P–195 The influence of hormones and initial cell number on the size of self-assembled embryo-like structures

Study question

Do hormonal treatments and initial cell number influence the formation of embryo-like structures (ELS) during their development in regard to size?

Summary answer

The chosen initial cell number for ELS-assembly seems to influence the ELS size only until day 4, while hormones affect embryo size throughout their development.

What is known already

The initial cell number is an important parameter for the development of ELS, which might help to better understand how embryos regulate their size. Previous studies on differently sized natural murine embryos revealed that an initial difference in size at the early stage is compensated until E6.75. Normal-size embryos experience an increased mitotic activity before E6.75, whereas larger sized embryos show an increased apoptotic activity, indicating an important control point of cell turnover by adapting mitotic activity and cell survival. Embryo development is strongly dependent on appropriate β-estradiol and progesterone levels.

Study design, size, duration

The first set of experiments interrogated the influence of initial cell number (two conditions) on the size of formed ELS during the first 3 days (D1–3). The second set included two different hormonal treatments and the two conditions of initial cell number (the same as in the first experiments) generating four different groups. For each day one Aggrewell (generating 1200 ELS/well) per condition was harvested. Experiments were repeated at least three times.

Participants/materials, setting, methods

ELS are generated by self-assembly in microwell-chamber plates combining embryonic stem cells, trophoblast stem cells and extraembryonic endoderm stem cells. Cells were cultured with and without addition of β-estradiol and progesterone, starting with different initial cell numbers (106 vs. 42 cells/ELS). ELS were harvested, stained, and at least 40 randomly picked ELS per condition were measured and statistically analyzed with Two-way ANOVA and Tukey’s multiple comparison test. Results show the average area ± SD.

Main results and the role of chance

The results show a continuous increase in the size of ELS during the first three days of cultivation, with significant lower values (on D1-D3) when ELS were assembled from 42 initial cells (D1: 224.1±87.7 μm²; D3: 674.0± 84.4 μm²) compared to ELS formed with 106 initial cells (D1: 467.1±224.1 μm²; D3: 1275.0±348.0 μm²). Onward on the course of self-assembly, ELS with 42 initial cells were still smaller on D4 (1465.7±657.6 μm²) compared to ELS formed with 106 initial cells (2028.6±522.4 μm²). However, these differences could not be measured on D5 (106 initial cells: 1892.2±603.7 μm²; 42 initial cells: 1855±448.5 μm²), D6 (106 initial cells: 2143.3±622.1 μm²; 42 initial cells: 1788.4±585.5 μm²) and D7 (106 initial cells: 2146.7±628.1 μm²; 42 initial cells: 2319.5±778.8 μm²). Differences between the conditions with and without hormonal treatments (HT) could also be detected especially when ELS were generated with 42 cells: on D4 ELS with HT (1730.4±852.4 μm²) were significantly larger than without hormones (1201.2±462.9 μm²). In contrast, on D7 HT influenced the size of ELS distinctly depending on the initial cell number (42 cells: 1989.2±558.3 μm² with HT vs. 2649.7±999.4 μm² without HT; 106 cells: 2334.9±770.2μm² with HT vs. 1958.6±486.1 μm² without HT).

Limitations, reasons for caution

An even cell distribution is crucial for reproducible ELS-formation. Unfortunately, the used techniques for cell seeding led to an uneven distribution within the microwells. Moreover, different orientation of ELS during the size assessment might be an additional reason for the high variance of ELS size within one condition.

Wider implications of the findings: Even if the results seem to be in accordance with the observations made with natural embryos regarding compensation of size until E6.75, additional experiments need to be conducted. Further investigations should be carried out by testing different culture formats to obtain a more even cell distribution during the cultivation.

Trial registration number

Not applicable

Molecular basis of the evolution of alternative tyrosine biosynthetic routes in plants

L-Tyrosine (Tyr) is essential for protein synthesis and is a precursor of numerous specialized metabolites crucial for plant and human health. Tyr can be synthesized via two alternative routes by different key regulatory TyrA family enzymes, prephenate dehydrogenase (PDH, also known as TyrA_p) or arogenate dehydrogenase (ADH, also known as TyrA_a), representing a unique divergence of primary metabolic pathways. The molecular foundation underlying the evolution of these alternative Tyr pathways is currently unknown. Here we characterized recently diverged plant PDH and ADH enzymes, obtained the X-ray crystal structure of soybean PDH, and identified a single amino acid residue that defines TyrA substrate specificity and regulation. Structures of mutated PDHs co-crystallized with Tyr indicate that substitutions of Asn222 confer ADH activity and Tyr sensitivity. Reciprocal mutagenesis of the corresponding residue in divergent plant ADHs further introduced PDH activity and relaxed Tyr sensitivity, highlighting the critical role of this residue in TyrA substrate specificity that underlies the evolution of alternative Tyr biosynthetic pathways in plants.

The target cell of transformation is distinct from the leukemia stem cell in murine CALM/AF10 leukemia models

The CALM/AF10 fusion gene is found in various hematological malignancies including acute myeloid leukemia (AML), T-cell acute lymphoblastic leukemia and malignant lymphoma. We have previously identified the leukemia stem cell (LSC) in a CALM/AF10-driven murine bone marrow transplant AML model as B220+ lymphoid cells with B-cell characteristics. To identify the target cell for leukemic transformation or 'cell of origin of leukemia' (COL) in non-disturbed steady-state hematopoiesis, we inserted the CALM/AF10 fusion gene preceded by a loxP-flanked transcriptional stop cassette into the Rosa26 locus. Vav-Cre-induced panhematopoietic expression of the CALM/AF10 fusion gene led to acute leukemia with a median latency of 12 months. Mice expressing CALM/AF10 in the B-lymphoid compartment using Mb1-Cre or CD19-Cre inducer lines did not develop leukemia. Leukemias had a predominantly myeloid phenotype but showed coexpression of the B-cell marker B220, and had clonal B-cell receptor rearrangements. Using whole-exome sequencing, we identified an average of two to three additional mutations per leukemia, including activating mutations in known oncogenes such as FLT3 and PTPN11. Our results show that the COL for CALM/AF10 leukemia is a stem or early progenitor cell and not a cell of B-cell lineage with a phenotype similar to that of the LSC in CALM/AF10+ leukemia.

