Inability of granule polarization by NK cells defines tumor resistance and can be overcome by CAR or ADCC mediated targeting

Background

On encountering a susceptible target, natural killer (NK) cells mediate cytotoxicity through highly regulated steps of directed degranulation. Cytotoxic granules converge at the microtubule organizing center and are polarized toward the immunological synapse (IS), followed by granule exocytosis. NK cell retargeting by chimeric antigen receptors (CARs) or mAbs represents a promising strategy for overcoming tumor cell resistance. However, little is known about the lytic granule dynamics of such retargeted NK cells toward NK-cell-resistant tumors.

Methods

Here, we used spinning disk confocal microscopy for live-cell imaging to analyze granule-mediated NK cell cytotoxicity in ErbB2-targeted CAR-expressing NK-92 cells (NK-92/5.28.z) and high-affinity FcR transgenic NK-92 cells plus Herceptin toward ErbB2-positive breast cancer cells (MDA-MB-453), which are resistant to parental NK-92.

Results

Unmodified NK-92 cells cocultured with resistant cancer cells showed stable conjugate formation and granule clustering, but failed to polarize granules to the IS. In contrast, retargeting by CAR or FcR+Herceptin toward the MDA-MB-453 cells enabled granule polarization to the IS, resulting in highly effective cytotoxicity. We found that in NK-92 the phosphoinositide 3-kinase pathway was activated after contact with resistant MDA-MB-453, while phospholipase C-γ (PLCγ) and mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) were not activated. In contrast, retargeting by CAR or antibody-dependent cell-mediated cytotoxicity (ADCC) provided the missing PLCγ and MEK/ERK signals.

Conclusions

These observations suggest that NK cells can create conjugates with resistant cancer cells and respond by granule clustering, but the activation signals are insufficient to induce granule polarization and consequent release of lytic enzymes. Retargeting by CAR and/or the FcR/mAb (ADCC) axis provide the necessary signals, leading to granule polarization and thereby overcoming tumor cell resistance.

Keywords: NK cells, NK-92, haNK, ADCC, Chimeric Antigen Receptor (CAR), breast cancer, cancer immunotherapy, live-cell imaging, granule polarization

NK-92: an 'off-the-shelf therapeutic' for adoptive natural killer cell-based cancer immunotherapy

Natural killer (NK) cells are increasingly considered as immunotherapeutic agents in particular in the fight against cancers. NK cell therapies are potentially broadly applicable and, different from their T cell counterparts, do not cause graft-versus-host disease. Efficacy and clinical in vitro or in vivo expansion of primary NK cells will however always remain variable due to individual differences of donors or patients. Long-term storage of clinical NK cell lots to allow repeated clinical applications remains an additional challenge. In contrast, the established and well-characterized cell line NK-92 can be easily and reproducibly expanded from a good manufacturing practice (GMP)-compliant cryopreserved master cell bank. Moreover, no cost-intensive cell purification methods are required. To date, NK-92 has been intensively studied. The cells displayed superior cytotoxicity against a number of tumor types tested, which was confirmed in preclinical mouse studies. Subsequent clinical testing demonstrated safety of NK-92 infusions even at high doses. Despite the phase I nature of the trials conducted so far, some efficacy was noted, particularly against lung tumors. Furthermore, to overcome tumor resistance and for specific targeting, NK-92 has been engineered to express a number of different chimeric antigen receptors (CARs), including targeting, for example, CD19 or CD20 (anti-B cell malignancies), CD38 (anti-myeloma) or human epidermal growth factor receptor 2 (HER2; ErbB2; anti-epithelial cancers). The concept of an NK cell line as an allogeneic cell therapeutic produced 'off-the-shelf' on demand holds great promise for the development of effective treatments.

Treatment of patients with advanced cancer with the natural killer cell line NK-92

BACKGROUND AIMS

Natural killer (NK) cells, either naive or genetically engineered, are increasingly considered for cellular therapy of patients with malignancies. When using NK cells from peripheral blood, the number of expanded NK cells can be highly variable and the need for NK cell enrichment can make the process expensive. The NK-92 cell line (CD56+/CD3-) that was isolated from a patient with lymphoma has predictable high cytotoxic activity and can be expanded under good manufacturing practice conditions in recombinant interleukin-2.

METHODS

Fifteen patients (age, 9-71 years) with advanced, treatment-resistant malignancies, either solid tumors/sarcomas (n = 13) or leukemia/lymphoma (n = 2), received two infusions of NK-92 cells, given 48 h apart. Three cohorts of patients were treated with escalating doses of NK-92 cells (n = 7 at 1 × 10(9), n = 6 at 3 × 10(9) and n = 2 at 1 × 10(10) cells/m(2)).

