Studies on red cell aplasia. V. Presence of erythroblast cytotoxicity in G-globulin fraction of plasma.

The marrow cells of a patient with pure red cell aplasia markedly increased their rate of heme synthesis when they were freed from the host environment and were incubated in vitro. When the red cell aplasia was treated with cyclophosphamide and prednisone, marrow cell incorporation of (59)Fe into heme in vitro increased several weeks before a reticulocytosis was apparent, and was the earliest effect noted. The plasma gammaG-globulins of this patient inhibited heme synthesis by normal marrow cells or the patient's own marrow cells obtained after remission of the disease. Since the inhibition of heme synthesis could be the result of damage to erythroblasts, the patient's posttreatment marrow cells or normal marrow cells were labeled with (59)Fe and were then incubated with the patient's pretreatment, treatment, and posttreatment gammaG-globulins as well as normal gammaG-globulins. At the end of this incubation the supernatant and cells were separated and counted. Heme was extracted and also was counted. Treatment of the cells with the patient's pretreatment gammaG-globulins resulted in a release of 40% of the radioactive heme from the cells. This represented the loss of radioactive hemoglobin and was an index of erythroblast cytotoxicity. A progressive disappearance of the cytotoxic factor in the gammaG-globulins occurred in the 3 wk period preceding the onset of reticulocytes in the patient's blood. Posttreatment and normal gammaG-globulins did not produce this effect and increased injury of red cells and lymphocytes was not produced by the patient's pretreatment gammaG-globulins. These studies demonstrate a method for measuring erythroblast cytoxicity and show that red cell aplasia is associated with gammaG-globulins that specifically damage erythroblasts. Whether interference with new erythroblast development also occurs and contributes to the inhibition of heme synthesis has not yet been ascertained.

Efficacy of 2'-deoxycoformycin in hairy-cell leukemia: a study of the National Cancer Institute of Canada Clinical Trials Group.

Thirty-one patients with hairy-cell leukemia were treated with 2'-deoxycoformycin (DCF) in a National Cancer Institute of Canada multicenter trial. The DCF was administered in a cycle (4 mg/m2 iv weekly X 3), which was repeated every 8 weeks. Following a complete remission, consolidation was done with two further cycles of DCF. Of 28 patients evaluable for response, 25 obtained a complete remission; 3 had a partial response. To date there has been only one relapse; the median time with no therapy was 429.5 days (range 99-743 days). Toxicity was moderate and included nausea and vomiting, lethargy, and skin rash; with the first cycle of treatment, neutropenia and an increased incidence of fever or infection were also observed. We conclude that low-dose DCF is highly effective in treating hairy-cell leukemia.

Long-term outcome following treatment of hairy cell leukemia with pentostatin (Nipent): a National Cancer Institute of Canada study.

We have previously demonstrated that pentostatin (Nipent; SuperGen, San Ramon, CA) is highly effective in the treatment of hairy cell leukemia and report here the long-term outcome of this study. Pentostatin was administered intravenously in cycles of 4 mg/m2 weekly x 3 repeated every 8 weeks. Patients who achieved a complete remission (CR) received two further cycles for consolidation. Of 28 evaluable patients, 25 achieved a CR and three a partial remission. Twenty-three patients are alive at a median follow-up duration of 118 months (range, 55 to 133 months). Of the 25 patients who achieved a CR, 14 (56%) remain in CR at a median of 119 months (range, 109 to 133 months) from the time of CR. Nine additional patients relapsed at a median time of 49 months (range, 15 to 122 months). Only three of the relapsed patients have required treatment: two patients who received cladribine achieved CRs; the third received interferon-alpha and died from hairy cell leukemia. The three patients in partial remission continue to have normal blood counts at 58, 105, and 120 months. Five patients have developed a second malignancy: one mycosis fungoides and four solid tumors. Three patients died from the second malignancies. There were no treatment-related deaths due to toxicity or opportunistic infection. Pentostatin is a highly effective agent for hairy cell leukemia and produces prolonged remissions in the majority of patients.

An Eastern Cooperative Oncology Group phase II study of single agent DHAD, VP-16, aclacinomycin, or spirogermanium in metastatic pancreatic cancer.

There were 80 patients with measurable metastatic or unresectable pancreatic cancer randomly assigned to treatment with either DHAD, VP-16, aclacinomycin, or spirogermanium. There were no complete or partial responses. Two deaths from leukopenia occurred in patients treated with DHAD. One patient receiving spirogermanium experienced a seizure. No other life-threatening toxicities occurred. Maximal toxicities were not significantly more frequent with any treatment group. Median survival was 10 weeks, and median time to progression was only 6 weeks, with no difference among these four therapies.

Studies on pure red cell aplasia. Maintenance therapy with immunosuppressive drugs.

Two patients with pure red cell aplasia, whose marrow cells were capable of increasing their rate of haem synthesis when incubated in vitro with erythropoietin concentrate, had a complete remission associated with the administration of cyclophosphamide and prednisone. Both patients relapsed when the drugs were withdrawn. The patients again went into remission when therapy was reinstituted. Maintenance of normal erythropoiesis was dependent on the continued administration of these drugs. This study provides additional evidence for a causal relationship between immunosuppressive therapy and the resumption of erythropoiesis in patients with this disease and demonstrates the value of this therapy for the maintenance of a remission.

Detection of cytotoxic antibody to erythroblasts.

A two-stage test of cytotoxicity for erythroblasts has been developed that is faster and more sensitive than a previous method. Release of 59Fe from erythroid precursors was used as an index of cytotoxic injury. Optimal release was obtained by pretreating the labeled marrow cells with 0.46M reduced glutathione (GSH) at pH 8.0 for 1 hour at 37 degrees C. The first-stage test plasmas or IgG globulins were incubated with the treated cells at 22 degrees C. for 1 hour and the second-stage source of complement was incubated with the cells for 1 hour at 37 degrees C. These changes permitted cytotoxic plasmas to be detected when they previously would not have been identified. Substitution of the GSH by trypsin or neuraminidase did not yield comparable results. Measurement of the cytotoxicity for GSH-treated cells by the trypan blue exclusion technique showed that the loss of exclusion of trypan blue by marrow erythroblasts increased with an increased release of 50Fe. No cytotoxicity was detected if complement was inactivated at 56 degrees C. The results observed with trypan blue and the occurence of cytotoxicity with the addition of IgG globulins and complement indicate that this system can be used to detect cytotoxic antibody to erythroblasts.

Phase II study of dibromodulcitol in colorectal, kidney, and other carcinomas.

In a phase II study dibromodulcitol (DBD), an alpha-omega dibrominated hexitol, was used to treat 99 previously treated patients with colon, rectal, kidney, and other tumors. Six patients were ineligible and 10 patients were nonevaluable for response. Aside from thrombocytopenia toxicity was moderate. Twenty-three patients had platelet nadirs of less than 50,000/mm3 and there were three thrombocytopenic-associated drug deaths. One of 21 rectal and 1 of 13 kidney cancer patients entered a remission. All but seven patients had received previous treatment with one or more cytotoxic agents. Previously treated patients with colorectal and kidney cancer appear to be resistant to DBD.