Inhibition of human breast epithelial HBL100 cell proliferation by a dextran derivative (CMDB7): interference with the FGF2 autocrine loop [corrected]

Anticancer Activity of Chitosan, Chitosan Derivatives, and Their Mechanism of Action

Tailoring of chitosan through the involvement of its amino, acetamido, and hydroxy groups can give derivatives of enhanced solubility and remarkable anticancer activity. The general mechanism of such activity is associated with the disturbances in normal functioning of cell cycle, interference to the central dogma of biological system from DNA to RNA to protein or enzymatic synthesis, and the disruption of hormonal path to biosynthesis to inhibit the growth of cancer cells. Both chitosan and its various derivatives have been reported to selectively permeate through the cancer cell membranes and show anticancer activity through the cellular enzymatic, antiangiogenic, immunoenhancing, antioxidant defense mechanism, and apoptotic pathways. They get sequestered from noncancer cells and provide their enhanced bioavailability in cancer cells in a sustained release manner. This review presents the putative mechanisms of anticancer activity of chitosan and mechanistic approaches of structure activity relation upon the modification of chitosan through functionalization, complex formation, and graft copolymerization to give different derivatives.

Retention of transforming growth factor beta1 using functionalized dextran-based hydrogels

Functionalized dextrans (FD) are anionic water-soluble polymers bearing carboxylate, benzylamide and sulfate groups, which exhibit binding capacity to transforming growth factor-beta1 (TGF-beta1). In this paper, we have investigated the ability of dextran-based hydrogels containing FD, to bind and release recombinant human TGF-beta1. Hydrogels were prepared by chemical crosslink native dextran and FD with sodium trimetaphosphate in 1m NaOH at 50 degrees C. A wide range of hydrogels were prepared as particles ranging of 1-1.6mm of diameter and characterized with various amounts of FD and with different crosslinker feeding ratios (CFR). Dried particles were soaked with recombinant human transforming growth factor-beta1 (rhTGF-beta1) to determine their capacity to deliver the growth factor. Results indicated that the in vitro kinetics releases of rhTGF-beta1 were related to FD and CFR. Retention capacity of rhTGF-beta1 increases with an increase of negative charges of the matrices brought by both phosphate linkages and FD as demonstrated by an additional release of growth factor in high ionic strength solution. Highly crosslinked hydrogels that contained the highest amount of FD (18% (w/w)) retained up to 88% of rhTGF-beta1. Bioactivity of released growth factor was confirmed in a cell assay. These functionalized hydrogels may have important uses for the stabilization and the protection of rhTGF-beta1 as entrapment systems and could be applied to other proteins of clinical interest.

Cytostatic and pro-apoptotic effects of a novel phenylacetate–dextran derivative (NaPaC) on breast cancer cells in interactions with endothelial cells

We have tested a novel hybrid molecule made of carboxymethylbenzylamide dextran (CMDB) and sodium phenylacetate (NaPa) groups, called the CMDB-NaPa ester (NaPaC), on the proliferation of breast cancer and endothelial cells as well as paracrine effects between these two cell types. Our results showed that NaPaC inhibited the proliferation of MDA-MB-231 cells and MCF-7 cells in a dose-dependent manner. NaPaC was 20-fold more active on highly invasive MDA-MB-231 cells than the NaPa parental molecule. On MCF-7 cells, which present a less aggressive phenotype, NaPaC was only 3-fold more active than the NaPa parental molecule. Furthermore, NaPaC had only a slight effect on the proliferation of primary cultured endothelial cells (HUVEC). A cytostatic effect of NaPaC on tumor cells was observed with cells accumulating in G0/G1 phase after 96 h of treatment. In addition, NaPaC induced a strong apoptotic effect on the two breast cancer cell lines. Conditioned media (CM) from tumor cells inhibited HUVEC proliferation, and this effect was enhanced in the presence of NaPaC (6 mM) and NaPa (10 mM). In addition to this cytostatic effect, CM from tumor cells induced a HUVEC early apoptosis which was increased, mainly, in the presence of NaPa (15 mM). Thus, this study shows that NaPaC is a more powerful anti-proliferative molecule than its parental NaPa molecule, with cytostatic and pro-apoptotic effects on MDA-MB-231 and MCF-7 tumor cells. Also, both molecules increased a pro-apoptotic effect of tumor cells on HUVEC.

