Generation and characterization of lymphokine-activated killer cells against fresh human leukemia cells

Lymphokine-activated killer (LAK) cells generated from 15 acute leukemia patients in remission showed significant levels of cytotoxicity against Daudi 1A4, a natural killer-resistant cell line. This indicates that lymphocytes of leukemia patients in remission could respond to interleukin-2 to generate conventional LAK cells. However, LAK cells caused lysis of autologous leukemia cells at considerably lower levels in seven out of the 15 patients, with the exception of one case (48.6% cytolysis). None of the remaining eight patients exhibited LAK activity against autologous leukemia cells. On the other hand, patients' LAK could lyse allogeneic leukemia cells including those resistant to autologous LAK. Thus, patients' LAK seem not to be defective in lysis of leukemia cells. In the cold target competition analysis, the binding of patients' LAK to leukemia cells could be inhibited by autologous and allogeneic leukemia cell competitors, implying that almost all leukemia cells could be recognized by patients' LAK. Most LAK cells from normal donors showed significant lysis of allogeneic leukemia cells, but some leukemia cells were found to be resistant to lysis. LAK cells against both leukemia cells and Daudi 1A4 were phenotypically heterogenous, and were predominantly observed in the T3- fraction in the precursor phase. In the effector phase, whereas LAK activity against leukemia cells was also predominantly shown in the T cell-depleted fraction, similar levels of LAK activity against Daudi 1A4 were found in both the T cell-depleted and -enriched fractions.     

Alpha-interferon activated cytotoxic lymphocytes in hairy cell leukemia patients: evaluation of cytotoxic events

To further define the mechanisms responsible for the alpha-interferon (alpha-IFN) efficacy in the treatment of hairy cell leukemia (HCL), experiments were carried out to specify the cytotoxic events taking place following this type of therapy. Although an increased natural killer (NK) activity was demonstrable after alpha-IFN treatment, evidence has been provided that hairy cells were not specifically lysed either by fresh autologous/allogenic NK lymphocytes or by lymphokine activated killer (LAK) cells. This property could not be induced in vitro by alpha-IFN or by interleukin-2 (IL-2). Our data favour the hypothesis that the increase of NK cell activity observed following alpha-IFN therapy has not a direct antineoplastic effect but is likely to be of relevance for a non-specific enhancement of the host immune system. In alpha-IFN treated HCL this latter property may account for the better resistance to infections which usually represents the major cause of mortality in these patients.     

Alpha-interferon structure and natural killer cell stimulatory activity

Expression vectors for human alpha-interferon (Hu-IFN-alpha) J1, a site-specific mutant [Ser116]Hu-IFN-alpha J1, and Hu-IFN-alpha J/C or Hu-IFN-alpha C/J hybrids were constructed and expressed in Escherichia coli. These interferons and others were purified by immunoaffinity chromatography with a monoclonal antibody against human alpha-interferon. Their antiviral activity and ability to stimulate natural killer cell activity were determined in comparison to several other human interferons. These results provide some insight into structure-activity relationships for stimulating natural killer cells and confirm our previous conclusions that antiviral activity cannot be used to predict other activities for an individual IFN-alpha species. The observations suggest that the tertiary structure rather than any specific linear sequence of amino acids regulates the ability of the interferons to stimulate natural killer cell activity.     

