Immunotherapy blocking programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) pathway has achieved great therapeutic effect in the clinic, but the overall response rate is not satisfactory. Early studies showed that response to treatment and overall survival could be positively related to PD-L1 expression in tumors. Therefore, accurate measurement of PD-L1 expression will help to screen cancer patients and improve the overall response rate. A small molecular positron emission tomography (PET) probe [¹⁸F]LP-F containing a biphenyl moiety was designed and synthesized for measurement of PD-L1 expression in tumors. The PET probe [¹⁸F]LP-F was obtained with a radiochemical yield of 12.72 ± 1.98%, a radiochemical purity of above 98% and molar activity of 18.8 GBq/μmol. [¹⁸F]LP-F had good stability in phosphate buffer saline (PBS) and mouse serum. In vitro assay indicated that [¹⁸F]LP-F showed moderate affinity to PD-L1. Micro-PET results showed that the tumor accumulation of [¹⁸F]LP-F in A375 tumor was inferior to that in A375-hPD-L1 tumor. All the results demonstrated that [¹⁸F]LP-F could specifically bind to PD-L1 and had a potential application in non-invasive evaluation of PD-L1 expression in tumors.

Two new platinum(II)-based complexes bearing a bone-targeting group were synthesized and characterized. They both have excellent affinity for hydroxyapatite (HA), which is abundant in human bone tissues. Their antitumor activities against five human cancer cell lines (U2OS, A549, HCT116, MDA-MB-231 and HepG2) were evaluated and compared with cisplatin (CDDP). Though the antitumor efficacies of new complexes are lower than that of CDDP, they show higher selectivity against the HepG2 hepatoma cell line than the L02 normal liver cell line. Morphology studies exhibited typical characteristics of cell apoptosis and the cell cycle distribution analysis indicated that the complexes can inhibit cancer cells by inducing cell cycle arrest at the G2/M phase, a similar mechanism of action to CDDP.