Restoration of membrane TNF-like activity by cell surface targeting and matrix metalloproteinase-mediated processing of a TNF prodrug.

Tumor necrosis factor (TNF) prodrugs are fusion proteins comprised of an N-terminal single-chain antibody variable fragment (scFv) targeting a TNF effector and a C-terminal TNF receptor (TNFR)1-derived inhibitor module. Introduction of matrix metalloproteinase (MMP)-2 recognition motifs between TNF and the TNFR1 fragment allowed activation by recombinant MMP-2 and MMP-expressing HT1080 cells. Processing by endogeneous MMPs required specific membrane binding of the TNF prodrug via the targeting scFv, ensuring strictly antigen-dependent activation. Interestingly, TNF bioactivity of the processed prodrug was approximately 1000-fold higher upon scFv-mediated targeting, and signaled juxtatropic cell death also to antigen-negative cells. Microscopical analyses of TNFR2 clustering and TNF receptor-associated factor 2 recruitment at contact sites to adjacent cells revealed the formation of stable TNFR complexes by target-bound, processed prodrug, resembling the increased signal capacity of natural, membrane-expressed TNF. MMP-2-sensitive TNF prodrugs represent novel cytokine-based reagents for targeted cancer therapy, which should be exploitable for MMP-overexpressing tumors.

A highly sensitive model for quantification of in vivo tumor angiogenesis induced by alginate-encapsulated tumor cells.

A remarkable approach to a specific tumor angiogenesis model in vivo is the use of alginate implants encapsulating tumor cells. However, this previously reported approach has often been questioned because of doubts regarding the relevance of hemoglobin at the alginate implant as a parameter of vascularization. In the present investigation, we examined whether or not the use of the blood pool agents FITC-dextran of high molecular weight would significantly improve the determination of vascularization at the alginate implant. In our experiments, we found a rapid distribution of FITC-dextran within the blood circulation of mice after i.v. bolus injection. The amount of FITC-dextran within alginate implants strongly correlated with the number of LL2 carcinoma cells or B16/F10 cells encapsulated. Even a low number of 10(3) cells per alginate implant led to a significantly increased accumulation of FITC-dextran. A more than 10-fold stimulation above that of controls was found with alginate implants containing 10(4) LL2 or B16/F10 tumor cells. Using the investigational compound AGM-1470 in different treatment schedules, we found that quantification of alginate implant anglogenesis with FITC-dextran is a sensitive method for the determination of angiogenesis inhibition. In conclusion, our results demonstrated that the use of FITC-dextran enables highly sensitive, quantitative measurement of blood vessel formation by alginate implants.

Biochemical and functional characterization of aminopeptidase N expressed by human melanoma cells.

A cell surface protein expressed on melanoma cells, but not on normal melanocytes, was biochemically and functionally characterized. Microsequencing of the M(r) 143,000 affinity-purified protein revealed amino acid sequence identity to aminopeptidase N (EC 3.4.11.2). In situ expression, indirect immunofluorescence, and Western blotting demonstrated that aminopeptidase N is tightly associated with extracellular matrix components. A specific polyclonal antiserum and the competitive inhibitors of aminopeptidase N, bestatin and amastatin, inhibited invasion of an aminopeptidase N-expressing metastatic melanoma cell line through the reconstituted basement membrane Matrigel in a dose-dependent manner. In vitro digestion of Matrigel with affinity-purified aminopeptidase N revealed an enzyme-sensitive M(r) 160,000 protein. These experiments suggest a role for aminopeptidase N in melanoma invasion of basement membranes.

Signaling-inactive epidermal growth factor receptor/ligand complexes in intact carcinoma cells by quinazoline tyrosine kinase inhibitors.

Several inhibitors of EGF receptor (EGFR) tyrosine kinase activity have been developed that compete with ATP at its binding site such as the quinazolines PD 153035 and ZD 1839 or the 4,5-dianilino-phthalimides DAPH1 and DAPH2. When tested on human A431 cells, the quinazolines completely blocked EGF-induced receptor phosphorylation at 100 nM, whereas it was inhibited by DAPH1 and DAPH2 by only 20% at 3 microM. Quinazoline-treated A431 as well as tumor cells expressing less EGFR (A549, MDA MB 231, and T47D) bound 3- to 6-fold more (125)I-labeled EGF than untreated intact control cells. Scatchard analysis revealed the disappearance of low- and high-affinity EGFR on A431 cells upon PD 153035 treatment. A single receptor class of intermediate ligand binding affinity emerged and its number corresponded to the sum of the two classes. DAPH1 and DAPH2 did not change ligand binding properties of EGFR. PD 153035 exerted the most potent effects on EGF binding to A431 or on inhibiting EGF-stimulated growth of rat MTLn3 cells at low ligand concentrations. Cross-linking of EGFR on PD 153035-treated A431 cells indicated the formation of inactive dimers that further increased upon addition of EGF. Chemical cross-linking of (125)I-labeled EGF to PD 153035-treated A431 cells revealed increased binding to monomeric and dimeric EGFR. Thus, the quinazolines sequestered EGFR plus the ligand into inactive receptor/ligand complexes. This novel mode of action of quinazoline tyrosine kinase inhibitors may be the basis for their extraordinary potency especially in conditions when the ligand is present in limiting amounts.