Genetic dissection of IGF1-dependent and -independent effects of permanent GH excess on postnatal growth and organ pathology of mice

To study insulin-like growth factor 1 (IGF1)-independent effects of permanent growth hormone (GH) excess on body and organ growth and pathology in vivo, hemizygous bovine GH transgenic mice with homozygous disruption of the Igf1 gene (Igf1(-/-)/GH) were generated, and examined in comparison to Igf1(-/-), Igf1(+/-), wild-type (WT), Igf1(+/-)/GH, and GH mice. GH mice and Igf1(+/-)/GH mice showed increased serum IGF1 levels and the well-known giant-phenotype of GH transgenic mice. In contrast, the typical dwarf-phenotype of Igf1(-/-) mice was only slightly ameliorated in Igf1(-/-)/GH mice. Similar to GH mice, Igf1(-/-)/GH mice displayed hepatocellular hypertrophy, glomerulosclerosis, and reduced volumes of acidophilic cells in the pituitary gland. However, GH excess associated skin lesions of male GH mice were not observed in Igf1(-/-)/GH mice. Therefore, development of GH excess induced liver-, kidney-, and pituitary gland-alterations in GH transgenic mice is independent of IGF1 whereas GH stimulated body growth depends on IGF1.

MicroRNAs as novel players in skin development, homeostasis and disease

MicroRNAs (miRNAs) are a group of newly discovered small (∼19-24 nucleotides), noncoding RNAs that modulate gene expression by interacting with the 3' untranslated region of the corresponding target gene messenger RNA (mRNA). miRNAs have been estimated to regulate more than one-third of protein-encoding mRNAs. As a consequence, cellular protein expression and a large number of biological processes are influenced by miRNA-mediated post-transcriptional regulation of gene expression. The severe phenotype of mice lacking key enzymes of the miRNA biogenesis pathway (Dgcr8 and Dicer) in the skin confirmed the essential function of miRNAs in this tissue. In addition, a growing number of reports has identified miRNAs as regulators of the morphogenesis and homeostasis of the skin and its appendages, and miRNA deregulation was shown to be associated or even causally related to several skin diseases. Profiling studies have identified numerous differentially regulated miRNAs associated with physiological (e.g. keratinocyte differentiation) and pathological (e.g. psoriasis, melanoma) processes. These data bear enormous potential for further studies. Because of the easy accessibility of the skin, it is plausible to anticipate that, once efficient and safe methods for the topical delivery of substances mimicking or modulating miRNA activity become available, skin diseases will be among the first to be approached with miRNA-based therapies. This review article gives a short introduction to miRNA biology and summarizes and discusses existing evidence for a role of these molecules in the skin.

Canine embryonic stem cells: state of the art

Embryonic stem cells (ESCs) are permanent cell lines that can be maintained in a pluripotent, undifferentiated state. Appropriate environmental stimuli can cause them to differentiate into cell types of all three germ layers both in vitro and in vivo. Embryonic stem cells bear many opportunities for clinical applications in tissue engineering and regenerative medicine. Whereas most of our knowledge on the biology and technology of ESCs is derived from studies with mouse cells, large animal models mimicking important aspects of human anatomy, physiology, and pathology more closely than mouse models are urgently needed for studies evaluating the safety and efficacy of cell therapies. The dog is an excellent model for studying human diseases, and the availability of canine ESCs would open new possibilities for this model in biomedical research. In addition, canine ESCs could be useful for the development of cell-based approaches for the treatment of dogs. Here, we discuss the features of recently reported canine embryo-derived cells and their potential applications in basic and translational biomedical research.

Betacellulin overexpression in transgenic mice improves glucose tolerance and enhances insulin secretion by isolated islets in vitro

Betacellulin (BTC), a ligand of the epidermal growth factor receptor, has been shown to promote growth and differentiation of pancreatic beta-cells and to improve glucose metabolism in experimental diabetic rodent models. We employed transgenic mice (BTC-tg) to investigate the effects of long-term BTC overabundance on islet structure and glucose metabolism. Expression of BTC is increased in transgenic islets, which show normal structure and distribution of the different endocrine cell types, without pathological alterations. BTC-tg mice exhibit lower fasted glucose levels and improved glucose tolerance associated with increased glucose-induced insulin secretion. Surprisingly, quantitative stereological analyses revealed that, in spite of increased cell proliferation, the islet and beta-cell volumes were unchanged in BTC-tg mice, suggesting enhanced cell turnover. Insulin secretion in vitro was significantly higher in transgenic islets in medium containing high glucose (11.2 or 16.7mM) as compared to control islets. Our results demonstrate that long-term BTC overabundance does not alter pancreatic islet structure and beta-cell mass, but enhances glucose-induced insulin secretion in vivo as well as in vitro.

Insulin-like growth factor-binding protein-4 inhibits growth of the thymus in transgenic mice

Numerous in vitro studies have demonstrated that IGF-binding protein (IGFBP)-4 is a consistent inhibitor of IGF actions. In order to investigate the functions of IGFBP-4 in vivo, transgenic mice were generated by microinjection of a transgene, in which the murine Igfbp4 cDNA is driven by the H-2K(b) promoter, and followed by a splicing cassette and polyadenylation signal of the human beta-globin gene. Transgene mRNA was expressed ubiquitously, and elevated IGFBP-4 protein was detected in the spleen, thymus, kidney and lung of transgenic mice. The activities of serum IGFBPs were not changed in transgenic mice. Immunohistochemical studies revealed transgene expression predominantly in the thymic medulla and red pulp of the spleen. Body weight and the weights of the spleen, kidney and lung of transgenic mice were not different from controls. In contrast, the thymus of transgenic mice showed a significantly reduced weight and cortex volume. In transgenic thymus and spleen, cell proliferation was inhibited and apoptosis was stimulated. Transgenic mice showed normal T- and B-cell development and normal basal plasma immunoglobulin levels. In conclusion, overexpression of IGFBP-4 inhibits growth of the thymus. IGFBP-4 excess inhibits cell proliferation and stimulates apoptosis in lymphoid tissues, but does not affect lymphocyte development. These findings suggest that IGFBP-4 is a potential growth inhibitor of lymphoid tissues.

IGF-binding protein-5: flexible player in the IGF system and effector on its own

The multiple activities of IGF-I and -II are modulated by a family of IGF-binding proteins (IGFBP-1 to -6). Although structurally related, each IGFBP has unique properties and exerts specific functions. IGFBP-5 is the most conserved IGFBP across species and was identified as an essential regulator of physiological processes in bone, kidney and mammary gland. In addition, IGFBP-5 appears to play a decisive role in the control of proliferation of specific tumour cell types. In many situations IGFBP5 exerts biological activities in the absence of IGFs, indicating the existence of IGF-independent actions. This concept was supported by the unexpected localisation of IGFBP-5 in the nucleus and the description of IGFBP-5-specific membrane-bound IGFBP-5 receptor(s). The scope of this review is to summarise the available information about the structure of IGFBP-5 and the regulation of its expression. Furthermore, the potential significance of IGFBP-5 in the regulation of physiological processes will be critically analysed in the light of recent experimental data.

