Proliferation Of Adult T-cell Leukemia Cells Research Articles

Inefficient Tax-Specific T-Cell Responses in Mice after Syngeneic Transplantation with tax-Transgenic Mouse-Derived Adult T-Cell Leukemia Cells.

Adult T-cell leukemia (ATL) is induced by chronic latent infection with human T-cell leukemia virus type 1 (HTLV-1). HTLV-1 Tax is an oncogenic factor that can be targeted by host T-cell responses. However, the expression of Tax in vivo is little in ATL cells and the impact of Tax-specific T-cell responses on ATL progression remains unclear. In the present study, we examined Tax-specific T-cell responses in C57BL/6 mice after syngeneic transplantation with tax-transgenic mouse-derived ATL (mATL) cells. We first confirmed that cellular tax cDNAs are mostly maintained and detectable in the spleen three weeks after mATL cell transplantation. However, mATL cell transplantation did not induce significant Tax-specific T-cell responses. Mice immunized with DNA and adenovirus vectors expressing Tax exhibited Tax-specific CD4+ T-cell responses but showed no enhancement of the responses or reduction in cellular tax cDNA levels after mATL cell transplantation. This study provides an animal model for analyzing the interaction between ATL cells and host immune responses as well as indicates the limited impact of Tax-specific T-cell responses on the proliferation of ATL cells.

153 Molecular pathogenesis by HTLV-1 bZIP factor

Human T-cell leukemia virus type 1 (HTLV-1) mainly transmits by cell-to-cell contact. Therefore, this virus induces proliferation of infected cells to facilitate transmission. In HTLV-1 infected individuals, infected cells proliferate in vivo. This proliferation of infected cells leads to the development of adult T-cell leukemia (ATL) and inflammatory diseases including HTLV-1 associated myelopathy (HAM). HTLV-1 bZIP factor (HBZ) is consistently expressed in ATL cells and HTLV-1 infected cells, and plays a critical role in their proliferation. Transgenic expression of HBZ causes T-cell lymphoma and inflammatory diseases, indicating that HBZ is critical for the pathogenesis of HTLV-1.We analyzed the function of HBZ and found that it possessed opposite functions to Tax in many pathways. We found that Tax could activate the classical Wnt pathway while HBZ inhibited it by interacting with TCF1/LEF1. The canonical Wnt pathway is activated in the thymus, and its transcription factors, TCF1/LEF1, suppressed the viral gene transcription by Tax. Conversely, the canonical Wnt pathway is suppressed in the peripheral T cells in which the non-canonical Wnt pathway is activated. HBZ enhanced the expression of Wnt5a, which is a ligand in non-canonical Wnt signaling. Knockdown of Wnt5a suppressed the proliferation and migration of ATL cells. Thus, activation of the non-canonical Wnt pathway by HBZ is linked with proliferation of ATL cells.These findings suggest that HTLV-1 is adapted to, not thymic T cells, but peripheral T cells. HBZ modulates the intracellular environment suitable for HTLV-1 replication and proliferation of infected cells.

4P-1090 cDNA microarray analysis of gene expression profile in tumor necrosis factor-α-stimulated human aortic endothelial cells

To examine the possibility that interleukin-9 (IL-9) may be involved in oncogenesis and the proliferation of adult T-cell leukemia (ATL) cells, we examined the expression of IL-9 mRNA and growth response to IL-9 in five human T-lymphotropic virus type-I (HTLV-I) infected T-cell lines and in primary leukemia cells in peripheral blood from eight patients with ATL (four acute ATL and four chronic). Four out of five cell lines expressed IL-9 mRNA not correlated with Tax expression. Primary ATL cells from all patients also expressed IL-9 mRNA not correlated with the clinical forms. Recombinant IL-9 showed growth enhancing activity in only one out of five cell lines and one out of eight patients' primary leukemic cells. These results suggest the infrequent involvement of IL-9 in the proliferation of ATL cells, both primary tumor cells and HTLV-I infected T-cell lines.

Interleukin-15 (IL-15) Can Replace the IL-2 Signal in IL-2–Dependent Adult T-Cell Leukemia (ATL) Cell Lines: Expression of IL-15 Receptor α on ATL Cells

