Anti-tumor efficacy of theliatinib in esophageal cancer patient-derived xenografts models with epidermal growth factor receptor (EGFR) overexpression and gene amplification

Patient-derived xenograft: a developing tool for screening biomarkers and potential therapeutic targets for human esophageal cancers

Esophageal cancer (EC) represents a human malignancy, diagnosed often at the advanced stage of cancer and resulting in high morbidity and mortality. The development of precision medicine allows for the identification of more personalized therapeutic strategies to improve cancer treatment. By implanting primary cancer tissues into immunodeficient mice for expansion, patient-derived xenograft (PDX) models largely maintain similar histological and genetic representations naturally found in patients' tumor cells. PDX models of EC (EC-PDX) provide fine platforms to investigate the tumor microenvironment, tumor genomic heterogeneity, and tumor response to chemoradiotherapy, which are necessary for new drug discovery to combat EC in addition to optimization of current therapeutic strategies for EC. In this review, we summarize the methods used for establishing EC-PDX models and investigate the utilities of EC-PDX in screening predictive biomarkers and potential therapeutic targets. The challenge of this promising research tool is also discussed.

Targeted Therapies and Immunotherapies in the Treatment of Esophageal Cancers

Esophageal cancer (EC) is among the most frequent and deadly cancers around the world. While esophageal adenocarcinoma (EAC) has one of the fastest-growing incidences amongst cancers in the US, it also has one of the lowest survival rates due to the limited effective treatment options. Fortunately, in the past decade, two targeted therapies and an immunotherapy agent have been approved by the FDA for metastatic EAC and esophageal squamous cell carcinoma (ESCC), with several more currently being considered for approval. In terms of immunotherapies, in July 2019, the FDA approved the PD1 inhibitor pembrolizumab for second-line treatment of PDL1-positive, advanced or metastatic ESCC. Two years before, pembrolizumab had been approved for the third-line treatment of PDL1-positive EAC. The PD1 inhibitor nivolumab, which was found in one study to outperform chemotherapy irrespective of PDL1 status, has yet to secure FDA approval. In terms of targeted therapies, although as many as 90% of EC cases show upregulated EGFR, anti-EGFR therapy has not been shown to improve survival. Ramucirumab, an antibody targeting both VEGF and HER2/neu receptors, has been approved for the treatment of refractory EAC, while the anti-HER2 monoclonal antibody (mAb) trastuzumab has been approved as front-line treatment for HER2-positive cases which account for approximately 20% of ECs. Although these targeted therapies and immunotherapies have resulted in significant improvements in survival for specific patient populations that are positive for certain biomarkers, such as PDL1 and HER2/neu, the survival rates remain low for a large proportion of the metastatic EC patient population, necessitating the development of further targeted treatment options.