Oncoproteomic analysis reveals co-upregulation of RELA and STAT5 in carboplatin resistant ovarian carcinoma.
BACKGROUND
Ovarian cancer is one of the most lethal types of female malignancy. Although most patients are initially responsive to platinum-based chemotherapy, almost all develop recurrent chemoresistant tumors and succumb to their diseases. Elucidating the pathogenesis underlying drug resistance is fundamental to the development of new therapeutics, leading to improved clinical outcomes in these patients.


RESULTS
We compared the proteomes of paired primary and recurrent post-chemotherapy ovarian high-grade serous carcinomas from nine ovarian cancer patients using CIEF/Nano-RPLC coupled with ESI-Tandem MS. As compared to their primary tumors, more than half of the recurrent tumors expressed higher levels of several proteins including CP, FN1, SYK, CD97, AIF1, WNK1, SERPINA3, APOD, URP2, STAT5B and RELA (NF-kappaB p65), which were also validated by quantitative RT-PCR. Based on shRNA screening for the upregulated genes in in vitro carboplatin-resistant cells, we found that simultaneous knockdown of RELA and STAT5B was most effective in sensitizing tumor cells for carboplatin treatment. Similarly, the NF-kappaB inhibitor, BMS-345541, and the STAT5 inhibitor, Dasatinib, significantly enhanced cell sensitivity to carboplatin. Moreover, both RELA and STAT5 are known to bind to the promoter region of Bcl-X, regulating its promoter activity. In this regard, augmented Bcl-xL expression was detected in carboplatin-resistant cells. Combined ectopic expression of RELA and STAT5B enhanced Bcl-xL promoter activity while treatment with BMS-345541 and Dasatinib decreased it. Chromatin immunoprecipitation of the Bcl-X promoter region using a STAT5 antibody showed induction of RELA and STAT5 DNA-binding segments both in naïve cells treated with a high concentration of carboplatin as well as in carboplatin-resistant cells.


CONCLUSIONS
Proteomic analysis identified RELA and STAT5 as two major proteins associated with carboplatin resistance in ovarian tumors. Our results further showed that NF-kappaB and STAT5 inhibitor could sensitize carboplatin-resistant cells and suggest that such inhibitors can be used to benefit patients with carboplatin-resistant recurrent ovarian cancer.
Jinawath
Natini
N
Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America.
Vasoontara
Chanont
C
Jinawath
Artit
A
Fang
Xueping
X
Zhao
Kejia
K
Yap
Kai-Lee
KL
Guo
Tong
T
Lee
Cheng S
CS
Wang
Weijie
W
Balgley
Brian M
BM
Davidson
Ben
B
Wang
Tian-Li
TL
Shih
Ie-Ming
IeM
D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D016190:Carboplatin / Q000627:therapeutic use*; D047369:Chromatin Immunoprecipitation; D019008:Drug Resistance, Neoplasm; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D009363:Neoplasm Proteins / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D040901:Proteomics; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; C498143:RELA protein, human; D050799:STAT5 Transcription Factor; D051996:Transcription Factor RelA; D016190:Carboplatin