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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 41  |  Issue : 2  |  Page : 77-80

Neuron-specific enolase in cerebrospinal fluid as a neurochemical marker for brain damage in acute lymphoblastic leukemia


1 Department of Pediatrics, Faculty of Medicine, Zagazig University, Zagazig, Egypt
2 Department of Clinical Pathology, Faculty of Medicine, Zagazig University, Zagazig, Egypt

Date of Submission02-Dec-2015
Date of Acceptance07-Dec-2015
Date of Web Publication15-Jul-2016

Correspondence Address:
Hossam E Salah
Department of Clinical Pathology, Faculty of Medicine, Zagazig University, Zagazig, 44519
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-1067.186410

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  Abstract 

Background Acute lymphoblastic leukemia (ALL) is the most common form of childhood cancer with a cure rate approaching 80%. Neuron-specific enolase (NSE) is known to be a cell-specific isoenzyme of the glycolytic enzyme enolase. The expression of NSE is a late event in neural differentiation, thus making it a useful index of neural maturation. It is a highly specific marker for neurons and peripheral neuroendocrine cells. NSE in cerebrospinal fluid (CSF) is a reliable marker of neuronal damage. It is believed to signal for brain damage after hypoxic-ischemic and traumatic injury.
Objective and methods This study aimed to measure CSF levels of NSE as a neurochemical marker for brain damage in response to chemotherapy at diagnosis and during induction using the enzyme-linked immunosorbent assay method. Thirty newly diagnosed ALL patients were enrolled in this study, comprising 19 male and 11 female patients.
Results NSE level in the CSF samples increased from 9.3 ± 2.1 μg/l on day 0 (before the start of treatment) to 14.9 ± 1.85 μg/l on day 7 and then gradually decreased to 11.4 ± 1.46 μg/l on day 28. The increase in NSE levels in CSF on days 7 and 28 was considered highly significant when compared with those measured on day 0 (before induction therapy).
Conclusion We concluded that the increase in NSE in CSF during induction therapy in children with ALL can be interpreted as an early sign of brain damage.

Keywords: acute lymphoblastic leukemia, brain damage, chemotherapy, neuron-specific enolase


How to cite this article:
Sherief LM, Beshir M, Salah HE. Neuron-specific enolase in cerebrospinal fluid as a neurochemical marker for brain damage in acute lymphoblastic leukemia. Egypt J Haematol 2016;41:77-80

How to cite this URL:
Sherief LM, Beshir M, Salah HE. Neuron-specific enolase in cerebrospinal fluid as a neurochemical marker for brain damage in acute lymphoblastic leukemia. Egypt J Haematol [serial online] 2016 [cited 2019 Dec 14];41:77-80. Available from: http://www.ehj.eg.net/text.asp?2016/41/2/77/186410


  Introduction Top


Acute lymphoblastic leukemia (ALL) is the most common form of childhood cancer, with cure rate approaching 80%. To achieve this good outcome, prophylactic treatment of the central nervous system (CNS) in addition to systemic chemotherapy is essential [1].

Formal treatment protocols using cranial irradiation as prophylaxis have shown lower intelligence scores and specific neuropsychological deficits after treatment in the patient group compared with the control group [2].

Irradiation was substituted with repeated intrathecal methotrexate injections and high-dose intravenous methotrexate [3]. However, this approach has also been suspected of carrying the risk for adverse effects and severe acute neurological symptoms have been reported [4].

Neuron-specific enolase (NSE) is known to be a cell-specific isoenzyme of the glycolytic enzyme enolase. The expression of NSE, which occurs as γγ-dimer and αγ-dimer, is a late event in neural differentiation, thus making it a useful index of neural maturation. NSE is a highly specific marker for neurons and peripheral neuroendocrine cells [5].

NSE is predominantly present in the neuronal soma, but it is also present to a lesser degree in the axons. It can also be found in neuroendocrine cells and to some extent in oligodendrocytes. Extracellular presence of NSE is attributed to cell destruction [6]. Outside the CNS, it is also found in non-neuronal tissues and is sometimes used as a tumor marker. Other enolase isoenzymes are present in red blood cells and platelets and can cross-react with the antibodies. Therefore, hemolysis will cause elevated levels of these isoenzymes in blood [7]. NSE in cerebrospinal fluid (CSF) is a reliable marker of neuronal damage. It is believed to signal for brain damage after hypoxic-ischemic and traumatic injury. It had also been analyzed in various neurodegenerative, inflammatory, and infectious diseases, both in blood and in CSF [8]. To be able to detect elevated levels in blood, there must be severe damage to the CNS. This is not likely to occur during ALL treatment. In CNS, it is possible to detect less pronounced effects on neurons and astrocytes, resulting in leakage of brain-specific proteins [9].

