Rhabdomyosarcoma in children

Pancreatic masses in children: a single-center experience over two decades

Pancreatic masses are extremely rare in pediatric patients, with limited data available. This lack of data makes the diagnosis and management of these tumors in children extremely challenging. Therefore, we aimed to describe the presentations, clinical course, and outcomes of children with pancreatic tumors at our center. A retrospective analysis was performed of all pediatric patients diagnosed with pancreatic masses between 2003 and 2022 in an academic freestanding children's hospital. Data including demographics, clinical presentation, workup, management, and subsequent morbidity and mortality were collected and aggregated. Furthermore, we reviewed cases of pancreatic tumor resections in the National Surgical Quality Improvement Program - Pediatric (NSQIP-P) database to identify common adverse outcomes and measures for quality improvement. In total, 17 patients were identified at our institution. Diagnoses included solid pseudopapillary (n = 9), gastrinoma (n = 1), rhabdomyosarcoma (n = 2), pancreatoblastoma (n = 2), and insulinoma (n = 1). Two patients did not have a histopathologic diagnosis and were excluded from subsequent analysis. Overall, 12 patients underwent surgical intervention, with the most common procedures being pancreaticoduodenectomy and distal pancreatectomy, and all 12 were known to be alive at last contact. There were 3 deaths, all due to complications related to metastatic disease. Furthermore, 30-day postoperative outcomes in the NSQIP-P dataset for pancreatic surgeries in pediatric patients are excellent, with negligible morbidity and no mortalities after the index surgery.

CONCLUSIONS

Children with pancreatic tumors amenable to surgical resection appear to have adequate long-term survival. Short-term outcomes at diagnosis are excellent and mainly appear to be influenced by the presence of metastatic disease at initial presentation.

WHAT IS KNOWN

• Pancreatic masses are a rare entity in children with limited data on their presentation, management and surgical outcomes. • Solid Pseudopapillary tumors are one of the most common pancreatic tumors in children with a fair prognosis after surgical intervention.

WHAT IS NEW

• Surgical management of pediatric patients with pancreatic tumors is safe and effective in patients who do not have aggressive tumor types or metastatic disease. • Our case series provides a notable cohort of these pancreatic tumors with insight into the presentation, management and outcomes of five of these tumor types.

Exceptional case of a hemangioma-like rabdomyosarcoma in the hand's palm

Rhabdomyosarcoma is a malignant tumor in children that might mimic a benign tumor, such as infantile hemangioma, particularly when detected early. Although rhabdomyosarcoma rarely occurs in the hand, its prognosis is generally poor, and successful treatment relies on a complete and radical surgical excision. We present a case of rhabdomyosarcoma located in the palm of an infant's hand, initially presenting clinical and radiological features suggestive of a vascular tumor. The resection of this mass was radical, and histological analysis and immunohistochemistry returned in favor of embryonic rhabdomyosarcoma. In similar cases recorded in the literature, the diagnosis may be first mistaken for that of a hemangioma, then confirmed by histology. This underlines the importance of a systematic anatomopathological examination of all tissues removed surgically.

Case Report: Robotic pylorus-preserving pancreatoduodenectomy for periampullary rhabdomyosarcoma in a 3-year-old patient

Periampullary neoplasm is rare in pediatric patients and has constituted a strict indication for pancreatoduodenectomy (PD), which is a procedure sporadically reported in the literature among children. Robotic PD has been routinely performed for periampullary neoplasm in periampullary neoplasm, but only a few cases in pediatric patients have been reported. Here, we report the case of a 3-year-old patient with periampullary rhabdomyosarcoma treated with robotic pylorus-preserving PD and share our experience with this procedure in pediatric patients. A 3-year-old patient presented with obstructive jaundice and a mass in the pancreatic head revealed by imaging. A laparoscopic biopsy was performed. Jaundice progressed with abdominal pain and elevated alpha-amylase leading to urgent robotic exploration in which a periampullary neoplasm was revealed and pathologically diagnosed as rhabdomyosarcoma by frozen section examination. After pylorus-preserving PD, we performed a conventional jejunal loop following a child reconstruction, including an end-to-end pancreaticojejunostomy, followed by end-to-side hepaticojejunostomy and duodenojejunostomy. Delayed gastric emptying (DGE) presented with increasing drain from the nasogastric tube (NGT) a week after the surgery and improved spontaneously within 10 days. In a 13-month follow-up until the present, our case patient recovered well without potentially fatal complications, such as pancreatic fistula. Robotic PD in pediatric patients was safe and effective without intra- or postoperative complications.

Alveolar Rhabdomyosarcoma of the Temporal Region with Metastatic Cervical Lymph Node

Introduction: Paediatric rhabdomyosarcoma most commonly occurs in the head and neck region. Its treatment is complex, including multi-drug chemotherapy, surgery and radiotherapy. Case report: Here, we report a case of alveolar rhabdomyosarcoma of the temporal region with a metastatic cervical lymph node, in a 15-year-old girl, and its management. The patient received ne-adjuvant chemotherapy, followed by surgery and post operative radiotherapy. Literature was also reviewed for the various treatment modalities for these rare tumours. Discussion: Rhabdomyosarcoma of the temporal region has rarely been reported in the literature. Due to the rarity of these tumours, there are difficulties in creating standardized therapeutic protocols. However, multimodality treatment, including chemotherapy, surgery and radiotherapy, has been shown to improve the overall survival rate.

Nefarious NTRK oncogenic fusions in pediatric sarcomas: Too many to Trk

Neurotrophic Tyrosine Receptor Kinase (NTRK) genes undergo chromosomal translocations to create novel open reading frames coding for oncogenic fusion proteins; the N-terminal portion, donated by various partner genes, becomes fused to the tyrosine kinase domain of either NTRK1, NTRK2, or NTRK3. NTRK fusion proteins have been identified as driver oncogenes in a wide variety of tumors over the past three decades, including Pediatric Gliomas, Papillary Thyroid Carcinoma, Spitzoid Neoplasms, Glioblastoma, and additional tumors. Importantly, NTRK fusions function as drivers of pediatric sarcomas, accounting for approximately 15% of childhood cancers including Infantile Fibrosarcoma (IFS), a subset of pediatric soft tissue sarcoma (STS). While tyrosine kinase inhibitors (TKIs), such as larotrectinib and entrectinib, have demonstrated profound results against NTRK fusion-positive cancers, acquired resistance to these TKIs has resulted in the formation of gatekeeper, solvent-front, and compound mutations. We present a comprehensive compilation of oncogenic fusions involving NTRKs focusing specifically on pediatric STS, examining their biological signaling pathways and mechanisms of activation. The importance of an obligatory dimerization or multimerization domain, invariably donated by the N-terminal fusion partner, is discussed using characteristic fusions that occur in pediatric sarcomas. In addition, examples are presented of oncogenic fusion proteins in which the N-terminal partners may contribute additional biological activities beyond an oligomerization domain. Lastly, therapeutic approaches to the treatment of pediatric sarcoma will be presented, using first generation and second-generation agents such as selitrectinib and repotrectinib.

