Targeting angiogenesis in childhood sarcomas

BET Epigenetic Reader Proteins in Cardiovascular Transcriptional Programs

Epigenetic mechanisms involve the placing (writing) or removal (erasing) of histone modifications that allow heterochromatin to transition to the open, activated euchromatin state necessary for transcription. A third, less studied epigenetic pathway involves the reading of these specific histone marks once placed. The BETs (bromodomain and extraterminal-containing protein family), which includes BRD2, BRD3, and BRD4 and the testis-restricted BRDT, are epigenetic reader proteins that bind to specific acetylated lysine residues on histone tails where they facilitate the assembly of transcription complexes including transcription factors and transcriptional machinery like RNA Polymerase II. As reviewed here, considerable recent data establishes BETs as novel determinants of induced transcriptional programs in vascular cells, like endothelial cells and vascular smooth muscle cells, cardiac myocytes and inflammatory cells, like monocyte/macrophages, cellular settings where these epigenetic reader proteins couple proximal stimuli to chromatin, acting at super-enhancer regulatory regions to direct gene expression. BET inhibition, including the use of specific chemical BET inhibitors like JQ-1, has many reported effects in vivo in the cardiovascular setting, like decreasing atherosclerosis, angiogenesis, intimal hyperplasia, pulmonary arterial hypertension, and cardiac hypertrophy. At the same time, data in endothelial cells, adipocytes, and elsewhere suggest BETs also help regulate gene expression under basal conditions. Studies in the cardiovascular setting have highlighted BET action as a means of controlling gene expression in differentiation, cell identity, and cell state transitions, whether physiological or pathological, adaptive, or maladaptive. While distinct BET inhibitors are being pursued as therapies in oncology, a large prospective clinical cardiovascular outcome study investigating the BET inhibitor RVX-208 (now called apabetalone) has already been completed. Independent of this specific agent and this one trial or the numerous unanswered questions that remain, BETs have emerged as novel epigenetic players involved in the execution of coordinated transcriptional programs in cardiovascular health and disease.

Degradation of endothelial network in disordered tumor-containing cell sheet

Tumor angiogenesis is an important event in tumor malignancy; and the vasculature formed in tumor region is typically dysfunctional. Multiple factors are associated with tumor vessel abnormalities, but the precise mechanism has not been fully understood. In the present study, a tumor-containing cell sheet was prepared by mixing a small population of human embryonal rhabdomyosarcoma (RMS) cells (RDs) with human skeletal muscle myoblasts (HSMMs) to mimic muscle tissue invaded by RMS cells. Sheet fluidity and the extracellular matrix (ECM) meshwork of the tumor-containing cell sheet were found to be elevated and disordered, demonstrating the disruptive effect of tumor cells on sheet structure. When green fluorescent protein expressing human umbilical vein endothelial cells (GFP-HUVECs) were co-cultured with the tumor-containing cell sheet, an endothelial network was formed, but degraded faster as a result of activated migration of endothelial cells in the tumor-containing cell sheet. This study suggested that disorganized tissue structure facilitate tumor angiogenesis by activation of endothelial cell migration.

Pediatric Osteosarcoma: An Updated Review

Osteosarcoma (OS), the most common type of primary malignant bone tumor, is defined by the presence of malignant mesenchymal cells producing osteoid or immature bone. The peak incidence of the most frequent type of OS, i.e., high-grade central OS, occurs in the second decade of life during the adolescent growth spurt. Most patients suffer from the pain and swelling in the involved region and, usually, seek medical attention. Diagnosis is carried out by conventional radiographs, computed tomography, and magnetic resonance image (MRI). In addition, three-phase bone scans, thallium scintigraphy, dynamic MRI, and positron emission spectroscopy are new innovative promising tools. OS can be treated with surgery, radiotherapy, and chemotherapy. There is a clear need for newer effective agents for patients with OS, especially for patients who afflicted with metastatic and recurrence tumor. Monoclonal antibodies directed against OS may prove useful as treatment, either for drug delivery or for radiopharmaceuticals.

