Regulatory T cells and immunodeficiency in mycosis fungoides and Sézary syndrome

Cutaneous T-cell lymphoma (CTCL) is the term for diseases characterized by primary accumulation of malignant T cells in the skin. Patients with the two predominant clinical forms of CTCL called mycosis fungoides (MF) and Sézary syndrome (SS) characteristically develop severe immunodeficiency during disease progression and consequently patients with advanced disease frequently die of infections and not from the tumor burden. For decades, it has been suspected that the malignant T cells actively drive the evolving immunodeficiency to avoid antitumor immunity, yet, the underlying mechanisms remain unclear. The identification of a subset of highly immunosuppressive regulatory T cells (Tregs) triggered a variety of studies investigating if MF and SS are malignant proliferations of Tregs but seemingly discordant findings have been reported. Here, we review the literature to clarify the role of Tregs in MF and SS and discuss the potential mechanisms driving the immunodeficiency.

COX-2-dependent PGE(2) acts as a growth factor in mycosis fungoides (MF)

Cancer often originates from a site of persistent inflammation, and the mechanisms turning chronic inflammation into a driving force of carcinogenesis are intensely investigated. Cyclooxygenase-2 (COX-2) is an inducible key modulator of inflammation that carries out the rate-limiting step in prostaglandin synthesis. Aberrant COX-2 expression and prostaglandin E(2) (PGE(2)) production have been implicated in tumorigenesis. In this study we show that COX-2 is ectopically expressed in malignant T-cell lines from patients with cutaneous T-cell lymphoma (CTCL) as well as in situ in lymphocytic cells in 21 out of 22 patients suffering from mycosis fungoides (MF) in plaque or tumor stage. COX-2 is not expressed in lymphocytes of 11 patients with patch-stage MF, whereas sporadic COX-2 staining of stromal cells is observed in the majority of patients. COX-2 expression correlates with a constitutive production of PGE(2) in malignant T cells in vitro. These cells express prostaglandin receptors EP3 and EP4 and the receptor antagonist as well as small interfering RNA (siRNA) directed against COX-2, and specific COX-2 inhibitors strongly reduce their spontaneous proliferation. In conclusion, our data indicate that COX-2 mediated PGE(2) exerts an effect as a tumor growth factor in MF.

Gamma c-signaling cytokines induce a regulatory T cell phenotype in malignant CD4+ T lymphocytes

In this study, we demonstrate that malignant mature CD4(+) T lymphocytes derived from cutaneous T cell lymphomas (CTCL) variably display some aspects of the T regulatory phenotype. Whereas seven cell lines representing a spectrum of primary cutaneous T cell lymphoproliferative disorders expressed CD25 and TGF-beta, the expression of FOXP3 and, to a lesser degree, IL-10 was restricted to two CTCL cell lines that are dependent on exogenous IL-2. IL-2, IL-15, and IL-21, all of which signals through receptors containing the common gamma chain, induced expression of IL-10 in the IL-2-dependent cell lines as well as primary leukemic CTCL cells. However, only IL-2 and IL-15, but not IL-21, induced expression of FOXP3. The IL-2-triggered induction of IL-10 and FOXP3 expression occurred by signaling through STAT3 and STAT5, respectively. Immunohistochemical analysis of the CTCL tissues revealed that FOXP3-expressing cells were common among the CD7-negative enlarged atypical and small lymphocytes at the early skin patch and plaque stages. Their frequency was profoundly diminished at the tumor stage and in the CTCL lymph node lesions with or without large cell transformation. These results indicate that the T regulatory cell features are induced in CTCL T cells by common gamma chain signaling cytokines such as IL-2 and do not represent a fully predetermined, constitutive phenotype independent of the local environmental stimuli to which these malignant mature CD4(+) T cells become exposed.

EBV PCR in the diagnosis and monitoring of posttransplant lymphoproliferative disorder: results of a two-arm prospective trial

While EBV PCR is used in the management of PTLD, the optimal primer set, relative importance of intracellular versus free plasma EBV, and the baseline profile in an organ transplant population remains unclear. We performed a prospective 2-arm trial utilizing an EBV PCR panel measuring LMP-1, EBER-1 and EBNA-1 in both free plasma as well as intracellular whole blood. Control Arm A consisted of 31 lung transplant patients and Arm B consisted of 35 transplant patients being evaluated for possible PTLD. In Arm A, 1/31 (3%) patients developed a transient plasma EBV load. Thirteen of 31 (42%) had detectable intracellular EBV. In Arm B, 17 (49%) patients were diagnosed with PTLD. Thirteen (76%) had EBV-positive PTLD with 12/13 (92%) having detectable EBV by PCR. The EBV PCR panel had a high sensitivity (92%), specificity (72%), positive predictive value (PPV) (71%) and negative predictive value (NPV) (93%) for diagnosing EBV-positive PTLD and followed patients' clinical course well (p < 0.001). Comparing the individual PCR assays, plasma EBNA PCR was superior with high sensitivity (77%), specificity (100%), PPV (100%) and NPV (86%). We conclude that EBV PCR is a useful test for managing PTLD patients. While plasma EBNA PCR is the best single assay for diagnosing and monitoring PTLD, the complete PCR panel is superior for ruling out its presence.

Oncogenic tyrosine kinase NPM/ALK induces activation of the rapamycin-sensitive mTOR signaling pathway

The mechanisms of cell transformation mediated by the nucleophosmin (NPM)/anaplastic lymphoma kinase (ALK) tyrosine kinase are only partially understood. Here, we report that cell lines and native tissues derived from the NPM/ALK-expressing T-cell lymphoma display persistent activation of mammalian target of rapamycin (mTOR) as determined by phosphorylation of mTOR targets S6rp and 4E-binding protein 1 (4E-BP1). The mTOR activation is serum growth factor-independent but nutrient-dependent. It is also dependent on the expression and enzymatic activity of NPM/ALK as demonstrated by cell transfection with wild-type and functionally deficient NPM/ALK, small interfering RNA (siRNA)-mediated NPM/ALK depletion and kinase activity suppression using the inhibitor WHI-P154. The NPM/ALK-induced mTOR activation is transduced through the mitogen-induced extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway and, to a much lesser degree, through the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway. Accordingly, whereas the low-dose PI3K inhibitor wortmannin and Akt inhibitor III profoundly inhibited Akt phosphorylation, they had a very modest effect on S6rp and 4E-BP1 phosphorylation. In turn, MEK inhibitors U0126 and PD98059 and siRNA-mediated depletion of either ERK1 or ERK2 inhibited S6rp phosphorylation much more effectively. Finally, the mTOR inhibitor rapamycin markedly decreased proliferation and increased the apoptotic rate of ALK+TCL cells. These findings identify mTOR as a novel key target of NPM/ALK and suggest that mTOR inhibitors may prove effective in therapy of ALK-induced malignancies.

Oncogenic tyrosine kinase NPM/ALK induces activation of the MEK/ERK signaling pathway independently of c-Raf

The mechanisms of cell transformation mediated by the highly oncogenic, chimeric NPM/ALK tyrosine kinase remain only partially understood. Here we report that cell lines and native tissues derived from the NPM/ALK-expressing T-cell lymphoma (ALK+ TCL) display phosphorylation of the extracellular signal-regulated protein kinase (ERK) 1/2 complex. Transfection of BaF3 cells with NPM/ALK induces phosphorylation of EKR1/2 and of its direct activator mitogen-induced extracellular kinase (MEK) 1/2. Depletion of NPM/ALK by small interfering RNA (siRNA) or its inhibition by WHI-154 abrogates the MEK1/2 and ERK1/2 phosphorylation. The NPM/ALK-induced MEK/ERK activation is independent of c-Raf as evidenced by the lack of MEK1/2 and ERK1/2 phosphorylation upon c-Raf inactivation by two different inhibitors, RI and ZM336372, and by its siRNA-mediated depletion. In contrast, ERK1/2 activation is strictly MEK1/2 dependent as shown by suppression of the ERK1/2 phosphorylation by the MEK1/2 inhibitor U0126. The U0126-mediated inhibition of ERK1/2 activation impaired proliferation and viability of the ALK+ TCL cells and expression of antiapoptotic factor Bcl-xL and cell cycle-promoting CDK4 and phospho-RB. Finally, siRNA-mediated depletion of both ERK1 and ERK2 inhibited cell proliferation, whereas depletion of ERK 1 (but not ERK2) markedly increased cell apoptosis. These findings identify MEK/ERK as a new signaling pathway activated by NPM/ALK and indicate that the pathway represents a novel therapeutic target in the ALK-induced malignancies.