RESULTS

No infusion-related or long-term side effects were observed. The dose of 10(10) cells/m(2) was considered the maximum expandable cell dose with the use of an established culture bag system. Three fourths of patients with lung cancer had some anti-tumor response. Only one patient of seven had development of human leukocyte antigen antibodies. The persistence of NK-92 cells (male origin) in the circulation was confirmed by Y chromosome-specific polymerase chain reaction in two female patients.

CONCLUSIONS

Infusions of NK-92 cells up to 10(10) cells/m(2) were well tolerated. Despite the allogeneic nature of NK-92, development of human leukocyte antigen antibodies in these patients with cancer appears to be rare. The cells can persist in the recipient's circulation for at least 48 h. Some encouraging responses were seen in patients with advanced lung cancer.

Allogeneic hematopoietic stem-cell transplantation with reduced-intensity conditioning in intermediate- or high-risk patients with myelofibrosis with myeloid metaplasia

A total of 21 patients with myelofibrosis with myeloid metaplasia (MMM), with a median age of 54 years (range, 27-68 years), were prepared with a reduced-intensity conditioning (RIC) regimen. The patients received an allogeneic marrow (n = 3) or peripheral blood stem-cell (n = 18) transplant from HLA-matched related (n = 18) or unrelated (n = 2), or 1 Ag-mismatched related (n = 1), donors. RIC regimens included fludarabine/total body irradiation 200 cGy (n = 5) or 450 cGy (n = 1), fludarabine/melphalan (n = 7), thiotepa/cyclophosphamide (n = 7), and thiotepa/fludarabine (n = 1). At the time of transplantation, all of the patients were at intermediate (n = 13) or high (n = 8) risk, according to the Dupriez classification. Of the patients, 19 had grade III or IV marrow fibrosis. All of the patients achieved full engraftment but one. Posttransplantation chimerism analysis showed more than 95% donor cells in 18 patients, while 2 patients achieved complete donor chimerism after donor leukocyte infusion (DLI). Acute graft-versus-host disease (GVHD) grades II to IV was observed in 7 patients, grades III to IV in 2, and extensive chronic GVHD in 8 of 18 evaluable patients. There were 3 patients who died from acute GVHD, infection, and relapse. There are 18 patients alive 12 to 122 months (median, 31 months) after transplantation, and 17 are in remission (1 after a second transplantation). The use of RIC regimens in allogeneic stem cell transplantation results in prolonged survival in intermediate/high-risk MMM patients.

Heteroclitic CD33 peptide with enhanced anti-acute myeloid leukemic immunogenicity

The goal of these studies was to engineer a synthetic CD33 peptide with enhanced immunogenicity for the induction of acute myeloid leukemia (AML)-specific CTLs. Eight modified CD33 peptides YLISGDSPV, YIGSGDSPV, YIIIGDSPV, YIILGDSPV, YIISGISPV, YIISGDLPV, YIISGDSWV and YIISGDSPL were designed for increased HLA-A2.1 or T cell receptor affinity and compared with the native CD33(65-73) peptide, AIISGDSPV, for enhanced immunogenicity. The YLISGDSPV peptide was found to be the most immunogenic epitope producing highly cytolytic CTLs against AML target cells. The CTLs generated withYLISGDSPV peptide showed CD33 peptide-specificity through targeting of both native (AIISGDSPV) and modified (YLISGDSPV) peptide presenting EBV-BLCL. The CTL cultures displayed a distinct phenotype consisting of a high percentage of activated memory (CD69(+)/CD45RO(+))-CD8(+)and a low percentage of naive (CD45RA(+)/CCR7(+))-CD8(+)cells. In addition, T-cell clones specific to the YLISGDSPV peptide were isolated and characterized to target AML cells. The clones exhibited both HLA-A2.1-restricted and AML cell-specific cytotoxicity that was mediated through a granule-dependent pathway. More importantly, the CTL clones did not lyse or inhibit the proliferation of normal CD34(+) progenitor cells. In conclusion, we report on the identification of a highly immunogenic heteroclitic YLISGDSPV CD33 epitope that is a promising candidate for immunotherapy targeting AML.

