Purpose: To study the feasibility of Leucine-Aspartic Acid-Valine (LDV) as targeting ligand and drug carrier for targeted delivery to integrin alpha(4)beta(1) over-expressing cancer cells.
Methods: Poly(L,D,V) was randomly copolymerized using N-carboxyanhydrides of leucine, beta-benzyl-aspartic acid, and valine. Oligo(LDV), consisting of 2-6 LDV units, were synthesized by solid phase protein synthesis (SPPS) method. Binding of Leu-Asp-Val, Val-Asp-Leu, and Leu-Asn-Val, and internalization of FITC labeled LDV by wild-type and integrin alpha(4) knock-down A375 cells were studied. Cytotoxicity of poly(L,D,V)-Dox, oligo(LDV)-Dox, and doxorubicin (Dox) was also determined on wild-type, integrin alpha(4) knock-down A375 cells, and normal human epithelial keratinocytes (NHEK).
Results: LDV was essential for the specific binding and internalization by cells expressing integrin alpha(4)beta(1). Cytotoxicity of poly(L,D,V)-Dox and oligo(LDV)-Dox was integrin alpha(4)-dependent, while free Dox did not show this differential effect. No observable cytotoxicity trend was found when increasing LDV repeating unit. Poly(L,D,V) was relatively more effective than oligo(LDV) for the delivery of Dox to A375.
Conclusion: LDV containing moieties bind specifically to integrin alpha(4)beta(1) expressing cancer cells. The binding, internalization, and cytotoxicity depend on the level of integrin alpha(4)beta(1) expression. Poly(L,D,V) and oligo(LDV) were both effective in the in vitro targeted delivery of Dox to integrin alpha(4)beta(1) over-expressing A375 cells.