Flotillin-1 promotes tumor necrosis factor-Œ± receptor signaling and activation of NF-Œ∫B in esophageal squamous cell carcinoma cells
Authors: Jueheng Wu
Hui Gong
Mengfeng Li
Chanjuan Wang
Jun Li
Chuyong Lin
Liping Liu
Libing Song
Journal: Gastroenterology (2012)
Discipline: CLINICAL MEDICINE
Keywords: Flotillin-1; NF-Œ∫B; Esophageal squamous cell carcinoma; Lipid raft protein; Tumor growth
Affiliations: State Key Laboratory of Oncology in Southern China, Department of Experimental Research, Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, China.

Abstract:  Background &amp; aims: The flotillin family of proteins, including flotillin-1 (FLOT1 or Reggie-2), are lipid raft proteins that initiate receptor kinase signaling and are up-regulated in several tumor types. We investigated the role of FLOT1 signaling and activation of the transcription factor nuclear factor (NF)-Œ∫B in esophageal squamous cell carcinoma (ESCC) cells. Methods: We used immunoblot and immunochemical analyses to determine levels of the lipid raft-associated protein FLOT1 in ESCC cell lines and 432 ESSC samples from patients; primary normal esophageal epithelial cells and matched adjacent nontumor tissues were used as controls. We determined the ability of FLOT1 to activate NF-Œ∫B using kinase, electrophoretic mobility shift, and luciferase reporter assays. We measured the effects of FLOT1 overexpression and knockdown with short hairpin RNAs in ESCC cell lines using colony formation, anchorage-independent growth, chicken chorioallantoic membrane, transwell matrix penetration, and Annexin V-binding assays. We analyzed growth of ESCC xenograft tumors in nude mice. Results: Levels of FLOT1 were increased in ESCC cell lines and samples from patients, compared with controls; protein levels correlated with disease stage and survival time. Overexpression of FLOT1 in Kyse30 and Kyse510 ESCC cell lines increased proliferation, anchorage-independent growth, and invasive activity and protected them from apoptosis. FLOT1-transduced ESCC cells formed larger tumors in nude mice than control cells (transduced with only the vector). FLOT1 facilitated recruitment of the tumor necrosis factor-Œ± receptor to lipid rafts; promoted K63-linked polyubiquitination of the signaling intermediaries tumor necrosis factor receptor associated factor 2, receptor interacting protein, and NEMO; and sustained the activation of NF-Œ∫B. Levels of FLOT1 correlated with activation of NF-Œ∫B in ESCC samples from patients. Conclusions: The lipid raft protein FLOT1 is up-regulated in ESCC cell lines and samples from patients and promotes ESCC cell proliferation and tumor growth in mice. FLOT1 activates tumor necrosis factor-Œ± receptor signaling and sustains activation of NF-Œ∫B in ESCC cells. 

Retracted: No

PubPeer comments:
 The solutions reported in the work shall be correct. But, the graphical demonstrations are misleading. To be precise, the contour plots shown in Figs. 2-7 are incorrect and they are not corresponding to the given 3D plots. The nature profiles is completely different in 3D and contour plots. See the attached figures for an easy reference. Fig 2:  Fig 3:  Fig 4:  Fig 5:  Fig 6:  Fig 7:  ,