Therapeutic targeting of membrane-associated GRP78 in leukemia and lymphoma: preclinical efficacy in vitro and formal toxicity study of BMTP-78 in rodents and primates

Translation of drug candidates into clinical settings requires demonstration of preclinical efficacy and formal toxicology analysis for filling an Investigational New Drug (IND) application with the US Food and Drug Administration (FDA). Here, we investigate the membrane-associated glucose response protein 78 (GRP78) as a therapeutic target in leukemia and lymphoma. We evaluated the efficacy of the GRP78-targeted proapoptotic drug bone metastasis targeting peptidomimetic 78 (BMTP-78), a member of the D(KLAKLAK)2-containing class of agents. BMTP-78 was validated in cells from patients with acute myeloid leukemia and in a panel of human leukemia and lymphoma cell lines, where it induced dose-dependent cytotoxicity in all samples tested. Based on the in vitro efficacy of BMTP-78, we performed formal good laboratory practice toxicology studies in both rodents (mice and rats) and nonhuman primates (cynomolgus and rhesus monkeys). These analyses represent required steps towards an IND application of BMTP-78 for theranostic first-in-human clinical trials.

Targeting IL11 Receptor in Leukemia and Lymphoma: A Functional Ligand-Directed Study and Hematopathology Analysis of Patient-Derived Specimens

PURPOSE

The IL11 receptor (IL11R) is an established molecular target in primary tumors of bone, such as osteosarcoma, and in secondary bone metastases from solid tumors, such as prostate cancer. However, its potential role in management of hematopoietic malignancies has not yet been determined. Here, we evaluated the IL11R as a candidate therapeutic target in human leukemia and lymphoma.

EXPERIMENTAL DESIGN AND RESULTS

First, we show that the IL11R protein is expressed in a variety of human leukemia- and lymphoma-derived cell lines and in a large panel of bone marrow samples from leukemia and lymphoma patients, whereas expression is absent from nonmalignant control bone marrow. Moreover, a targeted peptidomimetic prototype (termed BMTP-11), specifically bound to leukemia and lymphoma cell membranes, induced ligand-receptor internalization mediated by the IL11R, and resulted in a specific dose-dependent cell death induction in these cells. Finally, a pilot drug lead-optimization program yielded a new myristoylated BMTP-11 analogue with an apparent improved antileukemia cell profile.

CONCLUSIONS

These results indicate (i) that the IL11R is a suitable cell surface target for ligand-directed applications in human leukemia and lymphoma and (ii) that BMTP-11 and its derivatives have translational potential against this group of malignant diseases.

Design, development, and validation of a high-throughput drug-screening assay for targeting of human leukemia

BACKGROUND

The authors developed an ex vivo methodology to perform drug library screening against human leukemia.

METHODS

The strategy for this screening relied on human blood or bone marrow cultures under hypoxia; under these conditions, leukemia cells deplete oxygen faster than normal cells, causing a hemoglobin oxygenation shift. Several advantages were observed: 1) partial recapitulation of the leukemia microenvironment, 2) use of native hemoglobin oxygenation as a real-time sensor/reporter, 3) cost-effectiveness, 4) species specificity, and 5) a format that enables high-throughput screening.

RESULTS

For a proof of concept, a chemical library (size, approximately 20,000 compounds) was screened against human leukemia cells. Seventy compounds were identified ("hit" rate, 0.35%; Z-factor = 0.71) that had activity, and 20 compounds were examined to identify 18 true-positive compounds (90%). Finally, the results demonstrated that carbonohydraxonic diamide group-containing compounds are potent antileukemia agents that induce cell death in leukemia cells and in patient-derived samples.

CONCLUSIONS

The current results indicated that this unique functional assay can identify novel drug candidates and can help with the development of future applications in personalized drug selection for patients with leukemia.

Abstract 2903: Therapeutic targeting of leukemia and lymphoma with a neuropilin-1 binding pro-apoptotic peptide

Targeted drug delivery offers an opportunity for the development of safer and more effective therapies for the treatment of cancer. In this study, we sought to identify short cell-internalizing peptide ligands that bind to specific cell surface receptors on malignant hematopoietic cells. Such targeting motifs could also serve as vehicles for preferential delivery of cytotoxic agents to leukemias and lymphomas. By screening of human leukemia cells with a combinatorial phage display peptide library, we isolated a peptide motif, sequence FF/YXLRS, which bound to human leukemia and lymphoma cell lines as well as to primary human acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) bone marrow specimens obtained from patients. The motif was internalized through a receptor-mediated pathway, and we next identified the corresponding receptor as the transmembrane glycoprotein neuropilin-1 (NRP-1). Moreover, the functional relevance of this internalizing receptor was evaluated in the context of disease progression via the targeted delivery of a pro-apoptotic peptidomimetic to leukemia and lymphoma cells, and a potent anti-leukemia cell effect was observed both with cell lines and patient samples when the targeting motif was synthesized in tandem to the pro-apoptotic sequence D(KLAKLAK)2. Markedly, the pro-apoptotic peptide did not have an effect on purified mononuclear cells from normal bone marrow cells. Finally, our results confirmed increased expression of NRP-1 in representative human leukemia and lymphoma cell lines and in a panel of bone marrow specimens obtained from patients with ALL or AML compared to normal bone marrow specimens. Taken together, our results indicate that NRP-1 could, potentially, be used as a target for ligand-directed therapy in human leukemias and lymphomas - as well as in many human solid tumors, which are also know to over-express NRP-1 - and that the prototype CGFYWLRSC-GG-D(KLAKLAK)2 is a promising drug candidate in this setting.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2903. doi:1538-7445.AM2012-2903

Identification of novel peptide inhibitors for human trypsins

Human trypsin isoenzymes share extensive sequence similarity, but certain differences in their activity and susceptibility to inhibitors have been observed. Using phage display technology, we identified seven different peptides that bind to and inhibit the activity of trypsin-3, a minor trypsin isoform expressed in pancreas and brain. All of the peptides contain at least two of the amino acids tryptophan, alanine and arginine, whereas proline was found closer to the N-terminus in all but one peptide. All peptides contain two or more cysteines, suggesting a cyclic structure. However, we were able to make synthetic linear variants of these peptides without losing bioactivity. Alanine replacement experiments for one of the peptides suggest that the IPXXWFR motif is important for activity. By molecular modeling the same amino acids were found to interact with trypsin-3. The peptides also inhibit trypsin-1, but only weakly, if at all, trypsin-2 and -C. As trypsin is a highly active enzyme which can activate protease-activated receptors and enzymes that participate in proteolytic cascades involved in tumor invasion and metastasis, these peptides might be useful lead molecules for the development of drugs for diseases associated with increased trypsin activity.

