Lipid formulations of amphotericin B preserve and stabilize renal function in HSCT recipients

The current study assessed renal function based on medical records in adult hematopoietic stem cell transplant (HSCT) recipients with proven or probable invasive fungal infection (IFI) transplanted between 1995 and 2000. We confirm that amphotericin B deoxycholate (AmB-d) is nephrotoxic in a large percentage of HSCT recipients. Due to nephrotoxicity, defined as serum creatinine (SCr) >2.5 mg/dl or a 100% increase in SCr from baseline, 88% of patients treated with AmB-d were switched to a lipid formulation of amphotericin B (LFAB). In total, 53% of patients initiated on AmB-d were switched within the first week of therapy. Significantly more patients (70.6%) treated with AmB-d experienced a 100% increase in SCr from baseline compared to patients treated with either AmBisome (44.4%) or Abelcet (41.2%). A Cox Proportional Hazards Model revealed that, compared to patients initiated on AmBisome or Abelcet, the risk of nephrotoxicity (RR=1.5 vs AmBisome; RR=1.7 vs Abelcet), dialysis (RR=2.4 vs AmBisome; RR=1.4 vs Abelcet), and death (RR=2.0 vs AmBisome; RR=1.1 vs Abelcet) were all increased for patients initiated on AmB-d. Study results suggest that renal function improves and mortality declines when an LFAB is given to HSCT patients as initial therapy rather than as second-line therapy, the current practice.

Factors regulating the cytotoxic activity of the human natural killer cell line, NK-92

NK-92, a highly cytotoxic, interleukin-2 (IL-2)-dependent human natural killer (NK) cell line, has been of interest for basic and translational research. We report on a comprehensive analysis of NK-92 for factors implicated in NK cytotoxicity to elucidate factors underlying NK-92's high cytolytic activity and target range. Thus, we hope to develop a method to identify patients best suited to NK-92 immunotherapy. In addition, as a model system, we hope to increase understanding of the basis for the elevated activity exhibited by activated NK (ANK) cells. NK-92 exhibits an unusual receptor expression profile, expressing a relatively large number of activating (NKp30, NKp46, 2B4, NKGD, E, CD28) receptors. Conversely, it expresses few inhibitory receptors (NKGA/B, low levels of KIR2DL4, ILT-2), lacking most of the killer inhibitory receptors (KIRs) clonally expressed on normal NK cells. In addition, NK-92 expresses high levels of molecules involved in the perforin-granzyme cytolytic pathway as well as additional cytotoxic effector molecules including tumor necrosis factor (TNF)-superfamily members FasL, TRAIL, TWEAK, TNF-alpha, indicating the ability to kill via alternative mechanisms. NK-92 also expresses other molecules implicated immune effector cell regulation (CD80, CD86, CD40L, TRANCE) whose relevance in NK killing is unclear. This study provides initial data to develop a method to identify NK-92 susceptible cells (cells expressing ligands for NK-92 activating receptors ie CD48 for 2B4 and CD80/86 for CD28). Furthermore, this work suggests mechanisms that may contribute to ANK cell activity, including modulation of receptor expression to favor activation, up-regulation of cytotoxic effector molecules, and acquisition of new cytolytic pathways.

Interim analysis of the use of the anti-idiotype breast cancer vaccine 11D10 (TriAb) in conjunction with autologous stem cell transplantation in patients with metastatic breast cancer

The anti-idiotype monoclonal antibody breast cancer vaccine 11D10 (TriAb) was administered before and after autologous stem cell transplantation (ASCT) in 45 patients with metastatic breast cancer whose disease was responsive to conventional chemotherapy. Evidence of a positive anti-anti-idiotype antibody (Ab3) humoral response was noted at a median of 1.76 months post-ASCT (range, before ASCT-6 months) with this strategy. Maximal Ab3 levels and idiotype-specific T-cell proliferative responses were observed at a median of 3 and 4 months, respectively, after ASCT. The achievement of rapid immune responses after ASCT, during a known period of decreased immunoresponsiveness, opens the possibility of an additional antitumor effect at a time when the tumor burden is relatively small. Moreover, in this interim analysis, patients with the most vigorous humoral and cellular immune responses had a significant improvement in progression-free survival. Further follow-up and evaluation of this approach is warranted.

