Dual Differentiation Research Articles

Treatment of a mixed acinar-endocrine carcinoma with uptake on 68Gallium-DOTATOC positron emission tomography-computed tomography: A case report

The case of a 35-year old female patient with a diagnosis of metastatic mixed acinar-endocrine carcinoma (MAEC) is investigated in the present study. The patient was believed to have a well-differentiated neuroendocrine tumor (NET) with a high Ki-67 index and uptake on 68Gallium-DOTATOC positron emission tomography-computed tomography for 9 years, and was treated accordingly. The patient had long lasting disease control by treatment with sunitinib, and a response was observed in numerous lesions with peptide receptor radionuclide therapy (PRRT). Following treatment for metastatic disease for >4 years, liver transplantation was performed, as an exception to normal recommendations, at the time of progression of a centrally located liver lesion inducing obstructive jaundice. Following transplantation, the diagnosis of a Grade 3 NET, as defined by the WHO 2010 classification, was challenged and changed to MAEC. MAEC is a rare type of tumor of the pancreas, exhibiting endocrine and acinar differentiation. It is difficult to diagnose, often being misidentified as acinar cell carcinoma or predominantly as neuroendocrine neoplasms. Immunohistochemical labelling provides the only evidence for the dual differentiation of neuroendocrine (synaptophysin and chromogranin) and acinar (lipase, trypsin and chymotrypsin) cell markers. Studies investigating MAECs with a clear histopathological diagnosis are scarce, in addition to evidence of disease behaviour and treatment options. It is generally agreed that surgery is the primary treatment in patients with resectable tumors. The responses to sunitinib and PRRT suggested that treatments considered or developed for NETs may be beneficial in MAEC cases.

Dual Energy CT Kidney Stone Differentiation in Photon Counting Computed Tomography.

This study evaluates the capabilities of a whole-body photon counting CT system to differentiate between four common kidney stone materials, namely uric acid (UA), calcium oxalate monohydrate (COM), cystine (CYS),and apatite (APA) ex vivo. Two different x-ray spectra (120 kV and 140 kV) were applied and two acquisition modes were investigated; The macro-mode generates two energy threshold based image-volumes and two energy bin based image-volumes. In the chesspattern-mode, however, four energy thresholds are applied. A virtual low energy image, as well as a virtual high energy image are derived from initial threshold-based images, while considering their statistically correlated nature. The energy bin based images of the macro-mode, as well as the virtual low and high energy image of the chesspattern-mode serve as input for our dual energy evaluation. The dual energy ratio of the individually segmented kidney stones were utilized to quantify the discriminability of the different materials. The dual energy ratios of the two acquisition modes showed high correlation for both applied spectra. Wilcoxon-rank sum tests and the evaluation of the area under the receiver operating characteristics curves suggest that the UA kidney stones are best differentiable from all other materials (AUC = 1.0), followed by CYS (AUC ≈ 0.9 compared against COM and APA). COM and APA, however, are hardly distinguishable (AUC between 0.63 and 0.76). The results hold true for the measurements of both spectra and both acquisition modes.

Immunophenotypic features of dedifferentiated skull base chordoma: An insight into the intratumoural heterogeneity.

Chordomas are rare and low-grade malignant solid tumours, despite their histologically benign appearance, that arise in the bone from embryonic notochordal vestiges of the axial skeleton, a mesoderm-derived structure that is involved in the process of neurulation and embryonic development. Chordomas occurring in the skull base tend to arise in the basiocciput along the clivus. Three major morphological variants have been described (classical, chondroid, and atypical/dedifferentiated). The pathogenesis and molecular mechanisms involved in chordoma development remain uncertain. From a pathological standpoint, the microenvironment of a chordoma is heterogeneous, showing a dual epithelial-mesenchymal differentiation. These tumours are characterised by slow modality of biologic growth, local recurrence, low incidence of metastasis rates, and cancer stem cell (CSC) phenotype. The main molecular findings are connected with brachyury immunoexpression and activation of the downstream Akt and mTOR signalling pathways. The differentiation between typical and atypical chordomas is relevant because the tumoural microenvironment and prognosis are partially different. This review provides an insight into the recent and relevant concepts and histochemical markers expressed in chordomas, with special emphasis on dedifferentiated chordomas and their prognostic implications.

