ROS-1 re-arrangements and c-MET amplifications in adenocarcinoma lung: A tertiary care center study from North India

Background: C-ros oncogene 1, receptor tyrosine kinase (ROS 1) proto-oncogene 1, receptor tyrosine kinase (ROS-1) fusions are potent oncogenic drivers and these re-arrangements promote signal transduction programs leading to uninhibited cell survival and proliferation identified in 1–2% of cases of nonsmall-cell lung cancer. Mesenchymal epithelial transition factor (MET) receptor tyrosine kinase and its ligand are predominantly involved in epithelial mesenchymal transition and tissue regeneration. The MET amplification and overexpression is oncogenic in 3–7% cases. The objectives of this study were to identify the frequency of ROS-1 and c-MET protein expression in adenocarcinoma lung and to correlate it with the clinicopathological parameters and to analyze the histomorphology of cases that harbor the characteristic mutations (c-MET and ROS-1). Materials and Methods: Study group comprised a prospective cases series of 90 cases of adenocarcinoma lung. ROS-1 protein expression was determined by immunohistochemistry using the D4D6 rabbit monoclonal antibody (Cell Signaling, Danvers, MA) and c-MET protein expressed was analyzed using the SP-44 clone (Ventana Medical Systems). Results: c-MET protein expression was identified in 33.33% cases (n = 30/90) with statistically significant thyroid transcription factor-1 (TTF-1) positivity. ROS-1 protein expression was detected in 3.33% cases (n-3/90), in biopsies from the respiratory tree with TTF-1 expression. Conclusion: This is the first study from the Indian subcontinent to identify the frequency of ROS-1 re-arrangements and MET amplification in the Indian population. The availability of targeted therapy that has a significant impact on survival makes it essential to detect these less frequent mutations.