Phase III trial of 5-fluorouracil and leucovorin plus either 3H1 anti-idiotype monoclonal antibody or placebo in patients with advanced colorectal cancer.

BACKGROUND: The monoclonal antibody 3H1 mimics the external structure of the carcinoembryonic antigen (CEA). It therefore has the potential, via the anti-idiotypic network, to stimulate immune responses to CEA that may benefit colorectal cancer patients. PATIENTS AND METHODS: A total of 630 patients with previously untreated metastatic colorectal cancer were randomised in a 2:1 fashion to receive bolus 5-fluorouracil (5-FU) and leucovorin (LV) plus either 3H1 (n = 422) or placebo (n = 208). RESULTS: The addition of 3H1 to 5-FU and LV did not result in increased toxicity. Survival for the full intent-to-treat population was 14.7 months for the 3H1 arm and 15.2 months for the placebo arm (P = 0.80). Anti-CEA antibody responses were observed in 70% of patients treated with 3H1. Patients with a negative CEA response had a median survival of 8.3 months (95% CI 7.5-11.0) compared with patients with a strong response: median survival not reached (P <0.001). CONCLUSION: 3H1 is safe and effectively induces immune responses to CEA. Addition of 3H1 to 5-FU and LV was not shown to improve overall patient outcomes. However, improved survival in patients developing anti-CEA responses to 3H1 are provocative and should be studied in further clinical trials.

Rapid engraftment after allogeneic transplantation of density-enriched peripheral blood CD34+ cells in patients with advanced hematologic malignancies.

BACKGROUND: Acute graft versus host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. Preclinical studies have suggested that a T-cell subset with a CD4-/CD8- double-negative (DN) T-cell phenotype is capable of suppressing GVHD. Double-negative T cells can be mobilized into the peripheral blood with granulocyte colony-stimulating factor (G-CSF) and enriched by density centrifugation. The current study was performed to study the feasibility and safety of applying a density gradient separation technique for enrichment of CD34+ and DN T cells, while depleting CD4+ and CD8+ single-positive (SP) T cells from peripheral blood progenitor cells (PBPCs) for the purpose of allogeneic transplantation. METHODS: Twenty-five patients with advanced hematologic malignancies were treated with a myeloablative preparative regimen consisting of fractionated total body irradiation, etoposide, and cyclophosphamide. Human leukocyte antigen identical donors were mobilized with G-CSF PBPC collected by apheresis. The apheresis product was applied to a single-step density gradient, and the low-density cell population was collected. The low-density cell population was infused as the sole source of allogeneic cells after myeloablative therapy. Graft versus host disease prophylaxis consisted of cyclosporine with or without prednisone. RESULTS: CD34 cell recovery was efficient with a median 72% yield, providing for a median CD34+ cell dose of 6.5 x 10(6)/kg (range,1.0- 13.9 x 10(6)/kg). CD3+CD4+ or CD3+CD8+ SP T cells were depleted by a median of 94.4% (range, 58.8- 99.2%), and the ratio of CD34+:SP T cells increased 10-fold. Double-negative T cells were depleted by 92% (range, 18.8- 99.4%), thus the ratio of DN:SP T cells increased less than 2-fold in 71% of apheresis samples tested. Hematopoietic engraftment was rapid, and there was no occurrence of graft failure in examinable patients. Median time to absolute neutrophil count greater than 0.5 x 10(9)/L and platelet count greater than 20 x 10(9)/L was 10.5 and 12 days, respectively. The incidence of Grade 2-4 acute GVHD was 26% (95% confidence interval [CI], 6-45%), although not all patients were examinable due to an unexpectedly high nonrecurrence mortality that at Day 180 was 62% (95% CI, 40-83%). CONCLUSIONS: These data suggest that T-cell subset manipulation via density gradient separation is a safe procedure and allowed rapid hematopoietic recovery. Selective enrichment of a donor DN T-cell subset was observed in only a few and was not associated with a reduced incidence of GVHD. However, the low-density selected cells still resulted in GVHD, and there was a high treatment-related mortality.

Fluorouracil modulation in colorectal cancer: lack of improvement with N -phosphonoacetyl- l -aspartic acid or oral leucovorin or interferon, but enhanced therapeutic index with weekly 24-hour infusion schedule--an Eastern Cooperative Oncology Group/Cancer and Leukemia Group B Study.