Current treatment options in hairy cell leukemia and hairy cell leukemia variant

Hairy cell leukemia (HCL) is a chronic B-cell lymphoproliferative disorder characterized by splenomegaly, pancytopenia and circulating lymphocytes displaying prominent cytoplasmic projections. HCL has usually an indolent course and the patients with asymptomatic disease do not require therapy. Treatment of progressive symptomatic HCL includes a variety of pharmacological approaches such as interferon-alpha (IFN-alpha), pentostatin (DCF) and cladribine (2-CdA), which have significantly improved the disease prognosis. 2-CdA and DCF seem to induce a similar high response rate and a long overall survival. They are also active in relapsed patients. More recently high activity of anti-CD20 monoclonal antibody (rituximab) and anti-CD25 (LMB-2) and anti-CD22 (BL-22) immunotoxins have increased the number of therapeutic options for HCL. Splenectomy may be still indicated in patients with massive, symptomatic splenomegaly or results in severe cytopenia. IFN-alpha may have a place in patients with very severe cytopenia, in HCL in pregnancy and in patients who have failed prior therapy with purine nucleoside analogs. HCL variant (HCL-V) is a distinct clinico-pathological entity which seems to be resistant to IFN-alpha and purine nucleoside analogs - DCF and 2-CdA. However, preliminary observations suggest that monoclonal antibodies - rituximab and BL-22 immunotoxin are highly active in this disorder even refractory to 2-CdA. In this review current therapeutic strategies in HCL and HCL-V are presented.     

Susceptibility of adult acute lymphoblastic leukemia blasts to lysis by lymphokine-activated killer cells

To help understand host-tumor relationships in adult acute lymphoblastic leukemia (ALL) and to better define potential indications for interleukin-2 (IL-2) treatment in this disease, the relationship between the susceptibility of leukemia cells of 22 patients with ALL to lysis by allogeneic lymphokine-activated killer (LAK) cells and characteristics of the leukemia was studied. Lymphocytes were activated in the presence of 1000 U/ml recombinant IL-2 for 5 days. The lysis of ALL cells was studied by the release of 51Cr. The average lysis of ALL cells by control, unactivated lymphocytes was 1.2 +/- 2.4% and by LAK cells 8.9 +/- 8.6%. The susceptibility of leukemic cells to lysis did not correlate with the expression of lymphoid or myeloid differentiation markers or expression of the adhesion molecules CD54 (ICAM-1) and CD58 (LFA-3). Leukemic cells of the FAB I2 subtype were significantly more resistant to lysis than those of the other subtypes (average lysis 1.4 +/- 3.0% versus 12.3 +/- 8.2%, p = 0.003). The susceptibility to lysis did not correlate with the other initial characteristics of the leukemia. The 11 patients in whom 8% or more of leukemic cells were lysed by allogeneic LAK cells survived significantly longer than the 11 patients whose blast cells were less susceptible to lysis (p = 0.04). It is concluded that IL-2 treatment might be of benefit in adult ALL, particularly in non-L2 FAB subtypes and during complete remission to possibly delay relapse and prolong survival.     

Enhancement of human lymphokine-activated killer cell cytolysis and a method for increasing lymphokine-activated killer cell yields to cancer patients

In a continued effort to make interleukin-2/lymphocyte-activated killer (LAK) cell therapy safer and more efficacious for cancer patients, we examined methods of increasing the yields of cells obtained as a final product for reinfusion. Previously, the major cell loss occurred in the Ficoll-Hypaque gradient separation procedure used before cell culture. Therefore, we investigated the necessity of this step. Leukapheresis procedures (n = 105) from 40 different cancer patients showed that the resultant cell product is predominantly mononuclear (lymphocytes and monocytes; greater than 97%) before the gradient purification step. The only cells observed to decrease in percentage as a result of the step were red blood cells (RBC: WBC ratio of 17:1 before purification to 1:3 after purification). Our study showed that the cytolytic potential of unpurified leukapheresis products against the LAK-sensitive line Daudi and the natural killer cell-sensitive line K562 was greater and that the patients received significantly more cells at times of reinfusion if the gradient separation step was eliminated. By additional experiments, we determined that autologous red blood cells enhance the generation of cytolytic LAK cells. This enhancement was greater if the red blood cells were in contact with the mononuclear cells during the time of cell culture. The elimination of the Ficoll-Hypaque purification step not only reduces the time and cost of the cell collection procedures, it also allows us to return to the patients greater numbers of cytolytic LAK cells following the activation period.     

