Ruthenium-based NAMI-A type complexes with in vivo selective metastasis reduction and in vitro invasion inhibition unrelated to cell cytotoxicity

A series of analogues of NAMI-A, a reference compound active on solid tumor metastases, were synthesized (NAMI-A type complexes). They share the same chemical structure of NAMI-A, and differ from it in the nature of the coordinated nitrogen ligand, such as pyrazole, thiazole and pyrazine, which are less basic than imidazole. This modification confers to the new NAMI-A type complexes a better stability in aqueous solution compared to the parent compound, a very important characteristic for a class of compounds that, with NAMI-A, is currently completing a phase I clinical trial at the Netherlands Cancer Institute of Amsterdam. Cytotoxicity and the effects on cell cycle and invasion were investigated on TS/A, B16-F10 and MCF-7 tumor cell lines, while the inhibition of lung metastases was determined on the mouse experimental tumors Lewis lung carcinoma and MCa mammary carcinoma. The new complexes show a pharmacological activity very similar to that of the parental compound NAMI-A: in vitro they are devoid of meaningful cytotoxicity against tumor cells, and in vivo they inhibit metastasis formation and growth approximately to the same extent as NAMI-A. Thus the new NAMI-A type complexes retain the same potent characteristic of NAMI-A to selectively interact with solid tumor metastases. However, compared to NAMI-A they do not stop cell cycle progression at G2-M level and are more active in preventing the spontaneous invasion of Matrigel by tumor cells exposed for 1 h to 10(-4) M concentration. Globally, these complexes take advantage of the knowledge on NAMI-A and appear particularly interesting for future clinical handling and applications.     

Degradation of basement membrane type IV collagen and lung subendothelial matrix by rat mammary adenocarcinoma cell clones of differing metastatic potentials

A series of rat 13762NF mammary adenocarcinoma cell clones and subclones of various lung metastatic potentials were examined for their abilities to degrade rat lung subendothelial matrix and purified basement membrane type IV collagen. Metastatic potentials were simultaneously determined based on the ability to form "spontaneous" lung metastases after s.c. injection or "experimental" lung metastases after i.v. injection of cells. Microvessel endothelial cells isolated from rat lung were grown in vitro, and the subendothelial matrix containing type IV collagen was metabolically labeled with [3H]proline. When mammary adenocarcinoma cells were placed on the isolated subendothelial matrix, fragmentation and solubilization of [3H]proline-labeled components were observed; highly metastatic 13762NF cells solubilized the matrix at higher rates than did poorly metastatic cells. The 13762NF cells were assayed for type IV collagenolytic activity using [3H]proline-labeled type IV collagen purified from Engelbreth-Holm-Swarm tumor as a substrate. We found excellent correlation between the type IV collagenolytic activities of living cells and their "spontaneous" lung metastatic potentials (r = 0.993). The levels of type IV collagenolytic activity in the conditioned medium depended on the cell culture conditions. In the presence or absence of acid-treated fetal bovine serum, highly metastatic cells secreted higher amounts of type IV collagenolytic enzymes in active and latent forms than did poorly metastatic cells. Incubation of procollagen type IV with medium conditioned by highly metastatic 13762NF cells and treated with trypsin resulted in the production of several large fragments characteristic of type IV collagen. The results suggest that enzymatic degradation of basement membrane type IV collagen is important in lung metastasis of 13762NF mammary adenocarcinoma cells.     

Reduction of in vivo lung metastases by dinuclear ruthenium complexes is coupled to inhibition of in vitro tumour invasion

