Background Tissue factor (TF) is a transmembrane protein that acts as a receptor for activated coagulation factor VII (FVIIa), initiating the coagulation cascade. Recent studies demonstrate that expression of tumor-derived TF also mediates intracellular signaling relevant to tumor growth and apoptosis. Our present study investigates the possible mechanism by which the interaction between TF and FVIIa regulates chemotherapy resistance in neuroblastoma cell lines. Methods Gene and siRNA transfection was used to enforce TF expression in a TF-negative neuroblastoma cell line and to silence endogenous TF expression in a TF-overexpressing neuroblastoma line, respectively. The expression of TF, Bcl-2, STAT5, and Akt as well as the phosphorylation of STAT5 and Akt in gene transfected cells or cells treated with JAK inhibitor and LY294002 were determined by Western blot assay. Tumor cell growth was determined by a clonogenic assay. Cytotoxic and apoptotic effect of doxorubicin on neuroblastoma cell lines was analyzed by WST assay and annexin-V staining (by flow cytometry) respectively. Results Enforced expression of TF in a TF-negative neuroblastoma cell line in the presence of FVIIa induced upregulation of Bcl-2, leading to resistance to doxorubicin. Conversely, inhibition of endogenous TF expression in a TF-overexpressing neuroblastoma cell line using siRNA resulted in down-regulation of Bcl-2 and sensitization to doxorubicin-induced apoptosis. Additionally, neuroblastoma cells expressing high levels of either endogenous or transfected TF treated with FVIIa readily phosphorylated STAT5 and Akt. Using selective pharmacologic inhibitors, we demonstrated that JAK inhibitor I, but not the PI3K inhibitor LY294002, blocked the TF/FVIIa-induced upregulation of Bcl-2. Conclusion This study shows that in neuroblastoma cell lines overexpressed TF ligated with FVIIa produced upregulation of Bcl-2 expression through the JAK/STAT5 signaling pathway, resulting in resistance to apoptosis. We surmise that this TF-FVIIa pathway may contribute, at least in part, to chemotherapy resistance in neuroblastoma.

Introduction: Subcutaneous panniculitis-like T-cell lymphoma (SPTL-AB) and cutaneous gamma/delta T-cell lymphoma (CGD-TCL) are rare T-cell lymphomas with varying clinical courses. There is no standard treatment, although chemotherapy and hematopoietic stem cell transplantation are commonly used. We describe results using bexarotene for children and adults with these disorders. Methods: We identified 15 patients (12 adults, 3 children) who were treated with bexarotene between 2000 and 2010 from the Memorial Sloan-Kettering Cancer Center lymphoma database, the Stanford Cancer Center Registry, and the National Cancer Institute (NCI) pediatric lymphoma database. There were 8 females and 7 males, with a median age of 45 years (range, 3 years to 85 years). All patients had stage IV disease. Two of 15 and 4 of 15 patients had documented CGD-TCL and SPTL-AB, respectively; others were presumed to have SPTL-AB. Bexarotene was administered at flat doses corresponding to 91 to 339 mg/m 2 /d. Two of 15 patients received concurrent denileukin diftitox. Two children received bexarotene as maintenance therapy and were not evaluable for response. Results: Among those treated with bexarotene alone, the overall response rate (ORR) was 82% (6/11 complete response [CR], 3/11 partial response [PR]). One of the 2 patients treated with concomitant denileukin diftitox responded for an ORR of 10/13 (77%), including 54% CR and 23% PR. Median progression-free survival was 38.4 months; median duration of response was 26.3 months. Six patients developed hypothyroidism and 9 developed hyperlipidemia; one patient developed dose-limiting hypertriglyceridemia. One pediatric patient developed insulin-dependent diabetes mellitus. Conclusions: In this retrospective series, bexarotene showed a high response rate in SPTL-AB and CGD-TCL. It was generally well-tolerated with durable responses; therefore, bexarotene represents a promising therapy for children and adults with these disorders.