Anticancer bioactivity of zerumbone on pediatric rhabdomyosarcoma cells

PURPOSE

Natural products are generally regarded as safe and have been shown to mediate anticancer activities against a variety of cell types. Zerumbone is a natural cyclic sesquiterpene derived from the rhizome of Zingiber zerumbet, which has attracted extensive attention in the recent decade for anticancer activities. The present study investigates the in vitro effect of zerumbone on rhabdomyosarcoma cells.

METHODS

Two rhabdomyosarcoma cell lines (RD and RH30) were used as the model system. The growth inhibition of zerumbone was measured by MTT-assay, apoptosis via flow cytometry, gene expression by real-time PCR, the migration by transwell assay, and intracellular signaling by Western blotting.

RESULTS

Zerumbone shows anticancer effects on RD and RH30 cells in a dose-dependent manner via cell growth inhibition and induction of apoptosis. Exposure of RD and RH30 cells on zerumbone also resulted in a decrease of migration and downregulation of the hedgehog pathway.

CONCLUSIONS

Taken together, our study provided the first evidence that zerumbone imparted strong inhibitory and apoptotic effects on pediatric rhabdomyosarcoma cell lines and merit further investigation as a promising candidate for the anticancer therapy.

Looking at denitrosylation to understand the myogenesis gone awry theory of rhabdomyosarcoma

S-nitrosylation of proteins is a nitric oxide (NO)-based post-translational modification of cysteine residues. By removing the NO moiety from S-nitrosothiol adducts, denitrosylases restore sulfhydryl protein pool and act as downstream tuners of S-nitrosylation signaling. Alterations in the S-nitrosylation/denitrosylation dynamics are implicated in many pathological states, including cancer ontogenesis and progression, skeletal muscle myogenesis and function. Here, we aim to provide and link different lines of evidence, and elaborate on the possible role of S-nitrosylation/denitrosylation signaling in rhabdomyosarcoma, one of the most common pediatric mesenchymal malignancy.

Contrast-enhanced ultrasound of the spleen, pancreas and gallbladder in children

Gray-scale and color/power Doppler ultrasound (US) are the first-line imaging modalities to evaluate the spleen, gallbladder and pancreas in children. The increasing use of contrast-enhanced ultrasound (CEUS) as a reliable and safe method to evaluate liver lesions in the pediatric population promises potential for imaging other internal organs. Although CEUS applications of the spleen, gallbladder and pancreas have been well described in adults, they have not been fully explored in children. In this manuscript, we present an overview of the applications of CEUS for normal variants and diseases affecting the spleen, gallbladder and pancreas. We highlight a variety of cases as examples of how CEUS can serve in the diagnosis and follow-up for such diseases in children. Our discussion includes specific examination techniques; presentation of the main imaging findings in various benign and malignant lesions of the spleen, gallbladder and pancreas in children; and acknowledgment of the limitations of CEUS for these organs.

Inhibition of lipid metabolism exerts antitumor effects on rhabdomyosarcoma

Rhabdomyosarcoma exhibits tumor-specific energy metabolic changes that include the Warburg effect. Since targeting cancer metabolism is a promising therapeutic approach, we examined the antitumor effects of suppressing lipid metabolism in rhabdomyosarcoma. We suppressed lipid metabolism in rhabdomyosarcoma cells in vitro by administering an inhibitor of malonyl-CoA decarboxylase, which increases malonyl-CoA and decreases fatty acid oxidation. Suppression of lipid metabolism in rhabdomyosarcoma cells decreased cell proliferation by inducing cell cycle arrest. Metabolomic analysis showed an increase in glycolysis and inactivation of the pentose phosphate pathway. Immunoblotting analysis revealed upregulated expression of the autophagy marker LC3A/B-II due to increased phosphorylation of AMP-activated protein kinase, a nutrient sensor. p21 protein expression level also increased. Inhibition of both lipid metabolism and autophagy suppressed tumor proliferation and increased apoptosis. In vivo studies involved injection of human Rh30 cells into the gastrocnemius muscle of 6-week-old female nude mice, which were divided into normal chow and low-fat diet groups. The mice fed a low-fat diet for 21 days showed reduced tumor growth compared to normal chow diet-fed mice. Suppression of lipid metabolism disrupted the equilibrium of the cancer-specific metabolism in rhabdomyosarcoma, resulting in a tumor growth-inhibition effect. Therefore, the development of treatments focusing on the lipid dependence of rhabdomyosarcoma is highly promising.

What to Look Out for in a Newborn with Multiple Papulonodular Skin Lesions at Birth

Multiple papulonodular skin lesions at birth can indicate the presence of various benign and malignant disorders. Although the lesions’ clinical aspect (color and consistency, in particular) may steer the clinician towards one disorder or another (infantile myofibromatosis, xanthogranuloma, or metastatic neuroblastoma), the diagnosis can only be confirmed by the histopathologic assessment of a biopsy. In neonates, a rapid but accurate diagnosis is critical because skin lesions may be the first manifestation of a malignant disorder like leukemia cutis or metastatic neuroblastoma. Here, we review the various disorders that may manifest themselves as multiple skin lesions at birth.

GEIS-SEHOP clinical practice guidelines for the treatment of rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma (STS) in children and adolescents. In Spain the annual incidence is 4.4 cases per million children < 14 years. It is an uncommon neoplasm in adults, but 40% of RMS are diagnosed in patients over 20 years of age, representing 1% of all STS in this age group. RMS can appear anywhere in the body, with some sites more frequently affected including head and neck, genitourinary system and limbs. Assessment of a patient with suspicion of RMS includes imaging studies (MRI, CT, PET-CT) and biopsy. All patients with RMS should receive chemotherapy, either at diagnosis in advanced or metastatic stages, or after initial resection in early local stages. Local control includes surgery and/or radiotherapy depending on site, stage, histology and response to chemotherapy. This guide provides recommendations for diagnosis, staging and treatment of this neoplasm.

Cytologic diagnosis of metastatic embryonal rhabdomyosarcoma in cerebrospinal fluid: A case report

Rhabdomyosarcoma (RMS) originates from a differentiation block in muscle progenitors. Leptomeningeal metastasis is a rare but devastating complication of RMS which can be caused by dissemination of cancer cells in cerebrospinal fluid (CSF). Here, we present a 4-year-old female with RMS originating from the upper nasal wall. The following histologic and immunohistochemistry analyses combined with molecular testing analysis supported the diagnosis of embryonal rhabdomyosarcoma (ERMS). Results from CSF routine test, magnetic resonance imaging scans and CSF cytology indicated metastatic meningitis, thus confirming the diagnosis of metastatic ERMS in CSF. This is the first report to describe the clinical features of ERMS in CSF.

3D monitoring of tumor volume in an in vivo model

BACKGROUND

The ability to evaluate tumor development within experimental oncology is of upmost importance. However, determining tumor volumes in 3D in vivo tumor models is challenging. The chick chorioallantoic membrane (CAM) model represents an optimized xenograft model that surpasses many disadvantages that are inherent to rodent models and provides the opportunity of real-time monitoring of tumor growth.

OBJECTIVE

The objective of this study was to introduce a new method that enables monitoring of tumor growth within the CAM model throughout the course of the experiment.

METHODS

Sarcoma cell lines and sarcoma primary tumors were grafted onto the CAM of fertilized chicken eggs. A digital microscope (Keyence VHX-6000) was used for 3D volume monitoring before and after tumor excision and compared it to tumor weight.