Insulin-like growth factor-binding protein-5 inhibits growth and induces differentiation of mouse osteosarcoma cells

The precise role of insulin-like growth factor-binding protein-5 (IGFBP-5) in regulating the growth of tumor cells, especially of bone-derived malignant cells, is not well understood. We have investigated the biological activity of IGFBP-5 by transfecting OS/50-K8 mouse osteosarcoma cells with an expression vector containing the osteocalcin promoter and the complete mouse IGFBP-5 cDNA (OC-IGFBP-5). Overexpression of IGFBP-5 mRNA and secretion of increased amounts of bioactive protein in conditioned media were demonstrated in different clones. For the analysis of cell proliferation, three clones exhibiting high levels of IGFBP-5 expression were selected and compared to a mock clone and to nontransfected parental cells. IGFBP-5-secreting clones displayed reduced proliferation under both anchorage-dependent and -independent conditions (P < 0.05). The increase in proliferation observed in IGFBP-5-secreting clones after addition of exogenous IGF was significantly lower than that observed in mock-transfected or parental cells. A similar result was obtained with long[R3]IGF-I which has a low affinity for all IGFBPs, suggesting that the inhibitory effect of IGFBP-5 is only partially IGF-dependent. OC-IGFBP-5-transfected clones expressed significantly higher amounts of osteocalcin mRNA (P < 0.05) and secreted more osteocalcin protein than a mock clone or parental OS-50/K8 cells. Thus, part of the growth-inhibiting effect of IGFBP-5 may be due to an induction of differentiation in these cells.

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.

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.

Interleukin-6 stimulates clonogenic growth of primary and metastatic human colon carcinoma cells

Interleukin-6 (IL-6) is a pleiotropic cytokine which exerts biological activities on various cell types including neoplastic cells. We have investigated the biological effect of IL-6 and the expression of IL-6 receptors (IL-6R) on human colorectal carcinoma cell lines. Isreco-1 was derived from the primary site of a colon cancer while Isreco-2 and Isreco-3 were established from a liver and peritoneal metastasis of the same patient. IL-6 stimulated colony formation in methylcellulose of Isreco-1 cells to 150% (P < 0.05). The effect was even more pronounced on the metastatic Isreco-2 line where colony numbers in the presence of IL-6 were enhanced up to four-fold (P < 0.0001) in a dose-dependent fashion. An anti-IL-6 antibody completely abolished this growth stimulatory effect of IL-6. RT-PCR analysis revealed transcripts for IL-6Ralpha and gp 130 in these cell lines. Experiments with additional cell lines confirmed the general expression of gp130 but showed limited expression of the IL-6Ralpha chain. Surprisingly, about half of the cell lines tested expressed IL-6 mRNA at low levels which was not translated into protein. Our results suggest that IL-6 can potently stimulate anchorage-independent growth of some colorectal carcinoma cells. This stimulation appears to occur through a paracrine mechanism.

Transgenic mouse models for studying the functions of insulin-like growth factor-binding proteins

The insulin-like growth factor-binding proteins (IGFBPs) comprise a family of six related peptides that interact with high affinity with IGFs. IGFBPs compete with IGF receptors for IGF binding, and as a consequence of this competition they can affect cell growth. In addition, IGF-independent regulatory mechanisms of IGFBPs have been described. Despite their common property to interact with IGFs every IGFBP is expressed in a tightly regulated time- and tissue-specific manner suggesting that each protein may have its own distinct functions. Several transgenic mouse models overexpressing IGFBP-1, -2, -3, or -4 were developed in the past few years. Brain abnormalities were a common feature of IGFBP-1 transgenic models. Individual strains showed alterations in glucose homeostasis, reproductive performance, and a reduction of somatic growth as the most prominent phenotypes. The latter was also the main effect observed in IGFBP-2 transgenic mice. The overexpression of IGFBP-3 under the control of an ubiquitous promoter resulted in selective organomegaly, whereas mammary gland-targeted expression of this protein caused an altered involution after pregnancy in this organ. Tissue-specific overexpression of IGFBP-4 resulted in hypoplasia and reduced weight of smooth muscle-rich tissues such as bladder, aorta, and stomach. This review summarizes the current knowledge about the actions of IGFBPs in vivo based on the presently established transgenic mice.

Differential cross-talk of estrogen and growth factor receptors in two human mammary tumor cell lines

Cultured human mammary MCF7 and T47D tumor cell lines were used to test the interference of the partial antiestrogen 4'-hydroxytamoxifen (4-OH-TAM) and the pure antiestrogen ZM 182780 with growth factor (IGF-I, heregulin) signaling pathways. Growth of both cell lines was stimulated by IGF-I (20 ng/ml) or heregulin (3 nM). ZM 182780 effectively blocked growth factor induced as well as basal proliferation of MCF7 cells while the compound was ineffective in interfering with growth factor mitogenic activity in T47D cells. On both cell lines the IGF-I or heregulin- induced proliferation was enhanced further by 4-OH-TAM. This synergism could be inhibited dose-dependently by ZM 182780. When cells were grown in the presence of estradiol plus growth factors, the antiestrogenic potencies of both compounds and the efficacy of ZM 182780 were unaffected, while the efficacy of 4-OH-TAM was reduced. Our data show cell type specific cross-talk between the receptor for estrogen and that for IGF-I or heregulin, which is different in MCF7 and T47D cells, respectively. In MCF7 cells with demonstrable cross-talk, a clear superiority exists for a pure antiestrogen over a partial agonist in interfering with growth factor mitogenic activity.

Switch from antagonist to agonist of the androgen receptor bicalutamide is associated with prostate tumour progression in a new model system

Advanced prostate cancer is treated by androgen ablation and/or androgen receptor (AR) antagonists. In order to investigate the mechanisms relevant to the development of therapy-resistant tumours, we established a new tumour model which closely resembles the situation in patients who receive androgen ablation therapy. Androgen-sensitive LNCaP cells were kept in androgen-depleted medium for 87 passages. The new LNCaP cell subline established in this manner, LNCaP-abl, displayed a hypersensitive biphasic proliferative response to androgen until passage 75. Maximal proliferation of LNCaP-abl cells was achieved at 0.001 nM of the synthetic androgen methyltrienolone (R1881), whereas 0.01 nM of this compound induced the same effect in parental cells. At later passages (> 75), androgen exerted an inhibitory effect on growth of LNCaP-abl cells. The non-steroidal anti-androgen bicalutamide stimulated proliferation of LNCaP-abl cells. AR protein expression in LNCaP-abl cells increased approximately fourfold. The basal AR transcriptional activity was 30-fold higher in LNCaP-abl than in LNCaP cells. R1881 stimulated reporter gene activity in LNCaP-abl cells even at 0.01 nM, whereas 0.1 nM of R1881 was needed for induction of the same level of reporter gene activity in LNCaP cells. Bicalutamide that acts as a pure antagonist in parental LNCaP cells showed agonistic effects on AR transactivation activity in LNCaP-abl cells and was not able to block the effects of androgen in these cells. The non-steroidal AR blocker hydroxyflutamide exerted stimulatory effects on AR activity in both LNCaP and LNCaP-abl cells; however, the induction of reporter gene activity by hydroxyflutamide was 2.4- to 4-fold higher in the LNCaP-abl subline. The changes in AR activity were associated neither with a new alteration in AR cDNA sequence nor with amplification of the AR gene. Growth of LNCaP-abl xenografts in nude mice was stimulated by bicalutamide and repressed by testosterone. In conclusion, our results show for the first time that the nonsteroidal anti-androgen bicalutamide acquires agonistic properties during long-term androgen ablation. These findings may have repercussions on the natural course of prostate cancer with androgen deprivation and on strategies of therapeutic intervention.