Mononuclear ruthenium-dmso compounds showed interesting antimetastatic properties on experimental models of solid tumours. In line with the interesting results with multinuclear platinum complexes, which proved to overcome cisplatin resistance, we thought it worthwhile to test the pharmacological properties of some dinuclear ruthenium complexes to ascertain the possible advantages due to the introduction of a second metal centre over NAMI-A and its mononuclear analogues. These compounds belong to the general formula X2[[RuCl4(dmso-S)]2(mu-L)] or [X][[RuCl4(dmso-S)](mu-L)[RuCl3(dmso-S)(dmso-O)]] where L is a nitrogen donor ligand (pyrazine; pyrimidine; 4,4'-bipyridine; 1,2-bis(4-pyridyl)ethane; 1,2-bis(4-pyridyl) ethylene; 1,3-bis(4-pyridyl)propane) and X a counterion. We focused on parameters related to metastatic ability such as gelatinase activity, detected by zymography, and invasive potential, measured by means of a transwell chamber. These activities were correlated to the ability to inhibit tumour metastases in vivo. All dinuclear complexes, except compound D8 ([NH4]2[[RuCl4(dmso-S)]2(mu-pyz]), decrease the number of tumour cells that cross a matrigel barrier, and inhibit MMP-9 gelatinolytic activity at concentrations lower than that of NAMI-A and of other mononuclear ruthenium complexes. In vivo compounds D5 (Na2[[RuCl4(dmso-S)]2(mu-ethylbipy)]) and D7 ([NH4][[RuCl4(dmso-S)](mu-pyz)[RuCl3(dmso-S) (dmso-O)]]) show anti-metastasis activity, at two dose levels, with mild or null effect on primary tumour growth; compound D8 is the weakest active. All compounds tend to accumulate in liver and kidneys, rather than in tumour and lungs. However, compound D5, the most active in vitro on invasion and gelatinases and active in vivo on metastasis, is better concentrated in the lungs than compound D8 which is less active or inactive in vitro and in vivo. Histological analysis show liver, as well as kidney toxicities that limit in vivo activity. These data thus suggest dinuclear ruthenium complexes as promising anti-invasive agents for cancer treatment.     

Enhanced metastatic dissemination to multiple organs by melanoma and lymphoma cells in timp-3-/- mice

Identifying versatile inhibitors of metastasis that operate in multiple sites against distinct cancer cell types is important for designing novel therapeutics for metastasis. We show that multiple tissues of timp-3-/- mice are more susceptible to metastatic colonization. Overall, a 5-14-fold increase in liver and kidney colonization occurred by EL-4 lymphoma cells, and a twofold increase upon targeting B16F10 melanoma cells to the bone or lung of timp-3-/- mice. There was a general lack of macrophage or neutrophil localization to metastases in the liver, kidney and lung, and of osteoclasts to bone in both genotypes. Analysis of lung showed that proliferation or angiogenesis were unaltered within the metastatic colonies. Lung-trap assays revealed that initial tumor cell trapping was similar in the lung vasculature of timp-3-/- and wild-type mice. However, more tumor cells were found in timp-3-/- lungs at 48 and 96 h after tumor cell injection indicating more efficient extravasation and initial proliferation. Activation of pro-MMP-2 was greater in timp-3-/- lungs at these time points. These data demonstrate TIMP-3 functions to inhibit metastatic dissemination of diverse cancer cells to multiple organs. TIMP-3 regulates MMP-2 activation to limit tumor cell extravasation and subsequent colonization of the lung, without augmenting inflammatory cell response.     

Myeloid progenitor cells in the premetastatic lung promote metastases by inducing mesenchymal to epithelial transition

Tumors systemically initiate metastatic niches in distant target metastatic organs. These niches, composed of bone marrow-derived hematopoietic cells, provide permissive conditions for future metastases. However, the mechanisms by which these cells mediate outgrowth of metastatic tumor cells are not completely known. Using mouse models of spontaneous breast cancer, we show enhanced recruitment of bone marrow-derived CD11b(+)Gr1(+) myeloid progenitor cells in the premetastatic lungs. Gene expression profiling revealed that the myeloid cells from metastatic lungs express versican, an extracellular matrix proteoglycan. Notably, versican in metastatic lungs was mainly contributed by the CD11b(+)Ly6C(high) monocytic fraction of the myeloid cells and not the tumor cells or other stromal cells. Versican knockdown in the bone marrow significantly impaired lung metastases in vivo, without impacting their recruitment to the lungs or altering the immune microenvironment. Versican stimulated mesenchymal to epithelial transition of metastatic tumor cells by attenuating phospho-Smad2 levels, which resulted in elevated cell proliferation and accelerated metastases. Analysis of clinical specimens showed elevated versican expression within the metastatic lung of patients with breast cancer. Together, our findings suggest that selectively targeting tumor-elicited myeloid cells or versican represents a potential therapeutic strategy for combating metastatic disease.     

