Adjuvant therapy for melanoma in dogs: results of randomized clinical trials using surgery, liposome-encapsulated muramyl tripeptide, and granulocyte macrophage colony-stimulating factor.

Spontaneous canine oral melanoma (COM) is a highly metastatic cancer, resistant to chemotherapy, and can serve as a model for cancer immunotherapy. Liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) can activate the tumoricidal activity of the monocyte-macrophage system following i.v. injection. The objective of these studies was to evaluate the therapeutic effectiveness of L-MTP-PE administered alone and combined with recombinant canine granulocyte macrophage colony-stimulating factor (rcGM-CSF) in dogs undergoing surgery for oral melanoma. Ninety-eight dogs with histologically confirmed, clinically staged, oral melanoma were entered into two randomized, double-blind, surgical adjuvant trials. In trial 1, 50 dogs were stratified based on clinical stage and randomized to once a week L-MTP-PE or lipid equivalent (control). When all of the clinical stages were combined, no difference in disease-free survival or in survival time (ST) were detected. However, within stage I, dogs receiving L-MTP-PE had a significant increase in ST compared with control, with 80% of the dogs treated with L-MTP-PE still alive at >2 years. Within each stage II and stage III, there was no difference detected between the treatment groups. In trial 2, 48 dogs were stratified on the basis of clinical stage and extent of surgery (simple resection or radical excision), treated with L-MTP-PE two times a week, and randomized to rcGM-CSF or saline (placebo) given s.c. daily for 9 weeks. Within each stage and when all of the stages were combined, there was no difference between the treatment groups. In both studies, stage I COM is associated with a better prognosis. No effect on survival was observed with regard to tumor location in the oral cavity, sex, type/extent of surgery, or age. In a subset of dogs tested, pulmonary alveolar macrophage cytotoxicity was enhanced with combined rcGM-CSF and L-MTP-PE but not in dogs treated with L-MTP-PE alone. The present study indicates that after surgery, L-MTP-PE administered alone or combined with rcGM-CSF showed no significant antitumor activity in treating advanced stage COM. In early stage COM, L-MTP-PE was shown to result in a prolongation of ST. Furthermore, this study provides additional rationale for the use of the dog model for human malignant melanoma.     

Liposomal muramyl tripeptide phosphatidyl ethanolamine: ifosfamide-containing chemotherapy in osteosarcoma

Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE) is a synthetic biological investigational agent used for treating osteosarcoma. It has been used in both canine and human osteosarcoma to reduce pulmonary metastases, the most common pattern of treatment failure for sarcomas. L-MTP-PE has been well tolerated using the concept of biological cancer therapy during chemotherapy. The use of L-MTP-PE with ifosfamide is the best studied combination with single agent chemotherapy. This may represent a new treatment choice for osteosarcoma patients receiving ifosfamide. Such patients include those with a poor initial histological response to primary therapy and/or metastatic disease including pulmonary metastases. Reduction of side effects of L-MTP-PE, such as fever and/or flu-like symptoms, with ibuprofen has not reduced efficacy. Since improved symptom control is possible using drug combinations that are especially effective for delayed nausea, outpatient high-dose ifosfamide chemotherapy combined with L-MTP-PE may lead to a safe and effective therapy while maintaining the patients' quality of life.     

Liposomal muramyl tripeptide phosphatidyl ethanolamine: a safe and effective agent against osteosarcoma pulmonary metastases

Osteosarcoma is the most common form of primary malignant bone tumor. The use of chemotherapy drugs with many side effects, including high-dose methotrexate, doxorubicin, cisplatin and ifosfamide, has greatly improved osteosarcoma survival compared with surgery alone. However, for 20 years, overall survival remained at a plateau of 60-70% in nonmetastatic disease and 20-30% in metastatic osteosarcoma owing to lung metastases. Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE) is a new agent that improves overall osteosarcoma survival (chemotherapy without L-MTP-PE 70% versus with L-MTP-PE 78%; p = 0.03). L-MTP-PE offers additional benefit for osteosarcoma treatment in combination with chemotherapy, particularly ifosfamide-containing regimens. Clinical experience indicates that side effects such as fever are temporary and controlled or prevented with ibuprofen and/or acetoaminophen premedication; severe side effects are rare. Although surgery will remain the main approach for osteosarcoma treatment of lung metastases, L-MTP-PE combined with other modalities, including chemotherapy, appears to be of benefit in these patients as well.     