Multi-gene epigenetic silencing of tumor suppressor genes in T-cell lymphoma cells; delayed expression of the p16 protein upon reversal of the silencing

To understand better T-cell lymphomagenesis, we examined promoter CpG methylation and mRNA expression of closely related genes encoding p16, p15, and p14 tumor suppressor genes in cultured malignant T-cells that were derived from cutaneous, adult type, and anaplastic lymphoma kinase (ALK)-expressing T-cell lymphomas. p16 gene was epigenetically silenced in all but one of the 10 malignant T-cell lines examined, p15 gene silenced in roughly half of the lines, and p14 was the least frequently affected. Extensive methylation of the p16 promoter was seen in six out of 10 cutaneous T-cell lymphoma patient samples and corresponded with lack of p16 protein expression in the cases examined. Treatment of cultured T-cells with the DNA methyltransferase inhibitor, 5-aza-2-deoxy-cytidine, resulted in reversal of the p16 gene silencing. However, expression of p16 protein was delayed in relationship to p16 promoter demethylation and required up to 3 weeks to occur, seemingly reflecting late activation of the p16 gene. These findings indicate that epigenetic silencing affects in T-cell malignancies, often simultaneously, several tumor suppressor genes that impact on key cell functions. The observed differential silencing of p16 and p14, and to a lesser degree p15 gene, indicates that the silencing is governed by precise, promoter region-specific mechanisms. The study provides also further rationale for treatment of at least some types of T-cell lymphomas with DNA methyltransferase inhibitors to target the epigenetically silenced tumor suppressor genes.

Role of signal transducer and activator of transcription 5 in nucleophosmin/ anaplastic lymphoma kinase-mediated malignant transformation of lymphoid cells

The NPM/ALK fusion gene, formed by the t(2;5) translocation in anaplastic large-cell lymphoma, encodes a M(r) 75,000 hybrid protein that containsthe amino-terminal portion of the nucleolar phosphoprotein nucleophosmin(NPM) joined to the entire cytoplasmic portion of the receptor tyrosine kinase anaplastic lymphoma kinase (ALK). NPM/ALK encodes a constitutively activated tyrosine kinase that belongs to the family of tyrosine kinases activated by chromosomal translocation. Our studies show that NPM/ALK, similar to other members of this family, activates signal transducer and activator of transcription 5 (STAT5) and that this activation is essential for lymphomagenesis. NPM/ALK-mediated activation of STAT5 was demonstrated by detection of: (a) constitutive tyrosine phosphorylation and enhanced DNA binding ability of STAT5 in NPM/ALK-transformed cells; and (b) NPM/ALK-dependent stimulation of STAT5-mediated transactivation of the beta-casein promoter. Retroviral infection of NPM/ALK+ cells with a dominant-negative STAT5B mutant (STAT5-DNM) inhibited the antiapoptotic activity of NPM/ALK in growth factor and serum-free medium. In addition, STAT5-DNM inhibited proliferation and diminished the clonogenic properties of NPM/ALK-positive cells. Finally, SCID mice injected with NPM/ALK+ cells infected with a virus carrying STAT5-DNM survived significantly longer than mice inoculated with NPM/ALK+ cells infected with the empty virus. Necropsy identified a widespread ALK+ lymphoma in lymph nodes and liver of the affected animals. Together, our data indicate that NPM/ALK-induced activation of STAT5 may play an important role in NPM/ALK-mediated lymphomagenesis.

SHP-1 expression by malignant small B-cell lymphomas reflects the maturation stage of their normal B-cell counterparts

SHP-1 is a protein phosphotyrosine phosphatase that plays an important role in modulating intracellular signaling, which regulates cell activation, proliferation, differentiation, and migration. It is a negative regulator of signal transduction induced by a number of cell receptors. Our immunohistochemical examination of paraffin-embedded reactive lymph nodes and lymphoid tissues revealed that B lymphocytes in follicle germinal centers do not express SHP-1. A weak staining of the B cells in the germinal center light zones was detected when an ultrasensitive amplification system was used. In contrast, normal B cells in mantle and marginal zones as well as interfollicular B lymphocytes and plasma cells displayed strong immunoreactivity. This pattern of SHP-1 expression was repeated in small B-cell lymphomas. All cases of mantle cell lymphoma (12 of 12), marginal zone lymphoma (10 of 10), and chronic lymphocytic leukemia/small lymphocytic lymphoma (13 of 13) expressed SHP-1 protein. However, only 1 of 30 cases of grade 1 follicle center cell lymphoma expressed SHP-1. Our observations highlight the biologic functions of SHP-1 and demonstrate that the SHP-1 expression pattern by small B-cell lymphomas reflects the maturation stage of their normal cell counterparts. These results indicate that determination of SHP-1 expression may help in the differential diagnosis of small B-cell lymphomas.

Constitutive STAT3-activation in Sezary syndrome: tyrphostin AG490 inhibits STAT3-activation, interleukin-2 receptor expression and growth of leukemic Sezary cells

Interleukin-2 (IL-2) is a growth factor which upon binding to high-affinity receptors (IL-2Ralphabetagamma) triggers mitogenesis in T cells. IL-2Ralpha expression is restricted to T cells which have recently encountered antigen, and in healthy individuals the majority (>95%) of peripheral T cells are IL-2Ralpha negative. An aberrant expression of IL-2Ralpha has recently been described in cutaneous T-cell lymphoma (CTCL). Here, we study the regulation of IL-2Ralpha expression and STATs in a tumor cell line obtained from peripheral blood from a patient with Sezary syndrome (SS), a leukemic variant of CTCL. We show that (1) STAT3 (a transcription factor known to regulate IL-2Ralpha transcription) is constitutively tyrosine-phosphorylated in SS tumor cells, but not in non-malignant T cells; (2) STAT3 binds constitutively to a STAT-binding sequence in the promotor of the IL-2Ralpha gene; (3) the Janus kinase inhibitor, tyrphostine AG490, inhibits STAT3 activation, STAT3 DNA binding, and IL-2Ralpha mRNA and protein expression in parallel; and (4) tyrphostine AG490 inhibits IL-2 driven mitogenesis and triggers apoptosis in SS tumor cells. In conclusion, we provide the first example of a constitutive STAT3 activation in SS tumor cells. Moreover, our findings suggest that STAT3 activation might play an important role in the constitutive IL-2Ralpha expression, survival, and growth of malignant SS cells.

Comparative genome-scale analysis of gene expression profiles in T cell lymphoma cells during malignant progression using a complementary DNA microarray

Using a cDNA microarray, we compared the expression of approximately 8000 genes between two unique, clonally related T cell lines derived from different stages of a progressive T cell lymphoma involving skin. A total of 180 genes was found to be differentially expressed at the RNA level by a factor of fivefold or greater. Compared with the cells from the earlier, clinically indolent stage of the lymphoma, 56 genes were up-regulated, whereas 124 genes were down-regulated in the cells from the advanced, clinically aggressive stage lymphoma. The functions of approximately 65% of these genes are currently unknown. The 22 genes with a known function that were up-regulated in the advanced lymphoma cells included several genes involved in promotion of cell proliferation and survival as well as drug resistance. The 42 functionally characterized genes that were down-regulated in the advanced lymphoma cells included negative regulators of cell activation and cell cycle, and mediators of cell adhesion, apoptosis, and genome integrity. The differential expression identified by the cDNA microarray analysis was confirmed for selected genes by reverse transcription-polymerase chain reaction and Northern blotting. The identified differences in gene expression may be related to the differences in behavior between the early and advanced stages of the T cell lymphoma and point to directions for further investigations into mechanisms of lymphoma progression.

Hepatosplenic and subcutaneous panniculitis-like gamma/delta T cell lymphomas are derived from different Vdelta subsets of gamma/delta T lymphocytes

Gamma/delta T cell lymphomas (gamma/delta TCL) represent rare, often aggressive types of T cell malignancy that are clinically and pathologically diverse. Most gamma/delta TCL occur as a hepatosplenic or subcutaneous type. To date, analysis of the T cell receptor delta (TCRS) gene repertoire of hepatosplenic gamma/delta TCL (gamma/delta HSTCL) and subcutaneous panniculitis-like gamma/delta TCL (gamma/delta SPTCL) has been reported only in a limited number of cases. In this study we analyzed 11 gamma/delta HSTCL and 4 gamma/delta SPTCL by polymerase chain reaction and immunostaining to determine their usage of the Vdelta subtypes (Vdelta1-6). It is noteworthy that 10 of 11 gamma/delta HSTCL expressed the Vdelta1 gene. The remaining case also expressed T cell receptor delta (TCRS) as determined by flow cytometry and TCRdelta rearrangement in Southern blot. However, the Vdelta gene expressed by this lymphoma could not be determined, which suggests usage of an as yet unidentified Vdelta gene. In striking contrast to the gamma/delta HSTCL, all 4 gamma/delta SPTCL expressed the Vdelta2 gene. Our data demonstrate that gamma/delta HSTCL are preferentially derived from the Vdelta1 subset of gamma/delta T lymphocytes, whereas gamma/delta SPTCL are preferentially derived from the Vdelta2 subset. The pattern of Vdelta gene expression in HSTCL and SPTCL corresponds to the respective, predominant gamma/delta T cell subsets normally found in the spleen and skin. This finding suggests that gamma/delta TCL are derived from normal gamma/delta T lymphocytes which reside in the affected tissues. Furthermore, the selective, lymphoma type-specific Vdelta gene segment usage may provide a molecular tool to distinguish better among various types of gamma/delta TCL lymphoma particularly in the clinically advanced, widely disseminated cases.