Comparison of the effects of the antimetastatic compound ImH[trans-RuCl4(DMSO)Im] (NAMI-A) on the arthritic rat and on MCa mammary carcinoma in mice

The effects of the new molecule ImH[trans-RuCl₄(DMSO)Im] (NAMI-A), administered orally or intraperitoneally to adjuvant-arthritic rats or orally to mice bearing s.c. or i.m. implants of MCa mammary carcinoma, were studied. NAMI-A was not able to modify the progression of chronic inflammation in the complete Freund-adjuvant injected animals. Histology indicated a significant worsening of the inflammatory process, characterised by an increased infiltration of inflammatory cells, as well as by a remarkable deposition of connective tissue fibres around the blood vessels and alveolar walls. NAMI-A had no effect on primary i.m. implanted MCa mammary carcinoma growth and its lung metastasis formation, but significantly interfered with the cell cycle of primary tumor cells following bolus oral administration. On the contrary, NAMI-A caused a significant inhibition of lung metastasis accompanied by a dramatic deposition of connective tissue fibres around the primary tumor mass, when given as medicated food to mice implanted s.c. with MCa tumor. These data indicated that NAMI-A is well absorbed after oral administration although there is no connection between lung concentration and the antimetastatic activity. Conversely, the marked deposition of connective tissues in NAMI-A treated animals is in agreement with the reported effects of the compund on extracellular matrix and tumor blood vessels.     

Expression of matrix metalloproteinases in the microenvironment of spontaneous and experimental melanoma metastases reflects the requirements for tumor formation

Expression of matrix metalloproteinases (MMPs) and their activation in tumor cells, as well as tumor surrounding stromal cells have been implicated in tumor cell invasion and metastasis. By means of a syngeneic tumor model for either experimental or spontaneous metastases, the differential expression of MMPs and tissue inhibitors of MMPs (TIMPs) in relation to the microenvironment and the way of metastasis induction was characterized. In vitro characterization revealed that increased levels of secreted MMP-2, MMP-9, and TIMP-1 were only detectable in the most aggressive cell line, B16G3.12BM2. Remarkably, active MMP-2 was restricted to this cell line, whereas TIMP-2 and membrane type (MT) 1-MMP expression was comparable in all three of the spontaneously metastasizing melanoma cell lines investigated. In vivo analysis demonstrated that MMP-2, MMP-9, and MT1-MMP were predominantly expressed at the tumor-stroma border of s.c. tumors. Furthermore, functional active MMP-2 was restricted to this invasive front. In spontaneous lymph node or lung metastases, however, MMP-9 was expressed both in the center and the periphery of tumors; these areas were largely negative for MMP-2 and MT1-MMP. Notably, tumor cells of experimental lung metastases did not express MMP-9 at all. These results indicate that expression of MMPs in melanoma metastases is not only influenced by their localization but also the nature of tumor induction, suggesting that individual MMPs serve specific roles during the different stages of metastasis formation.     

Characterization of spontaneous metastases from autochthonous 3-methylcholanthrene-induced tumors

In mice bearing autochthonous 3-methylcholanthrene-induced tumors metastasis was rare, with only 2 out of 47 (4%) animals showing lung secondaries and 1 showing kidney lesions. Surgical excision of autochthonous growing tumors brought only a slight increase in incidence of metastasis (5 out of 42 mice, 12%). Cell lines were established by in vivo and/or in vitro passage from two kidney metastasis found in the same host (0.13-K1 and 0.13-K3) and from a spontaneous lung metastasis found in 2 mice (mR80/43 and mR80/17) and compared to lines from the respective primary tumors (0.13; R80/17; R80/43). Cell lines from metastases and primary tumors were heterogeneous in tumorigenicity, growth rate, metastatic potential (spontaneous), and colonizing capacity (i.v. inoculation). In particular, the mR80-43 line was more metastatic to lungs upon intravenous injection than the parent R80-43 primary tumor. Similarly the 013-K1 line from a kidney secondary caused more lung nodules when inoculated intravenously than the parent 0.13 line, but this was not the case with the 013-K3 line derived from another kidney secondary in the same host. The R80-17 and mR80-17 lines had similar lung-colonizing capacity. Lung colonizing ability was not strictly correlated to the capacity to form spontaneous metastases. Changes in lung-colonizing capacity occurred in part of the lines (013, 013-K1, R80-17, mR80-17) upon in vitro or in vivo passage. These findings with lines from spontaneous metastases from three autochthonous sarcomas extend previous observations on the heterogenous behavior of transplanted metastatic neoplasms.     