RESULTS

Accuracy of tumor volumes was validated through correlation with tumor weight. In and ex ovo tumor volumes correlated significantly with tumor weight values.

CONCLUSIONS

The described method can be used to assess the effects of chemotherapeutic agents on the growth of tumors that have been grafted onto the CAM and further advance personalized cancer therapy. In summary, we established a promising protocol that enables in vivo real-time tracking of tumor growth in the CAM model using a digital microscope.

Co-inhibition of BET proteins and PI3Kα triggers mitochondrial apoptosis in rhabdomyosarcoma cells

Remodeling transcription by targeting bromodomain and extraterminal (BET) proteins has emerged as promising anticancer strategy. Here, we identify a novel synergistic interaction of the BET inhibitor JQ1 with the PI3Kα-specific inhibitor BYL719 to trigger mitochondrial apoptosis and to suppress tumor growth in models of rhabdomyosarcoma (RMS). RNA-Seq revealed that JQ1/BYL719 co-treatment shifts the overall balance of BCL-2 family gene expression towards apoptosis and upregulates expression of BMF, BCL2L11 (BIM), and PMAIP1 (NOXA) while downregulating BCL2L1 (BCL-xL). These changes were confirmed by qRT-PCR and western blot analysis. Ingenuity pathway analysis (IPA) of RNA-Seq data followed by validation qRT-PCR and western blot identified MYC and FOXO3a as potential transcription factors (TFs) upstream of the observed gene expression pattern. Immunoprecipitation (IP) studies showed that JQ1/BYL719-stimulated increase in BIM expression enhances the neutralization of antiapoptotic BCL-2, BCL-xL, and MCL-1. This promotes the activation of BAK and BAX and caspase-dependent apoptosis, as (1) individual silencing of BMF, BIM, NOXA, BAK, or BAX, (2) overexpression of BCL-2 or MCL-1 or (3) the caspase inhibitor N-Benzyloxycarbonyl-Val-Ala-Asp(O-Me) fluoromethylketone (zVAD.fmk) all rescue JQ1/BYL719-induced cell death. In conclusion, co-inhibition of BET proteins and PI3Kα cooperatively induces mitochondrial apoptosis by proapoptotic re-balancing of BCL-2 family proteins. This discovery opens exciting perspectives for therapeutic exploitation of BET inhibitors in RMS.

PET in the Diagnostic Management of Soft Tissue Sarcomas of Musculoskeletal Origin

Soft tissue sarcomas (STSs) account for less than 1% of adult solid tumors and about 7% of pediatric malignancies, causing 2% of cancer-related deaths. With the advent of PET-computed tomography (CT), the value of (18) fluorine-2-fluoro-2-deoxy-d-glucose (FDG) PET imaging to improve the management of STSs has been explored. FDG PET imaging has been found useful in restaging and treatment response assessment. This article reviews current knowledge and application of FDG PET-CT in initial diagnosis, staging, restaging, treatment response monitoring, and prognosis, with a brief overview of the most common histologic subtypes of STS.

Co-targeting of BET proteins and HDACs as a novel approach to trigger apoptosis in rhabdomyosarcoma cells

Histone acetylation marks exert essential functions in regulating gene expression. These marks are written by histone acetyltransferases (HATs), removed by histone deacetylases (HDACs) and read by e.g. BET proteins. While BET inhibitors are promising new anticancer drugs, little is yet known about their antitumor activity in rhabdomyosarcoma (RMS). We therefore investigated the efficacy of the prototypic BET inhibitor JQ1 alone or in combination with other epigenetic modifiers, namely HDAC inhibitors (HDACIs). Here, we discover a synergistic interaction of the panBET inhibitor JQ1 together with various HDACIs, i.e. Quisinostat (JNJ-26481585), Vorinostat (SAHA), Entinostat (MS-275) and Panobinostat (LBH589), inducing apoptosis in RMS cells, whereas JQ1 as single agent exhibits little cytotoxicity. Calculation of combination index (CI) confirmed the synergism of this combination. Importantly, JQ1 and JNJ-26481585 act in concert to suppress colony formation and to trigger apoptosis in an in vivo model. Mechanistic studies revealed that combination of JQ1 and JNJ-26481585 cooperatively upregulates BIM and BMF, while downregulating BCL-x_L. This shifted ratio of pro- and antiapoptotic BCL-2 proteins engages activation of BAX and BAK and increases caspases-3 and -7 activity. Individual silencing of BIM or NOXA, overexpression of BCL-2 or MCL-1 as well as addition of the caspase inhibitor zVAD.fmk significantly rescue JQ1/JNJ-26481585-induced apoptosis. Thus, co-targeting of histone acetylation by concomitant inhibition of HDAC and BET proteins synergistically induces mitochondrial apoptosis by shifting the ratio of pro- and antiapoptotic BCL-2 proteins towards apoptosis. These findings indicate that combinatorial use of BET and HDACIs may represent a promising new strategy for the treatment of RMS.

Targeting redox homeostasis in rhabdomyosarcoma cells: GSH-depleting agents enhance auranofin-induced cell death

Rhabdomyosarcoma (RMS) cells have recently been reported to be sensitive to oxidative stress. Therefore, we investigated whether concomitant inhibition of the two main antioxidant defense pathways, that is, the thioredoxin (TRX) and the glutathione (GSH) systems, presents a new strategy to trigger cell death in RMS. In this study, we discover that GSH-depleting agents, i.e. γ-glutamylcysteine synthetase inhibitor, buthionine sulfoximine (BSO) or the cystine/glutamate antiporter inhibitor erastin (ERA), synergize with thioredoxin reductase (TrxR) inhibitor auranofin (AUR) to induce cell death in RMS cells. Interestingly, AUR causes accumulation of ubiquitinated proteins when combined with BSO or ERA, in line with recent reports showing that AUR inhibits the proteasome besides TrxR. Consistently, AUR/BSO or AUR/ERA cotreatment increases ubiquitination and expression of the short-lived proteins NOXA and MCL-1, accompanied by increased binding of NOXA to MCL-1. Notably, NOXA knockdown significantly rescues RMS cells from AUR/BSO- or AUR/ERA-induced cell death. In addition, AUR acts together with BSO or ERA to stimulate BAX/BAK and caspase activation. Of note, BSO or ERA abolish the AUR-stimulated increase in GSH levels, leading to reduced GSH levels upon cotreatment. Although AUR/BSO or AUR/ERA cotreatment enhances reactive oxygen species (ROS) production, only thiol-containing antioxidants (i.e., N-acetylcysteine (NAC), GSH), but not the non-thiol-containing ROS scavenger α-Tocopherol consistently suppress AUR/BSO- and AUR/ERA-stimulated cell death in both cell lines. Importantly, re-supply of GSH or its precursor NAC completely prevents AUR/ERA- and AUR/BSO-induced accumulation of ubiquitinated proteins, NOXA upregulation and cell death, indicating that GSH depletion rather than ROS production is critical for AUR/BSO- or AUR/ERA-mediated cell death. Thus, by demonstrating that GSH-depleting agents enhance the antitumor activity of AUR, we highlight new treatment options for RMS by targeting the redox homeostasis.