Role of phosphatidylinositol 3-kinase-Akt pathway in nucleophosmin/anaplastic lymphoma kinase-mediated lymphomagenesis

The NPM/ALK fusion gene, formed by the t(2;5) translocation in a subset of anaplastic large cell lymphomas, encodes a Mr 75,000 hybrid protein that contains the NH2-terminal portion of the nucleolar phosphoprotein nucleophosmin (NPM) joined to the entire cytoplasmic portion of the receptor tyrosine kinase anaplastic lymphoma kinase (ALK). NPM/ALK encodes a constitutively activated tyrosine kinase that belongs to the family of tyrosine kinases activated by chromosomal translocations. Our studies showed that NPM/ALK, similar to other members of this family, activates phosphatidylinositol 3-kinase (PI3K) and its downstream effector, serine/threonine kinase (Akt). PI3K was found in complex with NPM/ALK. Both PI3K and Akt kinase were permanently activated in NPM/ALK-transfected BaF3 murine hematopoietic cells and in NPM/ALK-positive, but not in NPM/ALK-negative, patient-derived anaplastic large cell lymphoma cell lines. In addition, Akt was phosphorylated/activated in protein samples isolated from four patients diagnosed with ALK-positive T/null-cell lymphomas. The PI3K inhibitors wortmannin and LY294002 induced apoptosis in NPM/ALK+ cells but exerted only minor effects on the control BaF3 parental cells and peripheral blood mononuclear cells stimulated by growth factors. Furthermore, retroviral infection of NPM/ALK+ BaF3 cells with a dominant-negative PI3K mutant (delta p85) or a dominant-negative Akt mutant (K179M) inhibited proliferation and clonogenic properties of the infected cells. Finally, the Akt mutant (K179M) suppressed the tumorigenicity of NPM/ALK-transfected BaF3 cells injected into syngeneic mice. In conclusion, our data indicate that NPM/ALK constitutively activates the PI3K-Akt pathway and that this pathway plays an important role in the NPM/ALK-mediated malignant transformation.

Lack of phosphotyrosine phosphatase SHP-1 expression in malignant T-cell lymphoma cells results from methylation of the SHP-1 promoter

SHP-1 is an important negative regulator of signaling by several receptors including receptors for interleukin-2 (IL-2R) and other cytokines. SHP-1 acts by dephosphorylating the receptors and receptor-associated kinases such as IL-2R-associated Jak3 kinase. We found that SHP-1 protein was not detectable or greatly diminished in most (six of seven) T cell lines derived from various types of T cell lymphomas and all (eight of eight) cutaneous T-cell lymphoma tissues with a transformed, large-cell morphology. All T-cell lymphoma lines tested (eight of eight) expressed diminished amounts or no detectable SHP-1 mRNA. These T cell lines did not, however, carry any mutations in the SHP-1 gene-coding, splice-junction, and promoter regions. Importantly, SHP-1 DNA promoter region in the T cell lines was resistant to digestion with three different methylation-sensitive restriction enzymes. This resistance was reversed by treatment of the cells with a demethylating agent, 5-deoxyazacytidine. The treatment resulted also in the expression of SHP-1 mRNA and, less frequently, SHP-1 protein. The expression of SHP-1 protein was associated with dephosphorylation of the Jak3 kinase. These results show that lack of SHP-1 expression is frequent in malignant T cells and results from methylation of the SHP-1 gene promoter. Furthermore, they indicate that SHP-1 loss may play a role in the pathogenesis of T cell lymphomas by permitting persistence of signals generated by IL-2R and, possibly, other receptor complexes.

Biological significance of the expression of HIV-related chemokine coreceptors (CCR5 and CXCR4) and their ligands by human hematopoietic cell lines

The aim of this study was to learn more about the role of the HIV-related chemokine-chemokine receptor axes in human hematopoiesis. To address this issue we phenotyped 35 selected hematopoietic cell lines for the expression of CD4, CXCR4 and CCR5. We next evaluated the functionality of these chemokine receptors by calcium flux and chemotaxis assays, and by the ability of SDF-1, MIP-1alpha, MIP-1beta and RANTES to influence the growth of the cells expressing CXCR4 and/or CCR5. Lastly, we examined whether human hematopoietic cell lines may secrete some HIV-related chemokines, and whether endogenously secreted chemokines might interfere with the infectability. of hematopoietic cells by X4 and R5 HIV strains. These results demonstrate that: (1) HIV-related receptors are widely expressed on human hematopoietic cell lines; (2) stimulation of CXCR4 by SDF-1 induces calcium flux and chemotaxis in several hematopoietic cell lines more efficiently than stimulation of CCR5 by receptor-specific beta-chemokines; (3) chemokines do not regulate proliferation of the hematopoietic cells; and finally (4) infectability of the hematopoietic cells by HIV-1 may be auto-modulated by endogenously secreted chemokines. These data shed more light on the role of HIV-related chemokine-chemokine receptors axes in human hematopoiesis and interaction of hematopoietic cells with HIV.

Expression, regulation and function of AC133, a putative cell surface marker of primitive human haematopoietic cells

To explore the physiological significance of AC133 expression on human haematopoietic cells, we phenotyped normal and malignant human haematopoietic cells for AC133 expression, evaluated the utility of AC133 for isolating human stem/progenitor cells in comparison to other known early haematopoietic cell markers, investigated the role of AC133 in regulating hematopoiesis, and evaluated the possibility that MYB might regulate AC133. We found that while human CD34+ progenitor cells expressed AC133, expression was rapidly downregulated during differentiation. In apparent contrast, AC133 mRNA was detectable in cells isolated from CFU-Mix, BFU-E, CFU-GM and CFU-Meg colonies. Human cord blood CD34+ cells expressed AC133 at higher levels than their normal bone marrow counterparts. In apparent contrast to normal primitive haematopoietic cells, the AC133 protein was undetectable on cells from 24 different human haematopoietic cells lines, even though the majority of these cells expressed AC133 mRNA. Since CD34, AC133 and the c-kit (KIT) receptor are all co-expressed on human stem/progenitor cells, we compared the ability of monoclonal antibodies directed against each of these proteins to isolate early progenitor cells. Using these antibodies and magnetized particles in a standard immunoaffinity isolation protocol, we found that anti-CD34 and anti-KIT MoAbs could isolate > 80-90% of the clonogeneic cell population present in a given marrow sample. Anti-AC133 MoAbs recovered approximately 75-80% of CFU-GM and CFU-Meg, but only about 30% of CFU-Mix and BFU-E. Perturbation of AC133 expression with antisense oligodeoxynucleotides (AS ODN) resulted in transient downregulation of AC133 protein on human CD34+ cells but no apparent effect on cell survival or cloning efficiency ex vivo. Finally, downregulation of MYB expression with AS ODN had no effect on the AC133 expression at either the mRNA or protein level. Based on these results, we conclude that AC133 offers no distinct advantage over CD34 or c-kit as a target for immunoaffinity based isolation of primitive hematopoietic cells, that AC133 expression is not required for normal hematopoietic progenitor cell development in vitro, and finally that AC133 expression may not be MYB-dependent.

Soluble interleukin-2 receptor concentration as a biochemical indicator for acute graft-versus-host disease after allogeneic bone marrow transplantation

When interleukin-2 (IL-2) binds to the IL-2 receptor (IL2-R) on activated T cells, a soluble portion of the receptor (sIL2-R) is released. After allogeneic bone marrow transplantation (BMT), the serum concentration of sIL2-R may, therefore, be a useful surrogate marker for T cell activation that results in acute graft-versus-host disease (aGVHD). To determine if the sIL2-R concentration is a useful marker to help establish a diagnosis of aGVHD, serial sIL2-R concentrations were measured weekly for 4 weeks in 43 patients after allogeneic BMT. Grafts were from HLA-matched siblings (n = 33), 5/6 HLA-matched siblings (n = 3) or matched unrelated donors (n = 7). GVHD prophylaxis included cyclosporine A (CSA)/methotrexate (MTX) (n = 25), solumedrol/CSA (n = 15), or T cell depletion (n = 3). Twenty-three patients developed aGVHD (Grade I, 7; Grade II, 12; Grade III, 4) a median of 28 days after transplant. There was a significant association between a clinical diagnosis of aGVHD and an increase in the sIL2-R concentration (p < 0.001). The mean percent increase (+/-SE) over baseline for patients with a clinical diagnosis of aGVHD was 294% (+/-57%) by week 2 (n = 12), 431% (+/-116%) by week 3 (n = 14), and 650% (+/-315%) by week 4 (n = 9) after BMT. For each 100% increase over baseline, the likelihood of having aGVHD increased by 18%. Six of 20 patients without aGVHD became critically ill and exhibited marked increases in sIL2-R concentrations, similar to patients with a clinical diagnosis of aGVHD who never became critically ill. Fourteen patients without aGVHD who did not become critically ill exhibited negligible increases of sIL2-R in 2- to 4-week period after BMT. These data suggest that serial measurements sIL2-R concentration are helpful in establishing the diagnosis of aGVHD, but are not useful in the most acutely ill patients.

