Antibody landscape of C57BL/6 mice cured of B78 melanoma via immunotherapy

Hoefges et al. utilized a whole-proteome peptide array approach to show that C57BL/6 mice develop a large repertoire of antibodies against linear peptide sequences of their melanoma after receiving a curative immunotherapy regimen consisting of radiation and an immunocytokine. Antibodies can play an important role in innate and adaptive immune responses against cancer, and in preventing infectious disease. Flow cytometry analysis of sera of immune mice that were previously cured of their melanoma through a combined immunotherapy regimen with long-term memory showed strong antibody-binding against melanoma tumor cell lines. Using a high-density whole-proteome peptide array, we assessed potential protein-targets for antibodies found in immune sera. Sera from 6 of these cured mice were analyzed with this high-density, whole-proteome peptide array to determine specific antibody-binding sites and their linear peptide sequence. We identified thousands of peptides that were targeted by 2 or more of these 6 mice and exhibited strong antibody binding only by immune, not naive sera. Confirmatory studies were done to validate these results using 2 separate ELISA-based systems. To the best of our knowledge, this is the first study of the "immunome" of protein-based epitopes that are recognized by immune sera from mice cured of cancer via immunotherapy.

In situ Vaccine Plus Checkpoint Blockade Induces Memory Humoral Response

In a syngeneic murine melanoma (MEL) model, we recently reported an in situ vaccination response to combined radiation (RT) and intra-tumoral (IT) injection of anti-GD2 hu14. 18-IL2 immunocytokine (IC). This combined treatment resulted in 71% complete and durable regression of 5-week tumors, a tumor-specific memory T cell response, and augmented response to systemic anti-CTLA-4 antibody checkpoint blockade. While the ability of radiation to diversify anti-tumor T cell response has been reported, we hypothesize that mice rendered disease-free (DF) by a RT-based ISV might also exhibit a heightened B cell response. C57BL/6 mice were engrafted with 2 × 10⁶ GD2+ B78 MEL and treated at a target tumor size of ~200 mm³ with 12 Gy RT, IT-IC on day (D)6-D10, and anti-CTLA-4 on D3, 6, and 9. Serum was collected via facial vein before tumor injection, before treatment, during treatment, after becoming DF, and following rejection of subcutaneous 2 × 10⁶ B78 MEL re-challenge on D90. Flow cytometry demonstrated the presence of tumor-specific IgG in sera from mice rendered DF and rejecting re-challenge with B78 MEL at D90 after starting treatment. Consistent with an adaptive endogenous anti-tumor humoral memory response, these anti-tumor antibodies bound to B78 cells and parental B16 cells (GD2-), but not to the unrelated syngeneic Panc02 or Panc02 GD2+ cell lines. We evaluated the kinetics of this response and observed that tumor-specific IgG was consistently detected by D22 after initiation of treatment, corresponding to a time of rapid tumor regression. The amount of tumor-specific antibody binding to tumor cells (as measured by flow MFI) did not correlate with host animal prognosis. Incubation of B16 MEL cells in DF serum, vs. naïve serum, prior to IV injection, did not delay engraftment of B16 metastases and showed similar overall survival rates. B cell depletion using anti-CD20 or anti-CD19 and anti-B220 did not impact the efficacy of ISV treatment. Thus, treatment with RT + IC + anti-CTLA-4 results in adaptive anti-tumor humoral memory response. This endogenous tumor-specific antibody response does not appear to have therapeutic efficacy but may serve as a biomarker for an anti-tumor T cell response.

Antitumor Activity and Tolerability of hu14.18-IL2 with GMCSF and Isotretinoin in Recurrent or Refractory Neuroblastoma: A Children's Oncology Group Phase II Study

PURPOSE

Combining anti-GD2 (disialoganglioside) mAb with GM-CSF, IL2, and isotretinoin is now FDA-approved for high-risk neuroblastoma minimal residual disease (MRD) therapy. The humanized anti-GD2 antibody conjugated to IL2 (hu14.18-IL2) has clinical activity in neuroblastoma and is more effective in neuroblastoma-bearing mice than antibody and cytokine given separately. We therefore evaluated the safety, tolerability, and antitumor activity of hu14.18-IL2 given with GM-CSF and isotretinoin in a schedule similar to standard MRD therapy.

PATIENTS AND METHODS

Hu14.18-IL2 was given at the recommended phase II dose of 12 mg/m²/day on days 4-6 of a 28-day cycle with GM-CSF (250 mg/m²/dose, days 1-2 and 8-14) and isotretinoin (160 mg/m²/day, days 11-25). Tolerability was determined on the basis of the number of unacceptable toxicities observed. Response was evaluated separately for patients with disease measurable by standard radiologic criteria (stratum 1), and for patients with disease evaluable only by I¹²³-metaiodobenzylguanidine (I¹²³-MIBG) scan and/or bone marrow histology (stratum 2).

RESULTS

Fifty-two patients with recurrent or refractory neuroblastoma were enrolled; 51 were evaluable for toxicity and 45 were evaluable for response. Four patients had unacceptable toxicities, well below the protocol-defined rule for tolerability. Other grade 3 and 4 nonhematologic toxicities were expected and reversible. No responses were seen in stratum 1 (n = 14). In stratum 2 (n = 31), 5 objective responses were confirmed by central review (3 complete, 2 partial).

CONCLUSIONS

Hu14.18-IL2 given in combination with GM-CSF and isotretinoin is safe and tolerable. Patients with MIBG and/or bone marrow-only disease had a 16.1% response rate, confirming activity of the combination.

In Vivo Effects of Multiple Cycles of Recombinant Interleukin-2 (IL2) on Peripheral Granulocyte-macrophage Hematopoietic Progenitors Circulating in the Blood of Cancer Patients

The numbers of peripheral blood (PB) granulocyte-macrophage colony forming units (CFU-GM) were evaluated in five patients treated with multiple weekly cycles of recombinant interleukin-2 (IL2). A 4.5-12 fold increase in the number of CFU-GM was evident within 8 days after the beginning of the treatment. The maximal increase in the absolute numbers of CFU-GM/ml blood caused by the IL2 treatment, ranged from 14 to 57 times the baseline values and was reached after two or three cycles of IL2. IL2-activated PBMC, added in vitro to the PBMC of a normal donor did not modify the number of CFU-GM present in the donor PBMC. CFU-GM were also recovered from frozen samples of in vivo IL2-activated PBMC.

Soluble interleukin-2 receptor α activation in a Children's Oncology Group randomized trial of interleukin-2 therapy for pediatric acute myeloid leukemia

PURPOSE

To assess associations of soluble IL-2 receptor alpha (sIL-2rα) concentration with outcomes in pediatric acute myeloid leukemia (AML) in a phase 3 trial of IL-2 therapy.

PROCEDURES

We randomized 289 children with AML in first remission after intensive chemotherapy to receive IL-2 infused on days 0-3 and 8-17 (IL-2 group) or no further therapy (AML control group). We measured sequential serum sIL-2rα concentrations in both groups before, during and after therapy in both groups and in reference controls without AML.

RESULTS

Before treatment, mean sIL-2rα concentrations were similar in the IL-2 group and AML controls, but significantly higher than in reference controls. Both AML groups experienced reduction in sIL-2rα concentration after chemotherapy. Thereafter in the IL-2 group, mean sIL-2rα concentration increased from 2,669 pg/ml before IL-2 to 15,534 pg/ml on day 4 (P < 0.001) and 10,585 pg/ml on day 18 (P < 0.001). In the control group sIL-2rα concentration did not change after 28 days of follow-up. Five-year disease-free survival (DFS) was 51% in the IL-2 group and 58% in the controls (P = 0.489) and overall survival was 70% and 73%, respectively (P = 0.727).

CONCLUSION

SIL-2rα concentration was elevated in AML at diagnosis and tended to normalize after chemotherapy. IL-2 infusion significantly increased sIL-2rα concentration, but did not improve DFS or survival in pediatric AML. Furthermore, sIL-2rα concentration was not predictive of outcome before, during or after treatment for AML.

Genotypes of NK cell KIR receptors, their ligands, and Fcγ receptors in the response of neuroblastoma patients to Hu14.18-IL2 immunotherapy

Response to immunocytokine (IC) therapy is dependent on natural killer cells in murine neuroblastoma (NBL) models. Furthermore, killer immunoglobulin-like receptor (KIR)/KIR-ligand mismatch is associated with improved outcome to autologous stem cell transplant for NBL. Additionally, clinical antitumor response to monoclonal antibodies has been associated with specific polymorphic-FcγR alleles. Relapsed/refractory NBL patients received the hu14.18-IL2 IC (humanized anti-GD2 monoclonal antibody linked to human IL2) in a Children's Oncology Group phase II trial. In this report, these patients were genotyped for KIR, HLA, and FcR alleles to determine whether KIR receptor-ligand mismatch or specific FcγR alleles were associated with antitumor response. DNA samples were available for 38 of 39 patients enrolled: 24 were found to have autologous KIR/KIR-ligand mismatch; 14 were matched. Of the 24 mismatched patients, 7 experienced either complete response or improvement of their disease after IC therapy. There was no response or comparable improvement of disease in patients who were matched. Thus KIR/KIR-ligand mismatch was associated with response/improvement to IC (P = 0.03). There was a trend toward patients with the FcγR2A 131-H/H genotype showing a higher response rate than other FcγR2A genotypes (P = 0.06). These analyses indicate that response or improvement of relapsed/refractory NBL patients after IC treatment is associated with autologous KIR/KIR-ligand mismatch, consistent with a role for natural killer cells in this clinical response.

