RHCG Suppresses Tumorigenicity and Metastasis in Esophageal Squamous Cell Carcinoma via Inhibiting NF-κB Signaling and MMP1 Expression

Abstract

Background and Aims: Esophageal squamous cell carcinoma (ESCC), a major histologic subtype of esophageal cancer, is increasing in incidence, but the genetic underpinnings of this disease remain unexplored. The aim of this study is to identify the recurrent genetic changes, elucidate their roles and discover new biomarkers for improving clinical management of ESCC.Methods: Western blotting and immunohistochemistry were performed to detect the expression level of RHCG. Bisulfite genomic sequencing (BGS) and methylation-specific PCR (MSP) were used to study the methylation status in the promoter region of RHCG. The tumor-suppressive effect of RHCG was determined by both in-vitro and in-vivo assays. Affymetrix cDNA microarray was used to identify the underlying molecular mechanism.Results: RHCG was frequently downregulated in ESCCs, which was significantly correlated with poor differentiation (P = 0.001), invasion (P = 0.003), lymph node metastasis (P = 0.038) and poorer prognosis (P < 0.001). Demethylation treatment and bisulfite genomic sequencing analyses revealed that the downregulation of RHCG in both ESCC cell lines and clinical samples was associated with its promoter hypermethylation. Functional assays demonstrated that RHCG could inhibit clonogenicity, cell motility, tumor formation and metastasis in mice. Further study revealed that RHCG could stabilize IκB by decreasing its phosphorylation, and subsequently inhibit NF-κB/p65 activation by blocking the nuclear translocation of p65, where it acted as a transcription regulator for the upregulation of MMP1 expression.Conclusions: Our results support the notion that RHCG is a novel tumor suppressor gene that plays an important role in the development and progression of ESCC.

Aberrant DNA Methylation in Esophageal Squamous Cell Carcinoma: Biological and Clinical Implications

“…The aberrant methylation pattern has also been identified as a prognostic indicator for ESCC patients. Recently, promoter hypermethylation of CHL1 and RHCG, two novel tumor suppressor candidates, has been reported to be associated with poor differentiation and increased invasion of ESCC, as well as advanced tumor stage and decreased overall survival (48,49). Using DNA from the plasma of ESCC patients, Liu et al analyzed the methylation status of Wnt antagonists SFRP1, DKK3, and RUNX3 and showed that patients carrying two or three of these hypermethylated genes had a significantly elevated risk of cancer recurrence, compared with those without methylated genes (46).…”

Multifaceted ammonia transporters

“…Using the example of squamous cell carcinoma cells (ESCC), normal and elevated RhCG levels were found associated with a low risk of metastasis, presumably due to inhibition of the NF-kB signaling pathway. By contrast, reduced expression of RhCG leads to the opposite effect, in particular due to hypermethylation of the rhcg promoter region (Ming et al 2018). At present, the mechanisms driving the oncosuppressive activity of proteins of this class remain unclear and require further in-depth study.…”

Multiomic Analysis of Methylation and Transcriptome Reveals a Novel Signature in Esophageal Cancer

“…Accumulating evidence suggests that DNA methylation is involved in the initiation and progression of EC and is associated with clinical outcomes. Promoter hypermethylation silences tumor suppressor genes, including coding genes (PTPN6, 18 RHCG, 19 and ZNF471 20 ) and noncoding genes (lncRNA ZNF667-AS1 and ZNF667, 21 microRNA-128, 22 and microRNA-10b-3p 23 ). Liu et al 18 indicated that PTPN6 expression was significantly downregulated in EC cell lines and tissues.…”