scholarly journals Differentiation-dependent expression of sialyl stage-specific embryonic antigen-1 and I-antigens on human lymphoid cells and its implications for carbohydrate-mediated adhesion to vascular endothelium

Blood ◽  
1993 ◽  
Vol 81 (1) ◽  
pp. 101-111
Author(s):  
K Ohmori ◽  
A Takada ◽  
T Yoneda ◽  
Y Buma ◽  
K Hirashima ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
B Cells ◽  
Nk Cells ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
T And B Cells ◽  
Con A ◽  
Peripheral Lymphocytes ◽  
Embryonic Antigen ◽  
Stage Specific Embryonic Antigen

Expression of two developmentally regulated carbohydrate antigens, the sialyl stage-specific embryonic antigen-1 (SSEA-1) and I-antigens, in human lymphocytes and lymphocytic leukemia cells was investigated using specific monoclonal antibodies. Sialyl SSEA-1 was expressed only on natural killer (NK) cells, and was essentially absent on resting mature T and B cells among normal peripheral lymphocytes. On the other hand, the I-antigen was strongly expressed on virtually all mature B cells, moderately expressed on most mature T cells, but not expressed on NK cells in normal donors. Expression of the two antigens on normal T and B cells was reversible; in vitro stimulation of normal lymphocytes with concanavalin A (Con A) resulted in the loss of I-antigen and appearance of sialyl SSEA-1 on CD3+ T blasts, whereas stimulation with pokeweed mitogen led to loss of I-antigen expression and appearance of sialyl SSEA-1 antigen on CD19+ B blasts. Among lymphocytic leukemia cells, sialyl SSEA-1 was detected primarily on leukemia cells having immature properties such as most common acute lymphocytic leukemia (cALL) blasts, while the I-antigen was frequently expressed on malignant cells having relatively mature properties, such as those found in adult T- cell leukemia or chronic lymphocytic leukemia, and only occasionally on cALL blasts. Among normal peripheral lymphocytes, the sialyl SSEA-1+I- antigen- NK cells selectively underwent E-selectin (ELAM-1, endothelial- leukocyte adhesion molecule-1)-dependent adhesion to endothelial cells, while the I-antigen+sialyl SSEA-1- mature T and B cells did not, in line with the recent finding that sialyl SSEA-1 serves as a specific ligand for E-selectin. Con A blasts, which are sialyl SSEA-1+I-antigen- , also exhibited significant E-selectin-dependent adhesion to endothelial cells. These results indicate that expression of the sialyl SSEA-1 and I-antigens varies alternately depending on the differentiation/activation status of the lymphocytes, and that this at least partly regulates the behavior of lymphocytes at the vessel wall.

scholarly journals Differentiation-dependent expression of sialyl stage-specific embryonic antigen-1 and I-antigens on human lymphoid cells and its implications for carbohydrate-mediated adhesion to vascular endothelium

Blood ◽  
1993 ◽  
Vol 81 (1) ◽  
pp. 101-111 ◽  
Author(s):  
K Ohmori ◽  
A Takada ◽  
T Yoneda ◽  
Y Buma ◽  
K Hirashima ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
B Cells ◽  
Nk Cells ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
T And B Cells ◽  
Con A ◽  
Peripheral Lymphocytes ◽  
Embryonic Antigen ◽  
Stage Specific Embryonic Antigen

