Targeted Drug Delivery Utilizing a Mini-Collagen Ligand Recognized by CD44/CSPG Melanoma Receptor

Liposomes of varying lipid compositions are currently used as drug carriers. and
great efforts have been made to target these vehicles to specific cellular receptors.
Previous targeting components include peptides. proteins. antibodies. or vitamins.
CD44/CSPG is among the receptors overexpressed in metastatic melanoma. and the
sequence to which it binds within the type IV collagen triple-helix has been identified. A
triple-helical '·peptide-amphiphile .. (al(JV)1263-1277 PA) which binds CD44/CSPG has
been constructed and incorporated into liposomes of differing lipid compositions.
Liposomes containing distearoyl phosphatidylcholine (DSPC) as the major bilayer
component. in combination with distearoyl phosphatidylglycerol (DSPG) and cholesterol.
were more stable than analogous liposomes containing dipalmitoyl phosphatidylcholine
(DPPC) instead of DSPC. The presence of the al(JV)1263-1277 PA conferred greater
stability to the DPPC liposomal systems. and did not affect the stability of the DSPC
liposomes. The addition of either PEG 750 or PEG 2000 (5 mol %) to DSPG/DSPC/Chol
liposomes did not affect the stability of this system. Fluorophore delivery of rhodamine loaded liposomes to cells varymg 111 CD44/CSPG expresston was determined usmg
fluorescence microscopy. The CD44/CSPG receptor content for two normal fibroblast
cell lines, BJ and Hs895Sk, and a highly metastatic melanoma derived cell line, M 14#5.
was determined using whole cell ELISA. The results of the ELISA showed varying levels
of CD44 receptors amongst the cell lines. with M 14#5 cells having the most. A positive
correlation was observed for cellular fluorophore delivery by the ai(IV)1263-1277 PA
liposomes and CD44/CSPG receptor content. Conversely, non-targeted liposomes
delivered minimal fluorophore to cells regardless of the CD44/CSPG receptor content.
When cells were treated with exogeneous a I (IV) 1263-1277, prior to incubation with
a I (IV) 1263 -1277 PA liposomes, a dose-dependent decrease in the amount of fluorophore
delivered was observed with respect to increasing concentrations of exogeneous
al(IV)1263-1277. In addition, we have found a positive correlation between the
cytotoxic effect of ai(IV)l263-1277 PA targeted liposomes (with and without PEG)
loaded with doxorubicin and the CD44/CSPG content amongst the three different cell
lines. This trend was not observed with non-targeted liposomes. These findings provide
the possibility of a novel drug carrier system to be used in future clinical applications
against metastatic melanoma.