NTSR1 and cancer: We demonstrated its applicability in detecting higher red‐NTR levels in cancer cell lines compared to normal cell lines, observing increased and variable red‐NTR levels in normal cells under hypoxic conditions versus normoxic conditions, observing elevated red‐NTR levels in tumor xenograft mouse tissues compared to other organ tissues, and identifying downregulated red‐NTR levels in cells undergoing premature senescence for the first time.