Carboxymethyl benzylamide dextran inhibits angiogenesis and growth of VEGF-overexpressing human epidermoid carcinoma xenograft in nude mice

Vascular endothelial growth factor (VEGF) expression is elevated in a wide variety of solid tumours. Inhibition of VEGF activities is able to reduce angiogenesis and tumour growth. We have recently shown in vitro that carboxymethyl dextran benzylamide (CMDB7) prevents the binding of VEGF(165) to its cell surface receptors and thus inhibits VEGF activities on endothelial cells. In the present study, we explored the effects of CMDB7 on highly aggressive human epidermoid carcinoma A431 cells known to overexpress epidermal growth factor receptors (EGFRs) and produce a high amount of VEGF and a minor quantity of bFGF. In vitro, CMDB7 blocked the mitogenic activity of A431-conditioned medium on endothelial cells. Concerning A431 cells, CMDB7 inhibited their proliferation and the VEGF(165) binding to them. In vivo, administration of CMDB7 (10 mg kg(-1)) three times per week for 2 weeks inhibited the growth of A431 xenografts in nude mice by 73% as compared to the control group. Immunostaining of endothelial cells with mouse-specific GSL-1 lectin in tumour sections revealed that CMDB7 also inhibited the density of intratumour endothelial cells by 66%. These findings demonstrate that CMDB7 has an efficient antiangiogenic and antitumour action in vivo even when tumour cells produce a high level of VEGF and EGFRs.

Aponecrotic, antiangiogenic and antiproliferative effects of a novel dextran derivative on breast cancer growth in vitro and in vivo

1. Since the sodium phenylacetate (NaPa) was reported to enhance the inhibitory effect of carboxymethyl benzylamide dextran (CMDB) on the breast cancer growth, we performed the esterification of CMDB with NaPa to obtain a new drug carrying the characteristics of these two components. A new molecule, phenylacetate carboxymethyl benzylamide dextran, was named NaPaC. 2. We investigated in vitro and in vivo the effects of NaPaC on MCF-7ras cell growth as well as its apoptotic and antiangiogenic effects in comparison to NaPa and CMDB. In addition, we assessed in vitro the antiproliferative effects of these drugs on other breast cancer cells, including MDA-MB-231, MDA-MB-435 and MCF-7. 3. In vitro, NaPaC inhibited MCF-7ras cell proliferation by 40% at concentration lower than that of CMDB and NaPa (12 microM vs 73 microM and 10 mM). IC(50)s were 6 and 28 microM for NaPaC and CMDB, respectively. The similar results were obtained for three other breast cancer cell lines. NaPaC reduced the DNA replication and induced cell recruitment in G(0)/G(1) phase more efficiently than its components. Moreover, it induced a cell death at concentration 1000-fold lower than NaPa. 4. In vivo, CMDB (150 mg kg(-1)) and NaPa (40 mg kg(-1)) inhibited the MCF-7ras tumour growth by 37 and 57%, respectively, whereas NaPaC (15 mg kg(-1)) decreased tumour growth by 66% without toxicity. 5. NaPa or CMDB reduced the microvessel number in tumour by 50% after 7 weeks of treatment. NaPaC had the same effect after only 2 weeks. After 7 weeks, it generated a large necrosis area without detectable microvessels. In vitro, NaPaC inhibited human endothelial cell proliferation more efficiently than CMDB or NaPa. NaPaC interacts with vascular endothelial growth factor as observed by affinity electrophoresis. 6. NaPaC acts like NaPa and CMDB but in more potent manner than components used separately. Its antiproliferative, aponecrotic and anti-angiogenic actions make it a good candidate for a new anti-cancer drug.

Heparin and non-heparin-like dextrans differentially modulate endothelial cell proliferation: in vitro evaluation with soluble and crosslinked polysaccharide matrices

Proliferation of endothelial cells (ECs) is a cellular step of particular importance for implanted cardiovascular biomaterials. Heparin and some synthetic water-soluble non-anticoagulant polysaccharides derived from dextran and bearing anionic carboxymethyl and hydrophobic benzylamine groups were first investigated for their effects on EC proliferation in vitro. The results assessed by cell counting, 3H-thymidine uptake, and flow cytometry analysis, showed that the derivatized dextran-bearing hydrophobic groups stimulated the EC growth in the presence of serum, whereas native dextran or dextran-bearing anionic carboxymethyl groups were inactive and heparin was slightly inhibitory. Then, we showed that the derivatized dextran enhanced EC proliferation by potentiation of the mitogenic activities of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2), two potent EC growth factors. In the presence of 2 nM of derivatized dextran, a 3-fold and 13-fold increase of 3H-thymidine uptake was obtained with VEGF and FGF-2, respectively. Finally, proliferation of ECs was investigated on crosslinked gels made of polysaccharides. It is of interest that EC proliferation was higher on gels containing the derivatized dextran than on plain hydrogels, and heparinized gels inhibited cell proliferation. From the obtained results, we propose that the synthetic non-heparin-like dextran may be of interest as a coating for the endothelialization of cardiovascular biomaterials.