The immunosuppressive macrolide RAD inhibits growth of human Epstein-Barr virus-transformed B lymphocytes in vitro and in vivo: A potential approach to prevention and treatment of posttransplant lymphoproliferative disorders

Whereas the standard immunosuppressive agents foster development of posttransplant lymphoproliferative disorders (PTLDs), the impact of RAD, a macrolide with potent immunosuppressive properties, and other immunosuppressive macrolides on these disorders remains undetermined. We found that RAD had a profound inhibitory effect on in vitro growth of six different PTLD-like Epstein-Barr virus+ lymphoblastoid B cell lines. Similar to normal T cells, RAD blocked cell-cycle progression in PTLD-like B cells in the early (G(0)/G(1)) phase. Furthermore, RAD increased the apoptotic rate in such cells. The drug also had a profound inhibitory effect on the growth of PTLD-like Epstein-Barr virus+ B cells xenotransplanted s.c. into SCID mice. The degree of the RAD effect varied among the three B cell lines tested and was proportional to its effects on the cell lines in vitro. In this in vivo xenotransplant model, RAD markedly delayed growth or induced regression of the established tumors. In one line, it was able to eradicate the tumor in four of eight mice. When RAD treatment was initiated before tumor cell injection, a marked inhibition of tumor growth was seen in all three lines. In two of them, the drug prevented tumor establishment in approximately 50% of mice (5/11 and 5/8). In summary, RAD is a potent inhibitor of PTLD-like cells in vitro and in vivo. These findings indicate that, in contrast to the standard immunosuppressive agents, macrolides such as RAD may be effective in prevention and treatment of PTLDs.

Hepatosplenic gamma-delta T-cell lymphoma as a late-onset posttransplant lymphoproliferative disorder in renal transplant recipients

We report 2 cases of renal transplant recipients in whom hepatosplenic gamma-delta T-cell lymphoma (gamma-delta HSTCL) developed 5 and 10 years after transplantation. Both patients had marked hepatosplenomegaly, B symptoms (weight loss, fever, and night sweats), and abnormal peripheral blood findings, including anemia in both, thrombocytopenia and leukoerythroblastic changes in 1, and leukocytosis in the other. Markedly atypical lymphoid infiltrate of intermediate to large cells was observed in the spleen, liver, and bone marrow. The malignant cells showed typical immunophenotype of gamma-delta T cells (CD2+, CD3+, CD4-, CD8-, CD7+, gamma-delta T-cell receptor-positive, and alpha-beta T-cell receptor-negative) with clonal T-cell receptor gene rearrangement and were of the V-delta-1 subset. In addition, the cells contained a cytolytic granule-associated protein, TIA-1, and Fas ligand, indicating cytotoxic T-cell differentiation. The malignant T cells in both cases were of host tissue origin. Both cases were negative for Epstein-Barr virus genome using Southern blot analysis. The patients did not respond to reduction of immunosuppression. Despite initial response to chemotherapy, both patients died within 6 months of diagnosis. Our findings indicate that gamma-delta HSTCL can occur as a late complication in transplant recipients.

Evidence for early hematopoietic progenitor cell involvement in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) represents a subtype of acute myeloid leukemia with characteristic morphologic, molecular, and immunophenotypic features. Previous immunophenotypic analyses have shown that leukemic cells in APL typically express the myeloid markers CD33 and CD13 but lack expression of the early hematopoietic progenitor cell antigens CD34 and HLA-DR. We analyzed selected immunophenotypic features of APL by flow cytometry and showed that 7 (41%) of 17 cases contained significant subsets of CD34+ leukemic cells: CD34+ myeloid cells predominated in 2 APL cases. By using a fluorescence-activated cell sorter-fluorescence in situ hybridization approach, we confirmed that the CD34+ cells harbored the t(15;17) translocation characteristic of APL. By using the same experimental approach, CD34+ populations were stratified into primitive CD34+ CD38- and committed CD34+ CD38+ progenitor cell subpopulations; cells in both subsets contained the t(15;17) translocation. The knowledge that APL may be partly or largely CD34+ is important for proper diagnosis. Furthermore, identification of the t(15;17) translocation in CD34+ CD38- blasts indicates that, in at least some cases, the leukemogenic mutation in APL occurs within primitive hematopoietic progenitor cells.

Signal transducer and activator of transcription (STAT)5 activation by BCR/ABL is dependent on intact Src homology (SH)3 and SH2 domains of BCR/ABL and is required for leukemogenesis

Signal transducer and activator of transcription (STAT)5 is constitutively activated in BCR/ ABL-expressing cells, but the mechanisms and functional consequences of such activation are unknown. We show here that BCR/ABL induces phosphorylation and activation of STAT5 by a mechanism that requires the BCR/ABL Src homology (SH)2 domain and the proline-rich binding site of the SH3 domain. Upon expression in 32Dcl3 growth factor-dependent myeloid precursor cells, STAT5 activation-deficient BCR/ABL SH3+SH2 domain mutants functioned as tyrosine kinase and activated Ras, but failed to protect from apoptosis induced by withdrawal of interleukin 3 and/or serum and did not induce leukemia in severe combined immunodeficiency mice. In complementation assays, expression of a dominant-active STAT5B mutant (STAT5B-DAM), but not wild-type STAT5B (STAT5B-WT), in 32Dcl3 cells transfected with STAT5 activation-deficient BCR/ABL SH3+SH2 mutants restored protection from apoptosis, stimulated growth factor-independent cell cycle progression, and rescued the leukemogenic potential in mice. Moreover, expression of a dominant-negative STAT5B mutant (STAT5B-DNM) in 32Dcl3 cells transfected with wild-type BCR/ABL inhibited apoptosis resistance, growth factor-independent proliferation, and the leukemogenic potential of these cells. In retrovirally infected mouse bone marrow cells, expression of STAT5B-DNM inhibited BCR/ABL-dependent transformation. Moreover, STAT5B-DAM, but not STAT5B-WT, markedly enhanced the ability of STAT5 activation-defective BCR/ABL SH3+SH2 mutants to induce growth factor-independent colony formation of primary mouse bone marrow progenitor cells. However, STAT5B-DAM did not rescue the growth factor-independent colony formation of kinase-deficient K1172R BCR/ABL or the triple mutant Y177F+R522L+ Y793F BCR/ABL, both of which also fail to activate STAT5. Together, these data demonstrate that STAT5 activation by BCR/ABL is dependent on signaling from more than one domain and document the important role of STAT5-regulated pathways in BCR/ABL leukemogenesis.

Differences in phosphorylation of the IL-2R associated JAK/STAT proteins between HTLV-I(+), IL-2-independent and IL-2-dependent cell lines and uncultured leukemic cells from patients with adult T-cell lymphoma/leukemia

To determine activation status of the IL-2R-associated (Jak/STAT) pathway in the HTLV-I infected cells, we examined tyrosine phosphorylation of Jak3, STAT3, and STAT5 in several HTLV-I(+) T-cell lines and in uncultured leukemic T cells isolated from patients with adult T-cell lymphoma/leukemia (ATLL). Constitutive basal phosphorylation of Jak3 and, usually, STAT3 and STAT5 was detected in all four IL-2-independent cell lines tested, but in none of the three IL-2-dependent cell lines. Similarly, there was no detectable basal phosphorylation of Jak3 and STAT5 in the leukemic cells from ATLL patients (0/8 and 0/3, respectively). However, stimulation with IL-2 resulted in Jak3 and STAT5 phosphorylation in both leukemic ATLL cells and IL-2-dependent lines. Furthermore, expression of SHP-1 phosphatase which is a negative regulator of cytokine receptor signaling, was lost in most IL-2 independent cell lines (3/4) but not in the leukemic ATLL cells (0/3). Finally, the HTLV-I(+) T-cell lines (313) but not the control, HTLV-I(-) T-cell lines were resistant to rapamycin and its novel analog RAD. We conclude that (1) HTLV-I infection per se does not result in a constitutive phosphorylation of the Jak3, STAT3, and STAT5 proteins; (2) malignant transformation in at least some cases of ATLL does not require the constitutive, but may require IL-2-induced, activation of the IL-2R Jak/STAT pathway; and (3) there are major differences in T-cell immortalization mechanism(s) which appear to involve SHP-1 and target molecules for rapamycin and RAD.

The usefulness of CD64, other monocyte-associated antigens, and CD45 gating in the subclassification of acute myeloid leukemias with monocytic differentiation

Immunophenotyping by flow cytometry is widely used in the diagnosis and subclassification of acute myeloid leukemia (AML). CD14 is the monocyte-associated antigen most widely used to identify AML with monocytic differentiation (French-American-British classes M4 and M5); however, we observed that CD14 expression is frequently diminished or absent in such cases. To identify monocyte-associated antigens that might improve recognition of AML M4 and M5, we used 3-color flow cytometry and a panel of antibodies reported to distinguish cells of monocytic lineage in 44 cases of AML. In addition, CD45 vs logarithmic side scatter plots were analyzed in all cases. As expected, CD14 was highly specific but was only moderately sensitive for monocytic differentiation. CD64 had the best-combined sensitivity and specificity for AML M4 and M5. CD45 vs logarithmic side scatter analysis showed a higher percentage of monocytes in AML M4 and M5 compared with nonmonocytic AML. CD64 was expressed in 5 of 5 cases of acute promyelocytic leukemia (AML M3), but the intensity of staining was significantly less in AML M3 than in AML M4 and M5. Our findings show that addition of CD64 and CD45 vs logarithmic side scatter analysis to CD14 greatly improves flow cytometric detection of AML with monocytic differentiation and that CD64, also expressed in AML M3, may help distinguish AML M3 from other subtypes.

