EXPRESSION OF ILT3 RECEPTORIN CHRONIC LYMPHOCYTIC LEUKEMIA

Tyrone Reid HCS 2007Mentor: Dr. Adrianna Colovai

Columbia University Medical Center ( CUMC)

INTRODUCTION

Chronic lymphocytic leukemia (CLL) is the most frequent form of leukemia in adults of the Western world. CLL is characterized by the accumulation of cancerous B lymphocytes in bone marrow, blood, and lymph nodes (1,2).

Patients with CLL have different types of the disease: some have slowly progressive (low-risk) disease, do not require anti-cancer treatment and live longer, while others have aggressive or rapidlyprogressing (high-risk) disease, require treatment and have shorter survival.

Therefore, the correct decision regarding the treatment and follow-up of patients with CLL can be only made if patients with rapidly progressive disease can be distinguished from those with stable disease at the time of diagnosis. For this, laboratory tests may be very useful.

In the present study, we attempted to identify a protein that is displayed only on the surface of cancer B cells from patients with aggressive form of CLL, and not on the surface of normal B cells or B cells from patients with slowly progressing CLL. The screening of almost 100 different proteins led us to the discovery of a protein receptor, ILT3 (immunoglobulin-like transcript 3), which is only expressed by cancer B cells from patients with aggressive CLL.

MATERIAL AND METHODS

Human specimensForty-seven patients with CLL and 25 normal volunteers were enrolled in this study, in accordance to an existing IRB protocol.

Flow cytometryCell surface staining of ILT3 protein was performed using anti-ILT3 PC5 mAb (Beckman Coulter). Cells were run and analyzed on a FACSCalibur (BD Biosciences) using CellQuestPro software.

Statistical analysisStatistical analysis was performed using Student’s t-test of significance and two-tailed Fisher exact test. Bonferroni criteria were applied.

RESULTS

ILT3 receptor is not expressed by normal B cells.

ILT3 was expressed by CLL B cells in 23 out of 47 patients.

NORMAL BLOOD HIGH-RISK CLL

Table 1. Clinical data and ILT3 expression in CLL patients

Group variableAll

patientsILT3 positive

patientsILT3 negative

patients p value

   (>10% of

CD19+CD5+ cells)(<10% of

CD19+CD5+ cells)  

No. of patients 47 23 24  

Patient age (n=47) 69 68 70 NS

No. of male patients 31 18 13 NS

No. of female patients 16 5 11  

Lymph node involvement (n=23)        

Yes 15 11 4 p=0.009

No 8 1 7  

WBC/10-9L (n=46) 56+87 61+85 40+39 NS

LDT, months (n=25) 47+45 38+38 56+52 NS

CONCLUSIONS

ILT3 protein is present on B cells from patients with high-risk CLL, but it is absent on normal B cells or B cells from patientswith low-risk CLL. Thus, detection of ILT3 by flow cytometrymay be used as a laboratory test to identify patients with high-risk CLL, and select the appropriate treatment for these patients.

This study opens new avenues in cancer research. We next planto explore the role of ILT3 protein in CLL, and identify thecellular mechanisms leading to its expression in high-risk CLL.

This study also opens new possibilities for the treatment of CLL. Since ILT3 is only present on B cells from high-risk CLL patients, new drugs that target ILT3 positive B cells may be designed. Such drugs may specifically bind to ILT3 on the cell surface of cancer B cells, and kill these cells.

REFERENCES

1. Chiorazzi N, Rai KR, Ferrarini M. Chronic lymphocytic leukemia. N Engl J Med 2005, 352:804-15.2. Shanafelt TD, Geyer SM, Kay, NE. Prognosis at diagnosis: integrating molecular biologic insights into clinical practice for patients with CLL. Blood 2004, 103:1202-10. 3. Hamblin TJ, Orchard JA, Gardiner A, Oscier DG, Davis Z, Stevenson FK. Immunoglobulin V genes and CD38 expression in CLL. Blood 2000, 95:2455-2457.4. Rassenti L and Kipps TJ. Clinical utility of assessing ZAP-70 and CD38 in chronic lymphocytic leukemia. Cytometry 2006, 708:209-213.5. Chang CC, Ciubotariu R, Manavalan JS, Yuan J, Colovai AI, Piazza F, Lederman S, Colonna M, Cortesini R, Dalla-Favera R, Suciu-Foca N. Tolerization of dendritic cells by T(S) cells: the crucial role of inhibitory receptors ILT3 and ILT4. Nat Immunol 2002;3:237-243.

Acknowledgment Acknowledgment

Dr. Adrianna ColovaiDr. Adrianna Colovai

Staff at CUMCStaff at CUMC

Dr. Sat Dr. Sat

Staff at HCSStaff at HCS