PURPOSE: To investigate mechanism-directed regimens in maximizing the efficacy of fluorouracil (5-FU) in advanced colorected cancer. PATIENTS AND METHODS: Based on promising phase II data, a randomized comparison of various methods for the biochemical modulation of 5-FU was undertaken in patients with advanced colorectal cancer. The control group received single-agent 5-FU as a 24-hour infusion weekly. Patients (N = 1,120) with no prior chemotherapy for metastatic disease were randomized to one of the following arms: arm A, 5-FU 2,600 mg/m2 by 24-hour infusion, weekly; arm B, N-phosphonoacetyl-l-aspartic acid 250 mg/m2 day l, 5-FU 2,600 mg/m2 by 24-hour infusion day 2, weekly; arm C, 5-FU 600 mg/m2 with oral leucovorin (LV) 125 mg/m2 hourly for the preceding 4 hours, weekly; arm D, 5-FU 600 mg/m2 with intravenous (IV) LV 600 mg/m2, weekly; arm E, 5-FU 750 mg/m2/d IV by continuous infusion for 5 days, then 750 mg/m2 weekly, and recombinant interferon alfa-2a 9 million units subcutaneously three times weekly. Median follow-up was 4.8 years. RESULTS: Of the 1,098 assessable patients, 57% had measurable disease. The toxicity of all the regimens was tolerable. Grade 4 or worse toxicity occurred in 11%, 11%, 30%, 24%, and 22% on each arm, respectively; diarrhea was the most common adverse effect. These toxicity patterns favored significantly (P <.001) the 24-hour infusion arms. Median survival (months) by arm was A, 14.8; B, 11.9; C, 13.5; D, 13.6; and E, 15.2. These survival durations did not differ significantly. CONCLUSION: We conclude that a weekly infusion regimen of 5-FU is significantly less toxic than and as effective as 5-FU bolus regimens modulated by either LV or interferon in patients with metastatic colorectal cancer.

Dendritic cell-based treatment of cancer: closing in on a cellular therapy.

PURPOSE: Dendritic cells are the most potent antigen-presenting cells and are critical to initiation of immune responses. Dendritic cells loaded ex vivo with tumor-associated antigen are being administered to cancer patients in an effort to jump-start a potent, cell-mediated anticancer immune response resulting in tumor shrinkage and clinical benefit. PATIENTS AND METHODS: Dendreon Corporation has designed three therapeutic vaccines using blood-derived dendritic cells loaded ex vivo with antigen: Provenge for prostate cancer; Mylovenge for multiple myeloma and other B-cell malignancies; and APC8024 for cancers expressing the HER-2/neu proto-oncogene. RESULTS: Preclinical studies demonstrated that blood dendritic cells matured spontaneously in short-term culture without growth factors, and that fusion of antigens with granulocyte-macrophage colony-stimulating factor enhances antigen uptake and presentation by blood dendritic cells. Phase I/II trials suggest that these dendritic cell-based vaccines are safe and well tolerated. Provenge has demonstrated antitumor activity in hormone-refractory prostate cancer; approximately 20% of patients experienced decreased prostate-specific antigen (i.e., PSA) levels and a similar percentage experienced disease stabilization. Double-blind, placebo-controlled, randomized trials in metastatic, asymptomatic hormone-refractory prostate cancer have been initiated. Phase II data on Mylovenge are similarly encouraging, and expanded phase II testing is ongoing in anticipation of opening phase III trials in 2002. APC8024 is in early clinical development and has shown significant capacity to elicit antigen-specific immune responses. CONCLUSION: Antigen delivery by ex vivo antigen-loaded dendritic cells may be an effective approach to cancer immunotherapy.

Bispecific Antibody MDX-210 for Treatment of Advanced Ovarian and Breast Cancer.

A large number of monoclonal antibodies (MAbs) to various tumor cell lines have been developed (1). However, MAbs have thus far had limited therapeutic impact in oncology, probably in part because many murine MAbs do not effectively recruit immune effector mechanisms, such as complement fixation and antibody-dependent cell-mediated cytotoxicity (ADCC) in humans. Additionally, although humanized MAbs are being developed, when used therapeutically their immunological effectiveness may be limited by high concentrations of nonspecific immunoglobulin (Ig) in patient serum. These nonspecific Ig will compete with conventional MAbs for binding to Type I Fc receptors (FcγRI) on immune effector cells, and may therefore limit conventional MAbs ability to recruit an immune response. Recently, however, clinical efficacy of a humanized MAb directed against HER-2/neu in patients with advanced breast cancer has been demonstrated (2-4). Preclinical data suggests that mechanistically this activity may be as a consequence of modulation of important biologic properties of the HER-2/neu receptor itself, as opposed to through an immunologic mechanism of tumor cell destruction.