Novel steroid-linked conjugates of 17 beta-[N-[N'-(2-chloroethyl)-N'-nitroso]carbamoyl]amino acids and their antineoplastic activity against Noble Nb prostate carcinoma model in rats

The novel steroid conjugates 17 beta-[N-[N'-(2-chloroethyl)-N'-nitroso] carbamoyl]-glycyl-19-nortestosterone (1) and 17 beta-[N-[N'-(2-chloroethyl)-N'-nitroso]carbamoyl]-L-alyanyl-19- nortestosterone (2) were synthesized and characterized with respect to affinity for steroid receptors and for androgenic efficacy. At an i.p. dosage of 50 mg/kg, conjugates 1 and 2 induced strong tumor inhibition of Nobel Nb prostate carcinoma in rats, but also a marked loss of body weight. In two further experiments, treatment with conjugate 2 at a dosage of 25 mg/kg demonstrated high antitumor activity without indication of toxicity. Conjugate 2 achieved the same tumor growth inhibition as a nearly twofold molar dose of cyclophosphamide. The results indicate reproducibly high antitumor activity of 2 in the Noble Nb model at a well tolerated dosage. A low dose equimolar mixture of unlinked N-(2-chloroethyl)-N-nitrosocarbamoyl (CNC)-alanine and 19-nortestosterone was significantly more toxic than conjugate 2, showing about the same adverse effect on the body weight as the conjugate at high dosage. CNC-L-alanine at equimolar dosage was highly toxic, causing early death of all animals.

Estrogenic regulation of clusterin mRNA in normal and malignant endometrial tissue

Clusterin is a heterodimeric, 80kDa, glycoprotein that is synthesized in a wide variety of tissues in response to a number of diverse stimuli, including hormone ablation. We have investigated the regulation of clusterin expression by estradiol and anti-estrogens in RUCA-I rat endometrial adenocarcinoma cells in vitro and in vivo. We have also compared clusterin expression in endometrial tumors and in normal uterine tissue. Estradiol treatment significantly increases the steady state mRNA levels of clusterin in RUCA-I cells cultured on a reconstituted basement membrane, with a maximal induction 24 hr after estradiol treatment. The inductive effects of estrogen on clusterin mRNA steady state levels in vitro are significantly more pronounced than the effects on fibronectin mRNA levels, an estrogen-repressed gene in RUCA-I. In vivo, induction of clusterin expression in primary and metastatic endometrial adenocarcinoma is also dependent on the presence of estradiol, in marked contrast to expression of clusterin in the normal endometrium of the same animals. These data suggest that clusterin mRNA expression in rat endometrial adenocarcinoma cells is tightly regulated by estrogens and anti-estrogens in vitro and in vivo, and that there is a complex mechanism of regulation of clusterin expression in the normal and cancerous endometrium.

Estrogenic regulation of clusterin mRNA in normal and malignant endometrial tissue

Clusterin is a heterodimeric, 80kDa, glycoprotein that is synthesized in a wide variety of tissues in response to a number of diverse stimuli, including hormone ablation. We have investigated the regulation of clusterin expression by estradiol and anti-estrogens in RUCA-I rat endometrial adenocarcinoma cells in vitro and in vivo. We have also compared clusterin expression in endometrial tumors and in normal uterine tissue. Estradiol treatment significantly increases the steady state mRNA levels of clusterin in RUCA-I cells cultured on a reconstituted basement membrane, with a maximal induction 24 hr after estradiol treatment. The inductive effects of estrogen on clusterin mRNA steady state levels in vitro are significantly more pronounced than the effects on fibronectin mRNA levels, an estrogen-repressed gene in RUCA-I. In vivo, induction of clusterin expression in primary and metastatic endometrial adenocarcinoma is also dependent on the presence of estradiol, in marked contrast to expression of clusterin in the normal endometrium of the same animals. These data suggest that clusterin mRNA expression in rat endometrial adenocarcinoma cells is tightly regulated by estrogens and anti-estrogens in vitro and in vivo, and that there is a complex mechanism of regulation of clusterin expression in the normal and cancerous endometrium.

Negative cooperativity between alpha 3 beta 1 and alpha 2 beta 1 integrins in human mammary carcinoma MDA MB 231 cells

The alpha 3 beta 1 integrin has been implicated as a receptor for several matrix components, including collagen, fibronectin, and laminins. The function of alpha 3 beta 1 seems to be very versatile involving cell adhesion to or migration on ECM, establishment of cell-cell contacts in aggregates, as well as linkage to intracellular tyrosine phosphorylation cascades. Here we report a strong induction of attachment of alpha 3 beta 1 integrin expressing human breast carcinoma cell line MDA MB 231 to matrix proteins by two alpha 3 integrin subunit function-blocking monoclonal antibodies (P1B5 and ASC-1). In contrast, stimulation of adhesion to ECM by inhibitory alpha 3 integrin-specific antibodies was not observed in the alpha 3 beta 1 integrin-expressing nonmalignant human mammary epithelial cell line MCF-10A or the human breast carcinoma cell line MDA MB 468 that expressed relatively low amounts of alpha 3 beta 1 integrin at the cell surface. This increase was specific for collagens and not observed on fibronectin or laminin. Physiological concentrations of bivalent cations were not required. MAb P1B5 did not induce homotypic aggregation of MDA MB 231 cells. The P1B5-induced increase in cell attachment to collagens could be prevented but not reduced below control levels by blocking mAb to the alpha 2 integrin subunit. Function blocking anti-alpha 5 integrin subunit mAb was without effect while anti-beta 1-mAb completely abolished adhesion. Our data indicate that negative cooperativity between integrins results in transdominant inhibition of alpha 2 beta 1 function by alpha 3 beta 1 in human MDA MB 231 but not MDA MB 468 tumor cells or nonmalignant MCF-10A cells.

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.

