Prognostic and predictive biomarkers in central nervous system tumours: the molecular state of play

Central nervous system (CNS) tumours were one of the first cancer types to adopt and integrate molecular profiling into routine clinical diagnosis in 2016. The vast majority of these biomarkers, used to discriminate between tumour types, also offered prognostic information. With the advent of The Cancer Genome Atlas (TCGA) and other large genomic datasets, further prognostic sub-stratification was possible within tumour types, leading to increased precision in CNS tumour grading. This review outlines the evolution of the molecular landscape of adult CNS tumours, through the prism of World Health Organization (WHO) Classifications. We begin our journey in the pre-molecular era, where high-grade gliomas were divided into 'primary' and 'secondary' glioblastomas. Molecular alterations explaining these clinicopathological observations were the first branching points of glioma diagnostics, with the discovery of IDH1/2 mutations and 1p/19q codeletion. Subsequently, the rigorous characterisation of paediatric gliomas led to the unearthing of histone H3 alterations as a key event in gliomagenesis, which also had implications for young adult patients. Simultaneously, studies investigating prognostic biomarkers within tumour types were undertaken. Certain genomic phenotypes were found to portend unfavourable outcomes, for example, MYCN amplification in spinal ependymoma. The arrival of methylation profiling, having revolutionised the diagnosis of CNS tumours, now promises to bring increased prognostic accuracy, as has been shown in meningiomas. While MGMT promoter hypermethylation has remained a reliable biomarker of response to cytotoxic chemotherapy, targeted therapy in CNS tumours has unfortunately not had the success of other cancers. Therefore, predictive biomarkers have lagged behind the identification of prognostic biomarkers in CNS tumours. Emerging research from new clinical trials is cause for guarded optimism and may shift our conceptualisation of predictive biomarker testing in CNS tumours.

Chronic Traumatic Encephalopathy in a Routine Neuropathology Service in Australia

Chronic traumatic encephalopathy (CTE) is a neuropathological diagnosis defined by a unique pattern of hyperphosphorylated tau (p-tau) accumulation that begins in neocortical regions of the brain. It is associated with a range of neuropsychological symptoms, but a definitive diagnosis can only be made by postmortem brain examination. In 2018, we instituted CTE screening for all autopsy brains as part of our routine departmental protocol by performing p-tau immunohistochemistry on a restricted set of 3 neocortical blocks (frontal, temporal, and parietal). This strategy allowed us to identify 4 cases of low-stage CTE from 180 consecutive autopsies. Two of the 4 cases had a documented history of brain injury; for the remaining 2 cases, there was a long history of treatment-resistant tonic/clonic epilepsy suggesting that undocumented brain injuries may have occurred. Our experience indicates that 3-block CTE screening is useful in identifying CTE in routine practice. The results of this study further support the association between prior head injuries and CTE and demonstrate that, albeit uncommon, CTE does occur in the general population. Our findings suggest that p-tau screening should be routinely pursued in brain autopsy, particularly where there is a documented or likely history of traumatic brain injury.

Patterns of care in adult histone mutant gliomas: results of an international survey

Background

Histone mutant gliomas (HMG) with histone H3 K27 and G34 mutations are recognized as biologically discrete entities with distinct anatomical locations, a younger age at presentation (in comparison to the most common high grade gliomas, IDH wild type glioblastoma) and poor prognosis. There is a paucity of data regarding management of adult HMG patients and no consensus for management. This study aims to identify current patterns of Australian and US neuro-oncology clinical practice for this entity.

Methods

Following institutional approvals, a patterns of care questionnaire designed to capture relevant clinical variables was circulated through the Cooperative Trials Group for Neuro-Oncology (COGNO) in Australia and the Caris Precision Oncology Alliance in the United States (US).

Results

Between 4/2021 and 10/2021, 43 responses were collected. 33% (n=14) of responders tested all patients for HMGs routinely; 40.92% (n=18) tested in select patients 26% (n=11) did not test for HMGs. The common indications for testing selected patients were midline anatomic location (n=18) and age (n=11) (<50 years). 23 used molecular sequencing, 22 used IHC at their centres.

Nine participants stated knowledge of histone H3 mutation did not affect their management of these gliomas, 11 said it affected their management at the time of recurrence, 23 stated it affected management of midline K27M patients, 11 participants stated it affected management of K27M mutant gliomas in other locations and 3 felt it affected management of G34R/V mutant gliomas.

