The Prion Protein Preference of Sporadic Creutzfeldt-Jakob Disease Subtypes

Sporadic Creutzfeldt-Jakob disease (CJD) is the most prevalent manifestation of the transmissible spongiform encephalopathies or prion diseases affecting humans. The disease encompasses a spectrum of clinical phenotypes that have been correlated with molecular subtypes that are characterized by the molecular mass of the protease-resistant fragment of the disease-related conformation of the prion protein and a polymorphism at codon 129 of the gene encoding the prion protein. A cell-free assay of prion protein misfolding was used to investigate the ability of these sporadic CJD molecular subtypes to propagate using brain-derived sources of the cellular prion protein (PrP^C). This study confirmed the presence of three distinct sporadic CJD molecular subtypes with PrP^C substrate requirements that reflected their codon 129 associations in vivo. However, the ability of a sporadic CJD molecular subtype to use a specific PrP^C substrate was not determined solely by codon 129 as the efficiency of prion propagation was also influenced by the composition of the brain tissue from which the PrP^C substrate was sourced, thus indicating that nuances in PrP^C or additional factors may determine sporadic CJD subtype. The results of this study will aid in the design of diagnostic assays that can detect prion disease across the diversity of sporadic CJD subtypes.     

Familial Creutzfeldt-Jakob Disease: Case report and role of genetic counseling in post mortem testing

Here we present a case of an asymptomatic 53-year-old woman who sought genetic testing for Familial Creutzfeldt-Jakob Disease (fCJD) after learning that her mother had fCJD. The patient's mother had a sudden onset of memory problems and rapidly deteriorating mental faculties in her late 70s, which led to difficulties ambulating, progressive non-fluent aphasia, dysphagia and death within ～1 y of symptom onset. The cause of death was reported as “rapid onset dementia.” The patient's family, unhappy with the vague diagnosis, researched prion disorders online and aggressively pursued causation and submitted frozen brain tissue from the mother to the National Prion Disease Surveillance Center, where testing revealed a previously described 5-octapeptide repeat insertion (5-OPRI) in the prion protein gene (PRNP) that is known to cause fCJD. The family had additional questions about the implications of this result and thus independently sought out genetic counseling.

?While rare, fCJD is likely underdiagnosed due to clinical heterogeneity, rapid onset, early non-specific symptomatology, and overlap in the differential diagnosis of Alzheimer disease and Lewy body dementias. When fCJD is identified, a multidisciplinary approach to return of results that includes the affected patient's provider, genetics professionals, and mental health professionals is key to the care of the family. We present an example case which discusses the psychosocial issues encountered and the role of genetic counseling in presymptomatic testing for incurable neurodegenerative conditions. Ordering physicians should be aware of the basic issues surrounding presymptomatic genetic testing and identify local genetic counseling resources for their patients.     

Synthetic prions generated in vitro are similar to a newly identified subpopulation of PrPSc from sporadic Creutzfeldt-Jakob Disease

In recent studies, the amyloid form of recombinant prion protein (PrP) encompassing residues 89-230 (rPrP 89-230) produced in vitro induced transmissible prion disease in mice. These studies showed that unlike "classical" PrP(Sc) produced in vivo, the amyloid fibrils generated in vitro were more proteinase-K sensitive. Here we demonstrate that the amyloid form contains a proteinase K-resistant core composed only of residues 152/153-230 and 162-230. The PK-resistant fragments of the amyloid form are similar to those observed upon PK digestion of a minor subpopulation of PrP(Sc) recently identified in patients with sporadic Creutzfeldt-Jakob disease (CJD). Remarkably, this core is sufficient for self-propagating activity in vitro and preserves a beta-sheet-rich fibrillar structure. Full-length recombinant PrP 23-230, however, generates two subpopulations of amyloid in vitro: One is similar to the minor subpopulation of PrP(Sc), and the other to classical PrP(Sc). Since no cellular factors or templates were used for generation of the amyloid fibrils in vitro, we speculate that formation of the subpopulation of PrP(Sc) with a short PK-resistant C-terminal region reflects an intrinsic property of PrP rather than the influence of cellular environments and/or cofactors. Our work significantly increases our understanding of the biochemical nature of prion infectious agents and provides a fundamental insight into the mechanisms of prions biogenesis.     