Concomitant epigenetic targeting of LSD1 and HDAC synergistically induces mitochondrial apoptosis in rhabdomyosarcoma cells

The lysine-specific demethylase 1 (LSD1) is overexpressed in several cancers including rhabdomyosarcoma (RMS). However, little is yet known about whether or not LSD1 may serve as therapeutic target in RMS. We therefore investigated the potential of LSD1 inhibitors alone or in combination with other epigenetic modifiers such as histone deacetylase (HDAC) inhibitors. Here, we identify a synergistic interaction of LSD1 inhibitors (i.e., GSK690, Ex917) and HDAC inhibitors (i.e., JNJ-26481585, SAHA) to induce cell death in RMS cells. By comparison, LSD1 inhibitors as single agents exhibit little cytotoxicity against RMS cells. Mechanistically, GSK690 acts in concert with JNJ-26481585 to upregulate mRNA levels of the proapoptotic BH3-only proteins BMF, PUMA, BIM and NOXA. This increase in mRNA levels is accompanied by a corresponding upregulation of BMF, PUMA, BIM and NOXA protein levels. Importantly, individual knockdown of either BMF, BIM or NOXA significantly reduces GSK690/JNJ-26481585-mediated cell death. Similarly, genetic silencing of BAK significantly rescues cell death upon GSK690/JNJ-26481585 cotreatment. Also, overexpression of antiapoptotic BCL-2 or MCL-1 significantly protects RMS cells from GSK690/JNJ-26481585-induced cell death. Furthermore, GSK690 acts in concert with JNJ-26481585 to increase activation of caspase-9 and -3. Consistently, addition of the pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) significantly reduces GSK690/JNJ-26481585-mediated cell death. In conclusion, concomitant LSD1 and HDAC inhibition synergistically induces cell death in RMS cells by shifting the ratio of pro- and antiapoptotic BCL-2 proteins in favor of apoptosis, thereby engaging the intrinsic apoptotic pathway. This indicates that combined treatment with LSD1 and HDAC inhibitors is a promising new therapeutic approach in RMS.

Primary cardiac rhabdomyosarcoma developed after receiving radiotherapy for left breast cancer 18 years prior

The heart is an organ where primary malignant tumors rarely develop. In particular, the incidence of cardiac rhabdomyosarcoma (RMS) is extremely low. It has been reported that the risk of second malignant tumors in mediastinum is increased by radiotherapy in women with breast cancer. However, little is known about the association between irradiation to heart and cardiac RMS. Here, we report a case of a 68-year-old woman with primary cardiac RMS. She suddenly presented syncope at a workplace, and was taken to the emergency room at our hospital. Several imaging tests, including echocardiogram and cine magnetic resonance imaging, detected two tumors in the right ventricle (RV) and its outflow tract, which had almost obstructed the main trunk of the pulmonary artery (PA). To avoid sudden PA occlusion by the tumor, we emergently performed surgical excision of the tumors from the RV. Pathological analysis revealed that these tumors were embryonal type RMS. She had received radiotherapy after mastectomy for left breast cancer 18 years previously, and no recurrence of breast cancer had been detected. This cardiac RMS is considered as a second malignant tumor related to radiotherapy for breast cancer. <Learning objective: We experienced a 68-year-old woman having two tumors of the RMS in RV, who had received radiotherapy for left breast cancer 18 years previously and had previously presented no recurrence. There is literature suggesting that radiotherapy may increase the risk of soft-tissue sarcoma in women with breast cancer. We should be aware of cardiac RMS as a second malignant tumor related to radiotherapy for breast cancer, although its incidence is extremely low.>.

Small GTPase Arl6 controls RH30 rhabdomyosarcoma cell growth through ciliogenesis and Hedgehog signaling

Background

Rhabdomyosarcoma (RMS) originates from skeletal muscle precursors that fail to differentiate. Hedgehog (Hh) signaling and primary cilia contribute to the pathobiology of RMS.

Results

Here we showed ADP ribosylation factor like GTPase 6 (ARL6) localizes at the base of primary cilium, controls ciliogenesis and Hh signaling. The transcription of Arl6 is dynamic during the differentiation of myoblasts, companying with the growth and elimination of primary cilia. Arl6 expression is significantly up regulated in cilia-dependent RMS cells and tissues. Knockdown of Arl6 inhibits proliferation and promotes apoptosis of RMS RH30 cells through defected ciliogenesis and reduced Hh activity.

Conclusions

Taken together, the functions of Arl6 in ciliogenesis and Hh signaling suggest it as a potential RMS drug target.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-016-0126-2) contains supplementary material, which is available to authorized users.

Management of pediatric head and neck rhabdomyosarcoma: A case-series of 36 patients

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in the pediatric population. In 35% of cases, RMS develops in the head and neck (H&N) region, and only combined therapy is recognized as a curative treatment. However, recent advances in skull base and reconstructive surgery, along with microsurgery and endoscopic surgery, have strengthened the role of surgery as an important part of RMS treatment. In the present study, 36 pediatric RMS cases (24 males and 12 females) were analyzed after surgical treatment. The average age at diagnosis was 7 years. In total, 67% of tumors were localized in the parameningeal region. Alveolar RMS was the most common histopathological type. A total of 16 patients were treated due to disease recurrence or a previous non-radical surgical procedure, while 19 cases had inductive chemotherapy and/or radiotherapy preceding surgical treatment due to locally advanced disease. In 1 case, only diagnostic biopsy was performed. It is recommended that the management of H&N RMS is interdisciplinary from the beginning. Extensive surgical dissection in the H&N region for RMS may result in severe cosmetic defects and functional impairment; thus, these risks should be considered during treatment planning, and the surgical approach should be based on the individual characteristics of each patient.

JNJ-26481585 primes rhabdomyosarcoma cells for chemotherapeutics by engaging the mitochondrial pathway of apoptosis

Rhabdomyosarcoma (RMS) is a common soft-tissue sarcoma in childhood with a poor prognosis, highlighting the need for new treatment strategies. Here we identify a synergistic interaction of the second-generation histone deacetylase inhibitor (HDACI) JNJ-26481585 and common chemotherapeutic drugs (i.e. Doxorubicin, Etoposide, Vincristine, Cyclophosphamide and Actinomycin D) to trigger apoptosis in RMS cells. Importantly, JNJ-26481585/Doxorubicin cotreatment also significantly suppresses long-term clonogenic survival of RMS cells and tumor growth in vivo in a preclinical RMS model. Mechanistically, JNJ-26481585/Doxorubicin cotreatment causes upregulation of the BH3-only proteins Bim and Noxa as well as downregulation of the antiapoptotic proteins Mcl-1 and Bcl-xL. These changes in the ratio of pro- and antiapoptotic Bcl-2 proteins contribute to JNJ-26481585/Doxorubicin-mediated apoptosis, since knockdown of Bim or Noxa significantly inhibits cell death. Also, JNJ-26481585 and Doxorubicin cooperate to stimulate activation of Bax and Bak, which is required for JNJ-26481585/Doxorubicin-induced apoptosis, since silencing of Bax or Bak protects against apoptosis. Consistently, overexpression of Bcl-2 significantly reduces JNJ-26481585/Doxorubicin-mediated apoptosis. JNJ-26481585/Doxorubicin cotreatment leads to caspase activation and caspase-dependent apoptosis, since the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) rescues cells from apoptosis. In conclusion, the second-generation HDACI JNJ-26481585 cooperates with chemotherapeutics to engage mitochondrial apoptosis in RMS cells, demonstrating that JNJ-26481585 represents a promising strategy for chemosensitization of RMS.

