Adenoviruses synergize with nuclear localization signals to enhance nuclear delivery and photodynamic action of internalizable conjugates containing chlorin e(6)

Photosensitizers, molecules that produce active oxygen species upon activat ion by visible light, are currently being used in photodynamic therapy (PDT ) to treat cancer and other conditions, where limitations include normal ce lls and tissue damage and associated side effects, and the fact that cytoto xic effects are largely restricted to the plasma and other peripheral membr anes. In this study, we used insulin-containing conjugates to which variant s of the simian-virus-SV40 large-tumor antigen (T-ag) nuclear localization signal (NLS) were linked in order to target the photosensitizer chlorin e(6 ) to the nucleus, NLSs were included either as peptides coupled co-valently to the carrier bovine serum albumin, or within the coding sequence of beta -galactosidase fusion proteins, The most potent photosensitizing conjugate was the NLS-containing T-ag beta-galactosidase fusion protein (P10)-(chlori n e(6))-insulin, exhibiting an EC50 more than 2400-fold lower than the valu e for free chlorin e(6), and more than 15-fold lower than that of an NLS-de ficient beta-galactosidase(chlorin e(6))-insulin construct, thus demonstrat ing that NLSs can increase the photosensitizing activity of chlorin e(6). A ttenuated adenoviruses were used to increase the nuclear delivery of conjug ates through its endosomal-membrane-disrupting activity. In the case of the NLS-containing P10-conjugate, co-incubation with adenovirus increased the proportion of cells whose nuclear photosensitizing activity was higher than that in the cytoplasm by 2.5-fold. This use of adenoviruses in conjunction with photosensitizers has clear implications for achieving efficient cell- type-specific PDT. (C) 1999 Wiley-Liss, Inc.