Identification of CD19 and CD20 Peptides for Induction of Antigen-Specific CTLs against B-Cell Malignancies

The purpose of these studies was to develop immunogenic peptides derived from the CD19 and CD20 self-antigens for the induction of antigen-specific CTLs against B-cell malignancies. A total of seven peptides were designed and examined for their HLA-A2.1 affinity and immunogenicity. Of these peptides, we identified two highly immunogenic HLA-A2.1-specific peptides, CD19(150-158) (KLMSPKLYV) and CD20(188-196) (SLFLGILSV), which were capable of inducing peptide-specific CTLs. The CTLs displayed HLA-A2.1-restricted and antigen-specific cytotoxicity against Burkitt's lymphoma, chronic B cell leukemia, and multiple myeloma cell lines. The CD19 or CD20 peptide-specific CTL cytotoxicity was confirmed using HLA-A2.1(+) T2 cells presenting the appropriate peptide. No cytotoxic activity was observed against T2 cells presenting the irrelevant MAGE-3 peptide or T2 cells alone. In addition, the CTLs displayed a significant (P < 0.05) increase in cell proliferation and IFN-gamma secretion (>830 ng/mL) following restimulation with HLA-A2.1(+)/CD19(+)/CD20(+) tumor cells. The CTLs also displayed a distinct phenotype consisting of a high percentage of CD69(+)/CD45RO(+) and a low percentage of CD45RA(+)/CCR7(+) CD4(+) or CD8(+) T cells characteristic of effector memory cell population. Cyclic guanosine 3',5'-monophosphate culture conditions using serum-free AIM-V medium containing human AB serum, recombinant human interleukin 2 (Proleukin) and CD3/CD28 Dynabeads were developed resulting in a 35-fold expansion of CD20 peptide-specific CTLs. The expanded CD20-CTLs retained their cytotoxic activity (28-49%) against the Burkitt's lymphoma cell line. In conclusion, we report here on the identification of novel immunogenic CD19(150-158) (KLMSPKLYV) and CD20(188-196) (SLFLGILSV) peptides that have immunotherapeutic potentials as peptide vaccines or targeted T-cell therapies for treating B-cell malignancies.

The effect of LIGHT in inducing maturation of monocyte-derived dendritic cells from MDS patients

LIGHT is a recently cloned novel cytokine belonging to the TNF family that is selectively expressed on immature dendritic cells (iDCs) generated from monocytes isolated from human PBMCs. In these studies, we demonstrate that exogenous soluble LIGHT or soluble CD40 ligand (CD40L) can promote monocyte-derived dendritic cell maturation in vitro by the up-regulation of CD86, CD80, CD83, and HLA-DR antigen expression. Immature dendritic cells differentiated from monocytes of MDS patients displayed lower levels of costimulatory and HLA-DR molecules compared with iDCs differentiated from monocytes of normal subjects. However, upon induction of maturation by LIGHT or CD40L, the expression of costimulatory and HLA-DR molecules is comparable between DCs from MDS and normal subjects. Exogenous LIGHT- and CD40L-stimulated mature DCs (mDCs) also displayed increased antigen presentation to autologous T lymphocytes (tetanus toxin) or allogeneic T lymphocytes in mixed lymphocyte reactions. DCs matured by LIGHT showed increased secretion of IL-6, IL-12p75, and TNF-alpha, but not IL-1beta. We conclude that both LIGHT and CD40L are immunoregulating factors that induce monocyte-derived iDCs from MDS patients to undergo maturation resulting in increased antigen presentation and T-cell activation. Monocyte-derived DCs can be stimulated to undergo phenotypic and functional changes with LIGHT that might be applied in the development of a DC-based vaccine for MDS treatment.

Identification of novel CD33 antigen-specific peptides for the generation of cytotoxic T lymphocytes against acute myeloid leukemia

Identification of immunogenic peptides for the generation of cytotoxic T lymphocytes (CTLs) may lead to the development of novel cellular therapies to treat disease relapse in acute myeloid leukemia (AML) patients. The objective of these studies was to evaluate the ability of unique HLA-A2.1-specific nonameric peptides derived from CD33 antigen to generate AML-specific CTLs ex vivo. We present data here on the identification of an immunogeneic HLA-A2.1-specific CD33(65-73) peptide (AIISGDSPV) that was capable of inducing CTLs targeted to AML cells. The CD33-CTLs displayed HLA-A2.1-restricted cytotoxicity against both mononuclear cells from AML patients and the AML cell line. The peptide- as well as AML cell-specificity of CD33-CTLs was demonstrated and the secretion of IFN-gamma by the CTLs was detected in response to CD33(65-73) peptide stimulation. The cultures contained a distinct CD33(65-73) peptide-tetramer(+)/CD8(+) population. Alteration of the native CD33(65-73) peptide at the first amino acid residue from alanine (A) to tyrosine (Y) enhanced the HLA-A2.1 affinity/stability of the modified CD33 peptide (YIISGDSPV) and induced CTLs with increased cytotoxicity against AML cells. These data therefore demonstrate the potential of using immunogenic HLA-A2.1-specific CD33 peptides in developing a cellular immunotherapy for the treatment of AML patients.

