STING1 and neoplasm: Upon phosphorylation, IRF3 translocates to the nucleus, where it activates the transcription of type 1 IFNs and ISGs, which is a hallmark of activation of the STING pathway.[31] Our immunohistochemical analysis of tumor tissues demonstrated elevated nuclear IRF3 expression in the C5‐PE38 treatment group (Figure 6i), indicating that the downstream of STING pathway was initiated.