Immunotherapy of hormone-refractory prostate cancer with antigen-loaded dendritic cells.

PURPOSE: Provenge (Dendreon Corp, Seattle, WA) is an immunotherapy product consisting of autologous dendritic cells loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase (PAP) linked to granulocyte-macrophage colony-stimulating factor. Sequential phase I and phase II trials were performed to determine the safety and efficacy of Provenge and to assess its capacity to break immune tolerance to the normal tissue antigen PAP. PATIENTS AND METHODS: All patients had hormone-refractory prostate cancer. Dendritic-cell precursors were harvested by leukapheresis in weeks 0, 4, 8, and 24, loaded ex vivo with antigen for 2 days, and then infused intravenously over 30 minutes. Phase I patients received increasing doses of Provenge, and phase II patients received all the Provenge that could be prepared from a leukapheresis product. RESULTS: Patients tolerated treatment well. Fever, the most common adverse event, occurred after 15 infusions (14.7%). All patients developed immune responses to the recombinant fusion protein used to prepare Provenge, and 38% developed immune responses to PAP. Three patients had a more than 50% decline in prostate-specific antigen (PSA) level, and another three patients had 25% to 49% decreases in PSA. The time to disease progression correlated with development of an immune response to PAP and with the dose of dendritic cells received. CONCLUSION: Provenge is a novel immunotherapy agent that is safe and breaks tolerance to the tissue antigen PAP. Preliminary evidence for clinical efficacy warrants further exploration.

Priming tissue-specific cellular immunity in a phase I trial of autologous dendritic cells for prostate cancer.

We attempted to induce therapeutic immunity against prostate-derived tissues in patients suffering from progressive hormone-refractory metastatic prostate carcinoma. Thirteen patients were treated with two infusions, 1 month apart, of autologous dendritic cells (APC8015) preexposed ex vivo to PA2024, a fusion protein consisting of human granulocyte/macrophage-colony stimulating factor (GM-CSF) and human prostatic acid phosphatase (PAP). The infusions were followed by three s.c. monthly doses of PA2024 without cells. Three groups of patients each received PA2024 at 0.3, 0.6, or 1.0 mg/injection. All Ps were two-sided. Treatment was well tolerated. After infusions of APC8015, patients experienced only mild (grade 1-2) short-lived fever and/or chills, myalgia, pain, and fatigue. One patient developed grade 3 fatigue. Four patients developed mild local reactions to s.c. PA2024. Twelve patients were evaluable for response to treatment. Circulating prostate-specific antigen levels dropped in three patients. T cells, drawn from patients after infusions of APC8015, but not before, could be stimulated in vitro by GM-CSF (P = 0.0004) and PAP (P = 0.0001), demonstrating broken immune tolerance against these two normal proteins. Injections of PA2024 did not influence the reactivity of T cells against PAP and GM-CSF. However, antibodies to GM-CSF and, to a much lesser extent, to PAP reached maximum titers only after two or even three injections of PA2024, showing that directly injected PA2024 was involved in stimulation of humoral immunity. Dendritic cells exposed to antigen ex vivo can induce antigen-specific cellular immunity in prostate cancer patients, warranting further studies of this mode of immunotherapy.

Transplantation with low-density autologous PBSC prepared with BDS60 for women with Stage II, III and IV breast cancer.