During induction treatment, uneven regional cerebral blood flow with hypoperfusion of cortical areas was reported. This was seen together with leakage of NSE into the CSF. Regional hypoperfusion, causing oxidative stress or direct toxic effect of the chemotherapy, might cause brain damage [4].

The aim of this study was to measure CSF levels of NSE as a neurochemical marker for brain damage in response to chemotherapy at diagnosis and during induction in children with ALL.


  Patients and methods Top


The present study was carried out in the Hematological Oncology Unit of Department of Pediatrics in Zagazig University Hospitals. It included 30 newly diagnosed ALL patients, comprising 19 male and 11 female patients.

All cases of the study were subjected to the following:

  1. Full laboratory examination: complete blood picture with examination of Leishman-stained films, liver and kidney function tests, serum lactate dehydrogenase, serum electrolytes, and CSF examination.
  2. Bone marrow aspiration with examination of Leishman-stained and peroxidase-stained films and immunophenotyping.
  3. Other investigations to detect extramedullary infiltration: plain radiography, abdominal sonar, and brain MRI.


Cerebrospinal fluid sampling

Lumbar punctures were performed under complete aseptic conditions according to the CCG protocol before the start of therapy (day 0), and then on days 7 and 28 during induction treatment. A volume of 2 ml of CSF was sampled (before intrathecal injection), chilled, divided into separate tubes, and immediately frozen and stored at −70°C until analyzed.

Methods

NSE level in the CSF was estimated using CanAg NSE EIA (catalog number: 420-10; CanAg Diagnostics Co. Ltd, Sweden, Beijing, China) according to the manufacturer's instruction manual. Intra-assay and interassay coefficients of variation were 1.7-3.5 and 3.7-5.5%, respectively. Detection limit was less than 1 μg/l. Healthy individuals are expected to have NSE values below 13 μg/l.

Statistical analysis

The results were computed on IBM Personal Computer microprocessor using a statistical software package Epi-Info, version 6.02 (Atlanta, GA, USA).

Quantitative data were presented as mean ± SD and compared using the t-test. Qualitative data were presented in the form of number (frequency) and percentage and were compared using the χ2 or Fischer's exact test. A P value of 0.05 or less was considered as significant, a P value of 0.001 or less as highly significant, and a P value greater than 0.05 as not significant.


  Results Top


[Table 1] shows that Pallor is the most common presentation among our patients (90%). This is followed by fever (74%), hepatosplenomegaly (73.3%), bone ache (73.3%), and lymphadenopathy (70%). CNS manifestations did not appear in any of the patients. [Table 2] shows that anemia is a common laboratory finding among our patients, as mean hemoglobin level at presentation was 8.1 g/dl, and reduced mean of platelet count was 40.4 × 10 3 . [Table 3] shows that according to immunophenotyping, c-ALL is the most common type of ALL in the investigated patients. [Table 4] shows that the increase in NSE levels in CSF on days 7 and 28 is considered highly significant when compared with those measured on day 0 (before induction therapy).
Table 1 Demographic and clinical data of the investigated group


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Table 2 Laboratory parameters of the investigated group


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Table 3 Immunophenotype of the investigated group


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Table 4 NSE levels in CSF


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  Discussion Top


ALL is the most common malignancy in childhood. The advances in diagnostic and therapeutic methods have led to increase in the 5-year survival of childhood ALL patients to more than 80% and about two-thirds of patients reached adulthood [10].

CNS-directed therapy is an essential part of therapy for ALL in children. Because the blood-brain barrier serves as a pharmacological barrier, leukemic cells can remain in CNS despite systemic therapy. It is thought that CNS infiltration is mostly subclinical in the majority of cases. Without preventive therapy directed to the CNS, up to 80% of children with ALL develop CNS infiltration [11].

Although these treatments save lives, they impair activities of the brain, such as thinking, attention, memory, speech, and flexible thought [12].

