Abstract OT1-12-02: Biomarker study of patients with HER2-negative metastatic breast cancer receiving combination therapy with nivolumab, bevacizumab and paclitaxel as first-line treatment (WJOG9917BTR)

Background: In recent years, anti-PD-1 antibody, an immune checkpoint inhibitor, has been developed for the treatment of various types of cancer, including breast cancer. Synergistic effects of nivolumab, paclitaxel and bevacizumab are expected, based on various preclinical data, when these drugs are administered in combination. A biomarker study is ongoing to evaluate the immune status of patients participating in the NEWBEAT trial, which is a phase II trial of nivolumab + paclitaxel + bevacizumab therapy as first-line treatment for patients with metastatic or recurrent HER2-negative breast cancer. Methods: HER2-negative breast cancer patients from the WJOG9917B (NEWBEAT) trial are enrolled in this biomarker study. To explore new biomarkers for combined treatment of breast cancer with immune-checkpoint inhibitors and anti-vascular endothelial growth factor antibodies, we propose to conduct multicolor immunohistochemistry (IHC) assays for immunomonitoring of the intra-tumor environment, such as the expressions of PD-L1, CD4 and CD8. Blood samples are collected before the start of treatment and at four time-points during the treatment, to determine, using a multicolor flow cytometry panel, the numbers of circulating immunosuppressive cells, such as regulatory T cells, myeloid-derived suppressor cells and tumor-associated macrophages (M2). In the NEWBEAT trial, patients receive nivolumab 240 mg/body on days 1 and 15, paclitaxel 90 mg/m2 on days 1, 8 and 15, and bevacizumab 10 mg/kg on days 1 and 15 every 4 weeks until disease progression. The primary endpoint is the objective response rate, and the key secondary endpoints include progression-free survival, overall survival, and toxicity of the protocol treatment. A total of 51 patients will be enrolled and the enrollment period will be one year. This trial opened to accrual in February 2018. Clinical trial registry number: UMIN000029590

Citation Format: Ozaki Y, Kitano S, Matsumoto K, Takahashi M, Mukohara T, Futamura M, Masuda N, Tsurutani J, Yoshimura K, Minami H, Takano T. Biomarker study of patients with HER2-negative metastatic breast cancer receiving combination therapy with nivolumab, bevacizumab and paclitaxel as first-line treatment (WJOG9917BTR) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT1-12-02.

P5-06-04: Mechanisms of Acquired Resistance to Insulin-Like Growth Factor 1 Receptor Inhibitor in MCF-7 Breast Cancer Cell Line

Background: No studies have yet clarified the mechanism of acquired resistance to insulin-like growth factor-1 receptor (IGF-1R) tyrosine kinase inhibitor (TKI). Our previous study of 16 breast cancer cell lines found that only MCF-7 expressed high levels of insulin receptor substrate (IRS)-1 and was sensitive to the IGF-1R-TKI NVP-AEW541.

Material and Methods: We developed a model of acquired resistance to NVP-AEW541 by continuously exposing MCF-7 cells to NVP-AEW541, naming the model MCF-7-NR. To explore the mechanism of acquired resistance to NVP-AEW541, the effects of NVP-AEW541 on cell growth and IGF-1R signaling in MCF-7 and MCF-7-NR cells were examined.

Results: With Western blot analysis, we found that MCF-7-NR had much lower levels of IRS-1 than parental MCF-7. While phosphorylation of Akt was completely inhibited by administration of NVP-AEW541 (3 μM) in both cell lines, phosphorylation of S6K remained high only in MCF-7-NR. The notion of Akt-independent S6K phosphorylation in MCF-7-NR was further supported by the fact that cell growth and phosphorylation of S6K was affected by administration of the Akt inhibitor perifosine to a lesser degree in MCF-7-NR than in MCF-7. Further, the mTOR inhibitor everolimus inhibited phosphorylation of S6K and cell growth equally in both lines. Screening of MCF-7 and MCF-7-NR lines for phosphorylation of 42 receptor tyrosine kinases with and without 3μM NVP-AEW541 showed that Tyro3 phosphorylation remained high only in MCF-7-NR cells. Gene silencing of Tyro3 using siRNA resulted in reduced cell growth, decreased phosphorylation of phosphoinositide-dependent kinase-1 (PDK-1) and protein kinase C α/βII, reduced expression of cyclin D1 in the MCF-7-NR line, with minimal effects evident in the MCF-7 line.

Discussion: Findings from our current study support the possibility of predicting sensitivity to NVP-AEW541 by measuring IRS-1 expression, as hypothesized in our previous study. Akt-independent activation of mTOR/S6K by an as-yet-undefined mechanism appears to induce acquired resistance to NVP-AEW541, and as such mTOR inhibitors may have therapeutic value. Tyro3 upregulation and migration of control of cellular growth and cyclin D1 expression may also induce resistance to NVP-AEW541. Although the validity of these findings should be evaluated in further preclinical studies and eventually in clinical trials, our observations may lead to individualized use of NVP-AEW541 and the development of “backup drugs” against tumors that acquire resistance to NVP-AEW541.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-06-04.

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 m⁻² week⁻¹ on days 1, 8, and 15, was combined with a fixed dose of cisplatin 80 mg 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 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).