Passive immunotherapy of leukemia and other cancer

Monoclonal antibodies in cancer detection and therapy

Anticancer antibodies have had a long history in the management of cancer, with major applications having been shown in the immunohistochemistry and immunoassay of tumor-associated antigen markers. With the advent of hybridoma-derived monoclonal antibodies, attempts to use these more reproducible reagents in vivo for cancer detection and therapy have intensified. Radiolabeled monoclonal antibodies appear to be gaining a role in the management of cancer by means of imaging methods to detect sites of increased radioactivity, and several products have been developed and tested clinically. In the area of radioimmunotherapy, a number of problems still need to be solved, including low tumor uptake of the radioimmunoconjugate, dose-limiting myelotoxicity, and the induction of an immune response to repeated doses of murine (foreign) immunoglobulins. Similar problems exist for toxin and drug immunoconjugates, but these also fail to benefit from the "bystander" effect of the ionizing radiation delivered with radioimmunoconjugates, and plant and bacterial toxin molecules appear to have additional immunogenicity that restricts repeated injections. Despite these limitations, recombinant engineering and other chemical approaches are making progress in developing second-generation immunoconjugates that may be more efficacious and less immunogenic as cancer-selective therapeutics. Although nonconjugated, "naked", murine monoclonal antibodies have shown limited success in the therapy of human neoplasms, human and "humanized" forms may be more effective, particularly in lymphatic tumors. Some evidence also suggests that anti-idiotype antibodies (antiantibodies) may serve as surrogate antigens in cancer vaccines. Thus, a number of promising immunologic approaches for cancer diagnosis, detection, and therapy have made important progress in recent years.

The effect of an anti-membrane antibody-methotrexate conjugate on the human prostatic tumour line PC3

Methotrexate (MTX) was linked, via an active ester intermediate, to a purified IgG fraction of rabbit polyclonal antiserum raised against a cell membrane preparation from the human prostatic cell line PC3. The resulting conjugates contained an average of 0.044 mg of MTX per mg of antibody with acceptable losses in both the binding activity of the immunoglobulin (27.5%) and the enzyme inhibitory activity of the drug (32% at a MTX concentration of 3 x 10(-7) M). Using cultures of PC3 cells the antibody-MTX (Ab-MTX) conjugates were observed to be as effective as free drug in causing cell death and more effective than non-immune IgG-MTX (NIgG-MTX) conjugates. When athymic nude mice bearing PC3 tumours were administered with Ab-MTX conjugates, significant reductions in tumour growth rates were observed compared to animals given saline, MTX alone or NIgG-MTX conjugates (P less than 0.01 in all cases). Furthermore, the accumulation of radioactive MTX in the tumour tissue of animals injected with these Ab-MTX conjugates was 16-fold greater than those given free drug and 8.6-fold greater than those administered with NIgG-MTX conjugates. Uptake by the reticuloendothelial system, however, was not significantly different when animals from each treatment group were compared.

Evaluation of alternative methodologies for the generation of murine monoclonal anti-idiotypic antibodies to human B cell leukemias and lymphomas

The standard immunization procedure for the development of monoclonal antibodies to human malignant B cell idiotype immunoglobulin in our laboratory consists of intraperitoneal immunization with 50-100 micrograms of purified immunoglobulin followed 7 days later by intravenous immunization with an equal quantity of protein. In order to shorten the process and decrease the amount of idiotypic immunoglobulin necessary for successful immunization, we have evaluated 2 alternative immunization procedures. When immunized by the standard method, the percentage of hybridomas demonstrating anti-idiotype activity was 0.3-1.0%. In order to increase the proportion of anti-idiotype hybrids tolerance to the constant regions of human IgM was established by intraperitoneal administration of disaggregated human gamma globulin 14 days prior to immunization of both male and female mice. The percentage of wells with anti-idiotype activity rose to 16-52% in tolerant male mice. The percentage of anti-idiotype hybrids generated was significantly lower in tolerant female mice. To accelerate the process of anti-idiotype development, a single intrasplenic immunization with soluble idiotype IgM was also evaluated. No anti-idiotype or anti-IgM secreting heterohybrids were formed out of nearly 1400 wells seeded in 3 separate fusions using soluble IgM. When the idiotype IgM was immobilized onto protein A-Sepharose, and then injected intrasplenically, approximately 1% of the wells seeded showed anti-idiotype activity. Thus, a single intrasplenic immunization with immobilized immunoglobulin resulted in significant time saving, while prior tolerization may greatly increase the percentage of anti-idiotype hybrids.