Two independent mechanisms essential for tumor angiogenesis: inhibition of human melanoma xenograft growth by interfering with either the vascular endothelial growth factor receptor pathway or the Tie-2 pathway.

Protein ligands and receptor tyrosine kinases that specifically regulate endothelial cell function are mainly involved in physiological as well as in disease-related angiogenesis. These ligand/receptor systems include the vascular endothelial growth factor (VEGF) and the angiopoietin (Ang) families, and their receptors, the VEGF receptor family and the tyrosine kinase with immunoglobulin-like and epidermal growth factor homology domains (Tie) family. In the present study, the contribution of these endothelium-specific ligand/receptor systems to tumor angiogenesis was evaluated. A375v human melanoma cells, which express at least the angiogenic growth factors VEGF, VEGF-C, and Ang-1, were stably transfected to overexpress the extracellular ligand-binding domains of the endothelium-specific receptor tyrosine kinases fms-like tyrosine kinase-1 (Flt-1), Flt-4, Tie-1, and Tie-2, respectively. In vitro proliferation and colony formation assays confirmed that expression of the extracellular receptor domains inhibited neither tumor cell mitogenesis nor the ability to produce anchorage-independent growth. Nude mouse xenografts revealed that interference with either the VEGF receptor pathway or the Tie-2 pathway resulted in a significant inhibition of tumor growth and tumor angiogenesis. In contrast, interference with the Flt-4 pathway or the Tie-1 pathway was without significant effect. Our results show that both the VEGF receptor pathway and the Tie-2 pathway are essential for A375v melanoma xenograft growth. The inhibition of the VEGF receptor pathway cannot be compensated by the Tie-2 pathway, nor vice versa. These findings suggest that the VEGF receptor pathway and the Tie-2 pathway have to be considered as two independent mediators essential for the process of in vivo angiogenesis.

Topical calcitriol enhances normal hair regrowth but does not prevent chemotherapy-induced alopecia in mice.

Using a murine model that mimics chemotherapy-induced alopecia (CIA) in humans particularly well, we show here that in contrast to previously reported CIA-protective effects in neonatal rats, topical calcitriol does not prevent CIA in adolescent mice but enhances the regrowth of normally pigmented hair shafts. When, prior to injecting 1 X 120 mg/kg cyclophosphamide i.p., 0.2 microg calcitriol or vehicle alone were administered topically to the back skin of C57BL/6 mice with all hair follicles in anagen, no significant macroscopic differences in the onset and severity of CIA were seen. However, hair shaft regrowth after CIA, which is often retarded and patchy, thus displaying severe and sometimes persistent pigmentation disorders, was significantly accelerated, enhanced, and qualitatively improved in test compared with control mice. Histomorphometric analysis suggests that this is related to the fact that calcitriol-pretreated follicles favor the "dystrophic catagen pathway" of response to chemical injury, ie., a follicular repair strategy allowing for the unusually fast reconstruction of a new, undamaged anagen hair bulb. Thus, it may be unrealistic to expect that topical calcitriol can prevent human CIA, but topical calcitriols may well enhance the regrowth of a normal hair coat.

Establishment and characterization of a cell line (Wa-2) derived from an extrarenal rhabdoid tumor.

A new human cell line (Wa-2) derived from an extrarenal rhabdoid tumor has been established. The cell line grows as a monolayer consisting of round- and spindle-shaped cells. Injection of cells into nude mice results in the growth of solid tumors within 2 wk of inoculation. These solid tumors have the microscopic appearance similar to that of the original tumor from which the cell line was derived. Moreover, the tumor cells have all the features of rhabdoid tumors, including the intracytoplasmatic hyaline globules, large prominent nucleoli, and inclusion bodies made up of whorls of fibrillary material. Transplanted tumor cells stain positive for vimentin, cytokeratin, actin, and desmin and negative for myoglobin and neuron-specific enolase. Karyotyping of the cell line at different passages and cells derived from the transplant tumors consistently revealed a diploid number of chromosomes with a reciprocal translocation between chromosomes 18 and 22 [t(18;22) (q21;p11.2)]. In fibroblasts derived from the patient, no translocation could be found. Culturing the cells in the presence of 1-beta-D-arabinofuranosylcytosine induces differentiation, characterized by the outgrowth of neuron-like processes and the morphological appearance of cells similar to neuroblasts. Southern blot analysis showed no amplification of the N-myc oncogene. Since no published cell line derived from rhabdoid tumors exists, this cell line should be helpful to further elucidate the biology and histological origin of the malignant rhabdoid tumor.

