The Co-expression of HER Family Members and CD109 is common in Pancreatic Cancer.

In the absence of biomarkers for the early detection of pancreatic cancer and the development of more effective therapeutic interventions, pancreatic cancer is projected to become the second leading cause of death from cancer in the Western world. In the past four decades, aberrant expression and activation of human epidermal growth factor receptor (EGFR, also called HER) family members have been reported in a wide range of human cancers. Currently, of the various types of drugs targeting one or more members of the HER family, only the EGFR-specific tyrosine kinase inhibitor erlotinib and more recently Zenocutuzumab, a HER-2/HER3 bispecific antibody, were granted breakthrough therapy designation by the FDA for the treatment of patients with pancreatic cancer. However, the therapeutic benefit may be modest in some patients. Hence there is an urgent need for the identification of biomarkers as prognostic indicators, therapeutic targets, and for the response to therapy and the development of more effective therapeutic agents for this highly heterogeneous cancer. In this study, for the first time, we investigated the relative expression and prognostic significance of all members of the HER family, the type-III EGFR mutant (EGFRvIII), and CD109 in tissue microarrays (TMAs) and whole tumour specimens (WTS) from pancreatic cancer patients by immunohistochemistry. We found the positive expression of wild-type EGFR (wt-EGFR) (63%, 4.7%), HER2 (75%, 14%), HER3 (none, 14%), HER4 (45%, 21%), EGFRvIII (5%, 3%), and CD109 (67%, 55%) in TMAs (USA) and WTS (UK) from pancreatic cancer patients respectively. Our results also show that the co-expression of HER family members with CD109 occurs frequently in patients with pancreatic cancer. In addition, the co-expression of HER4/CD109 may also be associated with poorer overall survival in such patients. In this article, we shall discuss these findings and their implications and future opportunities for more effective targeting of HER positive pancreatic cancer using the HER inhibitors in combination with other drugs and therapeutic interventions.