Influence of chemotherapy administration on monocyte activation by liposomal muramyl tripeptide phosphatidylethanolamine in children with osteosarcoma

The purpose of these studies was to determine whether chemotherapy interfered with the ability of peripheral blood monocytes from patients with osteosarcoma to respond to the liposome-encapsulated activating agent muramyl tripeptide phosphatidylethanolamine (L-MTP-PE). This was done in preparation of designing an adjuvant therapy protocol that includes L-MTP-PE combined with chemotherapy postoperatively for the treatment of primary osteosarcoma. The majority of patients who fail current adjuvant chemotherapy do so while on chemotherapy. Therefore, we believe it is important to combine L-MTP-PE with chemotherapy early in the treatment course rather than waiting until all chemotherapy cycles are completed. The tumoricidal properties of monocytes from patients with osteosarcoma could be activated by L-MTP-PE to levels equal to or greater than those expressed by normal control monocytes. No intrinsic monocyte defect could be demonstrated. Single-agent chemotherapy consisting of cisplatin (CPD), high-dose methotrexate (MTX), Cytoxan (CTX, cyclophosphamide; Bristol-Myers Co, Evansville, IN), or Adriamycin (ADR, doxorubicin; Adria Laboratories, Columbus, OH) did not interfere with this activation process. There was even a suggestion of enhanced activation potential following the administration of ADR. However, when both ADR and CTX were administered together on the same day, profound suppression in monocyte activation was observed. This suppressed function returned to normal by 3 weeks postcombination therapy. We therefore conclude that L-MTP-PE can be combined with ADR, CPD, MTX, or CTX as single agents but recommend that ADR plus L-MTP-PE is the most effective combination. By contrast, we discourage the use of L-MTP-PE when ADR and CTX are given together.     

Macrophages inhibit human osteosarcoma cell growth after activation with the bacterial cell wall derivative liposomal muramyl tripeptide in combination with interferon-γ

Background

In osteosarcoma, the presence of tumor-infiltrating macrophages positively correlates with patient survival in contrast to the negative effect of tumor-associated macrophages in patients with other tumors. Liposome-encapsulated muramyl tripeptide (L-MTP-PE) has been introduced in the treatment of osteosarcoma patients, which may enhance the potential anti-tumor activity of macrophages. Direct anti-tumor activity of human macrophages against human osteosarcoma cells has not been described so far. Hence, we assessed osteosarcoma cell growth after co-culture with human macrophages.

Methods

Monocyte-derived M1-like and M2-like macrophages were polarized with LPS + IFN-γ, L-MTP-PE +/− IFN-γ or IL-10 and incubated with osteosarcoma cells. Two days later, viable tumor cell numbers were analyzed. Antibody-dependent effects were investigated using the therapeutic anti-EGFR antibody cetuximab.

Results

M1-like macrophages inhibited osteosarcoma cell growth when activated with LPS + IFN-γ. Likewise, stimulation of M1-like macrophages with liposomal muramyl tripeptide (L-MTP-PE) inhibited tumor growth, but only when combined with IFN-γ. Addition of the tumor-reactive anti-EGFR antibody cetuximab did not further improve the anti-tumor activity of activated M1-like macrophages. The inhibition was mediated by supernatants of activated M1-like macrophages, containing TNF-α and IL-1β. However, specific blockage of these cytokines, nitric oxide or reactive oxygen species did not inhibit the anti-tumor effect, suggesting the involvement of other soluble factors released upon macrophage activation. While LPS + IFN-γ–activated M2-like macrophages had low anti-tumor activity, IL-10–polarized M2-like macrophages were able to reduce osteosarcoma cell growth in the presence of the anti-EGFR cetuximab involving antibody-dependent tumor cell phagocytosis.

