Chronic lymphocytic leukemia with clinical debut as neurological involvement: a rare phenomenon and the need for better predictive markers
© The Author(s). 2017
Received: 17 August 2015
Accepted: 24 January 2017
Published: 2 February 2017
Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries. The frequency of symptomatic central nervous system (CNS) involvement is unknown but thought to be a rare phenomenon. Currently there are no known risk factors for CNS involvement.
We describe a clinically staged low-risk CLL case that presented with symptomatic CNS involvement and progressed rapidly to death. Evaluation of the surface adhesion molecules identified a markedly altered expression pattern of the integrin, CD49d, and the tetraspanin, CD82, in the index case when compared to similar low-risk CLL cases. We found that the early Rai clinical stage CLL patients showed linear correlation for the co-expression of CD82 and CD49d. In contrast, this unique index case with CNS involvement, which has the same Rai clinical stage, had a significantly lower expression of CD82 and higher expression of CD49d.
These data suggest that the expression profile of CD49d and CD82 may represent potential biomarkers for patients with increased propensity of CNS involvement. Moreover, this study illustrates the critical need for a better mechanistic understanding of how specific adhesion proteins regulate the interactions between CLL cells and various tissue sites.
KeywordsLeukemia Central nervous system CD49d CD82
Chronic lymphocytic leukemia (CLL) is the most common hematologic malignancy in Western countries. The hallmark of CLL is the progressive accumulation of CD5+ B cells in the blood peripheral lymphoid organs, and bone marrow . In rare cases CLL can involve the central nervous system (CNS). Recent systematic analysis data from reported cases in the literature and a large case series of over 4000 patients followed at a single institution have estimated a prevalence of symptomatic CNS involvement in 0.4% of patients with CLL, those findings are consistent with other previously reported antemortem studies [2–4]. In contrast, postmortem studies have demonstrated CNS involvement in up to 71% of patients with CLL . Together, these data imply that CLL infiltration of the CNS is either underdiagnosed or frequently fails to manifest clinically. However, for CLL patients with symptomatic CNS involvement, the average time from diagnosis to death is 12 months .
In general, CLL follows an extremely variable clinical course with patient survival ranging from months to decades . Several pathological markers exist for CLL diagnosis and prognosis, such as CD38 expression, immunoglobulin heavy chain variable region mutation status, and FISH panels for specific genetic alterations . However, thus far, studies have failed to identify risk factors that effectively assist in early identification of CNS involvement . There has been no strong correlation with age, sex, presenting symptoms, Rai stage, duration of disease, immunophenotype, or peripheral white blood cell (WBC) counts . Initial studies reported that CNS infiltration occurs more frequently in late stage CLL [7, 8]. However, a more recent review of the literature indicates that one fourth of all the published cases of CNS involvement were during Rai stage 0 of CLL . In fact recent data suggests that earlier CLL stages are more likely to present with neurological symptoms as the first signs of CLL, which is consistent with the case we present in this study. While 48.8% of patients with Rai stage 0-II disease presented with neurologic symptoms, only 10.7% of patients with stages III-IV disease presented with signs of neurologic involvement . Therefore, the timely diagnosis of CNS involvement and the identification of risk factors for patients who develop CNS infiltration are crucial.
In combination, these data highlight the need for biomarkers that can predict CNS involvement. Soluble CD27 was a marker deemed useful at ruling out disease with a negative predictive value of 92%; however it was ultimately found to be highly non-specific with a positive predictive value of 54% . As such there remains a critical need to identify specific markers that can be used to predict CNS involvement of CLL. We describe here a case that based on all clinical criteria, was staged as a low-risk CLL. Despite all of the low risk prognostic data, the patient presented with CNS involvement and progressed rapidly. Evaluation of the surface adhesion molecules on these CLL cells identified a unique differential expression pattern of the integrin, CD49d, and tetraspanin, CD82. Thus, analysis of the combined expression of CD49d and CD82 may serve as a potential indicator of CLL cells with propensity to involve the CNS.
We studied this case, nested in a pilot institutional project, evaluating the expression profile of specific adhesion molecules that regulate critical interactions between CLL cells and the microenvironment. Integrins, a family of cell adhesion molecules, play a significant role in cell motility, invasion and cell adhesion to the extracellular matrix and supportive stromal cells. In the case of CLL, the integrin CD49d or α4β1, has been linked to migration of CLL cells across the vascular endothelium and found to have clinical relevance for disease prognosis . A recent study confirmed that patients with high CD49d expression had significantly increased CLL infiltration of the bone marrow . Furthermore, a multicenter analysis demonstrated that patients with CLL expressing CD49d in ≥ 30% of neoplastic cells had a diminished 5 and 10-year overall survival and treatment free survival . These findings were independent of CD38 and ZAP-70 expression. Finally, within a large-scale, worldwide, multicenter analysis, CD49d emerged as the strongest flow cytometry-based predictor of overall survival and treatment-free survival .
