Bone Sarcomas in Pediatrics: Progress in Our Understanding of Tumor Biology and Implications for Therapy.

The pediatric bone sarcomas osteosarcoma and Ewing sarcoma represent a tremendous challenge for the clinician. Though less common than acute lymphoblastic leukemia or brain tumors, these aggressive cancers account for a disproportionate amount of the cancer morbidity and mortality in children, and have seen few advances in survival in the past decade, despite many large, complicated, and expensive trials of various chemotherapy combinations. To improve the outcomes of children with bone sarcomas, a better understanding of the biology of these cancers is needed, together with informed use of targeted therapies that exploit the unique biology of each disease. Here we summarize the current state of knowledge regarding the contribution of receptor tyrosine kinases, intracellular signaling pathways, bone biology and physiology, the immune system, and the tumor microenvironment in promoting and maintaining the malignant phenotype. These observations are coupled with a review of the therapies that target each of these mechanisms, focusing on recent or ongoing clinical trials if such information is available. It is our hope that, by better understanding the biology of osteosarcoma and Ewing sarcoma, rational combination therapies can be designed and systematically tested, leading to improved outcomes for a group of children who desperately need them.

New, tolerable γ-secretase inhibitor takes desmoid down a notch.

A phase I trial of PF-03084014, an oral reversible γ-secretase inhibitor, in solid tumor malignancies shows drug tolerability in patients. Evidence of Notch pathway inhibition was demonstrated in peripheral blood. A surprisingly high rate of response was seen in desmoid tumors, a rare but sometimes locally aggressive sarcoma.

The narrow-spectrum HDAC inhibitor entinostat enhances NKG2D expression without NK cell toxicity, leading to enhanced recognition of cancer cells.

PURPOSE: Natural killer (NK) cell cytotoxicity correlates with the ligation of activating receptors (e.g., NKG2D) by their ligands (e.g., MHC class I-related chains [MIC] A and B) on target cells. Histone deacetylase inhibitors (HDACi) at high concentrations inhibit tumor growth and can increase NKG2D ligand expression on tumor targets, but are widely regarded as toxic to NK cells. METHODS: We investigated the mechanism of entinostat, a benzamide-derivative narrow-spectrum HDACi, in augmenting the cytotoxicity of NK cells against human colon carcinoma and sarcoma by assessing gene and protein expression, histone acetylation, and cytotoxicity in in vitro and murine models. RESULTS: We observed that entinostat dose- and time-dependent increase in MIC expression in tumor targets and NKG2D in primary human NK cells, both correlating with increased acetylated histone 3 (AcH3) binding to associated promoters. Entinostat pretreatment of colon carcinoma and sarcoma cells, NK cells, or both led to enhanced overall cytotoxicity in vitro, which was reversed by NKG2D blockade, and inhibited growth of tumor xenografts. Lastly, we showed decreased expression of MICA and ULBP2 transcription in primary human osteosarcoma. CONCLUSIONS: Entinostat enhances NK cell killing of cancer cells through upregulation of both NKG2D and its ligands, suggesting an attractive approach for augmenting NK cell immunotherapy of solid tumors such as colon carcinoma and sarcomas.

Understanding the role of Notch in osteosarcoma.

The Notch pathway has been described as an oncogene in osteosarcoma, but the myriad functions of all the members of this complex signaling pathway, both in malignant cells and nonmalignant components of tumors, make it more difficult to define Notch as simply an oncogene or a tumor suppressor. The cell-autonomous behaviors caused by Notch pathway manipulation may vary between cell lines but can include changes in proliferation, migration, invasiveness, oxidative stress resistance, and expression of markers associated with stemness or tumor-initiating cells. Beyond these roles, Notch signaling also plays a vital role in regulating tumor angiogenesis and vasculogenesis, which are vital aspects of osteosarcoma growth and behavior in vivo. Further, osteosarcoma cells themselves express relatively low levels of Notch ligand, making it likely that nonmalignant cells, especially endothelial cells and pericytes, are the major source of Notch activation in osteosarcoma tumors in vivo and in patients. As a result, Notch pathway expression is not expected to be uniform across a tumor but likely to be highest in those areas immediately adjacent to blood vessels. Therapeutic targeting of the Notch pathway is likewise expected to be complicated. Most pharmacologic approaches thus far have focused on inhibition of gamma secretase, a protease of the presenilin complex. This enzyme, however, has numerous other target proteins that would be expected to affect osteosarcoma behavior, including CD44, the WNT/ß-catenin pathway, and Her-4. In addition, Notch plays a vital role in tissue and organ homeostasis in numerous systems, and toxicities, especially GI intolerance, have limited the effectiveness of gamma secretase inhibitors. New approaches are in development, and the downstream targets of Notch pathway signaling also may turn out to be good targets for therapy. In summary, a full understanding of the complex functions of Notch in osteosarcoma is only now unfolding, and this deeper knowledge will help position the field to better utilize novel therapies as they are developed.