Tumor metastasis inhibition with the prostacyclin analogue cicaprost depends on discontinuous plasma peak levels

Stable prostacyclin analogues exert a strong inhibitory effect on lymphogenous as well as haematogenous tumor metastasis in a series of tumor lines. The strong inhibition of metastasis was achieved by repeated once-daily i.g. applications. The mechanism of antimetastatic action is related to the expression of functional IP-receptors (PGI-receptors). As cellular assay systems indicated that the IP-receptor mediated signalling is down-regulated upon continuous exposure to prostacyclin or stable derivatives, it has been questioned whether a mode of drug application with constant plasma drug levels may potentially result in a decrease of the antimetastatic effect. We addressed this question using the stable prostacyclin analogue cicaprost in a disease model by comparing i.g. applications given once daily with a continuous administration of equivalent doses via drinking water. Very similar to our previous investigations in the 13762NF MTLn3 rat mammary carcinoma model, cicaprost administered by i.g. application strongly reduced lung and lymph node metastasis. In contrast, administration of equivalent doses via drinking water leading to lower but constant steady-state plasma levels failed to exert inhibitory effects. Plasma and urine levels of cicaprost were measured with a sensitive radioimmunoassay on the last treatment day. Pharmacokinetic evaluation demonstrated a similar bioavailability of cicaprost in both groups. This result first demonstrates a treatment failure of a prostacyclin derivative in a chronic disease model in association with a continuous drug administration leading to constant plasma levels. A desensitization of receptor signalling by constant plasma levels may be a possible mechanism for treatment failure.

Progesterone receptor repression by estrogens in rat uterine epithelial cells

Measurements performed using cell lines or animal tissues have shown that the progesterone receptor (PR) can be induced by estrogens. By use of immunohistochemistry we studied the effects of estrogens on the PR levels in the individual cell types of the target organs uterus and breast. In the uteri of rats, ovariectomy induced a decrease in PR immunoreactivity within the myometrium and outer stromal cell layers. In contrast, in the uterine luminal and glandular epithelium and surrounding stromal cell layers the PR immunoreactivity was significantly enhanced. The same picture emerged when intact rats were treated with the pure estrogen receptor antagonist, ZM 182780 (10 mg/kg/d). Treatment of ovariectomized rats with estradiol resulted in high PR levels in the myometrium and stroma cells but low PR immunoreactivity in the epithelial cells. The ER-mediated repression of the PR immunoreactivity was evidently restricted to the uterine epithelium, as we found that in the epithelial cells of the mammary gland and in cells of N-nitrosomethylurea-induced mammary carcinomas the PR expression was induced by estrogens and was blocked by the pure antiestrogen ZM 182780. These results clearly show that in the rat the activated ER induces diverging effects on PR expression in different cell types even within the same organ.

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.

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.

Inhibition of metastasis by cicaprost in rats with established SMT2A mammary carcinoma growth

Cicaprost, a stable prostacyclin analog has been shown to be antimetastatically active in a series of metastasizing rodent tumors. Whereas starting treatment with Cicaprost on the day of tumor implantation was a characteristic feature of our previous investigations, the present study focused on the antimetastatic potency of Cicaprost in animals with established tumor growth. We have previously reported that, in Wistar-Furth rats bearing subcutaneously implanted SMT2A mammary carcinoma, Cicaprost in daily oral doses of 0.1 to 1.0 mg/kg given from the day of tumor implantation to the end of the experiment led to a strong decrease in the number of lung metastases. The 1.0 mg/kg doses reduced the number of lung metastases by about 95% compared with the control. In the present study, we have examined the effect of delaying the start of treatment in animals with established tumor growth, Cicaprost in daily oral doses of 0.1 mg/kg given from Day 10 until Day 32 reduced the number of lung metastases by about 80% compared with the control. In contrast, surgical removal of palpable primary tumors had no effect on lung metastasis. We conclude that Cicaprost exhibits strong antimetastatic activity in the SMT2A rat mammary carcinoma model and interferes not only with mechanisms of tumor cell-blood cell interaction, tumor cell adhesion, and extravasation, but also with steps following extravasation.

The future of antihormone therapy: innovations based on an established principle

Endocrine therapy of mammary and prostate cancer has been established for decades. The therapies available to block sex-hormone-receptor-mediated tumor growth are based on two principles: (i) ligand depletion, which can be achieved surgically, by use of luteinizing-hormone-releasing hormone analogues or inhibitors of enzymes involved in steroid biosynthesis or by interfering with the feedback mechanisms of sex hormone synthesis at the pituitary/hypothalamic level; (ii) blockade of sex hormone receptor function by use of antihormones. The antiestrogen tamoxifen, which is the compound of choice for the treatment of mammary carcinoma, has the drawback of being a partial agonist. A complete blockade of estrogen receptor (ER) function can be achieved by a new class of compounds, pure antiestrogens. In contrast to aromatase inhibitors, pure antiestrogens are able to block ER activation by ligands other than estradiol and can also interfere with ligand-independent ER activation. In addition to estradiol, progesterone has a strong proliferative effect in mammary carcinomas. Antiprogestins are promising new tools for clinical breast cancer therapy. These compounds clearly need a functionally expressed progesterone receptor to block tumor growth, but there is strong experimental evidence that their tumor inhibition is based on more than just progesterone antagonism. The ability of these compounds to induce tumor cell differentiation that leads to apoptosis is unique among all other endocrine therapeutics. In prostate tumors that have relapsed from current androgen-ablation therapies the androgen receptor (AR) is still expressed and, compared to the primary tumors, its level is often even enhanced. Mutated AR that can be activated by other compounds such as adrenal steroids, estrogens, progestins and even antiandrogens have been detected in recurrent tumors. Thus, relapse of tumors under the selective pressure of common androgen-ablation therapies can be caused by acquired androgen hypersensitivity and AR activation by ligands other than (dihydro-)testosterone. There is a clinical need for future compounds that produce a complete blockade of AR activity even in recurrent tumors. Preclinical experiments indicate that combination therapy as well as the extension of endocrine treatments to several other tumor entities are promising approaches for further developments. Examples are the combination of antiestrogens and antiprogestins for breast cancer treatment, or the treatment of prostate carcinomas with antiprogestins.

