A major problem in the treatment of cancer is the specific targeting of drugs to these abnormal cells. Ideally, such a drug should act over short distances to minimize damage to healthy cells and target subcellular compartments that have the highest sensitivity to the drug. We describe the novel approach of using modular recombinant transporters to target photosensitizers to the nucleus, where their action is most pronounced, of cancer cells overexpressing ErbB1 receptors. We have produced a new generation of the transporters consisting of (a) epidermal growth factor as the internalizable ligand module to ErbB1 receptors, (b) the optimized nuclear localization sequence of SV40 large T-antigen, (c) a translocation domain of diphtheria toxin as an endosomolytic module, and (d) the Escherichia coli hemoglobin-like protein HMP as a carrier module. The modules retained their functions within the transporter chimera: they showed highaffinity interactions with ErbB1 receptors and A/B-importin dimers and formed holes in lipid bilayers at endosomal pH. A photosensitizer conjugated with the transporter produced singlet oxygen and Á OH radicals similar to the free photosensitizer. Photosensitizers-transporter conjugates have >3,000 times greater efficacy than free photosensitizers for target cells and were not photocytotoxic at these concentrations for cells expressing a few ErbB1 receptors per cell, in contrast to free photosensitizers. The different modules of the transporters, which are highly expressed and easily purified to retain full activity of each of the modules, are interchangeable, meaning that they can be tailored for particular applications.

The search for new pharmaceuticals that are specific for diseased rather than normal cells in the case of cancer and viral disease has raised interest in locally acting drugs that act over short distances within the cell and for which different cell compartments have distinct sensitivities. Thus, photosensitizers (PSs) used in anti-cancer therapy should ideally be transported to the most sensitive subcellular compartments in order for their action to be most pronounced. Here we describe the design, production, and characterization of the effects of bacterially expressed modular recombinant transporters for PSs comprising 1) alpha-melanocyte-stimulating hormone as an internalizable, cell-specific ligand; 2) an optimized nuclear localization sequence of the SV40 large T-antigen; 3) an Escherichia coli hemoglobin-like protein as a carrier; and 4) an endosomolytic amphipathic polypeptide, the translocation domain of diphtheria toxin. These modular transporters delivered PSs into the nuclei, the most vulnerable sites for the action of PSs, of murine melanoma cells, but not non-MSH receptor-overexpressing cells, to result in cytotoxic effects several orders of magnitude greater than those of nonmodified PSs. The modular fusion proteins described here for the first time, capable of cell-specific targeting to particular subcellular compartments to increase drug efficacy, represent new pharmaceuticals with general application.

Enhancer-mediated promoter activation is a fundamental mechanism of gene regulation in eukaryotes (10, 44). Recently, sequences in different organisms have been identified that constrain enhancer action. These elements, known as insulators, block communication between an enhancer and promoter only when the insulator is positioned between these regulatory elements. Similarly, insulators prevent silencer interactions with promoters (6,10,30,44,45). The properties of insulators are exemplified by the gypsy insulator that originally was found in the gypsy transposable element (19,24).Genetic and molecular approaches have led to the identification and characterization of three proteins, Suppressor of Hairy wing [Su(Hw)], Mod(mdg4)-67.2, and CP190, that are required for the activity of the gypsy insulator (6, 36). Su(Hw) is a zinc finger protein that binds 12 directly repeated copies of a short sequence motif in the gypsy insulator (9, 42). In addition, Su(Hw) has two acidic domains located at the amino (N) and carboxyl (C) termini of the protein and a C-terminal enhancer-blocking region that is essential for insulation (23, 29). The mod(mdg4) gene, also known as E(var)3-93D, encodes a large set of protein isoforms with specific functions in regulating the chromatin structure of different genes (3). All isoforms encoded by mod(mdg4) contain a BTB/POZ domain and a glutamine-rich (Q) region in the N terminus (3, 7). The BTB (broad complex, tramtrack, bric-a-brac) or POZ (poxvirus and zinc finger) domain identifies a large family of proteins in organisms from yeast to humans (43,47). This domain functions as a protein interaction domain that facilitates homodimer (2, 33, 34) and heterodimer formation as well as oligomerization (11,28,37). One of the mod(mdg4)-encoded protein isoforms, Mod(mdg4)-67.2, interacts with the enhancer-blocking domain of the Su(Hw) protein (12, 20) through a C-terminal acidic domain. This domain is affected in two viable mutations mod(mdg4) u1 and mod(mdg4) T6 (12, 15). The third component of the insulator complex, CP190, also contains a BTB domain (38). It was suggested that Mod(mdg4)-67.2 and CP190 interact through their BTB domains.The mod(mdg4) u1 and mod(mdg4) T6 mutations have varying effects on insulator function, resulting in partial restoration of enhancer-promoter communication in some cases, while transforming the insulator into a silencer in others (4,12,13,14,15,22). The domains of the Mod(mdg4)-67.2 protein required for the insulator and antirepression activity are not determined. Although the essential role of the BTB domain for Mod-(mdg4)-67.2 activity was predicted in the previous studies, this postulate has not been proven (12,20). Here we examined the role of the BTB domain in the functional activities of the Mod(mdg4)-67.2 protein.The structure of the BTB domain has been examined for mammalian transcriptional repressors 34). The high degree of sequence identity between the BTB domains of Mod(mdg4), Bcl-6, and PZLF (1) allowed us to predict key residues of the Mod(mdg4)-67.2 ...

