ANXA5 and colon adenocarcinoma: To analyze in detail the consequences of AHA labeling, we cultured the mouse colon adenocarcinoma cell line MC38 up to 24 h under standard labeling conditions as described in “Methods.” We observed that the replacement of Met by AHA in the culture medium affected cell viability and proliferation (Fig. 1a, b) and induced a shift of the entire cell population into a pre-apoptotic state as indicated by the staining with TO-PRO-3 and Annexin V (Fig. 1c).