PTK787/ZK 222584, a novel and potent inhibitor of vascular endothelial growth factor receptor tyrosine kinases, impairs vascular endothelial growth factor-induced responses and tumor growth after oral administration.

PTK787/ZK 222584 (1-[4-chloroanilino]-4-[4-pyridylmethyl] phthalazine succinate) is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, active in the submicromolar range. It also inhibits other class III kinases, such as the platelet-derived growth factor (PDGF) receptor beta tyrosine kinase, c-Kit, and c-Fms, but at higher concentrations. It is not active against kinases from other receptor families, such as epidermal growth factor receptor, fibroblast growth factor receptor-1, c-Met, and Tie-2, or intracellular kinases such as c-Src, c-Abl, and protein kinase C-alpha. PTK787/ZK 222584 inhibits VEGF-induced autophosphorylation of kinase insert domain-containing receptor (KDR), endothelial cell proliferation, migration, and survival in the nanomolar range in cell-based assays. In concentrations up to 1 microM, PTK787/ZK 222584 does not have any cytotoxic or antiproliferative effect on cells that do not express VEGF receptors. After oral dosing (50 mg/kg) to mice, plasma concentrations of PTK787/ZK 222584 remain above 1 microM for more than 8 h. PTK787/ZK 222584 induces dose-dependent inhibition of VEGF and PDGF-induced angiogenesis in a growth factor implant model, as well as a tumor cell-driven angiogenesis model after once-daily oral dosing (25-100 mg/kg). In the same dose range, it also inhibits the growth of several human carcinomas, grown s.c. in nude mice, as well as a murine renal carcinoma and its metastases in a syngeneic, orthotopic model. Histological examination of tumors revealed inhibition of microvessel formation in the interior of the tumor. PTK787/ZK 222584 is very well tolerated and does not impair wound healing. It also does not have any significant effects on circulating blood cells or bone marrow leukocytes as a single agent or impair hematopoetic recovery after concomitant cytotoxic anti-cancer agent challenge. This novel compound has therapeutic potential for the treatment of solid tumors and other diseases where angiogenesis plays an important role.

Antiangiogenic chemotherapeutic agents: characterization in comparison to their tumor growth inhibition in human renal cell carcinoma models.

The mechanism of action of anticancer chemotherapeutic agents is mainly thought to be due to a direct inhibition of tumor cell proliferation. The enhanced endothelial cell proliferation rate in tumor specimens raised the question of whether therapeutic effects of chemotherapeutic agents might be at least partially attributed to inhibition of tumor angiogenesis. In the present study, we investigated the potential effects of chemotherapeutic agents on human renal carcinoma angiogenesis with the alginate implantation model in mice. For the first time, we also compared results from the angiogenesis model with the inhibitory effects on growth of s.c. xenografts in nude mice. Vincristine and bleomycin exerted strong inhibition of tumor angiogenesis in both carcinoma lines close to the level of the standard antiangiogenic agent O-chloroacetyl-carbamyl-fumagillol (AGM-1470; T/C 22%). Adriamycin reduced angiogenesis of Caki-2 cells (T/C 33%) but had no effect on Caki-1 angiogenesis (T/C 137%). Etoposide and 5-fluorouracil reduced Caki-1 tumor angiogenesis but had no effect on Caki-2. Despite antiangiogenic effects in both carcinoma lines, vincristine, bleomycin, and AGM-1470 significantly reduced only the growth of fast-growing Caki-1 s.c. xenografts but not the slow-growing Caki-2. Antivascular effects by bleomycin and AGM-1470 were also shown by a decrease of microvessel density in nude mouse xenografts. Our findings suggest that chemotherapeutic agents may exert inhibition of tumor angiogenesis, which could be exploitable by combination therapy of fast-growing tumors. The resistance of the slow-growing Caki-2 carcinoma against acute angiogenesis inhibition indicates a need for well-tolerated angiogenesis inhibitors. Our results also suggest the use of fast-growing s.c. xenografts for demonstrating growth inhibition by antiangiogenic compounds. Further characterization of antiangiogenic compounds considered for clinical application should, however, have its focus on slow-growing tumors, which are not accessible for most therapeutic strategies.

