Myoepithelial Tumors of Bone With EWSR1::PBX3 Fusion: A Spectrum From Benign to Malignant.

The EWSR1::PBX3 fusion gene, commonly associated with cutaneous syncytial myoepitheliomas, is also found in myoepithelial tumors (METs) of bone and soft tissue. These tumors typically demonstrate benign histology and favorable outcomes. This study examines 6 previously unreported intraosseous METs harboring the EWSR1::PBX3 fusion, focusing on their histopathologic characteristics, immunophenotype, clinical and radiographic profiles, and patient outcomes. The cohort comprised 5 men and 1 woman, aged 25 to 65 years (median age: 31 years), with tumors located in the proximal tibia (3 cases), distal radius (2 cases), and ilium (1 case) and sizes between 3.2 and 12.2 cm (median size: 3.9 cm). Imaging showed osteolytic lesions with varying degrees of cortical involvement and soft tissue extension in 3 cases. Histologically, 4 tumors showed mainly uniform oval-to-spindled cells in syncytial or fascicular arrangements within a collagenous matrix, displaying either bland nuclear features or mild atypia, and low to slightly elevated mitotic activity (≤1 per 10 high-power fields in 3 cases and 6 per 10 high-power fields in 1), classifying them as benign or atypical METs. In contrast, 2 tumors exhibited pronounced nuclear atypia with ovoid, spindled, epithelioid and round cells, hyperchromatic nuclei, inconspicuous nucleoli, increased N/C ratios, high mitotic rates (17 and 19 per 10 high-power fields), and extensive necrosis. Both tumors behaved aggressively-one patient underwent amputation after neoadjuvant chemotherapy and radiation, and the other died within 7 months with the disease still present. Immunohistochemically, the tumors consistently expressed epithelial membrane antigen and S100 but lacked keratin (AE1/AE3) expression. Our study demonstrated that bone METs with EWSR1::PBX3 fusions encompass a histologic continuum from benign to malignant, with benign/atypical METs mirroring their cutaneous analogs in morphology, and malignant variants distinguished by heterogeneous cytologic and architectural features, pronounced nuclear atypia, and high mitotic rates.

Inhibition of ERN1 affects the expression of TGIF1 and other homeobox gene expressions in U87MG glioblastoma cells.

BACKGROUND: The ERN1 (endoplasmic reticulum to nucleus signaling 1) pathway plays an important role in the regulation of gene expression in glioblastoma, but molecular mechanism has not yet been fully elucidated. The aim of this study was to evaluate the relative relevance of ERN1 activity as a kinase in comparison to its endoribonuclease activity in the regulation of homeobox gene expression. METHODS: Two sublines of U87MG glioblastoma cells with different ways of ERN1 inhibition were used: dnERN1 (overexpressed transgene without protein kinase and endoribonuclease) and dnrERN1 (overexpressed transgene with mutation in endoribonuclease). ERN1 suppression was also done using siRNA for ERN1. Silencing of XBP1 mRNA by specific siRNA was used for suppression of ERN1 endoribonuclease function mediated by XBP1s. The expression levels of homeobox genes and microRNAs were evaluated by qPCR. RESULTS: The expression of TGIF1 and ZEB2 genes was downregulated in both types of glioblastoma cells with inhibition of ERN1 showing the ERN1 endoribonuclease-dependent mechanism of their regulation. However, the expression of PBX3 and PRPRX1 genes did not change significantly in dnrERN1 glioblastoma cells but was upregulated in dnERN1 cells indicating the dependence of these gene expressions on the ERN1 protein kinase. At the same time, the changes in PAX6 and PBXIP1 gene expressions introduced in glioblastoma cells by dnrERN1 and dnERN1 were different in direction and magnitude indicating the interaction of ERN1 protein kinase and endoribonuclease activities in regulation of these gene expressions. The impact of ERN1 and XBP1 silencing on the expression of studied homeobox genes is similar to that observed in dnERN1 and dnrERN1 glioblastoma cells, correspondingly. CONCLUSION: The expression of TGIF1 and other homeobox genes is dependent on the ern1 signaling pathways by diverse mechanisms because inhibition of ERN1 endoribonuclease and both ERN1 enzymatic activities had dissimilar impacts on the expression of most studied genes showing that ERN1 protein kinase plays an important role in controlling homeobox gene expression associated with glioblastoma cell invasion.