A novel and selective membrane type-1 matrix metalloproteinase (MT1-MMP) inhibitor reduces cancer cell motility and tumor growth

Matrix metalloproteinases (MMPs), and especially membrane type-1 matrix metalloproteinase (MT1-MMP, MMP-14), play a role in cancer progression and can have a prognostic value. Various synthetic broad-spectrum MMP inhibitors have been developed but have had little success in cancer patient treatment owing to side effects. Until recently, selective targeting of specific MMPs has not been possible due to lack of specific inhibitors. Here we have developed a selective MT1-MMP peptide-inhibitor GACFSIAHECGA, which did not affect the activities of many other MMPs including MMP-1, -2, -3, -7, -8, -9, -10, -11, -12, -13, -15, -17 or -20. In a fluorescent peptide cleavage assay it displayed an IC(50) value of 150 microM. The peptide effectively inhibited the migration and invasion of cancer cell lines in vitro. Furthermore, in vivo the peptide reduced the growth of tongue carcinoma xenografts and prolonged the survival of mice. Overall these results suggest that selective MT1-MMP inhibitors may have utility as anticancer agents.

Autologous Stem Cell Transplantation in Patients with Primary Amyloidosis: A Nation-wide Survey

Due to poor prognosis with conventional therapy, high-dose therapy (HDT) with autologous stem cell transplantation (ASCT) is considered for treatment in patients with primary amyloidosis (AL). Only single centre series are available on the feasibility and efficacy of this approach. Altogether 20 AL patients (11 males, 9 females, median age 54 years) were included in HDT protocols in 5 Finnish transplant centres between 1997 and 2003. Twelve patients were mobilized with granulocyte colony-stimulating factor (G-CSF) alone and 8 patients with a combination of cyclophosphamide and G-CSF. Sixteen patients (80%) went on to high-dose melphalan. Early transplant-related mortality was 25%. Nine out of 11 evaluable patients showed improvement or stabilization of AL. The overall survival of the transplanted patients is 69% (median follow-up 13 months). After a median follow-up of 26 months for the living patients, only 2 patients (18%) have shown progression of AL. This retrospective nation-wide analysis shows that HDT with ASCT leads to improvement or stabilization of AL in the majority of the patients who survive the immediate posttransplant period. A randomized multicentre trial is needed to show whether ASCT is superior to conventional therapy in patients with AL.

Blood monocytes and serum and bone marrow lysozyme in sarcoidosis

Serum lysozyme (LZM) concentrations were correlated to the number of neutrophils and monocytes in patients with sarcoidosis and nongranulomatous diseases. In sarcoidosis patients with an increased activity of serum angiotensin converting enzyme (ACE), a positive correlation was noted between LZM and blood monocytes. In sarcoidosis patients with normal ACE activity, as well as in patients with non-granulomatous diseases, a correlation was found between blood neutrophils and LZM, but not between blood monocytes and LZM. LZM was found in bone marrow plasma and in serum in a ratio of 1.5 to 1. Sarcoidosis patients had 30% higher LZM levels than healthy controls. The concentration of LZM in bone marrow plasma did not correlate to detectable granulomas in bone marrow specimens. The positive correlation between blood monocytes and LZM in patients with clinically active sarcoidosis is possibly due to recruitment of bone marrow monocytes for the granuloma formation.

Prognostic significance of lymphopenia in sarcoidosis

During 1959--67, sarcoidosis were diagnosed in a series of 140 patients. All were followed up and 22 developed chronic sarcoidosis. In 134 patients (20 with chronic course) the initial granulocyte, monocyte and lymphocyte counts were known. No differences in granulocyte values were seen between different groups of sarcoidosis patients. Patients with erythema nodosum had significantly increased monocyte levels. Lymphopenia below 1 000/microliter was seen in only 7.5% of the patients. Lymphocyte counts below 1 500 microliter were a common finding, especially in patients developing chronic sarcoidosis. Significantly decreased lymphocyte values were also seen in patients older than 40 years at the time of diagnosis, in patients negative to 10 TU of PPD and in those with a disease requiring treatment with corticosteroids. A correlation was found between initial lymphopenia and less favourable prognosis, 85% of the patients having a very good prognosis. Patients with initial lymphopenia must be carefully followed up. The initial presence of erythema nodosum does not always guarantee a good prognosis.

Combinatorial targeting of the macropinocytotic pathway in leukemia and lymphoma cells

Ligand-directed delivery of agents to leukemia and lymphoma cells has the potential to yield new mechanistic disease insights and targeted therapies. Here we set out to target the macropinocytotic pathway with a combinatorial approach. From the screening of acute T-lymphoblastic leukemia Molt-4 cells with a random phage-display peptide library, we isolated a phage displaying the sequence CAYHRLRRC. This peptide contains a lymph node-homing motif (Cys-Ala-Tyr) and a cell-penetrating motif (Arg-Leu-Arg-Arg). Binding of this ligand-directed phage to a large panel of leukemia/lymphoma cells and to patient-derived samples was much higher than to non-leukemia control cells. CAYHRLRRC phage internalization into Molt-4 cells is both energy- and temperature-dependent. Flow cytometry with fluorescein-labeled peptide and endocytosis blocking with specific inhibitors revealed that CAYHRLRRC is indeed taken up through macropinocytosis in Molt-4 and K562 human leukemia cells. Unexpectedly, the cell surface receptor for the CAYHRLRRC peptide is not a heparan sulfate proteoglycan as it would be predicted for other cell-penetrating peptides. Confirming this interpretation, a CAYHRLRRC-directed peptidomimetic-induced cell death in all the leukemia and lymphoma cells was evaluated, whereas a control transactivator of transcription protein (tat)-directed proapoptotic peptidomimetic was non-selective. In summary, the targeting peptide CAYHRLRRC is selectively internalized through macropinocytosis in leukemia and lymphoma cells and has potential as a drug lead for ligand-directed anti-leukemia therapies.

AlphaMbeta2 integrin modulator exerts antitumor activity in vivo

BACKGROUND

Leukocyte immunomodulation has great clinical potential as a therapy of inflammatory conditions and cancer. We have recently developed leukocyte alphaMbeta2 integrin targeting small molecule (IMB-10) capable of inhibiting leukocyte migration and recruitment in vitro and in vivo.