BACKGROUND: DS60 is a novel buoyant density solution, whose density has been adjusted to enrich PBSC from subjects who have been mobilized with cytokines alone, or cytokines plus chemotherapy. This report describes the use of BDS60 to enrich autologous PBSC that were used for hematological reconstitution after myeloablative chemotherapy in women with breast cancer. METHODS: Fifty-one consecutive patients with high-risk Stage II or III breast cancer or chemotherapy-sensitive Stage IV breast cancer were enrolled. Forty-seven completed treatment and were evaluable. After mobilization with cyclophosphamide (4.0 g/m(2) i.v. once) and filgrastim (10 microg/kg/day), the patients underwent leukapheresis and the products were enriched with BDS60 using the DACS300 Kit. Myeloablative chemotherapy, given on Day -5 through Day -2, consisted of cyclophosphamide (1.5 g/m(2)/day), thiotepa (150 mg/m(2)/day) and carboplatin (200 mg/m(2)/day). RESULTS: Forty-one patients underwent a single leukapheresis procedure to achieve the target number of BDS60-enriched CD34+ cells for transplantation (> or = 2 x 10(6)/kg). Five of the other six patients had less than the target number of cells in the leukapheresis product and thus required 2-4 leukapheresis procedures. Median cell recovery was 76.8% for CD34+ cells, 39.1% for nucleated cells, and 17.7% for platelets. Erythrocyte contamination of the final product was negligible. The median time to sustained neutrophil count > 500/mm(3) was 9 days (range: 8-12) and the median time to platelet count > 20 000/mm(3), without transfusion support, was also 9 days (range: 6-15). There were no late graft failures. Infusion-related adverse events were mild and no adverse events were attributed to the use of BDS60 to enrich CD34+ cells. DISCUSSION: BDS60 is an effective, rapid method for enrichment of CD34+ cells by buoyant density centrifugation and the resulting cell product is safe and effective for engraftment after myeloablative therapy.

Rapid debulking and CD34 enrichment of filgrastim-mobilized peripheral blood stem cells by semiautomated density gradient centrifugation in a closed system.

Filgrastim-mobilized peripheral blood progenitor cells (PBPC) are used for hematopoietic reconstitution after myeloablative therapy for malignancies, but the large number of cells collected in a single apheresis frequently presents a problem for storage or further processing. We have evaluated the use of CD34 Buoyant Density Solution-PBPC, an ultralight-density colloidal silica suspension, for debulking and enrichment of CD34+ cells in PBPC preparations in a semiautomated system. Cells were collected from four filgrastim-treated normal donors using the COBE Spectra. The separation procedure was carried out with Plasma-Lyte A and DNase 5 U/ml using the COBE 2991. Following processing and washing, there was a 26% recovery of nucleated cells, 2.6-fold enrichment of CD34+ cells, 68% recovery of CD34+ cells, 88% recovery of CFU-GM, 73% recovery of BFU-E, 1 log depletion of CD3+ cells, 0.5 log depletion of CD56+ cells, and 1 log depletion of CD19+ cells. These results were not significantly different from those obtained when PBPC were separated over CD34 Buoyant Density Solution-PBPC by centrifugation in tubes. Using CD34 Buoyant Density Solution-PBPC, mononuclear preparations of PBPC can be enriched rapidly for CD34+ cells and depleted of lymphocytes in a semiautomated closed system using reagents produced according to good manufacturing practice (GMP).

A randomized phase II study of ifosfamide/mesna/cisplatin plus G-CSF or etoposide/cisplatin plus G-CSF in advanced non-small cell lung cancer: a Cancer and Leukemia Group B study.

This Phase II study was designed to determine the efficacy of two chemotherapy regimens with G-CSF support for patients with advanced non-small cell lung cancer (NSCLC). One-hundred and one patients with Stage IIIB or IV NSCLC and performance status 0-1 were randomized to receive ifosfamide 2.0 g/m2 days 1-3, mesna 400 mg/m2 at 0, 4, 6 h days 1-3, cisplatin 33 mg/m2 days 1-3 or etoposide 200 mg/m2 days 1-3, cisplatin 35 mg/m2 days 1-3. Both groups received G-CSF 5 micrograms/kg SQ day 4 to the post day 11 absolute neutrophil count > 10 000. For the 47 eligible patients receiving ifosfamide/mesna/cisplatin, the response rate was 26% (95% confidence interval: 14-40%) and the median survival 7.5 months (95% confidence interval: 5.8-11.0 months). Grade 3 or worse toxicities were: neutropenia 75%, thrombocytopenia 70%, infection 21%. There were two treatment-related deaths due to infection. For course 1, the median absolute neutrophil count nadir was 1.3, platelet nadir 96 000 and incidence of febrile neutropenia 16%. For the 48 eligible patients receiving etoposide/cisplatin, the response rate was 21% (95% confidence interval: 11-35%) and median survival 5.8 months (95% confidence interval: 4.5-9.7 months). Grade 3 or worse toxicities were: neutropenia 90%, thrombocytopenia 58%, infection 29%. There were three treatment-related deaths due to infection. For course 1, the median absolute neutrophil count was 0.2, platelet nadir 80 000 and incidence of febrile neutropenia 33%. For both ifosfamide/mesna/cisplatin and etoposide/cisplatin, median duration of Grade IV neutropenia was short (< or = 4 days), time to subsequent courses 21 days and dose delivered > 95% of planned dose. Although G-CSF allowed full doses of drugs to be delivered on schedule, both ifosfamide/mesna/cisplatin and etoposide/cisplatin produced response rates and survival similar to other cisplatin-based regimens. In view of the significant cost of G-CSF and no obvious improvement in response rate, survival or toxicity profile, G-CSF cannot be recommended with these chemotherapy regimens for patients with advanced NSCLC.