Abstract Expression of two developmentally regulated carbohydrate antigens, the sialyl stage-specific embryonic antigen-1 (SSEA-1) and I-antigens, in human lymphocytes and lymphocytic leukemia cells was investigated using specific monoclonal antibodies. Sialyl SSEA-1 was expressed only on natural killer (NK) cells, and was essentially absent on resting mature T and B cells among normal peripheral lymphocytes. On the other hand, the I-antigen was strongly expressed on virtually all mature B cells, moderately expressed on most mature T cells, but not expressed on NK cells in normal donors. Expression of the two antigens on normal T and B cells was reversible; in vitro stimulation of normal lymphocytes with concanavalin A (Con A) resulted in the loss of I-antigen and appearance of sialyl SSEA-1 on CD3+ T blasts, whereas stimulation with pokeweed mitogen led to loss of I-antigen expression and appearance of sialyl SSEA-1 antigen on CD19+ B blasts. Among lymphocytic leukemia cells, sialyl SSEA-1 was detected primarily on leukemia cells having immature properties such as most common acute lymphocytic leukemia (cALL) blasts, while the I-antigen was frequently expressed on malignant cells having relatively mature properties, such as those found in adult T- cell leukemia or chronic lymphocytic leukemia, and only occasionally on cALL blasts. Among normal peripheral lymphocytes, the sialyl SSEA-1+I- antigen- NK cells selectively underwent E-selectin (ELAM-1, endothelial- leukocyte adhesion molecule-1)-dependent adhesion to endothelial cells, while the I-antigen+sialyl SSEA-1- mature T and B cells did not, in line with the recent finding that sialyl SSEA-1 serves as a specific ligand for E-selectin. Con A blasts, which are sialyl SSEA-1+I-antigen- , also exhibited significant E-selectin-dependent adhesion to endothelial cells. These results indicate that expression of the sialyl SSEA-1 and I-antigens varies alternately depending on the differentiation/activation status of the lymphocytes, and that this at least partly regulates the behavior of lymphocytes at the vessel wall.

scholarly journals A distinct type of sialyl Lewis X antigen defined by a novel monoclonal antibody is selectively expressed on helper memory T cells

Blood ◽  
1993 ◽  
Vol 82 (9) ◽  
pp. 2797-2805 ◽  
Author(s):  
K Ohmori ◽  
A Takada ◽  
I Ohwaki ◽  
N Takahashi ◽  
Y Furukawa ◽  
...  
Keyword(s):  
T Cells ◽  
Endothelial Cells ◽  
Nk Cells ◽  
Memory T Cells ◽  
Distinct Type ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
Healthy Individuals ◽  
Sialyl Lex ◽  
Lex Antigen

A subset of human helper memory T cells is known to adhere to E- selectin expressed on cytokine-activated endothelial cells. However, sialyl Lex antigen, the carbohydrate ligand for E-selectin, has been hardly detectable on these cells, at least when typical anti-sialyl Lex antibodies were used for detection. One of the MoAbs (2F3, IgM), which we raised against a chemically synthesized sialyl Lex glycolipid preparation, is found to react selectively to CD4+ CD45RObright+ CD45RA- helper memory T cells among peripheral lymphocytes in healthy individuals. The specificity of the antibody is in clear contrast to that of the hitherto reported typical anti-sialyl Lex antibodies FH-6 and SNH-3. These classical anti-sialyl Lex antibodies were known to react to a subset of natural killer (NK) cells, but were not reactive with any particular subset of resting peripheral T or B cells of healthy individuals if the cells were not activated. On the other hand, the newly generated 2F3 antibody specifically reacted to helper memory T cells, and did not react to NK cells, B cells, or any T cells other than helper memory T cells. When tested against the sialyl Lex-active glycolipid antigen, the reactivity of 2F3 was not significantly different from that of the classical anti-sialyl Lex antibodies. But when tested against oligosaccharides prepared from cellular glycoproteins, 2F3 detected a distinct set of O-linked oligosaccharides, which were not reactive to the classical anti-sialyl Lex antibodies. Our results suggest that various molecular species of sialyl Lex antigens are present on carbohydrate side chains of cellular glycoproteins, and that helper memory T cells express a distinct type of sialyl Lex antigen that is defined by 2F3 but is not efficiently detected by other typical anti-sialyl Lex antibodies. Among cultured lymphocytic leukemia cells, the adult T-cell leukemia (ATL) cells preferentially expressed the 2F3-defined antigen, and acute lymphocytic leukemia cells rarely expressed the antigen. The cultured ATL cells expressing the 2F3-defined antigen showed a clear E-selectin-dependent adhesion to cytokin-activated endothelial cells, and the 2F3-defined sialyl Lex antigen served as a ligand for E-selectin as ascertained by the clear inhibition of adhesion with the 2F3 antibody.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals A distinct type of sialyl Lewis X antigen defined by a novel monoclonal antibody is selectively expressed on helper memory T cells