Subcutaneous panniculitis-like T-cell lymphoma: clinicopathologic, immunophenotypic, and genotypic analysis of alpha/beta and gamma/delta subtypes

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is an uncommon cutaneous lymphoma that has been proposed as a distinct clinicopathologic entity, but studies of SPTCL are limited. We studied the clinicopathologic, immunophenotypic, and genetic features of 11 SPTCLs. All cases had a variable admixture of pleomorphic small, medium, or large lymphocytes and histiocytes infiltrating the subcutis in a lobular panniculitis-like pattern. A granulomatous reaction was seen in three cases and erythrophagocytosis in four. Karyorrhexis and fat necrosis were present in all cases. Angioinvasion was seen in seven SPTCLs; four had areas of coagulation necrosis. All cases expressed T-cell-associated antigens (CD3epsilon, CD45RO, or CD43) and T-cell receptors (TCR); nine expressed alphabeta TCRs and two expressed gammadelta TCRs. T-cell receptor-gamma, TCRbeta, or TCRdelta genes were clonally rearranged in 8 of 10 cases studied. Both gammadelta SPTCLs expressed Vdelta2+ TCRs and were CD4-, CD8- and CD56+. CD56 was negative in seven of nine alphabeta SPTCLs and inconclusive in the other two. Six of nine alphabeta SPTCLs were CD8+; the CD4/CD8 phenotypes were indeterminate in the other three. Cytolytic granule-associated proteins were expressed by all SPTCLs (11 of 11 were TIA-1+, 4 of 4 were perforin+). In situ hybridization for Epstein-Barr virus-encoded RNA (EBER-1) was negative in all cases. Most patients responded to systemic chemotherapy or local radiation therapy. Seven patients are alive: four without disease (19-73 months) and three with disease (32-72 months); four died: three of disease (3-25 months) and one without disease (42 months). We conclude that SPTCLs are clonal, EBV-, cytotoxic T-cell lymphomas derived from alphabeta T-cells or gammadelta T-cells. The gammadelta SPTCLs appear to be preferentially derived from the Vdelta2+ subset. Subcutaneous panniculitis-like T-cell lymphoma may be rapidly fatal or indolent; local therapy may be appropriate for some patients.

Expression of constitutively active Raf-1 in the mitochondria restores antiapoptotic and leukemogenic potential of a transformation-deficient BCR/ABL mutant

The oncogenic BCR/ABL protein protects hematopoietic cells from apoptosis induced by growth factor deprivation, but the mechanisms are only partially understood. A BCR/ABL mutant lacking amino acids 176-426 in the BCR domain (p185DeltaBCR) failed to protect interleukin 3-deprived 32Dcl3 myeloid precursor cells from apoptosis, although it possessed tyrosine kinase activity and was capable of activating the Ras-Raf-MAP kinase pathway. Compared to p185 wild-type transfectants, p185DeltaBCR-transfected cells showed markedly reduced levels of Bcl-2 and expressed the hypophosphorylated, proapoptotic form of BAD. Bcl-2 expression in the mitochondrial fraction of p185DeltaBCR cells was also markedly diminished and mitochondrial RAF was undetectable. In p185DeltaBCR cells transfected with a mitochondria-targeted, constitutively active RAF (M-Raf) BAD was expressed in the hyperphosphorylated form and released from the mitochondria into the cytosol. p185DeltaBCR/M-Raf-transfected cells were completely resistant to apoptosis induced by growth factor deprivation in vitro. Moreover, constitutive expression of dominant-negative M-Raf (K375W) enhanced the susceptibility of 32Dcl3 cells expressing wild-type BCR/ABL to apoptosis. In severe combined immunodeficiency (SCID) mice, p185DeltaBCR/M-Raf double transfectants were leukemogenic, whereas cells expressing only p185DeltaBCR showed no leukemogenic potential. Together, these data support the existence of a BCR/ABL-dependent pathway that leads to expression of an active RAF in the mitochondria and promotes antiapoptotic and leukemia-inducing effects of BCR/ABL.

Abnormal myelocytic cell development in interleukin-2 (IL-2)-deficient mice: evidence for the involvement of IL-2 in myelopoiesis

Mice lacking interleukin-2 (IL-2) developed a severe hematopoietic disorder characterized by the abnormal development of myeloid cells and neutropenia. Analysis of the bone marrow of IL-2-deficient (IL-2(-/-)) mice showed that the number of mature polymorphonuclear cells was decreased by 65% to 75%, and granulocyte/macrophage precursor cells were reduced by 50%. Bone marrow cells from IL-2(-/-) mice were unable to sustain myelopoiesis in lethally irradiated mice and in long-term bone marrow cultures (LTBMC). The addition of exogenous IL-2 to LTBMC of IL-2(-/-) cells partially restored hematopoietic progenitor activity. In the bone marrow of wild-type mice, immature (Mac-1(lo)) myeloid cells, including myeloblasts and promyelocytes, constitutively expressed the beta-chain of the IL-2R, and the number of Mac-1(lo)IL-2Rbeta+ cells was increased by twofold to threefold in IL-2(-/-) mice. During culture in the presence of IL-2 and the absence of stromal cells, Mac-1(lo)IL-2Rbeta+ immature myeloid cells proliferated and gave rise to mature granulocytes and macrophages. Collectively, these observations indicate that defective myelopoiesis in IL-2(-/-) mice is at least in part a consequence of their direct dependency on IL-2, and by regulating the growth of immature myeloid cells, IL-2 plays an important role in the homeostatic regulation of myelocytic cell generation.

The role of insulin (INS) and insulin-like growth factor-I (IGF-I) in regulating human erythropoiesis. Studies in vitro under serum-free conditions--comparison to other cytokines and growth factors

The role of insulin (INS), and insulin-like growth factor-I (IGF-I) in the regulation of human erythropoiesis is not completely understood. To address this issue we employed several complementary strategies including: serum free cloning of CD34+ cells, RT-PCR, FACS analysis, and mRNA perturbation with oligodeoxynucleotides (ODN). In a serum-free culture model, both INS and IGF-I enhanced survival of CD34+ cells, but neither of these growth factors stimulated their proliferation. The influence of INS and IGF-I on erythroid colony development was dependent on a combination of growth factors used for stimulating BFU-E growth. When BFU-E growth was optimally stimulated with erythropoietin (EpO) + kit ligand (KL) the large erythroid colonies developed normally even in the absence of INS or IGF-I. However, the addition of both of these growth factors slightly enhanced colony size. On the other hand, if erythroid colonies were stimulated suboptimally with EpO + IL-3 only, INS or IGF-I increased the number of small erythroid bursts by approximately 30%. Both INS and IGF-I activated signal transduction in maturing human erythropoietic cells as determined by phosphorylation of the insulin receptor substrate-2 (IRS-2) protein. We also found by RT-PCR that mRNA coding for INS-R is expressed in FACS sorted CD34+, c-kit-R+ marrow cells, and in cells isolated from BFU-E and CFU-GM colonies. Expression of INS-R protein on these cells was subsequently confirmed by cytofluorometry. In contrast, the receptor for insulin-like growth factor-I (IGF-IR) was not detected on CD34+ cells, and was first easily detectable on more differentiated cells derived from day 6 BFU-E and CFU-GM colonies. We conclude that INS and IGF-I may be survival factors for human CD34+ cells, but are not required during early erythropoiesis. In contrast, both growth factors may play some role at the final stages of erythroid maturation.

Use of serum soluble interleukin-2 receptor levels to monitor the progression of cutaneous T-cell lymphoma

BACKGROUND

The serum concentration of soluble alpha chain of the interleukin-2 receptor (sIL-2R) correlates with tumor burden in cutaneous T-cell lymphoma (CTCL). Therefore the sIL-2R level may be useful to monitor the condition of patients treated with extracorporeal photopheresis or other treatments.

OBJECTIVE

Our goal was to determine the utility of serum sIL-2R as a test in monitoring of patients with advanced CTCL.

METHODS

Serum sIL-2R was measured serially in 36 patients with advanced CTCL treated with extracorporeal photopheresis and other modalities (interferon alfa, methotrexate, topical nitrogen mustard, electron beam).

RESULTS

Serum concentrations of sIL-2R as well as lactate dehydrogenase (LDH) correlated strongly with lymph node size, but only sIL-2R correlated significantly with the severity of skin manifestations in erythrodermic patients. In addition, serum sIL-2R, but not LDH, was significantly higher in patients with nodal involvement. The level of sIL-2R also was significantly higher in patients with large-cell transformation in the skin or lymph nodes compared with patients without transformed disease. During treatment, serum concentrations of both serum sIL-2R and LDH correlated with changes in clinical status, but only sIL-2R showed statistically significant differences in mean levels for different relative global response scores. Pretreatment levels of both sIL-2R and LDH correlated significantly with survival, but only sIL-2R retained significance when both were entered into the Cox proportionate hazards model.

CONCLUSION

The concentration of serum sIL-2R correlates well with disease status and is more useful than LDH or Sézary cell counts to monitor clinical change in patients with advanced CTCL. Moreover, our data suggest that sIL-2R is produced at a relatively low rate by tissue-based lymphoma cells, and that large-cell transformation in CTCL results in marked increase in sIL-2R production in some patients.