Binding of anti-tumor immunoglobulins and their daunomycin conjugates to the tumor and its metastase. In vitro and in vivo studies with Lewis lung carcinoma.

The present study was undertaken in order to evaluate the possibility of using anti-tumor antibodies as specific carriers of chemotherapeutic drugs to tumor metastases. Xenogeneic and syngeneic antisera were prepared against a metastasizing C57BL tumor, the Lewis lung carcinoma (3LL). The binding of absorbed xenogeneic and syngeneic anti-3LL sera or their Ig fractions to 3LL tumor cells was assayed by direct and indirect methods. Antisera prepared against tumor cells from a local growth reacted to a similar extent with those obtained from the lung metastases. Radioiodinated immunoglobulins from syngeneic antisera injected into mice bearing metastases localized preferentially in metastasis-bearing lungs as compared to several other organs tested. No such preferential uptake was observed either in mice bearing metastases injected with iodinated normal Ig or in normal mice injected with iodinated anti-3LL Ig. This relative accumulation in the metastasis-bearing lungs was observed 3-4 days after the inoculation, when the whole Ig fraction was used, whereas a specific antibody-enriched preparation localized as early as 24 h after injection. Daunomycin--anti-3LL-Ig conjugates were effective inhibitors of tumor cells from both local and the metastatic growths. They were more active than either the free drug or drug conjugates of normal Ig, in in vitro assays.     

A critical step in metastasis: in vivo analysis of intravasation at the primary tumor

Detailed evaluation of all steps in tumor cell metastasis is critical for evaluating the cell mechanisms controlling metastasis. Using green fluorescent protein transfectants of metastatic (MTLn3) and nonmetastatic (MTC) cell lines derived from the rat mammary adenocarcinoma 13762 NF, we have measured tumor cell density in the blood, individual tumor cells in the lungs, and lung metastases. Correlation of blood burden with lung metastases indicates that entry into the circulation is a critical step for metastasis. To examine cell behavior during intravasation, we have used green fluorescent protein technology to view these cells in time lapse images within a single optical section using a confocal microscope. In vivo imaging of the primary tumors of MTLn3 and MTC cells indicates that both metastatic and nonmetastatic cells are motile and show protrusive activity. However, metastatic cells show greater orientation toward blood vessels and larger numbers of host cells within the primary tumor, whereas nonmetastatic cells fragment when interacting with vessels. These results demonstrate that a major difference in intravasation between metastatic and nonmetastatic cells is detected in the primary tumor and illustrate the value of a direct visualization of cell properties in vivo for dissection of the metastatic process.     

Down-regulation of osteopontin inhibits metastasis of hepatocellular carcinoma cells via a mechanism involving MMP-2 and uPA

Osteopontin (OPN) has an important role in hepatocellular carcinoma (HCC) progression and metastasis. This study was to investigate the therapeutic potential of inhibition of OPN expression. A 2'-O-methoxyethylribose-modified phosphorothioate antisense oligonucleotides (ASO) was used to knock-down OPN expression in the human metastatic HCC cell line HCCLM6 and in nude mice orthotopically implanted with HCCLM6 showing highly spontaneous lung metastasis. Furthermore, we assessed the metastatic potential of HCCLM6 cells in vitro and in vivo after ASO treatment. Treatment of HCCLM6 cells with OPN ASO inhibited OPN mRNA expression in a dose- and time-dependent manner, whereas the control oligonucleotides had no effect. OPN ASO significantly suppressed migration and invasion of HCCLM6 cells in vitro. Specific suppression of OPN also inhibited matrix metalloproteinase 2 (MMP-2) and urokinase-type plasminogen activator (uPA) expression in HCCLM6 cells. In mice bearing orthotopical xenografts with HCCLM6, OPN inhibition following therapeutic treatment with OPN ASO significantly decreased lung metastases although tumor weight did not appear to be reduced. These findings suggest that OPN-targeted therapy may be a promising strategy for the treatment of HCC metastases.     

