Inhibition of MDM2 Re-Sensitizes Rapamycin Resistant Renal Cancer Cells via the Activation of p53.
OBJECTIVE
Rapamycin is a potential anti-cancer agent, which modulates the activity of mTOR, a key regulator of cell growth and proliferation. However, several types of cancer cells are resistant to the anti-proliferative effects of rapamycin. In this study, we report a MDM2/p53-mediated rapamycin resistance in human renal cancer cells.


METHODS
Trypan blue exclusion tests were used to determine the cell viability. Changes in mRNA and protein expression were measured using real-time PCR and western blot, respectively. Xenograft models were established to evaluate the in vivo effects of rapamycin combined with a MDM2 inhibitor.


RESULTS
Rapamycin treatment suppresses the expression of MDM2 and exogenous overexpression of MDM2 in A498 cells contributes to rapamycin resistance. By establishing a rapamycin resistant cell line, we observed that MDM2 was significantly upregulated in rapamycin resistant cells than that in rapamycin sensitive cells. Importantly, the rapamycin resistant cells demonstrated attenuated accumulation of p53 in the nucleus in response to rapamycin treatment. Moreover, the inhibition of MDM2 by siMDM2 sensitizes A498 cells to rapamycin through the activation of p53. In both in vitro and in vivo models, the combination of rapamycin with the MDM2 inhibitor, MI-319, demonstrated a synergistic inhibitory effect on rapamycin resistant cells.


CONCLUSIONS
Our study reports a novel mechanism for rapamycin resistance in human renal cancer and provides a new perspective for the development of anti-cancer drugs.
Molecular Oncology Laboratory of Cancer Research Institute, the First Affiliated Hospital of China Medical University, Shenyang, PR China.
Xin
X
Tian
Shundong
S
Dai
Jing
J
Sun
Shenyi
S
Jiang
Chengguang
C
Sui
Fandong
F
Meng
Yan
Y
Li
Liye
L
Fu
Tao
T
Jiang
Yang
Y
Wang
Jia
J
Su
Youhong
Y
Jiang
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D004338:Drug Combinations; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D007279:Injections, Subcutaneous; D007680:Kidney Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D013141:Spiro Compounds / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D004338:Drug Combinations; D007211:Indoles; C548961:MI 319; D034741:RNA, Small Interfering; D013141:Spiro Compounds; D016159:Tumor Suppressor Protein p53; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D020123:Sirolimus