Blood ◽  
1993 ◽  
Vol 82 (9) ◽  
pp. 2797-2805 ◽  
Author(s):  
K Ohmori ◽  
A Takada ◽  
I Ohwaki ◽  
N Takahashi ◽  
Y Furukawa ◽  
...  
Keyword(s):  
T Cells ◽  
Endothelial Cells ◽  
Nk Cells ◽  
Memory T Cells ◽  
Distinct Type ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
Healthy Individuals ◽  
Sialyl Lex ◽  
Lex Antigen

Abstract A subset of human helper memory T cells is known to adhere to E- selectin expressed on cytokine-activated endothelial cells. However, sialyl Lex antigen, the carbohydrate ligand for E-selectin, has been hardly detectable on these cells, at least when typical anti-sialyl Lex antibodies were used for detection. One of the MoAbs (2F3, IgM), which we raised against a chemically synthesized sialyl Lex glycolipid preparation, is found to react selectively to CD4+ CD45RObright+ CD45RA- helper memory T cells among peripheral lymphocytes in healthy individuals. The specificity of the antibody is in clear contrast to that of the hitherto reported typical anti-sialyl Lex antibodies FH-6 and SNH-3. These classical anti-sialyl Lex antibodies were known to react to a subset of natural killer (NK) cells, but were not reactive with any particular subset of resting peripheral T or B cells of healthy individuals if the cells were not activated. On the other hand, the newly generated 2F3 antibody specifically reacted to helper memory T cells, and did not react to NK cells, B cells, or any T cells other than helper memory T cells. When tested against the sialyl Lex-active glycolipid antigen, the reactivity of 2F3 was not significantly different from that of the classical anti-sialyl Lex antibodies. But when tested against oligosaccharides prepared from cellular glycoproteins, 2F3 detected a distinct set of O-linked oligosaccharides, which were not reactive to the classical anti-sialyl Lex antibodies. Our results suggest that various molecular species of sialyl Lex antigens are present on carbohydrate side chains of cellular glycoproteins, and that helper memory T cells express a distinct type of sialyl Lex antigen that is defined by 2F3 but is not efficiently detected by other typical anti-sialyl Lex antibodies. Among cultured lymphocytic leukemia cells, the adult T-cell leukemia (ATL) cells preferentially expressed the 2F3-defined antigen, and acute lymphocytic leukemia cells rarely expressed the antigen. The cultured ATL cells expressing the 2F3-defined antigen showed a clear E-selectin-dependent adhesion to cytokin-activated endothelial cells, and the 2F3-defined sialyl Lex antigen served as a ligand for E-selectin as ascertained by the clear inhibition of adhesion with the 2F3 antibody.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals A case of chronic lymphocytic leukemia with properties characteristic of natural killer cells

Blood ◽  
1983 ◽  
Vol 61 (5) ◽  
pp. 940-948 ◽  
Author(s):  
K Itoh ◽  
K Tsuchikawa ◽  
T Awataguchi ◽  
K Shiiba ◽  
K Kumagai
Keyword(s):  
T Cell ◽  
Chronic Lymphocytic Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Leukemia Cells ◽  
Surface Markers ◽  
T Antigens ◽  
Homogeneous Population

Abstract A case of chronic lymphocytic leukemia that consisted of a homogeneous population of cells that had properties similar to those described for natural killer (NK) cells is presented. These leukemic cells had a morphology of large granular lymphocytes (LGL) and receptors for sheep erythrocytes (ER) and for the Fc portion of IgG (Fc gamma-R). They expressed pan-T antigens OKT3 and Leu-4, but neither helper/inducer T- cell differentiation antigens OKT4 and Leu-3a nor cytotoxic/suppressor T-antigens OKT8 and Leu-2a. HNK 1 antigen, which can be expressed on human NK cells, could be detected on almost all leukemic cells (LGL), whereas a myeloid differentiation antigen, OKM1, which can be expressed on macrophages, granulocytes, and NK cells, was not detected. Thus, it was concluded that the leukemia cells had a characteristic profile of the surface markers: ER+, Fc gamma-R+, HNK-1+, OKT3+, Leu-4+, OKT4-, OKT8-, Leu-3a, Leu-2a, and OKM1-. Although freshly isolated leukemic cells showed no cytotoxicity on NK targets, after incubation at 37 degrees C, the cells did show a potent cytotoxicity on targets of erythroleukemic cell, T cell, and monocyte (but not B cell) origins. When the cells were incubated at 37 degrees C, interferon (IFN gamma) was spontaneously produced in the culture fluids. Treatment with anti- HNK-1 and complement completely abrogated expression of NK activity and interferon production of the patient's lymphocytes in culture. These characteristic features of surface markers and functions strongly suggest the possibility that the leukemia cells of this case are of NK cell origin. The relationship between this case and chronic lymphocytic leukemia of T-cell origin is discussed.