Littoral-cell angioma of the spleen: a case report.

Littoral-cell angioma (LCA), a primary angioma which clinically belongs to splenic hemangioma, can be mostly found in normal spleen red sinus shore cells of reticuloendothelial cell system. The cells of LCA strongly express endothelial and tissue cell associated antigens that indicate a dual differentiation characteristic; whereas only endothelial cell markers are positive in normal spleen red sinus shore cells. Diagnosis of LCA relies on histopathology. Regular follow-up is needed to monitor recurrence and metastasis.

41 - Novel Cytogenetic Findings in a Case of Mixed Phenotype Acute Leukemia With a Complex Karyotype

Mixed phenotype acute leukemia (MPAL) is a rare hematological malignancy characterized by combinatorial aberrations involving cells of the myeloid, T-, and/or B- lineages, most often diagnosed by means of immunophenotyping in order to assess lineage-specific markers, which can still yield inconclusive diagnoses. The most recurrent cytogenetic correlates of MPAL are t(9;22)(q34;q11.2) resulting in the BCR-ABL1 fusion gene or rearrangements involving MLL (11q23), the former of which is associated with a poor prognosis. MPAL with a complex karyotype (3 or more chromosomal abnormalities) is likewise associated with a poor prognosis, but limited data is available about the cytogenetic abnormalities present in this context. Herein, we present the case of a 67-year-old female whose bone marrow biopsy revealed an extensive blast population showing dual morphologic differentiation including lymphoblasts and larger myeloblasts with monocytic differentiation. Multiparametric immunophenotyping by flow cytometry revealed a blast population that was positive for CD45, CD19, CD22, CD34, CD38, and HLA-DR. The blast populations were also immunereactive for both myeloperoxidase and TdT; thus, a diagnosis of mixed phenotype acute leukemia was rendered. Conventional cytogenetic analysis revealed a hyperdiploid composite karyotype with numerical abnormalities involving chromosomes 2, 6, 8, 10, 11, 14, 19, 20, 21, and 22 as well as structural abnormalities involving 1p, 1q, 9p, 16p, 17p, 19q, 20q, and a marker chromosome. Concurrent interphase and metaphase FISH studies were able to detect a deletion of CDKN2A/p16 at 9p21 and corroborated the presence of extra copies of chromosomes 8, 11, 20, and 22. This case provides further insight into the plethora of cytogenetic abnormalities not involving BCR-ABL1 and/or MLL present in MPAL with a complex karyotype and adds to the pool of cytogenetic information about this rare subset of hematological malignancies.

Mixed Adenoneuroendocrine Carcinoma Is a Rare but Important Tumour Found in the Oesophagus.

Mixed adenoneuroendocrine carcinoma (MANEC) is a rare tumour of the gastrointestinal tract that consists of a dual adenocarcinomatous and neuroendocrine differentiation, each component representing at least 30% of the tumour. We report a case of a 68-year-old man who presented with two-month history of postprandial pain and vomiting. Gastric endoscopy revealed a polypoid mass in the lower part of the oesophagus. In contrast to the majority of these tumours, this biopsy was immunohistochemically positive for chromogranin A, and synaptophysin and Ki-67 index was 50% and the tumour was diagnosed as poorly differentiated neuroendocrine carcinoma of the oesophagus. The patient underwent surgery and lower oesophagus resection was performed. Based on the histopathology and immunohistochemistry of the tumour in the oesophagogastrectomy specimen, a mixed adenoneuroendocrine carcinoma (MANEC) was diagnosed. The objective of this case report is to advocate for the focus on the MANEC diagnosis as such patients need to be referred to a centre of excellence with expertise in NET tumours, to have the correct diagnostic work-up, treatment, and secondary diagnostic procedures performed at progression, as this will have paramount influence of the choice of treatment.