Developmental pathways hijacked by osteosarcoma.

Cancer of any type often can be described by an arrest, alteration or disruption in the normal development of a tissue or organ, and understanding of the normal counterpart's development can aid in understanding the malignant state. This is certainly true for osteosarcoma and the normal developmental pathways that guide osteoblast development that are changed in the genesis of osteogenic sarcoma. A carefully regulated crescendo-decrescendo expression of RUNX2 accompanies the transition from mesenchymal stem cell to immature osteoblast to mature osteoblast. This pivotal role is controlled by several pathways, including bone morphogenic protein (BMP), Wnt/ß-catenin, fibroblast growth factor (FGF), and protein kinase C (PKC). The HIPPO pathway and its downstream target YAP help to regulate proliferation of immature osteoblasts and their maturation into non-proliferating mature osteoblasts. This pathway also helps regulate expression of the mature osteoblast protein osteocalcin. YAP also regulates expression of MT1-MMP, a membrane-bound matrix metalloprotease responsible for remodeling the extracellular matrix surrounding the osteoblasts. YAP, in turn, can be regulated by the ERBB family protein Her-4. Osteosarcoma may be thought of as a cell held at the immature osteoblast stage, retaining some of the characteristics of that developmental stage. Disruptions of several of these pathways have been described in osteosarcoma, including BMP, Wnt/b-catenin, RUNX2, HIPPO/YAP, and Her-4. Further, PKC can be activated by several receptor tyrosine kinases implicated in osteosarcoma, including the ERBB family (EGFR, Her-2 and Her-4 in osteosarcoma), IGF1R, FGF, and others. Understanding these functions may aid in the understanding the mechanisms underpinning clinical observations in osteosarcoma, including both the lytic and blastic phenotypes of tumors, the invasiveness of the disease, and the tendency for treated tumors to ossify rather than shrink. Through a better understanding of the relationship between normal osteoblast development and osteosarcoma, we may gain insights into novel therapeutic avenues and improved outcomes.

Understanding the Biology of Bone Sarcoma from Early Initiating Events through Late Events in Metastasis and Disease Progression.

The two most common primary bone malignancies, osteosarcoma (OS), and Ewing sarcoma (ES), are both aggressive, highly metastatic cancers that most often strike teens, though both can be found in younger children and adults. Despite distinct origins and pathogenesis, both diseases share several mechanisms of progression and metastasis, including neovascularization, invasion, anoikis resistance, chemoresistance, and evasion of the immune response. Some of these processes are well-studies in more common carcinoma models, and the observation from adult diseases may be readily applied to pediatric bone sarcomas. Neovascularization, which includes angiogenesis and vasculogenesis, is a clear example of a process that is likely to be similar between carcinomas and sarcomas, since the responding cells are the same in each case. Chemoresistance mechanisms also may be similar between other cancers and the bone sarcomas. Since OS and ES are mesenchymal in origin, the process of epithelial-to-mesenchymal transition is largely absent in bone sarcomas, necessitating different approaches to study progression and metastasis in these diseases. One process that is less well-studied in bone sarcomas is dormancy, which allows micrometastatic disease to remain viable but not growing in distant sites - typically the lungs - for months or years before renewing growth to become overt metastatic disease. By understanding the basic biology of these processes, novel therapeutic strategies may be developed that could improve survival in children with OS or ES.

Complications in the surgical treatment of pediatric melanoma.

