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Once prostate cancer metastasizes to bone, conventional chemotherapy is largely ineffective. We hypothesized that inhibition of phosphorylation of the epidermal growth factor receptor (EGF-R) and platelet-derived growth factor receptor (PDGF-R) expressed on tumor cells and tumor-associated endothelial cells, which is associated with tumor progression, in combination with paclitaxel would inhibit experimental prostate cancer bone metastasis and preserve bone structure. We tested this hypothesis in nude mice, using human PC-3MM2 prostate cancer cells. PC-3MM2 cells growing adjacent to bone tissue and endothelial cells within these lesions expressed phosphorylated EGF-R and PDGF-R alpha and -beta on their surfaces. The percentage of positive endothelial cells and the intensity of receptor expression directly correlated with proximity to bone tissue. Oral administration of PKI166 inhibited the phosphorylation of EGF-R but not PDGF-R, whereas oral administration of STI571 inhibited the phosphorylation of PDGF-R but not EGF-R. Combination therapy using oral PKI166 and STI571 with i.p. injections of paclitaxel induced a high level of apoptosis in tumor vascular endothelial cells and tumor cells in parallel with inhibition of tumor growth in the bone, preservation of bone structure, and reduction of lymph node metastasis. Collectively, these data demonstrate that blockade of phosphorylation of EGF-R and PDGF-R coupled with administration of paclitaxel significantly suppresses experimental human prostate cancer bone metastasis.

Objectives: We determined the expression of platelet-derived growth factor (PDGF), PDGF-receptor (PDGF-R), and phosphorylated PDGF-R (p-PDGF-R) on tumor cells and tumor-associated endothelial cells in clinical specimens of human ovarian carcinoma and human ovarian cancer cells growing in culture and in the peritoneal cavity of nude mice., Methods: Ten specimens of high-grade serous ovarian carcinoma were analyzed using immunohistochemistry (IHC). IHC was used to detect ligand and receptor expression in the human ovarian cancer cells from Hey A8 and SKOV3ip1 growing in culture. Cells from these lines were also implanted orthotopically into the peritoneal cavity of nude mice. IHC was used to determine ligand and receptor expression in tumors that formed in the peritoneal cavity., Results: All 10 evaluable samples expressed both PDGF AA and BB on tumor cells. Tumor cells were positive for PDGF-Ralpha in 10/10 samples, PDGF-Rbeta in 8/10 samples, p-PDGF-Ralpha in 6/10 samples, and p-PDGF-Rbeta in 4/10 samples. p-PDGF-Ralpha was positive in 4/10 tumor-associated endothelial cell samples and p-PDGF-Rbeta was positive in 3/10 samples. Human ovarian cancer cells expressed PDGF, PDGF-R, and p-PDGF-R when growing in culture or in the peritoneal cavity of nude mice. PDGF-R and p-PDGF-R were also present on tumor-associated endothelial cells as demonstrated by simultaneous staining with CD31 antibody., Conclusions: PDGF and the corresponding receptors were expressed in autochthonous human ovarian cancer lesions on both tumor cells and tumor-associated endothelial cells. The ligand and receptor were also present on Hey A8 and SKOV3ip1 human ovarian cancer cells growing in vitro and in the peritoneal cavity of nude mice.

Purpose: We sought to determine whether blockade of platelet-derived growth factor receptor (PDGF-R) activation by oral administration of a PDGF-R tyrosine kinase inhibitor (STI571) alone or in combination with i.p. paclitaxel can inhibit the progression of tumors caused by human ovarian carcinoma cells growing in the peritoneal cavity of female nude mice., Experimental Design: In several different experiments, paclitaxel-sensitive and paclitaxel-resistant metastatic human ovarian carcinoma cells were injected into the peritoneal cavity of nude mice. Seven days later, groups (n = 10) of mice began receiving a control treatment, STI571 alone, paclitaxel alone, or a combination of STI571 and paclitaxel. The mice were necropsied after 45 days of treatment., Results: Treatment with combination therapy significantly reduced tumor weight (relative to control or single-agent therapy) in all three human ovarian cancer cell lines. Immunohistochemical analyses revealed that PDGF-R activation was blocked by STI571 administered alone or in combination with paclitaxel. Tumor-associated endothelial cells expressed both PDGF-R and phosphorylated PDGF-R. In mice receiving combination therapy, tumor-associated endothelial cells underwent apoptosis, leading to decreases in microvessel density and tumor cell proliferation relative to control and single-agent therapy., Conclusions: These results show that administration of a PDGF-R tyrosine kinase inhibitor in combination with paclitaxel impairs the progression of ovarian cancer in the peritoneal cavity of nude mice, in part, by blockade of PDGF, an endothelial cell survival factor, which results in the increased apoptosis of tumor-associated endothelial cells.

Purpose: We evaluated the expression of platelet-derived growth factor (PDGF) ligands and receptors in clinical specimens of human pancreatic adenocarcinomas and determined the therapeutic effect of STI571 (Gleevec), a protein tyrosine kinase inhibitor of PDGF receptor (PDGFR), on human pancreatic carcinoma cells growing in the pancreas and liver of nude mice., Experimental Design: Immunohistochemical staining for PDGF-AA and -BB ligands, PDGFR-alpha and -beta, and phosphorylated PDGFR-alpha and -beta was performed on 31 specimens of human pancreatic cancer and L3.6pl human pancreatic adenocarcinoma cell line. To determine the in vivo effects of STI571, nude mice with L3.6pl cells injected into the pancreas were randomized 7 days later to receive one of the following treatments: sterile water p.o. (control), STI571, gemcitabine, or a combination of STI571 and gemcitabine., Results: In 29 of 31 clinical specimens of human pancreatic adenocarcinoma, both tumor cells and tumor-associated endothelial cells expressed phosphorylated PDGFR-alpha and -beta. L3.6pl cells growing in culture expressed moderate amounts of PDGF-AA and little to no PDGFR-alpha or -beta, whereas L3.6pl cells growing in the pancreas of nude mice expressed a high level of PDGF and receptors. Colocalization immunohistochemical analysis demonstrated expression of activated PDGFR-beta by tumor-associated endothelial cells in both the pancreas and in liver metastases. Tumors of mice treated for 4 weeks with STI571 (50 mg/kg or 100 mg/kg p.o. daily) were slightly smaller than controls. Tumors treated with gemcitabine and STI571 (50 mg/kg) were >70% smaller than tumors in control mice and 36% smaller than those in mice treated with gemcitabine only (P < 0.0002 and P < 0.04, respectively). Combination therapy also inhibited spontaneous metastasis to the liver. Tumors from mice treated with both STI571 and gemcitabine had decreased expression of activated (phosphorylated) PDGFR-alpha and -beta, decreased mean vessel density, decreased cell proliferation, and increased apoptosis of tumor cells., Conclusions: Collectively, these data show that activated PDGFR on tumor cells and tumor-endothelial cells can be a novel target for therapy of pancreatic carcinoma.

Purpose: We determined whether chronic administration of IFN-alpha at optimal biological dose inhibits angiogenesis of human pancreatic carcinoma growing in the pancreas of nude mice., Experimental Design: Cells of the human pancreatic cancer cell line L3.6pl were implanted into the pancreas of nude mice. Seven days later, groups of mice received s.c. injection with IFN-alpha alone (50,000 units biweekly or 10,000 units daily), i.p. injection with gemcitabine alone (125 mg/kg biweekly), or injection with both daily IFN-alpha and biweekly gemcitabine for 35 days. In a survival study, the mice were treated until they became moribund., Results: Biweekly treatments with 50,000 units of IFN-alpha alone were ineffective. In contrast, daily injections of IFN-alpha (10,000 units/day) alone, biweekly injections of gemcitabine alone, or the combination of IFN-alpha and gemcitabine reduced tumor volume by 53%, 70%, and 87%, respectively. Immunohistochemical analysis revealed that treatment with IFN-alpha alone or with IFN-alpha plus gemcitabine inhibited expression of the proangiogenic molecules basic fibroblast growth factor and matrix metalloproteinase 9 more than did treatment with gemcitabine alone. These treatments also decreased the staining of proliferating cell nuclear antigen within the tumor and induced apoptosis in tumor-associated mouse endothelial cells (staining with CD31/terminal deoxynucleotidyl transferase-mediated nick end labeling), leading to a decrease in microvessel density., Conclusions: These data show that administration of IFN-alpha at optimal biological dose and schedule in combination with gemcitabine induced apoptosis in tumor-associated endothelial cells and decreased growth of human pancreatic cancer cells in the pancreas, leading to a significant increase in survival.