Mesodermal iPSC-derived progenitor cells functionally regenerate cardiac and skeletal muscle.

Conditions such as muscular dystrophies (MDs) that affect both cardiac and skeletal muscles would benefit from therapeutic strategies that enable regeneration of both of these striated muscle types. Protocols have been developed to promote induced pluripotent stem cells (iPSCs) to differentiate toward cardiac or skeletal muscle; however, there are currently no strategies to simultaneously target both muscle types. Tissues exhibit specific epigenetic alterations; therefore, source-related lineage biases have the potential to improve iPSC-driven multilineage differentiation. Here, we determined that differential myogenic propensity influences the commitment of isogenic iPSCs and a specifically isolated pool of mesodermal iPSC-derived progenitors (MiPs) toward the striated muscle lineages. Differential myogenic propensity did not influence pluripotency, but did selectively enhance chimerism of MiP-derived tissue in both fetal and adult skeletal muscle. When injected into dystrophic mice, MiPs engrafted and repaired both skeletal and cardiac muscle, reducing functional defects. Similarly, engraftment into dystrophic mice of canine MiPs from dystrophic dogs that had undergone TALEN-mediated correction of the MD-associated mutation also resulted in functional striatal muscle regeneration. Moreover, human MiPs exhibited the same capacity for the dual differentiation observed in murine and canine MiPs. The findings of this study suggest that MiPs should be further explored for combined therapy of cardiac and skeletal muscles.

Pituitary adenoma-neuronal choristoma is a pituitary adenoma with ganglionic differentiation

The presence of ganglion cells within an endocrine pituitary tumor has been named hamartoma, choristoma, gangliocytoma, or most recently pituitary adenoma-neuronal choristoma (PANCH). The presence of neuronal differentiation in regular pituitary adenomas has been previously suggested, however, its origin, the extent of its presence, and the relationship between the neuronal elements and the pituitary adenoma remain uncertain. Thus, to further explore the neuronal potential of pituitary tumors, we used immunohistochemistry on pituitary tumors of different grades, with a neuronal antigen protein (NeuN) antibody as a specific marker for mature neuronal differentiation. We found NeuN expression in 26.47% (9/34) cases of pituitary tumors without ganglionic differentiation (7 adenomas, 1 atypical adenoma and 1 pituitary carcinoma), in addition to NeuN expression in pituitary adenomas with ganglionic cells (2/2). Thus, neuronal expression is an innate property of pituitary adenomas. We propose that the rare presence of ganglionic cells in pituitary adenomas is not the result of a separate lesion or “collision sellar tumors”, as previously suggested, but a ganglionic neuronal differentiation in an endocrine neoplasm. The ganglionic cells may be arising from uncommitted stem/progenitor cells that contain both neuronal and endocrine properties. A label of “pituitary adenoma with ganglionic differentiation” would better reflect the dual differentiation in a neuroendocrine tumor than the current label “PANCH”.

The pericyte antigen RGS5 in perivascular soft tissue tumors

Perivascular soft tissue tumors are relatively uncommon neoplasms of unclear lineage of differentiation, although most are presumed to originate from or differentiate to pericytes or a modified perivascular cell. Among these, glomus tumor, myopericytoma, and angioleiomyoma share a spectrum of histologic findings and a perivascular growth pattern. In contrast, solitary fibrous tumor was once hypothesized to have pericytic differentiation--although little bona fide evidence of pericytic differentiation exists. Likewise the perivascular epithelioid cell tumor (PEComa) family shares a perivascular growth pattern, but with distinctive dual myoid-melanocytic differentiation. RGS5, regulator of G-protein signaling 5, is a novel pericyte antigen with increasing use in animal models. Here, we describe the immunohistochemical expression patterns of RGS5 across perivascular soft tissue tumors, including glomus tumor (n = 6), malignant glomus tumor (n = 4), myopericytoma (n = 3), angioleiomyoma (n = 9), myofibroma (n = 4), solitary fibrous tumor (n = 10), and PEComa (n = 19). Immunohistochemical staining and semi-quantification was performed, and compared to αSMA (smooth muscle actin) expression. Results showed that glomus tumor (including malignant glomus tumor), myopericytoma, and angioleiomyoma shared a similar diffuse immunoreactivity for RGS5 and αSMA across all tumors examined. In contrast, myofibroma, solitary fibrous tumor and PEComa showed predominantly focal to absent RGS5 immunoreactivity. These findings further support a common pericytic lineage of differentiation in glomus tumors, myopericytoma and angioleiomyoma. The pericyte marker RGS5 may be of future clinical utility for the evaluation of pericytic differentiation in soft tissue tumors.

