA ( 5 , 9 – 16 ). Research into the underlying reasons behind these physiological aberrations has yielded a plethora of new insights into cell signaling mechanisms and the role of O-GlcNAc in overall cellular function, particularly nutrient-sensing.…”

Hyalinizing epithelioid tumors with OGT‐FOXO fusions. A case report of a non‐acral soft tissue mass harboring a novel FOXO4 gene rearrangement

“…Of note, FOXO proteins are among the substrates of OGT and can be glycosylated and activated under oxidative stress 10 . Furthermore, overexpression of O‐GlcNAcylated FOXO3 has been shown to stimulate growth of cancer cells 11 . Moreover, all tumors reported to date with OGT related fusions (including our current case) contain a nearly full‐length OGT transcript (Figure 2).…”

“…(G,H) Low and high-power magnification showing strong and diffuse positivity for CK AE1:AE3, while (I) show some weak nuclear expression for FLI1 (lower intensity than the internal positive control endothelial cells) shown to stimulate growth of cancer cells. 11 Moreover, all tumors reported to date with OGT related fusions (including our current case) contain a nearly full-length OGT transcript (Figure 2).…”