Background: Expression of platelet-derived growth factor (PDGF) and activation (by autophosphorylation) of its receptor (PDGF-R), a tyrosine kinase, are associated with the growth of metastatic prostate tumor cells in the bone parenchyma. The tyrosine kinase inhibitor STI571 blocks the PDGF signaling pathway by inhibiting PDGF-R autophosphorylation. We examined the effects of STI571, given alone or with paclitaxel (Taxol), on tumor growth in a mouse model of prostate cancer metastasis., Methods: Human prostate cancer PC-3MM2 cells were injected into the tibias of male nude mice. Three days later the mice (20 per group) were randomly assigned to 5 weeks of treatment with oral and injected water (control), daily oral STI571, weekly injected paclitaxel, or STI571 plus paclitaxel. Lesions in bone and the surrounding muscles were then harvested and analyzed by histology, western blotting (for PDGF-R phosphorylation), immunohistochemistry (for expression of proangiogenic molecules), and double immunofluorescence (to identify endothelial cells and apoptotic tumor cells). Growth of bone lesions was monitored by digital radiography. Bone lesions from control mice were used to establish short-term cell cultures for analysis of PDGF-R phosphorylation. All statistical tests were two-sided., Results: PC-3MM2 cells cultured from bone lesions and treated in vitro with STI571 had less phosphorylated PDGF-R than untreated cells. In control mice, bone lesions expressed high levels of PDGF and activated (i.e., phosphorylated) PDGF-R, whereas lesions in the adjacent musculature did not. Activated PDGF-R was present on the surface of endothelial cells within the bone lesions but not in endothelial cells of uninjected bone. Mice treated with STI571 or STI571 plus paclitaxel had a lower tumor incidence, smaller tumors, and less bone lysis and lymph node metastasis than mice treated with water or paclitaxel alone (P<.001 for all). Mice treated with STI571 or STI571 plus paclitaxel had less phosphorylated PDGF-R on tumor cells and tumor-associated endothelial cells, less tumor cell proliferation, statistically significantly more apoptotic tumor cells (all P<.001), and fewer tumor-associated endothelial cells (P<.001) than control mice., Conclusions: Endothelial cells appear to express phosphorylated PDGF-R when they are exposed to tumor cells that express PDGF. Using STI571 to inhibit PDGF-R phosphorylation may, especially in combination with paclitaxel, produce substantial therapeutic effects against prostate cancer bone metastasis.

Purpose: We determined whether blockade of the epidermal growth factor receptor (EGF-R) signaling pathway by oral administration of the EGF-R tyrosine kinase inhibitor (PKI 166) alone or in combination with injectable Taxol inhibits the growth of PC-3MM2 human prostate cancer cells in the bone of nude mice., Experimental Design: Male nude mice implanted with PC-3MM2 cells in the tibia were treated with oral administrations of PKI 166 or PKI 166 plus injectable Taxol beginning 3 days after implantation. The incidence and size of bone tumors and destruction of bone were determined by digitalized radiography. Expression of epidermal growth factor (EGF), EGF-R, and activated EGF-R in tumor cells and tumor-associated endothelial cells was determined by immunohistochemistry., Results: Oral administration of PKI 166 or PKI 166 plus injectable Taxol reduced the incidence and size of bone tumors and destruction of bone. Immunohistochemical analysis revealed that PC-3MM2 cells growing adjacent to the bone expressed high levels of EGF and activated EGF-R, whereas tumor cells in the adjacent musculature did not. Moreover, endothelial cells within the bone tumor lesions, but not in uninvolved bone or tumors in the muscle, expressed high levels of activated EGF-R. Treatment with PKI 166 and more so with PKI 166 plus Taxol significantly inhibited phosphorylation of EGF-R on tumor and endothelial cells and induced significant apoptosis and endothelial cells within tumor lesions., Conclusions: These data indicate that endothelial cells exposed to EGF produced by tumor cells express activated EGF-R and that targeting EGF-R can produce significant therapeutic effects against prostate cancer bone metastasis.

We determined whether blockade of the epidermal growth factor-receptor (EGF-R) signaling pathway by oral administration of the EGF-R tyrosine kinase inhibitor PKI166 can inhibit angiogenesis and growth of SN12PM6 human renal cell carcinoma (HRCC) in the kidney of nude mice and whether gemcitabine can potentiate these effects. In vitro treatment of HRCC cells with PKI166 inhibited EGF-R autophosphorylation, which correlated with a decrease in expression of Bcl-xl protein and phosphorylation of signal transducers and activators of transcription, particularly signal transducers and activators of transcription 3. PKI166 also decreased expression of vascular endothelial growth factor and basic fibroblast growth factor in a dose-dependent manner. Oral administration of PKI166 or PKI166 and injected gemcitabine or gemcitabine alone beginning 7 days after implantation of SN12PM6 cells into the kidney of athymic nude mice reduced the volume of tumors by 26, 61, and 23%, respectively. In another experiment 28 days after the orthotopic implantation of SN12PM6 cells, nephrectomy was performed followed by 4 weeks of treatment. Treatment with PKI166 and, more so, PKI166 plus gemcitabine significantly inhibited lung metastasis, corresponding to a significant increase in overall length of survival. EGF-R activation was significantly blocked by therapy with PKI166 and was associated with a significant reduction in expression of vascular endothelial growth factor and interleukin-8, decreased microvessel density, decreased staining of proliferating cell nuclear antigen, and increased tumor cell apoptosis. Collectively, the data indicate that targeting activation of EGF-R on HRCC produces significant therapeutic benefits.

We evaluated whether treatment of orthotopic human prostate cancer in nude mice with pegylated IFN-alpha-2b (PEG-IFN-alpha-2b) and docetaxel could represent a two-compartment targeting of primary tumor (tumor cells and tumor-associated endothelial cells) and inhibition of regional lymph node metastasis. The antiangiogenic properties of IFN were combined with the cytotoxic properties of docetaxel, resulting in apoptosis of both tumor cells and endothelium and hence significant inhibition of primary tumor growth. We first determined the optimal biological dose of PEG-IFN-alpha-2b (70,000 IU/week) necessary to down-regulate the expression of basic fibroblast growth factor, matrix metalloprotease-9, and matrix metalloprotease-2. The therapeutic dose of docetaxel (10 mg/kg/week) was determined by efficacy and minimal body weight loss. Therapy beginning 3 days after orthotopic implantation of PC3-MM2 prostate cancer cells reduced tumor weight by 37% in mice treated with PEG-IFN-alpha-2b, by 60% in mice treated with docetaxel, and by 83% in those given both drugs. PEG-IFN-alpha-2b also induced apoptosis of tumor-associated endothelial cells and hence a significant decrease in microvessel density. Our data indicate that the combination of PEG-IFN-alpha and docetaxel inhibits neoplastic angiogenesis by inducing a decrease in the local production of proangiogenic molecules by tumor cells, resulting in increased apoptosis of tumor-associated endothelial cells.