Antitumor effect of resveratrol and potential for combination with immunotherapy (B205)

Resveratrol (3, 4′, 5 – trihydroxy-trans-stilbene) is a natural compound currently being investigated for possible health promoting activities. It has antitumor effects on various types of cancer cells in vitro and in some animal models. Clement et al (Blood, 92:3, 996–1002, 1998) demonstrated that trans-resveratrol (t-RV) induced apoptotic cell death in HL60 leukemia cells and T47D breast cancer cells in vitro at doses which were minimally toxic to peripheral blood lymphocytes (PBMC). Additional studies on the effect of t-RV on the immune system have found t-RV to be immunosuppressive in vitro in a time and dose-dependent manner, but not suppressive in vivo. We are currently examining the ability of t-RV to be combined with immunotherapy to treat cancer. Using proliferative and cytotoxicity assays we are defining a dose in vitro and a regimen in vivo that does not suppress the immune system and has additive or synergistic anti-tumor effects when combined with immunotherapy. Our data suggest that t-RV inhibits the proliferation of K562, a natural killer sensitive target, and M21, a human melanoma cell line, in a dose dependent fashion. In addition, t-RV inhibits the ability of PHA to stimulate proliferation of PBMC. Furthermore, t-RV suppresses proliferation of cells already activated with PHA. These responses were dose dependent. We are examining the effects of t-RV on target and effector cells in cell mediated and antibody dependent cytotoxicity assays. These investigations may shed light on ways of combining t-RV with immunotherapy to treat cancer.

Antibody-directed, effector cell-mediated tumor destruction

Preclinical and clinical development of antitumor strategies using mAbs are showing antitumor efficacy in animal models and in some clinical settings. Preclinical models suggest that mAb treatment would be most effective when provided in the minimal residual disease setting and can involve mAbs in a variety of roles. In murine models, the combination of mAbs with recombinant cytokines, such as IL-2, IL-12, or GM-CSF, can augment the immunologic effect of the mAbs by activating effector cell functions. Efficacy appears to be greatest when the mAb can recruit the effector cells of the host's immune system into helping in the mediation of the antitumor effect. Clinical testing of these concepts is under way.

A phase Ib/II trial of granulocyte-macrophage-colony stimulating factor and interleukin-2 for renal cell carcinoma patients with pulmonary metastases: a case of fatal central nervous system thrombosis

BACKGROUND

Interleukin-2 (IL-2) and granulocyte-macrophage-colony stimulating factor (GM-CSF) are cytokines with nonoverlapping pleiotropic effects. In a prior Phase Ib study, this combination of agents exhibited antitumor effects in the lungs of four of eight patients with renal cell carcinoma and pulmonary metastases. We conducted this Phase Ib/II trial to determine the response rate of renal cell carcinoma patients with pulmonary metastases treated with continuous infusion IL-2 plus GM-CSF.

METHODS

Patients with renal cell carcinoma and pulmonary metastases were treated with 1.5, 2.25, or 4.5 x 10(6) IU/m(2)/day 96-hour continuous infusion IL-2 on Days 1-4, 8-11, and 15-18, and 1.25, 2.25, or 2.5 microg/kg/day GM-CSF on Days 8-19.

RESULTS

Sixteen patients were treated per protocol, 14 of whom could be evaluated for disease progression. None of these 14 patients had >50% shrinkage of either total tumor burden or pulmonary metastasis. One patient developed Grade 5 neurotoxicity. Autopsy revealed acute multifocal cerebral venous thrombosis as well as acute subdural and subarachnoid hemorrhage.

CONCLUSIONS

The combination of IL-2 and GM-CSF may be associated with marked morbidity and, as in one case in this study, mortality. No significant antitumor activity was appreciated. Thus, the combination of IL-2 and GM-CSF, when administered at this dose and according to this schedule, does not appear to be active in renal cell carcinoma and is associated with significant toxicities. Further studies using this combination of agents should only be undertaken with extreme caution and particular attention to neurotoxicity.

Pharmacokinetics and stability of the ch14.18-interleukin-2 fusion protein in mice

The fusion protein formed from ch14.18 and interleukin-2 (ch14.18-IL-2), shown to exhibit antitumor efficacy in mouse models, consists of IL-2 genetically linked to each heavy chain of the ch14.18 chimeric anti-GD2 monoclonal antibody. The purpose of this study was to determine the pharmacokinetics of ch14.18-IL-2 in mice and assess its stability in murine serum. Following i.v. injection, the fusion protein was found to have a terminal half-life of 4.1 h. Detection of IL-2 following injection of the ch14.18-IL-2 fusion protein showed a similar half-life, indicating that the fusion protein prolongs the circulatory half-life of IL-2. Detection of human IgG1 following injection of ch14.18-IL-2 showed a terminal half-life of 26.9 h. These data suggested that the native fusion protein is being altered in vivo, resulting in a somewhat rapid loss of detectable IL-2, despite prolonged circulation of its immunoglobulin components. In vitro incubation of the ch14.18-IL-2 fusion protein in pooled mouse serum at 37 degrees C for 48 h resulted in a loss of its IL-2 component, as detected in enzyme-linked immunosorbent assay systems and in proliferation assays. Polyacrylamide gel electrophoresis and Western blot analysis of the fusion protein incubated in mouse serum at 37 degrees C indicated that the ch14.18-IL-2 is cleaved, resulting in a loss of the 67-kDa band (representing the IL-2 linked to the IgG1 heavy chain) and the detection of a band of more than 50 kDa, slightly heavier than the IgG1 heavy chain itself. This suggests that the fusion protein is being cleaved in vitro within the IL-2 portion of the molecule. These studies show that (1) ch14.18-IL-2 prolongs the circulatory half-life of IL-2 (compared to that of soluble IL-2) and (2) the in vivo clearance of the fusion protein occurs more rapidly than the clearance of the ch14.18 antibody itself, possibly reflecting in vivo cleavage within the IL-2 portion of the molecule, resulting in loss of IL-2 activity.

Specific enzyme-linked immunosorbent assays for quantitation of antibody-cytokine fusion proteins

Preliminary testing has shown in vitro and in vivo that antitumor activity can be obtained with fusion proteins linking tumor-reactive monoclonal antibodies to cytokines, such as granulocyte-macrophage colony-stimulating factor or interleukin 2 (IL-2). Preclinical and clinical testing of these reagents requires their in vitro and in vivo quantitation and pharmacokinetic evaluation. We have focused on the detection of a fusion protein which links one human IL-2 molecule to the carboxy terminus of each heavy chain of the tumor-reactive human-mouse chimeric anti-GD2 antibody, ch14.18. We have developed enzyme-linked immunosorbent assays (ELISAs) to evaluate intact tumor-reactive fusion proteins. By these ELISAs we can reliably measure nanogram quantities of intact ch14.18-IL-2 fusion protein and distinguish the intact protein from its components (ch14.18 and IL-2) in buffer, mouse serum, and human serum with specificity and reproducibility. The measurement of intact ch14.18-IL-2 fusion protein is not confounded by free IL-2 or free ch14.18 when 100 ng or less of total immunoglobulin per ml is used during the assay procedure. Our results indicate that these ELISAs are suitable for preclinical and clinical testing and with slight modifications are applicable to the analysis of a variety of other fusion proteins.

Distinct clinical and laboratory activity of two recombinant interleukin-2 preparations

Interleukin-2 (IL-2) is a potent lymphokine that activates natural killer cells, T cells, and other cells of the immune system. Several distinct recombinant human IL-2 preparations have shown antitumor activity, particularly for renal cell cancer and melanoma. Somewhat distinct immune and clinical effects have been noted when different IL-2 preparations have been tested clinically; however, the regimens and doses used were not identical. To compare these more directly, we have evaluated two clinical recombinant IL-2 preparations in vitro and in vivo using similar regimens and similar IUs of IL-2. We used the Food and Drug Administration-approved, commercially available Chiron IL-2 and the Hoffmann LaRoche (HLR) IL-2 supplied by the National Cancer Institute. Using equivalent IUs of IL-2, we noted quantitative differences in vitro and in vivo in the IL-2 activity of these two preparations. In patients receiving comparable IUs of the two preparations, HLR IL-2 induced the release of more soluble IL-2 receptor alpha into the serum than Chiron IL-2. In addition, more toxicities were noted in patients receiving 1.5 x 10(6) IU of HLR IL-2 than were seen in patients treated with 1.5 x 10(6) or even 4.5 x 10(6) IU of Chiron IL-2. These toxicities included fever, nausea and vomiting, and hepatic toxicity. In vitro proliferative assays using IL-2-dependent human and murine cell lines indicated that the IU of HLR IL-2 was more effective than Chiron IL-2 at inducing tritiated thymidine incorporation. Using flow cytometry, we also found quantitative differences in the ability of these two preparations to bind to IL-2 receptors. These findings indicate that approximately 3-6 IU of Chiron IL-2 are required to induce the same biological effect as 1 IU of HLR IL-2.