Prolonged survival after intensive therapy and purged ABMT in patients with multiple myeloma

Despite numerous strategies, the cure of multiple myeloma remains a difficult challenge. Recent approaches have involved dose-intensive therapy followed by stem cell transplantation, most often with autologous stem cells (ASCT). Although ASCT is of benefit, it is not considered curative. Between 1988 and 1995, we utilized an aggressive three-drug conditioning regimen followed by ABMT using marrow purged with either 4-hydroperoxycyclophosphamide (4-HC) or mafosphamide (MAF). Twenty-nine of 42 patients who had first received VAD (14 patients) or VAD followed by cyclophosphamide (7 g/m2 i.v.) + dexamethasone (40 mg/day p.o. x4) + GM-CSF (15 patients) met the eligibility criteria needed to undergo bone marrow harvest and ABMT, ie < or =10% marrow plasma cells and > or =50% decrease in paraprotein level. Alpha-interferon maintenance therapy was given post ABMT. Median follow-up is 7.5 years (range 5.0-11.25). Six early and two late non-relapse deaths occurred; 15 patients have relapsed. Seven patients remain in continuous CR (five) or PR (two), including three with stage IIIB disease at diagnosis. One patient developed a soft tissue sarcoma 8 years post ASCT. Although this protocol produced excessive toxicity compared with current approaches, the results demonstrate that dose-intensive therapy and ASCT can produce durable remission in this disease. Further development of dose-intensive strategies is warranted.

Treatment of steroid-resistant acute graft-versus-host disease with rabbit antithymocyte globulin

Acute graft-versus-host disease (A-GVHD) is a life-threatening complication of allogeneic stem cell transplantation (SCT), and primary therapy consists of high-dose corticosteroids. Patients who fail to respond adequately to corticosteroids require salvage treatment, with anti-T cell antibodies being the most commonly utilized group of agents. We report our institution's experience treating steroid-resistant GVHD in 36 adult patients (median age 39 years, range 24-55) with a rabbit antithymocyte globulin product (thymoglobulin). Eleven patients had undergone sibling SCT (10 histocompatible, 1 one-antigen mismatched) and 25 patients had received unrelated donor bone marrow (17 matched, 8 one-antigen mismatched); 32 patients (89%) had grade III or IV A-GVHD. Thymoglobulin was administered in two different regimens; group 1 patients (n = 13) received 2.5 mg/kg/day x 4-6 consecutive days with maintenance of all other immunosuppressives. Group 2 patients (n = 21) were given the same dose of thymoglobulin on days 1, 3, 5, and 7 with discontinuation of cyclosporine for 14 days, during which the corticosteroid dose was held at 2-3 mg/kg/day. Two patients had severe adverse reactions to thymoglobulin (hypoxemia and hypotension) and could not complete treatment, however, in the other patients, aside from transient leukopenia (25%) and and hepatic dysfunction (25%), the antibody preparation was well tolerated. Of the 34 evaluable patients, 13 patients had a complete response (38%) and 7 patients (21%) had a partial response, for an overall response rate of 59%. Response rate was higher in group 1 patients (77%) compared to group 2 patients (48%), (p = 0.15); skin GVHD was more responsive (96% of patients) than gut GVHD (46% of patients) or hepatic GHVD (36% of patients). Opportunistic infections were a significant complication, with 11 patients developing systemic fungal infections and 9 patients serious viral infections; there were seven episodes of bacteremia following thymoglobulin treatment and one fatal protozoal infection. There were 9 patients (25%) who developed post-SCT lymphoproliferative disorder (PTLD) and 4 patients who had a relapse of underlying primary malignancy; none of these patients survived. Of the 36 patients entered on the study, only 2 patients (6%) survive, at 15+ and 34+ months post-unrelated donor SCT. Although thymoglobulin is associated with an impressive response rate when administered for advanced steroid-resistant GVHD, long-term survival is uncommon, even in responders, primarily due to the high risk of developing either an opportunistic infection or a PTLD.