PURPOSE: The purpose of this study was to characterize the complications associated with surgical treatment of pediatric melanoma. METHODS: We retrospectively reviewed all pediatric patients who received surgical treatment for melanoma at our institution between 1992 and 2010. We compared complications between three groups: wide local excision only (WLE), WLE and sentinel lymph node biopsy (SLNB), and WLE and completion lymph node dissection (CLND). RESULTS: One hundred twenty-five patients were identified: 37 patients received WLE only, 47 received WLE and SLNB, and 41 patients had WLE and CLND. Complication rates differed between the three groups: 19% in WLE, 11% in WLE+SLNB, and 39% in WLE+CLND (P=.006). The risk of complications was significantly lower among patients having WLE+SLNB versus WLE+CLND (OR 0.19, 95% CI 0.06-0.57, P=.0032). Lymphedema was a common complication with a higher incidence in the CLND group compared to the SLNB group (19.5% vs. 2.1%, P=.01). Complications were more frequent in inguinal compared to axillary dissections (52.0% vs. 17.1%, P=.006). CONCLUSIONS: In the surgical treatment of pediatric melanoma, the addition of a completion lymph node dissection significantly increases complication risk. Thus, it is critical to determine which patients truly benefit from this procedure.

UBE4B levels are correlated with clinical outcomes in neuroblastoma patients and with altered neuroblastoma cell proliferation and sensitivity to epidermal growth factor receptor inhibitors.

BACKGROUND: The UBE4B gene, which is located on chromosome 1p36, encodes a ubiquitin ligase that interacts with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), a protein involved in epidermal growth factor receptor (EGFR) trafficking, suggesting a link between EGFR trafficking and neuroblastoma pathogenesis. The authors analyzed the roles of UBE4B in the outcomes of patients with neuroblastoma and in neuroblastoma tumor cell proliferation, EGFR trafficking, and response to EGFR inhibition. METHODS: The association between UBE4B expression and the survival of patients with neuroblastoma was examined using available microarray data sets. UBE4B and EGFR protein levels were measured in patient tumor samples, EGFR degradation rates were measured in neuroblastoma cell lines, and the effects of UBE4B on neuroblastoma tumor cell growth were analyzed. The effects of the EGFR inhibitor cetuximab were examined in neuroblastoma cells that expressed wild-type and mutant UBE4B. RESULTS: Low UBE4B gene expression is associated with poor outcomes in patients with neuroblastoma. UBE4B overexpression reduced neuroblastoma tumor cell proliferation, and UBE4B expression was inversely related to EGFR expression in tumor samples. EGFR degradation rates correlated with cellular UBE4B levels. Enhanced expression of catalytically active UBE4B resulted in reduced sensitivity to EGFR inhibition. CONCLUSIONS: The current study demonstrates associations between UBE4B expression and the outcomes of patients with neuroblastoma and between UBE4B and EGFR expression in neuroblastoma tumor samples. Moreover, levels of UBE4B influence neuroblastoma tumor cell proliferation, EGFR degradation, and response to EGFR inhibition. These results suggest UBE4B-mediated growth factor receptor trafficking may contribute to the poor prognosis of patients who have neuroblastoma tumors with 1p36 deletions and that UBE4B expression may be a marker that can predict responses of neuroblastoma tumors to treatment.

Slow down to stay alive: HER4 protects against cellular stress and confers chemoresistance in neuroblastoma.