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.

Use of the anti-idiotype breast cancer vaccine 11D10 in conjunction with autologous stem cell transplantation in patients with metastatic breast cancer

The results of cytotoxic therapy, including dose-intensive therapy requiring autologous stem cell transplantation (ASCT), have been disappointing in patients with metastatic breast cancer, as almost all patients eventually experience disease progression. There has been a renewed interest in immunotherapeutic strategies in this disease, including evaluation of several breast cancer vaccines. In the current study, we describe the results of a program in which the anti-idiotype breast cancer vaccine 11D10 (TriAb) was administered before and after ASCT in patients with metastatic breast cancer chemosensitive to previous conventional therapy. The toxicity of this approach was acceptable, and idiotype-specific humoral and T-cell proliferative responses were observed in the majority of patients within a few weeks post-ASCT. The actuarial 3-year overall survival rate was 48% (95% CI, 32%-64%), while the progression-free survival rate was 32% (95% CI, 19%-45%). Multivariate analysis identified achievement of a strong antibody and cellular immune response to the vaccine as the only significant prognostic factors for outcome. The ability to reliably produce robust immune responses after ASCT is encouraging. Further studies are required to determine if the immune response mediates an antitumor benefit in these patients.

Role of immunotherapy in stem cell transplantation

Relapse of the underlying malignancy continues to be a major problem after both autologous and allogeneic stem cell transplantation. Over the years, it has been recognized that immune-mediated graft-versus-tumor effects are crucially involved in eliminating minimal disease and controlling its recurrence after stem cell transplantation. This recognition has led to a number of studies that have attempted to stimulate a cellular immune response in the recipient, especially after allogeneic transplantation. Immunotherapy after autologous transplantation has to take into consideration the fact that patients' immune cells frequently are compromised and tolerance to the host tumor may have developed. Hence, trials involving the administration of cytokines (such as with interleukin and interferon) have shown limited benefits. This situation is different for allogeneic transplantation for which the infusion of donor lymphocytes has shown disease regression, especially in patients with chronic leukemias. However, such treatment is effective only if the patient has limited disease, and severe graft-versus-host disease frequently has to be accepted as a complication. This fact has led investigators to pursue the generation of specific lymphocytes that can recognize tumor antigens but not necessarily induce graft-versus-host disease. Such studies are in the early stages, and although some promising results have been observed, it is unclear at this point if the antitumor effect can be separated sufficiently from the graft-versus-host disease mediated by allogeneic lymphocytes. More recently, it has been shown that natural killer (NK) cells can have an antitumor effect in myeloid malignancies, particularly if the cells are allogeneic and do not recognize self-HLA antigens. At this point, it appears that engineered T-lymphocytes and allogeneic NK cells may be useful in preventing or treating relapse after allogeneic transplantation. It remains to be seen if such novel cellular therapies can also be implemented after autologous transplantation via the use of engineered allogeneic immune cells.

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.

Cytogenetic abnormalities in primary myelodysplastic syndrome are highly predictive of outcome after allogeneic bone marrow transplantation

Allogeneic bone marrow transplantation (BMT) is the only curative therapy available for patients with myelodysplastic syndrome (MDS). In an attempt to identify prognostic factors influencing outcome, we collected data retrospectively on 60 consecutive adult patients who had undergone BMT at our center for primary MDS or acute myelogenous leukemia evolving from preexisting primary MDS (sAML). Patients were divided into subgroups according to cytogenetic abnormalities based on a recently described International MDS Workshop categorization system. The 7-year actuarial event-free survival (EFS), relapse rate, and nonrelapse mortality (NRM) for all patients were 29% (95% confidence interval [CI], 16% to 43%), 42% (CI, 24% to 67%), and 50% (CI, 37% to 64%), respectively. The EFS for the good-, intermediate-, and poor-risk cytogenetic subgroups were 51% (CI, 30% to 69%), 40% (CI, 16% to 63%), and 6% (CI, 0% to 24%), respectively (P = .003). The corresponding actuarial relapse rates were 19% (CI, 6% to 49%), 12% (CI, 2% to 61%), and 82% (CI, 48% to 99%), respectively (P = . 002) with no difference in NRM between the subgroups. Univariate analysis showed cytogenetic category, French-American-British (FAB) subtype, and graft-versus-host disease (GVHD) prophylaxis used to be predictive of relapse and EFS. In multivariate analysis, only the cytogenetic category was predictive of EFS, with the relative risk of treatment failure for the good-, intermediate-, and poor-risk cytogenetic subgroups being 1.0, 1.5, and 3.5, respectively (P = . 004). For adults with primary MDS and sAML, even after BMT, poor-risk cytogenetics are predictive of an unfavorable outcome; novel treatment strategies will be required to improve results with allogeneic BMT in this patient population.