散发性帕金森病蛋白酶体功能障碍及其所致的路易(小)体形成

散发性帕金森病(sporadic Parkinson's disease, sPD)的主要病理特征之一是中脑黑质致密部(substantia nigra pars compacta, SNpc)残存多巴胺能神经元内核周路易(小)体(Lewy body, LB)形成.LB发生的具体原因和确切过程有待进一步阐释.来自遗传学、尸体解剖和实验科学的报道提示,蛋白酶体功能障碍及其所致的LB形成可能是按照聚集体形成途径(process of aggresomes)进行的.在聚集体形成途径过程中,异常蛋白质聚集基本上经历了非纤维化分子聚集过程(molecular crowding)以及后续的纤维化聚集过程(fibrilation of aggregation).其间,蛋白酶体功能障碍(dysfunction of proteasome)、内质网相关降解丧失(loss of endoplasmic reticulum associated degradation)、非纤维化聚集物(nonfibrilar aggregates)、聚集体(aggresomes)及至纤维化LB (fibrilar LB)等构成了sPD病变过程的主要事件.这提示在sPD病变过程中,蛋白酶体功能障碍及其所致的LB形成过程实质上是细胞信号的转导过程,其间涉及了众多的蛋白质分子.     

An autopsy-verified case of FTLD-TDP type A with upper motor neuron-predominant motor neuron disease mimicking MM2-thalamic-type sporadic Creutzfeldt-Jakob disease

Here we report an autopsy-verified case of frontotemporal lobar degeneration (FTLD)-transactivation responsive region (TAR) DNA binding protein (TDP) type A with upper motor neuron-predominant motor neuron disease mimicking MM2-thalamic-type sporadic Creutzfeldt-Jakob disease (sCJD). A 69-year-old woman presented with an 11-month history of progressive dementia, irritability, insomnia, and gait disturbance without a family history of dementia or prion disease. Neurological examination revealed severe dementia, frontal signs, and exaggerated bilateral tendon reflexes. Periodic sharp-wave complexes were not observed on the electroencephalogram. Brain diffusion MRI did not reveal abnormal changes. An easy Z score (eZIS) analysis for ^99mTc-ECD-single photon emission computed tomography (^99mTc-ECD-SPECT) revealed a bilateral decrease in thalamic regional cerebral blood flow (rCBF). PRNP gene analysis demonstrated methionine homozygosity at codon 129 without mutation. Cerebrospinal fluid (CSF) analysis showed normal levels of both 14-3-3 and total tau proteins. Conversely, prion protein was slowly amplified in the CSF by a real-time quaking-induced conversion assay. Her symptoms deteriorated to a state of akinetic mutism, and she died of sudden cardiac arrest, one year after symptom onset.

?Despite the SPECT results supporting a clinical diagnosis of MM2-thalamic-type sCJD, a postmortem assessment revealed that this was a case of FTLD-TDP type A, and excluded prion disease. Thus, this case indicates that whereas a bilateral decreasing thalamic rCBF detected by ^99mTc-ECD-SPECT can be useful for diagnosing MM2-thalamic-type sCJD, it is not sufficiently specific. Postmortem diagnosis remains the gold standard for the diagnosis of this condition.     

Role of Ribonuclease and Ribonuclease Inhibitor Activities in Alzheimer''s Disease

It has been suggested that defects in the relationship between ribonuclease and its proteinaceous inhibitor could be a contributory factor in Alzheimer's disease. We have investigated this possibility further by analysing free and bound enzyme activities and the activity of the inhibitor in nine regions of diseased and normal brain. These were chosen to include areas known to be affected by the disease, regions not histologically affected but thought to be involved in the disease process, and areas not thought to be involved in the disease. Neither the enzyme nor its inhibitor is defective in its activities in the chosen areas of Alzheimer's disease brain when compared with those of carefully age-matched controls.     