Allografting for indolent lymphoid neoplasms

BACKGROUND

Allogeneic bone marrow transplantation (BMT) has been used in patients with low-grade lymphoma (LGL) and chronic lymphocytic leukemia (CLL) with the goal of achieving long-term disease-free survival.

PATIENTS AND METHODS

Twenty-nine patients with these diagnoses (LGL = 19, CLL = 10) received allogeneic BMT between September 1995 and January 1999. Median age was 42 (range 20-52) years. Twenty-three of twenty-nine patients (79%) were Ann Arbor or Rai stage IV at the time of transplant; twenty-four (83%) had never achieved complete remission (CR). Donor source was HLA-matched sibling (20), unrelated (8) and syngeneic (1).

RESULTS

Seventeen patients are currently alive, a median of 29 months (range 1-85) post-BMT with a median KPS of 90%. Twenty-three of twenty-seven evaluable patients (85%) achieved CR post-BMT. Six patients had refractory/recurrent disease. Death occurred related to transplant complications in eight patients and underlying disease in four. Overall and event-free survival for the whole group is 51% and 44%, respectively.

CONCLUSIONS

Allogeneic BMT for young patients with advanced stage LGL or CLL is a feasible strategy that can result in achievement of long-term disease-free survival.

Allogeneic bone marrow transplantation for low-grade lymphoma and chronic lymphocytic leukemia

Twenty-six patients with low-grade lymphoma (LGL) (n = 18) or chronic lymphocytic leukemia (CLL) (n = 8) received allogeneic BMTs between 1985 and 1998. Median age was 42 years, median interval from diagnosis to transplant 22 months and median number of prior treatments three. Twenty (77%) had stage IV disease; 22 (85%) had never achieved CR. Donor source was HLA matched sibling (n = 19, 73%), matched unrelated (n = 6, 23%) or syngeneic (n = 1). Conditioning therapy included total body irradiation in 23 patients and busulphan in three. Twenty-five received GVHD prophylaxis with cyclosporine A; + methotrexate (n = 19), + methylprednisolone (n = 2) or + T cell depletion of allograft +/- methotrexate (n = 4). Sixteen patients are alive, a median of 2.4 years post BMT. Death occurred due to transplant complications (n = 7) or underlying disease (n = 3). Eighteen (12 LGL, six CLL) of 22 evaluable patients (82%) achieved CR post BMT. Cumulative incidence of refractory/recurrent disease was 18% (95% confidence interval (CI) 7-42%). Overall and event-free survivals were 58% (95% CI 35-75%) and 54% (95% CI 32-72%), respectively. Allogeneic BMT for young patients with advanced LGL or CLL is feasible and can result in long-term disease-free survival.

Antileukemic effect of interleukin-2-transduced murine bone marrow after autologous transplantation

