Reduced promoter methylation and increased expression of CSPG4 negatively influences survival of HNSCC patients

Abstract

Proteoglycans are often overexpressed in tumors and can be found on several normal and neoplastic stem cells. In this study, we analyzed in-depth the role of CSPG4 in head and neck squamous cell carcinomas (HNSCC). Analysis of CSPG4 in a homogeneous study sample of HPV-negative stage IVa HNSCCs revealed overexpression of protein and mRNA levels in a subgroup of HNSCC tumors and a significant association of high CSPG4 protein levels with poor survival. This could be validated in three publicly available microarray datasets. As a potential cause for upregulated CSPG4 expression, we identified DNA hypomethylation in a CpG-island of the promoter region. Accordingly, we found an inverse correlation of methylation and patient outcome. Finally, CSPG4 re-expression was achieved by demethylating treatment of highly methylated HNSCC cell lines establishing a direct link between methylation and CSPG4 expression. In conclusion, we identified CSPG4 as a novel biomarker in HNSCC on several biological levels and established a causative link between DNA methylation and CSPG4 protein and mRNA expression.Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer and is characterized by pathological, phenotypical and biological heterogeneity. Despite the progress in surgical and radiation techniques, the 5-year survival rate is still below 50%. 1 There is increasing evidence that epigenetic changes like DNA methylation contribute significantly to malignant transformation. Down-regulation or gene silencing caused by promoter methylation has been shown to influence tumor progression in HNSCC. 2 Chondroitin sulfate proteoglycan 4 (CSPG4, also known as NG2/ MCSP/ HW-MAA) is a highly glycosylated integral membrane protein, composed of an N-linked glycoproteinand a chondroitin sulfate proteoglycan-component. 3 Although the exact function of CSPG4 is yet unknown, it seems to be implicated in angiogenesis, tissue invasion and cell spreading. 4,5 The expression level of markers of undifferentiated cells can be accurate prognostic indicators in cancer. 6 Interestingly, there are hints that CSPG4 is expressed on normal neural stem cells and cancer stem cells of gliomas and its expression is associated with a poor prognosis and resistance to treatment. 7-11 Moreover, CSPG4 is over-expressed in epithelial tumors such as breast cancer, while in melanoma and in malignant mesothelioma it is already used for antibodybased targeted therapy. 4,12,13 As a systematic analysis of the role of CSPG4 in HNSCC is still missing, we performed an in-depth analysis of CSPG4 expression in these tumors. To prevent a potential bias in our survival analyses caused by distinct life expectations of the different TNM stages, we restricted our analyses to a more homogenous study sample consisting of HPV-negative stage IVa tumors as evidenced by p16 staining. 14, 15 We found an increased CSPG4 expression in a subgroup of HNSCCs and identified promoter methylation as regulator of CSPG4 mRNA and protein expression. Moreover, high CSPG4 expression and l...

Furanodienone overcomes temozolomide resistance in glioblastoma through the downregulation of CSPG4‐Akt‐ERK signalling by inhibiting EGR1‐dependent transcription

“…CSPG4 is an established marker for GBM, and previous studies have demonstrated that increased expression of CSPG4 in tumour cells and biopsies was associated with reduced patient survival, increased pathological severity, and MDR but was not associated with age or hypermethylation of the MGMT promoter (Stegmuller, Schneider, Hellwig, Garwood, & Trotter, ; Warta et al, ). These data indicated that activated CSPG4 signalling promoted the aggressive disease course and multidrug chemoresistance (Price et al, ; Yang et al, ).…”

Characterization of gene methylation in human papillomavirus associated-head and neck squamous cell carcinoma

“…Other risk factors for HNSCC include epigenetic regulation of gene expression, which may lead to the induction and progression of HNSCC (Bragado et al, 2012;Hakami et al, 2014). Increasing evidence suggests that promoter methylation of tumor-related genes can aggravate the disease in HNSCC (Laytragoon-Lewin et al, 2013;Rettori et al, 2013;Warta et al, 2014;Shi et al, 2015). However, few studies have reported on the prognostic value of promoter methylation in HPV-induced HNSCC.…”

Identification of two glioblastoma-associated stromal cell subtypes with different carcinogenic properties in histologically normal surgical margins

“…These molecules have been shown to be attractive potential biomarkers of cancer prognosis. For example, CSPG4/NG2 has been proposed as a prognostic marker for breast cancers [13], head and neck squamous cell carcinomas (HNSCC) [14] and gliomas [15,16]. The expression of nestin has been described in tumor and peritumor areas of GB, independently of the presence of neoplastic cells [17,18].…”