ROS1 and neoplasm: Given that the C-terminal kinase domain function was likely retained (antibody targeting C-terminal of ROS1) and small cell transformation results in loss of fusion or mutation in kinase domains conferring resistance to tyrosine kinase inhibitors (TKIs), our data indicate yet a functional competent ROS1 throughout tumor progression and strengthens the need to disentangle ill-defined mechanisms of truncated ROS1 isoforms during tumor transformation39.