Conclusion

Here we present a description of how the discovery of a new molecular subtype of primary glial tumours, histone mutated gliomas in adults, is being introduced into clinical practice.

Progressive multifocal leukoencephalopathy post ibrutinib therapy in relapsed chronic lymphocytic leukaemia

Progressive multifocal leukoencephalopathy (PML) is a generally fatal infection of the cerebrum by the JC virus. It occurs in a range of primary and secondary immunosuppressed states and has become more common with AIDS and increasing the use of immunosuppressive therapies. Recently, Ibrutinib, a Bruton's Tyrosine Kinase Inhibitor (BTKi), has also been associated with PML. Here, we describe the case of a 77-year-old man treated for relapsed Chronic Lymphocytic Leukemia (CLL) with Ibrutinib, who eventually developed a fatal cerebellar granule cell variant of PML confirmed on autopsy. The case adds to the growing body of literature finding such an association with BTKis and highlights the importance of clinical vigilance in patients receiving such therapy.

PATH-18. A MULTI-CENTER CASE SERIES OF ADULT K27M MUTATED DIFFUSE MIDLINE GLIOMAS REVEALING A POPULATION UNIQUE FROM PAEDIATRIC CASES

BACKGROUND

Histone mutations in the K27M gene were first described in 2014, and incorporated into the WHO CNS tumour classification system in 2016. They are typically associated with diffuse midline gliomas (DMG). Presenting symptoms vary greatly, with some experiencing significant delay in diagnosis. Median survival is only 9-12 months for these patients. Biopsy samples are small, and in some due to location, not performed. Although data is predominately based on the paediatric population, DMGs are seen in both adolescence and adults. In this multi-site retrospective study, we describe 11 adult patients with K27M DMG gliomas across two tertiary Neuro-Oncology services in Sydney, Australia. To the authors’ knowledge we present the largest known collection of adult K27M cases in the Asia-Pacific region with correlation of treatment, clinicopathologic and radiologic features with outcomes.

METHODS

The glioma databases of Royal North Shore Hospital (RNSH) and Royal Prince Alfred Hospital (RPAH) between January 2009 and March 2020 were interrogated to identify patients. Selection criteria included patients aged ≥ 18 years who presented with a DMG, had undergone biopsy, and had confirmed K27M via next generation sequencing. Clinicopathologic, radiologic and treatment outcomes were extracted for correlation.

RESULTS

Eleven patients fitting the selection criteria were identified and reported. The median age at diagnosis was 30 years and 4 were female. Five presented with hydrocephalus, the most common presenting symptoms were headaches and nausea and/or vomiting (n= 4 and n= 2 respectively). The median progression-free survival was 13 months (4-31 months) and the median overall survival was 23 months (4-59 months).

CONCLUSION

This case series reports the outcomes of older patients with K27M. The clinical course demonstrated suggests a divergence from paediatric biology. Ongoing studies are required to further characterise the histopathological and clinical differences of these tumours in older patients.

Deep Sequencing of Small RNAs from Neurosurgical Extracellular Vesicles Substantiates miR-486-3p as a Circulating Biomarker that Distinguishes Glioblastoma from Lower-Grade Astrocytoma Patients

Extracellular vesicles (EVs) play key roles in glioblastoma (GBM; astrocytoma grade IV) biology and are novel sources of biomarkers. EVs released from GBM tumors can cross the blood-brain-barrier into the periphery carrying GBM molecules, including small non-coding RNA (sncRNA). Biomarkers cargoed in circulating EVs have shown great promise for assessing the molecular state of brain tumors in situ. Neurosurgical aspirate fluids captured during tumor resections are a rich source of GBM-EVs isolated directly from tumor microenvironments. Using density gradient ultracentrifugation, EVs were purified from cavitron ultrasonic surgical aspirate (CUSA) washings from GBM (n = 12) and astrocytoma II-III (GII-III, n = 5) surgeries. The sncRNA contents of surgically captured EVs were profiled using the Illumina^® NextSeq^TM 500 NGS System. Differential expression analysis identified 27 miRNA and 10 piRNA species in GBM relative to GII-III CUSA-EVs. Resolved CUSA-EV sncRNAs could discriminate serum-EV sncRNA profiles from GBM and GII-III patients and healthy controls and 14 miRNAs (including miR-486-3p and miR-106b-3p) and cancer-associated piRNAs (piR_016658, _016659, _020829 and _204090) were also significantly expressed in serum-EVs. Circulating EV markers that correlate with histological, neuroradiographic and clinical parameters will provide objective measures of tumor activity and improve the accuracy of GBM tumor surveillance.

