S1PR1 and neoplasm: At 24 h, the tumor uptake value of the SK-HEP-1 group was 5.53 ± 0.32% ID/g, which was higher than both blocking group (3.64 ± 0.39% ID/g, P = 0.003) and MCF-7 group (2.81 ± 0.21% ID/g, P = 0.000), and indicated that the molecular probe had targeting potential and specificity for tumors with high S1PR1 expression.