Differential quantitative effects of interleukin (IL)-2 and IL-15 on cytotoxic activity and proliferation by lymphocytes from patients receiving in vivo IL-2 therapy

Lymphocytes from patients receiving in vivo interleukin (IL)-2 therapy possess enhanced in vitro proliferative and cytotoxic responses to IL-2. The cells from these patients that respond to exogenous IL-2 are CD56+ natural killer cells expressing intermediate-affinity IL-2 receptor betagamma(c) complexes. Because IL-15 activates cells via these same betagamma(c) receptors, we hypothesized that IL-15 would also activate lymphocytes from patients treated with in vivo IL-2 therapy and therefore that IL-15 might potentially be useful as an immunotherapeutic agent alone or in combination with IL-2. We report here that peripheral blood mononuclear cells (PBMCs) from patients receiving in vivo IL-2 therapy do proliferate in response to IL-15. However, a greater dose of IL-15 is needed to reach the same level of proliferation stimulated by IL-2. The EC50 for IL-2 is 0.21 +/- 0.04 nM (mean +/- SE; n = 18), whereas the EC50 for IL-15-stimulated proliferation is 1.16 +/- 0.16 nM (n = 18). In contrast to the proliferative response, equivalent doses of IL-2 and IL-15 stimulate patient PBMCs to mediate similar levels of cytotoxicity against Daudi, K562, and LA-N-5 tumor targets. Notably, low concentrations of IL-15 that do not stimulate a substantial proliferative response (e.g., 1.0 ng/ml) do boost PBMCs to mediate cytotoxicity against these tumor targets. These distinct dose-response curves for proliferation compared to cytotoxicity suggest that IL-15 should be evaluated for its potential as an immunotherapeutic agent to treat cancer, particularly in regimens providing doses that might minimize the proliferative response (associated with cytokine release and toxic side effects) while maintaining the cytolytic antitumor response.

Combination therapy with interleukin-2 and antitumor monoclonal antibodies

PURPOSE

Administration of recombinant interleukin-2 (rIL-2) causes activation of natural killer (NK) cells, which express CD16, the Fc receptor gamma III (Fc gamma III), and can mediate antibody-dependent cellular cytotoxicity (ADCC). In an effort to generate a more directed antitumor response by rIL-2-activated NK cells, we have investigated combination therapy with rIL-2 plus the antitumor monoclonal antibody (mAb) 14. G2A and its molecular derivatives, which react strongly with the GD2 ganglioside expressed on melanoma, neuroblastoma, and certain other tumors.

PATIENTS AND METHODS

The initial trial of this therapeutic strategy involved 33 evaluable neuroblastoma patients who received rIL-2 by continuous intravenous infusion in combination with the murine 14.G2A mAb. A follow-up phase I study was conducted in 24 evaluable adult melanoma patients with a mouse/human chimeric mAb (ch14.18). The ch14.18 mAb has subsequently been investigated in combination with rIL-2 and granulocyte-macrophage colony-stimulating factor in neuroblastoma patients following autologous bone marrow transplantation. Based on preclinical data, the administration of rIL-2 plus mAbs may be more effective in patients with minimal residual disease. An alternative strategy to induce ADCC has also been investigated because of the finding that many NK cells fail to express Fc gamma III. The IL-2-ch14.18 fusion protein has been tested in preclinical studies for its ability to induce an effective antitumor response and is currently being evaluated for future clinical testing.

RESULTS

Based on in vitro assays, the serum of patients treated with rIL-2 plus either 14.G2A or ch14.18 mAbs demonstrated sufficient levels of antibody and NK cell activity to mediate effective ADCC; however, many patients developed antibodies against the administered murine and chimeric mAbs, leading to allergic complications. Concurrent administration of rIL-2 and ch14.18 resulted in a lower incidence of anti-ch14.18 antibodies. The IL-2-ch14.18 fusion protein has demonstrated dramatic antitumor effects in murine models.

DISCUSSION

These studies have demonstrated the feasibility of concurrent administration of rIL-2 with the mouse/human chimeric ch14.18 mAb. Although the early pilot studies were conducted in patients with bulky disseminated disease, this approach may be more effective in patients with minimal residual disease. Further refinement of the reagents and phase II and III trials will be necessary to evaluate fully the safety and efficacy of this immunotherapeutic approach.

Phase IB trial of chimeric antidisialoganglioside antibody plus interleukin 2 for melanoma patients

We conducted a Phase IB trial of antidisialoganglioside chimeric 14. 18 (ch14.18) antibody and interleukin 2 (IL-2) to determine the maximal tolerated dose (MTD), immunological effects, antitumor effects, and toxicity of this treatment combination. Twenty-four melanoma patients received immunotherapy with ch14.18 antibody and a continuous infusion of Roche IL-2 (1.5 x 10(6) units/m2/day) given 4 days/week for 3 weeks. The ch14.18 antibody (dose level, 2-10 mg/m2/day) was scheduled to be given for 5 days, before, during, or following initial systemic IL-2 treatment. The ch14.18 MTD was 7.5 mg/m2/day, and 15 patients were treated with the ch14.18 MTD. Immunological effects included the induction of lymphokine-activated killer activity and antibody-dependent cellular cytotoxicity by peripheral blood mononuclear cells. In addition, serum samples obtained following ch14.18 infusions were able to facilitate in vitro antibody-dependent cellular cytotoxicity. Antitumor activity included one complete response, one partial response, eight patients with stable disease, and one patient with >50% decrease of hepatic metastases in the face of recurrence of a s.c. lesion. Dose-limiting toxicities were a severe allergic reaction and weakness, pericardial effusion, and decreased performance status. Most patients treated at the MTD had abdominal, chest, or extremity pain requiring i.v. morphine. One patient had an objective peripheral neuropathy. This IL-2 and ch14.18 treatment combination induces immune activation in all patients and antitumor activity in some melanoma patients. We are attempting to enhance this treatment approach by addition of the anti-GD3 R24 antibody to this IL-2 and ch14.18 regimen.

A phase I/IB trial of murine monoclonal anti-GD2 antibody 14.G2a plus interleukin-2 in children with refractory neuroblastoma: a report of the Children's Cancer Group

BACKGROUND

The murine monoclonal antibody (MoAb) 14.G2a recognizes GD2, a disialoganglioside expressed in tumors of neuroectodermal origin, and facilitates antibody dependent cellular cytotoxicity (ADCC) in vitro. When given in vivo, interleukin-2 (IL-2) can increase ADCC by enhancing the activity and number of circulating lymphocytes.

METHODS

Thirty-three pediatric patients with GD2 positive malignancies, ranging in age from 2 to 17 years (median, 9.9 years), received IL-2 and 14.G2a in this Phase I/IB study of the Children's Cancer Group (CCG) and were monitored for toxicities and response to therapy. Seven of these patients also received granulocyte-macrophage-colony stimulating factor.

RESULTS

The maximum tolerated dose (MTD) of 14.G2a with IL-2 was 15 mg/m2/day. The most prevalent Grade 3-4 toxicities were generalized pain (n = 14 [42%]) and fever without documented infection (n = 17 [52%]). IL-2 was thought to be the causative agent in most cases of fever. Toxicities attributed to 14.G2a included pain, allergic or anaphylactic reactions, and rash. Human antimouse antibodies were demonstrated in 9 of 21 evaluated patients. One patient with neuroblastoma had a partial response, and one patient with osteosarcoma had a complete response. Immunocytology demonstrated that the number of neuroblastoma cells in bone marrow decreased in three patients.

CONCLUSIONS

The murine MoAb 14.G2a was well tolerated at the MTD and appeared to have some antitumor activity. Further development of this approach will involve additional engineered forms of the antibody as well as testing in the adjuvant and minimal residual disease setting.

Activation of human effector cells by a tumor reactive recombinant anti-ganglioside GD2 interleukin-2 fusion protein (ch14.18-IL2)

Cytotoxic effector cells interact with target cells through various mechanisms. CTLs use the antigen-specific T cell receptor, whereas Fc receptor-positive natural killer cells use this receptor to interact with antibody-coated target cells. We evaluated the tumor-binding and lymphocyte-activating capability of a recombinant fusion protein consisting of a tumor-selective human/mouse chimeric anti-ganglioside GD2 antibody (ch14.18) and recombinant human interleukin-2 (IL2) (ch14.18-IL2). This fusion protein bound specifically to GD2-positive melanoma and neuroblastoma tumor cell lines, and its IL2 component stimulated in vitro proliferation of an IL2-dependent cell line, as well as peripheral blood mononuclear cells, in healthy control individuals and in cancer patients receiving continuous infusion of IL2. The IL2 presented by the fusion protein, when bound to tumor cells, induced proliferation of IL2-responsive cells as well as a comparable amount of soluble IL2 did. This suggests that localization of IL2 at the site of contact between tumor and effector cells is an effective way of presenting this cytokine to IL2-responsive cells. The ch14.18-IL2 fusion protein also mediated antibody-dependent cellular cytotoxicity with Fc receptor-positive effector cells to an extent similar to ch14.18. These results, together with those of previous studies documenting antitumor efficacy against human tumor xenografts in SCID mice and GD2-positive murine tumors in immunocompetent syngeneic mice, suggest that the ch14.18-IL2 fusion protein should be tested in Phase I and II trials in patients with GD2-positive tumors.