Myeloablative chemotherapy or radiation therapy supported by autologous stem cell transplantation (SCT) for the treatment of hematologic malignancies such as acute leukemia, lymphoma, and myeloma is associated with high rates of relapse. The reasons for this are 1) autologous transplantation lacks the in vivo graft-vs.-tumor (GVT) effect associated with allogeneic SCT, which is effective in controlling or eliminating residual malignant cells remaining in the body after high-dose therapy, and 2) contaminating malignant cells in the autologous graft are reinfused into the body. Some researchers have attempted to administer immunomodulatory cytokines to simulate a GVT effect, and although this has shown some efficacy, it has several disadvantages. These include high toxicity associated with systemic administration, a short in vivo half-life, and insufficient levels reaching the site of residual disease. As an alternative, we investigated whether delivery of the cytokine interleukin (IL)-2 to the bone marrow can exert an antileukemic effect while avoiding the problems associated with systemic administration. We describe the delivery of IL-2 to the bone marrow by transplantation of syngeneic bone marrow, retrovirally transduced with the gene for IL-2, into lethally irradiated mice. We were able to efficiently transduce murine bone marrow with the IL-2 gene without adversely affecting clonogenic output from hematopoietic progenitors, and we were able to achieve expression of the transgene in transplanted animals. However, IL-2 transduction inhibited hematopoietic reconstitution in lethally irradiated mice. Marrow transduced with high-titer, high-expressing IL-2 retrovirus failed to engraft, and a low-titer, low-expressing IL-2 retrovirus also demonstrated reduced engraftment, although engraftment was sufficient to support survival of transplanted mice. Long-term, low-level expression of the IL-2 transgene was detectable in these mice and was effective in exerting an antileukemic effect. Mice transplanted with control marrow and challenged with leukemic cells suffered 100% mortality within 70 days, whereas mice transplanted with IL-2-transduced marrow exhibited 50% survival over the 175-day duration of this study. The work shows that delivery of immunomodulatory cytokines to the bone marrow can be achieved by transplantation of genetically modified hematopoietic cells. Furthermore, low-level IL-2 expression can exert an antileukemic effect. These data suggest that this may be an effective immunotherapeutic strategy to reduce relapse after autologous transplantation, but the selection and expression of the cytokine must be carefully considered to minimize adverse effects on hematopoiesis.

Antileukemic effect of interleukin-2-transduced murine bone marrow after autologous transplantation

Myeloablative chemotherapy or radiation therapy supported by autologous stem cell transplantation (SCT) for the treatment of hematologic malignancies such as acute leukemia, lymphoma, and myeloma is associated with high rates of relapse. The reasons for this are 1) autologous transplantation lacks the in vivo graft-vs.-tumor (GVT) effect associated with allogeneic SCT, which is effective in controlling or eliminating residual malignant cells remaining in the body after high-dose therapy, and 2) contaminating malignant cells in the autologous graft are reinfused into the body. Some researchers have attempted to administer immunomodulatory cytokines to simulate a GVT effect, and although this has shown some efficacy, it has several disadvantages. These include high toxicity associated with systemic administration, a short in vivo half-life, and insufficient levels reaching the site of residual disease. As an alternative, we investigated whether delivery of the cytokine interleukin (IL)-2 to the bone marrow can exert an antileukemic effect while avoiding the problems associated with systemic administration. We describe the delivery of IL-2 to the bone marrow by transplantation of syngeneic bone marrow, retrovirally transduced with the gene for IL-2, into lethally irradiated mice. We were able to efficiently transduce murine bone marrow with the IL-2 gene without adversely affecting clonogenic output from hematopoietic progenitors, and we were able to achieve expression of the transgene in transplanted animals. However, IL-2 transduction inhibited hematopoietic reconstitution in lethally irradiated mice. Marrow transduced with high-titer, high-expressing IL-2 retrovirus failed to engraft, and a low-titer, low-expressing IL-2 retrovirus also demonstrated reduced engraftment, although engraftment was sufficient to support survival of transplanted mice. Long-term, low-level expression of the IL-2 transgene was detectable in these mice and was effective in exerting an antileukemic effect. Mice transplanted with control marrow and challenged with leukemic cells suffered 100% mortality within 70 days, whereas mice transplanted with IL-2-transduced marrow exhibited 50% survival over the 175-day duration of this study. The work shows that delivery of immunomodulatory cytokines to the bone marrow can be achieved by transplantation of genetically modified hematopoietic cells. Furthermore, low-level IL-2 expression can exert an antileukemic effect. These data suggest that this may be an effective immunotherapeutic strategy to reduce relapse after autologous transplantation, but the selection and expression of the cytokine must be carefully considered to minimize adverse effects on hematopoiesis.