High incidence of extramedullary relapse of AML after busulfan/cyclophosphamide conditioning and allogeneic stem cell transplantation

While allogeneic stem cell transplantation (SCT) is curative for a significant number of patients with AML, relapse of disease within the bone marrow and/or extramedullary (EM) sites following high-dose therapy continues to limit the success of this treatment. Between October 1985 and December 1996, 81 adults underwent allogeneic SCT for de novo AML at our centre. Forty-two patients remain alive and free of leukaemia with a median follow-up of 50 months. The 5-year actuarial event-free survivals (EFS) for all patients and for those undergoing SCT in CR1 or with advanced disease were 46% (95% confidence interval (CI) 34-58%), 63% (CI 46-76%), and 19% (CI 7-36%), respectively. Twenty-two patients relapsed at a median of 8 (range 1.6-54.5) months with the actuarial risk of relapse for all, CR1 and advanced disease patients being 38%, (CI 27-52%), 23% (CI 13-40%) and 68% (CI 46-88%), respectively. Ten patients relapsed at EM sites; six of these (27% of relapses) had an isolated EM relapse at a median of 31 (range 8.5-54) months. Three of the patients with isolated EM relapse survived > or =24 months following relapse and two patients remain disease-free at 29+ and 33+ months. BuCy conditioning followed by allogeneic SCT in AML results in satisfactory EFS although there is a significant risk of late isolated EM relapse.

Admission of bone marrow transplant recipients to the intensive care unit: outcome, survival and prognostic factors

The role of ICU support in BMT patients is controversial. In an era of constrained resources, the use of prognostic factors predicting outcome may be helpful in identifying patients who are most likely (or unlikely) to benefit from this intervention. We attempted to define the survival of patients admitted to ICU following autologous or allogeneic BMT and to identify those factors important in determining patient outcome. A retrospective study of all adult BMT recipients admitted to intensive care over a 6 year study period was performed to determine overall and prognostic indicators of poor outcome. Pre-treatment, pre-ICU admission and ICU admission data were analyzed to identify factors predicting long-term survival. 116 patients were admitted to ICU on 135 separate occasions with the primary reasons for admission being respiratory failure (66%), sepsis associated with hypotension (10%), and cardiorespiratory failure (8%). No pre-ICU characteristics were predictive of survival. Univariate analysis identified the number of support measures required, the need for ventilation or hemodynamic support, the APACHE II score, the year of ICU admission and the serum bilirubin as significant predictors of post-discharge survival. On multivariate analysis the year of ICU admission, the need for hemodynamic support and the serum bilirubin remained significant. The APACHE II score significantly underestimated survival in the 46% of patients with scores less than 35, and could only be used to predict 100% mortality when it exceeded 45. Twenty-three percent of all BMT patients admitted to the ICU and 17% of ventilated patients survived to hospital discharge. Of the 27 patients surviving to leave hospital, 16 remain alive with a median follow-up of 4.2 years and a mean Karnofsky performance status of 90. Although mortality in BMT recipients admitted to ICU is high our results indicate that intensive care support can be lifesaving and that the outcome in patients requiring ventilation and ICU support may not be as poor as has been previously reported. No single variable was identified which could be used to predict futility but patients requiring both hemodynamic support and mechanical ventilation, and those with an APACHE II score greater than 45 have a very poor prognosis and are unlikely to benefit from lengthy ICU support.