Systemic interleukin-2 modulates the anti-idiotypic response to chimeric anti-GD2 antibody in patients with melanoma

The induction of human antimouse antibodies (HAMA) and human anti-idiotypic (anti-Id) responses in cancer patients receiving therapeutic monoclonal antibody (mAb) may limit the effectiveness of the administered mAb. This report evaluates the influence of systemic interleukin-2 (IL-2) on the anti-Id response to anti-disialoganglioside (anti-GD2) antibody given as treatment for patients with melanoma. Twenty-eight patients with melanoma received combined immunotherapy with anti-GD2 antibody and IL-2 at 1.5 x 10(6) U/m2/day given 4 days/week. The anti-GD2 antibody [murine 14.G2a mAb; dose levels of 2-5 mg/m2/day (4 patients); or human-mouse chimeric 14.18 (ch14.18) antibody; dose levels of 2-10 mg/m2/day (24 patients)] was scheduled to be given for 5 days either before, during, or after initial systemic IL-2 treatment. All four patients who received murine 14.G2a developed HAMA anti-isotype antibodies (660-1,000 ng/ml) as well as measurable anti-Id antibodies. All three patients who received initial treatment with ch14.18 alone developed a strong anti-Id antibody response after IL-2 was started 1 week later. The serum level of anti-Id antibody decreased during subsequent ch14.18 infusions, suggesting that the anti-Id antibody may be binding the administered ch14.18. In contrast, measurable anti-Id antibody was detected in only 3 of 14 patients who received IL-2 before, during, and after initial ch14.18 administration. Two of four patients receiving systemic IL-2 before and during initial ch14.18 infusions, and two of three patients receiving systemic IL-2 concurrent with initial ch14.18 infusions developed anti-Id antibodies. These data suggest that the anti-Id response to chimeric anti-GD2 antibody is influenced by the timing of systemic IL-2 in relation to antibody administration and can be suppressed by systemic treatment with IL-2 given before, during, and after the antibody administration.

Anti-renal-cell carcinoma chimeric antibody G250 facilitates antibody-dependent cellular cytotoxicity with in vitro and in vivo interleukin-2-activated effectors

Renal cell carcinoma (RCC) is relatively resistant to chemotherapy and radiotherapy, whereas treatment with biologics has achieved limited success. Although monoclonal antibodies able to recognize human RCC have been identified, most induce little complement-dependent cytotoxicity or antibody-dependent cellular cytotoxicity (ADCC), and thus are of limited potential as therapeutic modalities in their natural conformation. We evaluated a human/ mouse chimeric derivative of the previously described G250 murine monoclonal antibody (mAb), reactive with RCC, to identify a reagent for potential immunotherapy. This chimeric antibody (ch-G250) is composed of the murine variable region from the G250 mAb, which recognizes a tumor-associated antigen expressed on 95% of primary and 86% of metastatic renal cell carcinomas. The constant region of the ch-G250 is comprised of the human IgG1 isotype domains. This chimeric antibody does not bind to normal renal tissue or other normal human tissues, with the exception of gastric mucosal cells and large bile-duct epithelium. Clinical radiolocalization studies have demonstrated the relative tumor-targeting potential of this radiolabeled antibody. This ch-G250 antibody facilitated potent ADCC against several RCC lines when using in vitro and in vivo interleukin-2 (IL-2)-activated peripheral blood mononuclear cells obtained from healthy control donors and patients with cancer, respectively. This lymphocyte-mediated ADCC was specific for RCC cells recognized by the ch-G250 antibody. Using flow cytometry, we found that the level of ADCC was directly related to the degree of binding of ch-G250 to the renal cell target. These in vitro data suggest that this antibody may improve efficacy of IL-2 therapy by targeting cytokine-activated effector cells directly to the tumor and facilitating in vivo ADCC. Clinical studies combining this chimeric antibody with IL-2 treatment will be needed to test the antitumor effects of this ADCC effect in vivo.

Clinical and immunological effects of granulocyte-macrophage colony-stimulating factor coadministered with interleukin 2: a phase IB study

Interleukin 2 (IL-2) and granulocytes-macrophage colony-stimulating factor (GM-CSF) are activators of the lymphocyte and granulocyte/macrophage series, respectively. We conducted a phase IB trial to identify the maximally tolerated dose and to assess immunological effects of the combination. Thirty-four patients with incurable cancers received 2.5, 5, or 10 microgram/kg GM-CSF s.c. either before or concurrently with 1.5 or 3.0 million units/m2/day IL-2. The most common laboratory and clinical side effects included an elevation of the total WBC or eosinophil count due to GM-CSF, and constitutional symptoms due to IL-2. Grade 3 or 4 toxicities included hypotension, thrombocytopenia, elevations in aspartate aminotransferase or bilirubin, renal toxicity, gastrointestinal hemorrhage, arrhythmia, and constitutional symptoms. Two patients receiving 5.0 microgram/kg GM-CSF plus concurrent 3.0 million units IL-2 experienced dose-limiting grade 3 or 4 neurological toxicity, which reversed almost completely. An increase in the serum-soluble IL-2 alpha chain receptor was observed with administration of GM-CSF, IL-2, or the combination. IL-2 therapy enhanced lymphokine-activated killer activity, antibody-dependent cellular cytotoxicity, and lymphocyte activation, with increased CD16 and CD56 expression. GM-CSF increased expression of human leukocyte antigen DR on peripheral blood monocytes and decreased surface expression of CD16 on circulating monocytes and polymorphonuclear cells. Lymphokine-activated killer activity and CD16 expression on monocytes and lymphocytes and CD56 expression on lymphocytes were significantly lower in patients receiving GM-CSF simultaneously with IL-2 than in patients receiving the sequential treatment. Antitumor activity was observed in the lungs of four of eight renal cell carcinoma patients with pulmonary metastases treated with concurrent GM-CSF and IL-2. Although no or minimal shrinkage was observed in the patients' large primary tumors, these results warrant further study. The recommended initial Phase II dose and schedule is 1.25 microgram/kg/day GM-CSF, given concurrently with 1.5 million Roche units/m2/day (4.5 x 10(6) international units/m2/day) IL-2, with subsequent escalation of GM-CSF to 2.5 microgram/kg/day after careful observation for toxicities.

Lysis of human tumor cell lines by canine complement plus monoclonal antiganglioside antibodies or natural canine xenoantibodies

Because certain antiganglioside monoclonal antibodies can facilitate antibody-dependent cellular cytotoxicity against GD2+ ganglioside-bearing human and canine tumor cells, we wished to determine if clinically relevant antiganglioside monoclonal antibodies (Mabs) could also fix canine complement to lyse tumor cells in vitro. Using flow cytometry, human tumor cell lines (M21 melanoma and OHS osteosarcoma) were shown to highly express ganglioside GD2 and, to a lesser degree, GD3. In 51Cr release assays, M21 cells were lysed with canine serum, as a source of complement, plus either Mab 14.G2a or its mouse-human chimera, ch 14.18, specific for GD2. Heating canine serum abrogated its lytic activity and addition of rabbit complement reconstituted M21 lysis. Similar results were obtained with M21 cells when Mab R24 (against GD3) and canine serum were used. OHS cells were also lysed with canine serum plus Mab 14.G2a and lytic activity was abolished by heating canine serum but reconstituted with rabbit complement. Alone, canine serum or Mabs were not lytic to M21 or OHS cells. Conversely, human neuroblastoma (LAN-5) and K562 erythroleukemia cells were lysed by canine serum alone which was shown by flow cytometry to contain naturally occurring canine IgM antibodies that bound LAN-5 and K562 cells. The lytic activity of canine serum for LAN-5 or K562 cells was abolished by heating and restored by addition of either human or rabbit complement. Thus, human tumor cell lines can be lysed with antiganglioside Mabs through fixation and activation of canine complement-dependent lytic pathways. Canine xenoantibodies also mediate complement-dependent cytotoxicity of some human tumor cell lines. Together, these results are significant because they demonstrate an antitumor effect of the canine immune system which is of potential importance for cancer immunotherapy in a promising animal model.

Functional interleukin-2 receptors are expressed on natural killer-like leukemic cells from a dog with cutaneous lymphoma

We identified a dog with large granular lymphocytic leukemia and cutaneous lymphoma that exhibited constitutive expression of interleukin-2 (IL-2) receptors by the leukemic peripheral blood lymphocytes. The leukemic cells phenotypically resembled natural killer (NK) cells, and their surface IL-2 receptors were functional, as determined by the capacity to bind human recombinant IL-2 with high-affinity resulting in the transduction of proliferation signals and in the development of lymphokine-activated killer cell activity. These cells produced IL-2 spontaneously, and they may have maintained their proliferative state through an IL-2-dependent autocrine growth pathway. Our results indicate that neoplastic lymphocytes of syndromes that involve circulating leukemic cells with dermotropism can originate from NK-like cells. Additionally, the data also suggest that proliferative conditions such as these may be the result of the aberrant production of IL-2. Further, this case illustrates the potential for the use of hematopoietic malignancies in the dog as a suitable animal model for immune targeting of IL-2 receptors as a novel treatment approach for similar malignancies of human beings.

A phase II trial of human recombinant interleukin-2 administered as a 4-day continuous infusion for children with refractory neuroblastoma, non-Hodgkin's lymphoma, sarcoma, renal cell carcinoma, and malignant melanoma. A Childrens Cancer Group study

BACKGROUND

Recombinant human Interleukin-2 (IL-2) has been effective at inducing measurable antitumor responses in adults with renal cell carcinoma and melanoma. It also is being tested as adjuvant therapy for patients with acute myeloid leukemia after autologous bone marrow transplantation.