Interleukin-15 receptor (IL-15R) and IL-2R have the same β and γ chains, but IL-15R has a specific α chain distinct from that of IL-2Rα, which is indispensable for the high affinity binding of IL-15. In the present study, we examined four IL-2-dependent adult T-cell leukemia (ATL) cell lines for their IL-15R expression. All cell lines bound IL-15, which was not inhibited by a 100-fold excess amount of IL-2, proliferated in response to IL-15 to the same degree as to the stimulation with IL-2, and were maintained without IL-2. The responses to 1L-15 were inhibited by the antibodies against IL-2R β or γ chains but was not by the IL-2R α chain antibody. [125I]–IL-15 exhibited a single high-affinity binding with an apparent kd of 0.17 nmol/L. Reverse transcription–coupled polymerase chain reaction (RT-PCR) showed that the cell lines had the mRNA of IL-15R α. The cell lines also had IL-15 mRNA. Despite the presence of IL-15 mRNA, the cell lines did not secrete IL-15, and the culture supernatants of fresh ATL cells and plasma from the patients did not contain a detectable amount of IL-15 with a few exceptional cases, although fresh ATL cells also responded to IL-15. These results suggest that ATL cells have the complete form of IL-15R and respond to IL-15. Such an IL-15–dependent cell proliferation mechanism might be used in the development of ATL and for the invasion and proliferation of ATL cells in the visceral organs.

Interleukin-15 (IL-15) Can Replace the IL-2 Signal in IL-2–Dependent Adult T-Cell Leukemia (ATL) Cell Lines: Expression of IL-15 Receptor α on ATL Cells

AbstractInterleukin-15 receptor (IL-15R) and IL-2R have the same β and γ chains, but IL-15R has a specific α chain distinct from that of IL-2Rα, which is indispensable for the high affinity binding of IL-15. In the present study, we examined four IL-2-dependent adult T-cell leukemia (ATL) cell lines for their IL-15R expression. All cell lines bound IL-15, which was not inhibited by a 100-fold excess amount of IL-2, proliferated in response to IL-15 to the same degree as to the stimulation with IL-2, and were maintained without IL-2. The responses to 1L-15 were inhibited by the antibodies against IL-2R β or γ chains but was not by the IL-2R α chain antibody. [125I]–IL-15 exhibited a single high-affinity binding with an apparent kd of 0.17 nmol/L. Reverse transcription–coupled polymerase chain reaction (RT-PCR) showed that the cell lines had the mRNA of IL-15R α. The cell lines also had IL-15 mRNA. Despite the presence of IL-15 mRNA, the cell lines did not secrete IL-15, and the culture supernatants of fresh ATL cells and plasma from the patients did not contain a detectable amount of IL-15 with a few exceptional cases, although fresh ATL cells also responded to IL-15. These results suggest that ATL cells have the complete form of IL-15R and respond to IL-15. Such an IL-15–dependent cell proliferation mechanism might be used in the development of ATL and for the invasion and proliferation of ATL cells in the visceral organs.

Frequent expression of interleukin-9 mRNA and infrequent involvement of interleukin-9 in proliferation of primary adult T-cell leukemia cells and HTLV-I infected T-cell lines

To examine the possibility that interleukin-9 (IL-9) may be involved in oncogenesis and the proliferation of adult T-cell leukemia (ATL) cells, we examined the expression of IL-9 mRNA and growth response to IL-9 in five human T-lymphotropic virus type-I (HTLV-I) infected T-cell lines and in primary leukemia cells in peripheral blood from eight patients with ATL (four acute ATL and four chronic). Four out of five cell lines expressed IL-9 mRNA not correlated with Tax expression. Primary ATL cells from all patients also expressed IL-9 mRNA not correlated with the clinical forms. Recombinant IL-9 showed growth enhancing activity in only one out of five cell lines and one out of eight patients' primary leukemic cells. These results suggest the infrequent involvement of IL-9 in the proliferation of ATL cells, both primary tumor cells and HTLV-I infected T-cell lines.

Interleukin‐4 induces proliferation of adult T‐cell leukemia cells

To evaluate the effect of IL-4 on the growth of leukemic cells from adult T-cell leukemia (ATL) patients (ATL cells) and determine whether the IL-4 autocrine mechanism is involved in the growth of ATL cells, we studied the proliferative response of ATL cells, from 11 patients, cultured in the presence or absence of IL-4 in vitro. Leukemic cells from 10 of the 11 patients examined proliferated in response to both IL-2 and IL-4 in a dose-dependent manner. The proliferative response to IL-4 was higher than that obtained with IL-2 in 8 patients. The expression of the IL-2 receptor (IL-2R) alpha alpha-chain in leukemic cells from some patients was also enhanced by IL-4. The IL-4 receptor was demonstrated by flow cytometry on the surface of ATL cells. Neither IL-4-induced proliferation of ATL cells nor IL-4-induced IL-2R expression on ATL cells was inhibited by anti-Tac or anti-IL-2 antibody and, therefore, these effects of IL-4 are considered independent of endogenous IL-2 activity. However, IL-2 and IL-4 were undetectable in the culture supernatants of ATL cells from any patient by enzyme-linked immunosorbent assay. Interferon-gamma (IFN-gamma) partially inhibited IL-2 or IL-4-induced proliferation of ATL cells. These results suggest that leukemic cells from ATL patients proliferate by an IL-2 or IL-4 paracrine mechanism in lymphoid tissue in vivo and that IFN-gamma inhibits IL-2- or IL-4-induced proliferation of ATL cells.

