Up-regulated manganese superoxide dismutase expression increases apoptosis resistance in human esophageal squamous cell carcinomas.
BACKGROUND
Esophageal cancer is one of the most common malignancies in the world. In order to identify the proteins associated with esophageal squamous cell carcinomas (ESCC), we analyzed the protein profiles of ESCC cases with tumor and matched adjacent normal tissues.


METHODS
Two-dimensional electrophoresis (2-DE) was carried out to analyze the protein profiles. Dysregulated protein spots were identified by Matrix-Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) and verified by liquid chromatography/electrospray ionization ion trap-mass spectrometry/mass spectrometry (LC-ESI-IT MS). RT-PCR and immunohistochemistry on tissue microarray were performed to confirm the gene dysregulation in esophageal cancerous tissues. RNA interference (RNAi) was used to knock down the gene expression in ESCC cell lines. Apoptosis assay with annexin V-FITC/PI staining was conducted and cells were analyzed by flow cytometry.


RESULTS
2-DE showed that two protein spots with approximate molecular weights and different pI were elevated in 12 out of 18 ESCCs as compared to the corresponding normal tissues. Both the two spots were identified as MnSOD by MALDI-TOF and were verified by LC-ESI-IT MS. MnSOD overexpression was detected in 14 tumors out of 24 cases by RT-PCR and 52 tumors out of 116 cases by immunohistochemistry comparing to normal epithelia. siRNA-mediated silencing of MnSOD in KYSE450 and KYSE150 cell lines revealed that MnSOD protected ESCC cells from apoptosis induced by ultraviolet (UV) and doxorubicin (DOX).


CONCLUSIONS
These findings suggest that there existed two isoforms of MnSOD protein in normal and tumor esophageal tissues. MnSOD was overexpressed in ESCC and its up-regulation in esophageal cancer cells was associated with apoptosis resistance.
Hu
Hai
H
State Key Laboratory of Molecular Oncology, Cancer Institute (Hospital), Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
Luo
Man-li
ML
Du
Xiao-li
XL
Feng
Yan-bin
YB
Zhang
Yu
Y
Shen
Xiao-ming
XM
Xu
Xin
X
Cai
Yan
Y
Han
Ya-ling
YL
Wang
Ming-rong
MR
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002294:Carcinoma, Squamous Cell / Q000201:enzymology* / Q000473:pathology; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D004938:Esophageal Neoplasms / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D008969:Molecular Sequence Data; D034622:RNA Interference; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013482:Superoxide Dismutase / Q000235:genetics / Q000502:physiology*; D014466:Ultraviolet Rays; D015854:Up-Regulation
D004317:Doxorubicin; D013482:Superoxide Dismutase