MATERIALS AND METHODS

The purpose of this study was to investigate the potential anticancer effects of IMB-10 using U937 histiocytic lymphoma, OCI-AML-3 acute myeloid leukemia and HSC-3 tongue squamous cell carcinoma xenografts in athymic nude mice lacking T-lymphocytes.

RESULTS

IMB-10 therapy inhibited the growth of both leukemia and lymphoma xenografts and significantly prolonged the survival of the mice with lymphoma. Interestingly, IMB-10 also reduced host leukocyte infiltration in tumors and affected the invasion potential of squamous cell carcinomas.

CONCLUSION

IMB-10 has potential as a therapy for leukocytic malignancies, particularly for lymphomas. Since it also inhibited HSC-3 carcinoma invasion, most likely by blockage of the tumor-infiltrating leukocytes, we suggest that the host inflammation process may affect tumor progression also in a T-cell independent manner.

Cell-surface association between matrix metalloproteinases and integrins: role of the complexes in leukocyte migration and cancer progression

Leukocyte motility is known to be dependent on both β2-integrins and matrix metalloproteinases MMP-2/-9 or gelatinases, which mediate leukocyte adhesion and the proteolysis needed for invasion, respectively. Gelatinases not only play an important role in cell migration, tissue remodeling, and angiogenesis during development, but are also involved in the progression and invasiveness of many cancers, including leukemias. The concept that MMPs associate with integrins, as well as their importance in some physiologic and pathologic conditions, has been advanced previously but has not been examined on leukocytes. This review will examine mainly the function of the MMP-integrin complexes in normal leukocyte migration and the effect of integrin and broad-spectrum MMP inhibitors in tumor progression.

Late non-relapse mortality among adult autologous stem cell transplant recipients: a nation-wide analysis of 1482 patients transplanted in 1990–2003

Data on the incidence and causes of late (>100 d) non-relapse mortality (NRM) in autologous stem cell transplant (ASCT) recipients is limited. We have analysed NRM in a cohort of 1,482 adult patients who received ASCT in 1990-2003 in six Finnish transplant centres. The most common diagnoses included non-Hodgkin's lymphoma (NHL) (n = 542), multiple myeloma (MM) (n = 528), breast cancer (n = 132); Hodgkin's lymphoma (HL) (n = 86) and chronic lymphocytic leukaemia (CLL) (n = 63). Until September 2005, 646 patients (44%) have died. Late NRM was observed in 68 patients (4.6% of ASCT recipients; 11% of all deaths). There were 38 males and 30 females with a median age of 58 yr (20-69) at the time of ASCT. The median time to NRM was 27 months from ASCT (3-112). The risk of NRM was highest in patients with CLL (9.5%) and those with HL (8.1%) followed by MM and NHL (4.9% and 4.8%, respectively). The risk of late NRM was comparable in patients who received total body irradiation (TBI) and those who received chemotherapy-only regimens (6.7% vs. 4.3%). Another malignancy was the most common cause of late NRM (24 patients, 35% of late NRM). Twelve patients (0.8% of ASCT recipients) have died due to secondary haematological malignancy. Altogether 22 patients (32% of late NRM) died from infectious causes. Malignancies and late infections are important causes of NRM after ASCT. These facts point out the importance of prolonged follow-up in ASCT recipients.

Autologous stem cell transplantation in patients with chronic lymphocytic leukaemia: the Finnish experience

Although autologous stem cell transplantation (ASCT) has gained some popularity as a treatment option in patients with chronic lymphocytic leukaemia (CLL), limited multicentre data are available on the feasibility and efficacy of this approach. Between January 1995 and June 2005, 72 patients with CLL received ASCT in five Finnish centres. There were 45 men and 27 women with a median age of 57 years (38-69). The median time from diagnosis to ASCT was 32 months (6-181) and the median number of prior regimens 1 (1-4). All patients received blood stem cell grafts and CD34+ selection had been performed in 44 patients (61%). The most common high-dose regimen was a total body irradiation plus cyclophosphamide (38 patients, 53%). No early treatment-related deaths were observed. With a median follow-up of 28 months from ASCT, a relapse or progression has been observed in 27 patients (37%). The projected progression-free survival is 48 months (confidence interval (CI) 30-66). The projected median overall survival is 95 months (CI 74-101) from ASCT and is not influenced by graft selection or conditioning regimen used. Autologous stem cell transplantation is a feasible treatment option for CLL. Randomized trials against alternative treatments are needed to assess the impact of ASCT on the clinical course of CLL.

Stabilization of the activated alphaMbeta2 integrin by a small molecule inhibits leukocyte migration and recruitment

Integrins are potential targets for the development of antiinflammatory agents. Here we develop a novel high-throughput assay by allowing a chemical library to compete with phage display peptide binding and identify a novel small-molecule ligand to the leukocyte-specific alpha(M)beta(2) integrin. The identified thioxothiazolidine-containing compound, IMB-10, had an unexpected activity in that it stabilized binding of alpha(M)beta(2) to its endogenous ligands proMMP-9 and fibrinogen. Single amino acid substitutions in the activity-regulating C-terminal helix and the underlying region in the ligand-binding I domain of the integrin suppressed the effect of IMB-10. A computational model indicated that IMB-10 occupies a distinct cavity present only in the activated form of the integrin I domain. IMB-10 inhibited alpha(M)beta(2)-dependent migration in vitro and inflammation-induced neutrophil emigration in vivo. Stabilization of integrin-mediated adhesion by a small molecule is a novel means to inhibit cell migration and may have a utility in treatment of inflammatory diseases involving leukocyte recruitment.

Human tongue carcinoma growth is inhibited by selective antigelatinolytic peptides

Matrix metalloproteinases (MMP-2 and MMP-9, or gelatinases) are involved in tongue SCC invasion, metastasis and angiogenesis. We have recently shown that a novel and selective hydrophobic cyclic CTTHWGFTLC (CTT1) peptide is inhibitor for MMP-2 and MMP-9 (Koivunen et al., Nat Biotechnol 1999; 17:768-74). In this study, we demonstrate that both the new hydrophilic derivate GRENYHGCTTHWGFTLC (CTT2) peptide and the CTT1 peptide inhibited specifically the human tongue squamous cell carcinoma (HSC-3) cell-derived gelatinolytic activity and in vitro invasion and migration of these cells (p < or = 0.049). In situ zymography revealed that both peptides also inhibited clearly almost all of the gelatinolytic activity present in the human tongue SCC tissue sections, indicating that MMP-2 and MMP-9 are the major gelatinases detected in the tongue carcinomas. However, CTT2 did not inhibit the type I collagen degradation by human collagenases (MMP-1, MMP-8 and MMP-13). Furthermore, CTT2 reduced the blood vessel density (p < or = 0.043) and clearly improved the survival of the mice bearing human tongue carcinoma xenografts (p < or = 0.012). Overall, we suggest that CTT1 and CTT2 peptides being selective gelatinase inhibitors with significant anti-tumor properties could be useful to diminish the invasion and angiogenesis of human tongue carcinomas characterized by enhanced gelatinolytic activity in tumors.

