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Metabolism drives growth and division of cancer cells

 The metabolic status of the cell and its supply of nutrients is signaled, amongst other, by the O-linked N-acetylglucosamine (GlcNAc) transferase (OGT). This enzyme links GlcNAc (orange squares) as a mark to STAT5 at the OH groups of threonine 92 (T). Cytokine receptors activate the kinase JAK2, which phosphorylates STAT5 on tyrosine 694 (Y) (red circles).

The metabolic state of tumor cells contributes to signals that control the proliferation of tumor cells. Already the German biochemist and Nobel Prize laureate Otto H. Warburg observed in the 1920s that tumor cells radically change their metabolism. This process was termed "Warburg Effect", however neglected until recently by cancer research, but the latest results show it is indeed of fundamental importance for the development of aggressive tumors. Richard Moriggl and his co-workers have now published in the journal Leukemia how the tumor promoter STAT5 integrates metabolic signals that contribute to oncogenic transformation. Researchers from the Ludwig Boltzmann Institute for Cancer Research, Vetmeduni and Meduni Wien may have thus identified a new target to tackle cancer.

The sugar molecule UDP-GlcNAc serves as an indicator for the energy supply of the cell. If the cell is well supplied with nutrients, this molecule is abundant and signals to the cell that the tank is full. A specific enzyme (OGT) can attach this sugar molecule to a variety of proteins as a marker, thus controlling metabolic processes. "We are investigating STAT5, which can be marked with GlcNAc at a specific site (T92). By means of genetic engineering we have produced a variant of STAT5, which cannot carry this chemical group to decipher its influence on this oncogene. This variant is, so to speak, blind to the indicator and simulates the state of an empty tank ", explains the first author Patricia Freund from the Institute for Animal Breeding and Genetics at the University of Veterinary Medicine Vienna.

The researchers have now discovered that the STAT5 variant is not persistently tyrosine-phosphorylated without GlcNAc labeling. Thus, the sustained activation which is necessary for a transformation of cells into cancer cells is lacking. "If the tank is empty, the cell cannot divide," explains Moriggl. The signals of a good supply of nutrients, ie a high concentration of UDP-GlcNAc, are a precondition that oncogenic signals reach the cell nucleus via STAT5. "So we can turn off STAT5 if we trick it into believing the cell's nutrient supply is exhausted. We together with our collaboration partners will now perform experiments to explore whether this principle might have therapeutic potential,” emphasizes Moriggl the translational aspects of his research.

This research was carried out with financial support by the private Melanoma Donation in Liechtenstein and was partly funded by the FWF through SFB-F28 „Jak-Stat Signalling: from Basics to Disease“ and SFB-F47 "Myeloid Neoplasia".

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