In vitro studies on leukemia cells and T lymphocytes in hairy cell leukemia

Hairy cell leukemia cell lines were established from eight untreated patients using purified B cell growth factor (BCGF) in vitro. These cell lines maintained their original cell surface immunophenotype for about 1 month, after which they began to lose one or more of their characteristic surface antigens. The cell lines also maintained typical hairy cell leukemia morphology for 2-3 months in vitro but later showed an increasing number of multinucleate giant cells that maintained a B cell surface phenotype. The cell lines became independent of exogenously provided BCGF after at least 1 month in vitro and secreted BCGF activity into culture supernatants in most cases. Some cell lines also acquired Epstein-Barr virus nuclear antigen positivity after variable period. Two hairy cell leukemia patients also showed hyperactive T cell responses in vitro and exhibited spontaneous T cell proliferation in culture without exogenously supplied interleukin-2. These T cell lines had the T helper phenotype and secreted significant amounts of T cell-associated lymphokines with BCGF and interleukin-2 activity into culture supernatants.     

Cladribine in hairy cell leukemia

Cladribine results in prolonged complete remissions in most patients wo have HCL. Several studies have indicated that patients who are in complete remission have survivals that are comparable to those of normal age-matched controls. HCL-related mortality is distinctly uncommon. Nevertheless, it is unlikely that cladribine treatment of HCL is curative because MRD is common in the bone marrows of complete responders. Response criteria for HCL include clinical, hematologic, and morphologic criteria, but do not include flow cytometry, immunohistochemical analysis, or molecular studies. More sensitive techniques have been used by Filleul and colleagues to detect MRD. The used clonoegenic probes from the hypervariable regions of the immunoglobulin heavy-chain gene and performed polymerase chain reactions (PCRs) on bone marrow biopsy specimens, All seven patients who were in morphologic complete remission after a single cladribine infusion were PCR positive. These data indicate that cladribine induces protracted remissions but is not necessarily curative. MRD can be detected in most patients when sensitive techniques are used. Persistence of immunohistochemical MRD may predict detected MRD remains to be studied in a large number of patients. Investigators from the University of Pisa in Italy have used a combination of cladribine and rituximab to eradicate MRD in patients who have HCL. Ten patients received treatment with a standard infusion of cladribine. Two patients achieved a complete remission, 6 patients achieved a partial remission, and 2 patients failed to respond. All were PCR positive for the immunoglobulin heavy-chain (IgH) gene product at the completion of cladribine treatment. All 10 patients had achieved a complete hematologic response 2 months after the completion of ritximab therapy. The curative nature of this treatment will require long-term follow-up. Cladribine represents a major therapeutic advance in the treatment of HCL. The prognosis of patients who have HCL has improved greatly with cladribine therapy. Future strategies should address combination therapy with purine analogs and monclonal antibodies. These strategies should address eradication of MRD in an attempt to develop a potentially curative combination treatment program.     

DNA-abnormality in hairy cell leukemia

Spleen and light density peripheral blood leukocytes of 10 hairy cell leukemia (HCL) patients and total leukocytes of one patient and blood donor cells were stained quantitatively for cellular DNA. The DNA content of single cells was measured by flow cytometry (FC) and compared to the DNA content of sheep cells admixed as an internal control. Eight of eleven patients (72 per cent) showed deviations from blood donor DNA content. Two female patients showed increased cellular DNA content, the six male patients had hypodiploid cells. Chromosomal aberrations are therefore likely to exist in the majority of HCL patients. Separation of HCL cells into sheep erythrocyte rosette and non rosette forming cells revealed similar DNA abnormalities in both cell populations, suggesting that the leukemia encompasses cells with B and with T markers.     

Familial hairy cell leukemia

A mother and son are reported who both developed hairy cell leukemia. The mother aged 74 presented with pancytopenia and responded well to splenectomy. Four years later her son aged 48 presented with pancytopenia; splenectomy was less effective but he improved after treatment with interferon-alpha. Histological examination of the splenic tissue in both cases showed changes characteristic of hairy cell leukemia. This is the third report of this rare disease occurring in family members.     