FDG-PET in Creutzfeldt-Jakob disease: Analysis of clinical-PET correlation

Objective: To assess the relationship between clinical pattern and cerebral glucose metabolism on [18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in Creutzfeldt-Jakob disease (CJD). Methods: Predefined clinical signs (ataxia, visual, pyramidal, myoclonus, limb apraxia, limb dystonia, sensory, parkinsonism, and corticobasal syndrome [CBS]) and FDG-PET data were assessed in consecutive CJD patients. Two types of statistical parametric mapping (SPM) analyses, using stringent level of significance p < 0.001 and extent threshold of 100 voxels, were performed: one comparing CJD patients presenting specific sign against CJD patients without this specific sign (inter-CJD analysis), and one comparing CJD patients with specific sign against 18 healthy controls (CJD-control analysis). Results: Fifteen CJD patients (11 probable and two histologically proven sporadic and two genetic CJD) were analyzed. CJD-control analysis of the entire CJD group showed lateralized frontal and parietal hypometabolism. When analyzing clinical CJD subgroups, inter-CJD analyses showed hypometabolism in more restricted areas than on CJD-control analyses. For CJD patients presenting with ataxia, visual signs and CBS (and CBS-associated signs), additional hypometabolic areas probably related to the specific signs were identified: pons and middle cerebellar peduncles in patients with ataxia; occipital cortex in patients with visual signs; and prerolandic and lateral parietal cortex in patients with CBS. For pyramidal signs, sensory loss, and parkinsonism, no abnormalities in brain areas typically involved in these signs were observed. Conclusion: In addition to lateralized frontal and parietal hypometabolism previously reported in CJD and observed here, hypometabolism in brain areas related to some specific signs (i.e. ataxia, visual signs, and CBS) is also seen.     

Characteristics of Korean patients with suspected Creutzfeldt-Jakob disease with 14-3-3 protein in cerebrospinal fluid: Preliminary study of the Korean Creutzfeldt-Jakob disease active surveillance program

Although Korea had a national surveillance system for Creutzfeldt-Jakob disease (CJD), it was mainly dependent on attending physician''s reports. Thus, little prospective data about the epidemiology, characteristics, and final diagnoses of suspected patients were available. We have established a nationwide network for the active surveillance of patients with suspected CJD. When the requested cerebrospinal fluid (CSF) samples tested positive for 14-3-3 protein, we investigated the clinical characteristics of the corresponding patients and followed them until their final diagnoses were confirmed. A total of 218 samples were requested for CSF assays from May 2010 to August 2012, and 106 (48.6%) were positive for 14-3-3 protein. In 89 patients with complete clinical data, 38 (42.7%) were diagnosed with probable CJD and the estimated annual occurrence of CJD was 16.3 persons-per-year. The most common diagnoses of the remainder were central nervous system infection and any-cause encephalopathy. Non-CJD subjects showed worse initial consciousness levels than CJD patients. This preliminary study showed that the number of reported cases of CJD and the true positivity rates of CSF 14-3-3 protein assays were both low in Korea. An active surveillance system is urgently needed to provide the latest nationwide epidemiological data of CJD.     

14-3-3 Protein, Total Tau and Phosphorylated Tau in Cerebrospinal Fluid of Patients with Creutzfeldt-Jakob Disease and Neurodegenerative Disease in Japan

1.Sporadic Creutzfeldt-Jakob disease (CJD) is a rapidly progressive and fatal disease. Patients with CJD usually become akinetic mutism within approximately 6 months. In addition, clinical signs and symptoms at early stage of sporadic CJD may not be easy to distinguish from other neurodegenerative diseases by neurological findings. However, diagnostic biochemical parameters including 14-3-3 protein, S100, neuron-specific enorase in cerebrospinal fluid (CSF) have been used as diagnostic markers, elevated titers of these markers can also be observed in CSF in other neurodegenerative diseases. Therefore, we examined other biochemical markers to discriminate CJD from other neurodegenerative diseases in CSF. 2.We analyzed CSF samples derived from 100 patients with various neurodegenerative disorders by Western blot of 14-3-3 protein, quantification of total tau (t-tau) protein, and phosphorylated tau (p-tau) protein. All patients with CJD in this study showed positive 14-3-3 protein and elevated t-tau protein (>1000 pg/mL) in CSF. We also detected positive 14-3-3 protein bands in two patients in non-CJD group (patients with dementia of Alzheimer's type; DAT) and also detected elevated t-tau protein in three patients in non-CJD group. Elevated t-tau protein levels were observed in two patients with DAT and in one patient with cerevrovascular disease in acute phase. 3.To distinguish patients with CJD from non-CJD patients with elevated t-tau protein in CSF, we compared the ratio of p-tau and t-tau proteins. The p-/t-tau ratio was dramatically and significantly higher in DAT patients rather than in CJD patients. 4.Therefore, we concluded that the assay of t-tau protein may be useful as 1st screening and the ratio of p-tau protein/t-tau protein would be useful as 2nd screening to discriminate CJD from other neurodegenerative diseases.     