The rat endometrial adenocarcinoma cell line RUCA-I: a novel hormone-responsive in vivo/in vitro tumor model

The recently established, estrogen receptor positive rat endometrial adenocarcinoma cell line RUCA-I was tested for estrogen responsiveness in vivo and in vitro. In vivo, 10(6) RUCA-I cells were injected subcutaneously into intact, ovariectomized, or ovariectomized, estradiol-substituted syngenic DA/Han rats. All animals developed well differentiated endometrial adenocarcinoma, that had metastasized to peripheral lymph nodes and into the lung. Ovariectomy reduced tumor and lymph node weight, as well as number of lung metastases significantly compared to controls. In another series of experiments, treatment with the pure anti-estrogen ZK 119010 basically gave the same results as seen in ovariectomized animals, whereas tamoxifen treatment had no effect on metastasis of RUCA-I cells. These findings clearly demonstrate the estrogen dependency of growth and metastasis of RUCA-I cells in vivo. In vitro, we assessed the estrogenic and anti-estrogenic potency of various anti-estrogens, thereby investigating their effects on the expression of components of the complement C3 complex as an estradiol-induced protein and on the expression of fibronectin as an estrogen-repressed protein. Evaluating the relative anti-estrogenic potency of these anti-estrogens we found that ICI 164384 and ICI 182780 behaved as complete antagonists in vitro. Tamoxifen, like estradiol, stimulated complement C3 production and repressed fibronectin expression and has to be regarded as an agonist in this particular in vitro system. ZK 119010 if given alone had no significant influence on the biosynthesis of complement C3 and of fibronectin if compared to the unstimulated control. In addition, another estrogen dependent parameter was identified. Estrogen and anti-estrogen treatment affected glycosylation of complement C3 components. After estradiol treatment predominantly the higher glycosylated epitope of complement C3 became detectable, which could be transformed into the low molecular weight epitope by treatment with hyaluronidase. Finally, we compared the anti-proliferative effects of ICI 164384 and of tamoxifen in vitro. Both anti-estrogens slightly inhibited the growth of RUCA-I rat endometrial adenocarcinoma cells. In conclusion, RUCA-I cells represent a powerful, endometrial derived experimental model to test the agonistic and antagonistic properties of anti-estrogens on growth and metastasis in vivo and on gene expression in vitro. The effects of the tested anti-estrogens on gene expression of RUCA-I cells were found to be useful in predicting their effectiveness on tumor growth in vivo.

Tumorigenesis disrupts hormonal regulation of tenascin expression in regressing Dunning R 3327 H prostate carcinoma

We recently reported that androgen ablation either by orchiectomy or antiandrogen treatment resulted in the expression of the extracellular matrix glycoprotein tenascin in the regressing rat prostate. With the study presented here we investigated whether tenascin is expressed in the Dunning R 3327 H tumor and if orchiectomy and antiandrogen treatment affect tenascin expression. Experimentally, male rats were inoculated s.c. with pieces of Dunning tumor into the hind limb of both sides. Three months after inoculation rats were either orchiectomized or received a daily dose of 3 mg of cyproterone acetate or flutamide. Following a treatment period of 13 weeks, orchiectomy reduced tumor area by more than 60% compared to untreated controls. Cyproterone acetate and flutamide reduced tumor area significantly up to 30%. The amount and intensity of tenascin immunoreactivity appeared to be independent of the hormonal treatment and rather correlated to the content of tumor stroma. Those tumors with small, densely packed glandular ducts possessing almost no stromal tissue stained weakly for tenascin, whereas those tumors with larger ducts and significant stroma stained intensely. Staining intensity was particularly high at these sites where tumors infiltrated neighboring tissues, in proximity of infiltrating blood cells and close to necrotic areas. In summary, our results demonstrate a specific pattern of tenascin expression in Dunning R 3327 H rat prostate carcinomas, which appear to be independent of the hormonal treatment. We therefore conclude that tumorigenesis disrupts hormonal regulation of tenascin expression which we detected in the normal prostate gland after treatment with antiandrogens.

Antimetastatic action of the prostacyclin analogue cicaprost in experimental mammary tumors

In breast cancer, the survival rate strongly depends on the number of lymph nodes involved. A drug with a specific inhibitory activity on lymph node and organ metastases would therefore be a candidate for adjuvant therapy after surgery. Prostacyclin and its stable analogues have been shown to interfere with certain steps of the metastatic cascade and to inhibit the number of lung colonies after i.v.-inoculation of various tumor cell lines. Our data reveal that cicaprost, a metabolically stable and orally active analogue of prostacyclin, has pronounced antimetastatic effects in a series of spontaneously metastasizing rodent tumors. In the SMT 2a and 13762 MTLn3 mammary carcinomas of the rat, cicaprost given daily from the day of tumor implantation strongly inhibits the number of lung metastases as well as lymph node weights without exerting an effect on the primary tumor. Even starting treatment when palpable primary tumors are present gives a pronounced antimetastatic activity. To demonstrate that cicaprost has an effect on metastases already settled in the respective organ, treatment was started after surgical removal of the primary tumor. In the SMT 2a tumor, a strong inhibition of the number of metastases was shown. Interestingly, a perioperative treatment schedule was also effective in both models used. As primary tumor growth in vivo or proliferation in vitro remained unchanged by cicaprost, its mode of action seems to be related to one or more mechanisms of the metastatic process. In tumor cell lines expressing a functional prostacyclin receptor, stimulated tumor cell migration is inhibited and changes of differentiation status are obvious. In conclusion, cicaprost strongly inhibits lymph node and organ metastases of spontaneously metastasizing rodent mammary tumors with a mode of action different from cytostatic or antihormonal drugs.

Rodent model of systemic mammary tumor disease by surgical removal of the spontaneously metastasizing SMT2A mammary carcinoma: inhibitory effect of the stable prostacyclin analogue cicaprost on occult metastasis

Cicaprost, a stable prostacyclin analogue, has been shown to be anti-metastatically active in a series of metastasizing rodent tumors. Start of treatment with cicaprost immediately before tumor implantation was a characteristic feature of our previous investigations. We have reported that in rats bearing mammary-fat-pad-implanted SMT2A mammary carcinoma, cicaprost treatment starting before tumor implantation led to a strong decrease in the number of lung metastases. In order to determine the effect on occult tumor metastasis, the present study examined the effect of starting treatment when tumor metastasis is already present. Cicaprost in daily oral doses of 0.1 mg/kg given from day 10 to day 32 reduced the number of lung metastases by about 75% compared with the control, whereas surgical removal of palpable primary tumors on day 5 or day 10 failed to influence lung metastasis. Using different treatment schedules, a pronounced reduction of the number of lung metastases was achieved by administration of cicaprost until the end of the experiment (from day 5 to day 35), whereas short-term treatments (from day 5 to day 15 or to day 25) were without significant effect. In rats whose SMT2A tumors were surgically removed 10 days after tumor implantation, there was a strong decrease of lung metastases by cicaprost given from day 20 to day 36. In addition to its inhibitory potential in animals with advanced tumor disease, cicaprost showed anti-metastatic action when used in peri-operative treatment of animals whose primary tumors had been removed. In conclusion, the present results demonstrate that cicaprost exhibits strong anti-metastatic activity in the SMT2A rat mammary-carcinoma model with treatment started when occult tumor metastases are already present. Results also indicate that direct effects on tumor cells may contribute to the anti-metastatic action of cicaprost in spontaneously metastasizing tumors.

