Down-regulation of NF kappa B activation is an effective therapeutic modality in acquired platinum-resistant bladder cancer.
BACKGROUND
No previous study has addressed the efficacy of NF-κB blockade when bladder tumors develop acquired resistance toward CDDP-treatments. We investigated the changes in NF-κB activation and therapeutic impact of NF-κB blockade by the novel NF-κB inhibitor dehydroxymethyl derivative of epoxyquinomicin (DHMEQ) in CDDP-resistant bladder cancer cells.


METHODS
Two human invasive bladder cancer cell lines, T24 and T24PR, were used. The T24PR cell line was newly established as an acquired platinum-resistant subline by culturing in CDDP-containing medium for 6 months. Expression of intranuclear p65 protein in the fractionated two cell lines was determined by Western blotting analysis. DNA-binding activity of NF-κB was detected by electrophoretic mobility shift assay. The cytotoxic effects and induction of apoptosis were analyzed in vivo and in vitro.


RESULTS
Intranuclear expression and DNA-binding activity of p65 were strongly enhanced in T24PR cells compared with those of T24 cells, and both were significantly suppressed by DHMEQ. Lowered cell viability and strong induction of apoptosis were observed by treatment with DHMEQ alone in these chemo-resistant cells compared with parent cells. As T24PR cells did not show dramatic cross-resistance to paclitaxel in the in vitro study, we next examined whether the combination of DHMEQ with paclitaxel could enhance the therapeutic effect of the paclitaxel treatment in T24PR tumors. Using mouse xenograft models, the mean volume of tumors treated with the combination of DHMEQ (2 mg/kg) and paclitaxel (10 mg/kg) was significantly smaller than those treated with paclitaxel alone (p < 0.05), and the reduction of tumor volume in mice treated with DHMEQ in combination with paclitaxel and paclitaxel alone as compared to vehicle control was 66.9% and 17.0%, respectively.


CONCLUSIONS
There was a distinct change in the activation level of NF-κB between T24 and T24PR cells, suggesting strong nuclear localization of NF-κB could be a promising target after developing acquired platinum-resistance in bladder cancer.
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. yujiroitouro@gmail.com.
Yujiro
Y
Ito
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. eiji-k@kb3.so-net.ne.jp.
Eiji
E
Kikuchi
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. urotanaka@gmail.com.
Nobuyuki
N
Tanaka
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. takemduro@gmail.com.
Takeo
T
Kosaka
Department of Applied Biological Science, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi, Tokyo, 183-8538, Japan. eriboeribo@hotmail.com.
Eriko
E
Suzuki
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. mizunor@z7.keio.jp.
Ryuichi
R
Mizuno
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. t-shinoj@cd5.so-net.ne.jp.
Toshiaki
T
Shinojima
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. akiram@a8.keio.jp.
Akira
A
Miyajima
Department of Molecular Target Medicine Screening, Aichi Medical University, 1-1 Yazakokarimata, Nagakute, Aichi, 480-1195, Japan. umezawa@aichi-med-u.ac.jp.
Kazuo
K
Umezawa
Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. moto-oya@z3.keio.jp.
Mototsugu
M
Oya
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000096:biosynthesis* / Q000235:genetics; D017239:Paclitaxel / Q000008:administration & dosage; D010984:Platinum / Q000008:administration & dosage; D015398:Signal Transduction / Q000187:drug effects; D051996:Transcription Factor RelA / Q000096:biosynthesis* / Q000235:genetics; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D023041:Xenograft Model Antitumor Assays
D016328:NF-kappa B; C498144:Rela protein, mouse; D051996:Transcription Factor RelA; D010984:Platinum; D017239:Paclitaxel