Growth inhibition of human melanoma tumor cells by the combination of sodium phenylacetate (NaPA) and substituted dextrans and one NaPA-dextran conjugate

We have studied the cytostatic effects of sodium phenylacetate (NaPA) in association with several substituted dextrans on human tumor melanoma 1205LU cells. We show that NaPA alone inhibits the growth of these cells (IC50 = 3.9 mM) while a weak inhibitory effect appears at a concentration of 37 microM (10 microg/ml) for a dextran methyl carboxylate benzylamide (LS17-DMCB). The precursors of LS17-DMCB [T40 Dextran and carboxymethyl dextran (LS17-DMC)] did not affect the growth of 1205LU cells. To potentiate the inhibitory activity of NaPA at low concentrations (below 5.6 mM), we have tested NaPA and LS17-DMCB in physical mixture (association) or linked together covalently (this conjugate is termed 'LS17-NaPaC'). We have observed an increase of the 1205LU cell growth inhibition effect with NaPA in association (IC50 1.8 mM). For a concentration of 5 mM of NaPA (free in the case of association or linked in the case of conjugate), the association with dextran derivative exhibits a 4.6-fold higher efficacy than with NaPA alone (9 versus 41% surviving fraction), while the conjugate is 1.3-fold smaller (52% growth inhibition). By performing isobologram analysis of the IC50 data, we have shown a synergistic effect for a particular molar ratio of NaPA and LS17-DMCB (NaPA:LS17-DMCB = 0.35).

Vascular endothelial growth factor 165 (VEGF(165)) activities are inhibited by carboxymethyl benzylamide dextran that competes for heparin binding to VEGF(165) and VEGF(165).KDR Complexes

We have previously shown that carboxymethyl dextran benzylamide (CMDB7), a heparin-like molecule, inhibits the growth of tumors xenografted in nude mice, angiogenesis, and metastasis by altering the binding of angiogenic growth factors, including platelet-derived growth factor, transforming growth factor beta, and fibroblast growth factor 2, to their specific receptors. In this study, we explore the effect of CMDB7 on the most specific angiogenic growth factor, vascular endothelial growth factor 165 (VEGF(165)). We demonstrate here that CMDB7 inhibits the mitogenic effect of VEGF(165) on human umbilical vein endothelial cells (HUV-ECs) by preventing the VEGF(165)-induced VEGF receptor-2 (KDR) autophosphorylation and consequently a specific intracellular signaling. In competition experiments, the binding of (125)I-VEGF(165) to HUV-ECs is inhibited by CMDB7 with an IC(50) of 2 microm. Accordingly, CMDB7 inhibits the cross-linking of (125)I-VEGF(165) to the surface of HUV-ECs, causing the disappearance of both labeled complexes, 170-180 and 240-250 kDa. We show that CMDB7 increases the electrophoretic mobility of VEGF(165), thus evidencing formation of a stable complex with this factor. Moreover, CMDB7 reduces the (125)I-VEGF(165) binding to coated heparin-albumin and prevents a heparin-induced increase in iodinated VEGF(165) binding to soluble (125)I-KDR-Fc chimera. Concerning KDR, CMDB7 has no effect on (125)I-KDR-Fc electrophoretic migration and does not affect labeled KDR-Fc binding to coated heparin-albumin. In the presence of VEGF(165), (125)I-KDR-Fc binding to heparin is enhanced, and under these conditions, CMDB7 interferes with KDR binding. These data indicate that CMDB7 effectively inhibits the VEGF(165) activities by interfering with heparin binding to VEGF(165) and VEGF(165).KDR complexes but not by direct interactions with KDR.

Sodium phenylacetate enhances the inhibitory effect of dextran derivative on breast cancer cell growth in vitro and in nude mice