A Comprehensive Proteomic SWATH-MS Workflow for Profiling Blood Extracellular Vesicles: A New Avenue for Glioma Tumour Surveillance

Improving outcomes for diffuse glioma patients requires methods that can accurately and sensitively monitor tumour activity and treatment response. Extracellular vesicles (EV) are membranous nanoparticles that can traverse the blood-brain-barrier, carrying oncogenic molecules into the circulation. Measuring clinically relevant glioma biomarkers cargoed in circulating EVs could revolutionise how glioma patients are managed. Despite their suitability for biomarker discovery, the co-isolation of highly abundant complex blood proteins has hindered comprehensive proteomic studies of circulating-EVs. Plasma-EVs isolated from pre-operative glioma grade II-IV patients (n = 41) and controls (n = 11) were sequenced by Sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS) and data extraction was performed by aligning against a custom 8662-protein library. Overall, 4054 proteins were measured in plasma-EVs. Differentially expressed proteins and putative circulating-EV markers were identified (adj. p-value < 0.05), including those reported in previous in-vitro and ex-vivo glioma-EV studies. Principal component analysis showed that plasma-EV protein profiles clustered according to glioma histological-subtype and grade, and plasma-EVs resampled from patients with recurrent tumour progression grouped with more aggressive glioma samples. The extensive plasma-EV proteome profiles achieved here highlight the potential for SWATH-MS to define circulating-EV biomarkers for objective blood-based measurements of glioma activity that could serve as ideal surrogate endpoints to assess tumour progression and allow more dynamic, patient-centred treatment protocols.

Extracellular Vesicles from Neurosurgical Aspirates Identifies Chaperonin Containing TCP1 Subunit 6A as a Potential Glioblastoma Biomarker with Prognostic Significance

Glioblastoma, WHO-grade IV glioma, carries a dismal prognosis owing to its infiltrative growth and limited treatment options. Glioblastoma-derived extracellular vesicles (EVs; 30-1000 nm membranous particles) influence the microenvironment to mediate tumor aggressiveness and carry oncogenic cargo across the blood-brain barrier into the circulation. As such, EVs are biomarker reservoirs with enormous potential for assessing glioblastoma tumors in situ. Neurosurgical aspirates are rich sources of EVs, isolated directly from glioma microenvironments. EV proteomes enriched from glioblastoma (n = 15) and glioma grade II-III (n = 7) aspirates are compared and 298 differentially-abundant proteins (p-value < 0.00496) are identified using quantitative LC-MS/MS. Along with previously reported glioblastoma-associated biomarkers, levels of all eight subunits of the key molecular chaperone, T-complex protein 1 Ring complex (TRiC), are higher in glioblastoma-EVs, including CCT2, CCT3, CCT5, CCT6A, CCT7, and TCP1 (p < 0.00496). Analogous increases in TRiC transcript levels and DNA copy numbers are detected in silico; CCT6A has the greatest induction of expression and amplification in glioblastoma and shows a negative association with survival (p = 0.006). CCT6A is co-localized with EGFR at 7p11.2, with a strong tendency for co-amplification (p < 0.001). Immunohistochemistry corroborates the CCT6A proteomics measurements and indicated a potential link between EGFR and CCT6A tissue expression. Putative EV-biomarkers described here should be further assessed in peripheral blood.

Microtomy: Cutting Formalin-Fixed, Paraffin-Embedded Sections

Formalin-fixed, paraffin-embedded tissue (FFPE) still plays an important role in biobanking, since it is comparatively easy to obtain and store in comparison to fresh frozen tissue. They are stored as paraffin or FFPE blocks. Unstained slides derived from FFPE blocks may be used for hematoxylin and eosin histology, special stains, immunohistochemistry, and chromogenic or fluorescent in situ hybridization. In addition, tissue scraped off FFPE slides or from scrolls of FFPE tissue may be used for molecular or proteomic analyses. Hematoxylin and eosin staining of FFPE sections reviewed by a pathologist are highly valuable to ensure the presence of adequate lesional cells for molecular and other analyses. Therefore, proper microtomy technique is essential in the preparation of formalin-fixed, paraffin-embedded tissue for biobanking purposes. Here we describe the process of cutting paraffin embedded sections using a rotary microtome. We also highlight the possible pitfalls that may arise and discuss how to avoid them.