Background: Overexpression of epidermal growth factor receptor (EGF-R) is associated with increased malignant potential and correlates with poor clinical outcome in head and neck cancer. Therefore, inhibition of the EGF-R pathway provides an ideal target for molecular therapy. We examined in vitro and in vivo effects of PKI166, an orally administered EGF-R inhibitor, on 2 human squamous cell carcinoma of the oral cavity cell lines, Tu159 and MDA1986., Study Design: Basic science, laboratory investigation., Results: For Western blotting, Tu159 and MDA1986 cells were pretreated for 1 hour and then stimulated with EGF. The EGF-R-specific tyrosine kinase autophosphorylation was inhibited completely by PKI166 at all doses tested (1-10 micro g/mL). By means of a tetrazolium-based viable cell assay, PKI166 was shown to arrest the growth of Tu159 and MDA1986 cells. The inhibitory concentration (50%), calculated from regression lines on the linear portion of the growth inhibition graphs, was 0.18 micro M (R = 0.98) for Tu159 cells and 0.23 micro M (R = 0.97) for MDA1986 cells. Nude mice were inoculated subcutaneously with 1 x 10(6) Tu159 tumor cells and observed for 7 days. Next, daily doses of PKI166 (0, 10, or 50 mg/kg) were delivered by orogastric lavage for 28 days and the animals were observed for tumor growth. PKI166 significantly reduced tumor growth in mice treated for 1 month with oral PKI166 in a dose-dependent fashion., Conclusions: Targeted molecular therapy with EGF-R blockade arrests the growth of oral cancer in vitro and reduces its proliferation in an experimental xenograft animal model.

The purpose of this study was to optimize the antitumor andantiangiogenic activities of pegylated IFN-alpha (PEG-IFN-alpha)alone or in combination with paclitaxel against SKOV3ip1 human ovarian cancer cells growing orthotopically in female nude mice. Seven days after the i.p. implantation of tumor cells, groups of mice (n = 10) were injected s.c. once per week (for 4 weeks) with different doses of PEG-IFN-alpha (3,500, 7,000, 35,000, and 350,000 units). PEG-IFN-alpha at 7,000 units significantly decreased tumor incidence and volume. At doses exceeding 7,000 units, PEG-IFN-alpha was less efficacious. In another set of studies conducted 7 days after the i.p. implantation of SKOV3ip1 cells, groups of mice (n = 10) received (once per week for 4 weeks) either s.c. administrations of PEG-IFN-alpha (7,000 units), i.p. injections of paclitaxel (100 microg/wk), or a combination of PEG-IFN-alpha and paclitaxel. The mice were killed 7 days after the last treatment, and tumor burden was assessed. Administration of PEG-IFN-alpha at the optimal biological dose (7,000 units) in combination with paclitaxel significantly decreased angiogenesis and progressive growth of human ovarian carcinoma cells in a synergistic fashion. The combination therapy produced the most significant inhibition in expression of the proangiogenic molecules basic fibroblast growth factor and matrix metalloproteinase-9. Decreased microvessel density, decreased proliferating cell nuclear antigen staining, and increased endothelial cell apoptosis also correlated with therapeutic success. Collectively, the data suggest that combining the optimal biological dose of PEG-IFN-alpha with paclitaxel may provide a novel and effective approach to the treatment of human ovarian carcinoma.

Since vascular endothelial growth factor (VEGF) plays a major role in tumor angiogenesis, we determined whether blockage of VEGF receptor signaling using a novel tyrosine kinase inhibitor (PTK 787) decreases the growth and metastasis of human pancreatic carcinoma growing orthotopically in nude mice. Human pancreatic L3.6pl cells were injected into the pancreas of nude mice. Seven days later, groups of mice were given daily oral administrations of PTK 787 alone, twice weekly i.p. injections of gemcitabine, or combination therapy. The mice were necropsied when control mice became moribund (day 35). Therapy with PTK 787 alone, gemcitabine alone, or the combination of both agents produced respectively 60%, 70%, and 81% inhibition in the volume of pancreatic cancers. The combination therapy significantly decreased the incidence of lymph node and liver metastasis, leading to a significant increase in survival. Microvessel density (MVD) was significantly decreased in tumors treated with either PTK 787 alone or PTK 787 plus gemcitabine. MVD directly correlated with tumor cell proliferation and inversely correlated with apoptosis of tumor cells and associated endothelial cells. Collectively, our results demonstrate that blockade of VEGF-R signaling may provide an additional approach to the therapy of pancreatic cancer.

We determined the optimal administration schedule of a novel epidermal growth factor receptor (EGFR) protein tyrosine kinase inhibitor (PKI), PKI 166 (4-(R)-phenethylamino-6-(hydroxyl)phenyl-7H-pyrrolo[2.3-d]-pyrimidine), alone or in combination with gemcitabine (administered i.p.) for therapy of L3.6pl human pancreatic carcinoma growing in the pancreas of nude mice. Seven days after orthotopic implantation of L3.6pl cells, the mice received daily oral doses of PKI 166. PKI 166 therapy significantly inhibited phosphorylation of the EGFR without affecting EGFR expression. EGFR phosphorylation was restored 72 h after cessation of therapy. Seven days after orthotopic injection of L3.6pl cells, groups of mice received daily or thrice weekly oral doses of PKI 166 alone or in combination with gemcitabine. Treatment with PKI 166 (daily), PKI 166 (3 times/week), or gemcitabine alone produced a 72%, 69%, or 70% reduction in the volume of pancreatic tumors in mice, respectively. Daily oral PKI 166 or thrice weekly oral PKI 166 in combination with injected gemcitabine produced 97% and 95% decreases in volume of pancreatic cancers and significant inhibition of lymph node and liver metastasis. Daily oral PKI 166 produced a 20% decrease in body weight, whereas treatment 3 times/week did not. Decreased microvessel density, decreased proliferating cell nuclear antigen staining, and increased tumor cell and endothelial cell apoptosis correlated with therapeutic success. Collectively, our results demonstrate that three weekly oral administrations of an EGFR tyrosine kinase inhibitor in combination with gemcitabine are sufficient to significantly inhibit primary and metastatic human pancreatic carcinoma.

We determined whether the expression of matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP) in murine macrophages is regulated by the novel synthetic bacterial lipopeptide JBT 3002. Multilamellar liposomes (MLV) encapsulating JBT 3002 (MLV-JBT 3002) stimulated the production of 72-kDa and 92-kDa (gelatinase A and B) type IV collagenase and inhibited the production of murine metalloelastase (MME) in a dose-dependent manner in murine peritoneal macrophages. MLV-JBT 3002 also induced production of TIMP-1. MLV-JBT 3002 did not induce collagenase production in tumor cells. Priming murine macrophages with interferon-gamma (IFN-gamma) inhibited JBT 3002-stimulated production of both MMP-9 and MMP-2 and further inhibited production of MME by a mechanism involving nitric oxide (NO). This conclusion is based on data showing that IFN-gamma failed to inhibit production of MMP in the presence of L-methyl arginine or in macrophages from inducible nitric oxide synthase knockout mice. These data suggest that JBT 3002 differentially regulates the production of various MMPs and TIMP in macrophages.

The authors recently reported that tumoricidal activation of macrophages by a new synthetic bacterial lipopeptide, JBT 3002, can augment chemotherapy-mediated tumor-cell killing. The aim of this study was to identify the mechanism responsible for the destruction of metastatic cells. Three daily oral doses of JBT 3002 before once-weekly intraperitoneal injections of 100 mg/kg irinotecan for 3 weeks significantly increased the eradication of established CT-26 murine colon cancer liver metastases compared with treatment with irinotecan alone. Immunohistochemical analyses revealed that the hepatic metastases in mice given combination therapy contained infiltrating CD8+ lymphocytes and a dense infiltrate of macrophages expressing both inducible nitric oxide synthase (iNOS) and interleukin-15. In vitro treatment of peritoneal macrophages with JBT 3002 plus interferon-gamma induced the expression of iNOS and the production of nitric oxide. In the presence of a low (subtoxic) dose of irinotecan, these activated macrophages produced significant lysis of CT-26 cells. The high level of cytotoxicity was inhibited by the specific inducible nitric oxide synthase inhibitor, NG-methyl-L-arginine. In contrast, irinotecan-mediated lysis of normal intestinal epithelial IEC-6 cells was not increased by activated macrophages. Scanning electron microscopy revealed that activated macrophages bound to CT-26 tumor cells but not to normal IEC-6 cells, confirming that nitric oxide-mediated cytotoxicity is specific for tumor cells. Collectively, the results suggest that augmentation of the therapeutic efficacy of irinotecan against colon cancer liver metastases by immunomodulation with JBT 3002 may be associated with elevated inducible nitric oxide synthase and endogenous interleukin-15 in tumor-infiltrating macrophages.

