Enhancing radiosensitization in EphB4 receptor-expressing Head and Neck Squamous Cell Carcinomas.

Shilpa Bhatia,Valery Krasnoperov,Antonio Jimeno,Ayman Oweida,Jaspreet Sharma,Xiao-Jing Wang,Kellen Hirsch,Parkash S Gill,Anastacia Griego,David Raben,Stephen Keysar,Sana D Karam,Elena B Pasquale

doi:10.1038/srep38792

Abstract

Members of the Eph family of receptor tyrosine kinases have been implicated in a wide array of human cancers. The EphB4 receptor is ubiquitously expressed in head and neck squamous cell carcinoma (HNSCC) and has been shown to impart tumorigenic and invasive characteristics to these cancers. In this study, we investigated whether EphB4 receptor targeting can enhance the radiosensitization of HNSCC. Our data show that EphB4 is expressed at high to moderate levels in HNSCC cell lines and patient-derived xenograft (PDX) tumors. We observed decreased survival fractions in HNSCC cells following EphB4 knockdown in clonogenic assays. An enhanced G2 cell cycle arrest with activation of DNA damage response pathway and increased apoptosis was evident in HNSCC cells following combined EphB4 downregulation and radiation compared to EphB4 knockdown and radiation alone. Data using HNSCC PDX models showed significant reduction in tumor volume and enhanced delay in tumor regrowth following sEphB4-HSA administration with radiation compared to single agent treatment. sEphB4-HSA is a protein known to block the interaction between the EphB4 receptor and its ephrin-B2 ligand. Overall, our findings emphasize the therapeutic relevance of EphB4 targeting as a radiosensitizer that can be exploited for the treatment of human head and neck carcinomas.

Highlights

The management of locally advanced head and neck squamous cell carcinoma (HNSCC) patients presents a formidable challenge
We observed that EphB4 protein is expressed at high to moderate levels in HNSCC cells compared to normal oral keratinocyte (NOK) cells (Fig. 1A)
In caspase-3/7 assay, we observed a significant increase in apoptosis (~28%) in Fadu cells transfected with EphB4-Short interfering RNAs (siRNA) and 4 Gy dose of radiation compared to radiation alone at 96 h (Fig. 3A, p < 0.05)

Summary

Introduction

The management of locally advanced head and neck squamous cell carcinoma (HNSCC) patients presents a formidable challenge. There has been limited improvement in survival rates for these patients[1,2] This can be attributed to activation of some of the tyrosine kinase receptor pathways that promote tumor cell proliferation and survival[3]. The EphB4 receptor belongs to the Eph family of receptor protein tyrosine kinases[5] and has been shown to play a pro-tumorigenic role in carcinomas of head and neck, lung, prostate, breast, mesothelium, and esophagus[3,6,7,8,9,10,11]. The characterization, binding specificity, and pharmacokinetics of sEphB4-HSA has already been established in previous studies[18] To our knowledge, this is the first study to elucidate the functional role of EphB4 targeting in radiosensitization of HNSCCs

Methods

Results

Conclusion