Clinical trials of bispecific antibody MDX-210 in women with advanced breast or ovarian cancer that overexpresses HER-2/neu.

MDX-210 is a bispecific antibody (BsAb) that recognizes Fc gamma R1 on monocytes and macrophages and the cell surface product of the HER-2/neu oncogene, which is overexpressed on some breast and ovarian cancers. Clinical trials have demonstrated that treatment with MDX-210 is well tolerated and that MDX-210 is both immunologically and clinically active. Optimization of the dose and schedule of MDX-210 and development of combination treatments with cytokines that modulate immune effector cells will greatly enhance the efficacy of this novel BsAb construct for treatment of tumours that overexpress HER-2/neu. We envision that MDX-210 will be effective for treating patients with tumors that overexpress HER-2/neu, especially in the minimal disease setting.

Phase Ia/Ib trial of bispecific antibody MDX-210 in patients with advanced breast or ovarian cancer that overexpresses the proto-oncogene HER-2/neu.

PURPOSE: MDX-210 is a bispecific antibody that binds simultaneously to type I Fc receptors for immunoglobulin G (IgG) (Fc gamma RI) and to the HER-2/neu oncogene protein product. MDX-210 effectively directs Fc gamma RI-positive effector cells such as monocytes and macrophages to phagocytose or kill tumor cells that overexpress HER-2/neu. The goals of this phase Ia/Ib trial were to determine the maximum-tolerated dose (MTD) and/or the optimal biologic dose (OBD) of MDX-210. PATIENTS AND METHODS: Patients with advanced breast or ovarian cancer that overexpressed HER-2/neu were eligible for treatment. Cohorts of three patients received a single intravenous (IV) infusion of MDX-210 at increasing dose levels from 0.35 to 10.0 mg/m2. RESULTS: Treatment was well tolerated, with most patients experiencing transient grade 1 to 2 fevers, malaise, and hypotension only. Two patients experienced transient grade 3 hypotension at 10.0 mg/m2. Transient monocytopenia and lymphopenia developed at 1 to 2 hours, but no other hematologic changes were observed. Doses of MDX-210 > or = 3.5 mg/m2 saturated > or = 80% of monocyte Fc gamma RI and produced peak plasma concentrations > or = 1 microgram/mL, which is greater than the concentration for optimal monocyte/macrophage activation in vitro. Elevated plasma levels of the monocyte products tumor necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), granulocyte colony-stimulating factor (G-CSF), and neopterin were observed with maximal levels at doses > or = 7.0 mg/m2. Localization of MDX-210 in tumor tissue was demonstrated in two patients. One partial and one mixed tumor response were observed among 10 assessable patients. CONCLUSION: MDX-210 is immunologically active at well-tolerated doses. The MTD and OBD is 7 to 10 mg/m2.

Tumor necrosis factor release by murine macrophages stimulated by the cytotoxic ether lipid 1-O-hexadecyl-2-O-methyl-SN-glycero-3-phosphorylcholine (ET-18-O-OCH3).

