Association between gain-of-function mutations in PIK3CA and resistance to HER2-targeted agents in HER2-amplified breast cancer cell lines.

BACKGROUND: The mechanism of resistance to human epidermal growth factor receptor 2 (HER2)-targeted agents has not been fully understood. We investigated the influence of PIK3CA mutations on sensitivity to HER2-targeted agents in naturally derived breast cancer cells. MATERIALS AND METHODS: We examined the effects of Calbiochem (CL)-387,785, HER2 tyrosine kinase inhibitor, and trastuzumab on cell growth and HER2 signaling in eight breast cancer cell lines showing HER2 amplification and trastuzumab-conditioned BT474 (BT474-TR). RESULTS: Four cell lines with PIK3CA mutations (E545K and H1047R) were more resistant to trastuzumab than the remaining four without mutations (mean percentage of control with 10 microg/ml trastuzumab: 58% versus 92%; P = 0.010). While PIK3CA-mutant cells were more resistant to CL-387,785 than PIK3CA-wild-type cells (mean percentage of control with 1 microM CL-387,785: 21% versus 77%; P = 0.001), CL-387,785 retained activity against BT474-TR. Growth inhibition by trastuzumab and CL-387,785 was more closely correlated with changes in phosphorylation of S6K (correlation coefficient, 0.811) than those of HER2, Akt, or ERK1/2. Growth of most HER2-amplified cells was inhibited by LY294002, regardless of PIK3CA genotype. CONCLUSIONS: PIK3CA mutations are associated with resistance to HER2-targeted agents. PI3K inhibitors are potentially effective in overcoming trastuzumab resistance caused by PIK3CA mutations. S6K phosphorylation is a possibly useful pharmacodynamic marker in HER2-targeted therapy.

Phase I/II study of cisplatin combined with weekly paclitaxel in patients with advanced non-small-cell lung cancer.

To determine the maximum-tolerated dose (MTD) and the recommended dose (RD) of paclitaxel administered weekly with a fixed dose of cisplatin, and to assess the toxicity and activity of this combination, we conducted a phase I/II trial in patients with advanced non-small-cell lung cancer (NSCLC). In this study, patients with stage IIIB/IV NSCLC were eligible. Paclitaxel, at a starting dose of 40 mg x m(-2) week(-1) on days 1, 8, and 15, was combined with a fixed dose of cisplatin 80 mg x m(-2) on day 1. Chemotherapy was given in a 4-week cycle. In this phase I/II study, 38 patients were enrolled. Dose-limiting toxicities (DLT) were neutropenia, fatigue, and omission of treatment due to leucopenia, thrombocytopenia, or febrile neutropenia. The MTD and RD were estimated to be 70 mg x m(-2). Of the 37 assessable patients, 23 had a partial response and one had a complete response. Overall response rate was 62.1% (95% confidence interval (CI): 46.5-77.7%). The progression-free survival, the median survival time, and the 1-year survival rate were 5.5 months, 13.7 months, and 56.9%, respectively. This regimen is tolerable and very active against advanced NSCLC, and its efficacy should be confirmed in a phase III study.

Japanese experience with second-line chemotherapy with low-dose (60 mg/M2) docetaxel in patients with advanced non-small-cell lung cancer.

PURPOSE: To assess the efficacy and toxicity of relatively low-dose docetaxel (60 mg/m2) for previously treated advanced non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Patients with advanced (clinical stage IIIA-IV) NSCLC who had previously undergone at least one series of chemotherapy were enrolled. Previous paclitaxel use was allowed, but docetaxel was not. Docetaxel was administered at an initial dose of 60 mg/m2 intravenously on day 1 over 90 min every 3 weeks. RESULTS: From June 1997 to November 1999, 22 patients were entered into this study. The total number of cycles delivered to 22 patients was 53, with a median per patient of 2. Four patients achieved a partial response (PR), and the overall response rate was 18.2% (95% confidence interval 5.1-40.3%). The median time to progression was 13.7 weeks. The median survival time was 7.8 months, and the 1-year survival rate was 25%. About 73% of patients experienced grade 3 or 4 neutropenia. Neutropenic fever was observed in four patients (18%). Non-hematologic toxicities were generally mild. No treatment-related deaths occurred. CONCLUSIONS: Although the validity of the results of this study is limited due to the small and monoracial study population examined, low-dose (60 mg/m2) docetaxel for previously treated advanced NSCLC appears to yield antitumor activity and survival benefit comparable to those obtained with the conventional dose (100 mg/m2).