Suppression of proliferation and phosphorylation of Jak3 and STAT5 in malignant T-cell lymphoma cells by derivatives of octylamino-undecyl-dimethylxanthine

IL-2R signal transduction involves tyrosine phosphorylation of several proteins including Jak3 and STAT5. In the present study we examined the effect of two octylamino-undecyl-dimethylxanthine (OUDMX) derivatives, designated CT2576 and CT5589, on proliferation and protein tyrosine phosphorylation in human malignant T-cell lymphoma lines. These T-cell lines (PB-1, 2A, and 2B), obtained from a progressive T-cell lymphoma involving skin, are IL-2 independent but have constitutively activated IL-2R-associated signal transduction pathway common to IL-2 and several other cytokines: IL-4, IL-7, IL-9, and IL-15. CT2576, characterized previously on the functional level as an inhibitor of IL-2 signaling and, on the biochemical level, as an inhibitor of phosphatidic acid biosynthesis, suppressed completely growth of the malignant T cell lymphoma lines. CT5589 which is a novel analog of the CT2576, displayed a similar, although weaker, effect. Furthermore, both CT compounds inhibited constitutive tyrosine phosphorylation of two proteins: Jak3 and STAT5 which are key downstream elements in the signal transduction pathway activated by IL-2 and the other cytokines. The CT compounds inhibited also Jak3 phosphorylation induced by IL-2 in the IL-2 dependent SZ-4 cells. Inhibition of phosphorylation by CT2576 and CT5589 was only partially selective since phosphorylation of several other proteins was also affected. Phosphorylation of many others was, however, unaffected. These findings demonstrate that the OUDMX derivatives suppress proliferation of malignant T lymphocytes. Furthermore, they suggest that this suppression may be mediated by inhibition of the IL-2R-associated Jak/STAT signaling pathway. A potential role for OUDMX derivatives in therapy of human T-cell lymphoma should be further explored.

Lymphoid hyperplasia, autoimmunity, and compromised intestinal intraepithelial lymphocyte development in colitis-free gnotobiotic IL-2-deficient mice

IL-2-deficient (IL-2(-/-)) mice develop disorders of the hemopoietic and immune systems characterized by anemia, lymphocytic hyperplasia, and colitis. The mechanisms responsible for these abnormalities remain unclear. To investigate the underlying basis of autoimmunity, the particular role of commensal gut flora in the initiation of colitis, and the role of IL-2 in the development of intestinal intraepithelial lymphocytes (iIEL), we evaluated IL-2(-/-) mice reared and maintained under gnotobiotic (germfree) conditions. By 8 wk of age, 80% (20 of 25) of germfree IL-2(-/-) mice show signs of disease, including anemia, disturbances in bone marrow hemopoietic cells, lymphocytic hyperplasia, and generalized autoimmunity, similar to those seen in specific pathogen-free (SPF) IL-2(-/-) mice. In striking contrast to SPF IL-2(-/-) mice, germfree IL-2(-/-) mice do not develop colitis. However, the numbers of gammadelta+ and TCR alphabeta+ CD8 alphaalpha+ iIELs are reduced, and in lethally irradiated SPF IL-2(+/+) mice, reconstituted with IL-2(-/-) bone marrow TCR gammadelta+ iIELs fail to develop, consistent with an important role of IL-2/IL-2R signaling in the development of gammadelta iIELs. Consequently, our findings demonstrate that the colitis seen in SPF IL-2(-/-) mice depends upon the presence of intestinal bacterial flora and that environmental Ags are not responsible for the anemia and extraintestinal lymphoid hyperplasia that occur in IL-2(-/-) mice. Thus, germfree IL-2(-/-) mice represent a unique system in which the role of IL-2 deficiency in hemopoietic and immune system disorders can be investigated in dissociation from complications that may arise due to colitis.

Transformation of hematopoietic cells by BCR/ABL requires activation of a PI-3k/Akt-dependent pathway

The BCR/ABL oncogenic tyrosine kinase activates phosphatidylinositol 3-kinase (PI-3k) by a mechanism that requires binding of BCR/ABL to p85, the regulatory subunit of PI-3k, and an intact BCR/ABL SH2 domain. SH2 domain BCR/ABL mutants deficient in PI-3k activation failed to stimulate Akt kinase, a recently identified PI-3k downstream effector with oncogenic potential, but did activate p21 RAS and p70 S6 kinase. The PI-3k/Akt pathway is essential for BCR/ABL leukemogenesis as indicated by experiments demonstrating that wortmannin, a PI-3k specific inhibitor at low concentrations, suppressed BCR/ABL-dependent colony formation of murine marrow cells, and that a kinase-deficient Akt mutant with dominant-negative activity inhibited BCR/ABL-dependent transformation of murine bone marrow cells in vitro and suppressed leukemia development in SCID mice. In complementation assays using mouse marrow progenitor cells, the ability of transformation-defective SH2 domain BCR/ABL mutants to induce growth factor-independent colony formation and leukemia in SCID mice was markedly enhanced by expression of constitutively active Akt. In retrovirally infected mouse marrow cells, the BCR/ABL mutant lacking the SH2 domain was unable to upregulate the expression of c-Myc and Bcl-2; in contrast, expression of a constitutively active Akt mutant induced Bcl-2 and c-Myc expression, and stimulated the transcription activation function of c-Myc. Together, these data demonstrate the requirement for the BCR/ABL SH2 domain in PI-3k activation and document the essential role of the PI-3k/Akt pathway in BCR/ABL leukemogenesis.

Histiocytic necrotizing lymphadenitis (Kikuchi's disease): in situ end-labeling, immunohistochemical, and serologic evidence supporting cytotoxic lymphocyte-mediated apoptotic cell death

Histiocytic necrotizing lymphadenitis (Kikuchi's disease) is a benign, self-limited disorder that is sometimes confused with malignant lymphoma. Kikuchi's disease is characterized by collections of histiocytes and lymphocytes surrounding areas of necrosis containing fragments of karyorrhectic nuclear debris. Polymorphonuclear leukocytes are generally absent. The mechanism of cell death involved has not been extensively studied, and a definitive etiology has not been identified. Recent articles proposed that the mechanism of cell death is more characteristic of coagulative necrosis than apoptosis, but, to our knowledge, this has not been studied with the use of currently available assays of apoptosis. To study the mechanism of cell death in Kikuchi's disease, we employed an in situ end-labeling technique on formalin-fixed, paraffin-embedded sections of lymph nodes with Kikuchi's disease. These studies demonstrated that the lymphocytes and histiocytes within and surrounding the areas of necrosis showed nuclear DNA fragmentation, a feature characteristic of early apoptosis. Immunohistochemical studies revealed an increase in CD8(+)-T lymphocytes and lymphocytes containing TIA-1, a cytotoxic granule-associated protein, within foci of cellular debris, with a relative paucity of CD56+ cells. Moreover, TIA-1-positive granules were present within the cytoplasm of many apoptotic bodies. In one of the patients for whom acute phase serum was available, evaluation by enzyme-linked immunosorbent assay demonstrated that the serum concentrations of the T-cell activating cytokines interleukin-2 and interleukin-6 were increased; no such increase was noted in eight patients with other lymphoproliferative disorders. In contrast, the serum concentrations of the immunosuppressive molecules interleukin-10, soluble interleukin-2 receptor, and soluble tumor necrosis factor receptor were expressed at normal levels in the patient with Kikuchi's disease. These findings suggested that the predominate mechanism of cellular destruction in Kikuchi's disease was apoptosis mediated by cytolytic lymphocytes. These data supported the prevailing hypothesis of a viral or autoimmune pathogenesis in Kikuchi's disease.

Blastic transformation of p53-deficient bone marrow cells by p210bcr/abl tyrosine kinase

Blastic transformation of chronic myelogenous leukemia (CML) is characterized by the presence of nonrandom, secondary genetic abnormalities in the majority of Philadelphia1 clones, and loss of p53 tumor suppressor gene function is a consistent finding in 25-30% of CML blast crisis patients. To test whether the functional loss of p53 plays a direct role in the transition of chronic phase to blast crisis, bone marrow cells from p53+/+ or p53-/- mice were infected with a retrovirus carrying either the wild-type BCR/ABL or the inactive kinase-deficient mutant, and were assessed for colony-forming ability. Infection of p53-/- marrow cells with wild-type BCR/ABL, but not with the kinase-deficient mutant, enhanced formation of hematopoietic colonies and induced growth factor independence at high frequency, as compared with p53+/+ marrow cells. These effects were suppressed when p53-/- marrow cells were coinfected with BCR/ ABL and wild-type p53. p53-deficient BCR/ABL-infected marrow cells had a proliferative advantage, as reflected by an increase in the fraction of S+G2 phase cells and a decrease in the number of apoptotic cells. Immunophenotyping and morphological analysis revealed that BCR/ABL-positive p53-/- cells were much less differentiated than their BCR/ABL-positive p53+/+ counterparts. Injection of immunodeficient mice with BCR/ABL-positive p53-/- cells produced a transplantable, highly aggressive, poorly differentiated acute myelogenous leukemia. In marked contrast, the disease process in mice injected with BCR/ABL-positive p53+/+ marrow cells was characterized by cell infiltrates with a more differentiated phenotype and was significantly retarded, as indicated by a much longer survival of leukemic mice. Together, these findings directly demonstrate that loss of p53 function plays an important role in blast transformation in CML.