Sodium phenylacetate (NaPa) and carboxymethyl benzylamide dextran derivative (CMDB(LS4)) are able to inhibit growth of breast tumour cells. In this study, we explored whether the combination of NaPa and CMDB(LS4)may enhance their respective inhibitory effects on the MCF-7ras cell growth in vitro and in vivo. NaPa inhibited MCF-7ras cell proliferation by reducing the DNA replication concomitantly with a recruitment of cells in G0/G1 phase and by inducing apoptosis in a dose- and time-dependent manner. The addition of CMDB(LS4)potentiated the NaPa antiproliferative effect in the manner dependent on the ratio of CMDB(LS4)and NaPa concentrations. In nude mice, CMDB(LS4)(150 mg kg(-1)) or NaPa (40 mg kg(-1)) administrated twice a week, for 7 weeks inhibited MCF-7ras xenograft growth by 40% and 60%, respectively. The treatment by both, CMDB(LS4)and NaPa, decreased tumour growth by 83% without any toxicity. To better understand the mechanism of NaPa and CMDB(LS4)action we assessed their effect on mitogenic activity of MCF-7ras conditioned medium (CM) on BALBC/3T3 fibroblasts. CMDB(LS4)added to the CM, inhibited its mitogenic activity whereas NaPa had an anti-mitogenic effect when CM was prepared from MCF-7ras cells pretreated with NaPa. Thus, the antiproliferative effects of NaPa and CMDB(LS4)involve 2 different mechanisms explaining, at least in part, the possible synergism between them. Overall, this study points to the potential use of a combination of dextran derivatives with NaPa to inhibit the breast tumour growth.

Low-molecular-weight dextran derivatives (f-CMDB) enter the nucleus and are better cell-growth inhibitors compared with parent CMDB polymers

Carboxymethyldextrans-benzylamide (CMDB) are dextran derivatives that are statistically substituted with carboxymethyl and benzylamide groups. These molecules display a variety of biological effects, one of which is their inhibitory activity against mammary tumor cell growth, both in vitro and in vivo. We and others have previously shown that the effects of CMDB on cell growth are related to their ability to interact with the growth factor FGF-2. The binding modifies the conformation of FGF-2, leading to the suppression of its mitogenic activity. Here, the method previously reported to fragment natural polysaccharide fucans has been applied to CMDB (80,000 g/mol). f-CMDB (fragmented CMDB) of molecular weights from 6000 to 20,000 g/mol were found to be more potent inhibitors of MCF7 mammary tumor cell growth than high-molecular-weight CMDB. Confocal microscopy experiments using CMDB and f-CMDB labeled with the fluorophore DTAF (5-([4,6-dichlorotriazine-2-yl]amino) fluorescein) indicate that only low-molecular-weight f-CMDB penetrate into the nucleus of MCF7 cells. It is thus assumed that the better inhibitory properties demonstrated by f-CMDB, compared with CMDB, are related to their better ability to penetrate the nucleus and interact with nuclear targets, including topoisomerase II. The DNA relaxation properties of the latter are inhibited in vitro by both CMDB and f-CMDB. These findings could help us to develop models of low-molecular-weight oligosaccharide derivatives exhibiting better antiproliferative and antitumor properties.

Carboxymethyl benzylamide sulfonate dextrans (CMDBS), a family of biospecific polymers endowed with numerous biological properties: a review

The functionalized dextrans termed carboxymethyl benzylamide sulfonate dextran (CMDBS) represent a family encompassing a wide range of polymers. These soluble macromolecular compounds, which are substituted with specific chemical functional groups, are designed to interact with living systems. By analogy with glycosaminoglycan heparin, a natural highly charged anionic polysaccharide that exerts a variety of biological effects, we postulated that CMDBS compounds also possess binding sites capable of specific interactions with biological constituents, depending on the overall composition of the polymer. The synthesis and heparin-like properties of these CMDBS have been extensively investigated. Thus, it appears that dextran derivatives can mimic the action of heparin in regard to its interactions with antithrombin and serine proteases involved in blood coagulation. Other derivatives interact with various components of the immune system or with adhesive proteins such as fibronectin in modulating the proliferation of Staphylococcus aureus. Because they are able to stimulate wound healing in various in vivo models, these polysaccharides may also constitute a family of tissue repair agents because of their protecting and potentiating effects with heparin binding growth factors. Moreover, dextran derivatives in contact with cells such as endothelial cells, smooth muscle cells, or tumoral cells can affect both cell proliferation and metabolism. It appears that these bioactive polymers are also efficient tools to investigate the precise mechanism of action of individual biological activities by contrasting their mode of action to that of heparin. In addition to their numerous biological properties and biospecificity, functionalized dextrans are relatively simple to manufacture and exempt of donor contaminant, which make them attractive in a variety of clinical applications.

