Background: Recent prospective clinical trials of low molecular weight heparins (LMWHs) have demonstrated that these agents may provide significant advantages in terms of progression-free and overall survival in certain subgroups of cancer patients. The mechanisms of improved survival associated with LMWHs are not known, and may involve direct and/or indirect effects on tumor growth. The purpose of this study was to investigate the effects of LMWH and a sulfated non-anticoagulant LMWH (S-NACH) on tumor chemotherapeutic uptake and chemoresponse.
Materials and methods: LMWH and S-NACH were tested for their ability to reduce tumor growth and tumor-associated angiogenesis using three different in vivo models. Biodistribution studies were undertaken to determine the effect of these agents on uptake of paclitaxel (PACL) and doxorubicin (Dox) by breast cancer tumor xenografts.
Results: LMWH and S-NACH (10 mg/kg s.c. daily) effectively limited tumor growth of human A549 lung adenocarcinoma xenografts in the nude mouse. In an MDA453/LCC6 breast tumor xenograft model, PACL plus S-NACH showed significant (p < 0.01) tumor growth suppression and improved survival when compared to PACL alone. LMWH increased [(124-)I]-PACL uptake into MDA453/LCC6 tumors, with tumor:muscle ratios several fold greater than that of [(124-)I]-PACL alone 24 h post-injection. Similarly, LMWH and S-NACH significantly (p < 0.01) increased the uptake of Dox by 1.5-2 fold in MCF7 Dox-resistant tumor xenografts.
Conclusion: Protocols utilizing adjuvant or neo-adjuvant therapy with LMWH or S-NACH could lead to increased tumor chemo responsiveness, potentially overcoming tumor chemoresistance.