Rheumatoid leptomeningitis presenting with an acute neuropsychiatric disorder

Leptomeningitis is a rare central nervous system manifestation of rheumatoid arthritis, generally in patients with established chronic rheumatoid disease. We report a 41-year-old man without previous rheumatoid arthritis or psychiatric disorder who presented with an acute neuropsychiatric disturbance and polyarthralgia. His MR scan of brain showed asymmetric bifrontal leptomeningitis, confirmed on (18F)-fluoro-D-glucose-positron emission tomography. Other investigations showed highly positive serum and cerebrospinal fluid anti-cyclic citrullinated peptide. A leptomeningeal biopsy showed necrotising leptomeningeal inflammation with ill-defined granulomas and lymphoplasmacytic infiltrate without organisms. Prolonged high-dose corticosteroids and then rituximab resulted in recovery. Chronic leptomeningitis can present with an acute neuropsychiatric disorder. We highlight that early rheumatoid disease can, rarely, cause a chronic leptomeningitis, reversible with immunotherapy.

037 Post-transplant lymphoproliferative disorder in skeletal muscle arising seven years after allogeneic stem cell transplant

Introduction

Post-transplant lymphoproliferative disorder (PTLD) is a well-recognised serious complication of transplantation. However, it rarely affects muscle.

Methods

A case report detailing presentation, evaluation, management and outcome of a patient with acute on chronic proximal myopathy on a background of allogeneic stem cell transplant is described. The patient was diagnosed with PTLD affecting skeletal muscle.

Results

A 54 year old man presented with painful proximal myopathy seven years after successful allogeneic stem cell transplant for acute myeloid leukaemia. He had been managed with immunosuppression for extensive cutaneous graft versus host disease (GVHD) from the time of transplant. Initial quadriceps muscle biopsy showed changes in keeping with GVHD and features suggestive of drug-related necrotising myositis. The painful myalgia evolved to include bulbar muscles with dysphagia despite pulse steroid and intravenous immunoglobulin therapy. A positron emission tomography (PET) scan demonstrated intense and extensive hyper-metabolism in multiple muscle groups in keeping with diffuse myositis with the most prominent activity involving neck muscles, the left shoulder girdle and left arm musculature. A second biopsy of the sternocleidomastoid demonstrated infiltration with haematolymphoid cells consistent with post-transplant lymphoproliferative disorder. Treatment with reduction in immunosuppression, rituximab and rehabilitation saw improvement in myalgia and weakness. Unfortunately, exacerbation of chronic GVHD ensued following reduction in immunosuppression and contributed to oesophageal stricturing eventually requiring a percutaneous endoscopic gastrostomy tube for feeding.

Conclusion

This case highlights the complex morbidity of allogeneic stem cell transplant and the need to consider PTLD in the differential for patients who present with neurological symptoms.

043 Rheumatoid leptomeningitis: an acute presentation of neuropsychiatric disturbance

Introduction

We report a case of an isolated acute neuropsychiatric presentation due to rheumatoid meningitis (RM), successfully treated with steroids and rituximab.

Case

A 41 year old man with a chronic headache and acute neuropsychiatric disturbance including impulsivity, grandiose delusions and agitation on a background of no known psychiatric history. Incidentally, he reported migratory palindromic, large and small joint polyarthritis over the preceding 18 months accompanied by headache, symptomatically treated with indomethacin. He had no prior diagnosis of rheumatoid arthritis (RA) or other connective tissue disorder. Serum and cerebrospinal fluid (CSF) cyclic citrullinated peptide antibodies were strongly positive, with a normal serum rheumatoid factor. An interferon-gamma release assay was positive, suggestive of prior tuberculosis (TB) exposure. CSF examination was unremarkable with an MRI brain demonstrating asymmetric features of leptomeningeal thickening and enhancement over both cerebral cortices, suggesting an inflammatory or infiltrative leptomeningitis. Lymphoma, IgG4–related disease, granulomatous diseases such as TB, granulomatosis with polyangiitis, neurosarcoidosis, neurosyphilis and meningeal metastasis were considered as differential diagnoses. A leptomeningeal and brain biopsy showed necrotising inflammation with ill-defined granulomas and a dense lymphoplasmacytic infiltrate. No organisms were identified. Mycobacterial polymerase chain reaction and cultures over three months were negative. RM was the favoured histological diagnosis. Empirical treatment for prior TB exposure was commenced in conjunction with steroids. Subsequent addition of iv rituximab resulted in sustained improvement of neuropsychiatric and joint symptoms.

