Picropodophyllin (Picropodophyllin (PPP)) (PPP) is a specific IGF-1R inhibitor (IC50: 1 nM). Picropodophyllin specifically inhibits the activity and downregulates the cellular expression of IGF1R without interfering with activities of other growth factor receptors, such as receptors for insulin, epidermal growth factor, platelet-derived growth factor, fibroblast growth factor and mast/stem cell growth factor (KIT).

IGF-1R:1 nM

在完整细胞中，PPP有效抑制IGF-1激活的IGF-1R、Akt (Ser 473)和Erk1/2的磷酸化。Picropodophyllin特异性抑制细胞生长，并在培养的IGF-1R阳性肿瘤细胞中诱导凋亡。[1] Picropodophyllin与ABT-737和ABT-199协同作用，通过进一步降低细胞活性和增强凋亡，从而增强对HMCL、原发性人MM细胞和小鼠5T33 mM细胞的敏感性。[3] Picropodophyllin和索拉非尼协同抑制肝细胞癌细胞的增殖和移动性。[4]

在SCID小鼠中，通过人类ES-1、BE和PC3细胞外植后，Picropodophyllin（20 mg/kg/12 h，i.p.）能引起肿瘤完全消退。[1] 在5T33 mM小鼠模型中，Picropodophyllin同样展现出显著的抗肿瘤活性，并显著延长生存期。[2]

In vitro tyrosine kinase assays.: Assay of IGF-1R-catalyzed substrate phosphorylation of pTG, using a 96-well plate tyrosine kinase assay kit, is performed. We use recombinant epidermal growth factor receptor, immunoprecipitated IR from HEPG2, immunoprecipitated IGF-1R from P6 cells, and IGF-1R immunodepleted supernatant from P6 (representing "non-IGF-1R tyrosine kinases"). After 30-min treatment of the receptors with the desired compounds in the kinase buffer [50 mM HEPES buffer (pH 7.4), 20 mM MgCl2, 0.1 MnCl2, and 0.2 Na3VO4], the kinase reaction is activated by addition of ATP. The phosphorylated polymer substrate is probed with a phosphotyrosine-specific monoclonal antibody conjugated to horseradish peroxidase, clone PT-66. Color is developed with horseradish peroxidase chromogenic substrate O-phenylenediamine dihydrochloride and quantitated by spectrophotometry (ELISA reader). IGF-1R tyrosine autophosphorylation is analyzed by a sandwich ELISA assay. Briefly, 96-well plates are coated overnight at 4°C with 1 μg/well of an antibody to IGF-1R β-subunit. The plates are blocked with 1% BSA in PBS Tween for 1 h, and then 80 μg/well of total protein lysate from the P6 cell line is added. As a negative control we use total protein lysate from the R- cell line. The investigated compounds are added in tyrosine kinase buffer without ATP at room temperature for 30 min before kinase activation with ATP. Kinase assay is performed using the Sigma kit (see above). After spectrophotometry the IC50 values of inhibitors are determined using the REGRESSION function of Statistica program.

The determinations are performed using the Cell proliferation kit II, which is based on colorimetric change of the yellow tetrazolium salt 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt in orange formazan dye by the respiratory chain of viable cell. All of the standards and experiments are performed in triplicates. (Only for Reference)