NAB2-STAT6 drives an EGR1-dependent neuroendocrine program in Solitary Fibrous Tumors.

The pathogenesis of many rare tumor types is poorly understood, preventing the design of effective treatments. Solitary fibrous tumors (SFTs) are neoplasms of mesenchymal origin that affect 1/1,000,000 individuals every year and are clinically assimilated to soft tissue sarcomas. SFTs can arise throughout the body and are usually managed surgically. However, 30-40% of SFTs will relapse local-regionally or metastasize. There are no systemic therapies with durable activity for malignant SFTs to date. The molecular hallmark of SFTs is a gene fusion between the NAB2 and STAT6 loci on chromosome 12, resulting in a chimeric protein of poorly characterized function called NAB2-STAT6. We use primary samples and an inducible cell model to discover that NAB2-STAT6 operates as a transcriptional coactivator for a specific set of enhancers and promoters that are normally targeted by the EGR1 transcription factor. In physiological conditions, NAB2 is primarily localized to the cytoplasm and only a small nuclear fraction is available to operate as a co-activator of EGR1 targets. NAB2-STAT6 redirects NAB1, NAB2, and additional EGR1 to the nucleus and bolster the expression of neuronal EGR1 targets. The STAT6 moiety of the fusion protein is a major driver of its nuclear localization and further contributes to NAB2's co-activating abilities. In primary tumors, NAB2-STAT6 activates a neuroendocrine gene signature that sets it apart from most sarcomas. These discoveries provide new insight into the pathogenesis of SFTs and reveal new targets with therapeutic potential.

Gemcitabine and docetaxel in patients with unresectable leiomyosarcoma: results of a phase II trial.

PURPOSE: Few chemotherapy agents are active in leiomyosarcoma (LMS), particularly LMS that has progressed after doxorubicin treatment. We sought to determine the response to gemcitabine plus docetaxel among patients with LMS. PATIENTS AND METHODS: Patients with unresectable LMS of uterine (n = 29) or other (n = 5) primary sites who did not respond to zero to two prior chemotherapy regimens were enrolled onto a phase II study of gemcitabine 900 mg/m(2) intravenously (i.v.) on days 1 and 8 plus docetaxel 100 mg/m(2) i.v. on day 8 with granulocyte colony-stimulating factor given subcutaneously on days 9 to 15, delivered every 21 days. Patients with prior pelvic radiation received 25% lower doses of both agents. Gemcitabine was delivered over 30 or 90 minutes in cycles 1 and 2 and by 90-minute infusion in all subsequent cycles. Pharmacokinetic studies assessed in vivo differences in gemcitabine concentrations with different rates of infusion. RESULTS: Thirty-four patients (median age, 55 years; range, 32 to 74 years) have enrolled. Fourteen had received prior pelvic radiation. Sixteen of 34 patients had progressed after doxorubicin-based therapy; 18 had no prior chemotherapy. Among 34 patients, complete response was observed in three patients and partial response in 15, for an overall response rate of 53% (95% confidence interval, 35% to 70%). Seven patients had stable disease. Fifty percent of patients previously treated with doxorubicin responded. Hematologic toxicity was common (neutropenia: grade 3, 15%; grade 4, 6%; thrombocytopenia: grade 3, 26%; grade 4, 3%), but neutropenic fever (6%) and bleeding events (0%) were rare. The median time to progression was 5.6 months (range, 4 to 10 months). CONCLUSION: Gemcitabine plus docetaxel is tolerable and highly active in treated and untreated patients with LMS.

R1507, a monoclonal antibody to the insulin-like growth factor 1 receptor, in patients with recurrent or refractory Ewing sarcoma family of tumors: results of a phase II Sarcoma Alliance for Research through Collaboration study.

PURPOSE: The type 1 insulin-like growth factor 1 receptor (IGF-1R) has been implicated in the pathogenesis of the Ewing sarcoma family of tumors (ESFT). We conducted a multicenter phase II study of the fully human IGF-1R monoclonal antibody R1507 in patients with recurrent or refractory ESFT. PATIENTS AND METHODS: Patients ≥ 2 years of age with refractory or recurrent ESFT received R1507 at doses of 9 mg/kg intravenously one a week or 27 mg/kg intravenously every three weeks. Response was measured by using WHO criteria. Tumor imaging was performed every 6 weeks for 24 weeks and then every 12 weeks. RESULTS: From December 2007 through April 2010, 115 eligible patients from 31 different institutions were enrolled. The median age was 25 years (range, 8 to 78 years). The location of the primary tumor was bone in 57% of patients and extraskeletal in 43% of patients. A total of 109 patients were treated with R1507 9 mg/kg/wk, and six patients were treated with 27 mg/kg/3 wk. The overall complete response/partial response rate was 10% (95% CI, 4.9% to 16.5%). The median duration of response was 29 weeks (range, 12 to 94 weeks), and the median overall survival was 7.6 months (95% CI, 6 to 9.7 months). Ten of 11 responses were observed in patients who presented with primary bone tumors (P = .016). The most common adverse events of grades 3 to 4 were pain (15%), anemia (8%), thrombocytopenia (7%), and asthenia (5%). CONCLUSION: R1507 was a well-tolerated agent that had meaningful and durable benefit in a subgroup of patients with ESFT. The identification of markers that are predictive of a benefit is necessary to fully capitalize on this approach.

Clinical outcomes of systemic therapy for patients with deep fibromatosis (desmoid tumor).

BACKGROUND: In the current study, the authors examined the outcomes of patients with desmoid tumors who received systemic therapy at a single institution to provide a basis for the examination of newer agents. METHODS: Records of patients with desmoid tumors who were treated with chemotherapy at the study institution were reviewed. The activity of nonsteroidal anti-inflammatory drugs was not addressed. Patients without measurable disease and those receiving therapy could not be documented, and those receiving prophylactic therapy were excluded. RESULTS: A total of 68 patients received 157 lines of therapy. At the time of last follow-up, 9 patients had died, 7 of progressive disease. The cohort was 62% female, with a median age of 32.5 years. Approximately 32% of the patients had Gardner syndrome. The median follow-up was 63 months, and patients received a median of 2 lines of therapy. An intra-abdominal primary tumor location was the most common (44%). The greatest Response Evaluation Criteria in Solid Tumors (RECIST) response rate was observed with anthracyclines and hormonal therapy and the lowest response was noted with single-agent dacarbazine/temozolomide or tyrosine kinase inhibitors, principally imatinib. On multivariate analysis, macroscopic nodular morphology and the presence of Gardner syndrome were the only tumor factors found to be associated with a greater time to disease progression. CONCLUSIONS: Compared with other agents, antiestrogens and anthracycline-containing regimens appear to be associated with a higher radiological response rate against desmoid tumors. Systemic therapy can be successful in patients with desmoid tumors, and is a viable option in lieu of morbid or disabling surgery.