Prostacyclin and its analogues: antimetastatic effects and mechanisms of action

More than a decade ago, prostacyclin, a dienoic bicyclic eicosanoid derived from the metabolism of arachidnoic acid, was found to possess potent inhibitory effects on tumor cell metastasis. Thereafter, several laboratories demonstrated the metastasis-suppressive activity of prostacyclin in a wide spectrum of tumor types. Due to the short half-life of prostacyclin, researchers have focused on looking for stable prostacyclin analogues which have extended half lives and increased bioavailabilities. Cicaprost, among other prostacyclin analogues tested, has been demonstrated, like prostacyclin, to effectively inhibit metastasis in several different animal models (i.e., both experimental and spontaneous metastasis models). Prostacyclin as well as cicaprost prevent not only hematogenous, but also lymphatic metastasis. Furthermore, these compounds also inhibit the growth of established micrometastases after removal of the primary tumors. Mechanistic studies revealed that the antimetastatic effects of prostacyclin and its analogues are more related to their interference with tumor cell-host interactions (such as tumor cell induced platelet aggregation, tumor cell adhesion to endothelial cells and subendothelial matrix, tumor cell induced endothelial cell retraction, etc.) than their direct inhibition of the growth of primary tumors. The potent and widespread metastasis-retarding effects of prostacyclin and its stable analogues in animal tumor models warrant their clinical trial in treating human cancer patients and preventing metastasis.

Effect of the nonsteroidal antiestrogen ZK 119.010 on growth and metastasis of the EnDA endometrial carcinoma

For patients with disseminated endometrial cancer the prognosis is poor. Radiotherapy, chemotherapy or high-dose progestins have been of limited value in the clinic, with low response rates and a usually short duration. Because of the role of estrogen in the etiology of this disease, a rationale exists for therapies using estrogen antagonists. In order to test this strategy, we used the EnDA endometrial carcinoma of the rat recently described by us. The nonsteroidal antiestrogen ZK 119.010 inhibited the primary-tumor growth of the s.c. implanted EnDA endometrial carcinoma by 50%, being superior to high-dose progestin and tamoxifen (TAM). Moreover, in intact as well as in castrated estrogen (E2)-substituted rats, ZK 119.010 substantially reduced metastatic-tumor growth in the lymph nodes and lungs. With TAM, however, the number of lung metastases in intact and in castrated E2-substituted rats either rose or remained stable and the weight of lymph nodes in intact rats increased. After TAM treatment, almost no low-salt-extractable (cytosolic) estrogen receptor (ER) was measurable in the tumor, whereas ZK 119.010 did not alter ER concentrations. The stimulation of metastatic tumor growth, as well as the loss of cytosolic ER under TAM therapy, may reflect the well-known agonist activity of this compound in uterine tissues. ZK 119.010, however, not only lacks this agonist activity, but it exerts a strong antagonistic one. In conclusion, pure antiestrogens may help to improve treatment of endometrial cancer.

Enhancement of the antitumor efficacy of the antiprogestin, onapristone, by combination with the antiestrogen, ICI 164384

So far, no combination of endocrine treatments has been routinely used in the therapy of breast Cancer. It was, therefore, our interest to determine whether the combination of the antiprogestin, onapristone (ON), and the pure antiestrogen, ICI 164384 (ICI) might provide a more effective therapy than either monotherapy in experimental mammary tumors containing both estrogen and progesterone receptors. In the MXT-mammary tumor of the mouse, ON (5 mg/kg) administered for 3 weeks exerted an ovariectomy-like antitumor effect (56% inhibition), whereas ICI (30 mg/kg) was weakly effective (28% inhibition). The combination of ON and ICI was, however, distinctly more effective than the monotherapies or ovariectomy, causing 78% inhibition. A similar potentiation of antitumor effect by the combination was manifested in the dimethylbenzanthracene-induced mammary tumor of the rat when ON (5 mg/kg) and ICI (30 mg/kg) were administered once daily for 4 weeks (s.c.). The remission rates of tumors found after treatment with ICI, ON, the combination and ovariectomy (complete and partial remission) were 15%, 46%, 71% and 100% respectively. In the animals bearing DMBA-induced tumors, treatment with ON alone significantly increased the serum levels of luteinizing hormone and prolactin, but caused only a slight increase in the peripheral levels of estradiol and progesterone. ON had no appreciable effect on the uterine and ovarian weights. ICI reduced the uterine weight and the serum progesterone level. In the combination with ON, ICI reversed the effect of ON on the progesterone level without influencing the luteinizing hormone and prolactin levels. These findings suggest that the augmentation of antitumor effectiveness by the combination of two antihormones can be ascribed not only to their effects at estrogen- and progesterone-receptor-binding sites, but also to the decrease in the peripheral level of progesterone. Thus, an appropriate combination of antiprogestin and pure antiestrogen may be useful in the management of breast cancer.

Stromal expression of tenascin is inversely correlated to epithelial differentiation of hormone dependent tissues

We were previously investigating the expression of the extracellular matrix glycoprotein tenascin in normal and malignant endometrial tissues of humans and rodents. These studies suggested that the expression of tenascin was induced by proliferating epithelia (normal and particularly malignant) and was downregulated with their differentiation. The aim of this study was to investigate the hormone dependency of tenascin expression in (a) the transplantable EnDA endometrial tumor model with or without estrogen deprivation (ovariectomy) of the animals, (b) DMBA-induced rat mammary tumors with or without a hormonal treatment of the animals [ovariectomy, antiestrogen (tamoxifen) or antiprogestin (ZK 98299) treatment] and (c) in the rat prostate of untreated or androgen deprived animals (orchiectomy, flutamide-, casodex- or cyproterone acetate (CPA)-treatment). 1. Estrogen withdrawal by ovariectomy did not affect tenascin expression in transplantable EnDA endometrial adenocarcinoma, meaning the entire extracellular space of the stromal mesenchyme was decorated by tenascin immunoreactivity. 2. In untreated DMBA-induced rat mammary tumors almost the entire extracellular space of the stroma was stained by tenascin immunoreactivity. Ovariectomy and antiestrogen treatment did not affect tenascin expression. In contrast, antiprogestin treatment induced terminal differentiation of mammary tumor cells and in parallel downregulated tenascin expression. 3. In the normal rat prostate no tenascin was detectable by immunocytochemistry. However, following androgen deprivation we found tenascin expression in the stroma of the prostate. The most prominent expression was observable after CPA-treatment, possibly due to its progestagenic potency. In conclusion, the hormones and antihormones tested show no direct effect on the stromal expression of tenascin. However, proliferative activity and a low degree of differentiation of the epithelium induces tenascin expression, whereas epithelial differentiation apparently shuts down tenascin expression. Preliminary in vitro studies suggest that paracrine acting growth factors trigger the hormonal regulation of tenascin expression.