The molecular aspects of chordoma.

Chordomas are one of the rarest bone tumors, and they originate from remnants of embryonic notochord along the spine, more frequently at the skull base and sacrum. Although they are relatively slow growing and low grade, chordomas are highly recurrent, aggressive, locally invasive, and prone to metastasize to the lungs, bone, and the liver. Chordomas highly and generally show a dual epithelial-mesenchymal differentiation. These tumors resist chemotherapy and radiotherapy; therefore, radical surgery and high-dose radiation are the most used treatments, although there is no standard way to treat the disease. The molecular biology process behind the initiation and progression of a chordoma needs to be revealed for a better understanding of the disease and to develop more effective therapies. Efforts to discover the mysteries of these molecular aspects have delineated several molecular and genetic alterations in this tumor. Here, we review and describe the emerging insights into the molecular landscape of chordomas.

Mutational analysis by next generation sequencing of gastric type dysplasia occurring in hyperplastic polyps of the stomach: Mutations in gastric hyperplastic polyps

Gastric hyperplastic polyps (GHP) are the most common type of polyps occurring in the stomach. Although GHP are broadly interpreted as benign lesions, they may progress to dysplasia and adenocarcinoma. Objective: In this study, we aimed to identify genomic mutations that characterize and may drive malignant transformation in GHP by using next-generation sequencing. Eight GHP (2 with dysplasia, 1 indefinite for dysplasia and 5 without dysplasia) were studied. Only large polyps (>1cm) with gastric differentiation were included in this study, while adenomatous polyps (intestinal-type) were excluded. Immunohistochemistry for MUC2, MUC5A, MUC6, CDX2, p53, and Ki67 was performed. DNA was extracted from formalin-fixed paraffin-embedded sections and sequenced for the detection of somatic mutations. Multiplex sequencing was done with the TrueSeq Amplicon Cancer Panel in the MiSeq platform. Variant annotation and visualization were performed using NextGENe (SoftGenetics) software. No pathogenic mutations were detected in GHP without dysplasia. TP53 gene mutations were the most common alteration in dysplastic GHP (2 of 2 dysplastic cases). PIK3CA mutation was identified in a GHP with pyloric-type dysplasia, whereas foveolar-type dysplasia carried TP53 mutations. In conclusion, TP53 gene mutations are a common alteration in the early dysplastic stage during malignant transformation of GHP. GHP with dysplasia may show dual differentiation. In our study, pyloric-type dysplasia was associated with a PIK3CA alteration whereas foveolar dysplasia carried TP53 mutations. The identification of carcinoma-associated mutations in large GHP provides additional evidence of their neoplastic potential and emphasizes the need for their complete resection and follow-up.