Interestingly, previous microscopy studies identified CD49d cellular localization within a protein complex enriched on the plasma membrane of CLL cells . Recent work from our group established that CD49d protein organization and membrane density is regulated by the tetraspanin scaffold protein, CD82, which significantly impacts cell adhesion abilities . Tetraspanins facilitate the formation of membrane protein complexes involved in multiple signaling pathways, tumor adhesion and dissemination . CD82 is the protein product of the metastasis suppressor gene KAI1, which is located on chromosome 11p11.2. Several studies have confirmed its role as metastasis suppressor in many malignancies . In patients with CLL, CD82 expression is upregulated when compared with peripheral blood mononuclear cells in normal controls. Moreover, a study evaluating gene expression in molecular subgroups of CLL found that CD82 was underexpressed in IGVH unmutated cases, suggesting a role for CD82 in clinically aggressive CLL . However specific data on CD82 expression across different disease stages has not yet been described.
In our pilot study, CLL cells from peripheral blood were labeled in PAB buffer (PBS + 1% BSA + 0.02% sodium azide) for 30 min on ice with Alexa Fluor 647 CD82 (clone ASL-24; BioLegend) and Alexa Flour 488 integrin CD49d antibodies (clone 7.2R; R&D). Control tubes of cells were labeled with isotype controls: Alexa Flour 488 mouse IgG1 κ (clone 11711; R&D) and Alexa Flour 647 mouse IgG1 κ (clone MOPC-21; BioLegend). Cells were washed 3 times with PAB buffer and surface fluorescence was measured using an Accuri C6 flow cytometer. Control tube fluorescence values were subtracted from the experimental measurements to provide the mean fluorescence values indicated.
Demographic, clinical and prognostic characteristics of early clinical stage CLL patients
n = 14
Median (Min., Max.)
71 (60, 89)
Rai Clinical stage 0
Absence of B symptomatology
Median (Min., Max.)
14.6 (10.0, 17.1)
Platelet count (X103 per microliter)
Median (Min., Max.)
171 (128, 257)
Lymphocyte count (X103 per microliter)
Median (Min., Max.)
12.2 (4.0, 58.2)
Overexpression of CD38
Presence of IgVH hypermutation
Cytogenetic abnormalities: n (%)
Follow-up duration from diagnosis (months)
Median (Min., Max.)
74.8 (32.5, 188.6)
Progression to treatment
Time to progression from diagnosis (months)
Median (Min., Max.)
59.1 (11.4, 66.5)
Despite the favorable risk features in our patient measured by conventional clinical (Rai staging) immunophenotypic and cytogenetic criteria; she presented with CNS involvement and neurologic symptoms. When comparing the adhesion molecular profile of this patient to the cohort of Rai stage 0 patients in our study we identified an inverse relationship between the expression of CD49d and CD82. With our current findings, we cannot confirm whether the change in expression of CD49d and CD82 in our case was a cause or an effect of CNS involvement. However, we hypothesize that the reduction of CD82 expression and the high level of CD49d may contribute to the CNS involvement and the poor patient outcome observed in this CLL case.
This case highlights the need for better predictive markers in CLL, especially in atypical cases such as those with CNS involvement. Our data suggest that the expression profile of CD49d and CD82 may represent potential biomarkers in predicting CNS involvement of CLL. Furthermore, this study illustrates the critical need for a better mechanistic understanding of how specific adhesion proteins regulate the interactions between CLL cells and various tissue sites. We anticipate that future large-scale studies will help to elucidate dynamic changes in CD49d and CD82 expression across different tissues, disease stages and over the course of disease progression.
Bovine serum albumin
Chronic lymphocytic leukemia
Central nervous system
Cerebral spinal fluid
Magnetic resonance imaging
White blood cells
This work was supported by funding from the New Mexico INBRE (P20 GM103451), the University of New Mexico Clinical and Translational Center (UL1 TR000041), and an award from the UNM Department of Pathology Foucar Endowment.
CMR, QYZ & JMG: Acquisition and analysis of laboratory and clinical data, drafting of the manuscript and final approval of the version to be published. JN: Acquisition of clinical data, drafting of the manuscript and final approval of the version to be published. KDM: Acquisition and analysis of laboratory data, drafting of the manuscript and final approval of the version to be published. DB: Acquisition of laboratory data, drafting of the manuscript and final approval of the version to be published.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent was obtained from the next of kin of the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The study data shown in this report was approved by the institutional ethics committee at the University of New Mexico Health Sciences Center, USA.
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