Expression of SCM-1alpha/lymphotactin and SCM-1beta in natural killer cells is upregulated by IL-2 and IL-12

Recruitment of lymphocytes is an important feature of the host immune response against pathogens. However, the mechanisms by which lymphocytes are attracted are not yet fully understood. Recently, the cDNA of a lymphocyte-specific chemokine, lymphotactin (Lptn), was isolated from murine and human T cells and was also found to be expressed in murine NK cells and human NK cell clones. This study investigated the influence of interleukin (IL)-2 and IL-12 on the expression of Lptn, also known as SCM (single cysteine motif)-1alpha, and SCM-1beta, a 97% homolog of Lptn, in freshly isolated human NK cells and the human NK cell line NK-92. Northern blot analysis and RT-PCR confirmed that nonactivated human NK cells expressed both genes at low level. After activation with IL-2 or IL-12, the expression of both Lptn and SCM-1beta was upregulated within hours. NK-92 cells maintained in medium supplemented with IL-2 constitutively expressed SCM-1 mRNA. However, after 24 h of IL-2 starvation and subsequent culturing at various IL-2 concentrations, the expression of Lptn/SCM-1alpha was upregulated in a dose-dependent manner, whereas the expression of SCM-1beta remained consistently high. These observations indicate that NK cells, in addition to T lymphocytes, express Lptn/SCM-1alpha and SCM-1beta after cytokine activation. The upregulation of these chemokines in NK cells on activation likely acts to increase the number of effector cells reaching the site of an immune response such as inflammation.

Immunotherapy of malignant melanoma in a SCID mouse model using the highly cytotoxic natural killer cell line NK-92

In this work, we evaluated the potential of the natural killer (NK) cell line NK-92 and its IL-2-independent variants NK-92MI and CI, as immunotherapy for melanoma. In vitro, we found that NK-92 was much more cytotoxic to a number of human melanoma cell lines than lymphokine-activated killer (LAK) cells, particularly at low effector/target (E:T) ratios. In vivo treatment of mice challenged with MEWO melanoma cells with i.v. administered NK-92 and NK-92-MI resulted in a 1.5-2.5-fold increase in average length of survival. NK-92, MI, and CI were also effective against the WM1341 cell line, causing a 2-5-fold increase in survival when administered before the malignant cells. With s.c. injection, MEWO and WM1341 caused a primary tumor mass, secondary tumors, and metastatic cells. NK-92 cells reduced WM1341 primary tumor size by 40-90% and MEWO tumors by 30-75%. Similar results were seen with NK-92MI and CI. These data show that NK-92 cells are highly cytotoxic to human melanoma cells in vitro and in vivo and suggest that treatment with NK-92 cells may be a potentially effective immunotherapeutic modality in melanoma.

Regimen-related toxicity and non-relapse mortality with high-dose cyclophosphamide, carmustine (BCNU) and etoposide (VP16-213) (CBV) and CBV plus cisplatin (CBVP) followed by autologous stem cell transplantation in patients with Hodgkin's disease

This analysis compares the regimen-related toxicity (RRT) and overall non-relapse mortality (NRM) in Hodgkin's disease patients conditioned with either CBV (cyclophosphamide, BCNU (carmustine), and VP16-213 (etoposide)) (26 patients) or CBVP (CBV + cisplatin) (68 patients) followed by autologous stem cell transplantation (ASCT). CBVP included a continuous infusion rather than intermittent doses of etoposide, a lower BCNU dose and the addition of cisplatin. RRT and NRM were determined for each regimen and compared; risk factors for each were examined by multivariate analysis. Grade IV (fatal) RRT occurred in five patients (pulmonary in two, cardiac in two, and central nervous system in one). Eighteen patients experienced grade II-III pulmonary RRT, consistent with BCNU damage in 15. Prior nitrosourea exposure was the main risk factor for pulmonary RRT. Grade II mucosal and hepatic RRT occurred less often after CBVP vs CBV (P = 0.031 and 0.0003, respectively). In addition, three other early and eight late non-relapse deaths were seen. Median follow-up of the entire group is 5.1 (range 2.8-10.2) years. The probability of overall NRM was 26% (95% confidence interval (CI) 13-50%) with CBV vs 23% (95% CI 12-41%) with CBVP (P = 0.40). The progression-free survival and relapse rates were similar. Although the rates of fatal RRT, pulmonary RRT and overall NRM were similar with CBV or CBVP, CBVP produced less mucosal and liver RRT with a comparable antitumor effect. As many autografted patients are cured, future efforts should include measures to decrease NRM.