BACKGROUND: Neuroblastoma (NBL) is a common pediatric solid tumor, and outcomes for patients with advanced neuroblastoma remain poor despite extremely aggressive treatment. Chemotherapy resistance at relapse contributes heavily to treatment failure. The poor survival of patients with high-risk NBL prompted this investigation into novel treatment options with the objective of gaining a better understanding of resistance mechanisms. On the basis of previous work and on data from publicly available studies, the authors hypothesized that human epidermal growth factor receptor 4 (Her4) contributes to resistance. METHODS: Her4 expression was reduced with small-hairpin RNA (shRNA) to over express intracellular HER4, and the authors tested its impact on tumor cell survival under various culture conditions. The resulting changes in gene expression after HER4 knockdown were measured by using a messenger RNA (mRNA) array. RESULTS: HER4 expression was up-regulated in tumor spheres compared with the expression in monolayer culture. With HER4 knockdown, NBL cells became less resistant to anoikis and serum starvation. Moreover, HER4 knockdown increased the chemosensitivity of NBL cells to cisplatin, doxorubicin, etoposide, and activated ifosfamide. In mRNA array analysis, HER4 knockdown predominately altered genes related to cell cycle regulation. In NBL spheres compared with monolayers, cell proliferation was decreased, and cyclin D expression was reduced. HER4 knockdown reversed cyclin D suppression. Overexpressed intracellular HER4 slowed the cell cycle and induced chemoresistance. CONCLUSIONS: The current results indicated that HER4 protects NBL cells from multiple exogenous apoptotic stimuli, including anoikis, nutrient deficiency, and cytotoxic chemotherapy. The intracellular fragment of HER4 was sufficient to confer this phenotype. HER4 functions as a cell cycle suppressor, maintaining resistance to cellular stress. The current findings indicate that HER4 overexpression may be associated with refractory disease, and HER4 may be an important therapeutic target.

Signaling of ERBB receptor tyrosine kinases promotes neuroblastoma growth in vitro and in vivo.

BACKGROUND: ERBB receptor tyrosine kinases can mediate proliferation, migration, adhesion, differentiation, and survival in many types of cells and play critical roles in many malignancies. Recent reports suggest a role for EGFR signaling in proliferation and survival of neuroblastoma, a common form of pediatric cancer that often has an extremely poor outcome. METHODS: The authors examined ERBB family expression in neuroblastoma cell lines and patient samples by flow cytometry, western blot, and quantitative real time polymerase chain reaction (Q-PCR). Response to ERBB inhibition was assessed in vitro by cell-cycle analysis and western blot and in vivo by serial tumor-size measurements. RESULTS: A panel of neuroblastoma cell lines and primary patient tumors expressed EGFR, HER-3, and HER-4, with HER-2 in some tumors. HER-4 mRNA was expressed predominantly in cleavable isoforms. Whereas EGFR inhibition with erlotinib and pan-ERBB inhibition with CI-1033 inhibited EGF-induced phosphorylation of EGFR, AKT, and ERK1/2, only CI-1033 induced growth inhibition and dose-dependent apoptosis in vitro. Both CI-1033 and erlotinib treatment of neuroblastoma xenograft tumors resulted in decreased tumor growth in vivo, although CI-1033 was more effective. In vivo expression of EGFR was observed predominantly in vascular endothelial cells. CONCLUSIONS: Pan-ERBB inhibition is required for ERBB-related neuroblastoma apoptosis in vitro, although EGFR contributes indirectly to tumor growth in vivo. Inhibition of EGFR in endothelial cells may be an important aspect of erlotinib's impact on neuroblastoma growth in vivo. Our results suggest that non-EGFR ERBB family members contribute directly to neuroblastoma growth and survival, and pan-ERBB inhibition represents a potential therapeutic target for treating neuroblastoma.

Driven to death: Inhibition of farnesylation increases Ras activity and promotes growth arrest and cell death [corrected].

To improve cancer outcomes, investigators are turning increasingly to small molecule medicines that disrupt vital signaling cascades, inhibit malignant growth, or induce apoptosis. One vital signaling molecule is Ras, and a key step in Ras activation is membrane anchoring of Ras through prenylation, the C-terminal addition of a lipid anchor. Small molecule inhibitors of farnesyltransferase (FTI), the enzyme most often responsible for prenylating Ras, showed clinical promise, but development of FTIs such as tipifarnib has been stalled by uncertainty about their mechanism of action, because Ras seemed unimpeded in tipifarnib-treated samples. Interpretation was further complicated by the numerous proteins that may be farnesylated, as well as availability of an alternate prenylation pathway, geranylgeranylation. Our initial observations of varied response by cancer cell lines to tipifarnib led us to evaluate the role of FTI in Ras signal alteration using various tumor models. We describe our novel counterintuitive finding that endogenous Ras activity increases in cancer cell lines with low endogenous Ras activity when farnesyltransferase is inhibited by either tipifarnib or short hairpin RNA. In response to tipifarnib, variable growth arrest and/or cell death correlated with levels of activated extracellular signal­regulated kinase (ERK) and p38 mitogenactivated protein kinase (MAPK). Sensitivity to tipifarnib treatment was shown by growth inhibition and by an increase in subdiploid cell numbers; cells with such sensitivity had increased activation of ERK and p38 MAPK. Because Ras must be prenylated to be active, our findings suggest that geranylgeranylated N-Ras or K-Ras B interacts differently with downstream effector proteins in sensitive cancer cells responding to tipifarnib, switching the balance from cell proliferation to growth inhibition [corrected].

