A branched histidine/lysine peptide, H2K4b, in complex with plasmids encoding antitumor proteins inhibits tumor xenografts.
BACKGROUND
In this study we investigated whether a particular branched HK polymer, H2K4b, was an effective in vivo carrier of plasmids expressing the antiangiogenic kringle 1-5 or the tumor suppressor p53.


METHODS
H2K4b was synthesized on a solid-phase peptide synthesizer. Distribution, optimization and time course studies were done in tumor-bearing nude mice by systemically administering H2K4b in complex with a luciferase-expressing plasmid. We examined the amount of tumor angiogenesis in C6 with MDA-MB-435 xenografts utilizing the carmine dye. The ability of H2K4b to carry luciferase plasmids to different tissues was compared with several liposomal carriers. Medium from cells transfected with mKr1-5 was tested for its capacity to inhibit angiogenesis with an in vivo Matrigel assay. We then determined if systemically delivered H2K4b in complex with plasmid encoding mKr1-5 inhibited tumor growth; we also compared the antitumor activity of HK polyplexes containing hKr1-5, mKr1-5, and p53 plasmids.


RESULTS
H2K4b carried the luciferase-expressing plasmid in order of descending efficacy to these tissues: lung, spleen, tumor, and liver. Compared to DOTAP-containing liposomes, H2K4b was a more effective carrier of a luciferase-containing plasmid to extrapulmonary tissues. We then determined that mKr1-5 in complex with H2K4b reduced MDA-MB-435 tumor growth by approximately 50% compared to the control group (P < 0.01). Similarly, H2K4b/mKr1-5 polyplexes reduced the growth of C6 xenografts. In MDA-MB-435 xenografts, p53- and Kr1-5-expressing plasmids in complex with H2K4b had comparable antitumor activity.


CONCLUSIONS
H2K4b demonstrates potential as a carrier of plasmids encoding antiangiogenic and/or tumor suppressor proteins in a tumor-bearing mouse model.
Leng
Qixin
Q
Department of Pathology, University of Maryland Baltimore, MSTF Building, 10 South Pine Street, Baltimore, MD 21201, USA.
Scaria
Puthupparampil
P
Ioffe
Olga B
OB
Woodle
Martin
M
Mixson
A James
AJ
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000378:metabolism / Q000628:therapy*; D045744:Cell Line, Tumor; D005260:Female; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D010455:Peptides / Q000008:administration & dosage*; D010957:Plasmids / Q000008:administration & dosage* / Q000235:genetics*; D013997:Time Factors; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; C497834:H2K4bT protein; D010455:Peptides; D008156:Luciferases