shRNA plasmid - which company is good? (Oct/07/2009 )

Hello everyone,
I am trying to stablily knockdown a gene in our cancer cell line. I found that Santa cruz is sellling all kinds of shRNA plasmids and lentiviral particles, so do some other companys. Has anyone used their similar products and could you give me some suggestion which company is more reliable?
Thanks
Dan

If you're interested in using lentiviral vectors to deliver shRNA and generate stable lines, depending on your experimental design you have the following options:

Invitrogen: BLOCK-iT system
System Biosciences: pSIH1-H1 vectors
Biosettia: pLV-RNAi vectors
Open Biosystem: pTRIPZ system
Addgene: pLKO.1 and pLL3.7
Dharmacon: SMARTvector
and many others..............

My experience is: Invitrogen's shRNA designer seems the best and Biosettia's lentiviral shRNA vector only needs one shRNA oligo (single oligonucleotide RNAi technology) for each shRNA clone you make (save you 15 dollars per oligo sysnthesis).

Origene has shRNA vectors that can be used for plasmid based or retroviral stable cell generation. They sell you a kit of 4 different shRNA constructs, the base vector and a negative control shRNA vector. They also have a guarantee that if none of the 4 constructs provide at least 70% knockdown (assuming good transfection efficiency), they will then make 4 new constructs.