Inhibition of the CXCR4/CXCL12 chemokine pathway reduces the development of murine pulmonary metastases.

Metastasis continues to be the leading cause of mortality for patients with cancer. High expression of the chemokine receptor CXCR4 correlates with poor prognosis in many cancers, including osteosarcoma and melanoma. CXCL12, the ligand for CXCR4, is expressed at high levels in the lung and lymph node, which are the primary sites to which these tumors metastasize respectively. These findings suggest that therapy aimed at disruption of this specific receptor/ligand complex may lead to a decrease in metastases. CTCE-9908, a small peptide CXCR4 antagonist was utilized in two murine metastasis models to test this hypothesis. Treatment of osteosarcoma cells in vitro with CTCE-9908 led to the following changes: decreased adhesion, decreased migration, decreased invasion, and decreased growth rate. Following tail vein injection of osteosarcoma cells, mice that were treated with CTCE-9908 had a 50% reduction in the number of gross metastatic lung nodules and a marked decrease in micro-metastatic disease. Similar findings were observed following injection of melanoma cells and treatment with CTCE-9908. However, these results could only be consistently reproduced when the cells were pre-treated with the inhibitor. A novel ex vivo luciferase assay showed decreased numbers of cells in the lung immediately after injection into mice, when treated with CTCE-9908, suggesting the importance of interactions between the receptor and the ligand. Our findings show that inhibition of the CXCR4/CXCL12 pathway decreases metastatic disease in two murine tumor models and expands on previous reports to describe potential mechanisms of action.

Phosphoprotein pathway mapping: Akt/mammalian target of rapamycin activation is negatively associated with childhood rhabdomyosarcoma survival.

Mapping of protein signaling networks within tumors can identify new targets for therapy and provide a means to stratify patients for individualized therapy. Despite advances in combination chemotherapy, the overall survival for childhood rhabdomyosarcoma remains approximately 60%. A critical goal is to identify functionally important protein signaling defects associated with treatment failure for the 40% nonresponder cohort. Here, we show, by phosphoproteomic network analysis of microdissected tumor cells, that interlinked components of the Akt/mammalian target of rapamycin (mTOR) pathway exhibited increased levels of phosphorylation for tumors of patients with short-term survival. Specimens (n = 59) were obtained from the Children's Oncology Group Intergroup Rhabdomyosarcoma Study (IRS) IV, D9502 and D9803, with 12-year follow-up. High phosphorylation levels were associated with poor overall and poor disease-free survival: Akt Ser(473) (overall survival P < 0.001, recurrence-free survival P < 0.0009), 4EBP1 Thr(37/46) (overall survival P < 0.0110, recurrence-free survival P < 0.0106), eIF4G Ser(1108) (overall survival P < 0.0017, recurrence-free survival P < 0.0072), and p70S6 Thr(389) (overall survival P < 0.0085, recurrence-free survival P < 0.0296). Moreover, the findings support an altered interrelationship between the insulin receptor substrate (IRS-1) and Akt/mTOR pathway proteins (P < 0.0027) for tumors from patients with poor survival. The functional significance of this pathway was tested using CCI-779 in a mouse xenograft model. CCI-779 suppressed phosphorylation of mTOR downstream proteins and greatly reduced the growth of two different rhabdomyosarcoma (RD embryonal P = 0.00008; Rh30 alveolar P = 0.0002) cell lines compared with controls. These results suggest that phosphoprotein mapping of the Akt/mTOR pathway should be studied further as a means to select patients to receive mTOR/IRS pathway inhibitors before administration of chemotherapy.