Requirements for successful immunotherapy and chemoimmunotherapy of a murine model of ovarian cancer.

A comprehensive study of nonspecific immunotherapy has been conducted in an established murine model of ovarian cancer in order to determine the relative effectiveness of commonly used bacterial immunostimulants, the importance of the route and schedule of administration of these agents, and their effects in combination with chemotherapy. Implants of 10(5) or 10(6) ovarian tumor cells i.p. kill all syngeneic C3HeB/FeJ mice within 25 days. Corynebacterium parvum (700 microgram/mouse i.p. 24 hr after a 10(5) tumor cell inoculum) cures 75% of the mice; in contrast, neither i.v. nor s.c. administration improves survival rates. After the same tumor challenge, Bacillus Calmette-Guérin was minimally effective at extremely high doses only, while the methanol extraction residue of B. Calmette-Guérin was ineffective. Two days after an implant of 10(6) tumor cells, neither cyclophosphamide, nor cis-diamminedichloroplastinum(II) (cisplatin), nor C. parvum increased survival. Combination of C. parvum with cyclophosphamide or cisplatin resulted in a synergism shown by the 40 and 60% cure rates, respectively. However, combination of C. parvum with an active agent, doxorubicin, resulted in toxicity even in untumored animals. This study demonstrates that therapeutic efficacy of immunotherapy depends critically on the choice of an appropriate agent and route of administration and, to a lesser extent, on the dose and schedule used. The observation provides a rationale for carefully conducted Phase I and Phase II studies of treatment with bacterial immunostimulants, alone or in combination with chemotherapy, in human ovarian cancer.

Lack of histocompatibility antigens on a murine ovarian teratocarcinoma.

We have attempted to generate in vitro lymphocytes cytotoxic to a widely studied model of ovarian cancer in C3HeB/FeJ mice. These attempts were unsuccessful with either syngeneic or allogeneic spleen cells. The following experimental results demonstrated that this murine ovarian tumor lacks histocompatibility antigens. (a) Tumor cells were not lysed by allogeneic lymphocytes presensitized to H-2k spleen cells. (b) Tumor cells did not specifically inhibit the cell-mediated lysis of H-2k spleen cells by presensitized allogeneic lymphocytes. (c) Histoincompatible (H-2b or H-2d) and syngeneic (H-2k) mice all died with identical tumor growth patterns within 25, 30, or 35 days following the i.p. inoculation of 10(6), 10(5), or 10(4) tumor cells, respectively. (d) Tumor cells were not lysed by an anti-H-2k antiserum and complement. (e) Absorption of the anti-H-2k antiserum with tumor cells did not decrease the cytotoxicity of the antiserum. (f) Competitive inhibition of a radioimmunoassay and polyacrylamide gel electrophoresis of immunoprecipitate of radiolabeled tumor extracts failed to demonstrate an H-2 heavy chain, although a normal amount of beta-microglobulin was present. This lack of histocompatibility antigens may explain the failure to generate lymphocytes cytotoxic to this tumor. Thus, this murine ovarian tumor, which has a serologically detectable tumor-associated antigen and can be cured by nonspecific immunotherapy, may provide an excellent model for the study of successful immunotherapy in the absence of histocompatibility antigens and associated cell-mediated reactions.

Objective regressions of T- and B-cell lymphomas in patients following treatment with anti-thymocyte globulin.

We have conducted a clinical trial utilizing anti-thymocyte globulin (ATG) for the treatment of patients with non-Hodgkin's lymphomas. Six patients were treated; 50% reductions in tumor mass of short duration were observed in one patient with a T-cell lymphoma and two patients with B-cell lymphomas. In vitro assays have been performed in an attempt to study the reactivity and potential mechanism of antitumor action of the ATG. The ATG bound to essentially all normal blood mononuclear leukocytes as well as tumor cells from patients with T-, B-, or null cell lymphomas demonstrating its lack of specificity. Furthermore, complement-mediated lysis of normal mononuclear leukocytes, normal T- or B-cells, and tumor cells from two unresponsive patients were all comparable; moreover, since this lysis occurred only at concentrations of ATG that are not attainable in vivo, it is unlikely that complement-mediated cytotoxicity accounts for the responses observed. Peripheral blood lymphocyte counts and total erythrocyte rosettes did decrease during ATG treatment. Thus, objective tumor responses in both B- and T-cell non-Hodgkin's lymphomas can be achieved with a very nonspecific antiserum although significant toxicity resulted. Whether the magnitude or duration of response can be increased with monoclonal antibodies remains to be determined. Future success with serotherapy might require use of either a battery of different monoclonal antibodies or a single monoclonal antibody that can deliver radioisotopes, chemotherapy, or toxins to the tumor cells.

Increased sensitivity of T cells to regulation by normal suppressor cells persists in long-term survivors with Hodgkin's disease.

We have studied the function of T cells in the peripheral blood obtained from long term survivors with Hodgkin's disease in order to determine the sensitivity of those T cells to normal suppressor cell immunoregulatory mechanisms. Concanavalin A-activated suppressor cells from normal donors suppressed the proliferation of lymphocytes obtained from 11 patients (56.8 +/- 3.5 percent) and from 28 allogeneic normal control subjects (39.8 +/- 2.7 percent [p less than 0.001]). When suppressor monocytes from the normal donors were studied, the mean proliferation of lymphocytes from 19 patients was suppressed 76.3 +/- 4.8 percent whereas proliferation of lymphocytes from 26 normal donors was suppressed 46.6 +/- 4.4 percent (p less than 0.0001). There was no tendency for the increased sensitivity to suppression that was observed in either assay system to return to normal as the patients' disease free interval increased from 1.5 years to 12 years. Furthermore, long-term survivors with diffuse histiocytic lymphoma, who had been treated with comparable chemotherapy, had normal sensitivity to the suppressor monocytes (45.1 +/- 3.8 percent). In Hodgkin's disease, the persistent increased sensitivity of T cells to two different normal immunoregulatory cells suggests that the response of the T cell to regulatory signals may be an important cause of the depressed cellular immunity observed in Hodgkin's disease and a clue to the etiology of the disease.