The cytotoxic ether lipid 1-O-hexadecyl-2-O-methyl-SN-glycero-3-phosphorylcholine (ET-18-O-OCH3) is a structural analog of the mediator of inflammation platelet-activating factor (PAF). Recent studies demonstrated that ET-18-O-OCH3 activates human monocytes selectively at non-cytotoxic concentrations. The current studies determined the capacity of ET-18-O-OCH3 to stimulate release of TNF alpha by murine peritoneal macrophages. Macrophage receptors for ET-18-OCH3 and PAF were also assessed. ET-18-O-OCH3 and PAF stimulated TNF alpha release by resident BALB/c macrophages in the presence of LPS but not in the absence of this co-factor. In contrast, both ET-18-O_OCH3 and PAF stimulated TNF alpha release by thioglycollate-elicited macrophages in the absence of LPS although release was greater in the presence of this co-stimulus. Optimal stimulation of TNF alpha release occurred at 10(-14)-10(-11) M ET-18-O-OCH3 and PAF. Elicited macrophages and splenic macrophages from C57Bl/6 mice, unlike those from BALB/c mice, did not respond to 10(-15)-10(-8) M ET-18-O-OCH3 or PAF without or with LPS. Scatchard analysis of [3H]PAF binding to elicited BALB/c macrophages revealed the existence of high affinity receptors for PAF. In contrast, there was no evidence for receptors for ET-18-O-OCH3. ET-18-O-OCH3 did not compete with PAF for binding; macrophage activation by ET-18-O-OCH3 was not stereospecific; and, binding studies using [3H]ET-18-O-OCH3 did not reveal saturable binding characteristic of binding to specific receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Soluble normal and mutated DNA sequences from single-copy genes in human blood.

Healthy individuals have soluble (extracellular) DNA in their blood, and increased amounts are present in cancer patients. Here we report the detection of specific sequences of the cystic fibrosis and K-ras genes in plasma DNA from normal donors by amplification with the polymerase chain reaction. In addition, mutated K-ras sequences are identified by polymerase chain reaction utilizing allele-specific primers in the plasma or serum from three patients with pancreatic carcinoma that contain mutated K-ras genes. The mutations are confirmed by direct sequencing. These results indicate that sequences of single-copy genes can be identified in normal plasma and that the sequences of mutated oncogenes can be detected and identified with allele-specific amplification by polymerase chain reaction in plasma or serum from patients with malignant tumors containing identical mutated genes. Mutated oncogenes in plasma and serum may represent tumor markers that could be useful for diagnosis, determining response to treatment, and predicting prognosis.

Phase I trial of a 5-day infusion of L-leucovorin plus daily bolus 5-fluorouracil in patients with advanced gastrointestinal malignancies.

The combination of leucovorin [(6d,l)-5-formyl-tetrahydrofolate] and 5-fluorouracil (5-FU) has increased efficacy compared to 5-FU alone as treatment of advanced colorectal cancer. Leucovorin is metabolized to methylene tetrahydrofolate, which potentiates the antitumor actions of 5-FU by forming a ternary complex of thymidylate synthase, fluorodeoxyuridine and methylene tetrahydrofolate. Only l-leucovorin is metabolized to methylene tetrahydrofolate and forms this ternary complex. However, d-leucovorin may not be inert. d-Leucovorin may impair cellular uptake and metabolism of l-leucovorin, thereby inhibiting the actions of l-leucovorin. Because of this possible limitation to the effectiveness of racemic leucovorin, we have begun to explore the effects of the pure, biologically active isomer, l-leucovorin. In this phase I trial, patients with advanced gastrointestinal malignancies were treated with a 5-day continuous infusion of l-leucovorin and daily intravenous boluses of 5-FU at 370 mg/m2. The dose of l-leucovorin was escalated in groups of three patients at four doses, 200 mg/m2 per day, 400 mg/m2 per day, 700 mg/m2 per day and 1000 mg/m2 per day. Treatment was repeated every 28 days. Seventeen patients with advanced gastrointestinal cancers entered the trial. Sixteen patients were evaluable for toxicity. Toxicity was similar to that expected for leucovorin plus 5-FU. The most common severe toxicities (and the number of patents affected) were: diarrhea (2), mucositis (2), nausea/vomiting (1), and abdominal/rectal pain (2). The maximum tolerated dose of l-leucovorin was 700 mg/m2 per day. Twelve patients were evaluable for response. One complete, one partial and one minor response were observed. All responses occurred among the nine patients with colorectal carcinomas. The combination of l-leucovorin and 5-FU is well tolerated by patients and appears active for treatment of advanced colorectal carcinomas. Additional clinical trials are necessary to determine if l-leucovorin is more effective than d,l-leucovorin for modulating the effectiveness of 5-FU.