Blocking a novel 55 kDa melanoma-associated cell surface antigen inhibits the development of spontaneous metastases and interactions with frozen lung section

We recently identified a novel 55-kDa cell-cell adhesion protein (p55) whose expression is upregulated in primary melanomas in the transition from radial growth phase to vertical growth phase. However, the functional role of p55 in various steps of the metastatic process had not been investigated. We provide evidence that subcutaneous injection of metastatic melanoma variant T1P26 in immunosuppressed newborn rats rapidly caused spontaneous metastatic lung lesions that could be readily detected by histochemical analysis with the anti-p55 monoclonal antibody (MAb) LY1. Subsequently, we were able to demonstrate that multiple subcutaneous injections of the LY1 MAb starting on the same day after tumor cell inoculation of T1P26 cells specifically blocked the formation of spontaneous lung metastases, yet had no effects on primary tumor growth, suggesting a critical role of p55 in the earlier steps of the intravasation process. To study later stages in spontaneous metastasis, we investigated the role of p55 in organ-specific cell adhesion of tumor cells in vitro. We showed that the T1P26 variant attached preferentially to lung frozen sections compared with other organs, reflecting the pattern of organ involvement of metastasis in vivo and that LY1 significantly blocked this interaction. However, no significant differences in attachment to lung sections were observed between the parental melanoma cell line M(4)Beu and its derived variant, although cellular topography analysis indicated a preferential attachment of a T1P26 variant on specific compartments of the lungs such as the perialveolar components, the endothelium and the vessel lumen of pulmonary venules. Attachment of the T1P26 variant to lung sections is not due to alterations of tumor cell adherence to basement membrane matrix by the LY1 MAb, suggesting that p55 is involved in cellular adhesion with cellular elements of the lung. p55 could represent a new functional constituent that contributes to the metastatic spread of melanoma cells by promoting the intravasation process and subsequent specific interactions between tumor cells and the target lung organ.     

Bone sialoprotein mediates the tumor cell-targeted prometastatic activity of transforming growth factor beta in a mouse model of breast cancer

Transforming growth factor betas (TGF-beta) play a dual role in carcinogenesis, functioning as tumor suppressors early in the process, and then switching to act as prometastatic factors in late-stage disease. We have previously shown that high molecular weight TGF-beta antagonists can suppress metastasis without the predicted toxicities. To address the underlying mechanisms, we have used the 4T1 syngeneic mouse model of metastatic breast cancer. Treatment of mice with a monoclonal anti-TGF-beta antibody (1D11) significantly suppressed metastasis of 4T1 cells to the lungs. When metastatic 4T1 cells were recovered from lungs of 1D11-treated and control mice, the most differentially expressed gene was found to be bone sialoprotein (Bsp). Immunostaining confirmed the loss of Bsp protein in 1D11-treated lung metastases, and TGF-beta was shown to regulate and correlate with Bsp expression in vitro. Functionally, knockdown of Bsp in 4T1 cells reduced the ability of TGF-beta to induce local collagen degradation and invasion in vitro, and treatment with recombinant Bsp protected 4T1 cells from complement-mediated lysis. Finally, suppression of Bsp in 4T1 cells reduced metastasis in vivo. We conclude that Bsp is a plausible mediator of at least some of the tumor cell-targeted prometastatic activity of TGF-beta in this model and that Bsp expression in metastases can be successfully suppressed by systemic treatment with anti-TGF-beta antibodies.     

Carbamoylphosphonate matrix metalloproteinase inhibitors 3: in vivo evaluation of cyclopentylcarbamoylphosphonic acid in experimental metastasis and angiogenesis.