An intraosseous myoepithelial carcinoma with a EWSR1::PBX3 fusion.

Herein we report a case of an intraosseous myoepithelial carcinoma harboring a EWSR1::PBX3 fusion gene. The patient was a 64-year-old male found to have a 7 cm destructive lesion in the distal ulna with an extraosseous soft tissue component. Microscopic examination of the resected tumor showed a spindle-cell lesion within a sclerotic stroma and intravascular tumor emboli. At higher power the tumor cells showed moderate nuclear atypia with a high mitotic count (20 per mm2 ). Immunohistochemistry revealed diffuse EMA positivity and focal pancytokeratin (AE1/AE3) and S100 expression, consistent with myoepithelial differentiation. NGS using the Oncomine Childhood Cancer Assay (Thermo Fisher Scientific, Inc.) revealed a EWSR1-PBX3 fusion and ABL amplification. The patient subsequently developed local recurrence as well as distant lymph node, lung and vertebral metastases; he is currently awaiting systemic treatment in the context of a clinical trial. In this report, we present a rare case of a skeletal myoepithelial tumor harboring a EWSR1::PBX3 fusion with demonstrated histological and clinical features of malignancy.

Exosomal circKIAA1797 Regulates Cell Progression and Glycolysis by Targeting miR-4429/PBX3 Pathway in Gastric Cancer.

In recent years, circular RNAs (circRNAs) are extensively studied in the progression of various types of cancer, while the mechanism of circKIAA1797 is rarely studied in gastric cancer (GC). Hence, this research aimed to investigate the expression of exosomal circKIAA1797 and its biological function in GC cells. Exosomes were extracted from the serum of GC patients and identified by transmission electron microscopy (TEM) and nanoparticle tracking analyzer (NTA). CD81, CD63, Bcl-2, Bax, and pre-leukemia transcription factor 3 (PBX3) protein levels were detected using western blot assay. circKIAA1797, microRNA-4429 (miR-4429), and PBX3 mRNA were determined by quantitative real-time PCR (RT-qPCR). Cell proliferation, migration, invasion, and apoptosis were assessed using colony formation assay, 5-Ethynyl-2'-deoxyuridine (EdU) assay, transwell assay, and flow cytometry assay. Glucose consumption and lactate production levels were examined using glycolysis detection kits. The interaction between miR-4429 and circKIAA1797 or PBX3 was identified using dual-luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation (RIP) assay. Xenograft mouse model assay was used to investigate the effect of exosomal circKIAA1797 in vivo. It was found that circKIAA1797 was up-regulated in GC tissues and cells, as well as in the exosomes derived from the serum of GC patients. Silencing of exosomal circKIAA1797 could hamper cell progression and glycolytic metabolism of GC. Mechanically, circKIAA1797 acted as a sponge of miR-4429 to regulate PBX3 expression. Moreover, the knockdown of exosomal circKIAA1797 repressed tumor growth in vivo. Our data demonstrated that knockdown of exosomal circKIAA1797 suppressed GC malignant phenotypes by regulating miR-4429/PBX3 axis, which might offer a promising therapeutic strategy for GC treatment.

Long noncoding RNA-LINC00478 promotes the progression of clear cell renal cell carcinoma through PBX3.