Analysis of IL-2, IL-4 and their receptors in clonally-related cell lines derived from a patient with a progressive cutaneous T-cell lymphoproliferative disorder

Three clonally related T-cell lymphoma lines (PB-1, 2A, and 2B) were examined for expression of IL-2, IL-4, and their receptors. All three lines were derived from a single patient who had an atypical, progressive T-cell lymphoproliferative disorder involving primarily skin (Davis, T.H. et al. 1992, N. Engl. J. Med. 326:1115). The PB-1 cell line was obtained from a relatively early, clinically indolent stage of the cutaneous lymphoma, whereas the 2A and 2B lines were established from a late, aggressive stage of the lymphoma. Reverse-transcriptase PCR performed with primer pairs specific for IL-2 and IL-4 showed that no mRNA coding for these cytokines was present in any of the lines with the exception of IL-4 mRNA in the 2A line. No IL-4 protein, however, was found in any of the cell lines including 2A by immunocytochemical staining with anti-IL-4 mAb. Accordingly, no bioactive IL-4 was present in the supernatants of these lines. In contrast, all three T-cell lymphoma lines contained mRNA for IL-2R alpha, IL-2R beta, IL-4R and common gamma chain. Immunocytochemical analysis revealed that only the PB-1 line stained strongly with mAbs specific for IL-2R alpha, IL-2R beta, and IL-4R whereas the 2A and 2B lines showed only limited staining with these mAbs. In contrast to expression of IL-2R alpha and IL-4R primarily on the cell surface, IL-2R beta was localized mainly in the cell cytoplasm. Testing supernatants of the cell lines by ELISA for the presence of soluble alpha chain of the IL-2R (sIL-2R) has shown that only PB-1 secreted a large amount of sIL-2R, whereas the 2A and 2B lines secreted lesser amounts. Furthermore, the PB-1 cells expressed a relatively large number of IL-4R as determined by IL-4 binding studies using an IL-4-alkaline phosphatase fusion protein. The remaining two lines displayed only limited binding of IL-4. Addition of IL-2 and/or IL-4 to the culture medium did not modulate growth of PB-1 and the other two lines. These findings may indicate that at least some types of T-cell lymphoma evolve from cells which lose the capacity to synthesize T-cell autocrine growth factors such as IL-2 and IL-4, and show progressive loss of receptors for these cytokines.

Activation of Jak/STAT proteins involved in signal transduction pathway mediated by receptor for interleukin 2 in malignant T lymphocytes derived from cutaneous anaplastic large T-cell lymphoma and Sezary syndrome

Signaling through the interleukin 2 receptor (IL-2R) involves phosphorylation of several proteins including Jak3, STAT5, and, in preactivated cells, STAT3. In the present study, we examined the functional status of the IL-2R-associated Jak/STAT pathway in malignant T lymphocytes from advanced skin-based lymphomas: anaplastic large T-cell lymphoma (ALCL) and Sezary syndrome (SzS). Proliferation of three ALCL cell lines (PB-1, 2A, and 2B) was partially inhibited by rapamycin, a blocker of some of the signals mediated by IL-2R, but not by cyclosporin A, FK-506, and prednisone, which suppress signals mediated by the T-cell receptor. All the cell lines expressed on their surface the high-affinity IL-2R (alpha, beta, and gamma c chains). They showed basal, constitutive phosphorylation, and coassociation of Jak3, STAT5, and STAT3. Weak basal phosphorylation of IL-2R gamma c was also detected. In regard to SzS, peripheral blood mononuclear cells from 10 of 14 patients showed basal phosphorylation of Jak3, accompanied by phosphorylation of STAT5 in 9 patients, and STAT3 in 4 patients. However, in vitro overnight culture of SzS cells without exogenous cytokines resulted in markedly decreased Jak3 and STAT5 phosphorylation, which could be reversed by stimulation with IL-2. This indicates that the basal phosphorylation of Jak3 and STAT5 in freshly isolated SzS cells is induced rather than constitutive. The basal activation of the Jak/STAT pathway involved in IL-2R signal transduction in ALCL and SzS cells reported here suggests that this pathway may play a role in the pathogenesis of cutaneous T-cell lymphomas, although the mechanism (induced versus constitutive) may vary between different lymphoma types.

Cutaneous CD56+ large T-cell lymphoma associated with high serum concentration of IL-2

We report the case of a patient with a clinically aggressive large cell lymphoma (LCL) which expressed several T-lymphocyte markers and, in addition, CD56 and, to a lesser degree, CD68 antigens. A marked increase in serum concentration of interleukin (IL)-2 was found (490 and 167 pg/0.1 mL in two serum samples collected 6 months apart). This increase in IL-2 appeared unique to this lymphoma because serum concentration of IL-2 was not increased in any of the cases of various types of cutaneous lymphoproliferative disorders tested: mycosis fungoides-related cutaneous T-cell lymphoma (CTCL: 28 patients), granulomatous slack-skin syndrome (GS-SS: 1 patient), anaplastic large cell lymphoma (ALCL: 2 patients), subcutaneous gamma/delta T-cell lymphoma (gamma/delta-TCL: 1 patient), adult-type leukemia/lymphoma (ATLL: 1 patient), and lymphomatoid papulosis (LyP: 4 patients). Furthermore, the increase in IL-2 serum concentration appeared selective in this CD56+ large-cell lymphoma-bearing patient, because concentration of none of the five other cytokines tested (IL-4, IL-6, IFNgamma, GM-CSF, and TNFalpha) was increased. In contrast, soluble receptors for IL-2 and two of the other cytokines (IL-6, and TNFalpha) were markedly increased not only in this patient, but also in most patients with the other cutaneous lymphoproliferative disorders that we examined except for lymphomatoid papulosis. These data indicate that increased IL-2 serum concentration may help to diagnose a unique type of cutaneous CD56(+) large (T-) cell lymphoma and suggest that IL-2 way play a role of an autocrine growth factor for this lymphoma.

Constitutive secretion of GM-CSF by three different cell lines derived from a single patient with a progressive cutaneous lymphoproliferative disorder

Three clonally related lymphoma lines (Mac-1, Mac-2A and Mac-2B) derived from progressive stages of CD30+ cutaneous T-cell lymphoma were found to constitutively secrete GM-CSF. The secretion of GM-CSF was identified by the ability of cell line supernatants to stimulate growth of megakaryoblastic cell line M-07e. This supernatant-mediated stimulation was inhibited by anti-GM-CSF MoAb (>98% inhibition for Mac-1 and Mac-2B lines, and >95% for Mac-2A line). Synthesis of GM-CSF was confirmed, at the mRNA level, by reverse transcriptase PCR and, at the protein level, by ELISA. Quantification of GM-CSF in supernatants by ELISA showed that the Mac-1 line, derived from an early, clinically indolent stage of the lymphoma, produced much more GM-CSF (>1600 pg/ml) than Mac-2A and Mac-2B lines which were derived from a late, aggressive stage (30-50 and 50-120 pg/ml, respectively). Lack of inhibition of cell growth by anti-GM-CSF MoAb as well as lack of response to exogenous GM-CSF of cells cultured at low concentration have demonstrated that GM-CSF does not act directly as a growth factor for these lines. ELISA studies showed that GM-CSF concentration in serum and urine of the patient were not elevated (<5 pg/ml). From several other cell lines tested (two primary CD30+ ALCL, 2 CD30- non-lymphoblastic T-cell lymphomas and 4HD), only two HD lines with a T-lymphocyte phenotype secreted detectable amounts of GM-CSF. Our data show that cells lines from a patient with cutaneous T-cell lymphoma constitutively secrete GM-CSF, although this capacity is relatively diminished in lines developed from more advanced disease.

Testicular extramedullary myeloid cell tumor in a patient with myelodysplastic syndrome

We report herein a case of extramedullary myeloid tumor arising bilaterally in the testes of a 66-year-old man, who had previously been diagnosed with myelodysplastic syndrome. Light microscopy of the testicular neoplasm demonstrated a tumor composed of large, slightly polygonal cells with pale blue to weakly eosinophilic cytoplasm. The tumor cells were immunoreactive for CD45, myeloperoxidase, lysozyme, CD43, and MB2. Many of the cells also expressed chloroacetate esterase. Peripheral blood and bone marrow findings were consistent with chronic myelomonocytic leukemia (FAB-CMML), particularly in the most recent material, which showed clear cellular dysplasia and an increase in the percentage of blasts in the bone marrow (15% to 20% of all nucleated cells). This case of extramedullary myeloid tumor is unusual in view of the patient's age and the testicular location. It emphasizes the importance of including extramedullary myeloid tumor in the differential diagnosis of histologically undifferentiated large-cell tumors, as well as a need to use a broad panel of immunohistochemical stains in such cases.

Increased serum concentration of the soluble interleukin-2 receptor in cutaneous T-cell lymphoma. Clinical and prognostic implications

BACKGROUND AND DESIGN

The serum concentration of soluble alpha-chain receptor for interleukin-2 (sIL-2R) was determined in 101 patients with cutaneous T-cell lymphoma (CTCL).