Background: Modular nanotransporters (MNT) are recombinant multifunctional polypeptides created to exploit a cascade of cellular processes, initiated with membrane receptor recognition to deliver selective short-range and highly cytotoxic therapeutics to the cell nucleus. This research was designed for in vivo concept testing for this drug delivery platform using two modular nanotransporters, one targeted to the α-melanocyte-stimulating hormone (αMSH) receptor overexpressed on melanoma cells and the other to the epidermal growth factor (EGF) receptor overexpressed on several cancers, including glioblastoma, and head-and-neck and breast carcinoma cells. Methods: In vivo targeting of the modular nanotransporter was determined by immunofluorescence confocal laser scanning microscopy and by accumulation of 125 I-labeled modular nanotransporters. The in vivo therapeutic effects of the modular nanotransporters were assessed by photodynamic therapy studies, given that the cytotoxicity of photosensitizers is critically dependent on their delivery to the cell nucleus.Results: Immunohistochemical analyses of tumor and neighboring normal tissues of mice injected with multifunctional nanotransporters demonstrated preferential uptake in tumor tissue, particularly in cell nuclei. With 125 I-labeled MNT{αMSH}, optimal tumor:muscle and tumor:skin ratios of 8:1 and 9.8:1, respectively, were observed 3 hours after injection in B16-F1 melanoma-bearing mice. Treatment with bacteriochlorin p-MNT{αMSH} yielded 89%-98% tumor growth inhibition and a two-fold increase in survival for mice with B16-F1 and Cloudman S91 melanomas. Likewise, treatment of A431 human epidermoid carcinoma-bearing mice with chlorin e 6 -MNT{EGF} resulted in 94% tumor growth inhibition compared with free chlorin e 6 , with 75% of animals surviving at 3 months compared with 0% and 20% for untreated and free chlorin e 6 -treated groups, respectively. Conclusion:The multifunctional nanotransporter approach provides a new in vivo functional platform for drug development that could, in principle, be applicable to any combination of cell surface receptor and agent (photosensitizers, oligonucleotides, radionuclides) requiring nuclear delivery to achieve maximum effectiveness.

1. The membrane structure of erythrocytes of rats with different forms of arterial hypertension was studied by means of two hydrophobic fluorescent probes (diphenylhexatriene and pyrene). 2. Microviscosity of hydrophobic areas of erythrocyte membrane of spontaneously hypertensive rats was found to be increased compared with that of membranes from normotensive control rats. 3. No alterations of membrane structure of erythrocytes of deoxycorticosterone-treated rats and renal hypertensive rats were found.

Experiments with human hepatoma PLC/PRF/5 cells and human embryo skin fibroblasts involving the use of three different tests (colony formation, Trypan blue exclusion, labeled thymidine incorporation) have demonstrated a significantly higher photosensitizing activity of chlorin e6 conjugates with internalizable ligands as compared to that of chlorin e6 itself. Receptor-mediated internalization of chlorin e6 conjugates ensures a greater photosensitization of cells than binding of those conjugates to cell surface receptors. The suitability of such conjugates that permit the delivery of a photosensitizer to sensitive intracellular targets is discussed.

Permeability of the erythrocyte membrane for sodium and potassium ions was studied in 8-10-week old spontaneously hypertensive rats (SHR, Kyoto Wistar strain), normotensive Wistar and Sprague-Dawley rats. The rate constnat of Na/Na exchange was considerably greater in the SHR than in the normotensive Wistar and Sprague-Dawley rats. This difference remained the same in the rats adrenalectomized 7 days prior to the experiment. The maximum difference in the constants was found when the sodium pump was blocked by ouabain. The accumulation of 42K in the erythrocytes of the SHR (the sodium pump being blocked) took place at a considerably slower rate, and the K+ washout into a potassium-free medium was faster than in the normotensive Wistar and Sprague-Dawley rats. These results seem to indicate a higher permeability of the SHR's erythrocyte membrane for Na+ and K+ ions, as compared to normotensive Wistar and Sprague-Dawley strains. It is suggested that the increased permeability of the erythrocyte membrane for Na+ and K+ in the SHR may reflect a more widespread cell membrane defect, which could serve as a general cause for activating the mechanisms maintaing high blood pressure.

Cell cycle dynamics and localization of condensins — multiprotein complexes involved in late stages of mitotic chromosome condensation —were studied in Xenopus laevis XL2 cell line. Western blot analysis of synchronized cells showed that the ratio of levels of both pEg7 and XCAP-E to β-tubulin levels remains almost constant from G1 to M phase. pEg7 and XCAP-E were localized to the mitotic chromosomes and were detected in interphase nuclei. Immunostaining for condensins and nucleolar proteins UBF,fibrillarin and B23 revealed that both XCAP-E and pEg7 are localized in the granular component of the nucleolus. Nucleolar labeling of both proteins is preserved in segregated nucleoli after 6 hours of incubation with actinomycin D (5 mg/ml), but the size of the labeled zone was significantly smaller. The data suggest a novel interphase function of condensin subunits in spatial organization of the nucleolus and/or ribosome biogenesis.