Characteristics of Korean patients with suspected Creutzfeldt-Jakob disease with 14-3-3 protein in cerebrospinal fluid: Preliminary study of the Korean Creutzfeldt-Jakob disease active surveillance program

Abstract

Although Korea had a national surveillance system for Creutzfeldt-Jakob disease (CJD), it was mainly dependent on attending physician's reports. Thus, little prospective data about the epidemiology, characteristics, and final diagnoses of suspected patients were available. We have established a nationwide network for the active surveillance of patients with suspected CJD. When the requested cerebrospinal fluid (CSF) samples tested positive for 14-3-3 protein, we investigated the clinical characteristics of the corresponding patients and followed them until their final diagnoses were confirmed. A total of 218 samples were requested for CSF assays from May 2010 to August 2012, and 106 (48.6%) were positive for 14-3-3 protein. In 89 patients with complete clinical data, 38 (42.7%) were diagnosed with probable CJD and the estimated annual occurrence of CJD was 16.3 persons-per-year. The most common diagnoses of the remainder were central nervous system infection and any-cause encephalopathy. Non-CJD subjects showed worse initial consciousness levels than CJD patients. This preliminary study showed that the number of reported cases of CJD and the true positivity rates of CSF 14-3-3 protein assays were both low in Korea. An active surveillance system is urgently needed to provide the latest nationwide epidemiological data of CJD.     

Combined findings of FDG-PET and arterial spin labeling in sporadic Creutzfeldt-Jakob disease

ABSTRACT

Sporadic Creutzfeldt-Jakob disease (sCJD) is a fatal progressive neurodegenerative disease. Multimodal approaches, including electroencephalogram, diffusion-weighted imaging (DWI) of brain MRI, and cerebrospinal fluid biomarkers, have been applied to increase the diagnostic accuracy of sCJD. Although previous studies suggested DWI could be the most useful modality for sCJD diagnosis, whether metabolism changes underlying in sCJD are still poorly understood. To the best of our knowledge, there are only one case using the technique of arterial spin labeling (ASL) to detection and follow-up of perfusion changes in CJD. Herein, we described a 71-year-old woman presented with progressive cognitive decline, behavioral and psychological symptoms for two months. The patient died one month later after her admission. As far as we know, this is the first report using the combination of fluorodeoxyglucose positron emission tomography and ASL to explore the metabolism changes in sCJD. Our case exemplifies the difficulty clinicians may face in the diagnosis of sCJD.     

First case of V180I rare mutation in a Brazilian patient with Creutzfeldt-Jakob disease

Here, we report the first case of V180I rare mutation in a Brazilian woman whose clinical condition started with memory impairment for recent events and insomnia with 2 months of evolution, without any other alterations in neurological examination. Both the electroencephalogram (EEG) and the routine biochemical examination of cerebrospinal fluid (CSF) were normal. CSF 14-3-3 protein search was positive. Magnetic resonance imaging (MRI) of the encephalon showed findings suggestive of Creutzfeldt-Jakob disease, confirmed by sequencing of PRNP gene that reveal V180I mutation also homozygosity for methionine at codon 129 (M129M).     

