ABSTRACT
Objective@#To investigate the function and mechanism of zinc finger protein 750 (ZNF750) in esophageal squamous cell carcinoma (ESCC).@*Methods@#Xenograft in nude mice was applied to detect the tumorigenesis of ZNF750-depleted ESCC cells. Western blot was performed to observe the expression of downstream target protein of ZNF750 in ESCC cell lines and xenograft tumor tissues in which ZNF750 was knocked down. 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) assay was used to determine the proliferation of ZNF750 stably depleted cells after restoration of its target protein.@*Results@#The tumor weight of blank control, negative control and ZNF750 knockdown groups was 137±26 mg, 161±31 mg and 463±89 mg, respectively, with a statistically significant difference (P<0.01). The expressions of Kruppel-like factor 4 (KLF4) in ZNF750-depleted ESCC cells and its derived tumor tissue xenograft in nude mice were significantly down-regulated. Restoration of KLF4 in ZNF750 stably depleted cells significantly inhibited the cell proliferation (P<0.01).@*Conclusions@#ZNF750 may be a new tumor suppressor in the tumorigenesis of ESCC, and the inhibition of cell proliferation induced by ZNF750 may be partially through the regulation of KLF4 expression.
ABSTRACT
<p><b>OBJECTIVE</b>To study the effect of Mps1 on BRAFWT/MEK/ERK pathway in the presence of wild type BRAF or BRAFV600E in melanoma.</p><p><b>METHODS</b>Melanoma cells harboring BRAFWT genotype were transfected either with pBabe-puro-GST-BRAF-WT and/or pBabe-puro-GFP-Mps1-WT or pBabe-puro-GST-BRAFV600E and/or pBabe-puro-GFP-Mps1-WT, followed by Western blot to detect Mps1 and p-ERK expression. The melanoma cells harboring BRAFWT and BRAFV600E genotype were infected with pSUPER-Mps1 retrovirus to knockdown the endogenous Mps1 protein, followed by Western blot to detect Mps1 and p-ERK expression. Meanwhile, melanoma cells harboring BRAFV600E genotype were infected with pBabe-puro-GFP-Mps1 and Western blot was performed to detect Mps1 and p-ERK expression.</p><p><b>RESULTS</b>In melanoma cells harboring BRAFWT genotype and transfected with pBabe-puro-GST-BRAF-WT and pBabe-puro-GFP-Mps1-WT, phospho-ERK levels were notably reduced as compared to either negative control or empty vector. However, cells transfected with pBabe-puro-GST-BRAFV600E and pBabe-puro-GFP-Mps1-WT, phospho-ERK levels did not change significantly compared with either negative control or empty vector. Knockout of Mps1 in BRAF wild-type cell lines led to an increased ERK activity. However, there was no significant change of ERK activity in BRAFV600E cell lines in the absence of Mps1. The expression of p-ERK in BRAFV600E mutant cell lines infected with pBabe-puro-GFP-Mps1-WT did not show any significant difference from either negative control or empty vector.</p><p><b>CONCLUSIONS</b>Based on these findings, it suggests that there exists an auto-regulatory negative feedback loop between the Mps1 kinase and BRAFWT/ERK signaling. Oncogenic BRAFV600E abrogates the regulatory negative feedback loop of Mps1 on the MAPK pathway.</p>