The role of autologous tumor cells in preventing lymphokine-activated killer cell induction in vitro

Peripheral blood lymphocytes (PBL), when cultured in vitro in the presence of autologous irradiated tumor and interleukin-2 (IL-2), become more restricted in the spectrum of their cytotoxicity. The cells continue to exhibit cytotoxicity for autologous tumor cells and major histocompatibility complex (MHC)-concordant allogeneic tumor cells of similar histologic type but not for the natural killer target cell line, K562. Furthermore, the addition of autologous tumor at different time points after the initiation with IL-2 alone of conventional lymphokine-activated killer cell cultures modifies both the specificity and the degree of cytotoxicity of these lymphocytes for tumor targets. By varying the culture conditions it may be possible to generate killer cells that will exhibit similarly enhanced and more restricted antitumor effects in vivo.     

Immunotherapy of cancer with lymphokines and lymphokine-activated killer cells

Our expanding knowledge of the immune system has provided a basis of rationality for immunotherapy. Some non-specific immunotherapy has achieved the status of standard treatment: interferon in hairy cell leukemia and chronic myelogenous leukemia, BCG in bladder cancer, and levamisole in colon cancer adjuvant therapy. Tumor infiltrating lymphocytes, moreover, offer a level of specificity heretofore unknown. Combined with the newly available synthetic cytokines that regulate the normal immune system there is the potential for a major breakthrough in biotherapeutics. Problems remain. We have yet to identify tumor antigens with the precision necessary for effective immunotherapy. Indeed, we have no assurance that tumors will regularly synthesize new antigens. In the broad spectrum of immune deficiency syndromes, we have yet to see an increase in the common epithelial tumors that account for the great bulk of human cancer. This suggests that we still have a great deal more to learn.     

Cell-cell adhesion-independent killing due to lymphokine-activated killer cells against glioblastoma cell lines.

Lymphokine-activated killer (LAK) cells can kill several tumor cells. Their killing activity is generally due to cell-cell adhesion. Cell-cell adhesion of the LAK cells to the target cells is essential for LAK lysis. In this report, however, we describe that the LAK cells can also kill the target cells by cell-cell adhesion-independent killing. Killing occurred after the target cells were exposed to the LAK cells. When the LAK cells were added to glioblastoma cell lines T98G and U373MG (which proliferate by adhering to the bottom of a culture flask), the LAK cells killed them by cell-cell adhesion killing within 4 h (early killing). On the other hand, when small numbers of the LAK cells were added, some of the target cells escaped from the early killing. At 4 and 6 h after the adding the LAK cells, when the LAK cells were discarded from the flask by washing with PBS, the escaped cells still adhered and were alive. However, they ultimately died over the next 24-96 h (late killing). The late killing was the cell-cell adhesion-independent killing, because it occurred after the LAK cells were removed. In this killing, numerous granules and vacuoles appeared in the cytoplasm of the cells. The vacuoles enlarged and then the cells died. The cell death was different from apoptosis, because the nucleus was intact until the late stage and no DNA fragment laddering in the degenerated cells was recognized. The vacuoles were stained with acid phosphatase and the cell death was inhibited with 3-methyladenine (an inhibitor of lysosome), suggesting that the late killing may be autophagic cell death due to activated lysosome. Induction of late killing in tumor cells using the LAK cells may become one approach for cancer therapy.     

Fludarabine therapy in hairy cell leukemia

This study evaluated the efficacy of fludarabine, a new adenine nucleoside analogue, in typical and variant forms of hairy cell leukemia (HCL). Two patients with HCL and one patient with a variant form of HCL (HCL-variant) with resistant or progressive disease with prior treatments were studied. Fludarabine (30 mg/m2) was administered intravenously over 30 minutes daily for 5 days every month. Two patients (one with HCL and one with HCL-variant) achieved partial responses; the third patient had a minor response. This is the first report of encouraging activity of fludarabine in typical and variant forms of HCL. Further experience with fludarabine in these disorders is indicated.