Induction failure in de novo acute myelogenous leukemia is associated with expression of high levels of CD34 antigen by the leukemic blasts

The prognostic significance of CD34 antigen expression in acute myelogenous leukemia (AML) is controversial. Most studies to date have reported on CD34 positivity and not the level of antigen present. In this study of 62 patients with de novo AML, 48 (77%) patients were CD34+ in varying levels (0-85 mean channels of fluorescence (MCF)). Forty seven of 62 were treated with combination chemotherapy and 39 (83%) of them achieved complete remission (CR). Patients with CD34- blasts were more likely to achieve CR; however, this trend was not statistically significant (p = .11). On the other hand, patients with higher levels of CD34 antigen on the blasts were less likely to attain CR (p < 0.001, multivariate analysis). The patients who achieved CR expressed lower levels of CD34 (0-57; median 9 MCF) as compared to those who did not achieve CR (15-85; median 30 MCF). Of the other antigens tested, partial or complete absence of CD33 (CD33 absent in > or =25% blasts) correlated with failure to achieve CR (p = 0.0029). These results are in keeping with the hypothesis that more primitive AML blasts with high levels of CD34 are chemoresistant.

Phagocytosis and burst activity of granulocytes and monocytes after stem cell transplantation

In addition to a low number of leukocytes, an impairment of leukocyte function can also contribute to the increased susceptibility to bacterial and fungal infection in marrow transplant recipients. Phagocytosis and oxidative burst activity were measured in patients at various stages after transplant by using assay systems that are based on the quantification of the immunofluorescence of ingested bacteria. Although phagocytosis was normal in most transplant recipents, the oxidative burst of granulocytes was significantly impaired in recipients early after autologous and allogeneic transplants. Patients who underwent tests in later stages after transplant had normal leukocyte function test results. These observations are compatible with the notion that recipients early after bone marrow transplant may be able to phagocytize bacteria readily but that their ability to inactivate them via the oxidative burst might be compromised.

Comparison of natural killer activity of human bone marrow and blood cells in cultures containing IL-2, IL-7 and IL-12

Previous studies have suggested that autologous bone marrow or mobilized peripheral blood progenitor cell transplants activated by prior culture of the cells in IL-2 may capture some of the beneficial graft-versus-leukemia effects obtained with unmanipulated allogeneic, but not autologous, transplants. To investigate ways of improving this approach,we have compared the ability of two other immunomodulating cytokines, IL-7 and IL-12, either alone or in combination with IL-2, to stimulate human bone marrow cells (BMC) or peripheral blood cells (PBC) to acquire the potential to lyse K562 or Daudi cells. For these studies, we measured the cytotoxic activity of BMC or PBC both before and at the end of their incubation with various cytokine(s) using a standard 51-chromium release assay. Results suggest that IL-2 at optimal concentration induces cytotoxicity significantly higher than IL-7 or IL-12 when tested alone. At optimal concentration, the combination of IL-2 and IL-12 showed a synergistic effect for BMC. Such a synergistic effect could be observed for PBC only when suboptimal concentrations of IL-2 were used. In addition, the ability of the hematopoietic cells to reduce the number of K562 cells remaining at the end of various culture periods in the presence of the cytokines was measured. This was made possible by the use of a G418-resistant K562 cell line which could, in contrast to normal human BMC or PBC, form colonies that wer detectable after 1 week in methylcellulose cultures containing the neomycin analog G418. Normal human PBC, stimulated by either IL-7 or IL-12 alone effectively suppressed K562 proliferation in both of these assays, whereas no activity could be detected when BMC were incubated under the same conditions. On the other hand, cells from both sources displayed anti-leukemic activity when incubated with IL-2 and IL-12 together, although IL-2/IL-12-activated PBC suppressed the growth of co-cultivated K562-neor cells about eight-fold more efficiently than IL-2/IL-12-activated BMC. Cryopreservation and subsequent stimulation of BMC and PBC with cytokines did not cause a significant decrease in cytotoxicity or their ability to inhibit the growth of co-cultivated K562 cells compared to fresh cells. However, the synergistic effect observed with the combination of IL-2/IL-12 was no longer detectable for BMC. These results suggest that (1) PBC are superior to BMC with respect to developing effective natural killer (NK) activity after culture in cytokines and that, (2) the combination of IL-2 and IL-12 may be more effective than IL-2 alone to inhibit proliferation/growth of K562 cells.