Conclusion

This report illustrates for the first time isolated acute neuropsychiatric disturbances attributable to RM without a prior history of RA that was responsive to rituximab. Clinicians should consider infiltrative and inflammatory leptomeningeal causes, particularly with asymmetric meningeal thickening and enchantment on MRI and should commit to a tissue biopsy when no other systemic connective tissue, infective or neoplastic causes are identified.

038 Adult-onset leukoencephalopathy with neuroaxonal spheroids and pigmented glia mimicking systemic lupus erythematosus cerebral vasculitis

Introduction

We present an unusual case of adult-onset leukoencephalopathy with neuroaxonal spheroids and pigmented glia (ALSP) mimicking systemic lupus erythematosus (SLE) cerebral vasculitis. ALSP is an autosomal dominant progressive leukodystrophy, associated with mutations in the CSF1R gene, which induce dysregulation of microglia. The case was compiled from records of clinical data, imaging, brain biopsy and genetic studies.

Case

A 56 year old previously high functioning man of Southern Chinese origin was hospitalised with recurrent seizures. He had a prior 4 year history of progressive neuropsychiatric features, and 1 year of cognitive decline and occasional falls. Within the year prior, he had positive SLE serology and a renal biopsy consistent with lupus nephritis treated with steroids, mycophenolate, hydroxyl-chloroquine, and later rituximab due to concerns of evolving cerebral vasculitis on cerebral MRI and SPECT scan with MoCA of 20/30. Examination after seizure therapy revealed hyperreflexia, fine tremor, myoclonus, pseudobulbar affect, ideomotor apraxia and slow, independent gait. RUDAS was 6/30 with perseveration. CSF examination and SLE serology were quiescent. Consecutive brain MRIs showed multiple regions of worsening high T2/FLAIR signal in the corpus callosum and supra-tentorial white matter with persistent restricted diffusion. IV steroids and cyclophosphamide were added. Following treatment unresponsiveness, a frontal lobe brain biopsy demonstrated white matter gliosis with prominent axonal spheroids consistent with a primary leukoencephalopathy, with no inflammation, vasculitis nor infection. Immunotherapy was weaned. Genetic testing confirmed a positive CSF1R mutation (c.2329C>T; p. Arg777Trp in Exon 18). A positive family history of dementia in the patient’s elderly mother overseas was identified. The patient remained mobile but mute, and fatally aspirated 8 months after final presentation.

Conclusion

This report illustrates an unusual presentation of ALSP, initially misdiagnosed as SLE vasculitis. Clinicians should consider an adult onset leukodystrophy and proceed to biopsy and CSF1R gene testing early in suspected ‘refractory cerebral vasculitis’.

Cytomorphologic spectrum of mixed pituitary adenoma-gangliocytomas: a report of two cases

BACKGROUND

Mixed pituitary adenoma-gangliocytomas are rare tumors with a broad morphologic spectrum. Smear cytology is a useful tool for recognizing these tumors in an intraoperative setting.

CASES

The patients were 45 and 30 years old, and both presented with headache. Intraoperative smears in both cases showed a tumor composed of adenomatous and neuronal elements, in varying proportions. The first case had sheets of monotonous neuroendocrine-type cells with occasional interspersed ganglion cells. The second case, however, had a prominent fibrillary background and was predominantly neurocytic, with a mixture of large ganglion-like cells, intermediate cells, and only rare adenomatous cells.

CONCLUSION

The diagnostic features of mixed pituitary adenoma-gangliocytomas can be recognized on intraoperative smear preparations. Smear preparations are often more useful than frozen sections because freezing artifacts may mask one of the two components of the tumor. The proportion of adenomatous and neuronal elements can vary widely from case to case. Careful search for a neuronal component should be made, especially if there is a clinical history of a pituitary adenoma showing incomplete response to hormonal therapy.