Characterization of genetically altered, interleukin 2-independent natural killer cell lines suitable for adoptive cellular immunotherapy

NK-92 is a highly cytotoxic natural killer (NK) tumor cell line that possesses properties that make it an excellent candidate for adoptive cellular immunotherapy. However, the cytotoxicity of NK cells is dependent on cytokines such as interleukin 2 (IL-2). Although NK-92 cells maintain cytotoxicity for a time after withdrawal of IL-2, clinical use will probably require prolonged treatment with fully activated cells to eliminate disease effectively. The ability to support cytotoxic cells with exogenously administered IL-2 is limited by associated toxicity. Therefore, we describe the transfection of the IL-2-dependent NK-92 cell line with human IL-2 (hIL-2) cDNA by particle-mediated gene transfer to create two IL-2-independent variants, NK-92MI and NK-92 CI, and describe their characterization and comparison with parental cells. Both variants were shown to contain, express, and synthesize the hIL-2 cDNA. IL-2 synthesis was higher in NK-92MI cells compared with NK-92CI cells, with no expression in parental cells. Functionally, the cytotoxicity of all three cell lines was similar and coincubation with IL-2-independent variants did not affect hematopoietic progenitor cells. NK-92MI and NK-92CI cells were more radiosensitive than NK-92 cells, with proliferation inhibited at lower radiation doses and increased morality and decreased cytotoxicity compared with parental cells. Data presented here show that we have created by particle-mediated gene transfer two IL-2-independent variants of NK-92 that are identical to parental cells in virtually all respects, including high cytotoxic activity. The nonviral transfection of these cells makes them suitable for clinical applications. These IL-2-independent cells should allow prolonged treatment with fully active natural killer cells without the need for exogenous IL-2 support.

Lymphoproliferative disorders following allogeneic bone marrow transplantation: the Vancouver experience

Between June 1988 and May 1996, 428 patients underwent allogeneic BMT (288 related donor (RD) and 140 unrelated donor (UD)) at the Vancouver General Hospital. Eight patients (UD six and RD two) developed a post-transplant lymphoproliferative disorder (PTLD). Median age at BMT was 38 years (range 22-51). Five of the six UD allografts were T cell depleted. Cyclosporine+/-methotrexate was used for GVHD prophylaxis. All eight patients developed GVHD; in six this was refractory to treatment with corticosteroids. Rabbit antithymocyte globulin (ATG) or an anti-CD5-ricin A chain immunotoxin (Xomazyme) was used as second-line therapy for GVHD. Presentation with PTLD occurred at median day 90.5 (range 34-282) post BMT. Five of the eight patients had a rapidly progressive course characterized by fever, lymphadenopathy, lung and liver involvement and died within 3-8 days. PTLD was an incidental finding at post mortem examination in two patients. The remaining patient had localized disease and recovered. Pathological analysis revealed two morphological patterns; diffuse large B cell lymphoma (DLBC lymphoma, five patients) and polymorphous B cell hyperplasia (PBCH, three patients). EBV expression was positive in all eight cases and monoclonality was demonstrated in seven cases. In multivariate analysis, T cell depletion of the allograft (P=0.0001, relative risk (RR)=30.5), anti-T cell therapy for GVHD (P=0.006, RR=12.7) and acute GVHD grades 3-4 (P=0.04, RR=7.7) were the significant factors for development of PTLD. In conclusion, we have identified two forms of PTLD after BMT: one is characterized by disseminated disease with a rapidly progressive and often fulminant course and the other by localized, relatively indolent disease. Morphology, EBV positivity and clonality do not appear to correlate with the clinical course. The major risk factors for development of PTLD after BMT are ex vivo T cell depletion of the allograft and in vivo anti-T cell therapy for GVHD.

