Loss of ASRGL1 expression is an independent biomarker for disease-specific survival in endometrioid endometrial carcinoma.

OBJECTIVE: For endometrial carcinoma, prognostic stratification methods do not satisfactorily identify patients with adverse outcome. Currently, histology, tumor grade and stage are used to tailoring surgical treatment and to determine the need for adjuvant treatment. Low-risk patients are not considered to require adjuvant therapy or staging lymphadenectomy. For patients with intermediate or high risk, some guidelines recommend tailoring adjuvant treatment according to additional negative prognostic factors. Our objective was to evaluate the biomarker potential of the ASRGL1 protein in endometrial carcinoma. METHODS: Using The Human Protein Atlas (www.proteinatlas.org), the l-asparaginase (ASRGL1) protein was identified as an endometrial carcinoma biomarker candidate. ASRGL1 expression was immunohistochemically evaluated with an extensively validated antibody on two independent endometrial carcinoma cohorts (n=229 and n=286) arranged as tissue microarrays. Staining results were correlated with clinical features. RESULTS: Reduced expression of ASRGL1, defined as <75% positively stained tumor cells, was significantly associated with poor prognosis and reduced disease-specific survival in endometrioid endometrial adenocarcinoma (EEA). In multivariate analysis the hazard ratios for disease-specific survival were 3.55 (95% CI=1.10-11.43; p=0.003) and 3.23 (95% CI=1.53-6.81; p=0.002) in the two cohorts, respectively. Of the 48 cases with Grade 3 Stage I tumor all disease-related deaths were associated with low ASRGL1 expression. CONCLUSIONS: Loss of ASRGL1 in EEA is a powerful biomarker for poor prognosis and retained ASRGL1 has a positive impact on survival. ASRGL1 immunohistochemistry has potential to become an additional tool for prognostication in cases where tailoring adjuvant treatment according to additional prognostic factors besides grade and stage is recommended.

Biochemical and pathophysiological characterization of Helicobacter pylori asparaginase.

Asparaginase was purified from Helicobacter pylori 26695 and its pathophysiological role explored. The K(m) value of asparagine was 9.75 ± 1.81 µM at pH 7.0, and the optimum pH range was broad and around a neutral pH. H. pylori asparaginase converted extracellular asparagine to aspartate. H. pylori cells were unable to take up extracellular asparagine directly. Instead, aspartate produced by the action of the asparaginase was transported into H. pylori cells, where it was partially converted to ß-alanine. Asparaginase exhibited striking cytotoxic activity against histiocytic lymphoma cell line U937 cells via asparagine deprivation. The cytotoxic activity of live H. pylori cells against U937 cells was significantly diminished by deletion of the asparaginase gene, indicating that asparaginase functions as a cytotoxic agent of the bacterium. The cytotoxic effect was negligible for gastric epithelial cell line AGS cells, suggesting that the effect differs across host cell types. An asparaginase-deficient mutant strain was significantly less capable of colonizing Mongolian gerbils. Since asparagine depletion by exogenous asparaginase has been shown to suppress lymphocyte proliferation in vivo, the present results suggest that H. pylori asparaginase may be involved in inhibition of normal lymphocyte function at the gastric niche, allowing H. pylori to evade the host immune system.

Neuroprotective actions of PIKE-L by inhibition of SET proteolytic degradation by asparagine endopeptidase.

Ischemia and seizure cause excessive neuronal excitation that is associated with brain acidosis and neuronal cell death. However, the molecular mechanism of acidification-triggered neuronal injury is incompletely understood. Here, we show that asparagine endopeptidase (AEP) is activated under acidic condition, cuts SET, an inhibitor of DNase, and triggers DNA damage in brain, which is inhibited by PIKE-L. SET, a substrate of caspases, was cleaved by acidic cytosolic extract independent of caspase activation. Fractionation of the acidic cellular extract yielded AEP that is required for SET cleavage. We found that kainate provoked AEP activation and SET cleavage at N175, triggering DNA nicking in wild-type, but not AEP null, mice. PIKE-L strongly bound SET and prevented its degradation by AEP, leading to resistance of neuronal cell death. Moreover, AEP also mediated stroke-provoked SET cleavage and cell death in brain. Thus, AEP might be one of the proteinases activated by acidosis triggering neuronal injury during neuroexcitotoxicity or ischemia.

Use of the polyethylene glycol adduct of L-asparaginase for the treatment of hyperasparaginemia in a schizophrenic patient.

A man with hyperasparaginemia, presumably due to chronic deficiency of asparaginase activity, had been schizophrenic and unresponsive to antipsychotic drugs for at least 22 years. He was given repeated injections of bacterial L-asparaginase rendered relatively nonimmunogenic by covalent binding to polyethylene glycol (PEG). PEG-asparaginase lowered plasma asparagine concentrations from 4 to 5 SD above normal down to undetectable levels, and eliminated asparagine from the cerebrospinal fluid. Despite biochemical correction lasting at least 55 days, the patient did not improve psychiatrically. Experience limited to this single patient suggests that PEG-asparaginase therapy is relatively innocuous, but does not clarify whether there is an etiological relationship between hyperasparaginemia and psychiatric illness.

Hyperasparaginemia in a schizophrenic patient.

A man with a chronic schizophrenia-like psychotic disorder had fasting plasma asparagine concentrations that were consistently 4 to 8 SD above the normal level. Asparagine levels were also high in his cerebrospinal fluid (CSF) and erythrocytes. Ornithine, proline, and glutamate concentrations were irregularly high in fasting plasma, and gamma-aminobutyric acid (GABA) concentrations were elevated in CSF. Whether or not these biochemical abnormalities were related to the psychotic disorder is unclear. However, increased asparagine concentrations, possibly due to an enzymatic deficiency of asparaginase, could lead to deregulation of polyamine biosynthesis and to excessive production of GABA from putrescine. These biochemical changes could in turn cause disordered brain function. A search in mentally ill patients for metabolic abnormalities involving asparagine, or other amino acids, might hasten elucidation of the biochemical basis of the schizophrenias.