Long noncoding RNAs play an important regulatory role in the development and progression of tumors. Our study found that LINC00478 was upregulated in clear cell renal cell carcinoma (ccRCC), so we made an in-depth exploration into its mechanism. In Caki-2 cells, we established the oe-LINC00478 cell line overexpressing LINC00478, and established underexpressing sh-LINC00478 cell line by short hairpin RNA silencing. The abilities of oe-LINC00478 cell invasion and metastasis were significantly enhanced, and the cell proliferative potential was also improved. The cellular expressions of PBX3, CDCA8, and CDK2 were upregulated, while in the sh-LINC00478 cells, the proliferative potential and metastatic and invasive abilities were weakened. Similarly, we established the PBX3-overexpressing oe-PBX3 cell line and the PBX3-underexpressing sh-PBX3 cell line, finding that the PBX3 overexpression enhanced the metastatic and invasive abilities of Caki-2 cells. When we overexpressed LINC00478 in PBX3-knockout Caki-2-PBX3- / - cells, no significant changes were noted in the metastatic or invasive ability. Through RNA pull-down and RNA-binding protein immunoprecipitation assays, we found that LINC00478 could facilitate the transcription-translation processes of PBX3 by binding to it, thus further promoting the expression of downstream cyclins to exert its action. In animal experimentation, the oe-LINC00478 and sh-LINC00478 Caki-2 cells were separately seeded, revealing that the tumor volume was significantly larger in the oe-LINC00478 group than in the sh-LINC00478 group. This study finds that by promoting the PBX3 transcription, LINC00478 can further regulate the expressions of downstream cyclins, thereby facilitating the metastasis and invasion of ccRCC.

A case of cutaneous syncytial myoepithelioma with extensive adipocytic metaplasia: Usefulness of EWSR1-PBX3 gene fusion analysis.

Cutaneous syncytial myoepithelioma (CSM) is a recently recognized variant of myoepithelioma characterized by an intradermal syncytial proliferation of spindled, ovoid, and histiocytoid cells. Immunohistochemically, tumor cells usually show strong expression of S-100 protein and epithelial membrane antigen (EMA). Here we report a case of CSM in the thigh of a 51-year-old Japanese woman. Histopathological findings showed a sheet-like growth of ovoid cells and histiocytoid cells with an eosinophilic syncytial cytoplasm, and adipocytic metaplasia was widely observed in the tumor. Immunohistochemical staining revealed a diffuse, strong pattern for EMA, smooth muscle actin (SMA), and HHF35, and variable expression of S-100 protein and p63 in ovoid and histiocytoid cells without significant mitotic figures or pleomorphism. In addition, EWSR1-PBX3 gene fusion, which is characteristic of CSM, was observed in the tumor. Based on these findings, we diagnosed the patient as having CSM. Our case shows that CSM can exhibit extensive adipocytic metaplasia, which could make its histopathological diagnosis challenging.

Knockdown of hsa_circ_0043691 restrains the progression of gastric cancer by decoying miR-1294 to target pre-leukemia transcription factor 3.

BACKGROUND: Circular RNAs (circRNAs) have been found to render pivotal effects in gastric cancer (GC). However, the effect of hsa_circ_0043691 in GC still needs to be further unveiled. METHODS: The contents of hsa_circ_0043691, miR-1294, and pre-leukemia transcription factor 3 (PBX3) were examined using qRT-PCR or Western blot assay. In vitro colony formation, transwell, wound healing, flow cytometry, tube formation assays, glutaminolysis corresponding kit and in vivo Xenograft mice model were utilized to evaluate cell functions. The relationship between miR-1294 and hsa_circ_0043691 or PBX3 was further verified. RESULTS: The levels of hsa_circ_0043691 and PBX3 were upregulated, whereas miR-1294 expression was diminished in GC tissues and cells. Hsa_circ_0043691 deficiency significantly inhibited GC cell progression and glutaminolysis metabolism. Mechanistically, hsa_circ_0043691 was directly bound to miR-1294 to modulate PBX3 expression. Besides, silencing of hsa_circ_0043691 impeded tumor growth in vivo. CONCLUSION: Hsa_circ_0043691 knockdown repressed GC malignant phenotypes by miR-1294/PBX3 axis, which exhibited a novel therapeutic target for GC treatment.

Circular RNA circHECTD1 prevents Diosbulbin-B-sensitivity via miR-137/PBX3 axis in gastric cancer.