RESULTS

The serum concentration of sIL-2R correlates positively with CTCL tumor burden as determined by several clinical parameters (ie, clinical subtype of disease, extent of skin involvement, T rating, and stage), by serum lactate dehydrogenase concentration, and by Sézary cell counts in erythrodermic disease. The median value of sIL-2R in erythrodermic CTCL was more than threefold higher than that of classic mycosis fungoides (MF). The proportion of patients with elevated sIL-2R concentration (> 1000 U/mL) also increased in CTCL in a similar fashion according to the clinical type of disease (MF patch phase, 15%; MF plaque phase, 33%; MF tumor phase, 47%; and erythrodermic variants, 90%). However, no correlation was found between sIL-2R serum concentration and expression of membrane-bound IL-2R alpha chain (CD25) on lymphoid cells in skin lesions and peripheral blood. Significantly, multivariate analysis of various prognostic factors demonstrated that in erythrodermic CTCL, sIL-2R serum concentration correlated best with survival and was a better predictor of prognosis than stage, Sézary cell counts, or lactate dehydrogenase values.

CONCLUSIONS

These findings document the usefulness of the measurement of the sIL-2R serum concentration to determine tumor burden and prognosis in patients with CTCL.

Constitutive secretion of soluble interleukin-2 receptor by human T cell lymphoma xenografted into SCID mice. Correlation of tumor volume with concentration of tumor-derived soluble interleukin-2 receptor in body fluids of the host mice

Increased serum concentration of soluble alpha-chain receptor for interleukin-2 (sIL-2R) has been noted in patients with a variety of inflammatory conditions and lymphoid malignancies including T cell leukemia and lymphoma. Elevated sIL-2R serum levels seen in lymphoid malignancies appear to correlate with the clinical stage of disease. However, because sIL-2R is produced by normal activated lymphocytes, it has been uncertain whether serum sIL-2R in such conditions is derived from tumor cells or normal immune cells responding to the tumor. To address this question, we used a model of human (CD30+) anaplastic, large T cell lymphoma transplanted into immunodeficient SCID mice. Reverse transcription polymerase chain reaction of tumor RNA showed that the tumor, designated mJB6, contains mRNA for alpha-chain of human IL-2R. Furthermore, 15 to 25% of tumor cells stained with anti-human IL-2R alpha-chain mAb. Solid phase ELISA analysis of serum samples from mice bearing mJB6 lymphoma showed high concentrations of human sIL-2R. None of the control mice without lymphoma or with human nonlymphoid tumors (prostatic carcinoma, ovarian carcinoma, and glioblastoma multiforme) showed detectable human sIL-2R. The sIL-2R serum titers of mJB6-bearing mice correlated strongly with tumor volume (P < 0.0001). Tumors as small as 0.4 to 0.8 mm3 could be detected by this method. The sensitivity of sIL-2R ELISA exceeded at least 150 times the sensitivity of conventional radioisotopic tumor detection. Total resection of mJB6 tumors resulted in complete clearance of sIL-2R from the murine serum within 48 hours with a half-life of 6 hours. Accordingly, partial resection led to a significant decrease in sIL-2R followed by gradual increase with tumor regrowth. sIL-2R was also detected in the urine of mJB6-transplanted mice. As in serum, urine concentrations of sIL-2R were proportional to tumor mass (P < 0.02). Based on these findings we postulate that malignant cells are a major source of serum sIL-2R in patients with lymphoid tumors. In addition, our data further support monitoring sIL-2R concentration in body fluids as a sensitive method to detect change in tumor volume in such patients.

Preferential interaction of the CD4+29+/45RA-subset of human CD4+ T lymphocytes with an antibody against the cell-membrane ganglioside GD3

This study shows that the two major subpopulations of CD4+ T lymphocytes defined on the basis of differential expression of the CD29 and CD45RA antigens, show significant differences in reactivity with a monoclonal antibody against the GD3 ganglioside. Double staining studies showed that the GD3 ganglioside is predominantly expressed on cells from the CD4+29+/45RA subsets. The preferential interaction of the CD4+29+/45RA cell subset with the anti-GD3 MoAb was further confirmed by the proliferative and calcium-flux studies. Accordingly, the reciprocal, CD4+(29-)/45RA+ subset was unable to proliferate in response to the anti-GD3 MoAb alone. Although it did show a significant mobilization of calcium ions and proliferation to IL-2 when stimulated with the anti-GD3 MoAb, these response were much less pronounced than the responses of the CD4+29+/45RA- subset. Finally, when two T-cell stimulating monokines, IL-1 and IL-6, were tested for the ability to modulate the anti-GD3 mediated proliferation, only the former, but not the latter was able to enhance the proliferation. Although the natural ligand for the GD3 ganglioside remains unknown, the data presented here provide further evidence in support of the notion that the T-cell surface molecules different from the T-cell receptor MHC-antigen complex may contribute to the preferential activation of one of the CD4+ T lymphocyte subsets.

Differential effects of cytokines on proliferative response of human CD4+ T lymphocyte subsets stimulated via T cell receptor-CD3 complex

We report that the subsets of CD4+ T cells characterized by differential expression of CD45RA (2H4) Ag showed significant differences in proliferative response to immobilized anti-CD3 antibody (Ab) and cytokines: IL-1, IL-2, IL-4, and IL-6. Most strikingly, CD4+/45RA+ but not CD4+/45RA- T cells responded to anti-CD3 Ab and IL-4. Similar difference in response to IL-4 occurred when the subsets were stimulated by two "alternative" T cell activation pathways via CD2 and GD3 Ag. The response of CD4+/45RA+ cells to anti-CD3 Ab and IL-4 was enhanced by the two monokines: IL-1 and IL-6. Further differences between the subsets included the preferential response of the CD4+/45RA+ cells to enhancing effect of IL-6 on proliferation mediated by the anti-CD3 Ab and IL-2. In contrast to IL-6, IL-1 was unable to increase this proliferation significantly. In turn, the CD4+/45RA- cells responded preferentially to a weak stimulation mediated by anti-CD3 Ab either alone, or together with IL-1 and IL-6. Existence of these significant differences in the response of CD4+ T cell subsets costimulatory effects of the cytokines, suggests that the in vivo events resulting in an accumulation of the cytokines in particular combinations may lead to selective activation of one of the CD4+ T cell subsets during the immune response.

Differential effects of cytokines on proliferative response of human CD4+ T lymphocyte subsets stimulated via T cell receptor-CD3 complex

We report that the subsets of CD4+ T cells characterized by differential expression of CD45RA (2H4) Ag showed significant differences in proliferative response to immobilized anti-CD3 antibody (Ab) and cytokines: IL-1, IL-2, IL-4, and IL-6. Most strikingly, CD4+/45RA+ but not CD4+/45RA- T cells responded to anti-CD3 Ab and IL-4. Similar difference in response to IL-4 occurred when the subsets were stimulated by two "alternative" T cell activation pathways via CD2 and GD3 Ag. The response of CD4+/45RA+ cells to anti-CD3 Ab and IL-4 was enhanced by the two monokines: IL-1 and IL-6. Further differences between the subsets included the preferential response of the CD4+/45RA+ cells to enhancing effect of IL-6 on proliferation mediated by the anti-CD3 Ab and IL-2. In contrast to IL-6, IL-1 was unable to increase this proliferation significantly. In turn, the CD4+/45RA- cells responded preferentially to a weak stimulation mediated by anti-CD3 Ab either alone, or together with IL-1 and IL-6. Existence of these significant differences in the response of CD4+ T cell subsets costimulatory effects of the cytokines, suggests that the in vivo events resulting in an accumulation of the cytokines in particular combinations may lead to selective activation of one of the CD4+ T cell subsets during the immune response.

Induction of macrophage membrane interleukin 1 expression by T-cell dependent and T-cell independent pathways is inhibited by cyclosporin A

Here we report that cyclosporin A (CsA) inhibits the induction of membrane interleukin 1 (mIL-1) expression on murine peritoneal macrophages. The inhibition of mIL-1 expression was noted in response to both autoreactive T-cell lines specific for class I or class II MHC determinants as well as bacterial endotoxin. The macrophages were the direct target of this inhibition as shown by pretreating T cells and macrophages separately with CsA. The effective suppression by CsA of endotoxin-induced mIL-1 expression was dependent not only on the concentration of endotoxin employed, but also on the relative time of addition of CsA and endotoxin. Furthermore, CsA pretreatment of macrophages abrogated their ability to stimulate synthesis of IL-4 by a Th2 cell clone. These data suggest that inhibition of induction of accessory molecules such as mIL-1 may be a mechanism by which CsA abrogates the capacity of macrophages to present antigen.

Lymphokine-independent induction of macrophage membrane IL-1 by autoreactive T cells recognizing either class I or class II MHC determinants

Here we report that autoreactive T cell clones and T cell hybridomas that recognize class I or class II MHC determinants can induce IL-1 expression on cultured macrophages in an MHC-restricted manner. This genetic restriction of membrane IL-1 (mIL-1) induction is not absolute, however; it is manifest only in macrophages that have been cultured for several days before stimulation. Macrophages that are evaluated within 24 h after adherence display a basal level of mIL-1, and the T cell-induced augmentation of basal mIL-1 expression is not MHC-restricted. It appears that T cells of both Th1 and Th2 type have the capacity to induce mIL-1, suggesting that this function is not limited to the T cell subset (Th2) that is able to use IL-1. Most importantly, the ability of T cells to induce IL-1 on macrophages seems to occur by virtue of direct cellular interactions, and is independent of lymphokine secretion. The induction event is rapid enough (2 to 4 h) to allow T cells to interact with both antigen and IL-1 during the initial T cell/macrophage contact. These findings thus reveal an efficient mechanism for the induction of IL-1 during Ag presentation to T cells.