Marked improvement in hyperammonaemic encephalopathy from multimodal treatment of metastatic neuroendocrine tumour

Non-cirrhotic hyperammonaemic encephalopathy secondary to metastatic pancreatic neuroendocrine tumour treated with peptide receptor radio nucleotide therapy and transarterial chemoembolisation

Neuroendocrine tumours (NETs) are rare cancers which often carry significant morbidity and mortality, frequently related to burden of liver metastases. Hyperammonaemia and subsequent hepatic encephalopathy carries a poor prognosis and has been described in these patients. We discuss a case of a woman in her 50s with hyperammonaemic encephalopathy and a new diagnosis of pancreatic NET with hepatic metastases. She presented with a reduced conscious state a few days post commencing chemotherapy. This was considered to have a multifactorial pathophysiology: the primary driver being large volume hepatic metastases and contributed by portosystemic microshunting, sepsis, severe weight loss and malnutrition. We describe how each of these exacerbating factors was addressed and highlight the effective multimodal treatment approach consisting of sequential transarterial chemoembolisation followed by peptide receptor radio nucleotide therapy, resulting in the resolution of hyperammonaemic encephalopathy and radiological partial metabolic response.

Metabolic Heterogeneity, Plasticity, and Adaptation to "Glutamine Addiction" in Cancer Cells: The Role of Glutaminase and the GTωA [Glutamine Transaminase-ω-Amidase (Glutaminase II)] Pathway

Many cancers utilize l-glutamine as a major energy source. Often cited in the literature as "l-glutamine addiction", this well-characterized pathway involves hydrolysis of l-glutamine by a glutaminase to l-glutamate, followed by oxidative deamination, or transamination, to α-ketoglutarate, which enters the tricarboxylic acid cycle. However, mammalian tissues/cancers possess a rarely mentioned, alternative pathway (the glutaminase II pathway): l-glutamine is transaminated to α-ketoglutaramate (KGM), followed by ω-amidase (ωA)-catalyzed hydrolysis of KGM to α-ketoglutarate. The name glutaminase II may be confused with the glutaminase 2 (GLS2) isozyme. Thus, we recently renamed the glutaminase II pathway the "glutamine transaminase-ω-amidase (GTωA)" pathway. Herein, we summarize the metabolic importance of the GTωA pathway, including its role in closing the methionine salvage pathway, and as a source of anaplerotic α-ketoglutarate. An advantage of the GTωA pathway is that there is no net change in redox status, permitting α-ketoglutarate production during hypoxia, diminishing cellular energy demands. We suggest that the ability to coordinate control of both pathways bestows a metabolic advantage to cancer cells. Finally, we discuss possible benefits of GTωA pathway inhibitors, not only as aids to studying the normal biological roles of the pathway but also as possible useful anticancer agents.