HTLV-ⅠおよびATL細胞に対する遺伝子組換え型インターフェロン α2, β, γ の抗ウイルスおよび抗腫瘍効果

ATL (Adult T cell leukemia) causes severe immune deficiency. Furthermore, aggravation of immune deficiency is a major problem in chemotherapy of ATL. In expectation of antiviral, antineoplastic and increasing immunological activity, several clinical trials of Interferons (IFNs) on ATL have been reported. However, as the effects have not been generally established, we investigated the in vitro effects of human recombinant interferon (rIFN) alpha 2, beta and gamma on both the infection of human T-cell lymphotropic virus type I (HTLV-I) to normal peripheral blood lymphocytes (PBL) and the growth of ATL cells. The induction of HTLV-I specific antigens on the surface of normal PBL cultured with HTLV-I in vitro was inhibited by the addition of rIFNs in a dose dependent manner. The rIFNs also had dose dependent suppressive effects on the proliferation of ATL cells and one of the ATL cell lines (MT-2). These suppressive effects of rIFNs were not due to a direct cytocidal activity, because rIFNs did not affect the viability of ATL cells at these concentrations. Such inhibitory concentrations (1 to 1000 U/ml) were within the ranges achievable in the blood of patients after the injection of rIFNs. This investigation suggests that rIFNs is applicable for the therapy of ATL.

Immunodeficiency in Preclinical Smoldering Adult T-Cell Leukemia

We treated two Japanese patients with Pneumocystis carinii pneumonia. Inclusion bodies in both adrenal glands of patient no. 1 indicated a herpesvirus infection. The patient no. 2 recovered from the pneumonia upon sulfametoxazole-trimethoprim medication and high-dose methylprednisolone therapy. In both patients, anti-human T-cell leukemia virus type I (HTLV-I) antibodies were positive and anti-human immunodeficiency virus antibodies were negative. Peripheral leukocytes in patient no. 1 numbered 13.6 X 10(3)/microliter with 25% morphologically normal lymphocytes and 4% abnormal. Lymphocyte surface markers were 72.6%, CD4+, 13.6% CD8+ and 46.4% CD3+. In patient no. 2, leukocytes numbered 13.8 X 10(3)/microliter, including 18% lymphocytes, although no morphologically abnormal lymphocyte was evident. Lymphocyte markers were 36.6% CD4+, 16.8% CD8+ and 46.6% CD3+. Monoclonal integration HTLV-I proviral DNA in lymphocytes of patient no. 2 was demonstrated by Southern blotting. Thus, both patients must have had smoldering adult T-cell leukemia (ATL) without any cutaneous involvement, whereas the morphological diagnosis from peripheral blood smears was one of HTLV-I carrier status with a few atypical lymphocytes, i.e., the preclinical state of smoldering ATL. Pneumocystis carinii infections, a viral infection of the adrenals (no. 1), negative purified protein derivatives of the tuberculin reaction and suppressed blastogenesis of the peripheral lymphocytes indicated HTLV-I-induced impairment of the immune mechanism to have already occurred in both patients without there being a vast proliferation of ATL cells.

Autocrine Growth of Interleukin 2-Producing Leukemic Cells in a Patient With Adult T Cell Leukemia

Leukemic cells in the peripheral blood of a patient with adult T cell leukemia (ATL), which expressed the Tac antigen/interleukin 2 (IL2) receptor, were investigated in vitro for autocrine growth by IL 2. The cells showed spontaneous proliferation in mitogen-free medium. The spontaneous proliferation of the cells was inhibited by monoclonal anti-IL 2 or anti-Tac antibody. These cells were found to produce messenger RNA for IL 2 and secrete IL 2 during short-term culture in the same medium. Recombinant IL 2 and IL 2 secreted by the cells enhanced the proliferation of the cells in a dose-dependent manner when added to the initial culture. These findings demonstrate that an autocrine mechanism by IL 2 is involved in the proliferation of ATL cells during short-term culture.

Autocrine growth of interleukin 2-producing leukemic cells in a patient with adult T cell leukemia

Leukemic cells in the peripheral blood of a patient with adult T cell leukemia (ATL), which expressed the Tac antigen/interleukin 2 (IL2) receptor, were investigated in vitro for autocrine growth by IL 2. The cells showed spontaneous proliferation in mitogen-free medium. The spontaneous proliferation of the cells was inhibited by monoclonal anti- IL 2 or anti-Tac antibody. These cells were found to produce messenger RNA for IL 2 and secrete IL 2 during short-term culture in the same medium. Recombinant IL 2 and IL 2 secreted by the cells enhanced the proliferation of the cells in a dose-dependent manner when added to the initial culture. These findings demonstrate that an autocrine mechanism by IL 2 is involved in the proliferation of ATL cells during short-term culture.