TTF1 and lung cancer: For lung cancer, examples include extracellular Thyroid transcription factor‐1 (TTF1) and Transketolase‐like‐1 (TKTL1) mRNAs for diagnosing non‐small cell lung adenocarcinoma,[38] as well as extracellular programmed cell death protein‐1 (PD‐1) and Programmed death ligand‐1 (PD‐L1) mRNAs for diagnosing non‐small cell lung cancer and predicting response to PD‐1/PD‐L1 immunotherapy.[39]