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Structure−Function Correlation of Chloroquine and Analogues as Transgene Expression Enhancers in Nonviral Gene Delivery
journal contribution
posted on 2006-11-02, 00:00 authored by Jianjun Cheng, Ryan Zeidan, Swaroop Mishra, Aijie Liu, Suzie H. Pun, Rajan P. Kulkarni, Gregory S. Jensen, Nathalie C. Bellocq, Mark E. DavisTo understand how chloroquine (CQ) enhances transgene expression in polycation-based, nonviral gene
delivery systems, a number of CQ analogues with variations in the aliphatic amino side chain or in the
aromatic ring are synthesized and investigated. Our studies indicate that the aliphatic amino moiety of CQ
is essential to provide increased gene expression. Further, the enhancements are more dramatically affected
by changes to the aromatic ring and are positively correlated to the strength of intercalation between DNA
and the CQ analogues. Quinacrine (QC), a CQ analogue with a fused acridinyl structure that can strongly
intercalate DNA, enhances transfection similarly to CQ at a concentration 10 times lower, while N4-(4-pyridinyl)-N,N1-diethyl-1,4-pentanediamine (CP), a CQ analogue that has a weakly intercalating pyridinyl
ring, shows no effect on gene expression. Subtle change on the 7-substituent of the chloroquine aromatic
structure can also greatly affect the ability of the CQ analogues to enhance transgene expression. Transfection
in the presence of N4-(7-trifluoromethyl-4-quinolinyl)-N1,N1-diethyl-1,4-pentanediamin e (CQ7a) shows
expression efficiency 10 times higher than in the presence of CQ at same concentration, while transfection
in the presence of N4-(4-quinolinyl)-N1,N1-diethyl-1,4-pentanediamine (CQ7b) does not reveal any enhancing
effects on expression. Through a number of comparative studies with CQ and its analogues, we conclude
that there are at least three mechanistic features of CQ that lead to the enhancement in gene expression: (i)
pH buffering in endocytic vesicles, (ii) displacement of polycations from the nucleic acids in polyplexes,
and (iii) alteration of the biophysical properties of the released nucleic acid.