Selective, efficient modulation of activated CD4+ αßT cells by the novel humanized antibody GZ-αßTCR targeting human αßTCR.

Allograft rejection and immunosuppression are two major issues in transplantation medicine. The specific targeting of alloreactive T cells, the initiators and promoters of allograft rejection, would be a promising strategy to reduce unwanted T-cell responses and side effects of lifelong immunosuppression. The novel humanized monoclonal antibody GZ-αßTCR, specific for the human αßT-cell receptor, was tested in vitro and in vivo for its specificity and efficacy to modulate the αßT-cell compartment. GZ-αßTCR moderately induced apoptosis in resting αßT cells in vitro, an effect considerably amplified in activated T cells. A single dose of GZ-αßTCR significantly reduced human CD45(+)CD3(+) T cells in vivo, with a preferential modulation of CD4(+) αßT cells. Importantly, naive T cells, the T-cell subset from which alloreactivity emanates, were significantly reduced. Simultaneously, a significant, compensatory increase of γδ T cells was observed in vitro and in vivo in both humanized mouse models examined. GZ-αßTCR did not induce cytokines and was well tolerated. Thus, specificity and high efficacy make GZ-αßTCR a powerful tool to selectively eliminate putatively detrimental T-cell subsets, a major goal in transplantation medicine. At the same time, GZ-αßTCR spares γδ and natural killer cells, thus leaving the recipient's immune system competent for cell-mediated immunoregulation and cell-mediated immunity.

Reduction of intrafollicular apoptosis in chemotherapy-induced alopecia by topical calcitriol-analogs.

Chemotherapy-induced alopecia is thought to result from cytotoxic and apoptosis-related damage to the hair follicle. This study was designed to confirm whether keratinocyte apoptosis is indeed induced in growing (= anagen) hair follicles of C57 BL/6 mice after the injection of cyclophosphamide, using improved methods for histologic detection of apoptotic cells in murine skin. More importantly, we asked whether topical calcitriol-analogs are able to modulate cyclophosphamide-induced apoptosis in vivo, because there are conflicting reports on the effects of calcitriols on apoptosis in vitro. Anagen was induced in telogen mice on day 0 by depilation. Starting on day 5 post-depilation, the back skin of mice was topically treated with either 0.2 microg 1,25-dihydroxyvitamin D3, 2.0 microg calcipotriol, 0.02 microg KH 1060, or vehicle (ethanol) only. On the last day of treatment (i.e., day 9 post-depilation), all mice received 150 mg cyclophosphamide i.p. per kg as a single dose to induce alopecia, or vehicle (aqua dist.). Analysis of the treated skin by in situ-end labeling (using a modified terminal UTP nucleotide end labeling technique suitable for murine skin), by Hoechst 33342 stain, and by DNA electrophoresis on days 10 and 14, revealed the induction of massive apoptosis in cyclophosphamide-treated anagen hair bulbs, which was most prominent on day 10, whereas controls showed no follicular apoptosis. The calcitriol-pretreated groups demonstrated a significant reduction of apoptosis, with a maximal inhibition seen on day 14. This confirms that cyclophosphamide indeed induces massive keratinocyte apoptosis in anagen hair follicles, and provides evidence that topical calcitriol-analogs can suppress epithelial cell apoptosis in vivo. The mouse model employed here offers an excellent tool for dissecting the as yet poorly understood controls of keratinocyte apoptosis in situ and its pharmacologic manipulation.

Progesterone withdrawal up-regulates vascular endothelial growth factor receptor type 2 in the superficial zone stroma of the human and macaque endometrium: potential relevance to menstruation.

Several reports indicate that vascular endothelial growth factor (VEGF) expression is increased in endometrial glands and stroma during the menstrual phase in the human endometrium. Here we report that VEGF receptor type 2 (KDR), normally expressed only in the vascular endothelium, was dramatically up-regulated in the stromal cells of the superficial endometrial zones during the premenstrual phase in both human and macaque endometrium. This increase was detectable by Northern analysis, in situ hybridization, and immunocytochemistry and was cell specific, zone specific, cycle phase specific, and VEGF receptor type specific. That is, it only occurred during the premenstrual/menstrual phase, did not occur in glandular epithelium, endothelium, or stromal cells of the deepest endometrial zones, and was not observed for VEGF receptor type 1. The upregulation of stromal KDR was induced by progesterone (P) withdrawal in both women and macaques, and adding back P 24 h after P withdrawal in macaques blocked stromal, but not vascular, endothelial KDR expression. Promatrix metalloproteinase-1 (MMP-1) was coordinately up-regulated in the same stromal cell population by P withdrawal. Because of reports that VEGF can enhance MMP expression, we hypothesize that VEGF-KDR interactions may influence MMP expression in the superficial zones of the primate endometrium during the premenstrual phase, and that these interactions play a role in the induction of menstruation.

