Selective cyclooxygenase-2 silencing mediated by engineered E. coli and RNA interference induces anti-tumour effects in human colon cancer cells.
BACKGROUND
Cyclooxygenase-2 (COX-2) overexpression is strongly associated with colorectal tumourigenesis. It has been demonstrated that the chronic use of non-steroidal anti-inflammatory drugs (COX inhibitors) partially protects patients from colorectal cancer (CRC) development and progression but induces severe cardiovascular side effects. New strategies for selective COX-2 blockade are required.


METHODS
We developed an improved technique, based on RNA interference (RNAi), to gain a selective COX-2 silencing in CRC cells by a tumour-dependent expression of anti-COX-2 short-hairpin RNA (shCOX-2). Anti-COX-2 shRNA-expressing vectors were delivered in CRC cells (in vitro) and in colon tissues (ex vivo) using engineered Escherichia coli strains, capable of invading tumour cells (InvColi).


RESULTS
A highly tumour-dependent shCOX-2 expression and a significant COX-2 silencing were observed in CRC cells following InvColi strain infection. Cyclooxygenase-2 silencing was associated with a strong reduction in both proliferative and invasive behaviour of tumour cells. We also demonstrated a pivotal role of COX-2 overexpression for the survival of CRC cells after bacterial infection. Moreover, COX-2 silencing was achieved ex vivo by infecting colon tissue samples with InvColi strains, leading to anti-inflammatory and anti-tumour effects.


CONCLUSIONS
Our RNAi/InvColi-mediated approach offers a promising tool for a highly selective COX-2 blockade in vitro and in vivo.
Strillacci
A
A
Department of Experimental Biology, University of Bologna, via Selmi 3, Bologna 40126, Italy. antonio.strillacci@unibo.it
Griffoni
C
C
Lazzarini
G
G
Valerii
M C
MC
Di Molfetta
S
S
Rizzello
F
F
Campieri
M
M
Moyer
M P
MP
Tomasi
V
V
Spisni
E
E
D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D003110:Colonic Neoplasms / Q000201:enzymology / Q000235:genetics*; D051546:Cyclooxygenase 2 / Q000235:genetics*; D015232:Dinoprostone / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics*; D006801:Humans; D034622:RNA Interference; D014162:Transfection; D015854:Up-Regulation
D051546:Cyclooxygenase 2; D015232:Dinoprostone