Conclusion

This study demonstrates that human macrophages can be induced to exert direct anti-tumor activity against osteosarcoma cells. Our observation that the induction of macrophage anti-tumor activity by L-MTP-PE required IFN-γ may be of relevance for the optimization of L-MTP-PE therapy in osteosarcoma patients.     

Phase II study of liposomal muramyl tripeptide in osteosarcoma: the cytokine cascade and monocyte activation following administration.

PURPOSE: A phase II trial that uses liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) in patients with relapsed osteosarcoma is underway. To determine if in vivo cytokine induction plays a role in the mechanism of action of L-MTP-PE, we investigated the circulating cytokine levels of 16 patients who were undergoing therapy. PATIENTS AND METHODS: Patients had histologically proven osteosarcoma and pulmonary metastases that developed either during adjuvant chemotherapy or that were present at diagnosis and persisted despite chemotherapy. Patients were rendered disease-free by surgery. The major goal of the study was to improve the disease-free interval in this high-risk group. L-MTP-PE 2 mg/m2 was infused during a 1-hour period twice a week for 12 weeks, then once a week for 12 weeks. Serial blood samples were collected after L-MTP-PE administration and were assayed for cytokine levels (tumor necrosis factor-alpha [TNF alpha] interleukin-1 alpha [IL-1 alpha], IL-1 beta, IL-6, interferon-gamma [IFN-gamma], neopterin, C-reactive protein). RESULTS: After the infusion of L-MTP-PE, there was rapid induction of circulating TNF alpha and IL-6. TNF alpha levels peaked 1 to 2 hours after infusion in 10 of 16 patients, whereas peak IL-6 levels were detected at 2 to 3 hours in all patients. Induction of circulating TNF alpha and IL-6 was evident only after the first dose of L-MTP-PE. Neither IL-1 alpha nor IL-1 beta was detected in the plasma. Neopterin levels increased at 24 hours postinfusion, which indicated macrophage activation, and were not related to the induction of circulating IFN-gamma. C-reactive protein was elevated in all patients at 24 hours and decreased by 72 hours. Unlike circulating TNF alpha and IL-6, elevations in C-reactive protein and neopterin could be detected throughout the treatment course. CONCLUSION: It is concluded that L-MTP-PE has specific biologic effects in patients with osteosarcoma that may be important to the drug's immunostimulatory capacity and its effectiveness as an antitumor agent.     

Tumoricidal activation of murine resident peritoneal macrophages by interleukin 2 and tumor necrosis factor alpha.

The capacity of recombinant human interleukin 2 (rH-IL2), alone or in combination with recombinant tumor necrosis factor (r-TNF alpha), to activate murine resident peritoneal macrophages to a tumoricidal state was examined. Resident peritoneal exudate cells from C57BL/6 mice were cultured for 18 h with activating agents and washed and the adherent cells (macrophages) were assessed for cytolytic activity against radiolabeled target tumor cells (EL4, P815). Under these conditions, rH-IL2 alone activated macrophages to a tumoricidal state in a concentration dependent fashion. Neither murine nor human r-TNF alpha alone had any activating effect but, when combined with rH-IL2, further stimulated rH-IL2-inducible responses. Using polymyxin B, it was shown that macrophage activation was not due to an inadvertent lipopolysaccharide contamination of the r-TNF alpha or rH-IL2 preparations. It was also unlikely that target cell lysis was a direct result of increased TNF alpha production by rH-IL2 stimulated macrophages since P815 is totally resistant to lysis by r-TNF alpha. Although the lytic effector function was mediated by adherent cells, nonadherent peritoneal exudate cells were required for activation to occur. Furthermore, antisera against murine gamma-interferon, when added to activation cultures, reduced the level of cytolytic activity which developed. These data suggest that rH-IL2-induced peritoneal macrophage activation requires stimulation of nonadherent cells and is dependent upon gamma-interferon mediated mechanisms.     

