Phosphotyrosine profiling identifies ephrin receptor A2 as a potential therapeutic target in esophageal squamous‐cell carcinoma

Abstract

Esophageal squamous‐cell carcinoma (ESCC) is one of the most common malignancies in Asia. Currently, surgical resection of early‐stage tumor is the best available treatment. However, most patients present late when surgery is not an option. Data suggest that chemotherapy regimens are inadequate for clinical management of advanced cancer. Targeted therapy has emerged as one of the most promising approaches to treat several malignancies. A prerequisite for developing targeted therapy is prior knowledge of proteins and pathways that drive proliferation in malignancies. We carried out phosphotyrosine profiling across four different ESCC cell lines and compared it to non‐neoplastic Het‐1A cell line to identify activated tyrosine kinase signaling pathways in ESCC. A total of 278 unique phosphopeptides were identified across these cell lines. This included several tyrosine kinases and their substrates that were hyperphosphorylated in ESCC. Ephrin receptor A2 (EPHA2), a receptor tyrosine kinase, was hyperphosphorylated in all the ESCC cell lines used in the study. EPHA2 is reported to be oncogenic in several cancers and is also known to promote metastasis. Immunohistochemistry‐based studies have revealed EPHA2 is overexpressed in nearly 50% of ESCC. We demonstrated EPHA2 as a potential therapeutic target in ESCC by carrying out siRNA‐based knockdown studies. Knockdown of EPHA2 in ESCC cell line TE8 resulted in significant decrease in cell proliferation and invasion, suggesting it is a promising therapeutic target in ESCC that warrants further evaluation.

A dual specificity kinase, DYRK1A, as a potential therapeutic target for head and neck squamous cell carcinoma

“…We and others have demonstrated that phosphoproteomics is an effective technique to study aberrantly activated kinase signaling pathways in multiple malignancies82930. There is substantial literature indicating that protein kinases are most frequently involved in tumorigenesis31.…”

“…Peptides were lyophilized and subjected to phosphopeptide enrichment. The enrichment of tyrosine phosphorylated peptides from TMT labeled lysates was carried out using Phosphoscan Kit (P-Tyr-1000, Cell signaling technology, Danvers, MA) as described previously29.…”

Phosphotyrosine profiling of human cerebrospinal fluid

“…The CSF proteins were digested with trypsin, phosphotyrosine peptides were enriched, and LC–MS/MS analysis was conducted as described in Methods [ 25 , 30 , 31 ] (Fig. 1 ).…”

Progress in the development of protein biomarkers of oesophageal and gastric cancers

“…These early findings are intriguing but further validation is required before levels of heat shock proteins or other similar protein biomarkers can be adapted for routine use as predictive markers of chemotherapy response in oesophageal cancer. Phosphotyrosine profiling has identified ephrin receptor A2 as a potential therapeutic target in oesophageal squamous carcinoma .…”

“…These early findings are intriguing but further validation is required before levels of heat shock proteins or other similar protein biomarkers can be adapted for routine use as predictive markers of chemotherapy response in oesophageal cancer. Phosphotyrosine profiling has identified ephrin receptor A2 as a potential therapeutic target in oesophageal squamous carcinoma [24]. Proteomic analysis of serum rather than biopsy tissue samples is a technique that may identify predictive biomarkers of disease that could be used without the need for invasive procedures such as endoscopy.…”