METHODS

The authors tested IL-2 in a pediatric Phase II trial using a regimen that has antitumor effects in adults and was proven to be tolerated acceptably in a prior Phase I pediatric trial. Thirty-eight patients were entered into this study of whom 36 received IL-2 and were evaluable (20 with sarcoma, 9 with neuroblastoma, 5 with renal cell carcinoma, and 1 each with melanoma and lymphoma).

RESULTS

Interleukin-2 dose modifications were based on tolerance and toxicity, such that 46% of these patients received a 50% increase in IL-2 dose during the second week, and 81% of those receiving the elevated dose continued receiving this dose level during the third week of treatment. A single patient with renal cell carcinoma had a complete response that was maintained; the remaining 35 patients did not show objective evidence of tumor response sufficient to qualify as either a complete response or a partial response.

CONCLUSIONS

Absolute lymphocyte counts were indicative of the immunostimulatory effect of this IL-2 regimen as observed for adults, with a median 7.2-fold increase. Nevertheless, despite immune activation, a sufficient number of patients were evaluated, indicating that IL-2 does not have measurable antitumor effects in children with large refractory sarcomas or neuroblastomas, whereas one of five children with renal cell carcinoma had a complete response, consistent with the 10-20% response rate observed in adults.

Clinical and immunological effects of treatment with murine anti-CD3 monoclonal antibody along with interleukin 2 in patients with cancer

Anti-CD3 mAb and interleukin 2 (IL-2) were used in a Phase I study to treat 29 patients with cancer. The anti-CD3 was given as an i.v. bolus infusion over 10 min followed by two i.v. 96-h continuous infusions of IL-2 at 3 x 10(6) units/m2/day with a 3-day rest between the IL-2 infusions. Four patients were treated with 6, 18, 60, and 300 microgram/m2 anti-CD3. One patient received 3000 microgram/m2 anti-CD3. This patient developed profound hypotension and the IL-2 infusions were delayed for 2 weeks. Two patients were treated at an intermediate dose of 600 microgram/m2. These patients developed dose-limiting toxicities including hypotension, dyspnea and increased blood urea nitrogen, creatinine, and bilirubin. They were unable to complete their first course of therapy. In an effort to achieve a dose of anti-CD3 which would activate T cells in vivo, pentoxifylline was given to blunt the toxicities seen with anti-CD3 thought to be due predominantly to the cytokine syndrome and tumor necrosis factor release. Four patients received p.o. pentoxifylline to cover an anti-CD3 dose of 600 microgram/m2. The IL-2 infusion was initiated 1 week after the mAb. While there was an anti-CD3 dose-dependent increase in serum tumor necrosis factor level 1 h after mAb infusion, pentoxifylline did not reduce the serum tumor necrosis factor level. There was also an anti-CD3 dose-dependent increase in the serum soluble IL-2 receptor levels. Other immune parameters monitored, including in vitro cytotoxic and proliferative responses and lymphocyte count, were similar to treatment courses with IL-2 alone. Fourteen of 26 patients examined developed human anti-murine antibodies following a single dose of anti-CD3. There were no objective antitumor responses. We conclude that in vivo treatment with anti-CD3 did not enhance T cell activity or expansion with subsequent IL-2 infusion and that the combination of anti-CD3 followed by IL-2 did not improve upon the antitumor activity previously seen with IL-2 alone.

Potential to involve multiple effector cells with human recombinant interleukin-2 and antiganglioside monoclonal antibodies in a canine malignant melanoma immunotherapy model

Human tumors originating from neuroectodermal cells such as malignant melanoma and neuroblastoma express high levels of disialogangliosides GD2 and GD3, making these antigens ideal for targeting by monoclonal antibodies (Mabs). The purpose of this study was to investigate expression and targeting of gangliosides on canine melanoma. Using immunohistochemical methods, we analyzed the expression of disialogangliosides GD2 and GD3 on canine oral malignant melanomas with murine Mabs 14.G2a and R24 that recognize GD2 and GD3 disialogangliosides, respectively, on human tumors. We also assessed the ability of Mab 14.G2a (and its mouse-human chimera, ch 14.18) to mediate antibody-dependent cellular cytotoxicity (ADCC) in vitro against a canine malignant melanoma cell line with human recombinant interleukin-2 (IL-2) activated canine peripheral blood lymphocytes (PBL), or canine neutrophil effector cells. Our data show that Mabs 14.G2a and R24 recognized fresh frozen canine oral melanoma. Mabs 14.G2a or ch 14.18, or IL-2, potentiated lysis of the canine malignant melanoma cell line by canine PBL. The killing effect observed using the combination of either Mab with IL-2 was additive. Mab 14.G2a mediated potent ADCC of canine melanoma by canine neutrophils. These studies indicate that disialogangliosides are expressed on fresh canine melanoma cells. Mabs reactive with these antigens can target and trigger tumor killing by multiple canine effector populations and IL-2 can potentiate these effects by canine lymphocytes. Thus, canine oral malignant melanoma, a spontaneously occurring, metastatic cancer in the dog, may be a relevant animal model to investigate combination immunotherapy using antitumor Mab and IL-2.

Clinical and immunological effects of human recombinant interleukin-2 given by repetitive weekly infusion to normal dogs

Four normal adult dogs received two consecutive weekly cycles of human recombinant interleukin-2 (IL-2) by continuous infusion for 4 days/week. The dose of IL-2 given to each dog was 3 x 10(6) units m-2 day-1. Toxicities consisted of mild vomiting, diarrhea, and lethargy to varying degrees in all the dogs. These side-effects were reversed when the treatment was discontinued. Fever, tachypnea, and weight gain were not seen. A marked lymphocytosis and eosinophilia developed in all dogs after completion of each course of IL-2 (resulting in a more than sevenfold increase in each cell type) and persisted for more than 1 month in some. Fresh peripheral blood lymphocytes (PBL) obtained during this lymphocytosis mediated enhanced in vitro lysis of a natural-killer-cell-sensitive canine tumor cell line (CTAC). The in vitro proliferative responses of these same PBL to IL-2 could be detected earlier, progressed faster, and involved more cells than PBL tested prior to IL-2 infusion. Thus, a relatively well-tolerated regime of IL-2 in dogs can induce dramatic increases in lymphocyte numbers and activation, which is associated with augmentation of their in vitro antitumor reactivity. The clinical effectiveness of this immunotherapeutic approach remains to be tested in tumor-bearing dogs where it could serve as a relevant large-animal model for immunotherapy of cancer with IL-2.

Allogeneic T-cell clones able to selectively destroy Philadelphia chromosome-bearing (Ph1+) human leukemia lines can also recognize Ph1- cells from the same patient

Immunocompetent cells in bone marrow allografts have been associated with a graft-versus-leukemia (GVL) effect. To further characterize effector mechanisms that may be involved in this GVL phenomenon, we have previously established an in vitro model to identify allogeneic T-cell clones that selectively mediate cytotoxicity against a patient's leukemic cells, but not against nonleukemic lymphocytes from the same patient. We have modified this in vitro model to test whether the Ph1 chromosome and the P210 fusion protein it controls have a detectable role in leukemia-specific recognition by allogeneic T-cell clones. In this report, T-cell lines reactive with allogeneic Ph1 chromosome-bearing (Ph1+) chronic myeloid leukemia (CML) cell lines were derived and selected to be minimally reactive with Ph1 negative (Ph1-) lymphoid lines from the same patient. However, after prolonged culture, these same T-cell lines also mediated significant destruction of the Ph1- target cells from the same patients. These T-cell lines specifically recognized cells from the allogeneic CML patient to which they were sensitized, and were not contaminated by an outgrowth of natural killer cells. Furthermore, subclones could be derived from these T-cell lines, and some of these subclones again showed selective killing of the allogeneic Ph1+ leukemia cell lines, and not of the Ph1- cell line from the same patient. Analyses of T-cell receptor (TCR) genes showed the alloreactive T-cell lines and the Ph1+ selective subclones derived from them to be of the same clonal origin. This suggests that the same T cells reacting with antigens expressed on the nonleukemic Ph1- targets can at times selectively and preferentially kill the allogeneic Ph1+ cells. As the same TCR that recognizes Ph1+ cells also can recognize the Ph1- targets, it appears that the Ph1+ chromosome does not play a detectable role in recognition by these allogeneic T-cell clones. This in vitro observation may provide a model for evaluating the relationship between GVL and graft-versus-host disease effects.

Treatment of neuroblastoma patients with antiganglioside GD2 antibody plus interleukin-2 induces antibody-dependent cellular cytotoxicity against neuroblastoma detected in vitro

Therapy of neuroblastoma patients with interleukin (IL)-2 activates effector cells capable of lysing tumor cells in vitro. When tumor cells are pretreated with certain monoclonal antibodies (MoAb), these in vivo activated effectors show augmented tumor lysis via antibody-dependent cellular cytotoxicity (ADCC). This study presents immunological analyses of serial blood samples from two refractory neuroblastoma patients who received combined in vivo therapy with murine anti-ganglioside GD2 monoclonal antibody 14.G2a and IL-2. These studies were designed to determine whether conditions that induce ADCC in vitro can be generated in vivo by combined therapy with IL-2 and MoAb. As shown previously, administration of IL-2 dramatically augments the ability of peripheral blood mononuclear cells (PBMC) to mediate ADCC. In addition, we demonstrate here that sera, obtained 1 h after infusion of 14.G2a, provides an effective source of functional antibody for ADCC mediated by PBMC from healthy donors. Finally, effective ADCC-mediated killing of neuroblastoma target cells was also achieved in vitro following IL-2 plus 14.G2a treatment when patients' effector cells were combined with patients' serum, as the source of 14.G2a antibody. These results indicate that this combination of IL-2 and 14.G2a generates conditions within the peripheral blood of pediatric neuroblastoma patients that enable their own lymphocytes to mediate antibody-dependent cellular cytotoxicity sufficient to effectively kill neuroblastoma cells in vitro.