BACKGROUNDS: Gastric cancer (GC) is general disease in human digestive system with malignancy. Emerging findings indicated that hsa_circ_0031452 (circHECTD1) was strictly associated with carcinogenesis. Nevertheless, the role of circHECTD1 in drug-resistance still needed to be explained. METHODS: Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to examine the expression profiles of circHECTD1, microRNA (miR)-137, and pre-leukemia transcription factor 3 (PBX3). The function of circHECTD1 in tumorigenesis was evaluated via xenograft tumor model. The IC50 of Diosbulbin-B (DB) was detected using Cell Counting Kit-8 (CCK8). Cell-cycle and apoptosis were reckoned by flow cytometry. Besides, western blot was administrated to reckon the levels of PBX3 and cell apoptotic indicators. Moreover, the interrelation between miR-137 and circHECTD1 or PBX3 was expounded by dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull down assays. RESULTS: We uncovered that circHECTD1 was ectopically up-regulated in GC tissues and cells. CircHECTD1 deficiency sensitized DB-treatment in DB-evoked AGS and HGC-27 cells. In vivo assay, circHECTD1 silencing led to the tumor reduction. Also, circHECTD1 served as miR-137 sponge in a sequence-complementary manner. Furthermore, transfection of miR-137 inhibitor markedly eliminated circHECTD1 absence-mediated promotion of DB-sensitivity in GC cells. Moreover, PBX3, a target of miR-137, play a DB-resistant role in GC cells. Fascinatingly, the deletion of PBX3 reversed the impact of miR-137 repression and circHECTD1 knockdown on DB-sensitivity in vitro. CONCLUSIONS: CircHECTD1 served as an oncogene by a novel miR-137/PBX3 axis, which might supply an underlying biomarker for the diagnosis and prognosis of GC management.

LncRNA H19 suppresses pyroptosis of cardiomyocytes to attenuate myocardial infarction in a PBX3/CYP1B1-dependent manner.

OBJECTIVE: Myocardial infarction (MI) is a major cause of cardiovascular disease which poses great healthy and financial burden for individuals. MI can be mainly induced by hypoxia. Therefore, in this study, we aimed to explore the function and mechanism of lncRNA H19 on hypoxia-induced pyroptosis of cardiomyocytes. METHOD: Peripheral blood from healthy controls and MI patients was collected for determination of mRNA and protein expression levels of H19 and CYP1B1. The correlation between these two factors was analyzed. Then MI rat model was established and injected with H19 overexpression/CYP1B1 knockdown plasmid, in which the infraction area and pathological morphology were observed. Hypoxic cardiomyocytes were transfected with overexpression or knockdown of H19 and CYP1B1 for determination of NLRP3, ASC, caspase-1, IL-1ß, IL-18, CyclinD1, and PCNA. Cell proliferation ability was assessed by CCK8. RIP and dual luciferase gene reporter assay were applied to verify the binding among H19, PBX3 and CYP1B1. RESULTS: Downregulated H19 and upregulated CYP1B1 were observed in MI patients. A negative correlation was found for H19 and CYP1B1 expressions. Transfection of H19 overexpression or CYP1B1 knockdown could attenuate the MI progression in MI rats. In hypoxic cardiomyocytes, H19 overexpression or CYP1B1 knockdown could also inhibit NLRP3, ASC, caspase-1, IL-1ß, and IL-18 in addition to suppressing cell apoptosis rate and promoting cell proliferation rate. Different expression pattern was found in cells transfected with H19 knockdown or CYP1B1 overexpression. Overexpression of CYP1B1 could abrogate the suppressive effect of H19 on pyroptosis of cardiomyocytes. H19 could inhibit activity of CYP1B1 promoters by regulating PBX3. CONCLUSION: H19 could inhibit CYP1B1 expression in a PBX3-dependent way and thus attenuate cell pyroptosis of cardiomyocytes.

Long non-coding RNA HNF1A-AS1 upregulates OTX1 to enhance angiogenesis in colon cancer via the binding of transcription factor PBX3.