Defective Self-Renewal and Differentiation of GBA-Deficient Neural Stem Cells Can Be Restored By Macrophage Colony-Stimulating Factor

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder caused by mutations in the glucocerebrosidase gene (GBA), which encodes the lysosomal enzyme glucosylceramidase (GCase). Deficiency in GCase leads to characteristic visceral pathology and lethal neurological manifestations in some patients. Investigations into neurogenesis have suggested that neurodegenerative disorders, such as GD, could be overcome or at least ameliorated by the generation of new neurons. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are potential candidates for use in the treatment of neurodegenerative disorders because of their ability to promote neurogenesis. Our objective was to examine the mechanism of neurogenesis by BM-MSCs in GD. We found that neural stem cells (NSCs) derived from a neuronopathic GD model exhibited decreased ability for self-renewal and neuronal differentiation. Co-culture of GBA-deficient NSCs with BM-MSCs resulted in an enhanced capacity for self-renewal, and an increased ability for differentiation into neurons or oligodendrocytes. Enhanced proliferation and neuronal differentiation of GBA-deficient NSCs was associated with elevated release of macrophage colony-stimulating factor (M-CSF) from BM-MSCs. Our findings suggest that soluble M-CSF derived from BM-MSCs can modulate GBA-deficient NSCs, resulting in their improved proliferation and neuronal differentiation.     

Isoform pattern of 14-3-3 proteins in the cerebrospinal fluid of patients with Creutzfeldt-Jakob disease

Two-dimensional polyacrylamide gel electrophoresis of CSF has been used in the diagnosis of Creutzfeldt-Jakob disease (CJD). One of the two diagnostic protein spots was identified as isoform(s) of the 14-3-3 family of abundant brain proteins. This has led to the development of one-dimensional 14-3-3 sodium dodecyl sulfate polyacrylamide gel electrophoresis immunoblot, which is currently used to support the diagnosis of CJD. In the present study employing western blot analysis, we have identified the panel of 14-3-3 isoforms that appear in the CSF of 10 patients with CJD compared with 10 patients with other dementias. The results clearly show that the 14-3-3 isoforms beta, gamma, epsilon, and eta are present in the CSF of patients with CJD and can be used to differentiate other dementias. 14-3-3eta also gave a baseline signal in all patients with other dementias, including six patients with Alzheimer's disease. The presence of 14-3-3eta in the CSF of a patient with herpes simplex encephalitis was particularly noteworthy. This study has determined that isoform-specific 14-3-3 antibodies against beta, gamma, and epsilon should be considered for the neurochemical differentiation of CJD from other neurodegenerative diseases.     

质子泵抑制剂对冠心病患者嗜铬粒蛋白A影响的临床意义

目的：本研究旨在探讨质子泵抑制剂（vii）对心内科拟诊断为冠心病患者的嗜铬粒蛋白A（CgA）水平影响的临床意义。方法：113名拟诊冠心病的住院患者,分为PPI组（药物治疗中加入PPI,共62例）和非PPI组（药物治疗中无PPI,共51例）,收集其外周血清,用ELISA法检测样本血清中CgA水平,同时应用化学发光法检测样本血清中NT—proBNP水平。比较PPI组和非PPI组CgA、NT．proBNP水平的差异。结果：因为CgA、NT．proBNP均为非正态分布资料,两者均通过对数转换为正态分布资料;PPI组的LNCgA的均数显著高于非PPI组（4．62±0．97和3．91±0．89,P=0．000）。而两组LNNT-proBNP的均数无显著差异（5．41±1．46和5．59±2．00,P=0．580）。结论：在心功能等临床特征具有可比性的情况下,是否使用PPI对CgA水平的影响很大;而对BNP无明显影响。评价CgA在心功能分级或冠心病预后等方面的应用,不能忽略PPI联用对CgA数值的影响。     

Molecular pathogenesis of sporadic prion diseases in man

The yeast, fungal and mammalian prions determine heritable and infectious traits that are encoded in alternative conformations of proteins. They cause lethal sporadic, familial and infectious neurodegenerative conditions in man, including Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), kuru, sporadic fatal insomnia (SFI) and likely variable protease-sensitive prionopathy (VPSPr). The most prevalent of human prion diseases is sporadic (s)CJD. Recent advances in amplification and detection of prions led to considerable optimism that early and possibly preclinical diagnosis and therapy might become a reality. Although several drugs have already been tested in small numbers of sCJD patients, there is no clear evidence of any agent’s efficacy. Therefore, it remains crucial to determine the full spectrum of sCJD prion strains and the conformational features in the pathogenic human prion protein governing replication of sCJD prions. Research in this direction is essential for the rational development of diagnostic as well as therapeutic strategies. Moreover, there is growing recognition that fundamental processes involved in human prion propagation – intercellular induction of protein misfolding and seeded aggregation of misfolded host proteins – are of far wider significance. This insight leads to new avenues of research in the ever-widening spectrum of age-related human neurodegenerative diseases that are caused by protein misfolding and that pose a major challenge for healthcare.     