scholarly journals Interleukin-15 + thioredoxin induce DNA synthesis in B-chronic lymphocytic leukemia cells but not in normal B cells

Leukemia ◽  
1997 ◽  
Vol 11 (8) ◽  
pp. 1298-1304 ◽  
Author(s):  
O Söderberg ◽  
I Christiansen ◽  
G Nilsson ◽  
M Carlsson ◽  
K Nilsson
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Dna Synthesis ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
Interleukin 15

Arteriolar reactivity in lymphocyte-deficient mice

2011 ◽  
Vol 301 (4) ◽  
pp. H1276-H1285 ◽  
Author(s):  
Sean Leonard ◽  
B. Anne Croy ◽  
Coral L. Murrant
Keyword(s):  
B Cells ◽  
Nk Cells ◽  
Ang Ii ◽  
T And B Cells ◽  
Third Order ◽  
Immunodeficient Mice ◽  
Circulatory Control ◽  
Deficient Mice ◽  
Cell Cytokine Production

Mounting evidence suggests that lymphocytes have the capacity to contribute to the regulation of systemic circulatory control. We postulated that T and natural killer (NK) cells could modify basal microvascular activity under physiologically normal conditions. In situ intravital microscopy of mouse cremaster vasculature was used to evaluate arteriolar reactivities to the vasoconstrictors angiotensin II (ANG II) and phenylephrine (Phe) and the vasodilators acetylcholine (ACh) and adenosine (Ado) in normal [+/+; wild type (WT)] and genetically immunodeficient (T−B−NK+ or T−B−\NK−) C57BL/6 and BALB/c mice, strain backgrounds with differentially polarized T cell cytokine production. Immunodeficient mice tended to have smaller baseline and maximal diameters of third-order cremaster arterioles than their congenic WT partners. In C57BL/6, baseline diameters were similar in T-B− mice without or with NK cells; in BALB/c, baseline diameters were larger in T-B-NK− mice than in T−B−NK+ mice. Thus, at baseline, lymphocytes tended to promote vasodilation, except BALB/c NK cells, which mediated mild vasoconstriction. The presence of NK cells suppressed dilations to Ado in both strains, to ACh in the C57BL/6 strain, and dilatory responses to ANG II in C57BL/6 and to Phe in BALB/c. In the BALB/c strain, the presence of T and B cells promoted vasodilatory responses to Ado, attenuated dilations to low ACh concentrations, and exaggerated dilation and constriction responses to ANG II. Thus, under agonist challenge, NK cells generally promote constriction, whereas influences of T and B cells depend upon the stimulus. Therefore, lymphocytes or their products have physiological influences on microvascular arteriolar reactivity.

IL-21 Plus CpG ODN Induces Granzyme B-Dependent Induction of Apoptosis in CD5-Positive B Cells Including B-CLL Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2823-2823
Author(s):  
Sue E. Blackwell ◽  
Bernd Jahrsdoerfer ◽  
James E. Wooldridge ◽  
Jian Huang ◽  
Melinda W. Andreski ◽  
...  
Keyword(s):  
B Cells ◽  
Cord Blood ◽  
Granzyme B ◽  
Lymphocytic Leukemia ◽  
Cpg Odn ◽  
T And B Cells ◽  
B1 Cells ◽  
Lymphocyte Populations