Modulation of tumoricidal activity, induced in bone-marrow-derived mononuclear phagocytes by interferon gamma or Corynebacterium parvum, by interferon beta, tumor necrosis factor, prostaglandin E2, and transforming growth factor beta

Among a series of agents, including various interleukins and growth factors, only interferon gamma (IFN gamma) and heat-killed Corynebacterium parvum (CP) organisms were able to elicit, within 24 hr, tumoricidal activity in bone-marrow-derived mononuclear (BMM) phagocytes. In subsequent experiments, the abilities of interferon beta (IFN beta), tumor necrosis factor alpha (TNF alpha), prostaglandin E2 (PGE2), and transforming growth factor beta (TFG beta), alone or in combinations of 2, to modulate tumoricidal activity triggered in BMM phagocytes by IFN gamma or CP, were compared. In concentrations secreted by macrophages under physiological conditions, these agents proved potent in modulating induction and/or expression of tumoricidal activity. However, their ability to interfere with tumoricidal activity varied considerably, depending on the extent of macrophage differentiation and/or functional responsiveness, the pathway of macrophage activation, the type, concentration and combination of the macrophage secretory molecules, and on whether the agents were present during induction and expression or only during expression of tumoricidal activity. In showing that IFN beta and TNF alpha were mostly enhancing and TGF beta mostly suppressive, whereas PGE2 suppressed induction but enhanced expression of tumoricidal activity, our findings provide further support for the concept that these macrophage-derived molecules have a key role in autocrine regulation of macrophage functional activities.     

Induction of HLA class II antigens in osteosarcoma cells by interferons and tumor necrosis factor alpha.

In this study we have evaluated the ability of interferons (IFNs) alpha, beta, gamma and Tumor Necrosis Factor (TNF) alpha to modulate the expression of the Major Histocompatibility Complex (MHC) antigens in human osteosarcoma cells. The osteosarcoma cell lines Saos-2 and U-2 OS, treated in vitro with IFNs and TNF alpha, showed an increased expression of class I HLA antigens. However, only IFN gamma and, to a lower extent, IFN beta induced the expression of class II HLA antigens. These effects were dose and time-dependent. Simultaneous treatment with IFN gamma and IFN beta or TNF alpha, which by itself was unable to induce the expression of class II HLA antigens, produced different effects on the two osteosarcoma cell lines: in Saos-2 IFN beta and TNF alpha amplified the effects obtained with IFN gamma alone; in U-2 OS, TNF alpha increased the expression induced by IFN gamma on class II HLA antigens, whereas IFN beta antagonized the effects of IFN gamma. IFN alpha did not influence the induction of class II HLA antigens by IFN gamma in the two osteosarcoma cell lines. IFNs have been introduced in some clinical protocols for the treatment of osteosarcoma, based on their antiproliferative activity. Our findings may contribute to a better knowledge of the effects of IFNs and TNF alpha in osteosarcoma by showing the existence of more complex interactions.     

Combined effects of a third-generation bisphosphonate, zoledronic acid with other anticancer agents against murine osteosarcoma

Bisphosphonates (BPs) are widely used to treat bone diseases and also appear to possess direct antitumour activity. We have previously reported that third-generation BPs such as zoledronic acid (ZOL) and minodronic acid (YM529) synergistically augment the effects of anticancer agents in various cancer cells. Recently, we have also reported the antitumour effects of YM529 on murine osteosarcoma cells. As YM529 has not been clinically available, we herein focused on the anti-osteosarcoma effects of ZOL which is clinically available. In addition to ZOL alone, we evaluated the concurrent or sequential combined effects of ZOL with other anticancer agents against murine osteosarcoma cell lines. ZOL showed almost same anti-osteosarcoma activity compared with YM529 and more sensitive growth inhibitory effects against osteosarcoma cells than normal cells. Moreover, ZOL acted synergistically in vitro when administered concurrently with paclitaxel (PAC) or gemcitabine (GEM), not only in wild-type osteosarcoma cells but also in P-glycoprotein (P-gp)-overexpressing osteosarcoma cells, which were much less sensitive against each anticancer agent. Furthermore, 24 h of ZOL pretreatment significantly augmented the sensitivity of doxorubicin (DOX), PAC or GEM against osteosarcoma cells. These findings suggest that combined administration of ZOL with other anticancer agents may improve the osteosarcoma treatment.     