Effects of the binding of a dextran derivative on fibroblast growth factor 2: secondary structure and receptor-binding studies

CMDB (carboxymethyldextran-benzylamide) are dextrans statistically substituted with carboxymethyl and benzylamide groups which can mimick some of the biological properties of heparin. It has previously been shown that CMDB inhibit autocrine growth of breast tumor cells (Bagheri-Yarmand et al., Biochem. Biophys. Res. Commun. 239: 424-428, 1997) and selectively displace fibroblast growth factor 2 (FGF-2) from its receptor. Here, we used circular dichroism and fluorescence anisotropy measurements to show that the conformation of FGF-2 was significantly altered upon its binding to CMDB and to short CMDB fragments prepared within this study. CMDB and fragments formed a stable 1:1 complex with FGF-2, with affinities being estimated as 20+/-10 nM from fluorescence anisotropy analysis. No such a complex was formed with insulin-like growth factor (IGF-1) or epidermal growth factor (EGF). CMDB competed with the FGF-2 receptor for binding to FGF-2 but did not disturb the binding of IGF-1 and EGF to their receptors. Thus, our results highlight the selectivity of CMDB and their fragments towards FGF-2. Heparin, however, competes with CMDB and their fragments for binding to FGF-2. The carboxymethyl and benzylamide groups of these molecules likely interact directly with a heparin-binding region of FGF-2. The resulting change in conformation disturbs the binding of FGF-2 to its receptor and consecutively its mitogenic activity.

Suppression of the neoplastic phenotype by transfection of phospholipase C beta 3 to neuroendocrine tumor cells

The expression of phospholipase C beta 3 (PLCB3) is low or absent in several neuroendocrine neoplasias. To investigate the role of PLCB3 in the neuroendocrine tumorigenesis, we transfected a PLCB3 construct to three neuroendocrine tumor cell lines with a low PLCB3 expression. The growth rate and tumorigenicity were assessed in vitro by [3H]thymidine incorporation and cell counting, in vivo, by xenografting to nude mice. In vitro, PLCB3 expressing clones showed a significant growth inhibition. The tumor weight was reduced for one of the two xenografted PLCB3-transfected cell lines and in both, a reduced number of proliferating (Ki-67 positive) cells was observed. This study implies an essential role for PLCB3 in the neuroendocrine tumorigenesis.

In vivo and in vitro evidence of basic fibroblast growth factor action in mouse mammary gland development

Basic fibroblast growth factor (bFGF) stimulated [3H]thymidine incorporation at all stages of development, although the magnitude of this effect was the greatest in cells derived from pregnant mice. Cells primed with insulin and bFGF synthesized more casein than cells not exposed to either hormone. bFGF inhibited casein synthesis and decreased the amounts of beta-casein and alpha-lactalbumin transcripts in cells from pregnant animals simultaneously incubated with insulin, hydrocortisone and prolactin. bFGF content in mammary gland increased with puberty and pregnancy, but decreased markedly in lactation; the number of bFGF receptors in epithelial cells changed in parallel. These data suggest that bFGF may have a physiological role both in stimulating growth and in inhibiting functional differentiation of normal mouse mammary epithelial cells.

The suppression of fibroblast growth factor 2/fibroblast growth factor 4-dependent tumour angiogenesis and growth by the anti-growth factor activity of dextran derivative (CMDB7)

Our previous studies showed that carboxymethyl benzylamide dextran (CMDB7) blocks basic fibroblast growth factor (FGF-2)-dependent cell proliferation of a human breast epithelial line (HBL100), suggesting its potential role as a potent antiangiogenic substance. The derived cell line (HH9), which was transformed with the hst/FGF4 gene, has been shown to be highly proliferative in vitro and to induce angiogenic tumours in nude mice. We show here that CMDB7 inhibits the mitogenic activities of the conditioned media from HBL 100 and HH9 cells in a dose-dependent manner. When HH9 cells were injected s.c. into nude mice, CMDB7 treatment (300 mg kg(-1) week(-1)) suppressed the tumour take and the tumour growth by about 50% and 80% respectively. Immunohistochemical analysis showed a highly significant decrease, by more than threefold, in the endothelial density of viable tumour regions, together with a significant increase in the necrosis area. This antiangiogenic activity of CMDB7 was further demonstrated by direct inhibition of calf pulmonary artery (CPAE) and human umbilical vein (HUVEC) endothelial cell proliferation and migration in vitro. In addition, we showed that CMDB7 inhibits specifically the mitogenic effects of the growth factors that bind to heparin such as FGF-2, FGF-4, platelet-derived growth factor (PDGF-BB) and transforming growth factor (TGF-beta1), but not those of epidermal growth factor (EGF) and insulin-like growth factor (IGF-1). These results demonstrate that CMDB7 inhibits FGF-2/FGF-4-dependent tumour growth and angiogenesis, most likely by disrupting the autocrine and paracrine effects of growth factors released from the tumour cells.