Molecular pathogenesis of sporadic prion diseases in man

The yeast, fungal and mammalian prions determine heritable and infectious traits that are encoded in alternative conformations of proteins. They cause lethal sporadic, familial and infectious neurodegenerative conditions in man, including Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), kuru, sporadic fatal insomnia (SFI) and likely variable protease-sensitive prionopathy (VPSPr). The most prevalent of human prion diseases is sporadic (s)CJD. Recent advances in amplification and detection of prions led to considerable optimism that early and possibly preclinical diagnosis and therapy might become a reality. Although several drugs have already been tested in small numbers of sCJD patients, there is no clear evidence of any agent’s efficacy. Therefore, it remains crucial to determine the full spectrum of sCJD prion strains and the conformational features in the pathogenic human prion protein governing replication of sCJD prions. Research in this direction is essential for the rational development of diagnostic as well as therapeutic strategies. Moreover, there is growing recognition that fundamental processes involved in human prion propagation – intercellular induction of protein misfolding and seeded aggregation of misfolded host proteins – are of far wider significance. This insight leads to new avenues of research in the ever-widening spectrum of age-related human neurodegenerative diseases that are caused by protein misfolding and that pose a major challenge for healthcare.     

质子泵抑制剂对冠心病患者嗜铬粒蛋白A 影响的临床意义

目的:本研究旨在探讨质子泵抑制剂(PPI)对心内科拟诊断为冠心病患者的嗜铬粒蛋白A(CgA)水平影响的临床意义。方法:113名拟诊冠心病的住院患者,分为PPI组(药物治疗中加入PPI,共62例)和非PPI组(药物治疗中无PPI,共51例),收集其外周血清,用ELISA法检测样本血清中CgA水平,同时应用化学发光法检测样本血清中NT-proBNP水平。比较PPI组和非PPI组CgA、NT-proBNP水平的差异。结果:因为CgA、NT-proBNP均为非正态分布资料,两者均通过对数转换为正态分布资料;PPI组的LN CgA的均数显著高于非PPI组(4.62±0.97和3.91±0.89,P=0.000)。而两组LN NT-proBNP的均数无显著差异(5.41±1.46和5.59±2.00,P=0.580)。结论:在心功能等临床特征具有可比性的情况下,是否使用PPI对CgA水平的影响很大;而对BNP无明显影响。评价CgA在心功能分级或冠心病预后等方面的应用,不能忽略PPI联用对CgA数值的影响。     

Tumor Volume Can Be Used as a Parameter Indicating the Severity of Disease in Parathyroid Cancer

ObjectiveTo determine whether tumor volume and tumor size are related to disease severity in parathyroid cancer (PC).MethodsPatients treated for PC at our institution were retrospectively identified. Data were collected about clinical and pathologic characteristics, laboratory parameters, tumor volume, recurrence, metastasis, and mortality. Correlation analysis was applied to laboratory parameters, tumor volume, and tumor size in PC patients.ResultsThe study included 20 patients diagnosed with PC at our center. The median follow-up was 33 months. Serum calcium (median, 12.5 mg/dL), serum parathormone (PTH) (median, 743 pg/mL), and serum alkaline phosphatase (ALP) (median, 298 U/L) levels were found to be increased, and 25-hydroxyvitamin D (25[0H)D) (median, 12.3 ng/mL) and serum phosphorus (median, 2.1 mg/dL) levels were decreased. Magnesium level was within normal limits (median, 1.9 mg/dL). The median tumor volume was 5.7 mL and median tumor size was 2.5 cm. Significant positive correlations were found between tumor volume and calcium, ALP, and PTH levels. A significant negative correlation was found between tumor volume and 25(OH)D level. There were no significant correlations between tumor size and calcium, ALP, PTH, and 25(OH)D.ConclusionThese results found that the tumor volume affected PTH, calcium, ALP, and 25(OH)D levels. The morbidity and mortality associated with PC were usually associated with PTH secretion and hypercalcemia. Therefore, tumor volume may be a more effective parameter than tumor size when evaluating the severity of disease.