Hepatic cancers and their response to chemoembolization therapy. Quantitative image-guided 31P magnetic resonance spectroscopy.

RATIONALE AND OBJECTIVES: Hepatic embolization combined with intra-arterial administration of cytostatic drugs (chemoembolization) is frequently used to treat primary and metastatic cancers to the liver. Quantitative phosphorus-31 magnetic resonance spectroscopy (31P MRS) was used to assess the metabolic state of hepatic cancers and their metabolic response to chemoembolization. METHODS: Fifteen localized 31P MRS studies were performed on five patients with liver tumors. Thirteen healthy volunteers served as controls. Metabolite ratios and molar metabolite concentrations were calculated. RESULTS: Untreated hepatic tumors, relative to normal controls, showed elevated phosphomonoester/adenosine triphosphate (PME/ATP) ratios, reduced concentrations of ATP and inorganic phosphate (Pi), and normal phosphodiester (PDE) concentrations. As an acute response to chemoembolization, ATP, PME, and/or PDE concentrations diminished, whereas Pi concentrations increased or stayed relatively constant. Long-term follow-up after chemoembolization showed decreased PME/ATP and increased ATP concentrations in the absence of changes on standard magnetic resonance and computed tomographic images. CONCLUSIONS: These preliminary spectroscopic data suggest that quantitative 31P MRS can be successfully used to monitor directly metabolic response to hepatic chemoembolization.

Stimulation of tumour necrosis factor release by cytotoxic analogues of platelet-activating factor.

The capacity of cytotoxic analogues of platelet-activating factor (PAF) to stimulate tumour necrosis factor-alpha (TNF-alpha) synthesis and release by human monocytes was determined. Cell-associated TNF-alpha was quantified by protein immunoblotting and released TNF-alpha was quantified by cytotoxicity bioassay. Picomolar concentrations of methoxyPAF, SDZ 62-759, SDZ 68-826, SDZ 62-434 and SRI 62-834 induced a two- to fivefold increase in cell-associated and released TNF-alpha. These compounds were as potent as PAF for stimulating monocytes. In contrast, they lacked direct platelet-activating activity and inhibited platelet aggregation induced by PAF selectivity. The analogues inhibited PAF binding to platelets but not to monocytes. The PAF binding antagonists kadsurenone, BN52021 and WEB2086 inhibited TNF-alpha release induced by 10(-11) M PAF or methoxyPAF by a maximum of only 30-60% whereas they inhibited platelet aggregation by 10(-8) M PAF completely. Monocyte receptors for methoxyPAF were evaluated. Scatchard analysis of [3H]methoxyPAF binding to monocytes revealed large numbers of relatively low affinity receptors (Kd = 5.9 +/- 0.5 x 10(-7) M; 9.1 +/- 4.2 x 10(7) sites/monocyte). These values do not correspond to binding constants of monocyte receptors for PAF and do not account for monocyte activation by picomolar concentrations of methoxyPAF. Cytotoxic analogues of PAF stimulate TNF-alpha synthesis and release but they do not stimulate monocytes by interacting with PAF receptors.

Tumor necrosis factor release by human monocytes stimulated with platelet-activating factor.

Platelet-activating factor (PAF) is a low molecular weight phospholipid which enhances human monocyte cytotoxicity for tumor cells. In the current studies, the capacity of PAF to stimulate release of tumor necrosis factor alpha (TNF alpha) by human monocytes was assessed. PAF induced maximal TNF alpha synthesis 2-3 hr after monocyte stimulation as assessed by dot blotting of cell-associated TNF alpha using polyclonal anti-TNF antibody. Maximal net release of TNF alpha occurred 5-16 hr after monocyte stimulation, as assessed by a specific ELISA. Dose-response studies revealed that a maximal two- to three-fold increase in release of TNF alpha occurs at 10-100 pM PAF. LysoPAF and the optical isomer of PAF did not stimulate release of TNF alpha, suggesting that stimulation is mediated by specific PAF receptors. Scatchard analysis of [3H]PAF binding to monocyte membranes revealed 651 +/- 495 binding sites/monocyte with a Kd of 4.7 +/- 4.2 x 10(-10) M. PAF is a structurally unique activator of monocytes whose interactions with TNF alpha and other cytokines may be critical to host defense against tumors.