Novel peptide inhibitors of human kallikrein 2

Human kallikrein 2 (hK2) is a serine protease produced by the secretory epithelial cells in the prostate. Because hK2 activates several factors participating in proteolytic cascades that may mediate metastasis of prostate cancer, modulation of the activity of hK2 is a potential way of preventing tumor growth and metastasis. Furthermore, specific ligands for hK2 are potentially useful for targeting and imaging of prostate cancer and for assay development. We have used enzymatically active recombinant hK2 captured by a monoclonal antibody exposing the active site of the enzyme to screen phage display peptide libraries. Using libraries expressing 10 or 11 amino acids long linear peptides, we identified six different peptides binding to hK2. Three of these were shown to be specific and efficient inhibitors of the enzymatic activity of hK2 toward a peptide substrate. Furthermore, the peptides inhibited the activation of the proform of prostate-specific antigen by hK2. Amino acid substitution analyses revealed that motifs of six amino acids were required for the inhibitory activity. These peptides are potentially useful for treatment and targeting of prostate cancer.

Early treatment-related mortality in adult autologous stem cell transplant recipients: a nation-wide survey of 1482 transplanted patients

OBJECTIVES

To evaluate early (<100 d) treatment-related mortality (TRM) in autologous stem cell transplant (ASCT) recipients.

PATIENTS

Altogether 1482 adult patients received ASCT in six Finnish centres 1990-2003. The most common diagnoses were non-Hodgkin's lymphoma (NHL) (n = 542), multiple myeloma (MM) (n = 528), breast cancer (BC) (n = 132), Hodgkin's lymphoma (n = 86) and chronic lymphocytic leukaemia (CLL) (n = 63).

RESULTS

Forty-two patients (2.8%) died from treatment-related reasons <100 d from ASCT. The median time to death was 38 d from ASCT (0-99). The risk of TRM varied according to the diagnoses. The highest risk was observed in patients with AL amyloidosis (24%) followed by NHL (4.4%) and MM (1.9%). No early TRM was observed in patients transplanted for BC or CLL. Infections were the cause of death in 16 patients (fungal 7, bacterial 6, viral 3). Organ toxicity was responsible for early death in 26 patients (heart 9, lungs 7, other 10).

CONCLUSIONS

This nation-wide survey indicated a low early TRM in ASCT recipients in general, but higher risks in patients with AL amyloidosis or NHL. In addition to patient selection, also optimization of transplant procedure may be needed in these patient groups to reduce early TRM.

A tripeptide mimetic of von Willebrand factor residues 981-983 enhances platelet adhesion to fibrinogen by signaling through integrin alpha(IIb)beta3

BACKGROUND

RGD is a major recognition sequence for ligands of platelet alpha(IIb)beta3.

OBJECTIVE AND METHODS

To identify potential binding sites for alpha(IIb)beta3 apart from RGD, we screened phage display libraries by blocking the enrichment of RGD-containing phages with a GRGDS peptide and identified a novel integrin recognition tripeptide sequence, VPW.

RESULTS

Platelets adhered to an immobilized cyclic VPW containing peptide in a alpha(IIb)beta3-dependent manner; platelets and alpha(IIb)beta3-expressing CHO cells adhered faster to immobilized alpha(IIb)beta3-ligands in the presence of soluble VPW. In platelets adhering to fibrinogen, VPW accelerated the activation of the tyrosine kinase Syk which controls cytoskeletal rearrangements. In alpha(IIb)beta3-expressing CHO cells, VPW induced a faster formation of stress fibers. Sequence alignment positioned VPW to V980-P981-W982 in the von Willebrand factor (vWf) A-3 domain. In blood from a vWf-deficient individual, VPW increased platelet adhesion to fibrinogen but not to collagen under flow and rescued the impaired adhesion to vWf deficient in A-3.

CONCLUSION

These data reveal a VPW sequence that contributes to alpha(IIb)beta3 activation in in vitro experiments. Whether the V980-P981-W982 sequence in vWf shows similar properties under in vivo conditions remains to be established.

Autologous stem cell transplantation in patients with high-risk plasmacytoma

Although autologous stem cell transplantation (ASCT) is considered standard treatment in patients with multiple myeloma (MM), limited experience is available on this approach in patients with plasmacytoma (PC). Twelve patients with high-risk PC received ASCT in Finland 1994-2002. There were nine males and three females with a median age of 50 yr (32-64). Ten patients had a PC of bone, whereas two patients had extramedullary PCs. The median time from the diagnosis to ASCT was 9 months (5-100). At the time of ASCT six patients were in first complete remission (CR) or partial remission (PR), in four patients the disease was refractory to the first line therapy and two patients had relapsed. High-dose therapy consisted of melphalan (MEL)200 (n = 7), MEL200 x 2 (n = 3) or total body irradiation (TBI)-MEL140 (n = 2). No transplant-related deaths occurred. After ASCT eight patients (67%) were in CR, one patient in very good PR and one patient in PR; two patients were non-responders. With a median follow-up of 48 months from ASCT, 11 patients (92%) are alive. Six patients (50%) have relapsed or progressed 3-81 months from ASCT. ASCT is feasible in this patient population resulting in promising overall survival. A randomised trial is needed to assess the real value of ASCT when compared with other treatment options in patients with high-risk PC.

Gelatinase-mediated migration and invasion of cancer cells

The matrix metalloproteinases(MMP)-2 and -9, also known as the gelatinases have been long recognized as major contributors to the proteolytic degradation of extracellular matrix during tumor invasion. In the recent years, a plethora of non-matrix proteins have also been identified as gelatinase substrates thus significantly broadening our understanding of these enzymes as proteolytic executors and regulators in various physiological and pathological states including embryonic growth and development, angiogenesis and tumor progression, inflammation, infective diseases, degenerative diseases of the brain and vascular diseases. Although the effect of broad-spectrum inhibitors of MMPs in the treatment of cancer has been disappointing in clinical trials, novel mechanisms of gelatinase inhibition have been now identified. Inhibition of the association of the gelatinases with cell-surface integrins appears to offer highly specific means to target these enzymes without inhibiting their catalytic activity in multiple cell types including endothelial cells, tumor cells and leukocytes. Here, we review the multiple functions of the gelatinases in cancer, and especially their role in the tumor cell migration and invasion.