FoxF1 and FoxF2 transcription factors synergistically promote rhabdomyosarcoma carcinogenesis by repressing transcription of p21Cip1 CDK inhibitor

The role of Forkhead Box F1 (FoxF1) transcription factor in carcinogenesis is not well characterized. Depending on tissue and histological type of cancer, FoxF1 was shown to be either oncogene or tumor suppressor. Alveolar rhabdomyosarcoma (RMS) is the most aggressive pediatric soft tissue sarcoma. While FoxF1 is highly expressed in alveolar RMS, the functional role of FoxF1 in RMS is unknown. The present study demonstrates that expression of FoxF1 and its closely related transcription factor FoxF2 are essential for rhabdomyosarcoma tumor growth. Depletion of FoxF1 or FoxF2 in rhabdomyosarcoma cells decreased tumor growth in orthotopic mouse models of RMS. The decreased tumorigenesis was associated with the reduced tumor cell proliferation. Cell cycle regulatory proteins Cdk2, Cdk4/6, Cyclin D1 and Cyclin E2 were decreased in FoxF1- and FoxF2-deficient RMS tumors. Depletion of either FoxF1 or FoxF2 delayed G1-S cell cycle progression, decreased levels of phosphorylated Rb and increased protein levels of the CDK inhibitors, p21^Cip1 and p27^Kip1. Depletion of both FoxF1 and FoxF2 in tumor cells completely abrogated RMS tumor growth in mice. Overexpression of either FoxF1 or FoxF2 in tumor cells was sufficient to increase carcinogenesis in orthotopic RMS mouse model. FoxF1 and FoxF2 directly bound to and repressed transcriptional activity of p21^Cip1 promoter through −556/−545 bp region, but did not affect p27^Kip1 transcription. Knockdown of p21^Cip1 restored cell cycle progression in the FoxF1- or FoxF2-deficient tumor cells. Altogether, FoxF1 and FoxF2 promoted RMS tumorigenesis by inducing tumor cell proliferation via transcriptional repression of p21^Cip1 gene promoter. Due to robust oncogenic activity in RMS tumors, FoxF1 and FoxF2 may represent promising targets for anti-tumor therapy.

CYP2B6rs2279343 Is Associated with Improved Survival of Pediatric Rhabdomyosarcoma Treated with Cyclophosphamide

Background

Rhabdomyosarcoma (RMS) is a small round blue cell malignant tumor, representing 7% of childhood malignancies, and over 50% of all soft tissue sarcomas. Cyclophosphamide (CPA) is a prodrug and is the mainstay of RMS treatment. CYP2B6 is a highly polymorphic drug metabolizing enzyme involved in CPA bioactivation. The influence of CYP2B6 single nucleotide polymorphisms (SNPs) on the survival of RMS is still unknown.

Methods

We genotyped CYP2B6SNPs rs2279343, rs3745274, and rs3211371 by restriction fragment polymorphism (RFLP) after PCR amplification in a cohort of 73 pediatric RMS patients treated with CPA-based first line treatment. We then analyzed the association between those genotypes and survival outcome of RMS.

Results

The frequencies of CYP2B6 rs2279343, rs3745274, and rs3211371 were 63%, 45.2%, and 5.5%, respectively. There was no association between rs3745274, rs3211371 genotypes and survival outcomes of RMS. However, the carriers of at least one mutant allele CYP2B6rs2279343 had significantly longer event-free survival (p-value = 0.03).

Conclusion

Our results demonstrated that CYP2B6 rs2279343 may predict EFS in RMS patients and warrants future studies to clarify the pharmacogenetics of CPA in pediatrics. If validated, integration of genetic factors with clinical and molecular characteristics could be used for a composite algorithm to better stratify risk prior to treatment.

Store-operated Ca(2+) entry in rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS), the most common pediatric soft tissue sarcoma, has an intrinsic or early-acquisition of resistance to chemo- and radiation therapy. Molecular determinants pivotal for RMS migration, metastatic invasion, cell proliferation, and survival are incompletely identified. Migration and cell proliferation were shown to correlate with cytosolic Ca(2+) activity ([Ca(2+)]i). Store-operated Ca(2+)-entry (SOCE) that increases intracellular [Ca(2+)] is accomplished by Orai1, a pore-forming ion channel unit, the expression of which is stimulated by the transcription factor NFκB. The present study explored the expression of Orai1 and its regulators STIM1 and NFκB in human rhabdomyosarcoma cell lines and analyzed their impact on cell proliferation and migration. For the study human rhabdomyosarcoma cell lines RD (embryonal) and RH30 (alveolar) were analyzed for Orai1, STIM1, and NFκB transcription by RT-PCR and their corresponding proteins in Western blot. [Ca(2+)]i was detected via Fura-2 fluorescence and SOCE - resulting from [Ca(2+)]i increase following store depletion with extracellular Ca(2+) removal and inhibition of the sarcoendoplasmatic reticular Ca(2+) ATPase - detected with thapsigargin. Cell migration was analyzed in transwell and mitotic cell death with the clonogenic assay. In summary, Orai1, STIM1, and NFκB are expressed in embryonal (RD) and alveolar (RH30) rhabdomyosarcoma. SOCE inhibitor BTP2, Orai1 inhibitor 2-APB, or NFκB inhibitor wogonin virtually abrogated (BTP2, 2-APB) or significantly reduced (wogonin) SOCE. Moreover, SOCE inhibitors 2-APB and BTP2 and wogonin significantly inhibited migration and proliferation of both, RD and RH30 cells. These results suggest that Orai1 signaling is involved in SOCE into rhabdomyosarcoma cells thus contributing to migration, invasion and proliferation.

Overview of embryonal rhabdomyosarcoma of cervix in women over 40-year-old

The literature on cervical embryonal rhabdomyosarcoma (RMS) is reviewed here to identify management guidelines for middle-aged women diagnosed with this rare type of gynecologic cancer. Specifically, the PubMed, Web of Science and Google Scholar databases, were searched to find published case series on cervical embryonal RMS reporting on four or more patients, of whom at least one was > 40-year-old. The χ² test was used to assess heterogeneity. Five articles published between 1986 and 2013 were identified, reporting on a total of 47 patients, of whom 22 (46.8%) were older and 25 (53.2%) younger than 40-year-old. Although the two age groups did not differ significantly by stage of disease or radiotherapy treatment, the older age group received less chemotherapy (55% vs 90%, P = 0.008) and had more hysterectomy (86% vs 43%, P = 0.009). Follow-up data was missing for 18/47 (38.3%) patients. Among the 29 patients with follow-up data, survival was shorter in the older group, with 8/12 (67%) alive and 3 with disease at a median follow-up of 2.6 years, as compared with the younger group that had 15/17 (88%) alive and none with disease at a median follow-up of 3.5 years. The longest survivals among the older women were observed in those who received radiotherapy, including one case with a resected lung metastasis. A prospective multi-institutional collaboration and better follow-up are needed to determine the optimal management of cervical embryonal RMS. Long-term survival appears feasible if management is accompanied by chemotherapy and radiotherapy.

