Suramin-induced neutropenia

Suramin inhibits hepatic tissue damage in hepatocellular carcinoma through deactivation of heparanase enzyme

Hepatocellular carcinoma (HCC) is resistant to conventional chemotherapy, and is rarely amenable to radiotherapy. Heparanase, enzyme attacks heparan sulfate proteoglycans (HSPGs), is preferentially expressed in human tumors and its overexpression in low-metastatic tumor confers a highly invasive phenotype in experimental animals. Meanwhile, high doses of suramin dramatically increase tissue glycosaminoglycans due, in part, to inhibition of heparanase enzymes. Therefore, the following study was conducted to evaluate the chemopreventive and hepatoprotective effects of suramin in in-vivo model of HCC. Therefore, HCC was induced in SD rats by thioacetamide (200mg/kg) in presence/absence of suramin (20mg/kg). Liver impairment was assessed by measuring serum α-fetoprotein and investigating liver sections stained with Hematoxylin/Eosin. Hepatic HSPGs and heparanse were measured by ELISA. Glucosamine and glucuronic acid were measured by chemical methods. Gene expression of fibroblast growth factor (FGF)-2 and caspase-3 was measured. Apoptotic pathway was evaluated by measuring the activity of caspase-3/8/9. Suramin increased the animal survival and decreased serum α-fetoprotein. In addition, suramin ameliorated fibrosis and massive hepatic tissue breakdown. Suramin restored hepatic HSPGs and reduced the activity of hepatic heparanase leading to decreased hepatic levels of glucosamine and glucuronic acid. Moreover, suramin reduced the gene expression of FGF-2 and caspase-3. Finally, suramin blocked the elevated activity of caspase-3/8/9. In conclusion, surmain showed antitumor activity as well as hepatoprotective effects. Besides its antioxidant activity, other mechanisms are involved including restoration of HSPGs and inhibition of heparanase and FGF-2. Suramin inhibits intrinsic and extrinsic apoptotic pathway. Targeting HSPGs expression is potential therapeutic target for HCC.

Improved muscle healing after contusion injury by the inhibitory effect of suramin on myostatin, a negative regulator of muscle growth

BACKGROUND

Muscle contusions are the most common muscle injuries in sports medicine. Although these injuries are capable of healing, incomplete functional recovery often occurs.

HYPOTHESIS

Suramin enhances muscle healing by both stimulating muscle regeneration and preventing fibrosis in contused skeletal muscle.

STUDY DESIGN

Controlled laboratory study.

METHODS

In vitro: Myoblasts (C2C12 cells) and muscle-derived stem cells (MDSCs) were cultured with suramin, and the potential of suramin to induce their differentiation was evaluated. Furthermore, MDSCs were cocultured with suramin and myostatin (MSTN) to monitor the capability of suramin to neutralize the effect of MSTN. In vivo: Varying concentrations of suramin were injected in the tibialis anterior muscle of mice 2 weeks after muscle contusion injury. Muscle regeneration and scar tissue formation were evaluated by histologic analysis and functional recovery was measured by physiologic testing

RESULTS

In vitro: Suramin stimulated the differentiation of myoblasts and MDSCs in a dose-dependent manner. Moreover, suramin neutralized the inhibitory effect of MSTN on MDSC differentiation. In vivo: Suramin treatment significantly promoted muscle regeneration, decreased fibrosis formation, reduced myostatin expression in injured muscle, and increased muscle strength after contusion injury.

CONCLUSION

Intramuscular injection of suramin after a contusion injury improved overall skeletal muscle healing. Suramin enhanced myoblast and MDSC differentiation and neutralized MSTN's negative effect on myogenic differentiation in vitro, which suggests a possible mechanism for the beneficial effects that this pharmacologic agent exhibits in vivo.

CLINICAL RELEVANCE

These findings could contribute to the development of biological treatments to aid in muscle healing after experiencing a muscle injury.

Suramin inhibits proliferation of human arterial smooth muscle cells in vitro: potential drug for prevention of restenosis by local drug delivery

PURPOSE

Suramin is known to inhibit proliferation of various tumor cells. This study was performed to investigate the effect of suramin on proliferating human arterial smooth muscle cells (HASMC) and thus to examine its suitability for the prevention of restenosis.

METHOD

Proliferation of HASMC was stimulated with human whole blood serum (HWBS), as well as with platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). Proliferation was assessed by measuring DNA synthesis and cell viability was assessed by measuring mitochondrial activity.

RESULTS

Suramin exerted a strong attenuating effect on the proliferation stimulators HWBS, PDGF, and bFGF. A suramin concentration of 0.5 mmol/L, which is approximately twice the dosage used for systemic application, was sufficient for complete neutralization of proliferation stimulation by 10% HWBS added to the cell culture medium.

CONCLUSION

The authors' data demonstrate a strong proliferation inhibiting effect of suramin on HASMC in vitro. Because it is known to interact not only with one but with a multitude of relevant growth factors, these results make suramin a most interesting substance for local application for prevention of hyperplastic neointima formation.

Targeting human prostatic carcinoma through basic fibroblast growth factor receptors in an animal model: characterizing and circumventing mechanisms of tumor resistance

BACKGROUND

Basic fibroblast growth factor receptors on DU145 human prostatic carcinoma xenografts serve as targets for the delivery of a growth factor-toxin chimera, basic fibroblast growth factor-saporin (bFGF-SAP), which produces significant antitumor activity in a nude mouse model. However, DU145 tumors often become resistant to prolonged treatment.

METHODS

Nude mice bearing DU145 xenografts were intravenously administered bFGF-SAP (0.05 microg/kg weekly for 4 weeks), and a panel of eight tumors was isolated from the treated animals and established in monolayer culture.

RESULTS

In cell-survival assays, sensitivity of the treated tumor-derived cell lines to bFGF-SAP (IC50 = 12-100 nM) varied widely from cells derived from a vehicle-treated control tumor (IC50 = 10 nM). A significant inverse correlation was observed between increased IC50 values in vitro and increased tumor growth delay in vivo. Pretreatment of tumor cells with suramin or neutralizing antibodies to bFGF or keratinocyte growth factor (KGF) circumvented resistance in one of the tumor lines, confirming autocrine-mediated resistance. In another tumor subline, a 3-fold decrease in bFGF high-affinity receptor sites, which concurred with a 4-fold decrease in ability to internalize the bFGF ligand, was consistent with a decrease in total cellular expression of the FGF2 receptor (Bek). Resistance was circumvented by alternatively targeting FGF1 receptor (Flg) on these cells with a saporin immunotoxin.

CONCLUSIONS

These studies identify alterations in the ligand-targeted receptor as a frequent contributor to resistance arising in DU145 tumors to in vivo treatment with a bFGF receptor-directed-toxin chimera, and provide the basis for designing methods to circumvent resistance for the purpose of enhancing efficacy of receptor-directed therapies in the treatment of prostate cancer.