Critical signaling pathways in bone sarcoma: candidates for therapeutic interventions.

Bone sarcomas cause disproportionate morbidity and mortality and desperately need new therapies as there has been little improvement in outcomes in 20 years. Identification of critical signaling pathways, including type 1 insulin-like growth factor receptor (IGF-1R) for Ewing sarcoma and possibly osteosarcoma, and the ERBB and the Wnt signaling pathways for osteosarcoma, have emerged as receptors mediating vital signals for bone sarcoma. Akt, mammalian target of rapamycin (mTOR), phosphoinositide 3-kinases, mitogen-activated protein kinase kinase, extracellular signal-regulated kinases, and Ras pathway play key roles in at least some tumors, and inhibition of mTOR in particular will likely lead to improved survival, although clinical trials are still underway. The Notch pathway and ezrin are essential for osteosarcoma metastasis, and Fas downregulation is necessary for survival of metastases in lungs. As little is known about chondrosarcoma signaling, more preclinical work is needed. By defining vital signaling pathways in bone sarcomas, small molecule inhibitors can be applied rationally, leading to longer survival and reducing morbidity and late effects from intensive chemotherapy.

Strategies for the targeted delivery of therapeutics for osteosarcoma.

BACKGROUND: Conventional therapy for osteosarcoma has reached a plateau of 60 - 70%, a 5-year survival rate that has changed little in two decades, highlighting the need for new approaches. OBJECTIVE: To review the alternative means of delivering effective therapy for osteosarcoma that reach beyond the central venous catheter. METHODS: Drawing on the author's own experiences providing care to high-risk osteosarcoma patients and reviewing the last two decades of literature describing sarcoma therapy, available information is summarized about potential osteosarcoma treatments that deliver therapy by a less conventional route. RESULTS/CONCLUSIONS: Intra-arterial chemotherapy has a limited impact on survival, but may help to achieve a better limb salvage. Intrapleural chemotherapy is important for managing malignant effusions. The development of inhalation therapies, treatments that target new bone formation such as bisphosphonates, chemically targeted radiation and antibody-based therapies all have potential to improve osteosarcoma therapy.

Novel agents in development for pediatric sarcomas.

PURPOSE OF REVIEW: The survival curves for many pediatric sarcomas have remained flat for the past 2 decades or more and novel therapeutics - those small molecule medicines that selectively inhibit specific signaling molecules - have been slow to enter into pediatric practice. The preclinical basis for their use is reviewed here. RECENT FINDINGS: Preclinical and phase I studies showing efficacy of antiinsulin-like growth factor receptor 1 therapies for Ewing sarcoma have led to numerous ongoing clinical trials using these agents for Ewing and other sarcomas. Early studies of ERBB signaling as a target in sarcoma therapy have been tantalizing, but progress in this area has been controversial. In-vitro analysis of Src inhibitors suggested that these agents would prevent metastasis in osteosarcoma, whereas in-vivo analysis showed no effect on metastasis, underscoring the need for thorough preclinical investigations of promising new therapies to guide future clinical trials. Antiangiogenic and immunomodulatory therapies are gaining momentum in the pediatric arena and should be tested in combination with traditional cytotoxic agents for recurrent and high-risk primary pediatric sarcomas. SUMMARY: Pediatric sarcomas have diverse biology and distinct signaling pathways, making detailed preclinical evaluation of small molecule inhibitors essential to guiding the design of further clinical investigations.

Cetuximab attenuates metastasis and u-PAR expression in non-small cell lung cancer: u-PAR and E-cadherin are novel biomarkers of cetuximab sensitivity.