Critical role of mitochondria-mediated apoptosis for JNJ-26481585-induced antitumor activity in rhabdomyosarcoma

JNJ-26481585 is a second-generation histone deacetylase inhibitor with broad-range efficacy and improved pharmacodynamic properties. In the present study, we investigated the therapeutic potential of JNJ-26481585 and its molecular mechanisms of action in rhabdomyosarcoma (RMS). Here, we report that JNJ- 26481585's anticancer activity critically depends on an intact mitochondrial pathway of apoptosis. JNJ-26481585 induces apoptosis and also inhibits long-term clonogenic survival of several RMS cell lines at nanomolar concentrations that cause histone acetylation. Importantly, JNJ-26481585 significantly suppresses tumor growth in vivo in two preclinical RMS models, that is, the chorioallantoic membrane model and a xenograft mouse model. Mechanistically, we identify activation of the mitochondrial pathway of apoptosis as a key event that is critically required for JNJ-26481585-mediated cell death. JNJ-26481585 upregulates expression levels of several BH3-only proteins including Bim, Puma and Noxa, which all contribute to JNJ-26481585-mediated apoptosis, as knockdown of Bim, Puma or Noxa significantly inhibits cell death. This shift toward proapoptotic Bcl-2 proteins promotes activation of Bax and Bak as a critical event, as genetic silencing of Bax or Bak protects against JNJ-26481585-induced apoptosis. Intriguingly, rescue experiments reveal that JNJ-26481585 triggers Bax/Bak activation independently of caspase activation and activates caspase-9 as the initiator caspase in the cascade, as Bcl-2 overexpression, but not the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) blocks JNJ-26481585-induced Bax/Bak activation and caspase-9 cleavage. In conclusion, JNJ-26481585 exerts potent antitumor activity against RMS in vitro and in vivo by engaging mitochondrial apoptosis before caspase activation and represents a promising therapeutic for further investigation in RMS.

Endoscopic endonasal approach to the lateral orbital apex: case report

Although the medial and inferior orbital apex are considered safely accessible using the endonasal endoscopic approach, the lateral apex has been considered unsafe to access since the optic nerve lies between the surgeon and the pathology. The authors present the case of a 4-year-old girl with recurrent rhabdomyosarcoma attached to the lateral rectus muscle located lateral and inferior to the optic nerve in the orbital apex. The tumor was totally resected through an endoscopic endonasal transmaxillary transpterygoidal approach using a 45° endoscope. A gross-total resection was achieved, and the patient's vision was unchanged. This procedure is a safe, minimal-access alternative to open procedures in selected cases and provides evidence that increases the applicability of the endonasal endoscopic approach to reach the lateral compartment of the orbital apex.

Autoregulatory loop between TGF-β1/miR-411-5p/SPRY4 and MAPK pathway in rhabdomyosarcoma modulates proliferation and differentiation

The origin of rhabdomyosarcoma (RMS) remains controversial. However, specific microRNAs (miRNAs) are downregulated in RMS and it is possible that re-expression of these miRNAs may lead to differentiation. Transforming growth factor-β1 (TGF-β1) is known to block differentiation of RMS. We therefore analyzed miRNA microarrays of RMS cell lines with or without TGF-β1 knockdown and identified a novel anti-oncogene miR-411-5p. Re-expression of miR-411-5p inhibited RMS cell proliferation in vitro and tumorigenicity in vivo. Using a luciferase reporting system and sequence analysis, the potential target of miR-411-5p was identified as sprouty homolog 4 (SPRY4), which inhibits protein kinase Cα-mediated activation of mitogen-activated protein kinases (MAPKs), especially p38MAPK phosphorylation. These results revealed an inverse correlation between TGF-β1/SPRY4 and miR-411-5p levels. SPRY4 small interfering RNA and miR-411-5p both activated p38MAPK phosphorylation and also promoted apoptosis and myogenic differentiation, indicated by increased caspase-3, myosin heavy chain, and myosin expression. SPRY4 and miR-411 mRNA levels correlated with TGF-β1 expression levels in RMS tissues, which was confirmed by immunohistochemical staining for TGF-β1, SPRY4, and phosphorylated p38MAPK proteins. Overall, these results indicate that miR-411-5p acts as an RMS differentiation-inducing miRNA prompting p38MAPK activation via directly downregulating SPRY4. These results establish an autoregulatory loop between TGF-β1/miR-411-5p/SPRY4 and MAPK in RMS, which governs the switch between proliferation and differentiation.

Pancreatic pleomorphic rhabdomyosarcoma

INTRODUCTION

Rhabdomyosarcoma (RMS) is a primary malignancy that arises from the embryonic mesenchyme with the potential to differentiate into skeletal muscle. RMS of the biliary tree is extremely rare. We report a case of an undifferentiated pleomorphic RMS involving the liver and pancreas.

PRESENTATION OF CASE

A 62 year old Caucasian woman with rapidly growing abdominal mass and a history of endometrial adenocarcinoma underwent laparotomy due to compression symptoms and concerns of malignancy. A large mass arising from the pancreas and extending into the liver was identified and resected with a distal pancreatectomy associated with a left lateral liver segmentectomy. A diagnosis of pleomorphic RMS was made from the pathology specimen. Chemotherapy and radiotherapy were also performed. Unfortunately the patient died 2 years following treatment due to recurrence of the disease.

DISCUSSION

P-RMS in the biliary tree is extremely rare (0.5%) and mostly seen in infants and children. Preoperative diagnosis is challenging since the symptoms are unspecific. Preoperative imaging rarely contributes to the final diagnosis. The only possible treatment for adult RMS is surgical resection of the tumor followed by chemotherapy and radiotherapy. Long-term prognosis of P-RMS reported (predominantly of limbs) is poor. To our knowledge, no previous cases of RMS originating from the pancreas have been reported.

CONCLUSION

However RMS is an extremely rare tumor in adults, it should be included in the differential diagnosis of patients with atypical pancreatic and liver lesions.

Targeted killing of rhabdomyosarcoma cells by a MAP-based human cytolytic fusion protein

The treatment of rhabdomyosarcoma (RMS) is challenging, and the prognosis remains especially poor for high-grade RMS with metastasis. The conventional treatment of RMS is based on multi-agent chemotherapy combined with resection and radiotherapy, which are often marked by low success rate. Alternative therapeutic options include the combination of standard treatments with immunotherapy. We generated a microtubule-associated protein (MAP)-based fully human cytolytic fusion protein (hCFP) targeting the fetal acetylcholine receptor, which is expressed on RMS cells. We were able to express and purify functional scFv35-MAP from Escherichia coli cells. Moreover, we found that scFv35-MAP is rapidly internalized by target cells after binding its receptor, and exhibits specific cytotoxicity toward FL-OH1 and RD cells in vitro. We also confirmed that scFv35-MAP induces apoptosis in FL-OH1 and RD cells. The in vivo potential of scFv35-MAP will need to be considered in further studies.

