Intravital microscopic characterization of suramin effects in an orthotopic immunocompetent rat model of pancreatic cancer.

OBJECTIVES

We investigated the effect of suramin on tumor growth and spread in an immunocompetent, orthotopic rat model of pancreatic cancer and analyzed the tumor vasculature by intravital microscopy.

METHODS AND METHODS

In vitro, rat ductal pancreatic cancer cells (DSL-6A) were incubated with suramin (10-800 microg/ml), and cell proliferation was assessed. In vivo, DSL-6A tumors were induced in the pancreas of Lewis rats. Animals received suramin (60 mg/kg, weekly i.p.) or the vehicle (controls). Treatment started after 3 days. Intravital microscopy after 1, 4, and 8 weeks quantified diameter, density, and permeability of tumor vessels. Primary tumor volume, local infiltration, and metastatic spread were determined at autopsy. Microvessel density was analyzed by immunohistochemistry.

RESULTS

In vitro, proliferation was inhibited by suramin up to 95%. In vivo, all controls developed extensive tumor growth and spread. No tumor was detectable in half of the suramin-treated animals after 8 weeks; tumor dissemination was almost completely depressed. Suramin therapy resulted in a complete regression of tumor macrovessels and a significant reduction of microvessel density.

CONCLUSION

Suramin significantly reduces primary tumor growth and dissemination in a clinically relevant rat model of pancreatic cancer and seems to play an important role for the inhibition of tumor angiogenesis.