Cetuximab, which blocks ligand binding to epidermal growth factor receptor (EGFR), is currently being studied as a novel treatment for non-small cell lung cancer (NSCLC). However, its mechanisms of action toward metastasis, and markers of drug sensitivity, have not been fully elucidated. This study was conducted to (a) determine the effect of Cetuximab on invasion and NSCLC-metastasis; (b) investigate urokinase-type plasminogen activator receptor (u-PAR), a major molecule promoting invasion and metastasis, as a target molecule; (c) delineate molecular mediators of Cetuximab-induced metastasis inhibition; and (d) identify biomarkers of drug sensitivity in NSCLC. Cetuximab treatment resulted in reduced growth and Matrigel invasion of H1395 and A549 NSCLC cell lines, in parallel with reduced u-PAR mRNA and protein. u-PAR down-regulation was brought about by suppressing the binding of JunD and c-Jun to u-PAR promoter motif -190/-171 in vivo, and an inhibition of MAP/ERK kinase signaling. Furthermore, Cetuximab inhibited NSCLC proliferation and metastasis to distant organs in vivo as indicated by the chicken embryo metastasis assay. Low E-cadherin and high u-PAR, but not EGFR, was associated with resistance to Cetuximab in seven NSCLC cell lines. Furthermore, siRNA knockdown of u-PAR led to a resensitization to Cetuximab. Moreover, low E-cadherin and high u-PAR was found in 63% of resected tumor tissues of NSCLC patients progressing under Cetuximab therapy. This is the first study to show u-PAR as a target and marker of sensitivity to Cetuximab, and to delineate novel mechanisms leading to metastasis suppression of NSCLC by Cetuximab.

How the NOTCH pathway contributes to the ability of osteosarcoma cells to metastasize.

Controlling metastasis is the key to improving outcomes for osteosarcoma patients; yet our knowledge of the mechanisms regulating the metastatic process is incomplete. Clearly Fas and Ezrin are important, but other genes must play a role in promoting tumor spread. Early developmental pathways are often recapitulated in malignant tissues, and these genes are likely to be important in regulating the primitive behaviors of tumor cells, including invasion and metastasis. The Notch pathway is a highly conserved regulatory signaling network involved in many developmental processes and several cancers, at times serving as an oncogene and at others, behaving as a tumor suppressor. In normal limb development, Notch signaling maintains the apical ectodermal ridge in the developing limb bud and regulated size of bone and muscles. Here, we examine the role of Notch signaling in promoting metastasis of osteosarcoma, and the underlying regulatory processes that control Notch pathway expression and activity in the disease. We have shown that, compared to normal human osteoblasts and non-metastatic osteosarcoma cell lines, osteosarcoma cell lines with the ability to metastasize have higher levels of Notch 1, Notch 2, the Notch ligand DLL1 and the Notch-induced gene Hes1. When invasive osteosarcoma cells are treated with small molecule inhibitors of gamma-secretase, which blocks Notch activation, invasiveness is abrogated. Direct retroviral expression has shown that Hes1 expression was necessary for osteosarcoma invasiveness and accounted for the observations. In a novel orthotopic murine xenograft model of osteosarcoma pulmonary metastasis, blockade of Hes1 expression and Notch signaling eliminated spread of disease from the tibial primary tumor. In a sample of archival human osteosarcoma tumor specimens, expression of Hes1 mRNA was inversely correlated with survival (n=16 samples, p=0.04). Expression of the microRNA 34 cluster, which is known to downregulate DLL1, Notch 1 and Notch 2, was inversely correlated with invasiveness in a small panel of osteosarcoma tumors, suggesting that this family of microRNAs may be responsible for regulating Notch expression in at least some tumors. Further, exposure to valproic acid at therapeutic concentrations induced expression of Notch genes and caused a 250-fold increase in invasiveness for non-invasive cell lines, but had no discernible effect on those lines that expressed high levels of Notch without valproic acid treatment, suggesting a role for HDAC in regulating Notch pathway expression in osteosarcoma. These findings show that the Notch pathway is important in regulating osteosarcoma metastasis and may be useful as a therapeutic target. Better understanding of Notch's role and its regulation will be essential in planning therapies with other agents, especially the use of valproic acid and other HDAC inhibitors.