Malignant pleural effusion (PE) is associated with advanced human lung cancer. We found recently, using a nude mouse model, that vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) is responsible for PE induced by non-small cell human lung carcinoma cells. The purpose of this study was to determine the therapeutic potential of a VEGF/VPF receptor tyrosine kinase phosphorylation inhibitor, PTK 787, against PE formed by human lung adenocarcinoma (PC14PE6) cells. PTK 787 did not affect the in vitro proliferation of PC14PE6 cells, whereas it specifically inhibited proliferation of human dermal microvascular endothelial cells stimulated by VEGF/VPF. A specific platelet-derived growth factor receptor tyrosine kinase inhibitor, CGP57148 (used as a control because PTK 787 also inhibits platelet-derived growth factor receptor tyrosine kinases), had no effect on proliferation of PC14PE6 or human dermal microvascular endothelial cells. i.v. injection of PC14PE6 cells into nude mice produced lung lesions and a large volume of PE containing a high level of VEGF/VPF. Oral treatment with CGP57148 had no effect on PE or lung metastasis. In contrast, oral treatment with PTK 787 significantly reduced the formation of PE but not the number of lung lesions. Furthermore, treatment with PTK 787 significantly suppressed vascular hyperpermeability of PE-bearing mice but did not affect the VEGF/VPF level in PE or expression of VEGF/VPF protein and mRNA in the lung tumors of PC14PE6 cells in vivo. These findings indicate that PTK 787 reduced PE formation mainly by inhibiting vascular permeability, suggesting that this VEGF/VPF receptor tyrosine kinase inhibitor could be useful for the control of malignant PE.

We determined whether inhibition of the catalytic tyrosine kinase activity of the receptors for vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) inhibits the formation of malignant ascites and the progressive growth of human ovarian carcinoma cells implanted into the peritoneal cavity of nude mice. The novel protein tyrosine inhibitor PTK 787 was evaluated in two models of human ovarian cancer: Hey-A8 cells, which express low levels of VEGF/VPF and grow as solid tumor foci on the surface of peritoneal organs, and SKOV3 i.p.1 cells, which express high levels of VEGF/VPF and grow as solid peritoneal tumors and ascites. Treatment of nude mice by daily oral administration of 50 mg/kg PTK 787 was not effective against Hey-A8 tumors. In sharp contrast, it significantly inhibited growth of SKOV3 i.p.1 cells and formation of ascites, significantly increasing survival of mice with the implants. Tumor-induced vascular hyperpermeability in the peritoneum of tumor-bearing mice was inhibited by PTK 787, which accounted for its inhibition of ascites formation. Our results suggest that blockade of the VEGF/VPF receptor may be an efficient strategy to inhibit formation of malignant ascites and growth of VEGF/VPF-dependent human ovarian carcinomas.

We determined the therapeutic effect of irinotecan (CPT-11) combined with the immunomodulator JBT 3002, a synthetic bacterial lipopeptide (N-acylated derivative of psi-amino-C1-C3-alkane-sulfonic acid), against highly metastatic human pancreatic carcinoma cells injected into the pancreas of athymic nude mice. Mice received four courses consisting of three daily oral doses of JBT 3002, followed by once weekly i.p. injection of CPT-11. Control mice were treated with CPT-11 alone, JBT 3002 alone, or saline. Tumor growth and metastasis were assessed by gross pathology and confirmed by histological examination. Treatment with CPT-11 alone significantly decreased the median volume of pancreatic tumors and the incidence of metastasis, whereas treatment with only JBT 3002 did not. The combination therapy of CPT-11 plus JBT 3002 decreased tumor volume and incidence of metastasis significantly more than CPT-11 alone. The number of apoptotic cells (terminal deoxynucleotidyl transferase-mediated nick end labeling assay), the number of scavenger-receptor-positive macrophages, and expression level of inducible nitric oxide synthase (iNOS) within lesions directly correlated with therapeutic effects. Indeed, the in vitro incubation of tumor cells with macrophages activated by JBT 3002 plus IFN-gamma produced a significant lysis of tumor cells that could be blocked by a specific inhibitor of iNOS. Collectively, these data demonstrate that the oral administration of the immunomodulator JBT 3002 combined with i.p. injection of CPT-11 can decrease the growth of human pancreatic carcinoma and the incidence of metastasis in nude mice by both a direct antitumor effect and the activation of iNOS in infiltrating macrophages.

We recently reported that p.o. administration of the new synthetic bacterial lipopeptide JBT-3002 can protect mice from irinotecan (CPT-11)-induced intestinal injury, but the mechanism was not known. Because interleukin-15 (IL-15) is associated with maintenance of intestinal epithelial cell integrity, we examined whether p.o. administration of JBT-3002 elevates expression of this monocyte-derived cytokine. Four daily i.p. injections of 100 mg/kg CPT-11 were effective against liver metastases produced by CT-26 murine colon cancer cells, but severe damage to the intestinal epithelium and early death of the mice also resulted. Three consecutive daily p.o. doses of JBT-3002 prior to i.p. injection of irinotecan prevented the undesirable side effects of irinotecan without reducing its ability to eradicate liver metastases. Immunohistochemical analyses of the intestines of mice treated with JBT-3002 and CPT-11 demonstrated an increase in the number of dividing cells in the crypts and enhanced expression of IL-15 in lamina propria cells; the increase correlated with increased expression of the IL-15 gene as determined by semiquantitative reverse transcriptase-PCR. In vitro studies demonstrated that JBT-3002 induced expression of IL-15 in peritoneal macrophages but not in normal intestinal epithelial cells (IEC-6). Moreover, the presence of IL-15 decreased irinotecan-mediated cytotoxicity of IEC-6 epithelial cells. These data show that the p.o. administration of JBT-3002 induces expression of IL-15 by macrophages in the lamina propria, which can prevent irinotecan-induced injury to the intestinal mucosa.

We determined whether the angiogenesis and growth of murine colon carcinomas growing in the wall of the cecum is dependent on infiltrating leukocytes. Syngeneic BALB/c or SCID mice were treated with a myelosuppressive, maximally tolerated dose of doxorubicin. Parental or multidrug resistant CT-26 colon carcinoma cells were implanted into the cecal wall 3 days after the second intravenous injection of doxorubicin. Control mice developed large, well-vascularized tumors, whereas doxorubicin-pretreated mice did not. Intravenous injection of spleen cells from normal BALB/c or SCID mice one day prior to tumor cell implantation reversed the decreased vascularity and tumorigenicity. The production of proangiogenic molecules and microvessel density in tumors directly correlated with the number of infiltrating leukocytes, suggesting that tumor-infiltrating leukocytes are essential to angiogenesis of murine colon carcinomas.

Beta-2-glycoprotein I (beta2GPI), a 50-kDA serum glycoprotein that binds negatively charged phospholipids plays a role in coagulation, thrombosis, and the clearance of phosphatidylserine expressing cells. Because of its recently recognized role in several autoimmune responses, we have developed a method that quantifies plasma beta2GPI levels by using a competitive ELISA assay. When combined with data from a standard ELISA, this method determines the concentration of free beta2GPI and the fraction of antibody-bound beta2GPI thereby facilitating quantification of total antigen in individuals with autoimmune antibodies. Standard competitive inhibition ELISA was compared with this method, which uses known amounts of standard beta2GPI added to the plasma as an internal standard. Identical results were obtained with both methods for plasma samples from normal individuals that did not contain blocking antibodies. Analysis of plasma from antiphospholipid syndrome patients (patients with autoantibodies to beta2GPI) by the internal standard method, however, resulted in significantly lower apparent beta2GPI levels indicating that a substantial fraction of the plasma beta2GPI was bound by antibody.