Radionuclide imaging of tumor xenografts in mice using a gelatinase-targeting peptide

Tumors express MMP-2 and MMP-9 gelatinases, which are involved in the formation of tumor vasculature. This suggests that a tumor and its surrounding neovasculature can be visualized by a sensitive gelatinase recognition method. We have studied tumor radioimaging using a gelatinase inhibitory peptide CTTHWGFTLC (CTT), which in a mouse model targets the tumor site following an intravenous injection. We determined a solution NMR structure of CTT and its retro-inversion peptide, and prepared 125I and 99mTc-labelled CTT peptide derivatives. Radiolabelled CTT inhibited gelatinases in vitro, and homed to a tumor xenograft in mice. In normal mice, CTT was instead rapidly cleared from the circulation mainly through the kidney and, after 24 h, no significant radioactivity was accumulated in healthy tissues. Gamma camera imaging of a primary tumor in live mice was obtained with double-labelled liposomes, which were coated with 99mTc-CTT and encapsulated with 125I albumin. CTT also targeted liposomes to the lungs of tumor-bearing mice, which may indicate the existence of non-visible lung micrometastases. Our studies suggest that selective gelatinase-targeting compounds could be useful in the early detection and imaging of primary tumors and metastases.

Peptide-Mediated Delivery of Therapeutic and Imaging Agents Into Mammalian Cells

Modern molecular targeting provides new opportunities for imaging, diagnosis and treatment of diseases. Small molecular weight peptides have the potential for enhancing targeting of compounds, and they may also have therapeutic effects by themselves. The limiting step for successful molecular targeting is the development of efficient peptide delivery systems. This review will focus on peptides developed by phage display and combinatorial chemistry for the delivery of pharmaceuticals, radioactive compounds and gene expression vectors. Target cell-specific delivery can be improved by peptides that penetrate the cell membrane or alternatively induce receptor-mediated endocytosis. In addition, peptides that contain endosomal escape signals or nuclear localization motifs may help trafficking of therapeutics to appropriate locations inside the cell. Small molecule radiolabelled peptides are the preferred agents for targeting and for diagnostic imaging of various organs as they are easily synthesized, effectively penetrate tissues, and are rapidly cleared from the circulation. Such peptides have been tested in animals and humans in the fields of cancer, cardiology, neurology, inflammation/infection, atherosclerosis and thrombosis.

Invasive fungal infections in autologous stem cell transplant recipients: a nation-wide study of 1188 transplanted patients

Based on small single-centre series, the risk of invasive fungal infections (IFI) has been considered small in autologous stem cell transplant (ASCT) recipients.

PURPOSE

To analyse epidemiological and clinical features of (IFI) among ASCT recipients in Finland 1990-2001.

PATIENTS

During the study period, 1188 adult patients received high-dose therapy supported by ASCT in six centres. Altogether, 1112 patients (94%) received blood progenitor cells. The graft was CD34+ selected in 261 patients (22%). The major diagnostic groups were non-Hodgkin's lymphoma (n = 417), multiple myeloma (n = 395), breast cancer (n = 132) and Hodgkin's lymphoma (n = 53).

RESULTS

Eighteen patients (1.5%) with IFI were identified. The incidence of proven or probable invasive aspergillosis was 0.8%, followed by candidaemia with an incidence of 0.3%. The median time to the diagnosis of IFI was 35 d (6-162) from the progenitor cell infusion. In fourteen patients (78%) IFI was diagnosed during lifetime and they were treated with antifungal therapy for a median of 50 d. Nine patients (64%) were cured.

CONCLUSIONS

IFI appears to be a rare event after ASCT and Aspergillus infections seem to be predominant. These epidemiological features have an impact in planning prophylactic and empirical antifungal strategies in ASCT recipients.

Peptide Inhibition of Catalytic and Noncatalytic Activities of Matrix Metalloproteinase-9 Blocks Tumor Cell Migration and Invasion

Migration of invasive cells appears to be dependent on matrix metalloproteinases (MMPs) anchored on the cell surface through integrins. We have previously demonstrated an interaction between the integrin alpha-subunit I domain and the catalytic domain of MMP-9. We now show that there is also an interaction between the integrin beta subunit and MMP-9. Using phage display, we have developed MMP-9 inhibitors that bind either to the MMP-9 catalytic domain, the collagen binding domain, or the C-terminal hemopexin-like domain. The C-terminal domain-binding peptide mimics an activation epitope in the stalk of the integrin beta chain and inhibits the association of MMP-9 C-terminal domain with alpha(V)beta(5) integrin. Unlike other MMP-9 binding peptides, it does not directly inhibit catalytic activity of MMP-9, but still prevents proenzyme activation and cell migration in vitro and tumor xenograft growth in vivo. We also find an association between MMP-9 and urokinase-plasminogen activator receptor and find that urokinase-plasminogen activator receptor is cleaved by MMP-9. Collectively, we have defined molecular details for several interactions mediated by the different MMP-9 domains.

Intracellular and Cell Surface Localization of a Complex between αMβ2 Integrin and Promatrix Metalloproteinase-9 Progelatinase in Neutrophils

We have recently demonstrated that promatrix metalloproteinases (proMMPs), particularly proMMP-9, are potent ligands of the leukocyte beta(2) integrins. We studied here the complex formation between proMMP-9 and alpha(M)beta(2), the major MMP and integrin of neutrophils. On resting neutrophils, the proMMP-9/alpha(M)beta(2) complex was primarily detected in intracellular granules, but after cellular activation it became localized to the cell surface, as demonstrated by immunoprecipitation and double immunofluorescence. Further indication of the complex formation was that neutrophils and alpha(M)beta(2)-transfected L cells, but not the wild-type L cells or leukocyte adhesion deficiency cells, bound to immobilized proMMP-9 or its recombinant catalytic domain in a beta(2) integrin-dependent manner. Peptides that bound to the alpha(M) integrin-I domain and inhibited its complex formation with proMMP-9 prevented neutrophil migration in a transendothelial assay in vitro and in a thioglycolate-elicited peritonitis in vivo. These results suggest that the translocating proMMP-9/alpha(M)beta(2) complex may be part of the cell surface machinery guiding neutrophil migration.