A cytotoxic NK-cell line (NK-92) for ex vivo purging of leukemia from blood

Myeloablative chemo-/radiotherapy supported by transplantation of autologous bone marrow or blood progenitor cells for acute leukemia, lymphoma, or myeloma continues to be associated with a high relapse rate because of the infusion of malignant stem cells and the lack of an in vivo graft-vs.-leukemia (GVL) effect. Although various methods of purging are established for marrow, purging procedures for blood progenitor cell preparations have not been widely used primarily because of the technical challenges to process a higher number of cells. As a broadly applicable method for immunological purging, we tested whether highly cytotoxic cells from a natural killer (NK) cell line characterized previously (NK-92) could be used for immunological purging of blood preparations. The NK-92 cell line, which was established from a patient with non-Hodgkin's lymphoma, can lyse in vitro a broad range of leukemia, lymphoma, and myeloma cell lines even at very low effector:target (E:T) ratios; this lysis is superior to cytotoxicity obtained from normal peripheral blood mononuclear cells (PBMCs) stimulated for 4 days with interleukin (IL)-2. In an attempt to quantitate the purging achievable with NK-92 cells, normal PBMCs were spiked with 10% K562 cells that had been transfected with the neo(r) marker gene (K562-neo(r). Various numbers of NK-92 cells were then added to the cell mixtures, which were incubated for 4 or 48 hours at 37 degrees C with or without IL-2 (500 U/mL). In order to prevent their proliferation, NK-92 cells were irradiated with 1000 cGy (cesium source). This radiation dose was determined to suppress proliferation of NK-92 cells, but at the same time maintain full cytotoxic activity. After co-culture, the cells were plated in methylcellulose containing 0.8 mg/mL G418. The number of surviving K562-neo(r) colonies was counted under the microscope 7 days later and the results were considered a quantitative readout for the purging efficacy of NK-92 cells. No neomycin-resistant K562 colonies could be detected up to a ratio of NK-92:K562-neo(r) cells of 5:1 (effective NK-92:PBMC ratio of 0.5:1). The presence or absence of IL-2 during the culture period did not affect the results. At this ratio of NK-92:PBMC, the growth of normal clonogenic hematopoietic progenitor cells was not compromised as determined by a standard methylcellulose assay. Considering that K562 is a rapidly proliferating cell line and that the input number of K562 cells (10%) tested here was high, the data suggest that the cytotoxic NK-92 clone (after irradiation to prevent proliferation) could be used effectively for immunological ex vivo purging without compromising hematopoietic cell function.

Site-specific delivery of cytokines in cancer

Cytokines can stimulate the immune response by directly activating effector cells and/or by inducing the release of secondary cytostatic or immunomodulatory molecules. Systemic administration of cytokines, however, often causes numerous side effects in the patient and may not provide a constant level at the tumor site, owing to the variable and generally short half-lifes of cytokines. This has led to the development of novel strategies to deliver cytokines specifically to tumor sites in vivo. These include: the use of monoclonal antibodies directed against tumor antigens; cellular vehicles designed to carry genes to tumor sites; genetically engineered tumor cell vaccines; and targetable viral vectors.

Role of postinduction immunotherapy in acute myeloid leukemia

Because chemotherapy alone does not eliminate clonogenic leukemic cells, disease may recur after induction and consolidation chemotherapy. Studies of patients receiving high-dose chemotherapy supported by bone marrow or blood stem-cell transplantation suggest that immune-mediated effects of transplanted cells help control disease. This antileukemic (graft-versus-leukemia) effect represents several immune reactions. Various approaches to introduce or enhance such immune reactivity in patients with acute myeloid leukemia (AML) are being explored. There is some indication, even in older patients, that immunotherapy is better tolerated than chemotherapy, and efforts are underway to find the most effective treatment for maintaining remission after induction chemotherapy. We have developed a strategy that combines myeloablative chemotherapy with transplantation of autologous stem cells that have been cultured for 1 week in interleukin-2. Low-dose interleukin-2 is also administered for the first week after stem cell infusion. Although all patients developed side effects of fever and fatigue, even older patients tolerated this regimen well. The 3-year disease-free survival rate in a high-risk patient group transplanted in early first remission is 41 percent. Several other compounds are being investigated for their ability to enhance immune reactions after induction chemotherapy for AML. Although immunotherapy cannot eliminate overt leukemia and cytoreductive treatment is still needed initially, immunotherapy may find a place in postinduction management of AML to eliminate minimal (residual) disease or control its growth.