Tumor budding and survival after potentially curative resection of node-positive colon cancer

PURPOSE

The aim of this study was to investigate the relationship between tumor budding and other pathology features and overall survival after resection of clinicopathological stage III colon cancer.

METHODS

The number of buds and other histopathological features were assessed in 477 patients who were operated on between 1971 and 2001, with follow-up to December 2006. Overall survival was analyzed using the Kaplan-Meier method and Cox regression.

RESULTS

The number of buds was dichotomized as low (0 to 8) vs high (>or=9). High budding was more common in men, in high-grade tumors, in the presence of venous invasion, and where the tumor had involved a free serosal surface, but budding was not associated with 8 other clinical and pathological features. The 5-year survival rate for patients with 0 to 8 buds was 51.0% (95% confidence interval, 44.9-55.1), whereas that for patients with 9 or more buds was 33.9% (95% confidence interval, 25.2-42.8). This association, however, disappeared after adjustment for other variables independently associated with survival (hazard ratio, 1.2; 95% confidence interval, 0.94-1.54; P = .139).

CONCLUSION

In stage III colon cancer, tumor budding did not provide additional independent prognostic information beyond that given by routine pathology reporting.

Hospitalized congestive heart failure patients with preserved versus abnormal left ventricular systolic function: clinical characteristics and drug therapy

PURPOSE

To compare clinical characteristics of and pharmacologic therapy for hospitalized patients with congestive heart failure (CHF) and left ventricular systolic dysfunction or normal left ventricular systolic function.

PATIENTS AND METHODS

Medical records were reviewed for all patients discharged with a principal diagnosis of CHF from a university hospital and a community hospital between September 1, 1991 and August 31, 1992. Pertinent medical history items and prescribed drug therapies at discharge were recorded for each patient's first calendar year admission. Patients were categorized as having either normal left ventricular systolic function or systolic dysfunction based on the results of echocardiography and radionuclide angiography or contrast ventriculogram.

RESULTS

Of 298 patients with CHF, 92 (31%) had normal left ventricular systolic function. Patients with normal systolic function were older, were more often women, were less likely to have a history of coronary artery disease, and were more likely to have a history of hypothyroidism than patients with systolic dysfunction. However, the prevalence of clinical characteristics overlapped considerably between the two groups. Among patients with systolic dysfunction, 79% were discharged on a therapeutic regimen of digoxin, 65% on an angiotensin-converting enzyme inhibitor, and 26% on either a beta-blocker or a calcium channel blocker. Among patients with normal systolic function, 50% were discharged on a regimen of a beta-blocker or a calcium channel blocker and 38% were discharged on digoxin. Twenty-six percent of patients with normal systolic function and without a history of atrial fibrillation were discharged on a digoxin regimen.

CONCLUSION

Hospitalized CHF patients with normal left ventricular systolic function and those with diminished left ventricular systolic function share many clinical features. Since recommended drug therapy and prognosis differ, our data underscore the importance of diagnostic testing to assess left ventricular systolic function. Drug therapy for CHF patients provides a major challenge for quality-of-care improvement.

Identification of intraocular lens-adsorbed proteins in mammalian in vitro and in vivo systems

OBJECTIVE

Mammalian in vitro and in vivo systems were used to study the protein-adsorbing potential of intraocular lenses (IOLs).

METHODS

Intraocular lenses composed of polymethyl methacrylate optics with polypropylene haptics were incubated in rabbit plasma for 3 hours (in vitro grouping) or implanted in rabbit eyes for 48 hours (in vivo grouping). Lens-adsorbed proteins from both experimental groupings were eluted with sodium dodecyl sulfate and identified by Western Blot analyses.

RESULTS

The adsorbed protein layer was composed of at least six different proteins: albumin, complement C3 fragments, IgG, fibrinogen/fibrin (as a fibrin clot in vivo), fibronectin, and transferrin. Of the identified components, albumin, IgG, fibronectin, and fibrinogen were the predominant protein species on the in vitro IOLs, while fibronectin and fibrin were on the in vivo IOLs.

CONCLUSIONS

The composition of the protein layer has the potential to alter the biological property of IOLs.