Optimal management of Ewing sarcoma family of tumors: recent developments in systemic therapy

The Ewing sarcoma family of tumors (ESFT) is defined by cell surface expression of CD99 and a translocation involving EWS and an ETS partner. Cytotoxic chemotherapy remains the benchmark of first- and second-line therapy, and although the majority of patients with localized disease are cured, almost one third of patients relapse or progress from their disease. Moreover, cure remains elusive in most patients who present with distant metastases. In recent years, the ESFT literature has been dominated by reports of attempts at modulating the insulin-like growth factor (IGF) receptor (IGFR). Unfortunately, three phase II studies examining inhibiting antibodies to IGFR-1 published disappointing results. Whether these results were due to failure to modulate the pathway or other limitations in study design and/or patient selection remain unclear. Other novel strategies currently being investigated in ESFT include tyrosine kinase, mammalian target of rapamycin (mTOR), and poly(ADP-ribose) polymerase (PARP) inhibitors.

Luteinizing hormone, sex steroids and extracorporeal circulation - a promising link to treat retroperitoneal sarcomas. A reconsideration of cancer treatment

Retroperitoneal sarcomas are rare and aggressive tumors with a negative prognosis as there is currently no satisfactory treatment for them. The only proven factor that can significantly increase the otherwise poor survival of sarcoma patients is the radically of resection. However, the completeness of resection is hindered by the hypervascularized nature of sarcomas and the frequent involvement of major blood vessels. In this context, we propose to operate on retroperitoneal sarcomas only with the use of extracorporeal circulation, applying vascular clamps above and below the tumor, even with short periods of hypothermic circulatory arrest in complex cases. This technique would allow the surgeon to achieve complete tumor resections, approach large blood vessels easier and perform sofisticated vascular reconstructions with no fear of hemorrhage which is fundamental to achieve a bloodless surgical field. Also, we speculate on the etiology of retroperitoneal sarcomas that appear mostly during the period of menopause/andropause. Although both estrogens and androgens have been incriminated in inducing various cancer types, including sarcomas, an endogenous estradiol cathabolyte has been shown to have anti-tumor effects. Considering that during menopause/andropause sex steroid levels actually decrease, our second working hypothesis is that the increasing follicle-stimulating hormone (FSH) and especially luteinizing hormone (LH) levels, together with the relative estrogen/androgen imbalance, may be the triggering cause. Also, a certain level of estrogens (Methoxyestradiol) may be essential in limiting tumor development and dedifferentiation. Given that extragonadal sarcomas appear to behave as endocrine tumors, a targeted hormonal therapy, together with controlled radical resections in complex cases of tumor vascular involvement, would certainly provide a strong link to both prevention and treatment of retroperitoneal sarcomas and even of cancer in general.

Childhood rhabdomyosarcoma: recent advances and prospective views

Rhabdomyosarcoma (RMS) is a morphologically and clinically heterogeneous group of malignant tumors that resemble developing skeletal muscle and is the most common soft-tissue sarcoma in children and adolescents. The most prominent sites involve head and neck structures (~40%), genito-urinary track (~25%), and extremities (~20%). Embryonal (ERMS) and alveolar (ARMS) are the two major RMS subtypes that are distinct in their morphology and genetic make-up. The prognosis for this cancer depends strongly on tumor size, location, staging, and child's age. In general, ERMS has a more favorable outcome, whereas the mortality rate remains high in patients with ARMS, because of its aggressive and metastatic nature. Over the past two decades, researchers have made concerted efforts to delineate genetic and epigenetic changes associated with RMS pathogenesis. These molecular signatures have presented golden opportunities to design targeted therapies for treating this aggressive cancer. This article highlights recent advances in understanding the molecular pathogenesis of RMS, and addresses promising research areas for further exploration.