279. Antitumor activity of native and glycated fibrinogen-methotrexate conjugates

Abstract

Introduction and goal of the work Due to increased accumulation in tumors and ability to form stable conjugates with chemotherapy agents, fibrinogen may be used as potential antitumor drug carrier. Various methotrexate conjugates have been tested in our laboratory and they revealed significant antitumor activity but also were highly toxic (Cancer Letters, 2000, 148:189–95). Therefore, we attempted to lower their toxicity and preserve therapeutic efficacy at the same time. New original method of glycated fibrinogen conjugate synthesis has been developed in our laboratory. Conjugates synthesized this way are pure, not cross-linked and have low hydrophobicity. The aim of this work was to investigate their antitumor activity and toxicity in comparison with tree methotrexate. Materials and methods Three-month-old (C57BI/6 × DBA/2) F1 mice were injected with 10^6 leukemia (P388) cells i.p. and 24 hours later each mouse was injected with 40 mg/kg of appropriate agent (D1, i.p.). Three different methotrexate (MTX) conjugates were examined: 1) with native bovine fibrinogen (F-MTX), 2) with fibrinogen glycated at 65°C (F65-MTX) and 3) with fibrinogen glycated at 73°C (F73-MTX). Concentrations of MTX in the studied preparations were: MTX – 1,5 mg/mL, F-MTX – 1,5 mg/mL, F65-MTX – 1,4 mg/mL, F73-MTX – 0,8 mg/mL. Average substitution level of these conjugates approached 11,4. Animals were randomly divided into 5 groups: 1) nontreated control, 2–5) treated respectively with MTX, F-MTX, F65-MTX, and F63-MTX. Results Increase in average life span (ILS) over the control group was: MTX – 34%, F-MTX – 137%, F65-MTX – 151%, F73-MTX – 91%. Conclusions In our preliminary investigations all newly synthesized conjugates (F-MTX, F65-MTX, F73-MTX) revealed higher antitumor activity in vivo in comparison with free methotrexate (P