Colon cancer shows characteristics of metastasis, which is associated with angiogenesis. Increasing evidence highlights long non-coding RNAs (lncRNAs) as important participants in angiogenesis of cancers, including colon cancer. Hence, this study investigated the role of HNF1A-AS1 in angiogenesis of colon cancer. RT-qPCR and Western blot analysis were applied to detect HNF1A-AS1 and OTX1 expression in colon cancer tissues and cell lines. Then the interactions among HNF1A-AS1, PBX3, OTX1 and ERK/MAPK pathway were evaluated with RNA pull-down, RIP, ChIP and dual-luciferase reporter gene assays. Next, HCT116 and SW620 cells were treated with si-HNF1A-AS1 and/or oe-OTX1 plasmids to assess the effects of HNF1A-AS1 and OTX1 on angiogenesis, which was further evaluated in nude mice injected with SW620 cells transfected with sh-HNF1A-AS1 or sh-OTX1 lentivirus. HNF1A-AS1 and OTX1 were highly expressed in colon cancer. Silencing of HNF1A-AS1 inhibited angiogenesis of colon cancer in vivo and in vitro. HNF1A-AS1 increased the OTX1 expression by binding to transcription factor PBX3 to promote angiogenesis in colon cancer. Further, HNF1A-AS1 upregulated OTX1 to activate the ERK/MAPK pathway. Altogether, our findings identified HNF1A-AS1 as a tumor-promoting RNA in colon cancer, which could serve as a potential therapeutic target for colon cancer treatment.

The transcription factor PBX3 promotes tumor cell growth through transcriptional suppression of the tumor suppressor p53.

Pre-B-cell leukemia transcription factor 3 (PBX3) is a member of the PBX family and contains a highly conserved homologous domain. PBX3 is involved in the progression of gastric cancer, colorectal cancer, and prostate cancer; however, the detailed mechanism by which it promotes tumor growth remains to be elucidated. Here, we found that PBX3 silencing induces the expression of the cell cycle regulator p21, leading to an increase in colorectal cancer (CRC) cell apoptosis as well as suppression of proliferation and colony formation. Furthermore, we found that PBX3 is highly expressed in clinical CRC patients, in whom p21 expression is aberrantly low. We found that the regulation of p21 transcription by PBX3 occurs through the upstream regulator of p21, the tumor suppressor p53, as PBX3 binds to the p53 promoter and suppresses its transcriptional activity. Finally, we revealed that PBX3 regulates tumor growth through regulation of the p53/p21 axis. Taken together, our results not only describe a novel mechanism regarding PBX3-mediated regulation of tumor growth but also provide new insights into the regulatory mechanism of the tumor suppressor p53.

SNHG10/DDX54/PBX3 Feedback Loop Contributes to Gastric Cancer Cell Growth.

BACKGROUND: The importance of long noncoding RNAs (lncRNAs) has been identified in human cancers, such as emerged as tumor facilitator or tumor suppressor. Small nucleolar RNA host gene 10 (SNHG10) has been reported as an oncogenic lncRNA in hepatocellular carcinoma. However, its functional role and underlying mechanism in gastric cancer (GC) need to be further explored. AIMS: Our study was conducted to investigate the function and molecular mechanism of SNHG10 in GC. METHODS: SNHG10 expression was detected by qRT-PCR. The effect of SNHG10 on GC cell growth was assessed by colony formation, EdU, JC-1, flow cytometry, and wound-healing assays. The interaction between SNHG10 and PBX3 was confirmed through ChIP and luciferase reporter assay. RIP and RNA pull down assays was used to define the binding of DEAD-box helicase 54 (DDX54) to SNHG10 or PBX homeobox 3 (PBX3). RESULTS: SNHG10 was expressed at a high level in GC cells. SNHG10 knockdown resulted in the inhibition on GC cell proliferation, migration but induced cell apoptosis. PBX3 could interact with SNHG10 promoter and thereby activate the expression of SNHG10. Subsequently, it was confirmed that SNHG10 positively modulated the expression of PBX3. Based on this, we found that DDX54 could bind to SNHG10 and PBX3, suggesting that SNHG10 maintained PBX3 mRNA stability through recruiting DDX54. Restoration assays indicated that PBX3 overexpression recovered SNHG10 silencing-induced inhibition on GC cell growth. CONCLUSIONS: SNHG10 facilitates cell growth by affecting DDX54-mediated PBX3 mRNA stability in GC.