Abstract Interleukin 21 (IL-21), a recently discovered cytokine with structural homology to IL-2, IL-4 and IL-15, has pleiotropic effects on lymphocyte populations including NK, T and B cells and is currently undergoing early clinical evaluation. We explored the effect of the combination of IL-21 and immunostimulatory CpG ODN on B chronic lymphocytic leukemia (B-CLL), and other CD5-positive B cells. IL-21 plus CpG ODN were synergistic in their ability to induce apoptosis of the B-CLL cells, and also induced production and secretion of granzyme B from the B-CLL cells. B-CLL cells treated with IL-21 and CpG ODN were capable of inducing apoptosis of untreated autologous B-CLL cells. This bystander killing was inhibited by anti-granzyme B antibodies. The effect was observed in all cases of CD5-positive B-CLL, but not in CD5-negative B-CLL samples. IL-21 plus CpG ODN also induced granzyme B production and apoptosis of benign CD5-positive B1 cells obtained from umbilical cord blood. In contrast, the number of CD5-negative B2 cells increased in the same samples during in vitro culture, resulting in a decreased ratio of CD5-positive to CD5-negative cord blood B cells (Fig. 1). Our results indicate the combination of IL-21 and CpG ODN is able to induce apoptosis of both benign and malignant CD5-positive B cells. Given the suspected role of B1 cells in autoimmune diseases, our findings could have important implications for the understanding of their pathogenetic mechanisms. These results might also open new avenues for the development of novel therapies for both autoimmune dieseases and CD5-positive B-CLL. Figure 1. IL- 21 and CpG ODN therapy selectively eliminates CD5 positive B cells in cord blood. Figure 1. IL- 21 and CpG ODN therapy selectively eliminates CD5 positive B cells in cord blood.

Increased Expression of PD-1 on CD4+ T Cells from Patients with Chronic Lymphocytic Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4154-4154
Author(s):  
Mary M Sartor ◽  
David J Gottlieb
Keyword(s):  
T Cells ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Nk Cells ◽  
Cd4 T Cells ◽  
Mononuclear Cells ◽  
Lymphocytic Leukemia ◽  
Effector Memory ◽  
Cd4 Cells ◽  
Normal Peripheral Blood

Abstract Although the predominant finding in patients with chronic lymphocytic leukemia (CLL) is an expansion of monoclonal B lymphocytes, a polyclonal expansion of T cells co-exists in CLL patients. Allogenic stem cell transplants for CLL suggest that a significant graft versus leukaemia effect mediated through recognition of minor MHC or leukaemia specific antigens can be achieved. Since it appears that the immune system and probably T cells recognise CLL cells, it is possible that one or more T cell defects might contribute to the initiation or maintenance of a clone of CLL lymphocytes. PD-1 is a coinhibitory molecule that is expressed on T cells in patients with chronic viral infections. It has been suggested that PD-1 expression might be a marker of cell exhaustion due to antigenic overstimulation. We examined the expression of PD-1 and its naturally occurring ligands PD-L1 and PD-L2 on both B and T cells in patients with CLL and compared this with expression on normal peripheral blood mononuclear cells. We found that PD-1 was expressed on over 10% of CD4+ T cells in 7 of 9 cases of CLL (mean 22±16%) but not on CD4+ T cells in any of 9 normal donors (mean 0±0%), p=0.0009. There was no difference in PD-1 expression on CD8+ or CD14+ PBMCs from CLL patients and normal donors (for CD8+ 24±21% and 19±16% for CLL and normals; for CD14+ 58±16% and 71±31% for CLL and normals). More than 10% of CD5+/19+ CLL cells expressed PD-1 in 7 of 10 cases (mean 18±18%) while more than 10% of normal B cells from 6 of 7 donors also expressed PD-1 (mean 49±30%). We examined the expression of PD-1 on naïve, central memory, effector memory and terminally differentiated subsets of CD4+ cells (CD62L+CD45RA+, CD62L+CD45RA−, CD62L−CD45RA− and CD62L−CD45RA+ respectively) from CLL patients and normal donors. The expression of PD-1 was higher on CD4+ cells from CLL patients in all subsets. The effect was most prominent in the effector memory subset (mean 54±4% for CLL patients versus 26±17% for normal donors, p=0.02). We looked for expression of PD-L1 and PD-L2 on T cells, B cells, monocytes and NK cells from CLL patients and normal donors. PD-L1 was only expressed on monocytes (mean 30±23%) and NK cells (mean 14±19%) from CLL patients and on monocytes from normal donors (mean 35±26%). There was no expression of PD-L2 on any cell type in either CLL patients or normal donors. We conclude that there is increased expression of the co-inhibitory molecule PD-1 on CD4+ T cells in patients with CLL. Ligation of PD-1 by PD-L1 expressed on monocytes or NK cells could inhibit immune responses to tumor and infectious antigens leading to persistence of clonally expanded cells and predisposition to opportunistic pathogens.

