Background: Despite the recent improvements in multimodal therapies for oesophageal squamous cell carcinoma (ESCC), the prognosis remains poor. The identification of suitable biomarkers for predicting the prognosis and chemo-sensitivity is required to develop targeted treatments and improve treatment results. Methods: Proteins highly expressed in ESCC cell lines compared with normal oesophageal cell lines were screened by isobaric tag for relative and absolute quantitation (iTRAQ). We identified glypican-1 (GPC1) as a novel molecule. The clinicopathological characteristics of GPC1 were evaluated by immunohistochemistry using ESCC specimens, and clinical parameters were assessed. The correlation between GPC1 expression levels and chemo-sensitivity were analysed in vitro. Results: In the immunohistochemical assessment of 175 ESCC patients, 98.8% expressed GPC1. These patients demonstrated significantly poorer prognosis compared with patients with low-GPC1 expression by survival assay (P<0.001). Higher chemoresistance was observed in the GPC1 high-expression group. GPC1 expression levels positively correlated with chemo-sensitivity against cis-Diammineplatinum (II) dichloride (CDDP), and are potentially associated with anti-apoptotic function based on alterations in the MAPK downstream signalling pathway and Bcl-2 family member proteins. Conclusions: GPC1 is an independent prognostic factor in ESCC and is a critical molecule for altering the threshold of chemoresistance to CDDP.
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