Nicardipine in heart failure: distinguishing its acute beneficial from its chronic effects

Concern over negative inotropic effects has limited the use of calcium blockers in patients with congestive heart failure. Nicardipine, a second generation dihydropyridine calcium channel blocker, has demonstrated positive hemodynamic effects in short-term therapy in patients with congestive heart failure. Prolonged use of calcium channel blockers remains contraindicated in patients with congestive heart failure due to the potential for activation of the renin-angiotensin system. However, acute intravenous nicardipine administration has important clinical applications (as in the management of surgical hypertension or hypertensive emergencies). Nicardipine may be safely used for these indications even in the presence of congestive heart failure.

Dipeptide inhibitors of ubiquitin-mediated protein turnover prevent growth factor-induced neurite outgrowth in rat pheochromocytoma PC12 cells

Dipeptide inhibitors of the ubiquitin-dependent proteolysis pathway governed by N-terminal recognition (N-end rule) in reticulocyte lysates significantly suppress NGF- and bFGF-induced neurite outgrowth in rat pheochromocytoma PC12 cells, but do not cause retraction of already formed neurites. Peptides which do not inhibit proteolysis are also without effect on PC12 cell differentiation. Suppression of neurite outgrowth is readily reversible upon removal of the inhibitors. These data demonstrate a requirement for specific protein turnover in the process of neuron-like differentiation in PC12 cells and provide the first demonstration of a physiological role for the N-end rule.

Anomeric specificity of glucose effect on cAMP, fructose 1,6-bisphosphatase, and trehalase in yeast

The addition of beta-D-glucose (final concentration, 50 mM) to a cell suspension of Saccharomyces cerevisiae in stationary phase caused a rapid 4-fold increase in the concentration of cAMP, while a 2-fold increase of cAMP was observed by the addition of alpha-D-glucose. beta -D-Glucose was also more effective than alpha-D-glucose in the inactivation of fructose 1,6-bisphosphatase and the activation of trehalase. These results, taken together with the previous report that alpha-D-glucose is transported more rapidly than beta-D-glucose in Saccharomyces cerevisiae, do not support the view currently proposed by some investigators that cotransport of D-glucose with protons causes the depolarization of the cell membrane, resulting in the activation of adenylate cyclase. The present data, however, provides supporting evidence for the view that cAMP-dependent protein kinase is implicated in the inactivation of fructose 1,6-bisphosphatase and the activation of trehalase.

An altered adenylate cyclase in cdc35-1 cell division cycle mutant of yeast

Adenylate cyclase activity was studied in Saccharomyces cerevisiae's cell division cycle (cdc) mutant 35-1. The temperature sensitive mutant cdc35-1 was previously mapped as an allele of cyr, the adenylate cyclase gene. However, the adenylate cyclase activities of membranes prepared from cdc35-1 were not thermosensitive. The adenylate cyclase activity of cdc35-1 was found to have an altered Mn2+ dependency and did not respond to Gpp(NH)p stimulation. These results suggest that cdc35-1 mutation may not be at the catalytic site but at a site where adenylate cyclase interacts with regulatory proteins.

Catabolite inactivation of fructose 1,6-bisphosphatase and cytoplasmic malate dehydrogenase in yeast

Catabolite inactivation of fructose 1,6-bisphosphatase and cytoplasmic malate dehydrogenase was studied using the protease-deficient and vacuole-defective yeast strain pep4-3. The catabolite inactivation of fructose 1,6-bisphosphatase in pep4-3 was found to have a normal first inactivation step but with a defective second proteolytic step. In contrast, catabolite inactivation of cytoplasmic malate dehydrogenase was normal in pep4-3. These results suggest that the proteolytic pathways utilized in the hydrolysis of the two enzymes may be different and that proteolysis of fructose 1,6-bisphosphatase may require functional vacuoles while proteolysis of cytoplasmic malate dehydrogenase may not.