Interleukin-13-regulated M2 macrophages in combination with myeloid suppressor cells block immune surveillance against metastasis

CD1-deficient mice reject established, disseminated 4T1 metastatic mammary cancer and survive indefinitely if their primary mammary tumors are surgically removed. This highly effective immune surveillance is due to three interacting mechanisms: (a) the generation of inducible nitric oxide synthase (iNOS)-producing M1 macrophages that are tumoricidal for 4T1 tumor cells; (b) a rapid decrease in myeloid-derived Gr1(+)CD11b(+) suppressor cells that are elevated and down-regulate the CD3zeta chain when primary tumor is present and that suppress T cells by producing arginase; and (c) production of activated lymphocytes. Macrophages from wild-type BALB/c mice are polarized by interleukin-13 (IL-13) towards a tumor-promoting M2 phenotype, thereby inhibiting the generation of tumoricidal M1 macrophages. In contrast, CD1(-/-) mice, which are deficient for IL-13 because they lack IL-13-producting NKT cells, generate M1 macrophages that are cytotoxic for 4T1 via the production of nitric oxide. Although tumoricidal macrophages are a necessary component of immune surveillance in CD1(-/-) mice, they alone are not sufficient for tumor resistance because IL-4Ralpha(-/-) mice have M1 macrophages and retain high levels of myeloid suppressor cells after surgery; in addition, they are susceptible to 4T1 metastatic disease. These results show that effective immune surveillance against established metastatic disease is negatively regulated by IL-13 and requires the induction of tumoricidal M1 macrophages and lymphocytes combined with a reduction in tumor-induced myeloid suppressor cells.     

Effect of recombinant tumor necrosis factor on tumoricidal activation of murine macrophages: synergism between tumor necrosis factor and gamma-interferon

The activation of tumoricidal murine macrophages by recombinant human tumor necrosis factor (rH-TNF) alone or in combination with recombinant murine gamma-interferon (rM-IFN-gamma) was examined. When used alone, rH-TNF (10(-1)-10(5) units/ml) did not induce macrophage tumoricidal activity against TNF-insensitive P815 mastocytoma cells. Combining rH-TNF with rM-IFN-gamma resulted in the synergistic induction of tumoricidal activity in resident peritoneal macrophages. This synergistic effect was not due to contaminating bacterial lipopolysaccharide. A comparative study using recombinant murine tumor necrosis factor (rM-TNF) showed that rM-TNF alone also could not stimulate murine macrophages and there was no significant difference between effects of rM-TNF and rH-TNF on macrophage activation in the presence of rM-IFN-gamma. In experiments comparing sequential to simultaneous exposure of macrophages to rH-TNF and rM-IFN-gamma, it was found that: (a) when macrophages are primed with rM-IFN-gamma, rH-TNF serves only as a very weak triggering signal for tumoricidal activation; and (b) marked activation is obtained only when macrophages are exposed to the two cytokines simultaneously. These results suggest that TNF has an autocrine regulatory function in concert with lymphokines in macrophage-mediated host defense against tumors.     