Combined cutaneous tumors with a melanoma component: A clinical, histologic, and molecular study

The histogenesis and clinical behavior of combined cutaneous tumors (CCTs) in which the mesenchymal component consists of melanoma remain unclear. We sought to characterize the clinical, histologic, and molecular findings in CCTs with an epithelial and a melanoma component. We retrospectively reviewed the records from 2 institutions for CCTs. Fluorescence in situ hybridization was performed to assess chromosomal copy number alterations in both components. Sixteen CCTs were included. The most common subtype was the squamomelanocytic tumor (11), followed by the basomelanocytic tumor (3) and the trichoblastomelanoma (2). CCTs were more common in men (87%), on the head and neck (57%), and had extensive solar elastosis (81%). The median follow-up was 25 months (range, 8-167 months). One case had an adverse outcome. Fluorescence in situ hybridization revealed chromosomal alterations in approximately 55% of the cases. Five cases showed chromosomal gains only in the melanocytic component. One case showed 11q13 gains in both the epithelial and melanocytic components. Our study is retrospective and the sample is small. The low incidence of adverse outcomes suggests that CCT may be more indolent than noncombined tumors. 11q13 amplification in both components supports the theory of dual differentiation from a common progenitor cell.

Evaluating Packed Red Blood Cell (RBC) Product Utilization on Hematologic Malignancy Service (HMS): A Quality Improvement Initiative

Dual differentiation therapy with arsenic trioxide and tretinoin (all-trans-retinoic acid; ATRA) has demonstrated non-inferiority compared to chemotherapy for low and intermediate risk acute promyelocytic leukemia. As clinical experience grows with this regimen, less commonly reported toxicities may begin to surface. At our center, we have treated ten patients thus far with dual differentiation therapy; five (50%) have developed pseudotumor cerebri (PTC). One of these 5 patients was managed with temporary discontinuation of ATRA and initiation of acetazolamide. In the remaining 4 patients, topiramate was substituted after acetazolamide failure, in order to relieve symptoms and permit ATRA dose re-escalation. All patients treated with this approach are in complete remission. Given our experience with dual differentiation therapy, we recommend close monitoring for signs and symptoms of PTC. In patients with inadequate symptom control with ATRA dose reduction and acetazolamide, topiramate should be considered.

Global transcriptome and chromatin occupancy analysis reveal the short isoform of GATA1 is deficient for erythroid specification and gene expression.

GATA1 is a master transcriptional regulator of the differentiation of several related myeloid blood cell types, including erythrocytes and megakaryocytes. Germ-line mutations that cause loss of full length GATA1, but allow for expression of the short isoform (GATA1s), are associated with defective erythropoiesis in a subset of patients with Diamond Blackfan Anemia. Despite extensive studies of GATA1s in megakaryopoiesis, the mechanism by which GATA1s fails to support normal erythropoiesis is not understood. In this study, we used global gene expression and chromatin occupancy analysis to compare the transcriptional activity of GATA1s to GATA1. We discovered that compared to GATA1, GATA1s is less able to activate the erythroid gene expression program and terminal differentiation in cells with dual erythroid-megakaryocytic differentiation potential. Moreover, we found that GATA1s bound to many of its erythroid-specific target genes less efficiently than full length GATA1. These results suggest that the impaired ability of GATA1s to promote erythropoiesis in DBA may be caused by failure to occupy erythroid-specific gene regulatory elements.

The effects of panaxadiol saponins on megakaryocytic maturation and immune function in a mouse model of immune thrombocytopenia

We have identified a biologically active component, panaxadiol saponins component (PDS-C), from Chinese ginseng herb extract. Panaxadiol saponins component contains five ginsenoside monomers with total purity of 92.44%. In this study, the BALB/c mouse model with immune thrombocytopenia (ITP) was established by injection of antiplatelet antibody every other day for 5 total times; the peripheral blood platelet counts steadily decreased to 20%-30% of normal levels and remained decreased for about 10 days. The antiplatelet antibody was derived from the sera of guinea pigs immunized with the platelets of BALB/c mice. Mice with ITP were treated with PDS-C at a low, a moderate, or a high dose for 10 consecutive days. We observed that the peripheral blood platelet counts of ITP mice were significantly higher than that of ITP controls (untreated) after treatment of PDS-C in a dose-dependent manner. Treatment with PDS-C also increased the mature megakaryocytes in the bone marrow of treated ITP animals with a concomitant decease of immature megakaryocyte precursors. Furthermore, macrophage phagocytosis of exogenous erythrocytes in the intra-abdominal cavity of ITP mice was inhibited by PDS-C treatment, indicating that PDS-C also could modulate immune function and may possibly prevent phagocytosis of antibody-coated platelets. Altogether, our findings suggest that PDS-C may have a dual role, promoting proliferation and differentiation of megakaryocytes, as well as modulating immune function, and it may therefore be very helpful in the treatment of ITP.