Immunotherapy of human leukemia with antibody to pluripotential K-562 stem cells

Gamma (gamma) globulin was fractionated from the serum of a goat immunized with the pluripotential leukemia cell line K-562. The lyophilized gamma-globulin preparation, termed leukoglobulin, contained about 50% immune IgG and suppressed the proliferation of heterotransplanted leukemia and lymphoma cells of human origin. The main aims of this study were to evaluate the potential therapeutic value of leukoglobulin and to determine its toxicity in humans with terminal leukemia and patients whose disease was unresponsive to current therapy. Two patients with CML, one with AMML, four with ALL, and one with AML were treated once a week for up to 5 weeks with leukoglobulin intravenously at doses ranging from 2 to 29 mg/kg. Leukoglobulin was well tolerated with minimal adverse effects and produced an initial mobilization of blasts from the bone marrow, spleen, and other organs with a parallel increase in the number of blasts in the systemic circulation. Subsequent injections of leukoglobulin led to a sharp decrease and the eventual eradication of blasts from the peripheral blood and bone marrow. Except in patients with CML, immature cells other than blasts also markedly diminished. The results of the clinical trials indicated a synergism with or potentiation of most chemotherapeutic agents used. Two possible uses for a combination of leukoglobulin and antileukemic drugs are indicated by the results we report here; drug-antibody synergism for cases showing no response to chemotherapy alone or leukoglobulin given immediately after chemotherapy is administered to eliminate residual leukemia cells. Alternatively, leukoglobulin can be given as a single therapeutic agent during the induction or maintenance phases of treatment to patients with leukemia resistant to other therapeutic combinations.

Characterization of a monoclonal antibody to L1210 leukaemia

A mouse of monoclonal cell line (L1) was produced by fusing the mouse myeloma P3X63/Ag8 with CD2F1 spleen cells immunized with a highly immunogenic subline of L1210 leukaemia (L1210/DTIC). A very few positive clones (1%) were isolated and one of these was chosen for detailed study. The monoclonal antibody L1 is an IgM immunoglobulin strongly reacting in a complement-dependent cytotoxicity assay against L1210/Cr leukaemia and its more or less immunogenic sublines. The specificity of the L1 antibody against L1210 leukaemia was studied by extensive screening with normal adult and foetal tissues, lymphoid tissues from several independent strains and a panel of the most common experimental tumours, to all of which it was unreactive. Attempts at immunotherapy were carried out in DBA/2 mice challenged with L1210 leukaemia and treated with L1 (ascites) and complement. Although the in vitro cytotoxic titre of ascites fluid from mice bearing hybridoma was very high (10(-7)), no therapeutic effect was obtained in vivo.

Antibody-mediated suppression of grafted lymphoma. IV. Influence of time of tumor residency in vivo and tumor size upon the effectiveness of suppression by syngeneic antibody

In the suppression of the growth of a mouse lymphoma 6C3HED by antibody, the effectiveness of antibody in suppressing growing or established tumor cells and comparable number of freshly injected tumor cells is quantitatively similar. The effectiveness of antibody diminishes markedly when the number of tumor cells per mouse reaches the level of 10(6) due to the development of a macrophage shortage. At the 10(5) tumor cells level, antibody-mediated suppression takes place in an optimal manner and between 10(5) and 10(4) tumor cell numbers, the amount of antibody required to suppress 50% of the tumor cells is directly proportional to the number of tumor cells suppressed.

Immunotherapy of cancer with antibody

A long-term suppression of a transplanted solid tumor that has been growing in a syngeneic animal can be achieved by the administration of antibody against the tumor. The susceptibility of such growing tumor cells to antibody treatment is similar to that of a comparable number of freshly injected tumor cells.

Further observations on the effect of C. parvum and anti-tumour globulin on syngeneically transplanted mouse tumours

The inhibitory effect of an i.v. or i.p. injection of C. parvum on intrastrain transplants of a mammary carcinoma in A/HeJ mice has been confirmed, and it has been shown further that C. parvum inhibits the growth of transplants of sarcomata induced with methylcholanthrene both in this strain (members of which lack the fifth component of complement) and in CBA mice (which are not complement deficient). In experiments with the mammary carcinoma, 2 injections of C. parvum on days + 3 and + 9 were more effective than a single injection on day + 3; injections on days + 3 and + 6, or + 3 and + 12, appeared to be marginally less effective than on days + 3 and + 9, but the difference was not statistically significant.Development of the CBA sarcoma was inhibited to about the same extent if, instead of treating the mouse with C. parvum, the tumour cells were pre-incubated with anti-tumour globulin (ATG) in the absence of complement prior to inoculation, and the effect of combining these procedures was much greater than that of either alone. Pre-incubation with ATG had a similar but less marked effect on the development of the mammary carcinoma but had no effect on the A/HeJ sarcoma. Injection (i.v.) of ATG did not inhibit the growth of any of the tumours in these experiments and possible reasons for this are discussed.