In vitro and in vivo effect of adriamycin therapy on monocyte activation by liposome-encapsulated immunomodulators

The purpose of these studies was to determine the effect of Adriamycin (ADR) on the ability of liposome-encapsulated immunomodulators to activate human blood monocytes to the tumoricidal state. We undertook these experiments because we envisioned using encapsulated activators in addition to chemotherapy to destroy pulmonary micrometastases in patients with osteosarcoma (OS). Prior to the initiation of such therapy, it was important to determine whether chemotherapy interferes with monocyte function. First, human peripheral blood monocytes were isolated from normal donors and preincubated with ADR (0.5-500 ng/ml) for 1 h and then washed prior to the addition of free or liposome-encapsulated activators. After 18-24 h incubation, the activating agents were washed off and [125I]IdUrd-labeled A375 melanoma cells were added. Lysis of radiolabeled tumor cells was quantified 72 h later. Monocytes were also incubated with ADR for 24 h in the presence of free or liposome-encapsulated activators and their cytotoxicity quantified. ADR had no effect on the ability of either free or liposome-encapsulated agents to activate monocyte tumoricidal function. We also studied the in vivo effect of ADR therapy on monocyte function in nine patients with OS. At the time of diagnosis and 1 month after ADR therapy (75 mg/m2) patient monocytes could be activated to the tumoricidal state by liposome-encapsulated agents at levels equal to or greater than pretherapy levels. Monocytes isolated from four patients with OS 1 day after ADR therapy and then activated by liposome-encapsulated agents also demonstrated tumoricidal activity. These studies indicated that the monocytes isolated from osteosarcoma patients treated with ADR can be activated in vitro to kill tumor cells and that additional therapy with liposome-encapsulated immunomodulators may be combined with ADR in the treatment of metastatic pulmonary OS.     

Metastatic osteosarcoma: a review of current issues in systemic treatment

Purpose. Original articles and abstracts published between January 1991 and January 1997 were selected according to specified criteria and reviewed to provide answers to five interesting questions about the systemic treatment of metastatic osteosarcoma.Results.(1) In patients with metastatic disease at presentation, what is the outcome after intensive multi-agent chemotherapy?Historically, survival has been poor, but may be improving with the use of ifosfamide-containing regimens.(2) Can response to new agents be evaluated better in patients who have received no previous chemotherapy?Based on limited data, this is probably true.(3) Is the response to neo-adjuvant chemotherapy, as determined by histopathology, similar for the primary tumor and synchronous pulmonary metastases?With intensive multi-agent chemotherapy, good histological response rates are in the range 70-90% for both groups.(4) What is the outcome, after intensive combined modality treatment with chemotherapy and surgery, in patients relapsing with metastases after previous adjuvant chemotherapy, and what are the important prognostic factors?Outcome is highly variable, but 5-year survival ranges between 25 and 50% and a good outcome is more likely if recurrent disease is limited to resectable lung metastases.(5) Can a biological agent (L-MTP-PE) prolong the time to relapse in patients with resected metastatic osteosarcoma?Preliminary data suggest that this is possible, but more studies are required.     

Inhalation chemotherapy for macroscopic primary or metastatic lung tumors: proof of principle using dogs with spontaneously occurring tumors as a model.

This study represents part of an effort to determine the safety and efficacy of inhaled antineoplastic drugs, using pet dogs with spontaneously arising primary and metastatic lung cancers (including sarcoma, carcinoma, and malignant melanoma) as a model. Dogs received new formulations of either paclitaxel (PTX) or doxorubicin (DOX) by the inhalation route every 2 weeks using a specially designed aerosol device. Response was assessed radiographically using the indices of tumor nodule number and volume measurement of discrete pulmonary nodules. Dogs experiencing progressive disease after two consecutive treatments were crossed over to receive the alternate compound. In 24 dogs, 6 (25%) responses were noted including 5 partial responses (PR) and 1 complete response. These include 4 (22.2%) of 18 responses to DOX and 2 (13.3%) of 15 responses to PTX. Responses were noted with osteosarcoma (including three dogs with metastatic osteosarcoma that had failed prior systemic chemotherapy), liposarcoma, hemangiosarcoma, and undifferentiated sarcoma. One dog with mammary carcinoma experienced a 47% reduction in volume after PTX inhalation, just shy of PR criteria. One dog with liposarcoma is experiencing a long-term (>12 months) stabilization of disease on PTX. To date, no systemic toxicities have been observed with either PTX or DOX inhalations. Local (pulmonary) toxicity was not observed with PTX; however, changes consistent with pneumonitis/fibrosis were observed in some dogs receiving DOX. Only one of these dogs showed clinical signs, which were responsive to steroid and antitussive therapy. These data represent "proof of principle" for the avoidance of systemic toxicity while delivering efficacious local drug levels by the inhalation route.     