Oral treatment of acute myeloid leukaemia with etoposide, thioguanine, and idarubicin (ETI) in elderly patients: a prospective randomised comparison with intravenous cytarabine, idarubicin, and thioguanine in the second and third treatment cycle

A randomised multicentre study was conducted among patients over 65 yr of age with newly diagnosed acute myeloid leukaemia (AML) to compare oral treatment with etoposide 80 mg/m(2) and thioguanine 100 mg/m(2) twice daily on 5 d and idarubicin 15 mg/m(2) on 3 d (ETI) to a mainly i.v. combination of cytarabine 100 mg/m(2) twice daily on 5 d, idarubicin 12 mg/m(2) x 1, and thioguanine (TAI). Ninety-two patients were enrolled. Their median age was 72 yr, range 65-84 yr. Sixty-five patients had de novo AML, 21 AML subsequent to myelodysplastic syndrome, and six treatment-related AML. They received at first a 6-d i.v. treatment with cytarabine and idarubicin. After the first treatment, 68 patients were randomised to receive two cycles of ETI (n = 36) or TAI (n = 32) and thereafter maintenance with mercaptopurine and methotrexate. Of the 92 patients, 52 (57%) achieved remission at some stage. The median survival was 10 months. There were no significant differences between the patients randomised to ETI or TAI in the remission rate (67% vs. 72%), survival (12 months from randomisation in both arms), event-free survival or relapse rate. The patients randomised to receive ETI spent significantly fewer days at hospital during the two randomised cycles (20 vs. 41 d, P = 0.010), and they had fewer days with infusions, shorter neutropenias and thrombocytopenias and fewer and less severe infections. In conclusion, treatment with oral ETI resulted in a similar antileukaemic effect as obtained with mainly i.v. TAI, with less toxicity and reduced need for hospitalisation.

Identification of a negatively charged peptide motif within the catalytic domain of progelatinases that mediates binding to leukocyte beta 2 integrins

The alpha M beta 2 integrin of leukocytes can bind a variety of ligands. We screened phage display libraries to isolate peptides that bind to the alpha M I domain, the principal ligand binding site of the integrin. Only one peptide motif, (D/E)(D/E)(G/L)W, was obtained with this approach despite the known ligand binding promiscuity of the I domain. Interestingly, such negatively charged sequences are present in many known beta 2 integrin ligands and also in the catalytic domain of matrix metalloproteinases (MMPs). We show that purified beta 2 integrins bind to pro-MMP-2 and pro-MMP-9 gelatinases and that that the negatively charged sequence of the MMP catalytic domain is an active beta 2 integrin-binding site. Furthermore, a synthetic DDGW-containing phage display peptide inhibited the ability of beta 2 integrin to bind progelatinases but did not inhibit the binding of cell adhesion-mediating substrates such as intercellular adhesion molecule-1, fibrinogen, or an LLG-containing peptide. Immunoprecipitation and cell surface labeling demonstrated complexes of pro-MMP-9 with both the alpha M beta 2 and alpha L beta 2 integrins in leukocytes, and pro-MMP-9 colocalized with alpha M beta 2 in cell surface protrusions. The DDGW peptide and the gelatinase-specific inhibitor peptide CTTHWGFTLC blocked beta 2 integrin-dependent leukocyte migration in a transwell assay. These results suggest that leukocytes may move in a progelatinase-beta 2 integrin complex-dependent manner.

Use of intein-directed peptide biosynthesis to improve serum stability and bioactivity of a gelatinase inhibitory peptide

Screening of phage display libraries allows rapid identification of peptides binding to a target. However, functional analysis of the phage sequences and their reproduction as soluble and stable peptides are often the most time-consuming part in the screening. We have used here intein-based peptide biosynthesis to produce a phage-display derived gelatinase inhibitory peptide CTTHWGFTLC and to identify the critical residues for gelatinase inhibitory activity by performing alanine-scanning mutagenesis. By biosynthetic incorporation of 5-fluorotryptophan, we obtained an inhibitor of MMP-2 and MMP-9 gelatinases that showed a 6-fold enhancement in serum stability in comparison to the wild-type peptide. The new peptide also had an improved ability to inhibit tumor cell migration. These studies indicate the utility of intein methodology for synthesis and design of peptides obtained by phage display.

Steps toward mapping the human vasculature by phage display

The molecular diversity of receptors in human blood vessels remains largely unexplored. We developed a selection method in which peptides that home to specific vascular beds are identified after administration of a peptide library. Here we report the first in vivo screening of a peptide library in a patient. We surveyed 47,160 motifs that localized to different organs. This large-scale screening indicates that the tissue distribution of circulating peptides is nonrandom. High-throughput analysis of the motifs revealed similarities to ligands for differentially expressed cell-surface proteins, and a candidate ligand-receptor pair was validated. These data represent a step toward the construction of a molecular map of human vasculature and may have broad implications for the development of targeted therapies.

In vivo localization of gelatinases (MMP-2 and -9) by in situ zymography with a selective gelatinase inhibitor

In situ zymography provides a tool to localize proteolytic activity in tissues in vivo. However, it has been difficult to discriminate between the proteases responsible for the detected activity. We used a selective tissue-permeable gelatinase inhibitor, the CTTHWGFTLC-peptide (CTT) in inflamed human gingiva. The CTT-peptide was evidenced to home, target to, and selectively inhibit the areas of gelatinolytic activity in inflamed human gingiva expressing MMP-2 and -9. Gelatinolytic activity, MMP-9 immunoreactivity, and mRNA expression as well as CD-45-positive inflammatory cells colocalized well in the inflamed human gingival connective tissue. Gelatinolytic activity corresponding to MMP-2 colocalized with laminin-5 gamma2-chain immunoreactivity and was detected in the close vicinity of the sulcular basement membrane region. Furthermore, the CTT-peptide inhibited beta-caseinolysis by human MMP-2 and MMP-9 as well as laminin-5 gamma2-chain degradation by MMP-2 in vitro. Thus, the CTT-peptide may prove to be a useful tool (i) to discriminate between gelatinolytic proteases detected by in situ zymography and (ii) to preventMMP-2-dependent induction of epithelial cell migration and gelatinase-dependent tissue destruction in inflammatory and malignant diseases.