The stable prostacyclin analogue Cicaprost inhibits metastasis to lungs and lymph nodes in the 13762NF MTLn3 rat mammary carcinoma

Prostacyclin and its stable analogues have been shown to interfere specifically with certain steps of the metastatic cascade. The antimetastatic activity of the stable prostacyclin analogue Cicaprost (Schering AG) on haematogenous metastasis in a series of tumours in rats and mice has been well established. In order to test the effect of Cicaprost on lymphogenous metastasis we chose the metastatic cell clone MTLn3 derived from the 13762NF rat mammary carcinoma. The effect of Cicaprost on prevention of lung metastasis, lymph node metastasis and primary tumour growth was investigated. Cicaprost given in daily doses of 0.01, 0.03 and 0.1 mg/kg orally, reduced the number of lung metastases in a dose-dependent manner. Whereas the median number of lung metastases in the controls was greater than 1000, Cicaprost at a dose of 0.1 mg/kg reduced the number of lung metastases to between 11 and 100. The weight of the ipsilateral axillary lymph nodes was diminished by Cicaprost to 30-50% of controls. Moreover, metastasis to the contralateral axillary lymph node was completely inhibited by Cicaprost at all three doses tested. Cicaprost did not influence the growth rate of the MTLn3 cell clone implanted into the mammary fat pad or the weight of the primary tumour at the end of treatment. In conclusion, in addition to its dose-dependent effect on haematogenous metastasis, Cicaprost strongly inhibits lymph node metastasis.

[meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]- dichloroplatinum(II), a new drug not only parenterally but also orally active in the therapy of breast and prostate cancer

The platinum complex [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)- ethylenediamine]dichloroplatinum(II),K, was tested for its antitumor activity on hormone-sensitive tumor models under peroral administration. The resorption from the gastrointestinal tract was proved by determining the estrogenic effect of K in a dose/activity study using the immature-mouse uterine weight test. In comparison to the subcutaneous injection, a tenfold peroral dose was administered to achieve identical effects. By peroral treatment of the hormone-sensitive MXT(M3.2) mammary carcinoma of the mouse with K an almost complete inhibition of the tumor growth was obtained. This effect was superior to that of subcutaneously applied cisplatin and significantly better than that obtained by perorally administered ligand L at an equimolar dose, indicating that the antitumor effect is caused by the intact complex K and not by the liberated ligand L. The strong antitumor activity of perorally applied K was also demonstrated on the hormone-sensitive Noble Nb-R prostatic carcinoma of the rat. Histological examinations showed that the platinum complex K did not cause cisplatin-like kidney damage or irritations of gastric or intestinal mucosa when given perorally.

The EnDA endometrial adenocarcinoma: an oestrogen-sensitive, metastasizing, in vivo tumour model of the rat

A high percentage of endometrial carcinomas contain oestrogen and progesterone receptors. For endocrine therapy of recurrent endometrial carcinoma, only high-dose progestins are in clinical use. As, therefore, the development of new endocrine treatment strategies is of great interest, suitable animal models for this tumour are essential. Up to now, only human tumour xenografts transplanted in immune-deficient nude mice, but no syngeneic in vivo tumour models, have been available. In the present article we describe the hormone sensitivity of the EnDA endometrial adenocarcinoma of the DA/Han rat growing as s.c. implants in DA/Han rats and athymic nude mice in serial passage. In both species, the tumour expresses oestrogen, but no progesterone receptors. Transplanted in DA/Han rats or nude mice, ovariectomy reduced tumour weight by 64% and 46% respectively. In both species substitution of ovariectomized animals with oestradiol restored tumour weights to intact control levels. Oestradiol substitution of intact animals did not further enhance tumour growth. The growth of the primary tumour was inhibited by medroxyprogesterone acetate (MPA) at a dose of 100 mg/kg by 67% and by tamoxifen at a dose of 20 mg/kg by 38%. Lung metastases were regularly seen in both species, although to a lesser extent in nude mice than in DA/Han rats. Tamoxifen treatment did not alter the number of lung metastases, whereas MPA or ovariectomy produced a significant reduction in the number of lung metastases. The EnDA endometrial carcinoma of the DA/Han rat with respect to its oestrogen sensitivity, oestrogen receptor expression, morphology and metastatic growth, grossly resembles a typical endometrial adenocarcinoma and can therefore be regarded as a useful in vivo experimental model for the evaluation of new endocrine treatment strategies.

Effect of cisplatin on primary tumour growth and liver metastases in the M 5076 reticulum sarcoma: implication for new screening modalities

We investigated the effect of cisplatin given at different treatment intervals on growth of the s.c.-implanted M 5076 reticulum sarcoma and the number of liver metastases at the end of the experiment (day 24). The later the treatment was started, the smaller was the tumour-inhibiting effect of cisplatin on primary tumour growth. Initiation of cisplatin treatment before day 14 after tumour implantation inhibited liver metastases completely. Treatment starting from day 14 or later did not influence the number of liver metastases. With regard to the clinical situation, the data imply that in the search for new leads in anticancer compounds, experimental conditions should concentrate on the inhibition of metastatic tumour growth.

The antitumor potency of progesterone antagonists is due to their differentiation potential

A new therapy for the progesterone receptor positive mammary carcinoma may be the treatment with progesterone antagonists. This new class of antihormones causes a strong inhibition of tumor growth comparable to the potency of ovariectomy in a panel of experimental mammary carcinomas. The mechanisms of the strong tumor-inhibiting action of progesterone antagonists on experimental mammary carcinomas mainly depends on a progesterone receptor mediated process leading to induction of terminal differentiation and a blockade of the cell cycle. To further characterize the antitumor mechanism of progesterone antagonists we analyzed the effects of Onapristone and ZK 112.993 on DMBA- and MNU-mammary tumors of the rat and MXT-tumors of the mouse after different therapy intervals. These hormone-dependent mammary tumors normally display intraductal growth in papillary, cribiform or solid formation, whereas after treatment periods of 2-6 weeks with progesterone antagonists they displayed dysplastic ductal and acinous formations, usually filled with secretory material. Whereas tumor size, mitotic index, and the grade of tumor malignancy decreased distinctly, the volume fraction of glandular structures in the tumors as well as the appearance of apoptosis increased 3-fold compared to the controls. In addition, the mammary glands of progesterone antagonist treated animals showed the morphological features of differentiation with the appearance of secretory activity. Interestingly, the staining pattern of some of the lectins used, especially UEA 1 binding pattern, fits to the concept of differentiation since recent studies revealed a higher degree of fucosylation only in benign lesions of human breast cancers. Therefore, these data underline the concept of a differentiation potential of progesterone antagonists on progesterone receptor positive mammary carcinomas.