We studied activation to the tumoricidal state of murine peritoneal macrophages by liposomes containing a new synthetic analogue, JBT3002, of a lipoprotein from the outer wall of a gram-negative bacterium. The liposomes containing JBT3002 or CGP31362 were superior to liposomes containing muramyl tripeptide phosphatidylethanolamine (MTP-PE) for tumoricidal activation in three ways. First, efficient macrophage activation required lower concentrations of JBT3002 or CGP31362 than MTP-PE. Second, macrophage activation by JBT3002 was less dependent on priming by interferon-gamma. Third, MLV-JBT3002 activated tumoricidal properties in both lipopolysaccharide (LPS)-responsive and LPS-nonresponsive macrophages. The activation of tumoricidal properties by MLV-JBP3002 depended on protein tyrosine kinase (PTK) activity associated with phosphorylation of tyrosine. The major mechanism for tumoricidal activity in macrophages incubated with MLV-JBT3002 was due to increased activity of inducible nitric oxide synthase (iNOS) and, hence, production of nitric oxide (NO). We base this conclusion on the results of several experiments. First, MLV-JBT3002 was not directly toxic to tumor target cells. Second, the specific iNOS inhibitor NG-monomethyl-L-arginine abrogated tumor cell lysis by MLV-JBT3002-treated macrophages. Third, macrophages from iNOS knockout mice did not lyse tumor cells, even after incubation with high concentrations of MLV-JBT3002. These data suggest that liposomes containing the synthetic bacterial lipopeptide JBT3002 are potent activators of macrophage tumoricidal properties.

The induction of severe diarrhea limits the usefulness of the DNA topoisomerase I inhibitor irinotecan (CPT-11) in the treatment of advanced colon cancer. We investigated whether oral administration of the new synthetic bacterial lipopeptide, JBT 3002, encapsulated in phospholipid liposomes could prevent damage to the intestinal epithelium and lamina propria and thus allow for the parenteral administration of high-dose irinotecan to mice with established syngeneic CT-26 colon cancer liver metastases. Treatment of mice with four daily i.p. injections of 100 mg/kg irinotecan was effective against liver metastases but also resulted in loss of body weight and early death. Histopathological examination of the intestines after this treatment revealed loss of villi, epithelial vacuolation, decrease in the number of cells in the crypts in S-phase, increase in the number of apoptotic cells, and reduction in the number of lymphocytes in the lamina propria. In contrast, treatment of mice with the same irinotecan regimen after oral administration of JBT 3002 produced highly significant inhibition of liver metastases without detectable damage to the intestines. Studies that used irinotecan administered once a week for 3 weeks after pretreatment with oral JBT 3002 demonstrated significantly intensified eradication of established CT-26 liver metastases compared with treatment with once-weekly irinotecan alone. Histological studies revealed that the liver metastases in mice treated with oral JBT 3002 and i.p. irinotecan contained a higher number of macrophages than metastases in mice treated with either drug alone. In vitro studies revealed that irinotecan produced direct antiproliferative effects but JBT 3002 did not. Tumor cells exposed to both irinotecan and macrophages activated by JBT 3002 were highly susceptible to lysis. These data show that oral administration of JBT 3002 can prevent irinotecan-induced gastrointestinal toxic effects and maintain the integrity of the lamina propria, thus allowing for intensification of irinotecan therapy against liver metastases from colon cancer.

The therapy of cancer requires strategies that can eradicate metastatic disease. Metastases consist of unique subpopulations of tumor cells that are able to colonize distant organs and become autonomous from homeostatic mechanisms. Conventional therapies generally have been unsuccessful due to biological heterogeneity in metastatic tumors. It is possible to circumvent this heterogeneity by the tumoricidal activation of tissue macrophages. Activation can be achieved by encapsulation of immunomodulators, e.g., muramyl tripeptide analogues, into liposomes, and this form of immunomodulation leads to eradication of established tumor metastases in numerous animal tumor models. Modulation of the tumor microenvironment by activated macrophages may prove to be an additional modality in therapy that combines the use of biological response modifiers with conventional therapies.

We investigated the expression of cytokine genes and tumoricidal properties in human blood monocytes in response to a new synthetic immunomodulating lipopeptide, JBT3002. Incubation of peripheral blood monocytes with free-form JBT3002 or JBT3002 encapsulated in multilamellar phospholipid vesicles (liposomes, MLV-JBT3002) induced tumoricidal properties in a dose-dependent manner. Both MLV-JBT3002 and free-form JBT3002 induced production of tumor necrosis factor alpha, interleukin-1beta, and interleukin-6 in a dose-dependent manner with similar kinetics. Treatment of monocytes with interferon-gamma did not significantly alter the expression of cytokine genes but increased the expression of cytokines induced by MLV-JBT3002 and free-form JBT3002. In contrast to monocyte activation by lipopolysaccharide (LPS), activation by JBT3002 was independent of serum and was not inhibited by CD14-neutralizing antibody. Incubation of monocytes with JBT3002 induced a rapid increase in tyrosine phosphorylation of proteins with apparent molecular masses of 42 and 38 kDa, a migration band shift of c-Jun NH2-terminal kinase 1 (JNK1), and activation of extracellular signaling regulated kinases. Consistent with its effect on cytokine expression, stimulation of these intracellular signaling pathways by JBT3002 was not inhibited in serum-free conditions. Collectively, the data indicate that the synthetic lipopeptide JBT3002 is a potent monocyte activator that modulates monocyte function by mechanisms similar to LPS but by a distinct receptor.

Although humoral responses to Borrelia burgdorferi (Bb) have been shown to be protective in some animal models of Lyme disease, the role of T cells in this disease is less well understood. This work describes three Bb-specific T cell lines that prevent disease progression in syngeneic mice. The T cell lines were generated in C3H mice immunized with Bb in complete Freund's adjuvant. All lines were Bb-specific, CD4+, TCRalphabeta+, and they proliferated and produced interferon-gamma and interleukin-2 on stimulation with Bb. Injection of the cell lines into naive C3H recipients significantly reduced the number of organisms recoverable from the blood and tissues of infected mice and protected them from developing Bb-induced periarthritis. These studies demonstrated that Th1 cells can confer resistance to Bb infection in susceptible mice and suggested that the timing of this T cell response may be critical for determining disease outcome.

Rapid evaluation of new cytotoxic agents and biological response modifiers for therapy of cancer and elucidation of their mechanisms of action require the use of relevant animal models. It is well established that the faithful reproduction of the tumor microenvironment that allows the emergence of subpopulations of tumor cells with the biological and metastatic properties observed in clinical cancer occurs with orthotopic tumor models (transplantable and transgenic). This review summarizes the evidence that phenotypic properties of metastatic cells are governed by the expression of genes that are regulated by interaction with the relevant organ environment. While ectopic models of cancer allow rapid screening of new compounds and transgenic models afford opportunities to study early cellular and molecular events in tumor progression and metastasis, orthotopic transplantation of tumor cells remains an affordable, reproducible and reliable methodology for the study of organ-specific determinants of the biology and therapy of cancer.

The present study was undertaken to investigate the effect of JT3002, a new synthetic analogue of a lipoprotein from the outer wall of a gram-negative bacterium on the production of cytokines by mouse peritoneal macrophages. Multilamellar liposomes containing different concentrations of JT3002 induced production of the inflammatory cytokines tumor necrosis factor-alpha, interleukin-1 alpha, and interleukin-6 by macrophages in dose- and time-dependent manners. The presence of interferon-gamma enhanced production of tumor necrosis factor-alpha by macrophages exposed to lower concentrations of JT3002 and induced the release of nitric oxide, a potent cytolytic molecule of activated macrophages. Unlike lipopolysaccharide, JT3002 activated macrophages independently of serum, but like lipopolysaccharide, it required protein tyrosine kinase.