Sensitivity Analysis of a One-Dimensional SOFC Contaminant Degradation Model Using Dual Numbers Automatic Differentiation

Sensitivity analysis of a computational model with respect to a parameter is the derivative of the model outcome with respect to same parameter. In experimental studies, sensitivity of the experiment to the parameter is very crucial for the accuracy of the results. In this study, a one-dimensional contaminant performance degradation computational model for solid oxide fuel cells (SOFC) is utilized to study its sensitivity to changes in model parameters. Both finite difference (FD) method and dual numbers automatic differentiation (DNAD) are used to evaluate derivatives and compared to each other. The DNAD method uses dual number arithmetic to calculate the derivative of any mathematical functions or any numerical model with respect to a given parameter. Dual number arithmetic is a well-known strategy for automatic differentiation of computer codes which gives exact derivatives, to the machine accuracy, of the computed quantities with respect to any of the involved variables. The sensitivity to a model parameter calculated by DNAD is then verified and compared with finite differences. This technique can be used to evaluate the sensitivity of simulation results on changes in the critical parameters involved in the mathematical model. It is those parameters which have to be carefully calibrated and validated against experiments to confidence on predictions.

Early expressions of hypoxia-inducible factor 1alpha and vascular endothelial growth factor increase the neuronal plasticity of activated endogenous neural stem cells after focal cerebral ischemia.

Endogenous neural stem cells become “activated” after neuronal injury, but the activation sequence and fate of endogenous neural stem cells in focal cerebral ischemia model are little known. We evaluated the relationships between neural stem cells and hypoxia-inducible factor-1α and vascular endothelial growth factor expression in a photothromobotic rat stroke model using immunohistochemistry and western blot analysis. We also evaluated the chronological changes of neural stem cells by 5-bromo-2′-deoxyuridine (BrdU) incorporation. Hypoxia-inducible factor-1α expression was initially increased from 1 hour after ischemic injury, followed by vascular endothelial growth factor expression. Hypoxia-inducible factor-1α immunoreactivity was detected in the ipsilateral cortical neurons of the infarct core and peri-infarct area. Vascular endothelial growth factor immunoreactivity was detected in bilateral cortex, but ipsilateral cortex staining intensity and numbers were greater than the contralateral cortex. Vascular endothelial growth factor immunoreactive cells were easily found along the peri-infarct area 12 hours after focal cerebral ischemia. The expression of nestin increased throughout the microvasculature in the ischemic core and the peri-infarct area in all experimental rats after 24 hours of ischemic injury. Nestin immunoreactivity increased in the subventricular zone during 12 hours to 3 days, and prominently increased in the ipsilateral cortex between 3–7 days. Nestin-labeled cells showed dual differentiation with microvessels near the infarct core and reactive astrocytes in the peri-infarct area. BrdU-labeled cells were increased gradually from day 1 in the ipsilateral subventricular zone and cortex, and numerous BrdU-labeled cells were observed in the peri-infarct area and non-lesioned cortex at 3 days. BrdU-labeled cells rather than neurons, were mainly co-labeled with nestin and GFAP. Early expressions of hypoxia-inducible factor-1α and vascular endothelial growth factor after ischemia made up the microenvironment to increase the neuronal plasticity of activated endogenous neural stem cells. Moreover, neural precursor cells after large-scale cortical injury could be recruited from the cortex nearby infarct core and subventricular zone.