Development of novel peptide ligands modulating the enzyme activity of prostate-specific antigen

Prostate-specific antigen (PSA) is a serine proteinase produced mainly by epithelial cells of the prostate. Measurement of PSA in serum is widely used for diagnosis and monitoring of prostate cancer. The major problem of the PSA determination in early diagnosis is the high false positive rate due to benign prostatic hyperplasia, but the clinical accuracy can be improved by determining the proportions of various molecular forms of PSA. The main biological function of PSA is liquefaction of the seminal gel formed after ejaculation, but PSA has also been suggested to regulate invasiveness and metastatic potential of prostatic tumors. Thus, agents binding to and affecting the function of PSA have the potential to be used for diagnosis and therapy of prostate cancer. We have developed peptides specific for PSA by using cyclic phage display peptide libraries. After deducing the amino acid sequence of the peptides by sequencing the relevant part of phage genome, the peptides were expressed as glutathione-S-transferase (GST) fusion proteins or produced by chemical synthesis. The peptides were shown to bind to PSA specifically as indicated by lack of binding to other related serine proteinases. The binding of the peptides with PSA was strongly inhibited by monoclonal antibodies specific for free PSA and they did not bind to PSA-inhibitor complexes indicating that they bind close to the active site of the enzyme. Most of the peptides enhanced the enzyme activity of PSA against a chromogenic substrate. The affinity of the peptides could be increased by including Zn2+ in the reaction mixture. These results show that peptides that bind to PSA and modulate its enzyme activity can be developed by phage display techniques. These peptides have the potential to be used for targeting of prostatic tumors and diagnostics of prostate cancer.

The levels of trypsinogen isoenzymes in ovarian tumour cyst fluids are associated with promatrix metalloproteinase-9 but not promatrix metalloproteinase-2 activation

Proteolysis mediated by matrix metalloproteinases (MMPs) and serine proteinases is associated with cancer invasion and metastasis. Activation of latent proMMPs, and especially the proforms of the type IV collagen degrading gelatinases A and B (proMMP-2 and proMMP-9), is thought to be a critical step in this process. We have recently found that human tumour-associated trypsin-2 is a potent activator of proMMP-9 and it also activates proMMP-2 in vitro. Trypsinogen, MMP-2, and MMP-9 are expressed in ovarian cancer. To elucidate the function of trypsin in vivo, we studied whether high concentrations of trypsinogen-1, trypsinogen-2, their alpha(1)-proteinase inhibitor (API) complexes, and tumour-associated trypsin inhibitor (TATI) are associated with proMMP-2 and proMMP-9 activation in ovarian tumour cyst fluids. Zymography and immunofluorometric analysis of 61 cyst fluids showed a significant association between high trypsin concentrations and the activation of MMP-9 (P = 0.003-0.05). In contrast, the trypsin concentrations were inversely associated with the activation of MMP-2 (P = 0.01-0.02). Immunohistochemical analysis of ovarian tumour tissue demonstrated expression of trypsinogen-2 and TATI in the secretory epithelium. MMP-2 was detected both in stromal and epithelial cells whereas MMP-9 was detected in neutrophils and macrophage-like cells in stromal and epithelial areas. These results suggest that trypsin may play a role in the regulation of the MMP-dependent proteolysis associated with invasion and metastasis of ovarian cancer.

Inhibition of beta(2) integrin-mediated leukocyte cell adhesion by leucine-leucine-glycine motif-containing peptides

Many integrins mediate cell attachment to the extracellular matrix by recognizing short tripeptide sequences such as arginine-glycine-aspartic acid and leucine-aspartate-valine. Using phage display, we have now found that the leukocyte-specific beta(2) integrins bind sequences containing a leucine-leucine-glycine (LLG) tripeptide motif. An LLG motif is present on intercellular adhesion molecule (ICAM)-1, the major beta(2) integrin ligand, but also on several matrix proteins, including von Willebrand factor. We developed a novel beta(2) integrin antagonist peptide CPCFLLGCC (called LLG-C4), the structure of which was determined by nuclear magnetic resonance. The LLG-C4 peptide inhibited leukocyte adhesion to ICAM-1, and, interestingly, also to von Willebrand factor. When immobilized on plastic, the LLG-C4 sequence supported the beta(2) integrin-mediated leukocyte adhesion, but not beta(1) or beta(3) integrin-mediated cell adhesion. These results suggest that LLG sequences exposed on ICAM-1 and on von Willebrand factor at sites of vascular injury play a role in the binding of leukocytes, and LLG-C4 and peptidomimetics derived from it could provide a therapeutic approach to inflammatory reactions.

Binding of novel peptide inhibitors of type IV collagenases to phospholipid membranes and use in liposome targeting to tumor cells in vitro

We have recently described a novel cyclic peptide inhibitor CTTHWGFTLC (CTT) for matrix metalloproteinases (MMP)-2 and MMP-9, also called type IV collagenases or gelatinases (E. Koivunen et al., NAT: BIOTECHNOL:, 17: 768-774, 1999). As indicated by its amino acid composition, CTT is hydrophobic, and its partitioning into phospholipid films could be verified by the monolayer technique. Augmented fluorescence emission anisotropy (from 0.064 to 0.349) and reduced collisional quenching by I(-) of the Trp residue in CTT was evident in the presence of unilamellar phosphatidylcholine/phosphatidylethanolamine liposomes, revealing the association of CTT with the lipid bilayers. Gelatinases are potential targets of therapeutic intervention in cancer, and inhibitors of these enzymes can prevent tumor progression in animal models. CTT enhanced 3- to 4-fold the cellular uptake of liposome-encapsulated water-soluble fluorescent marker, rhodamine B by gelatinase-expressing cells. Gelatinase targeting seems to be essential, as modified peptides that were less potent gelatinase inhibitors were also less efficient in promoting the cellular uptake of liposomes. Augmented killing ( approximately 4-fold) of U937 leukemia and HT1080 sarcoma cells was obtained by the CTT-enhanced delivery of Adriamycin-containing liposomes, compared with control liposomes administered without the peptide. These results suggest a novel type of utility for small gelatinase inhibitors in targeted cancer therapy.

Pronounced monocytosis in a case of nephropathia epidemica

Nephropathia epidemica is a mild form of haemorrhagic fever with renal syndrome. Thrombocytopenia is common and characteristic. We report here a case of a young man with nephropathia epidemica and marked transient monocytosis.