An emerging evidence base for PET-CT in the management of childhood rhabdomyosarcoma: systematic review

INTRODUCTION

Rhabdomyosarcoma (RMS) management depends on risk stratification at diagnosis and treatment response. Assessment methods include CT, MRI, bone scintigraphy, histological analysis and bone marrow biopsy. Advanced functional imaging (FI) has potential to improve staging accuracy and management strategies.

METHODS AND ANALYSIS

We conducted a systematic review (PROSPERO 2013:CRD42013006128) of diagnostic accuracy and clinical effectiveness of FI in histologically proven paediatric RMS. PRISMA guidance was followed. We searched 10 databases to November 2013. Studies with ≥10 patients with RMS which compared positron emission tomography (PET), PET-CT or diffusion-weighted imaging (DWI) MRI to conventional imaging at any treatment stage were included. Study quality was assessed. Limited, heterogeneous effectiveness data required narrative synthesis, illustrated by plotting sensitivity and specificity in receiver operating curve (ROC) space.

RESULTS

Eight studies (six PET-CT, two PET) with 272 RMS patients in total were included. No DWI-MRI studies met inclusion criteria. Pooled estimates were not calculated due to sparseness of data. Limited evidence indicated initial PET-CT results were predictive of survival. PET-CT changed management of 7/40 patients. Nodal involvement PET-CT: sensitivity ranged from 80% to 100%; specificity from 89% to 100%. Distant metastatic involvement: PET-CT sensitivity ranged from 95% to 100%; specificity from 80% to100%. Data on metastases in different sites were sparse. Limited data were found on outcome prediction by PET-CT response.

DISSEMINATION AND ETHICS

PET/PET-CT may increase initial staging accuracy in paediatric RMS, specifically in the detection of nodal involvement and distant metastatic spread. There is a need to further assess PET-CT for this population, ideally in a representative, unbiased and transparently selected cohort of patients.

MiR-214 and N-ras regulatory loop suppresses rhabdomyosarcoma cell growth and xenograft tumorigenesis

Rhabdomyosarcoma (RMS) is a childhood malignant soft tissue cancer that is derived from myogenic progenitors trapped in a permanent mode of growth. Here, we report that miR-214 is markedly down-regulated in human RMS cell lines. Although not required for embryogenesis in mice, miR-214 suppresses mouse embryonic fibroblast (MEF) proliferation. When re-introduced into RD cells, a line of human embryonal RMS cells, miR-214 showed inhibition of tumor cell growth, induction of myogenic differentiation and apoptosis, as well as suppression of colony formation and xenograft tumorigenesis. We show that in the absence of miR-214, expression of proto-oncogene N-ras is markedly elevated in miR-214^−/− MEFs, and manipulations of miR-214 levels using microRNA mimics or inhibitor in RD cells reciprocally altered N-ras expression. We further demonstrate that forced expression of N-ras from a cDNA that lacks its 3'-untranslated region neutralized the pro-myogenic and anti-proliferative activities of miR-214. Finally, we show that N-ras is a conserved target of miR-214 in its suppression of xenograft tumor growth, and N-ras expression is up-regulated in xenograft tumor models as well as actual human RMS tissue sections. Taken together, these data indicate that miR-214 is a bona fide suppressor of human RMS tumorigensis.

MicroRNAs and epigenetic mechanisms of rhabdomyosarcoma development

Rhabdomyosarcoma is the most common type of soft tissue sarcoma in children. Two main subtypes of rhabdomyosarcoma with different molecular pattern and distinct clinical behaviour may be identified - embryonal and alveolar rhabdomyosarcoma. All types of rhabdomyosarcoma are believed to be of myogenic origin as they express high levels of myogenesis-related factors. They all, however, fail to undergo a terminal differentiation which results in tumour formation. In the aberrant regulation of myogenesis in rhabdomyosarcoma, microRNAs and epigenetic factors are particularly involved. Indeed, these mediators seem to be even more significant for the development of rhabdomyosarcoma than canonical myogenic transcription factors like MyoD, a master regulatory switch for myogenesis. Therefore, in this review we focus on the regulation of rhabdomyosarcoma progression by microRNAs, and especially on microRNAs of the myo-miRNAs family (miR-1, -133a/b and -206), other well-known myogenic regulators like miR-29, and on microRNAs recently recognized to play a role in the differentiation of rhabdomyosarcoma, such as miR-450b-5p or miR-203. We also review changes in epigenetic modifiers associated with rhabdomyosarcoma, namely histone deacetylases and methyltransferases, especially from the Polycomp Group, like Yin Yang1 and Enhancer of Zeste Homolog2. Finally, we summarize how the functioning of these molecules can be affected by oxidative stress and how antioxidative enzymes can influence the development of this tumour. This article is part of a Directed Issue entitled: Rare Cancers.

Pan-mammalian target of rapamycin (mTOR) inhibitor AZD8055 primes rhabdomyosarcoma cells for ABT-737-induced apoptosis by down-regulating Mcl-1 protein

The PI3K/mammalian Target of Rapamycin (mTOR) pathway is often aberrantly activated in rhabdomyosarcoma (RMS) and represents a promising therapeutic target. Recent evaluation of AZD8055, an ATP-competitive mTOR inhibitor, by the Preclinical Pediatric Testing Program showed in vivo antitumor activity against childhood solid tumors, including RMS. Therefore, in the present study, we searched for AZD8055-based combination therapies. Here, we identify a new synergistic lethality of AZD8055 together with ABT-737, a BH3 mimetic that antagonizes Bcl-2, Bcl-xL, and Bcl-w but not Mcl-1. AZD8055 and ABT-737 cooperate to induce apoptosis in alveolar and embryonal RMS cells in a highly synergistic fashion (combination index < 0.2). Synergistic induction of apoptosis by AZD8055 and ABT-737 is confirmed on the molecular level, as AZD8055 and ABT-737 cooperate to trigger loss of mitochondrial membrane potential, activation of caspases, and caspase-dependent apoptosis that is blocked by the pan-caspase inhibitor Z-VAD-fmk. Similar to AZD8055, the PI3K/mTOR inhibitor NVP-BEZ235, the PI3K inhibitor NVP-BKM120 and Akt inhibitor synergize with ABT-737 to trigger apoptosis, whereas no cooperativity is found for the mTOR complex 1 inhibitor RAD001. Interestingly, molecular studies reveal a correlation between the ability of different PI3K/mTOR inhibitors to potentiate ABT-737-induced apoptosis and to suppress Mcl-1 protein levels. Importantly, knockdown of Mcl-1 increases ABT-737-induced apoptosis similar to AZD8055/ABT-737 cotreatment. This indicates that AZD8055-mediated suppression of Mcl-1 protein plays an important role in the synergistic drug interaction. By identifying a novel synergistic interaction of AZD8055 and ABT-737, our findings have important implications for the development of molecular targeted therapies for RMS.