Antileukemia activity of a natural killer cell line against human leukemias

We describe here the in vitro and in vivo antileukemia activity of a recently described natural killer (NK) cell line (NK-92), which has features of human activated NK cells. The cytotoxic activity of rhIL2-dependent cultured NK-92 cells against primary patient-derived leukemic target cells [12 acute myelogenous leukemias (AMLs), 7 T acute lymphoblastic leukemias (T-ALLs), 14 B-lineage-ALLs, and 13 chronic myelogenous leukemias (CMLs)], human leukemic cell lines (K562, KG1, HL60, Raji, NALM6, TALL-104, CEM-S, and CEM-T) and normal bone marrow cells was measured in 51Cr-release assay (CRA). The patient-derived leukemias could be subdivided into three groups based on their sensitivity to NK-92 cells: insensitive (< or =19% lysis), sensitive (20-49% lysis), and highly sensitive (> or =50% lysis) at an E:T ratio of 9:1. Of 46 patient-derived samples, 24 (52.2%) were sensitive or highly sensitive to NK-92-mediated in vitro cytotoxicity (6 of 12 AMLs, 7 of 7 T-ALLs, 5 of 14 B-lineage-ALLs, and 6 of 13 CMLs). NK-92 cells were highly cytotoxic against all of the eight leukemic cell lines tested in a standard 4-h CRA. Normal human bone marrow hematopoietic cells derived from 18 normal donors were insensitive to NK-92-mediated cytolysis. In comparison with human lymphokine-activated killer cells, normal NK cells, and T cells, NK-92 cells displayed more powerful antileukemia activity against a patient-derived T-ALL as well as K562 and HL60 cells, both in in vitro CRA and in a xenografted human leukemia SCID mouse model. The NK-92 cells did not induce the development of leukemia in SCID mice after i.v., i.p., or s.c. inoculation. In adoptive transfer experiments, SCID mice receiving i.p. inoculations of human leukemias derived from a T-ALL (TA27) and an AML (MA26) that were highly sensitive to the cytolysis of NK-92 cells in vitro, as well as a pre-B-ALL (BA31) that was insensitive to the in vitro cytolysis of NK-92 cells, were treated by administration of NK-92 cells with or without rhIL2 (2 x 10(7) NK-92 cells i.p.; one dose or five doses). Survival times of SCID mice bearing the sensitive TA27 and MA26 leukemias were significantly prolonged by adoptive cell therapy with NK-92 cells. Some of the animals who received five doses of NK-92 cells with or without rhIL2 administration were still alive without any signs of leukemia development 6 months after leukemia inoculation. In contrast, survival of mice bearing the insensitive BA31 leukemia were not affected by this treatment. This in vitro and in vivo antileukemia effect of NK-92 cells suggests that cytotoxic NK cells of this type may have potential as effectors of leukemia control.

Induction of sensitivity to NK-mediated cytotoxicity by TNF-alpha treatment: possible role of ICAM-3 and CD44

SR-91 is a natural killer (NK)-resistant leukemic cell line expressing a low level of ICAM-1. Pre-treatment of SR-91 cells with TNF-alpha or IFN-gamma, increased both ICAM-1 (CD54) expression on SR-91 cells and binding to the human NK cell line NK-92. However, only TNF-alpha-treated SR-91 cells became sensitive to killing by NK-92 cells. The increased binding induced by both cytokines and the TNF-alpha-induced sensitivity of SR-91 cells to NK-92 cell killing were abrogated by anti-LFA-1 mAb as well as by a combination of antibodies against the three ligands of LFA-1 (CD11a/CD18), ICAM-1 (CD54), ICAM-2 (CD102) and ICAM-3 (CD50). This indicated that LFA-1 interaction with the three ICAMs on SR-91 cells is essential for effector-target cell binding (which is a prerequisite for subsequent target cell lysis), but is insufficient to render the SR-91 cells sensitive to killing by NK-92 cells. TNF-alpha, but not IFN-gamma also induced the activation of LFA-1, CD44 and beta1 integrins on SR-91 cells. Based on these observations we propose that the differential effect of TNF-alpha and IFN-gamma could be related to the activation of certain adhesion molecules on the surface of SR-91 cells by TNF-alpha that, upon interaction with their counter-receptors on NK-92 cells, lead to the activation of the NK-92 cells.