Fig. 4

Effect of maintenance treatment with different kinase inhibitors alone or in combination with trastuzumab, after induction therapy with oxaliplatin plus trastuzumab in HER2-amplified colon cancer xenograft models. HER2-amplified colon cancer cells (SW48-HER2 and LIM1215-HER2) were injected into the right flank of nude mice. After 2 weeks of subcutaneous injection, mice were treated with oxaliplatin (10 mg/kg once every 2 weeks, i.p.) in combination with trastuzumab (10 mg/kg twice a week, i.p.) for 4 weeks (induction treatment). Afterward, mice were randomized into nine groups and treated for 8 weeks (maintenance treatment). Ctrl: control; pictilisib (75 mg/Kg) and refametinib (25 mg/kg) were administrated every day for 5 days by o.g, as single agents and in different combinations; trastuzumab (10 mg/kg twice a week, by i.p.) and lapatinib (30 mg/kg every day, by o.g.) as single agents and in different combinations. a Treatment scheme. Red boxes: pictilisib treatment days; green boxes: refametinib treatment days; violet boxes: trastuzumab treatment days; light blue boxes: lapatinib treatment days. b–c Antitumor activity of maintenance treatment in SW48-HER2 and LIM1215-HER2 tumor-bearing mice. The indicated cancer cell lines were grown as subcutaneous tumor xenografts in nude mice and treated with different drugs as indicated above. The mean data are present. Tumor growth curves were calculated on the basis of three times a week tumor measurements during the treatment period and after 16 weeks of observation after termination of therapy. d Analysis of EGFR-dependent intracellular signaling by western blotting in LIM1215-HER2 colorectal cancer xenograft. At the end of maintenance treatment, 1 mouse per group treated with refamentinib, pictilisib or with their combination was sacrificed. Tumor samples were collected, and total cell protein extracts were subjected to immunoblotting with the indicated antibodies, as described in materials and methods. Anti-tubulin antibody was used for normalization of protein extract content