Obatoclax (GX15-070) triggers necroptosis by promoting the assembly of the necrosome on autophagosomal membranes

Obatoclax (GX15-070), a small-molecule inhibitor of antiapoptotic Bcl-2 proteins, has been reported to trigger cell death via autophagy. However, the underlying molecular mechanisms have remained elusive. Here, we identify GX15-070-stimulated assembly of the necrosome on autophagosomal membranes as a key event that connects GX15-070-stimulated autophagy to necroptosis. GX15-070 predominately induces a non-apoptotic form of cell death in rhabdomyosarcoma cells, as evident by lack of typical apoptotic features such as DNA fragmentation or caspase activation and by insensitivity to the broad-range caspase inhibitor zVAD.fmk. Instead, GX15-070 triggers massive accumulation of autophagosomes, which are required for GX15-070-induced cell death, as blockade of autophagosome formation by silencing of Atg5 or Atg7 abolishes GX15-070-mediated cell death. Co-immunoprecipitation studies reveal that GX15-070 stimulates the interaction of Atg5, a constituent of autophagosomal membranes, with components of the necrosome such as FADD, RIP1 and RIP3. This GX15-070-induced assembly of the necrosome on autophagosomes occurs in a Atg5-dependent manner, as knockdown of Atg5 abrogates formation of this complex. RIP1 is necessary for GX15-070-induced cell death, as both genetic and pharmacological inhibition of RIP1 by shRNA-mediated knockdown or by the RIP1 inhibitor necrostatin-1 blocks GX15-070-induced cell death. Similarly, RIP3 knockdown rescues GX15-070-mediated cell death and suppression of clonogenic survival. Interestingly, RIP1 or RIP3 silencing has no effect on GX15-070-stimulated autophagosome formation, underlining that RIP1 and RIP3 mediate cell death downstream of autophagy induction. Of note, GX15-070 significantly suppresses tumor growth in a RIP1-dependent manner in the chorioallantoic membrane model in vivo. In conclusion, GX15-070 triggers necroptosis by promoting the assembly of the necrosome on autophagosomes. These findings provide novel insights into the molecular mechanisms of GX15-070-induced non-apoptotic cell death.

Synthetic lethal interaction between PI3K/Akt/mTOR and Ras/MEK/ERK pathway inhibition in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) frequently exhibits concomitant activation of the PI3K/Akt/mTOR and the Ras/MEK/ERK pathways. Therefore, we investigated whether pharmacological cotargeting of these two key survival pathways suppresses RMS growth. Here, we identify a synthetic lethal interaction between PI3K/Akt/mTOR and Ras/MEK/ERK pathway inhibition in RMS. The dual PI3K/mTOR inhibitor PI103 and the MEK inhibitor UO126 synergize to trigger apoptosis in several RMS cell lines in a highly synergistic manner (combination index <0.1), whereas either agent alone induces minimal cell death. Similarly, genetic knockdown of p110α and MEK1/2 cooperates to induce apoptosis. Molecular studies reveal that cotreatment with PI103/UO126 cooperates to suppress PI3K/Akt/mTOR and Ras/MEK/ERK signaling, whereas either compound alone is not only less effective to inhibit signaling, but even cross-activates the other pathway. Accordingly, PI103 alone increases ERK phosphorylation, while UO126 enhances Akt phosphorylation, consistent with negative crosstalks between these two signaling pathways. Furthermore, PI103/UO126 cotreatment causes downregulation of several antiapoptotic proteins such as XIAP, Bcl-xL and Mcl-1 as well as increased expression and decreased phosphorylation of the proapoptotic protein BimEL, thus shifting the balance towards apoptosis. Consistently, PI103/UO126 cotreatment cooperates to trigger Bax activation, loss of mitochondrial membrane potential, caspase activation and caspase-dependent apoptosis. This identification of a synthetic lethal interaction between PI3K/mTOR and MEK inhibitors has important implications for the development of novel treatment strategies in RMS.

Targeting the fetal acetylcholine receptor in rhabdomyosarcoma

INTRODUCTION

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood and adolescence. Recent efforts to enhance overall survival of patients with clinically advanced RMS have failed and there is a demand for conceptually novel treatments. Immune therapeutic options targeting the fetal nicotinic acetylcholine receptor (fnAChR), which is broadly expressed on RMS, are novel approaches to overcome the therapeutic resistance of RMS. Expression of the fnAChR is restricted to developing fetal muscles, some apparently dispensable ocular muscle fibers and thymic myoid cells. Therefore, after-birth fnAChR is a tumor-associated and almost tumor-specific antigen on RMS cells.

AREAS COVERED

This review gives an overview on nAChR function and expression pattern in RMS tumor cells, and deals with the immunological significance of fnAChR-expressing cells, including the risk of anti-nAChR autoimmunity as a potential side effect of fnAChR-directed immunotherapies. The article also addresses the advantages and disadvantages of vaccination strategies, immunotoxins and chimeric T cells targeting the fnAChR.

EXPERT OPINION

Finally, we suggest technical and biological strategies to improve the available immunotherapeutic tools including increasing the in vivo expression of the target fnAChR on RMS cells.

RIP1 protein-dependent assembly of a cytosolic cell death complex is required for inhibitor of apoptosis (IAP) inhibitor-mediated sensitization to lexatumumab-induced apoptosis

Searching for new strategies to trigger apoptosis in rhabdomyosarcoma (RMS), we investigated the effect of two novel classes of apoptosis-targeting agents, i.e. monoclonal antibodies against TNF-related apoptosis-inducing ligand (TRAIL) receptor 1 (mapatumumab) and TRAIL receptor 2 (lexatumumab) and small-molecule inhibitors of inhibitor of apoptosis (IAP) proteins. Here, we report that IAP inhibitors synergized with lexatumumab, but not with mapatumumab, to reduce cell viability and to induce apoptosis in several RMS cell lines in a highly synergistic manner (combination index <0.1). Cotreatment-induced apoptosis was accompanied by enhanced activation of caspase-8, -9, and -3; loss of mitochondrial membrane potential; and caspase-dependent apoptosis. In addition, IAP inhibitor and lexatumumab cooperated to stimulate the assembly of a cytosolic complex containing RIP1, FADD, and caspase-8. Importantly, knockdown of RIP1 by RNA interference prevented the formation of the RIP1·FADD·caspase-8 complex and inhibited subsequent activation of caspase-8, -9, and -3; loss of mitochondrial membrane potential; and apoptosis upon treatment with IAP inhibitor and lexatumumab. In addition, RIP1 silencing rescued clonogenic survival of cells treated with the combination of lexatumumab and IAP inhibitor, thus underscoring the critical role of RIP1 in cotreatment-induced apoptosis. By comparison, the TNFα-blocking antibody Enbrel had no effect on IAP inhibitor/lexatumumab-induced apoptosis, indicating that an autocrine TNFα loop is dispensable. By demonstrating that IAP inhibitors and lexatumumab synergistically trigger apoptosis in a RIP1-dependent but TNFα-independent manner in RMS cells, our findings substantially advance our understanding of IAP inhibitor-mediated regulation of TRAIL-induced cell death.

Perianal rhabdomyosarcoma presenting 21 months after hamartoma excision

Perianal rhabdomyosarcoma is a rare type of tumor with a relatively poor prognosis. We present the case of a patient who presented with a cutaneous perianal hamartoma at the age of 6 weeks. 21 months latter a recurrent mass at the excision site proved to be an embryonal rhabdomyosarcoma involving the anal sphincter. A pathologic review of the two specimens confirmed their relatedness. This report highlights the need to maintain a high level of suspicion in cases of recurrence following excision of a benign lesion.