Induction of lymphokine-activated killer (LAK) activity in canine lymphocytes with low dose human recombinant interleukin-2 in vitro

Interleukin-2 (IL-2) is an immunostimulatory cytokine that induces activation of peripheral blood lymphocytes (PBL) which can mediate augmented tumor cytotoxicity. Several regimens using IL-2 as treatment for metastatic melanoma and renal carcinoma have shown measurable tumor responses in 10-20% of human patients. Our overall goals are to determine the efficacy of IL-2 as an adjuvant treatment for canine tumors. In order to evaluate the possibility to extend the use of IL-2 in vivo in the dog, we examined the ability of a clinically relevant (low) dose of human recombinant IL-2 (100 units/ml) to enhance the tumoricidal properties of canine PBL in vitro. This was particularly important considering the need to establish the effects on canine PBL by IL-2 at a dose that is potentially achievable in vivo with acceptable side effects. Our data show, for the first time, the ability to separate canine natural killer (NK) cell activity from lymphokine-activated killer (LAK) cell activity (induced with a low IL-2 dose) mediated by canine PBL against two canine cell lines (CTAC and CML-10) used as targets in 4 vs. 16 hour killing assays. LAK cells generated by stimulation of canine PBL with 100 units/ml of IL-2 for 72 hours, could kill CTAC or CML-10 targets up to 11 or 18 times more efficiently, respectively, than fresh PBL in a 4 hour assay. However, the killing of efficiency of the LAK cells was only 2- to 3-fold greater than that of the fresh PBL in a 16 hour assay. This apparent reduction in the killing efficiency of the LAK cells was mostly due to increased spontaneous NK activity by the fresh PBL after 16 hours in culture; both the LAK cells and the fresh PBL (NK cells) mediated a greater overall cytotoxicity after 16 hours than they did in the 4 hour assays. These results indicate that a low dose of human recombinant IL-2 can augment tumor killing by canine PBL in vitro, and suggest that it may be feasible to examine the potential use of IL-2 as an immunotherapeutic agent in tumor-bearing dogs.

Activation of multiple effector mechanisms to enhance tumor immunotherapy

Recent technical advances have enabled the generation of clinical reagents for immunotherapy. Currently, treatment protocols combining both interleukin-2 (IL-2) and tumor-specific monoclonal antibody are underway at the University of Wisconsin Comprehensive Cancer Center and elsewhere. These approaches are based on the hypothesis that IL-2-activated lymphocytes will use tumor-reactive antibody to more selectively and effectively destroy tumor in vivo. Just as IL-2 can activate lymphocytes to destroy antibody-coated tumor cells, other agents can activate neutrophils and monocytes to destroy antibody-treated tumor cells. We are investigating, in laboratory and clinic, approaches aimed at eventually using combinations of distinct antibody-based tumor recognition mechanisms in patients whose monocytes, neutrophils, and lymphocytes have been simultaneously activated with multiple biologic agents.

Modulation of target-cell culture conditions alters susceptibility to lymphocyte-mediated lysis

The culture conditions of the immortalized human breast cell line, 184B5, can be manipulated to evaluate conditions that influence target lysis by activated immune effector cells. Exponentially growing 184B5 cells (EXP) are more susceptible than growth-factor-deprived (removal of epidermal growth factor and bovine pituitary extract) 184B5 cells (GFD) to lysis by lymphokine-activated killer (LAK) cells, activated natural killer (NK) clones, and activated gamma/delta receptor expressing T-cell clones. LAK-cell lysis of contact-inhibited 184B5 cells is similar to lysis of GFD, while 184B5 cells with severe nutrient deprivation are more easily lysed than GFD by LAK cells. In a cold target inhibition assay with LAK effector populations, EXP are better inhibitors than GFD against several targets. Further analysis of the mechanism by which changes of in vitro culture conditions alter target-cell susceptibility to immune-mediated lysis may assist therapeutic strategies that involve combinations of standard therapies with biologic approaches.

A pilot phase II trial of continuous-infusion interleukin-2 followed by lymphokine-activated killer cell therapy and bolus-infusion interleukin-2 in renal cancer

Nine patients with metastatic renal cell carcinoma were entered into a pilot protocol including a 4-week regimen utilizing human recombinant interleukin-2 (IL-2) and in vitro lymphokine-activated killer (LAK) cells. The regimen included 2 weeks (4 days of treatment and 3 days of rest/week) of continuous-infusion (c.i.) IL-2 at 3 x 10(6) U/m2/day, followed by two leukaphereses. LAK cells were cultured in vitro for 48 to 72 h and administered as a single infusion, followed by 9 days of bolus i.v. injections of 10(6) U IL-2/m2/dose, given every 8 hours (t.i.d.). The average (+/- SD) number of LAK cells infused per patient was 7.2 x 10(10) (+/- 3.5 x 10(10)). One patient showed > 50% shrinkage of tumor (lung + renal bed recurrence). Toxicity was similar to that encountered in other studies using similar IL-2 doses and LAK cells and consisted of fever, hypotension, fluid retention, and reversible renal insufficiency. These results indicate that the 2 weeks of IL-2 c.i. provided conditions enabling the harvest of large quantities of mononuclear cells from the peripheral blood of patients; this could be useful for future trials requiring the use of in vitro activated lymphocytes. Nevertheless, these pilot data suggest that this regimen of prolonged t.i.d. IL-2 administration after the LAK infusion does not seem to generate any improvement in antitumor effects from those obtained using other LAK + IL-2 regimens.

Serum CD25 levels during interleukin-2 therapy: dose dependence and correlations with clinical toxicity and lymphocyte surface sCD25 expression

Using an enzyme-linked immunosorbent assay (ELISA), we have measured serum levels of a soluble form of the p55 subunit of the interleukin-2 receptor complex, soluble CD25 (sCD25), at regular intervals in the sera of 51 pediatric and adult cancer patients receiving recombinant human interleukin-2 (IL-2). The IL-2 was administered in repetitive weekly cycles alone or in combination with lymphokine-activated killer (LAK) cells. Levels of CD25 correlated with clinical toxicities reflected by nadir blood pressures, percentages of weight gained, and minimum Karnofsky performances during IL-2 therapy. Coadministration of autologous in vitro activated LAK cells together with IL-2 did not significantly affect the pattern of sCD25 release relative to administration of IL-2 alone. Examination of sCD25 release in response to different doses of IL-2 revealed a statistically significant dose effect of IL-2 on the sCD25 levels in patient sera. In addition, the level of sCD25 in patient sera also correlated strongly with expression of CD25 on the surface of peripheral blood lymphocytes (PBL) obtained from patients following IL-2 therapy. These studies demonstrate the utility of the sCD25 ELISA as a clinical tool for monitoring patients on treatment regimens that include IL-2.

Immunological effects of levamisole in vitro

Levamisole, an anthelminthic drug with immunological properties, has recently been reported to have antitumor activity when administered with 5-fluorouracil in patients with Duke's C colorectal carcinoma. The mechanism of this antitumor effect is unknown, but has been postulated to be related to levamisole's immunomodulatory properties. To define further the immunomodulatory activities of levamisole, we studied the in vitro effects of levamisole on monocyte and lymphocyte cytotoxicity, activation, and proliferation; induction of cytokine-induced proteins; and expression of tumor-associated antigens. Experiments utilized peripheral blood mononuclear cells from normal donors incubated in the presence of increasing concentrations of levamisole (0.1 to 100 micrograms/ml). Levamisole had no consistent effect on induction of 2',5'-oligoadenylate synthetase activity or indoleamine-2,3-dioxygenase activity, or production of tumor necrosis factor. Levamisole had no effect on monocyte cytotoxicity or expression of HLA-DR, HLA-DQ, HLA-DP, and the Fc receptor. Similarly, levamisole had no significant effect on NK or LAK cytotoxicity or the immunological activation of T-lymphocytes, assessed by expression of CD3, CD4, CD8, CD16, CD25, and CD56. Proliferation of lymphocytes from normal donors, patients with benign polyps, and patients with malignancies, with or without IL-2 or irradiated LS174T cells, was not significantly increased overall. No significant enhancement in the expression of three tumor-associated antigens (880364, NRCO-4, and ING-1) and the intercellular adhesion molecule-1 (ICAM-1) antigen on four human cancer cell lines was observed following in vitro exposure to levamisole. We conclude that levamisole is not a potent modulator of the immune parameters we examined, and that the mechanism behind the unique clinical interaction between levamisole and 5-fluorouracil in colorectal carcinoma remains to be identified.

