Optogenetic dissection of how oncogenic condensates reshape signaling response and modulate drug tolerance

Drug resistance is a main challenge in cancer therapy, including for cancers driven by oncogenic fusion proteins. EML4-ALK is an oncogenic fusion of a receptor tyrosine kinase (RTK) and a tubulin binding protein, and drives approximately 5% of lung cancers. Cytosolic condensates of EML4-ALK act as signaling hubs that activate oncogenic Ras/ERK signaling in cancer cells. However, it is unclear whether oncogenic condensates can modulate cell signaling and drug response. Here, we apply optogenetic profiling to precisely activate specific nodes of the MAPK signaling cascade. We found that EML4-ALK condensates suppressed cell responsiveness to RTK activation, and conversely, ALK inhibition resensitized cells to external RTK stimulation. We found that desensitization occured because condensates sequester signaling adaptor proteins that are required to transduce active RTK signals. Release of the adaptor proteins upon treatment with ALK inhibitors (ALKi) increased cell responsiveness to environmental mitogenic cues. Importantly, we observed rapid reactivation of Erk signaling after ALK inhibition that resulted from release of RTK ligands by apoptotic cancer cells, and this reactivation counteracted cell killing. Novel combinations of ALKi with inhibitors of paracrine signaling reduced signal reactivation and decreased drug tolerance. Our study uncovers how oncogenic condensates alter signal responses in cancer cells and offers a new approach for combined treatment to EML4-ALK positive tumors.