High pseudotumor cerebri incidence in tretinoin and arsenic treated acute promyelocytic leukemia and the role of topiramate after acetazolamide failure

Dual differentiation therapy with arsenic trioxide and tretinoin (all-trans-retinoic acid; ATRA) for the management of low and intermediate risk acute promyelocytic leukemia has recently been recommended by the National Comprehensive Cancer Network. Some less common toxicities of the combination may have yet to be fully realized. Of ten patients we have treated thus far, five (50%) have developed pseudotumor cerebri. In one patient, temporary discontinuation of ATRA and initiation of acetazolamide controlled symptoms. In four patients, topiramate was substituted for acetazolamide to relieve symptoms and allow ATRA dose re-escalation. We conclude that providers should monitor for pseudotumor cerebri and consider topiramate if acetazolamide fails.

Lung progenitors from lambs can differentiate into specialized alveolar or bronchiolar epithelial cells

BackgroundAirways progenitors may be involved in embryogenesis and lung repair. The characterization of these important populations may enable development of new therapeutics to treat acute or chronic lung disease. In this study, we aimed to establish the presence of bronchioloalveolar progenitors in ovine lungs and to characterize their potential to differentiate into specialized cells.ResultsLung cells were studied using immunohistochemistry on frozen sections of the lung. Immunocytochemistry and flow cytometry were conducted on ex-vivo derived pulmonary cells. The bronchioloalveolar progenitors were identified by their co-expression of CCSP, SP-C and CD34. A minor population of CD34pos/SP-Cpos/CCSPpos cells (0.33% ± 0.31) was present ex vivo in cell suspensions from dissociated lungs. Using CD34 magnetic positive-cell sorting, undifferentiated SP-Cpos/CCSPpos cells were purified (>80%) and maintained in culture. Using synthetic media and various extracellular matrices, SP-Cpos/CCSPpos cells differentiated into either club cells (formerly named Clara cells) or alveolar epithelial type-II cells. Furthermore, these ex vivo and in vitro derived bronchioloalveolar progenitors expressed NANOG, OCT4 and BMI1, specifically described in progenitors or stem cells, and during lung development.ConclusionsWe report for the first time in a large animal the existence of bronchioloalveolar progenitors with dual differentiation potential and the expression of specialized genes. These newly described cell population in sheep could be implicated in regeneration of the lung following lesions or in development of diseases such as cancers.

Twist1 is essential in maintaining mesenchymal state and tumor-initiating properties in synovial sarcoma

Synovial sarcoma is an aggressive mesenchymal tumor with dual differentiation; epithelial and mesenchymal differentiation. However, the molecular mechanisms behind tumorigenesis and dual differentiation have remained elusive. In this study, we investigated whether Twist1 is an essential transcription factor for maintaining tumor-initiating cell properties in synovial sarcoma. First, we identified that Twist1 is overexpressed in most cases of synovial sarcoma (SS) samples as well as in two synovial sarcoma cell lines (HSSYII, SW982). Additionally, Twist1 depletion led to down-regulation of mesenchymal markers and up-regulation of epithelial markers in SS cell lines. The migratory and invasive abilities of SS cell lines were also significantly reduced following the loss of Twist1. These results indicate that Twist1 plays an essential role in the maintenance of mesenchymal character in SS. Furthermore, knock-down of Twist1 induced G1 cycle arrest and apoptosis as well as remarkable reduction in the sphere-forming cell subpopulation and side population cells. Moreover, Twist1 knock-down profoundly inhibited the growth of synovial sarcoma xenograft in nude mice compared to controls indicating that Twist1 is essential for tumor initiating cell properties. To explore transcriptional regulation by Twist1 at the genomic level, Chromatin immunoprecipiation-solexa whole genome sequencing (ChIP-SEQ) and cDNA microarray analysis were performed. Mesenchymal differentiation/proliferation and PDGF related genes were found to be affected by Twist1. Finally, depletion of SS18-SSX fusion oncoprotein by RNA inference induced down-regulation of Twist1, implying that Twist1 is regulated by SS18-SSX. Hence, our results suggest that Twist1 is an essential transcription factor for the maintenance of mesenchymal characters and tumor initiating properties of synovial sarcoma.