Medical applications of peptide libraries: Immunomics and siRNA targeting to cancer cells
Targeting siRNA to cancer cells
The major challenge of cancer therapy is to direct therapeutics to tumour cells.Targeted therapy can significantly reduce the amount of agents needed and, as a consequence, lessen the potential toxicity to non targeted cells. By using cancer cell-binding peptides and cancer cell-specific promoters, we show that specific delivery and/or expression of siRNA in cancer cells is possible. macrophage-produced TNF aplha.
The discovery that double-stranded RNA (dsRNA) molecules of 21-23 nt (short interfering RNAs, siRNAs) can silence targeted genes through sequence-specific cleavage of the cognate RNA transcript has led to the rapid adaptation of this technology for the analysis of gene function. The technique has also the potential to be developed into human therapeutics. However, this approach has a major limitation: inhibition cannot be controlled in a time- or tissue specific manner. Furthermore, constitutive expression of siRNAs can affect cytoplasmic transport of microRNAs, a class of small non-coding RNAs with important biological role. Therefore, the therapeutic applications of RNAi in human cancers require either the specific delivery synthetic siRNAs into cancer cells or the control of siRNA expression. In this project, we have explored the possibility of conjugating siRNAs to synthetic peptides that recognize specific receptors expressed by cancer cells but not normal cells.
In addition to targeting peptides selected from peptide libraries, we show that it is possible to restrict siRNA expression to cancer cells by placing the siRNA under the control of a promoter taken from a gene selectively expressed in cancer cells. In this, respect, we have modified the survivin promoter to express shRNAs that can silence gene expression in cancer cells but not normal cells.
Notably, the interplay between malignant and stromal cells is essential in tumorigenesis. We have previously shown that colony-stimulating factor (CSF)-1, matrix metalloprotease (MMP)-2, and vascular endothelial growth factor (VEGF)-A production by stromal cells is enhanced by CSF-1-negative SW620 colon cancer cells. Using siRNAs, we have investigated the mechanisms by which colon cancer cells up-regulate host factors to promote tumorigenesis, we show that that colon cancer cell-derived TNF-alpha stimulates TNF-alpha and CSF-1 production by macrophages, and that CSF-1, in turn, induces macrophage VEGF-A and MMP-2 in an autocrine manner. Thus, interrupting tumor cell-macrophage communication by targeting TNF-alpha may provide an alternative therapeutic approach for the treatment of colon cancer.
Suppression of immunostimulatory siRNA-driven innate immune activation by 2'-modified RNAs.
Biochem Biophys Res Commun 2007 Sep;361(1):122-6. Epub 2007 jul 16
Colon cancer cell-derived tumor necrosis factor-alpha mediates the tumor growth-promoting response in macrophages by up-regulating the colony-stimulating factor-1 pathway.
Cancer Res 2007 Feb;67(3):1038-45.
Transcriptional targeting of small interfering RNAs into cancer cells.
Biochem Biophys Res Commun 2006 Dec;350(4):854-9. Epub 2006 okt 2