B Cell Activating Factor and c-Myc Regulate the Progression of Chronic Lymphocytic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 359-359
Author(s):  
Weizhou Zhang ◽  
Arnon P. Kater ◽  
Han-Yu Chuang ◽  
Thomas Enzler ◽  
George F. Widhopf ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Disease Progression ◽  
Cell Population ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
Low Grade ◽  
B Cell Activating Factor

Abstract Abstract 359 Chromosomal translocations involving c-Myc are frequently found in high grade lymphoma and multiple myeloma. In contrast, c-Myc translocations rarely occur in low-grade lymphomas/leukemias like chronic lymphocytic leukemia (CLL), but when present they are associated with rapid disease progression and bad prognosis. Overexpression of c-myc may also be the result of increased transcription by several proto-oncogene transcription factors, including NF-kB. Mice with c-Myc de-regulation at different stages of B cell development develop either aggressive B cells lymphomas or plasma cell neoplasm. So far, no c-Myc mouse model developed low-grade lymphoma/leukemia. iMycCa mice develop an expansion of CD5+ peritoneal B1 cells, as compared with WT littermates mice. These mice have a normal life-span and very rarely develop B cell lymphoma at older age. Interestingly, in iMycCa mice mature B cells, but not plasma cells,could be rescued from apoptosis by administration of B cell-activating factor belonging to the TNF family (BAFF). To our surprise, double transgenic iMycCa/Baff-Tg (Myc/Baff) mice developed a disease resembling human CLL, with dramatically shorter mean survival than parental strains, due to early onset and rapid clonal expansion of a mature CD5+B220low B cell population. Those cells transferred the disease into Baff-Tg (Baff) mice with marked infiltration in lymphoid organs and bone marrow. Gene-expression analyses revealed that among the genes altered in Myc/Baff CD5+B220lowleukemia cells were those with known relevance to human CLL disease, including elevated anti-apoptotic Bcl2 family members. Apart from studies on individual genes, sub-network analysis was performed which showed enrichment of apoptosis-related and stress-induced gene sets in Myc/Baff CD5+CD3- leukemia cells. The NF-kB gene set, a major target downstream of BAFF signaling, was also enriched in Myc/Baff CD5+CD3- leukemia cells. We observed a continuum in levels of c-MYC mRNA in 166 samples using Affymetrix array analyses. Changes in c-Myc protein expression were confirmed by immunoblot analyses and correlated with disease progression. In accordance with the functions of c-Myc as a promoter of cell cycle progression, as well as apoptosis, we found enhanced spontaneous cell death in vitro in CLL cells expressing high levels of c-Myc, which could be abrogated by co culture with BAFF expressing nurse-like cells (NLC) or recombinant BAFF. In addition to its anti-apoptotic role, BAFF treatment of primary human CLL cells led to dramatically enhanced expression of c-Myc through the IKK/NF-kB pathway. Inhibition of the NF-kB pathway significantly reduced viability of both Myc/Baff CD5+CD3- leukemia cells and human CLL cells co-cultured with NLC. Also it significantly lowered CD5+B220low leukemia cell population in blood and spleen, and prevented the infiltration of leukemia cells into lymph nodes and bone marrow of transplanted mice. This study demonstrates a potential pathologic role for c-Myc, in the pathogenesis and progression of CLL. Disclosures: No relevant conflicts of interest to declare.