Possible participation of tumoricidal macrophages in the therapeutic effect of bleomycin on a transplantable rat fibrosarcoma

When bleomycin (BLM) (5 mg/kg/day) was administered i.p. to WKA rats for 5 days from the eighth day after KMT-17 implantation, the therapeutic effects of BLM were demonstrated by complete tumor regression in 50% of the cases and prolongation of the mean survival time of the remainder [survival days, 44.3 +/- 13.6 (SD)]. The combined administration of an antimacrophage agent, carrageenan, with BLM significantly inhibited the therapeutic effects of BLM (cure rate, 33%; survival days, 29.8 +/- 5.8). By means of a Winn assay, the tumor neutralizing activity of both spleen cells and peritoneal cells (PC) against KMT-17 cells was found to be augmented in BLM-treated tumor bearing rats as compared with that in nontreated tumor bearing rats. The enhanced tumor neutralizing activity of spleen cells was not abolished by an anti-rat T-cell serum plus complement treatment and was present in an adherent macrophage enriched population. Similarly, an in vitro [125I]iododeoxyuridine release test enabled us to observe the enhancement of the cytotoxic activity of adherent spleen cells and adherent PC in BLM-treated rats. The cytotoxic activity of the PC of BLM-treated rats was not specific to KMT-17 cells alone but was also observed to operate against antigenically different tumor cells such as WFT-2N, KST-20, and K562 cells. An in vitro carrageenan treatment of PC taken from BLM-treated rats reduced their cytotoxic activity. At the same time, the combined administration of carrageenan and BLM also reduced the cytotoxic activity of PC. These results suggest that the tumoricidal activity of macrophages in tumor bearing rats is augmented after BLM therapy and that the activated tumoricidal macrophages may participate in the host-mediated antitumor effects of BLM.     

Type-1 transforming growth factor-beta differentially modulates tumoricidal activity of murine peritoneal macrophages against metastatic variants of the B16 murine melanoma

Transforming growth factor-beta 1 (TGF-beta 1) renders mouse peritoneal macrophages tumoricidal against metastatic variants of the B16 mouse melanoma in vitro. Both direct cytotoxicity and indirect cytotoxicity were observed. A subthreshold concentration (10 U/ml) of recombinant murine interferon-gamma (rMuIFN-gamma) enhanced the direct tumoricidal activity of TGF-beta 1-activated macrophages from 29% to 88% but did not change their indirect tumoricidal profile. Data obtained from macrophages preincubated with either TGF-beta 1 or rMuIFN-gamma showed that TGF-b1 can initiate tumoricidal activity better than rMuIFN-gamma. These effects were plasma-membrane mediated because targeting macrophages with liposomal TGF-beta 1 was ineffective. The order of tumoricidal susceptibility of the B16 melanoma lines to activated macrophages was B16F1 > B16F10 > B16BL6, in inverse order of metastatic potential.     

