Leukemic T cells are specifically enriched in a unique CD3^dimCD7^low subpopulation of CD4⁺ T cells in acute‐type adult T‐cell leukemia

Abstract

The morphological discrimination of leukemic from non-leukemic T cells is often difficult in adult T-cell leukemia (ATL) as ATL cells show morphological diversity, with the exception of typical ''flower cells.'' Because defects in the expression of CD3 as well as CD7 are common in ATL cells, we applied multi-color flow cytometry to detect a putative leukemia-specific cell population in the peripheral blood from ATL patients. CD4 + CD14) cells subjected to two-color analysis based on a CD3 vs CD7 plot clearly demonstrated the presence of a CD3 dim CD7 low subpopulation in each of nine patients with acute-type ATL. The majority of sorted cells from this fraction showed a flower cell-like morphology and carried a high proviral load for the human T-cell leukemia virus type 1 (HTLV-I). Genomic integration site analysis (inverse long-range PCR) and analysis of the T cell receptor Vb repertoire by flow cytometry indicated that the majority of leukemia cells were included in the CD3 dim CD7 low subpopulation. These results suggest that leukemic T cells are specifically enriched in a unique CD3 dim CD7 low subpopulation of CD4 + T cells in acute-type ATL. (Cancer Sci 2011; 102: 569-577)

CADM1 Expression and Stepwise Downregulation of CD7 Are Closely Associated with Clonal Expansion of HTLV-I–Infected Cells in Adult T-cell Leukemia/Lymphoma

“…The MT-2 cell line was a gift from Dr. Miyoshi (Kochi University, Kochi, Japan) and ST-1 was from Dr. Nagai (Nagasaki University, Nagasaki, Japan). Peripheral blood samples were collected from in-patients and outpatients at our hospital, as described in our previous reports (14,15). As shown in Supplementary Table S1, 26 cases were analyzed (10 cases of asymptomatic carrier; 5 cases of smoldering-type; 6 cases of chronic-type; and 5 cases of acute-type).…”

“…Peripheral blood mononuclear cells (PBMC) were isolated from whole blood by density gradient centrifugation, as described previously (14). An unlabeled CADM1 antibody (clone 3E1) and an isotype control chicken immunoglobulin Y (IgY) antibody were purchased from MBL.…”

“…For clonality analysis, inverse long PCR was performed as described previously (14). First, 1 mg genomic DNA extracted from the FACS-sorted cells was digested with PstI or EcoRI at 37 C overnight.…”

“…Quantification of HTLV-I proviral load by real-time quantitative PCR PVL in FACS-sorted PBMCs was quantified by real-time quantitative PCR (TaqMan method) using the ABI Prism 7000 sequence detection system (Applied Biosystems), as described previously (14,30).…”

“…However, the expression levels of these markers vary among patients, which often make it difficult to identify ATL cells specifically based on the immunophenotype. Previously, we focused on downregulated markers in acutetype ATL cells, such as CD3 and CD7, and successfully purified ATL cells using the CD3 versus CD7 plot of CD4 þ cells (14). Analysis of other clinical subtypes (indolent ATLs and HTLV-I asymptomatic carriers; AC) revealed that HTLV-I-infected and clonally expanded cells were purified similarly and that the subpopulations with downregulated CD7 grew concomitantly with the progression of HTLV-I infection (15).…”