In a narrow sense of cancer biomarker, it is limited to proteins the most used to challenge in the clinical applications, especially in the CAR-T therapy. Specifically, a cancer biomarker of the CAR-T provides the most prominent signal of cancer cells for distinguishing from normal cells and the most effective CAR T target for immune recognition and destruction. https://www.creative-biolabs.com/car-t/biomarker-identification-selection.htm