Activation of human T cells obtained pre- and post-interleukin-2 (IL-2) therapy by anti-CD3 monoclonal antibody plus IL-2: implications for combined in vivo treatment

The role of activated T cells in the mediation of antitumor responses has been documented in several experimental models. In some of these, interleukin-2 (IL-2) has been used as a means to induce and expand the antitumor effects of the T cells. IL-2 has been tested in clinical trials for cancer treatment. Surprisingly, T cells appear to be inactivated by IL-2 in these clinical trials. T cells obtained from peripheral blood after IL-2 therapy showed decreased responses to mitogens and alloantigens, did not proliferate in vitro in response to IL-2, and did not mediate non-major histocompatibility complex-restricted cytotoxicity or targeted lysis in the presence of bispecific monoclonal antibodies. In this study, we present evidence that these post-IL-2 therapy T cells are not irreversibly inactivated; they can be activated in vitro by anti-CD3 monoclonal antibody together with IL-2 to upregulate the p55 component of the IL-2 receptor and proliferate. Nevertheless, following activation by anti-CD3 and IL-2, the level of targeted T-cell cytotoxicity mediated by the post-IL-2 therapy T cells was significantly lower than that by pre-IL-2 therapy T cells. Although in vivo treatment with IL-2 alone induces natural killer (NK) cells to mediate lymphokine-activated killer activity, these data suggest that the T-cell lytic function is inhibited by this treatment and only partially reversible by subsequent T-cell receptor activation using anti-CD3 mAb. Exposure of T cells to anti-CD3 mAb prior to in vivo IL-2 treatment generates T-cell lytic activity in vitro. These results, together with preclinical murine studies, suggest that a combined in vivo protocol of anti-CD3 mAb and IL-2, starting first with the anti-CD3 mAb, may cause activation of the T cells in addition to the activation of NK cells and thus warrant clinical testing.

BLT-esterase activity following in vitro and in vivo activation of human lymphocytes with interleukin-2. In vivo IL-2 induces BLT-esterase

BLT-esterase and cytolytic activity by human in vitro and in vivo generated Lymphokine Activated Killer (LAK) cells were measured. Lysates made from peripheral blood lymphocytes (PBL) of both normal donors and cancer patients receiving IL-2 therapy were assayed for BLT-esterase activity in a spectro-photometric assay. Cytotoxicity of PBL was measured in a 51Cr-release assay. Both BLT-esterase activity and cytotoxicity increased when normal-donor PBL were stimulated in vitro with IL-2, with greater activities at higher IL-2 concentrations. The activities also increased over time, peaking at 6 days of in vitro stimulation. Patient PBL had increased BLT-esterase and cytotoxic activities after 4 weeks of in vivo IL-2 treatment. This association of BLT-esterase activity and cytotoxicity with IL-2 activation is consistent with the model that LAK cytotoxicity is mediated by secretion of BLT-esterase associated cytolytic granules. Lymphocytes obtained after in vivo IL-2 treatment and cultured for 3-4 hours in IL-2 show markedly augmented cytotoxic activity but no increase in their BLT-esterase activity. These results indicate that the increased cytotoxicity observed after this brief pulse of in vitro IL-2 following in vivo IL-2 treatment must result from effects of IL-2 other than the production of more esterase-containing cytolytic granules.

Analysis of T cell receptor beta and gamma genes from peripheral blood, regional lymph node and tumor-infiltrating lymphocyte clones from melanoma patients

A total of 199 T cell clones from two melanoma patients were derived from progenitor T cells from recurrent melanoma, regional lymph nodes (either involved or uninvolved with malignancy) and peripheral blood by inoculating single cells directly into the wells of microtiter plates before in vitro expansion. The surface marker phenotype of most clones was CD4+CD8-, although some were CD4-CD8+. Genomic DNA prepared from all clones was analyzed by Southern blot hybridization using T cell receptor (TCR) beta and gamma gene probes, seeking clones with identical TCR gene rearrangement patterns as direct evidence for in vivo progenitor T cell clonal amplification. Probing HindIII-digested DNA with TCR beta and TCR gamma probes revealed several clones with identical TCR gene rearrangement patterns. These clones had subsequent probing of BamHI-digested DNA with TCR beta and TCR gamma probes, which showed all but 2 clones to have distinct rearrangement patterns. These analyses provide clear molecular evidence for in vivo polyclonal CD4+ T cell populations in each of several separate immune compartments in these patients.

Prolonged interleukin-2 (IL-2) treatment can augment immune activation without enhancing antitumor activity in renal cell carcinoma

Preliminary studies involving small numbers of patients have suggested that interleukin-2 (IL-2) administered by continuous infusion in repetitive weekly cycles using doses of 3 x 10(6) U/M2/day is immunologically active and can induce tumor responses in patients with renal cell carcinoma. This study was designed to examine both the immunological and clinical effects of prolonged infusion IL-2 given by repetitive weekly cycles; first at moderate doses for 4 weeks as an impatient followed by lower doses of IL-2 for up to 5 months. Prolonged IL-2 treatment was investigated because previous studies revealed that patients had a return to their baseline immune status within 4 weeks after completing IL-2 treatment. Twenty-five patients (including 18 with renal cell carcinoma) were treated with one of two regimens utilizing IL-2 as sole therapy. These regimens were designed to induce augmented and prolonged immune activation based upon in vitro and in vivo data. Though patients on both arms of the study demonstrated sustained lymphocytosis, increase in numbers of natural killer cells, and induction of lymphokine-activated killer activity with prolonged IL-2 administration, only 1 out of the 18 patients with renal cell carcinoma demonstrated a sustained partial antitumor response to therapy. Furthermore, several patients demonstrated profound immune activation, without any evidence of tumor regression. The lack of clinical responses in these patients showing marked activation of LAK cytotoxicity suggests that other variables must also influence the likelihood of antitumor effects for patients receiving IL-2 therapy.

The influence of autologous lymphokine-activated killer cell infusions on the toxicity and antitumor effect of repetitive cycles of interleukin-2

Twenty patients with refractory malignancies were treated with a protocol evaluating the addition of ex vivo-activated autologous lymphokine-activated killer (LAK) cells to a clinically tolerable interleukin-2 (IL-2) regimen (four weekly cycles of human recombinant IL-2 at 3 x 10(6) U/m2/day by continuous infusion for 4 days/week). Sixteen patients completed their induction month of therapy, two had a partial response, six had stable disease, and eight had progressive disease. Four patients had clinical toxicity preventing completion of the induction month of therapy, and one of these patients died during therapy. Significant clinical toxicities included decreased performance status, weight gain, catheter-related thromboses, infectious complications, fever, hypotension, and dyspnea or hypoxemia requiring oxygen. Thus, the addition of LAK cell infusions to this IL-2 regimen did not cause a noticeable change in antitumor response rate but did not cause more severe toxicity.

Limiting dilution analysis of lymphokine-activated killer cell precursor frequencies in peripheral blood lymphocytes of cancer patients receiving interleukin-2 therapy

Eleven patients receiving weekly cycles of therapy with recombinant interleukin-2 (IL-2) were evaluated with a sensitive limiting dilution analysis to determine lymphokine-activated killer (LAK) cell precursor frequencies in peripheral blood lymphocytes. An increase in LAK precursor frequency above baseline was suggested by day 6 of this protocol and was clearly significant by day 20, indicating an expansion of the circulating precursor pool results from in vivo IL-2 administration. Correlations were not significant between LAK precursor frequency during IL-2 therapy and the total number of circulating lymphocytes, the percentage of CD56+ lymphocytes, IL-2 proliferative responses, or LAK activity of peripheral blood lymphocytes, indicating that the precursor frequency identification based on functional testing of individual cells is not accurately reflected by these analyses of heterogeneous bulk populations. Selective cell depletion analyses revealed that the majority of LAK precursors after in vivo IL-2 therapy were cells with the natural killer phenotype. Analysis of LAK precursors may help define the in vivo IL-2 administration, alone or in combination with other hematopoietic or immunodifferentiative cytokines, necessary to further augment in vivo effector cell numbers and activity for patients with cancer.

Increased expression of the interleukin 2 (IL-2) receptor beta chain (p70) on CD56+ natural killer cells after in vivo IL-2 therapy: p70 expression does not alone predict the level of intermediate affinity IL-2 binding

The expression of the 70-kD beta subunit of the interleukin 2 receptor (IL-2R) has been examined on peripheral blood lymphocytes (PBL) obtained from patients receiving systemic infusions of IL-2. Using monoclonal antibodies directed against p70, flow cytometric analyses revealed a greater than threefold increase in expression of the IL-2R beta chain on CD56+ natural killer (NK) cells from post-IL-2 therapy PBL relative to pre-therapy cells. The level of p70 expression on the post-therapy cells was three- to fourfold greater (based on fluorescence intensity) than the level of p70 expression on YT cells, an NK-like cell line that expresses approximately 12,000 intermediate affinity IL-2 binding sites/cell. Despite the high level of p70 expression, in 125I-IL-2 binding assays only 790-1,290 intermediate affinity IL-2 binding sites/cell were detected on post-therapy cells from six patients. These data represent the first report of increased p70 expression after in vivo IL-2 administration and suggest a requirement for at least one additional subunit for the formation of functional intermediate affinity IL-2Rs. Furthermore, the presence on the surface of post-therapy NK cells of excess p70 that does not bind IL-2 with intermediate affinity implies that the formation of intermediate affinity IL-2Rs is not solely determined by the level of p70 expression, and that the response of NK cells to IL-2 might be regulated by altering the expression of p70 or some other IL-2R subunit.

