Recent applications of RNA interference (RNAi) in mammalian systems

Specific knockdown of PPARδ gene in colon cancer cells by lentivirus-mediated RNA interfering

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors. Of this family, PPARδ has been implicated in the pathogenesis of colorectal cancer, whereas its exact role is highly controversial as available studies yield conflicting results. Therefore, further studies using powerful and duplicable methods are needed to clarify the functions of PPARδ in colorectal cancer. RNA interference (RNAi) is such a powerful tool for specific suppression of gene expression at the posttranscriptional level. Of available RNAi methods, lentivirus has been shown to mediate RNAi most efficiently and stably based on its remarkable advantages, such as powerful transduction efficiency and a wider range of target cells, integration of expression cassette into host genomics, low immunogenicity and self-inactivated and replication-incompetent after integrating into host genomics. In this chapter, we will introduce the details of using lentivirus-mediated RNAi to specifically knockdown the expression of PPARδ in colon cancer cell lines. This method includes: designing and cloning short-hairpin RNA cassette into lentivector, constructing and titrating lentiviral particles, infecting target cells with lentivirus and assaying the knockdown efficiency.

RNA interference against peroxisome proliferator-activated receptor delta gene promotes proliferation of human colorectal cancer cells

PURPOSE

This study was designed to investigate the effects of peroxisome proliferator-activated receptor delta (PPAR delta) on the proliferation and apoptosis of human colorectal cancer cells.

METHODS

For RNA interfering (RNAi), HCT-116 cells were transfected with short hairpin RNA (shRNA)-expressing plasmids against PPAR delta or negative control vectors, and the stably transfected cells were selected with G418. The efficacy of RNAi was assessed by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting analysis. The proliferation, cell cycle, and apoptosis of HCT-116 cells treated by RNAi, compared with those containing control vectors or untreated, were analyzed respectively by using MTT (methyl thiazolyl tetrazolium), flow cytometry, and TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick end-labeling (TUNEL) assay.

RESULTS

RNAi targeting PPAR delta resulted in substantial suppression of PPAR delta expression and significantly promoted the proliferation of HCT-116 cells relative to those with control vectors or untreated, obviously decreasing the frequency of G1-phase cells but had no effect on cell apoptosis.

CONCLUSIONS

PPAR delta may inhibit the proliferation of CRC cells and increase the number of cells in G1 phase, without any function in cell apoptosis.