Role of tumor necrosis factor and interleukin 1 in gamma-interferon-promoted activation of mouse tumoricidal macrophages

The purpose of this study was to determine if recombinant murine interleukin 1 beta (rMu-IL-1 beta) alone or in combination with recombinant murine gamma-interferon (rMu-IFN-gamma) could activate murine macrophages to be tumoricidal against tumor necrosis factor (TNF)-insensitive target cells and to evaluate the possible role of interleukin 1 (IL-1) in murine macrophage activation by recombinant murine tumor necrosis factor (rMu-TNF) plus rMu-IFN-gamma. rMu-IL-1 beta and rMu-TNF alone or in combination could neither directly lyse the TNF-insensitive P815 mastocytoma nor activate resident peritoneal macrophages to be tumoricidal for this target. A synergistic induction of tumoricidal macrophage activity against P815 occurred, however, when either of these monokines was combined with rMu-IFN-gamma. The tumoricidal activity obtained was transitory, and the level of activity was dependent upon the monokine concentration and the length of induction period. Murine macrophages stimulated under the same conditions used to induce tumoricidal activity with rMu-TNF plus rMu-IFN-gamma or with rMu-IL-1 plus rMu-IFN-gamma were shown to produce low concentrations of IL-1 or TNF, respectively. Thus, a bidirectional cross-induction of the production of the two monokines occurred. The monokine production was also quite transitory, and the time of peak production of the monokines (12 h) was found to precede the time of peak tumoricidal activation (24 h). Using neutralizing antisera specific for rMu-IL-1s and rMu-TNF, the cross-induced production of TNF was shown to be required for macrophage tumoricidal activation by rMu-IL-1 beta alone (TNF-sensitive targets) or in combination with rMu-IFN-gamma (TNF-insensitive targets). There was no evidence, however, that the production of IL-1 was required for macrophage activation by rMu-TNF in combination with rMu-IFN-gamma.     

Expression and function of survivin in canine osteosarcoma

Osteosarcoma has a high mortality rate and remains in need of more effective therapeutic approaches. Survivin is an inhibitor of apoptosis family member protein that blocks apoptosis and drives proliferation in human cancer cells where it is commonly elevated. In this study, we illustrate the superiority of a canine osteosarcoma model as a translational tool for evaluating survivin-directed therapies, owing to the striking similarities in gross and microscopic appearance, biologic behavior, gene expression, and signaling pathway alterations. Elevated survivin expression in primary canine osteosarcoma tissue correlated with increased histologic grade and mitotic index and a decreased disease-free interval (DFI). Survivin attenuation in canine osteosarcoma cells inhibited cell-cycle progression, increased apoptosis, mitotic arrest, and chemosensitivity, and cooperated with chemotherapy to significantly improve in vivo tumor control. Our findings illustrate the utility of a canine system to more accurately model human osteosarcoma and strongly suggest that survivin-directed therapies might be highly effective in its treatment.     

Comparison of cytolytic and proliferative activities of human gamma delta and alpha beta T cells from peripheral blood against various human tumor cell lines.

Peripheral blood lymphocytes (PBLs) from healthy donors were more than 95% enriched for gamma delta T cells. V gamma 9/V delta 2 was the predominant T-cell subset and represented more than two thirds of the isolated gamma delta T cells. When activated by surface-immobilized anti-TCR delta 1 monoclonal antibody (MoAb) during 5 days of culture, gamma delta T cells demonstrated a significant fourfold to 15-fold stronger cytolytic activity against various tumor cell lines than did PBL polyclonal alpha beta T cells analogously activated by surface-immobilized anti-CD3 MoAbs. Blocking experiments with specific MoAbs demonstrated that the cytolytic activity of gamma delta T cells was non-major histocompatibility complex (MHC) restricted and did not involve the gamma delta T-cell antigen receptor (TCR) but that cytolytic activity was dependent on LFA-1 beta/ICAM1 interaction. The proliferative responses of gamma delta and alpha beta T cells to Ovcar-3 tumor cells and irradiated allogeneic PBLs were inhibited by anti-HLA-A,B,C MoAb. Our findings suggest that gamma delta T cells activated via the TCR have a significant advantage in non-MHC-restricted lysis of various tumor cell lines over PBL alpha beta T cells stimulated analogously with anti-CD3, which may be important in terms of applicability of activated gamma delta cells for adoptive immunotherapy of metastatic cancers.