The systemic administration of doxorubicin (DXR) decreases the number of epithelial cells and leukocytes in the small intestine of mice. Oral administration of muramyl tripeptide phosphatidylethanolamine (MTP-PE) prevented both disruption of intestinal architecture, and a decrease in the number of macrophages, and it induced the expression of IL-6, G-CSF, GM-CSF, and TNF-alpha in the intestinal tissue. The data suggest that the oral administration of MTP-PE can prevent chemotherapy-induced toxicity to the intestinal mucosa and hence infections due to translocation of aerobic bacteria from the intestine to the blood.

The purpose of this study was to determine whether the implantation of human prostate cancer cells into the prostates of nude mice and their subsequent growth there can be used to select variants with increasing metastatic potential. PC-3M and LNCaP cells were injected into the prostates of athymic mice. Tumors from the prostate or lymph nodes were harvested, and cells were reinjected into the prostate. This cycle was repeated three to five times to yield cell lines PC-3M-Pro4, PC-3M-LN4, LNCaP-Pro3-5, and LNCaP-LN3-4. Parental and variant cells were injected into the prostates of nude mice. PC-3M-LN4 cells produced enhanced regional lymph node and distant organ metastasis as compared to PC-3M-Pro4 or PC-3M cells. After i.v. or intracardiac inoculation, PC-3M-LN4 cells produced a higher incidence of lung metastasis and bone metastasis, respectively, than PC-3M or PC-3M-Pro4 cells. Subsequent to implantation into the prostate, LNCaP-LN3 cells produced a higher incidence of regional lymph node metastases than LNCaP-Pro5 or LNCaP cells. After intrasplenic implantation, LNCaP-LN3 cells also yielded experimental liver metastases. The metastatic LNCaP-LN3 cells exhibited clonal karyotypic abnormalities, were less sensitive to androgen (in vitro and in vivo), and produced high levels of prostate-specific antigen. Collectively, the data show that the orthotopic implantation of human prostate cancer cell lines in nude mice is a relevant model with which to study the biology of prostate cancer metastasis and to select variant cell lines with enhanced metastatic potential.

We evaluated the therapeutic efficacy against murine drug-sensitive and drug-resistant tumor of a combination chemotherapy regimen comprising intravenous administration of doxorubicin (DXR) plus oral administration of the staurosporine analogue CGP 41251 (benzoylstaurosporine), a highly specific inhibitor of protein kinase C (PKC). In vitro studies indicated that the simultaneous presence of noncytotoxic concentrations of CGP 41251 with DXR decreased the median inhibitory concentration (IC50) about 3-fold in the drug-sensitive parental murine cell lines, CT-26P and UV2237. Similar treatment of drug-resistant variants of these tumor cell lines reversed their multiple drug resistant (MDR) phenotype (about a 5-fold increase in their sensitivity to DXR) and increased the cellular accumulation of DXR. Combination therapy in vivo with DXR and CGP 41251 significantly inhibited the SC growth of the drug-resistant CT-26R500 cell line. This effect was confirmed by the ability of this combination therapy to reduce the number of lung metastases produced by IV injection of either the drug-sensitive parental line CT-26P or the drug-resistant subline, CT-26R500. PKC activity was reduced in tumors derived from mice treated with either DXR or CGP 41251, but not from those derived from mice treated with the combination. These results reflect one of the infrequent examples of being able to modulate the sensitivity of in vivo-grown tumors to the antitumor effects of an MDR-related drug and suggest a basis for evaluation of CGP 41251 in clinical trials.

The present study evaluated the in vivo biological activity of synthetic muramyl tripeptide, CGP 19835A, when encapsulated into phosphatidylcholine liposomes (POPC-19835A) and administered as an p.o. immunomodulator to BALB/c mice. Liposomes were rapidly absorbed in the intestine and reached the systemic circulation within 4 h. Alveolar macrophages harvested from the lungs of mice 24 h after a single p.o. feeding of POPC-19835A were tumoricidal toward syngeneic murine renal cell carcinoma target cells. Repeated daily feedings with POPC-19835A generated sustained activation of the alveolar macrophages. Activation of peritoneal macrophages to the tumoricidal state required at least three daily feedings of POPC-19835A. In vitro studies demonstrated the release of tumor necrosis factor alpha and interleukin 6 by macrophages activated by POPC-19835A in the presence of gamma-interferon. Interleukin 1 and nitric oxide were not induced in macrophages by this liposomal preparation. Daily administration of POPC-19835A after i.v. injection of renal cell carcinoma tumor in BALB/c mice inhibited the development of experimental lung metastasis and confirmed the potential role of long-term therapy with this new p.o. immunomodulator.

A direct comparison was made between the insoluble ELISPOT, solubilized ELISPOT, and ELISA assays, to detect cytokine secretion by cells, using sterile ELISA plates and commercially available monoclonal antibodies. We evaluated the IL-6 secretion by resident peritoneal macrophages of BALB/c mice and the secretion of IL-2, IL-4, IL-5, and IL-6 by the murine T helper clone, D10.G4.1 cells. Our results demonstrated that ELISPOT can detect cytokine secretion at the single cell level in either adherent or nonadherent cells. The level of detection by ELISPOT was 10 to 200 times more sensitive than ELISA performed on culture supernatants. We also demonstrated that the solubilized ELISPOT can detect cytokine secretion by cells with greater sensitivity than conventional ELISA. These ELISPOT assays can be used to characterize the cytokine secretion pattern of different cell populations in a simple, reproducible, and reliable manner.

The antiproliferative effect of interferon alpha (IFN-alpha) against cultured 253J human bladder tumour cells was enhanced when IFN-alpha was encapsulated into multilamellar phospholipid liposomes (MLV). Moreover, significant cytostasis of a variant 253J subline (253J alpha R, resistant to the antiproliferative effect of IFN-alpha), could be achieved by delivery of IFN-alpha contained in liposomes. Although the two cell lines have the same number and affinity of cell receptors for IFN-alpha, the 253J alpha R cells did not down-regulate receptors as observed for the IFN-sensitive 253J cells. The IFN-response genes, 2'-5' oligosynthetase and gene 6-16 were equally induced in both cell lines following incubation of the cells with either free IFN-alpha or liposome-encapsulated IFN-alpha. Incorporation of radiolabelled IFN-alpha into cells by liposomes was independent of the status of IFN-receptors (the receptors being either occupied or down-regulated). These observations are consistent with the hypothesis that the antiproliferative effects of IFN-alpha against 253J and 253J alpha R cells may be mediated by internalization of IFN-alpha.

The therapy of cancer is, in reality, the design of therapeutic strategies for therapy of metastatic disease. Metastases consist of unique subpopulations of tumor cells that are derived from the primary tumor, colonize distant target organs, and are able to subvert host immune responses, establish necessary angiogenesis, and obtain a sufficient nutrient supply while evolving to become autonomous from homeostatic mechanisms that function within normal, differentiated tissues. Attempts at eradication of metastases by conventional therapies have generally been unsuccessful due to genetic instability and heterogeneity of metastatic tumors; these properties lead to the emergence of tumor cells that are resistant to most conventional treatments. It may be possible to circumvent this heterogeneity by the activation of tissue macrophages to the tumoricidal state. Activated macrophages are able to kill tumor cells while sparing normal tissues, and efficient activation can be achieved by encapsulation of synthetic muramyl tripeptide analogues into multilamellar vesicles composed of phospholipids. Systemic administration of these liposome-encapsulated compounds leads to tumoricidal activation of alveolar and peritoneal macrophages and eradication of established tumor metastasis in numerous animal tumor models, and this form of therapy is enhanced by combination with parenteral administration of cytokines. Phase III clinical trials of recurrent osteosarcoma are currently in progress. Modulation of the tumor microenvironment by activated macrophages may prove to be an additional modality in treatment strategies that combine the use of biological response modifiers with conventional therapies.

