To directly determine whether hypoxia‐induced CAIX total expression levels positively correlated with any upregulated NTR activity when under mild but relevant physiological hypoxic conditions (pO2 = 2.0%), we applied our hypoxia‐sensitive smart probe to the GBM39 cell line for conducting fluorescence microscopy studies due to such GBM cell line having demonstrated relatively the highest hypoxia‐induced upregulated CAIX total expression level of all evaluated GBM cell lines. This evidence concerns the gene CA9 and glioblastoma.