Vascular matrix metalloproteinase-2-dependent cleavage of calcitonin gene-related peptide promotes vasoconstriction

Matrix metalloproteinase (MMP)-2 has been historically associated with the process of vascular remodeling through the cleavage of extracellular matrix proteins. However, we recently found that MMP-2 also cleaves the endothelium-derived peptide big endothelin-1, ET-1[1-38] and yields the novel vasoconstrictor ET-1[1-32]. We therefore investigated the effects of MMP-2 inhibitors as potential vasodilators. MMP inhibition with ortho-phenanthroline (0.3 to 30 micromol/L) induced vasorelaxation of isolated rat mesenteric arteries (maximum of relaxation=74.5+/-27.6% at 30 micromol/L). However, phosphoramidon (0.3 to 30 micromol/L), which inhibits some metalloenzymes, but not MMP-2, did not dilate the arteries. Selective inhibition of endogenous MMP-2 with the novel tissue-permeable cyclic peptide CTTHWGFTLC (CTT, 10 micromol/L) also caused vasorelaxation (by 85+/-6%), whereas STTHWGFTLS (10 micromol/L), an inactive CTT analogue, did not dilate the arteries. Interestingly, the vasorelaxation that results from MMP-2 inhibition was endothelium-independent. Thus, we examined whether MMP-2 acted on peptides derived from the smooth muscle or the perivascular nerves. Recombinant human MMP-2 cleaved calcitonin gene-related peptide (CGRP) specifically at the Gly(14)-Leu(15) peptide bond and reduced the vasodilatory potency of CGRP by 20-fold. Inhibition of MMP-2 increased the amount of intact CGRP in arteries and enhanced vasorelaxation induced by anandamide, which stimulates CGRP release. Vasorelaxation in response to MMP-2 inhibition was abolished by CGRP[8-37], a selective CGRP receptor antagonist, and by capsaicin, which depletes arterial perivascular nerves of CGRP. We conclude that vascular MMP-2 cleaves endogenous CGRP and promotes vasoconstriction. These data suggest a novel mechanism of regulating the vasoactive and, possibly, the neurohormonal actions of CGRP and establish MMP-2 as a modulator of vascular function.

Identification of novel prostate-specific antigen-binding peptides modulating its enzyme activity

Prostate-specific antigen (PSA) is a serine protease with highly prostate-specific expression. Measurement of PSA in serum is widely used for diagnosis and monitoring of prostate cancer. PSA dissolves the seminal gel forming after ejaculation. It has been suggested to mediate invasion and metastasis of prostate cancer but also to exert antiangiogenic activity. We have identified peptides specific for PSA by screening cyclic phage display peptide libraries. PSA-binding peptides were isolated from four different libraries and produced as a fusion protein with glutathione S-transferase (GST). The phage and fusion proteins were shown to bind to PSA specifically as indicated by lack of binding to other serine proteinases. A peptide with four cysteines showed the highest affinity for PSA. Zn2+, an inhibitor of PSA activity, increased the affinity of the peptides to PSA. The binding specificity was characterized by cross-inhibition using monoclonal anti-PSA antibodies of known epitope specificities. The peptides bound to the same region as mAbs specific for free PSA indicating that they bind close to the active site of the enzyme. The peptides enhanced the enzyme activity of PSA against a chromogenic substrate. These results show that peptides binding to PSA and modulating its enzyme activity can be developed by phage display technique. The peptides have the potential to be used for identification of PSA variants and for imaging and targeting of prostatic tumors.

Targeting of phage display vectors to mammalian cells

Phage display libraries offer a strategy to isolate peptide ligands to target proteins and to define potential interaction sites between proteins. Recent studies have indicated a novel utility for phage display in that bacteriophage engineered to express peptide ligands to specific cell surface receptors are internalized by mammalian cells. Thus, reporter genes such as green fluorescent protein and lacZ harbored in the phage genome can be delivered to mammalian cells using targeting peptides displayed on the surface of phage. There is also the possibility to generate novel types of peptide libraries expressed intracellularly using a phage capable of inducing expression of its coding genes in human cells.

Down-regulation of trypsinogen-2 expression by chemically modified tetracyclines: association with reduced cancer cell migration

Many types of human tumor express trypsinogen-2, which may be a significant factor in the activation of pro-MMPs and the invasiveness of tumors. Prevention of trypsinogen-2 expression in cancer cells might be of benefit in cancer therapy. We describe here chemicals capable of down-regulating the expression of trypsinogen-2. Doxycycline (DOXY) and chemically modified tetracyclines (CMTs), previously known as inhibitors of the matrix metalloproteinase (MMP)-dependent proteinase cascade, down-regulated the mRNA and protein expression of trypsinogen-2 by COLO-205 human colon adenocarcinoma cells at therapeutically attainable concentrations (0. 1 to 1.0 microM). DOXY specifically inhibited the activation of pro-MMP-9 and cell migration induced by enteropeptidase, a specific activator of trypsinogen. Pro-MMP-9 activation and cell migration were also inhibited by tumor-associated trypsin inhibitor (TATI), which is a highly specific inhibitor of trypsin. CMT-3 as well as CMT-5 also inhibited cell migration, but an effect on the enteropeptidase-enhanced activation of pro-MMP-9 was not observed. Our results indicate that CMTs, DOXY and TATI inhibit cancer cell migration by down-regulating trypsinogen-2 expression or activity. Inhibition of trypsinogen-2 expression may represent a mechanism contributing to the ability of CMTs to suppress the pericellular proteolytic activity of some tumors.

Aminopeptidase N is a receptor for tumor-homing peptides and a target for inhibiting angiogenesis

Phage that display a surface peptide with the NGR sequence motif home selectively to tumor vasculature in vivo. A drug coupled to an NGR peptide has more potent antitumor effects than the free drug [W. Arap et al., Science (Washington DC), 279: 377-380, 1998]. We show here that the receptor for the NGR peptides in tumor vasculature is aminopeptidase N (APN; also called CD13). NGR phage specifically bound to immunocaptured APN and to cells engineered to express APN on their surface. Antibodies against APN inhibited in vivo tumor homing by the NGR phage. Immunohistochemical staining showed that APN expression is up-regulated in endothelial cells within mouse and human tumors. In another tissue that undergoes angiogenesis, corpus luteum, blood vessels also expressed APN, but APN was not detected in blood vessels of various other normal tissues stained under the same conditions. APN antagonists specifically inhibited angiogenesis in chorioallantoic membranes and in the retina and suppressed tumor growth. Thus, APN is involved in angiogenesis and can serve as a target for delivering drugs into tumors and for inhibiting angiogenesis.