Targeting of Chronic Lymphocytic Leukemia B Cells with a Novel Monoclonal Antibody to ROR1

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 984-984
Author(s):  
Bing CUi ◽  
George F. Widhopf ◽  
Jian Yu ◽  
Daniel Martinez ◽  
Esther Avery ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Adoptive Transfer ◽  
Leukemia Cell ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Phosphorylated Akt

Abstract Abstract 984 ROR1 is an orphan receptor tyrosine kinase that is expressed on leukemia cells of patients with chronic lymphocytic leukemia (CLL), but not on most adult tissues of healthy adults, including CD5+ B cells. To generate anti-ROR1 antibodies, we immunized mice using different strategies employing vaccines comprised of recombinant ROR1 protein, polynucleotide-ROR1 vaccines and CD154 genetic adjuvants, or replication-defective adenovirus vectors encoding ROR1 and CD154. We extirpated the spleens of animals that developed high-titer serum anti-ROR1 antibodies and used these to generate monoclonal-antibody-(mAb)-producing hybridomas or antibody phage-display libraries that subsequently were screened for ROR1-binding. Over 70 unique mAbs were generated that each bound the extra-cellular domain of native ROR1. Most mAbs recognized an epitope(s) within the ROR1 Ig-like domain, which appears to represent the immune dominant epitope. Other mAb recognized epitopes within the conserved ROR1 Kringle domain. One mAb (UC D10-001) had distinctive binding to an intradomain epitope of human ROR1 (hROR1). UC D10-001 was the only mAb we found directly cytotoxic for hROR1-expressing leukemia cells cultured in media without complement for 6 hours. We found that UC D10-001 could induce significant reductions in basal levels of phosphorylated AKT in hROR1-expressing leukemia cells. Moreover, UC D10-001 significantly decreased the basal levels of phosphorylated AKT in freshly isolated human CLL cells (N=4) to levels comparable to that observed in co-cultures containing 10 mM LY294002, a broad-spectrum inhibitor of PI3K. We examined whether this mAb had cytotoxic activity for leukemia cell in vivo. For this we examined whether we could inhibit the adoptive transfer of human-ROR1-expressing leukemia cells to young, syngeneic recipient mice made transgenic for human ROR1 under control of a B-cell specific promoter. Cohorts of 5 animals per group were each given intravenous injections of antibody at a dose of at 10 mg/kg. Each cohort was treated with UC D10-001, control IgG, or 4A5, an anti-ROR1 mAb specific for a non-cross-reactive epitope located in the Ig-like domain of ROR1. Each animal received an intravenous injection of 5 × 105 ROR1-expressing leukemia cells and then was assessed weekly for circulating leukemia cells by flow cytometry. UC D10-001, but not control IgG or 4A5, significantly inhibited engraftment of the ROR1+ leukemia. Four weeks after adoptive transfer, animals treated with UC D10-001 had a 10-fold lower median number of leukemia B cells in the blood than animals treated with control IgG or 4A5. We also tested UC D10-001 for its capacity to induce clearance of human ROR1+ CLL cells engrafted into the peritoneal cavity of Rag-2−/−/γc−/− immune deficient mice. Each of these mice received intraperitoneal injections of equal numbers of human ROR1+ CLL cells prior to receiving D10-001, control IgG, or 4A5, each at 10 mg/kg. These animals were sacrificed seven days later and the human leukemia cells were harvested via peritoneal lavage. In mice treated with UC D10-001 we harvested an average of only 6 × 104 ± 3 × 104 CLL cells. This number of cells was significantly less than the average number of CLL cells harvested from control IgG or 4A5-treated mice (8 × 105 ± 4 × 105 or 7 × 105 ± 2 × 105, respectively, p <0.01). These studies indicate that the anti-ROR1 mAb UC D10-001 can be directly cytotoxic for ROR1-expressing leukemia cells in vitro and in vivo, a property that apparently is unique to this mAb among other anti-ROR1 mAbs. Because of the restricted expression of ROR1 on leukemia cells and the distinctive properties of this mAb, we propose that UC D10-001 might have potential utility in the treatment of patients with CLL. Disclosures: No relevant conflicts of interest to declare.

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