LIN28B Underlies the Pathogenesis of a Subclass of Ewing Sarcoma LIN28B Control of EWS-FLI1 Stability.

Ewing sarcoma (EwS) is associated with poor prognosis despite current multimodal therapy. Targeting of EWS-FLI1, the fusion protein responsible for its pathogenesis, and its principal downstream targets has not yet produced satisfactory therapeutic options, fueling the search for alternative approaches. Here, we show that the oncofetal RNA-binding protein LIN28B regulates the stability of EWS-FLI1 mRNA in ~10% of EwSs. LIN28B depletion in these tumors leads to a decrease in the expression of EWS-FLI1 and its direct transcriptional network, abrogating EwS cell self-renewal and tumorigenicity. Moreover, pharmacological inhibition of LIN28B mimics the effect of LIN28B depletion, suggesting that LIN28B sustains the emergence of a subset of EwS in which it also serves as an effective therapeutic target.

Systemic oncolytic herpes virus therapy of poorly immunogenic prostate cancer metastatic to lung.

PURPOSE: Our goal was to evaluate whether systemic administration of NV1042, an interleukin-12 (IL-12)-expressing oncolytic herpes simplex virus, and its noncytokine parental vector NV1023 are effective against preexisting metastatic prostate cancer in an immunocompetent mice model. EXPERIMENTAL DESIGN: Metastatic TRAMP-C2 lung tumors established in C57Bl/6 or nude mice were treated on day 21 with four i.v. administrations of NV1042 or NV1023 and sacrificed on day 42 to assess virus efficacy and the potential mechanism of efficacy. RESULTS: NV1042 or NV1023 treatment was similarly effective in eliminating extrapleural and hemorrhagic tumors present in mock-treated mice. However, NV1042 was further effective compared with NV1023 in controlling the growth of lung tumors (as determined by mean surface tumor nodule number, lung weights, and surface tumor burden) and in extending survival. NV1042-treated mice exhibited a transient increase of serum IL-12 1 day posttreatment, whereas IL-12 levels in tumor bearing lungs persisted a further 2 days at least. Only splenocytes from NV1042-treated mice secreted IFN-gamma in response to TRAMP-C2 stimulation and displayed natural killer activity. The IL-12-mediated enhancement observed with NV1042 in the syngeneic model was abrogated in athymic mice treated in a similar manner, thus indicating a role for T cells in the augmented efficacy of NV1042 virus. CONCLUSIONS: Systemic administration of the IL-12-expressing NV1042 virus is more effective than its noncytokine parent, NV1023, against preestablished metastatic lung tumors. Given the clinical safety profile of NV1020, the parental vector of NV1023, and NV1042's enhanced efficacy and ability to activate the host immune system, NV1042 merits clinical consideration for treating metastatic prostate cancers.

Solitary myofibroma of the sclera.

PURPOSE: To report a novel case of solitary myofibroma involving the sclera. METHODS: Case report and review of the literature. RESULTS: A 19-year-old woman had an expanding and painful epibulbar mass clinically diagnosed as nodular scleritis that did not respond to anti-inflammatory therapy. A biopsy showed a proliferation of spindle-shaped cells that reacted strongly positively with immunoperoxidase stains for vimentin and smooth-muscle actin. The diagnosis of solitary myofibroma was made. Six months postoperatively, the patient was well, and the lesion had not recurred. CONCLUSIONS: Myofibroma should be considered in the differential diagnosis of an epibulbar mass, especially in the setting that would mimic nodular scleritis.

The NOTCH1/SNAIL1/MEF2C Pathway Regulates Growth and Self-Renewal in Embryonal Rhabdomyosarcoma.

Tumor-propagating cells (TPCs) share self-renewal properties with normal stem cells and drive continued tumor growth. However, mechanisms regulating TPC self-renewal are largely unknown, especially in embryonal rhabdomyosarcoma (ERMS)-a common pediatric cancer of muscle. Here, we used a zebrafish transgenic model of ERMS to identify a role for intracellular NOTCH1 (ICN1) in increasing TPCs by 23-fold. ICN1 expanded TPCs by enabling the de-differentiation of zebrafish ERMS cells into self-renewing myf5+ TPCs, breaking the rigid differentiation hierarchies reported in normal muscle. ICN1 also had conserved roles in regulating human ERMS self-renewal and growth. Mechanistically, ICN1 upregulated expression of SNAIL1, a transcriptional repressor, to increase TPC number in human ERMS and to block muscle differentiation through suppressing MEF2C, a myogenic differentiation transcription factor. Our data implicate the NOTCH1/SNAI1/MEF2C signaling axis as a major determinant of TPC self-renewal and differentiation in ERMS, raising hope of therapeutically targeting this pathway in the future.

In vivo imaging of tumor-propagating cells, regional tumor heterogeneity, and dynamic cell movements in embryonal rhabdomyosarcoma.

Embryonal rhabdomyosarcoma (ERMS) is an aggressive pediatric sarcoma of muscle. Here, we show that ERMS-propagating potential is confined to myf5+ cells and can be visualized in live, fluorescent transgenic zebrafish. During early tumor growth, myf5+ ERMS cells reside adjacent normal muscle fibers. By late-stage ERMS, myf5+ cells are reorganized into distinct regions separated from differentiated tumor cells. Time-lapse imaging of late-stage ERMS revealed that myf5+ cells populate newly formed tumor only after seeding by highly migratory myogenin+ ERMS cells. Moreover, myogenin+ ERMS cells can enter the vasculature, whereas myf5+ ERMS-propagating cells do not. Our data suggest that non-tumor-propagating cells likely have important supportive roles in cancer progression and facilitate metastasis.

Monophasic synovial sarcoma of the liver.

We report a hepatic monophasic synovial sarcoma in a 60-year-old woman who presented with right upper quadrant pain subsequent to an intrahepatic bleed from a highly vascular tumor mass. Imaging studies showed a dominant tumor mass in the right hepatic lobe with multiple satellite nodules. A detailed physical examination and radiologic workup failed to reveal a primary tumor elsewhere. A right partial hepatectomy was performed with a preoperative differential diagnosis of angiosarcoma versus hepatocellular carcinoma. The morphologic, immunophenotypic, and cytogenetic findings (t(X;18)(p11.2;icq11.2)) were consistent with a monophasic synovial sarcoma. Postoperative clinical evaluation of the extremities and a positron emission tomographic scan performed 4 weeks after surgery showed no evidence of recurrent or metastatic disease. The patient was started on an aggressive 4-drug chemotherapy regimen, but died 3 months thereafter from widespread metastatic disease. No autopsy was performed. The presence of multiple lesions in the liver certainly suggests the possibility of metastatic disease. It would, however, be very unusual for a synovial sarcoma to present as an occult primary, and the negative radiologic workup 1 month after the partial hepatectomy also argues against this possibility. The clinical presentation, radiographic findings, and subsequent course in this patient was therefore most consistent with a primary monophasic synovial sarcoma of the liver.