Many substances are released into the CSF and blood during brain damage, but the ideal damage marker should satisfy certain requirements: to be localized intracellulary, to be present in high concentration in the brain tissues, and finally to be relatively easy for detection. NSE is mentioned as a possible reliable marker for neuronal tissue damage. It is an intracellular protein predominantly present in neuron cytoplasm and in neuroendocrine cells in an insignificant concentration [13]. This enzyme is a highly soluble protein that is easily released in the CSF and blood after tissue injury. Its biological half-life is 48 h [14]. NSE constitutes about 1.5% of the total mass in the brain. The role of NSE in the CNS is not yet completely understood, but some experimental studies pointed to its neuropredictive role. It has been reported that, during CNS development, NSE takes part in forming membrane structures and is involved in all energy-dependent cell processes [15]. NSE is also necessary for maintenance of excitability of neuronal membrane [14].

As NSE is an integral part of the cytoplasm and dendrite of neurons, in physiological conditions, it is detected in small concentrations in CSF and plasma. Immunohistochemical studies showed that, in brain ischemia, functional damage or structural deficit of the cell membrane is followed by easy release of NSE from damaged neurons into the extracellular space [16].

The current study included 30 children who were newly diagnosed as suffering from ALL treated and followed up in the Hematological Oncology Unit of Pediatric Department in Zagazig University Hospitals.

We found that NSE level in the CSF samples increased from 9.3 ± 2.1 μg/l before start of treatment to 14.9 ± 1.85 μg/l on day 7 and then gradually decreased to 11.4 ± 1.46 μg/l on day 28. This change in NSE values is highly significant from days 0 to 7 (P < 0.001) and from days 0 to 28 (P < 0.001). Similar results were reported by Osterlundh and colleagues [4],[17]. They found that NSE levels reached their highest values on day 8 and then remained at higher levels (compared with day 0), but gradually decreased on days 15 and 29. They found that the results of two patients with CNS infiltration did not exceed the mean level of the patients without CNS disease, indicating that lymphoblasts in the CSF do not cause elevated brain-specific proteins. They reported uneven regional cerebral blood flow with hypoperfusion of cerebral areas during induction treatment in patients without neurological symptoms [4],[17]. The level of NSE is a reliable marker for brain damage during brain ischemia. NSE has been analyzed in various neurodegenerative, inflammatory, and infectious disease, both in blood and in CSF [8]. To be able to detect elevated levels in blood, there must be a severe damage to the CNS. This is not likely to occur during ALL treatment. In CNS, it is possible to detect less pronounced effects on neurons and astrocytes, resulting in leakage of brain-specific proteins [9]. However, Liang et al. [18] found that NSE was 11.56 ± 4.52 μg/l in five patients with CNS leukemia and 9.59 ± 3.42 μg/l in 33 cases of acute leukemia, and the difference was not statistically significant. They also found that there was no significant change in NSE levels between day 0 (9.96 ± 3.37 μg/l) before induction treatment, day 10 (11.15 ± 3.49 μg/l), day 20 (12.32 ± 3.55 μg/l), and day 56 (10.76 ± 2.76 μg/l) after intrathecal injection. They concluded that intrathecal administration of methotrexate, arabinoside, and dexamethasone was safe and effective, as they caused no CNS harm. In contrast, Osterlundh et al. [4] studied CSF of 54 children with ALL. They found that the highest levels of NSE were noted in the second sample of the first week of treatment. The increase was not as high as that of asphyxiated newborns, but it was significant and above the level of the control group.

Sioka and Kyristis [19] reported that the most common chemotherapeutic agents that may cause CNS toxicity, manifested as encephalopathy of various severities, include methotrexate, vincristine, ifosfamide, cyclosporine, fludarabine, cytarabine, 5-fluorouracil, cisplatin, and the interferons (α >β). Methotrexate is well known for producing symptoms of neurotoxicity, both acute and delayed. At present, methotrexate administration intrathecally appears to be the most likely noxious agent for these patients [20].

By analyzing our results of NSE values in CSF, we are able to show injury to CNS during ALL induction treatment. However, there are no signs of severe damage and no results that support the association that an active inflammatory process was started by this treatment. It is difficult to define which of the four drugs used during induction is implicated in the CNS process. The dose of dexamethasone is constant during the period of the study and might decrease inflammatory reactions. Dexamethasone has not previously been associated with neurotoxicity.

We could conclude that increased NSE in CSF during induction therapy in children with ALL can be interpreted as an early sign of brain damage, but further studies for following up NSE levels after cessation of treatment are recommended.

Acknowledgements

The manuscript has been read and approved by all authors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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