The spread of malignant tumor cells from a primary neoplasm to distant organs where they multiply and form new foci is the major cause of death from cancer. Despite the different modalities of cancer treatment, no effective curative therapy of metastatic lesions is available. To possess metastatic potential, a cell has to be able to invade the surrounding tissue, spread via lymphatics and/or the bloodstream, extravasate, and multiply at secondary sites. There is increasing evidence for a positive correlation between matrix metalloproteinase-2 (MMP-2) activity and tumor cell invasion. Agents blocking MMP-2 have been shown to prevent tumor cell invasion in vitro and in vivo. Inhibition of MMPs has, therefore, become the focus of considerable interest in connection with a variety of potential therapeutic applications. We have discovered a nontoxic MMP-2-selective inhibitor effective at nanomolar range on recombinant MMP. This compound, cyclopentylcarbamoylphosphonic acid, significantly inhibited cellular invasion and capillary formation in vitro. Further, i.p. or oral administration of the compound significantly reduced lung metastasis formation and s.c. tumor growth in a murine melanoma model. The effect of this novel compound on lung colonization, capillary formation, and s.c. tumor growth indicates that the compound might also be effective in treatment of primary tumor growth in reduction, or at least in prevention, of further tumor growth, thereby reducing the tumor burden of the patient by a nontoxic approach.     

Differential influence of organ site on three subpopulations of a single mouse mammary tumor at two distinct steps in metastasis

Tumor subpopulations 66c14, 168FARN, and 4T07 are drug-resistant variants selected from sister subpopulations derived from a single mouse mammary tumor. These subpopulations are heterogeneous in their capacities to form experimental metastatic growth in the lungs and liver. Initial survival kinetics of arrested cells, determined by the clearance of 125IUdR-labelled cells, and subsequent growth rates, determined by sequential recovery of clonogenic tumor cells from occult metastases, both correlated with organ-colonizing potential as determined by necropsy. The growth rates of these 3 subpopulations were determined in vitro in monolayer and in situ in the subcutis, in the liver following intrasplenic injection, and in the lung following intravenous injection. Clonogenic potential of all 3 lines was similar in vitro (54-59%). Growth rates in vitro (population doubling times 16.5-21 hr) and in the subcutis (tumor volume doubling times 5.2-7.4 days) were similar for the 3 subpopulations, but differed significantly in the liver and lungs. For line 4T07, the most metastatic line to both lung and liver, population doubling times in vitro and in the lung and liver were similar, ranging from 17 to 26 hr. For lines 66c14 and 168FARN, the growth rates in lungs and livers were much slower than in vitro. Line 66c14, which is relatively more metastatic to the lungs, grew much faster in the lung (39 hours) than in the liver (91 hr), but line 168FARN, which is relatively more metastatic to the liver, grew at a faster rate in the liver (37 hr) than in the lung (63 hr). Thus, 3 tumor subpopulations (seeds) derived from a single tumor were differentially affected by host organ factors (soil) at 2 distinct stages in the metastatic process.     

Effects of dimethyltriazenes on in vitro Lewis lung carcinoma tumor lines with different metastatic capacity

The effects of a selective antimetastatic agent: the aryldimethyltriazene derivative 1-p-(3,3-dimethyl-1-triazeno)benzoic acid potassium salt (DM-COOK) have been examined on two in vitro tumor cell lines derived from lung metastases of Lewis lung carcinoma. These stabilized in vitro tumor cell lines named C108 and BC215 have been reported to differ in their metastatic potential evaluated as lung colony forming ability and as the number of spontaneous metastases produced after intramuscular implant of tumor cells. The cytotoxic effect of DM-COOK in vitro was also compared with the one demonstrated by the structure-related compound 4-(3,3-dimethyl-1-triazeno)imidazole-5- carboxamide (DTIC) on the same variant lines. Survival curves show a different chemosensitivity of the two in vitro lines to the DM-COOK treatment, whereas no differences were detected between C108 and BC215 after exposure to DTIC. Moreover, DM-COOK and DTIC exhibit different trends of cell killing, implying different mechanisms of action for the two drugs. Results are discussed in view of the selective in vitro action of the aryldimethyltriazene derivative DM-COOK on cells which express a high metastatic potential.