Augmentation of antibody dependent cell mediated cytotoxicity following in vivo therapy with recombinant interleukin 2

Monoclonal antibodies (mAB) with tumor specificity are able to enhance the immunological specificity of interleukin 2 (IL-2)-activated lymphokine activated killer (LAK) cells. Antibodies may also be used to broaden the range of tumor types susceptible to immune mediated cytotoxicity by the activated LAK cells. In these studies, mAB with relative tumor specificity were used to target immunologically activated effector cells in an in vitro antibody dependent cell mediated cytotoxicity (ADCC) assay. The mAB included: 3F8 and 14.G2a, which are both specific for neuroblastoma and melanoma and recognize ganglioside GD2, and mAB ING-1, a mouse-human chimeric antibody with constant regions from human IgG1 and kappa chains and variable regions from a mouse mAB that binds to a broad range of human adenocarcinomas. Each of these mAB was able to mediate ADCC with fresh effector cells and antibody binding targets. When peripheral blood mononuclear cells were obtained from cancer patients prior to and following in vivo therapy with interleukin 2, a significant increase was noted in ADCC activity by peripheral blood mononuclear cells obtained following IL-2 therapy. Inclusion of IL-2 in the medium during the cytotoxic assay with mAB further boosted ADCC. The total activity seen was often greater than the sum of the independent LAK activity and standard ADCC activity. The cells responsible for this ADCC had the CD16+ Fc receptor. Combining IL-2 with mAB in clinical tumor therapy may lead to a wider range of tumor types being responsive to immunotherapy and may also enhance the efficacy of therapy by specifically targeting activated effector cells to tumor cells recognized by mAB. Our results provide strong support for the testing of these hypotheses in clinical trials by combining in vivo treatment with IL-2 and mAB able to mediate ADCC.

Effects of interleukin-2 (IL-2) on human plasma lipid, lipoprotein, and C-reactive protein

Six patients with confirmed malignant disease received four consecutive weekly cycles of human recombinant interleukin-2 (IL-2) 4 days/week, continuous iv. infusion, 3 X 10(6) U/m2/day. Plasma cholesterol decreased a mean of 7% within 24 hours after IL-2 infusion and decreased by 33% within 4 days. Plasma cholesterol was significantly lower than baseline concentration by day 21 (-21%), and day 25 (-41%) was significantly lower than day 21. Decreased plasma cholesterol was the result of decreased HDL and LDL cholesterol concentrations. Plasma triglyceride demonstrated a mean increase of 46% after 4 days of therapy and remained greater than baseline concentrations at all time points analyzed. Apolipoprotein AI and AII decreased concomitantly with HDL-cholesterol concentrations, whereas apolipoprotein B after an initial mean decrease of 17% during the first cycle was not significantly different from baseline during the fourth cycle. Apolipoprotein E and Lp(a) were not significantly affected by IL-2 treatment. Plasma C-reactive protein (CRP) increased by 79% within 24 hours of therapy, increased by 254% on day 4, then decreased to baseline concentrations by day 21 after 3 days off of IL-2. Day 25 CRP was elevated compared to both baseline and day 21 concentrations. IL-2 induced plasma lipoprotein changes may be due in part to the induction of interferon gamma.

Human T cell receptor-gamma delta-expressing T-cell lines recognize MHC-controlled elements on autologous EBV-LCL that are not HLA-A, -B, -C, -DR, -DQ, or -DP

HLA-loss variants of an EBV-transformed B lymphoblastoid cell line (EBV-LCL) 721 were used to investigate whether human MHC molecules other than known class I or class II were involved in autologous T cell responses. Bulk lymphocyte cultures of purified T cells primed to an autologous variant EBV-LCL that fails to express HLA-class II and has reduced cell surface HLA-class I expression, and oligoclonal TCR-gamma delta-bearing lines derived from them, could lyse both this EBV-LCL and an independently derived, class II expressing autologous variant EBV-LCL that bears no HLA-A, -B, or -C, suggesting the presence of additional HLA-like restriction elements. Cold target inhibition of cytolysis mediated by these lines indicated that a shared or cross-reactive MHC controlled restriction element other than the known MHC determinants was retained by the EBV-LCL variants. Single-cell derived clones from these T cell lines which expressed only the TCR-gamma delta showed this same target cell specificity pattern, proving recognition of MHC-controlled determinants by autologous gamma delta T cells. Anti-gamma delta antibody could inhibit cytolysis by the gamma delta-expressing lines, suggesting that the TCR-gamma delta was involved in recognition of the EBV-LCL targets. Flow cytometric analysis with separate HLA-reactive antibodies indicated that the restriction element for these cytolytic responses is a molecule serologically cross-reactive with HLA-B and -C Ag, yet is a determinant that cannot be HLA-A, -B, -C, -DR, -DQ or -DP.

Human T cell receptor-gamma delta-expressing T-cell lines recognize MHC-controlled elements on autologous EBV-LCL that are not HLA-A, -B, -C, -DR, -DQ, or -DP

HLA-loss variants of an EBV-transformed B lymphoblastoid cell line (EBV-LCL) 721 were used to investigate whether human MHC molecules other than known class I or class II were involved in autologous T cell responses. Bulk lymphocyte cultures of purified T cells primed to an autologous variant EBV-LCL that fails to express HLA-class II and has reduced cell surface HLA-class I expression, and oligoclonal TCR-gamma delta-bearing lines derived from them, could lyse both this EBV-LCL and an independently derived, class II expressing autologous variant EBV-LCL that bears no HLA-A, -B, or -C, suggesting the presence of additional HLA-like restriction elements. Cold target inhibition of cytolysis mediated by these lines indicated that a shared or cross-reactive MHC controlled restriction element other than the known MHC determinants was retained by the EBV-LCL variants. Single-cell derived clones from these T cell lines which expressed only the TCR-gamma delta showed this same target cell specificity pattern, proving recognition of MHC-controlled determinants by autologous gamma delta T cells. Anti-gamma delta antibody could inhibit cytolysis by the gamma delta-expressing lines, suggesting that the TCR-gamma delta was involved in recognition of the EBV-LCL targets. Flow cytometric analysis with separate HLA-reactive antibodies indicated that the restriction element for these cytolytic responses is a molecule serologically cross-reactive with HLA-B and -C Ag, yet is a determinant that cannot be HLA-A, -B, -C, -DR, -DQ or -DP.

Specific recognition of human leukemic cells by allogeneic T cells: II. Evidence for HLA-D restricted determinants on leukemic cells that are crossreactive with determinants present on unrelated nonleukemic cells

Transplantation of immunocompetent cells present within allogeneic bone marrow has been associated with the elimination of residual host leukemia, both in animal tumor models and in patients receiving marrow transplants for leukemia. This observation has been called the "graft-versus-leukemia effect." We have attempted to study this phenomenon in vitro by characterizing the cytolytic response of T cells from normal donors after in vitro activation with allogeneic leukemic cells. As expected, most T cells that react against an allogeneic patient's leukemic cells recognize their foreign HLA antigens and lyse the patient's nonleukemic remission lymphoid cells. In addition, we have shown that a small fraction of the T cells recognize and lyse foreign leukemic targets without lysis of nonmalignant remission targets from the same leukemic patient. These T cells have been isolated and characterized as CD3+, CD4+ cells expressing the alpha/beta T cell receptor (TCR). Their lysis appears to reflect specific antigen recognition mediated via the CD3-TCR complex and interactions involving the CD4 receptor. Some of these "leukemic specific" T cell lines, which are restricted by HLA class II molecules, can also lyse occasional nonleukemic cells from certain unrelated donors. This recognition appears to involve crossreactive determinants shared by the leukemic cells and the unrelated allogeneic nonleukemic cells. These specific interactions may represent an in vitro model of the graft-versus-leukemia effect.

Natural killer cells activated by interleukin 2 treatment in vivo respond to interleukin 2 primarily through the p75 receptor and maintain the p55 (TAC) negative phenotype

Interleukin 2 (IL-2) induced activation of unstimulated resting natural killer (NK) cells or resting T-cells initially occurs following binding of IL-2 through the p75 receptor that is expressed primarily by these cells. However, this IL-2/p75 interaction induces TAC chain synthesis and formation of high affinity IL-2 receptor required for the proliferation of resting peripheral blood lymphocytes. In this study, we present data indicating that NK cells activated by in vivo IL-2 treatment, in contrast to resting NK cells, respond and proliferate to further IL-2 in vitro using primarily the p75 receptor with only a minor component of cells responding through the high affinity receptor. These in vivo activated NK cells minimally expressed the TAC chain and maintained this TAC negative phenotype while proliferating in response to IL-2. The primary involvement of the p75 receptor in the proliferative response of these cells to IL-2 was demonstrated by the need for concentrations of IL-2 higher than 44 pM to obtain a significant response and by the dramatic inhibition of this response by anti-p75 monoclonal antibody. Anti-TAC monoclonal antibody inhibited only the poor proliferation obtained at low doses of IL-2 suggesting a minor role for TAC and high affinity IL-2 receptors. This was in contrast to the partial inhibition of proliferation by anti-p75 or anti-TAC observed in unstimulated pretherapy peripheral blood lymphocytes suggesting that these cells respond to IL-2 through both high affinity receptors and intermediate affinity p75 receptors. The T-cells isolated from in vivo activated peripheral blood lymphocytes, despite expressing TAC, were not responsive to IL-2, suggesting that these cells express predominantly nonfunctional low affinity TAC receptors. NK cells activated by IL-2 in vivo represent a unique model system of IL-2 dependent cells that respond and proliferate to IL-2 essentially through the p75 IL-2 receptor.