Subsequent to systemic administration of doxorubicin or whole-body X-irradiation, C57BL/6 mice exhibit a depletion in lymphoid cells (macrophages) lasting 2-3 weeks and returning to normal by 4 weeks after either treatment. We evaluated the ability of repeated oral administration of the synthetic macrophage activator muramyl tripeptide phosphatidylethanolamine (MTP-PE), either in free form or encapsulated into multilamellar liposomes, to reverse or prevent the decline in macrophages after cytoreductive therapies. The number of both resident peritoneal macrophages and peritoneal exudate cells elicited by thioglycollate-induced inflammation increased after the oral administration of MTP-PE (three times a week) for at least 3 weeks. The depletion of macrophage number from the peritoneal cavity that occurred after two IV injections of doxorubicin or X-irradiation with 1.5 or 3.0 Gy was prevented by repeated oral feedings of MTP-PE. Moreover pretreatment of mice with oral MTP-PE prevented depletion of macrophages resulting from IV injections of doxorubicin. Modest protection was also noted for blood leukocytes in mice receiving oral MTP-PE following systemic DXR. Similar effects were achieved when MTP-PE was encapsulated into phospholipid liposomes: this formulation also allowed macrophages to be readily activated to the tumoricidal state. The oral administration of MTP-PE offers an additional strategy for protection of host defense cells during cytoablative therapies.

Alterations in the immunogenic properties of tumor cells frequently accompany selection for multiple-drug-resistant (MDR) variants. Therefore, studies were performed to examine the hypothesis that overexpression of membrane P-glycoprotein, commonly observed in MDR tumor cells, is associated with enhanced immunogenic properties. Immunogenicity was determined by (a) the ability of drug-sensitive parental UV2237M fibrosarcoma cells and drug-resistant UV2237M variant cells to immunize normal mice against rechallenge with parental tumor cells and (b) the ability of normal syngeneic mice to reject cell inocula that caused progressive tumor growth in immunocompromised mice. Variant UV2237M cell lines included subpopulations selected for a six- to ten-fold increase in mRNA for P-glycoprotein and expression of the MDR phenotype (resistance to doxorubicin) and cells sensitive to doxorubicin (and no expression of MDR properties) but resistant to ouabain. All UV2237M drug-resistant cells were highly immunogenic in immunocompetent mice, regardless of their MDR phenotype. Additional studies showed that CT-26 murine adenocarcinoma cells, sensitive or resistant to doxorubicin (expressing high levels of P-glycoprotein), injected into normal syngeneic Balb/c mice produced rapidly growing tumors. The data do not demonstrate a correlation between the immunogenic properties of drug-resistant tumor cells and the expression of P-glycoprotein.

Background: Understanding the mechanism of prostate cancer metastasis is essential to the design of a more effective therapy. An effective therapy for this disease will depend on the development of a clinically relevant in vivo model., Purpose: We describe the development of such a model by using orthotopic implantation of human prostate cells in BALB/c nude mice., Method: We compared the tumorigenicity of and the incidence of metastasis of human prostate cancer PC-3M and LNCaP-FGC (LNCaP) cell lines subsequent to prostatic (orthotopic) or subcutaneous (ectopic) implantations in male nude mice., Results: LNCaP cells produced tumors only in the prostate. Enhanced tumorigenicity at the orthotopic site was found for PC-3M cells. Lymph node metastases were observed in practically all mice given an injection of PC-3M cells in the prostate, but they were uncommon with subcutaneous injection of these cells. Bilateral orchiectomy did not alter the tumorigenicity of either PC-3M or LNCaP cells or the incidence of lymph node metastasis by PC-3M cells. LNCaP tumors in the mouse prostate (but not PC-3M tumors) elaborated detectable levels of human prostate-specific antigen (PSA) in the serum, even when tumors were small (1.5 mm in diameter). Immunohistochemistry analysis revealed the presence of the PSA marker in tissue sections of LNCaP but not of PC-3M tumors., Conclusions: The implantation of human prostate cancer cells in an ectopic environment does not permit expression of metastatic potential. In contrast, intraprostatic implantation does., Implications: These data suggest that the orthotopic injection of human prostate cancer cells into the nude mouse may provide a valuable model to study the biology and therapy of human prostate cancer.

The purpose of these experiments was to evaluate the possibility that the systemic administration of liposomes containing synthetic macrophage activation CGP 31362 or CGP 19835 in mice which were simultaneously receiving injections of gamma-interferon or interleukin 2 would lead to enhanced regression of spontaneous lung metastases produced by syngeneic renal adenocarcinoma. The kidneys of BALB/c mice were given injections of renal adenocarcinoma cells, and 10 days later the kidney with local tumor was surgically resected. These mice were then given injections i.v. with liposomes and with gamma-interferon (s.c.) or interleukin 2 (i.p.). Systemic administration of MLV-CGP 31362 and MLV-CGP 19835A significantly reduced the number of lung metastases in nephrectomized mice. Both lung tumor burden and regional recurrence were further reduced by the s.c. injection of gamma-interferon or i.p. injection of interleukin 2. Long-term survivors were observed only in the groups of animals treated with liposomes containing macrophage activators and with lymphokines. Evaluation of host responsiveness to this immunotherapy revealed in situ activation of alveolar macrophages by administration of MLV-CGP 31362 or MLV-CGP 19835A, which was enhanced in mice also treated with interleukin 2. Normal levels of natural killer cell activity were reduced in the spleens of tumor-bearing mice but were restored subsequent to treatment with MLV-CGP 31362. These results indicate the potential usefulness of treating metastatic renal cell carcinoma by systemic administration of liposomes containing synthetic macrophage activators in combination with parental injections of lymphokines.

Three syngeneic murine tumor models were used to determine potential interactions between chemotherapeutic drugs and the synthetic liposome-encapsulated macrophage activator, muramyl tripeptide phosphatidylethanolamine (MLV-19835). Experiments were designed to maximize any additive toxicity of the simultaneous administration of MLV-19835 on the known myelosuppressive effects of doxorubicin, ifosfamide, and cisplatin. Treatment with these drugs resulted in diminished blood leukocyte counts, altered leukocyte differentials, and decreased hematocrits, but the systemic administration of MLV-19835 produced no additional deleterious effects. Myelosuppression normally observed at 2 weeks following treatment of mice with doxorubicin was prevented by combination treatment with MLV-19835. In addition, there was no interference of the antitumor activity of ifosfamide or doxorubicin against subcutaneous, kidney, and spleen tumors. These studies and the recent demonstration of the biological activity of MLV-19835 in phase II trials of osteosarcoma recommend clinical testing of these combined modalities.

These studies were undertaken to determine the mechanism for augmented tumoricidal activity of alveolar macrophages (AM) in mice injected intravenously with multilamellar liposomes containing a lipopeptide analogue of Gram-negative bacteria cell wall (MLV-CGP 31362) and intraperitoneally with interleukin 2 (IL-2). BALB/c mice were injected into the kidney with syngeneic renal carcinoma cells. Ten days later, this kidney was resected, and the mice were treated intravenously with MLV-CGP 31362 and/or intraperitoneally with IL-2. Treatment with MLV-CGP 31362 led to a reduction in the number of lung metastases, whereas treatment with IL-2 alone did not. The coadministration of intravenous liposomes and intraperitoneal IL-2 produced significant eradication of lung metastases. MLV-CGP 31362 (iv) and IL-2 (ip) were injected both into control immune-competent and nude mice or into mice whose natural killer (NK) cells had been depleted by systemic administration of anti-asialo GM1 antibodies. MLV-CGP 31362 activated tumoricidal properties in AM of all groups of mice. The additive tumoricidal activation of AM by IL-2 was associated with its effects on both T cells and NK cells.