Acute monocytic leukemia: a single institution experience

Using strict FAB criteria, 39 cases of monocytic leukemia were identified in 463 consecutive cases of AML. Patients had a median age of 49 with no sex predominance. Extramedullary disease and hyperleukocytosis were common (54% and 36% of patients respectively). Cytogenetic analysis was successful in 38 of 39 patients; 71% had a cytogenetic abnormality and 42% of these involved chromosome 11; 14 of 16 chromosome 11 abnormalities involved the region of 11q23. Non-chromosome 11 abnormalities tended to occur in older patients and to be associated with a lower platelet count; patients with the translocation 9;11 tended to have a lower white count and a higher incidence of therapy-related leukemia. 35 patients were treated with induction therapy including intensive chemotherapy (n = 33) and allogeneic BMT at presentation (n = 2). Patients who entered remission underwent consolidation chemotherapy, autologous BMT, or allogeneic BMT depending on policies at the time of diagnosis. Of 6 patients who underwent further intensive chemotherapy there is 1 long-term disease-free survivor. 3 of 8 patients undergoing autologous BMT and 2 of 3 patients undergoing allogeneic BMT are long-term disease-free survivors. We conclude that this specific subtype of AML, relatively rare when strict criteria are applied, is associated with unique biologic and clinical features and that the high relapse rate associated with conventional therapy makes new treatment approaches involving stem cell transplantation or immunomodulation necessary.

Introducing graft-versus-leukemia into autologous stem cell transplantation

Although autologous transplantation of stem cells is widely used to support high-dose chemotherapy and radiation for the treatment of hematologic malignancies, relapse is a severe impediment to its wide use, especially in patients receiving transplants for leukemia. This is related to the infusion of leukemic cells in the autograft and the lack of an allogenic graft-versus-leukemia (GVL) effect. This review discusses the current approaches that are under study to introduce a GVL effect into autologous transplantation.

High-dose cyclophosphamide, carmustine (BCNU), and etoposide (VP16-213) with or without cisplatin (CBV +/- P) and autologous transplantation for patients with Hodgkin's disease who fail to enter a complete remission after combination chemotherapy

Patients with Hodgkin's disease (HD) who fail to enter a complete remission after an initial course of combination chemotherapy are usually considered to have an induction failure (IF); this subset of patients has an extremely poor outcome with further conventional therapy. Since 1985, we have entered 30 IF patients into protocols using conditioning with high-dose cyclophosphamide, carmustine (BCNU), and etoposide (VP16-213) with or without cisplatin (CBV +/- P) followed by autologous stem cell transplantation (ASCT) with bone marrow (19 patients), peripheral blood stem cells (PBSCs; 8 patients), or both (3 patients). All except 2 patients had previously received chemotherapy regimens for HD that contained at least 7 drugs, and 9 had received prior radiotherapy (RT). After documentation of IF, the majority of patients received some cytoreductive therapy as specified by protocol (local RT in 9, two cycles of conventional chemotherapy in 2, both modalities in 2, or high-dose cyclophosphamide to enhance PBSC collection in 11) before CBV +/- P. Five treatment-related deaths occurred, all before day 150 posttransplant. Eleven patients have had progressive HD at a median of 6 months (range, 0.1 to 45 months) after ASCT. The actuarial progression-free survival (PFS) at a median follow-up of 3.6 years (range, 0.2 to 8.2 years) is 42% (95% confidence intervals, 21% to 61%). The statistical analysis identified only prior clinical bleomycin lung toxicity as an adverse risk factor for PFS, mainly because of the increased nonrelapse mortality seen in these patients. CBV +/- P and ASCT can produce durable remission in a substantial proportion of IF HD patients who otherwise have a poor survival, and we believed ASCT approaches represent the best therapy currently available for these patients. Additional measures are needed to reduce the primary problem of disease progression despite high-dose chemotherapy and stem cell transplantation.

1994 Consensus Conference on Acute GVHD Grading

Grading acute graft-versus-host disease (GVHD) is usually based on quantification of rash, serum bilirubin and diarrhea. Standard criteria have been developed and used for > 20 years by most transplant centers. However, neither the standard GVHD grading system nor any of several revisions has been validated in the context of GVHD prophylaxis with cyclosporine. The 1994 Consensus Conference on Acute GVHD Grading held in Keystone in January 1994 provided an opportunity to: (1) review data regarding these standard criteria; (2) determine if there are sufficient data to revise these criteria; and (3) develop recommendations for reporting results of GVHD prevention trials. Data were provided for 8249 patients from 12 large transplant centers and 2 transplant registries. Standard GVHD grading criteria were found to distinguish different mortality risks and treatment response rates. Analysis of new data suggested that persistent nausea with histologic evidence of GVHD but no diarrhea be included as stage 1 gastrointestinal GVHD. Additional studies were recommended to evaluate heterogeneity of outcome within GVHD grades prior to making further revisions. To improve comparability between publications, reports of GVHD prevention trials should include an accurate description of the grading system used and should report actuarial rates of grades II-IV and III-IV GVHD corrected for graft failure and potential interventions for early relapse. Additional information should include indications for therapy of GVHD and response.