A morphologic and molecular reappraisal of myoepithelial tumors of soft tissue, bone, and viscera with EWSR1 and FUS gene rearrangements.

Myoepithelial tumors (MET) represent a clinicopathologically heterogeneous group of tumors, ranging from benign to highly aggressive lesions. Although MET arising in soft tissue, bone, or viscera share morphologic and immunophenotypic overlap with their salivary gland and cutaneous counterparts, there is still controversy regarding their genetic relationship. Half of MET of soft tissue and bone harbor EWSR1 or FUS related fusions, while MET arising in the salivary gland and skin often show PLAG1 and HMGA2 gene rearrangements. Regardless of the site of origin, the gold standard in diagnosing a MET relies on demonstrating its "myoepithelial immunophenotype" of positivity for EMA/CK and S100 protein or GFAP. However, the morphologic spectrum of MET in soft tissue and bone is quite broad and the above immunoprofile is nonspecific, being shared by other pathogenetically unrelated neoplasms. Moreover, rare MET lack a diagnostic immunoprofile but shows instead the characteristic gene fusions. In this study, we analyzed a large cohort of 66 MET with EWSR1 and FUS gene rearrangements spanning various clinical presentations, to better define their morphologic spectrum and establish relevant pathologic-molecular correlations. Genetic analysis was carried out by FISH for EWSR1/FUS rearrangements and potential partners, and/or by targeted RNA sequencing. Then, 82% showed EWSR1 rearrangement, while 18% had FUS abnormalities. EWSR1-POU5F1 occurred with predilection in malignant MET in children and young adults and these tumors had nested epithelioid morphology and clear cytoplasm. In contrast, EWSR1/FUS-PBX1/3 fusions were associated with benign and sclerotic spindle cell morphology. Tumors with EWSR1-KLF17 showed chordoma-like morphology. Our results demonstrate striking morphologic-molecular correlations in MET of bone, soft tissue and viscera, which might have implications in their clinical behavior.

Circular RNA circCORO1C promotes laryngeal squamous cell carcinoma progression by modulating the let-7c-5p/PBX3 axis.

BACKGROUND: Laryngeal squamous cell carcinoma (LSCC) is a common malignant tumor of the head and neck. LSCC patients have seriously impaired vocal, respiratory, and swallowing functions with poor prognosis. Circular RNA (circRNA) has attracted great attention in cancer research. However, the expression patterns and roles of circRNAs in LSCC remain largely unknown. METHODS: RNA sequencing was performed on 57 pairs of LSCC and matched adjacent normal mucosa tissues to construct circRNA, miRNA, and mRNA expression profiles. RT-PCR, qPCR, Sanger sequencing, and FISH were undertaken to study the expression, localization, and clinical significance of circCORO1C in LSCC tissues and cells. The functions of circCORO1C in LSCC were investigated by RNAi-mediated knockdown, proliferation analysis, EdU staining, colony formation assay, Transwell assay, and apoptosis analysis. The regulatory mechanisms among circCORO1C, let-7c-5p, and PBX3 were investigated by luciferase assay, RNA immunoprecipitation, western blotting, and immunohistochemistry. RESULTS: circCORO1C was highly expressed in LSCC tissues and cells, and this high expression was closely associated with the malignant progression and poor prognosis of LSCC. Knockdown of circCORO1C inhibited the proliferation, migration, invasion, and in vivo tumorigenesis of LSCC cells. Mechanistic studies revealed that circCORO1C competitively bound to let-7c-5p and prevented it from decreasing the level of PBX3, which promoted the epithelial-mesenchymal transition and finally facilitated the malignant progression of LSCC. CONCLUSIONS: circCORO1C has an oncogenic role in LSCC progression and may serve as a novel target for LSCC therapy. circCORO1C expression has the potential to serve as a novel diagnostic and prognostic biomarker for LSCC detection.