Expression of LDL receptor on tumor cells induced by growth factors.

For the determination of LDL receptor expression on living human cells two monoclonal antibodies specific for the extracellular domain of LDL receptor were established using affinity-purified LDL receptor and carrier-conjugated LDL receptor peptide 163-174 as immunizing antigens. The 125I-labeled antibodies were used to quantify increases in LDL receptor expression on human cells grown in the presence of increasing concentrations of various growth factors. Growth factor-mediated increase of LDL receptor expression was entirely different in various cell lines with respect to a distinct growth factor and for different growth factors when tested with one and the same cell line. An increased LDL receptor expression was observed on A431 epidermoid carcinoma cells of the vulva in the presence of epidermal growth factor (EGF) or insulin but not with platelet-derived growth factor (PDGF), on HUV-EC primary endothelial cells in the presence of insulin or PDGF but not with EGF, and on MRC-5 diploid fetal lung cells only in the presence of PDGF. HEP-3B hepatoma cells did not respond to any of the three growth factors essentially maintaining the original level of LDL receptor expression.

Novel antibodies directed against the extracellular domain of the human VEGF-receptor type II.

Vascular endothelial cell growth factor (VEGF) plays a pivotal role in the regulation of angiogenesis by binding to its cognate receptor molecule type II (VEGFr-II, KDR). VEGFr-II is an endothelial cell-specific transmembrane tyrosine kinase important for vascular endothelial cell development and differentiation during embryogenesis, angiogenic processes under physiological conditions, and various diseases. An increasing number of reports indicate that VEGF/VEGFr-II also play a fundamental role for tumor angiogenesis. We present the generation and in vitro characterization of the monoclonal antibodies 2-7-9 and 2-10-1. Both antibodies are highly specific for VEGFr-II as demonstrated by Western blotting and immunoprecipitation. MAbs 2-10-1 and 2-7-9 bind to a disulphide bridge-stabilized epitope within domains 6 and 7 of the human VEGFr-II with an affinity of 8 and 80 nM, respectively. Furthermore, the antibodies are suitable for immunohistochemistry and ELISA techniques. Because both antibodies recognize their epitope on living cells, they also have the potential for drug targeting and diagnostic purposes.

Tumor progression, biology, and host response in melanoma.

Malignant melanoma has provided an excellent model system for studying crucial events in human tumor development and progression. Important components discussed here include the independence of melanoma cells from exogenous growth factors due to self-stimulation and the altered adhesive properties and invasive capacity of these cells.

Involvement of hepatocyte growth factor/scatter factor and met receptor signaling in hair follicle morphogenesis and cycling.

HGF/SF and its receptor (Met) are principal mediators of mesenchymal-epithelial interactions in several different systems and have recently been implicated in the control of hair follicle (HF) growth. We have studied their expression patterns during HF morphogenesis and cycling in C57BL/6 mice, whereas functional hair growth effects of HGF/SF were assessed in vivo by analysis of transgenic mice and in skin organ culture. In normal mouse skin, follicular expression of HGF/SF and Met was strikingly localized: HGF/SF was found only in the HF mesenchyme (dermal papilla fibroblasts) and Met in the neighboring hair bulb keratinocytes. Both HGF/SF and Met expression peaked during the initial phases of HF morphogenesis, the stage of active hair growth (early and mid anagen), and during the apoptosis-driven HF regression (catagen). Met+ cells in the regressing epithelial strand appeared to be protected from undergoing apoptosis. Compared to wild-type controls, transgenic mice overexpressing HGF/SF under the control of the MT-1 promoter had twice as many developing HF and displayed accelerated HF development on postnatal day 3. They also showed significant catagen retardation on P17. In organ culture and in vivo, HGF/SF i.c. resulted in a significant catagen retardation. These results demonstrate an important role of HGF/SF and Met in murine hair growth control and suggest that Met-mediated signaling might be exploited for therapeutic manipulation of human hair growth disorders.-Lindner, G., Menrad, A., Gherardi, E., Merlino, G., Welker, P., Handjiski, B., Roloff, B., Paus, R. Involvement of hepatocyte growth factor/scatter factor and Met receptor signaling in hair follicle morphogenesis and cycling.