Current therapies for renal cell carcinoma have been limited by the unresponsiveness of metastatic disease to conventional treatments. Although the use of biological response modifiers as adjuvant therapy has generally not been successful against disseminated disease, in situ activation of macrophages to a tumoricidal state by liposome-encapsulated immunomodulators has been shown to eradicate metastatic cancer in murine tumor models. We, therefore, designed experiments to evaluate the ability of a new macrophage activator, CGP 31362, a synthetic bacterial cell wall analogue, to cause regression of spontaneous lung metastases in mice whose primary renal adenocarcinoma was removed by nephrectomy. Delivery of the CGP 31362 to the lungs was accomplished by its encapsulation in multilamellar phospholipid liposomes (MLV-CGP 31362). Therapy with repeated i.v. injections of MLV-CGP 31362 significantly reduced the number of lung metastases in nephrectomized mice. Therapeutic efficacy of MLV-CGP 31362 was influenced by the encapsulation ratio of CGP 31362 to total phospholipid, the dose of injected liposomes, and the frequency of administration. Optimal therapy was achieved by combining the use of i.v. MLV-CGP 31362 with the s.c. injection of recombinant murine gamma interferon. Administration of MLV-CGP 31362 prior to removal of the primary tumor and continuing postoperatively was superior to postoperative therapy alone. Several lines of evidence indicate that in situ activation of macrophages was responsible for the therapeutic effects of MLV-CGP 31362: (a) macrophages harvested from the lungs of treated mice had significant tumoricidal activity against cultured renal carcinoma cells, (b) activated macrophages, as defined by the MRP-14 marker, were present in lung tumor nodules of treated mice but not untreated mice, and (c) the in situ activation of alveolar macrophages was consistent with the in vivo deposition of 60% of radiolabeled MLV-CGP 31362 liposomes in the lungs following i.v. injection. The results reported here represent the first in vivo evaluation of MLV-CGP 31362 and offer additional evidence that macrophage combination with therapies that reduce tumor burden.

We determined whether the intravenous administration of multilamellar vesicle liposomes (MLV) containing a lipopeptide analogue of a fragment from the cell wall of gram-negative bacteria (CGP 31362) can render BALB/c mouse alveolar macrophages tumoricidal in situ and reduce the incidence of spontaneous lung metastasis of syngeneic renal carcinoma (RENCA) cells. Alveolar macrophages (a) incubated in vitro with MLV containing CGP 31362 (MLV-31362) and (b) harvested from mice injected i.v. with MLV-31362 were rendered cytotoxic against the RENCA cells. Maximum cytotoxic activity of the macrophages was induced by injecting 5 mumol MLV consisting of 250 mg phospholipids and 0.5 mg CGP 31362. The single i.v. injection of 5 mumol MLV-31362 produced activation of macrophages that lasted for up to 4 days. Repeated i.v. injections of MLV-31362 produced a continuous antitumor activity in alveolar macrophages. To study the lipopeptide's effects on metastasis, we injected the left kidneys of BALB/c mice with RENCA cells. The kidney with growing tumor was resected 10 days later and, after a further 2 days, groups of mice were injected i.v. with MLV-31362 or with MLV-HBSS (twice weekly for 3 weeks). Treatment with MLV-31362 significantly decreased the median number of spontaneous lung metastases. These data demonstrate that the systemic administration of MLV-31362 can activate murine lung macrophages in situ and reduce the incidence of spontaneous RENCA lung metastases.

The purpose of this study was to characterize the antiproliferative activity of a recombinant interferon-alpha (IFN-alpha) against a newly established human adenocarcinoma cell line (DMS-4C) and to determine whether IFN-alpha entrapped in multilamellar liposomes had superior antitumor effects compared with free IFN-alpha. Treatment of DMS-4C cells with 100 U/ml of free IFN-alpha resulted in 34% cytostasis. IFN-alpha encapsulated in phosphatidylcholine/phosphatidylserine multilamellar vesicles produced growth inhibition of 67%, which was significantly greater than that produced by free IFN-alpha or by control liposomes containing only medium combined with free IFN-alpha. Moreover, kinetic analysis revealed that to produce significant cytolysis, free IFN-alpha had to be incubated with target cells for at least 24 h, whereas IFN-alpha encapsulated into liposomes required only 30 min of exposure.

Current therapy of human superficial bladder cancer includes the intravesical administration of antitumor drugs and immunomodulators. The purpose of these studies was to determine whether phospholipid liposomes that bind to human bladder cancer cells can improve the delivery of interferon alpha (IFN-alpha) to neoplastic urothelium. The antiproliferative activity of free IFN-alpha and IFN-alpha encapsulated in liposomes was assessed in vitro against the human transitional cell carcinoma line 253J. The cells were exposed to free and liposome-encapsulated IFN-alpha for short periods ranging from 30 minutes to four hours, and inhibition of cell growth was determined three days later. The production of greater than 25 percent cytostasis of 253J cells by free IFN-alpha required four hours of continuous exposure. In contrast, IFN-alpha encapsulated in liposomes produced 35 percent and 60 percent cytostasis after a 30-minute and four-hour exposure, respectively. Liposome-encapsulated IFN-alpha was also effective (50 percent cytostasis) against a subline of 253J cells selected for resistance against free IFN-alpha. Liposomes containing IFN-alpha were stable in the presence of human urine. In vivo studies in mice showed that intravesical administration of radiolabeled IFN-alpha or radiolabeled liposomes did not yield significant systemic absorption and deposition in distant organs. Collectively, these results suggest that the encapsulation of IFN-alpha within multilamellar liposomes may augment its antiproliferative activity, overcome some forms of tumor cell resistance to IFN-alpha, and prove useful for intravesical therapy of superficial bladder cancer.

We established variants resistant to human interferon (IFN) from an IFN-sensitive human colon carcinoma cell line and delineated some of the mechanisms for resistance to IFN-mediated cytotoxicity. The parent KM12C cells were incubated for 2 months in medium containing recombinant human IFN-alpha hybrid BBDD (r-IFN-alpha) or recombinant human IFN-gamma (r-IFN-gamma). Surviving variants were designated KM12 alpha R and KM12 gamma R, respectively. KM12 alpha R cells were cross-resistant to the cytostatic and cytolytic effects of r-IFN-alpha, r-IFN-beta, and r-IFN-gamma, whereas KM12 gamma R cells were resistant only to the effects of r-IFN-gamma. The parent and variant cell lines had similar in vitro growth rates and similar tumorigenicity in male BALB/c nude mice, but the mechanisms for resistance to IFNs differed in the two variant lines. The resistance of the cross-resistant KM12 alpha R cell line was not attributable to the loss of specific receptors, because our analyses demonstrated the presence of receptors for IFN-gamma, whereas the KM12 gamma R line lacked specific receptors for IFN-gamma. Northern blot analyses revealed that messenger RNA (mRNA) from the proto-oncogene c-myc was equally expressed in the IFN-sensitive and IFN-resistant cell lines and that treatment with r-IFN-gamma did not alter its expression. Treatment with r-IFN-gamma induced the expression of manganous superoxide dismutase mRNA in KM12C and KM12 alpha R cells, but not in KM12 gamma R cells, confirming that both KM12C and KM12 alpha R cells, but not KM12 gamma R cells, have functional receptors for IFN-gamma.

Experiments were designed to determine the effectiveness of active immunotherapy, both specific (neuraminidase-treated cells) and nonspecific [bacillus Calmette-Guerin (BCG) organisms] in the L1210-BDF1 tumor-host system. Tumor burden was minimized with chemotherapy (1,3-bis-(20chloroethyl)-1-nitrosourea) prior to immunotherapy. The effectiveness of immunotherapy was dependent on the amount of drug used to minimize tumor burden. An interval 36 hours between chemotherapy and immunotherapy produced the maximum number of survivors. A single immunization with 10(4) neuraminidase-treated cells was superior to other single or multiple immunizations. BCG was most effective when mice were given 393 X 10(5) organisms. Beneficial effects of immunotherapy were observed only when immunizations were given by an intraperitoneal route. All mice cured of tumor developed tumor-specific immunity. The highest levels of immunity were observed in mice given both neuraminidase-treated cells and BCG organisms after chemotherapy.