Multiple receptor tyrosine kinases promote the in vitro phenotype of metastatic human osteosarcoma cell lines.

The survival rate for osteosarcoma patients with localized disease is 70% and only 25% for patients with metastases. Therefore, novel therapeutic and prognostic tools are needed. In this study, extensive screening and validation strategies identified Axl, EphB2, FGFR2, IGF-1R and Ret as specific receptor tyrosine kinases (RTKs) that are activated and promote the in vitro phenotype of two genetically different metastatic osteosarcoma cell lines. Initial phosphoproteomic screening identified twelve RTKs that were phosphorylated in 143B and/or LM7 metastatic human osteosarcoma cells. A small interfering RNA (siRNA) screen demonstrated that siRNA pools targeting ten of the twelve RTKS inhibited the in vitro phenotype of one or both cell lines. To validate the results, we individually tested the four siRNA duplexes that comprised each of the effective siRNA pools from the initial screen. The pattern of phenotype inhibition replicated the pattern of mRNA knockdown by the individual duplexes for seven of the ten RTKs, indicating the effects are consistent with on-target silencing. Five of those seven RTKs were further validated using independent approaches including neutralizing antibodies (IGF-1R), antisense-mediated knockdown (EphB2, FGFR2, and Ret) or small molecule inhibitors (Axl), indicating that those specific RTKs promote the in vitro behavior of metastatic osteosarcoma cell lines and are potential therapeutic targets for osteosarcoma. Immunohistochemistry demonstrated that Axl is frequently activated in osteosarcoma patient biopsy samples, further supporting our screening and validation methods to identify RTKs that may be valuable targets for novel therapies for osteosarcoma patients.

Postoperative nomogram for survival of patients with retroperitoneal sarcoma treated with curative intent.

BACKGROUND: Current American Joint Committee on Cancer retroperitoneal sarcoma (RPS) staging is not representative of patients with RPS specifically and has limited discriminative power. Our objective was to develop a RPS disease-specific nomogram capable of stratifying patients based on probability of overall survival (OS) after resection. PATIENTS AND METHODS: In all, 1118 RPS patients were evaluated at our institution (1996-2006). Patients with resectable, nonmetastatic disease were selected (n = 343) and baseline, treatment and outcome variables were retrieved. A nomogram was created and its performance was evaluated by calculating its discrimination (concordance index) and calibration and by subsequent internal validation. RESULTS: Median follow-up and OS were 50 and 59 months, respectively. Independent predictors of OS were included in the nomogram: age (> or = 65), tumor size (> or = 15 cm), type of presentation (primary versus recurrent), multifocality, completeness of resection and histology. The concordance index was 0.73 [95% confidence interval (CI) 0.71-0.75] and the calibration was excellent, with all observed outcomes within the 95% CI of each predicted survival probability. CONCLUSIONS: A RPS-specific postoperative nomogram was developed. It improves RPS staging by allowing a more dynamic and robust disease-specific risk stratification. This prognostic tool can help in patient counseling and for selection of high-risk patients that may benefit from adjuvant therapies or inclusion into clinical trials.

Dual blockade of EGFR and ERK1/2 phosphorylation potentiates growth inhibition of breast cancer cells.

One of the major targets for breast cancer therapy is the epidermal growth factor receptor (EGFR) and related receptors, which signal via different signal transduction pathways including the mitogen-activated protein kinase (MAPK) pathway. This study determined whether there is a correlation between EGFR/HER2 status and MAPK (ERK1/2) phosphorylation in breast cancer cells, and how this affects the response to an inhibitor of the receptors. Expression of EGFR, HER2 and phosphorylated ERK1/2 were measured by immunoblotting in a panel of breast cancer cell lines. Several lines expressed high levels of pERK1/2, with no obvious correlation with the level of EGFR/HER2. The EGFR tyrosine kinase inhibitor PKI166 inhibited growth and induced apoptosis in some cells with high levels of growth factor receptors (MDA-MB-468, SUM149, SKBR3), but was less effective in cells that also had high basal ERK1/2 activity (MDA-MB-231). The combination of an inhibitor of MAPK signalling (U0126) and PKI166 produced significantly more inhibition and apoptosis than either agent alone. This suggests that constitutive activation of the MAPK pathway may bypass inhibition of EGFR/HER2 tyrosine kinases, and lead to insensitivity to agents targeting the receptors. However, inhibiting both EGFR/HER2 and MAPK signalling can result in significant growth inhibition and apoptosis of EGFR-expressing breast cancer cells.