Purification and phosphorylation of fructose-1,6-bisphosphatase from Kluyveromyces fragilis

Fructose-1,6-bisphosphatase from the yeast Kluyveromyces fragilis was found to have an apparent Mr = 155,000 and to be composed of four Mr = 35,000 subunits. The extent and rate of phosphorylation of fructose-1,6-bisphosphatase (Fru-1,6-P2) by yeast cAMP-dependent protein kinase were dependent on fructose-1,6-bisphosphatase inhibitors, 5'-AMP and fructose 2,6-bisphosphate (Fru-2,6-P2). In the absence of inhibitor, the enzyme was slowly phosphorylated with a maximum incorporation of 1 mol of phosphate/mol of enzyme. The presence of both inhibitors greatly increased the phosphorylation rate with a maximum incorporation of 2 mol of phosphate/mol of enzyme. The presence of only one inhibitor led to an intermediate rate of phosphorylation with 2 mol of phosphate incorporated/mol of enzyme. There was no significant change in enzymatic activity after phosphorylation. The estimated sedimentation coefficient of fructose-1,6-bisphosphatase was lowered by 5'-AMP from 8.2 to 5.7 while Fru-2,6-P2 increased the S value to 8.5. The presence of either Fru-1,6-P2 or Fru-2,6-P2 prevented the 5'-AMP lowering of S value. The susceptibility of enzyme to partial tryptic digestion was not changed by the presence of 5'-AMP. The presence of both Fru-2,6-P2 and 5'-AMP led to the protection of Mr = 35,000 subunit from tryptic digestion while Fru-2,6-P2 alone led to a protection of an Mr = 30,000 peptide fragment. This peptide fragment did not contain the phosphorylation sites. Our results suggest that the rapid regulation of fructose-1,6-bisphosphatase following glucose addition is controlled mainly by enzyme inhibitors.

Enzymic synthesis and cofactor activity of 3'-pyrophosphocoenzyme A

The 3'-pyrophosphate derivative of CoA was synthesized by using the excreted 5'-to-3' pyrophosphoryl-transferring enzyme from Streptomyces adephospholyticus and ATP as donor and dephospho-CoA as acceptor. Cofactor activity of this new coenzyme A derivative was tested with Clostridium kluyveri phosphotransacetylase and hog heart succinic thiokinase. With the phosphotransacetylase, 3'-pyrophospho-CoA was found to be twice as active as CoA whereas dephospho-CoA was inactive. However, succinic thiokinase utilized all three types of CoA equally well. Adenosine 5'-monophosphate 3'-pyrophosphate also was synthesized and used as an analog of adenosine 5'-monophosphate 3'-monophosphate in the dog liver's sulfotransferase-catalyzed sulfate transfer from p-nitrophenyl sulfate to phenol. In contrast to the pyrophospho derivative of coenzyme A, adenosine 5'-monophosphate 3'-pyrophosphate was inactive as a cofactor.

Guanosine 5'-triphosphate, 3'-diphosphate 5'-phosphohydrolase. Purification and substrate specificity

The regulatory nucleotide guanosine 5'-diphosphate, 3'-diphosphate (ppGpp) and its precursor guanosine 5'-triphosphate, 3'-diphosphate (pppGpp) are accumulated during stringent response in bacterial cells. The enzyme pppGpp-5'-phosphohydrolase, which catalyzes the conversion of pppGpp to ppGpp, was partially purified from Escherichia coli. It has Mr = 140,000 and an apparent Km of 0.11 mM for pppGpp. It requires Mg2+ and a monovalent cation. NH4+ is preferred over K+, while Na+ is inactive. The enzyme does not hydrolyze GTP, ATP, pppApp, or ppGpp. It is also not effectively inhibited by these nucleotides. pppGpp-5'-phosphohydrolase hydrolyzes the 3'-monophosphate analog pppGp equally well (apparent Km of 0.13 mM), yielding the recently identified MS III nucleotide (ppGp). pppGpp-5'-phosphohydrolase does not have RNA 5'-terminal gamma-phosphatase activity; however, 5'-terminal phosphates are released by pppGpp-5'-phosphohydrolase when the GTP-terminated RNA chains are first converted into oligonucleotides by RNase A treatment. pppGpp-5'-phosphohydrolase was found to actively hydrolyze the dinucleotide fragment pppGpNp but exhibited very low activity toward longer chain fragments. The 3'-unphosphorylated dinucleotide pppGpN was, however, not hydrolyzed. The ability of pppGpp-5'-phosphohydrolase to hydrolyze pppGpp, pppGp, and pppGpNp, but not pppG and pppGpN, indicates that pppGpp-5'-phosphohydrolase is rather nonspecific toward the 3'-OH substitutions of the substrates although a free, unsubstituted phosphate group at the 3'-OH position is essential.