Critical role of notch signaling in osteosarcoma invasion and metastasis.

PURPOSE: Notch signaling is an important mediator of growth and survival in several cancer types, with Notch pathway genes functioning as oncogenes or tumor suppressors in different cancers. However, the role of Notch in osteosarcoma is unknown. EXPERIMENTAL DESIGN: We assessed the expression of Notch pathway genes in human osteosarcoma cell lines and patient samples. We then used pharmacologic and retroviral manipulation of the Notch pathway and studied the effect on osteosarcoma cell proliferation, survival, anchorage-independent growth, invasion, and metastasis in vitro and in vivo. RESULTS: Notch pathway genes, including Notch ligand DLL1, Notch1 and Notch2, and the Notch target gene HES1, were expressed in osteosarcoma cells, and expression of HES1 was associated with invasive and metastatic potential. Blockade of Notch pathway signaling with a small molecule inhibitor of gamma secretase eliminated invasion in Matrigel without affecting cell proliferation, survival, or anchorage-independent growth. Manipulation of Notch and HES1 signaling showed a crucial role for HES1 in osteosarcoma invasiveness and metastasis in vivo. CONCLUSION: These studies identify a new invasion and metastasis-regulating pathway in osteosarcoma and define a novel function for the Notch pathway: regulation of metastasis. Because the Notch pathway can be inhibited pharmacologically, these findings point toward possible new treatments to reduce invasion and metastasis in osteosarcoma.

Primary tuberculosis of bone mimicking a lytic bone tumor.

Causes of lytic bone lesions in children include benign, malignant, and infectious processes. Here, we present the case of a 3-year-old boy presenting with a lytic bone lesion and surrounding soft tissue mass sent for evaluation of possible malignancy versus osteomyelitis. Biopsy revealed granulomatous osteomyelitis, and subsequent purified protein derivative resulted in 20-mm induration. Lesion cultures eventually identified pan-sensitive Mycobacterium tuberculosis. We emphasize that tuberculosis can cause primary lytic bone lesions in children in the United States, even in the absence of pulmonary symptoms or known exposure, and advise clinicians to include mycobacterial cultures when analyzing biopsies of lytic bone lesions.

Ex vivo culture with interleukin (IL)-12 improves CD8(+) T-cell adoptive immunotherapy for murine leukemia independent of IL-18 or IFN-gamma but requires perforin.

In animal models and clinical trials, adoptive transfer of activated, antigen-specific CD8(+) T cells mediates tumor regression in a cell dose-dependent manner. The cytokine interleukin (IL)-12 promotes CD8(+) T-cell cytotoxicity and, with IL-18, synergistically up-regulates IFN-gamma release. We have shown that culturing CD8(+) T cells ex vivo with IL-12 and IL-18 enhanced antitumor responses in vivo and in vitro using a model of C1498/ovalbumin, a murine acute myeloid leukemia cell line expressing the antigen ovalbumin. Activated ovalbumin-specific CD8(+) T cells cultured with IL-12, IL-18, both, or neither were assayed for antigen-specific cytokine production and cytolytic activity and adoptively transferred to C57BL/6 mice with established tumors. Maximal IFN-gamma release occurred after T-cell culture with IL-12 and IL-18. Tumor-specific in vitro cytotoxicity was enhanced by IL-12, unaffected by addition of IL-18, and abrogated in perforin-deficient T cells irrespective of cytokine exposure. T cells cultured with IL-12 more effectively eliminated tumors, and addition of IL-18 did not further augment responses. IFN-gamma-deficient CD8(+) T cells showed effective antitumor activity that was enhanced by IL-12 with or without IL-18. Perforin-deficient CD8(+) T cells were poor mediators of antitumor activity, though, and showed no improvement after culture with IL-12 and/or IL-18. Thus, ex vivo culture with IL-12 was sufficient to augment antigen-specific in vitro cytotoxicity and antitumor activity in vivo in an IFN-gamma-independent but perforin-dependent manner. Ex vivo culture with IL-12 may improve CD8(+) T-cell immunotherapy of cancer in the absence of donor cell-derived IFN-gamma via perforin-mediated cytolysis.