Constitutive NF-kappaB activation in colorectal carcinoma plays a key role in angiogenesis, promoting tumor growth.
OBJECTIVE
Nuclear factor kappaB (NF-kappaB) is an important transcription factor in various biological processes. Constitutive NF-kappaB activation has been noted in many tumors, including colorectal cancers. However, the precise role of this activation in colorectal cancer is unclear.


METHODS
Constitutive NF-kappaB activation was evaluated in colorectal cancer tissues and cell lines. To inhibit NF-kappaB activation, we established cancer cells with stable knockdown of IkappaB kinase gamma (NF-kappaB essential modulator), which is the regulatory subunit of the IkappaB kinase complex, by RNA interference. Cell growth and apoptosis were evaluated in wild-type cells (WT) and knocked-down cells (KD). Microarray and protein array analysis were also done. To determine involvement of angiogenesis, human umbilical vein endothelial cells were used. By s.c. transplantation of the cells into nude mice, tumor sizes, vascularity, and chemodrug sensitivity were analyzed.


RESULTS
Constitutive NF-kappaB activation was observed in 40% of colorectal cancer tissues and 67% of cell lines. Cell proliferation was not different between WT and KD in vitro, whereas apoptosis mediated by tumor necrosis factor-alpha and 5-fluorouracil were increased in KD. Several angiogenic chemokines were decreased in KD. Human umbilical vein endothelial cells incubated in WT supernatant showed more branch points than in KD, suggesting that constitutive NF-kappaB activation was involved in angiogenesis. Subcutaneous tumor expansion was suppressed to 23% in KD, and vessels were also decreased. By 5-fluoruracil treatment, tumor expansion was suppressed to a greater extent in KD (to 6%) than in WT (to 50%).


CONCLUSIONS
NF-kappaB inhibition may represent a potent treatment modality in colorectal cancer, especially in cases with constitutive NF-kappaB activation.
Sakamoto
Kei
K
Division of Gastroenterology, Institute for Adult Diseases, Asahi Life Foundation, Tokyo, Japan.
Maeda
Shin
S
Hikiba
Yohko
Y
Nakagawa
Hayato
H
Hayakawa
Yoku
Y
Shibata
Wataru
W
Yanai
Ayako
A
Ogura
Keiji
K
Omata
Masao
M
D043925:Angiogenesis Inducing Agents / Q000378:metabolism*; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D002277:Carcinoma / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D018925:Chemokines / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D005472:Fluorouracil / Q000494:pharmacology; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D016328:NF-kappa B / Q000378:metabolism*; D009389:Neovascularization, Pathologic / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D043925:Angiogenesis Inducing Agents; D000964:Antimetabolites, Antineoplastic; D018925:Chemokines; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D051550:I-kappa B Kinase; D048031:JNK Mitogen-Activated Protein Kinases; D005472:Fluorouracil