By downregulating PBX3, miR-526b suppresses the epithelial-mesenchymal transition process in cervical cancer cells.

Aim: Research on novel mutant genes may develop the treatment of cervical cancer (CC). The role of miRNA-526b in epithelial-mesenchymal transition (EMT) of CC was investigated. Methods: The role and the molecular mechanism of miRNA-526b in CC and its effect on EMT were analyzed in clinical specimens and oncology experiments. Results: miRNA-526b was proved to be decreased in CC and associated with malignant clinicopathological characters. The character of miRNA-526b in EMT was also inspected in CC cells and tumor models. miRNA-526b was found to be able to inhibit the EMT property of CC cells by directly targeting PBX3. Conclusion: miRNA-526b restoration may be deliberated as a new treatment strategy of CC.

EWSR1-PBX3 gene fusion in cutaneous syncytial myoepithelioma.

Cutaneous syncytial myoepithelioma (CSM) is a recently recognized, histopathological variant of myoepithelial (ME) tumors of the skin. It is characterized by a syncytial arrangement of spindled, ovoid, and/or epithelioid cells forming a well-circumscribed, unencapsulated dermal nodule. There is a paucity of intervening stroma, and absent duct or gland formation. Strong immunohistochemical staining for S100 and epithelial membrane antigen (EMA) has been described, while cytokeratin expression has been uncommon. The majority of CSMs harbor a rearrangement involving the EWSR1 gene. Although various fusion partner genes have been discovered in ME tumors at other anatomic sites, none has yet been described in CSM. We present a case of CSM represented clinically by a papule on the mid-upper back of a healthy 44-year-old female. It exhibited morphological and immunohistochemical features of a CSM with strong, diffuse S100 and alpha-actin expression, and focal positivity for EMA and cytokeratin AE1/AE3. Fluorescence in-situ hybridization showed an EWSR1 gene rearrangement. Massively parallel next-generation RNA sequencing revealed PBX3 as the fusion partner. The EWSR1-PBX3 gene fusion has been previously identified in three cases of ME tumors of bone and soft tissue, and in a case of retroperitoneal leiomyoma. This is the first report of an EWSR1-PBX3 fusion in CSM.

EWSR1-PBX3 fused myoepithelioma arising in metatarsal bone: Case report and review of the literature.

Intraosseous myoepithelial tumors are very rare. Due to the low incidence and diverse histologic features, accurate diagnosis is challenging, necessitating ancillary immunohistochemistry. Moreover, genetic abnormality in this tumor was not revealed until recently. Although EWSR1 translocation is involved in half of the cases of intraosseous myoepithelioma, only a few cases have indicated its counterpart gene. We herein describe a case of intraosseous myoepithelioma with a novel localization in the fourth metatarsal bone of a 36-year-old female. Cytogenetic analysis using next generation sequencing detected a rare EWSR1-PBX3 fusion. Next generation sequencing could be useful in understanding the cytogenetic characteristics of intraosseous myoepithelioma, and in obtaining an accurate diagnosis of this rare condition.

miR-129-5p suppresses proliferation, migration, and induces apoptosis in pancreatic cancer cells by targeting PBX3.

Pancreatic cancer (PC) is the seventh most frequent cause of cancer-related deaths worldwide with a high mortality. MicroRNAs (miRNAs) act as important regulators for the development of PC and participate in the progression of PC. miR-129-5p was reported to regulate the progression of tumors, such as thyroid cancer and gastric cancer. However, the function of miR-129-5p in PC is still unclear. In this study, the down-regulation of miR-129-5p was detected in PC tissues and PC cells. miR-129-5p was overexpressed or knocked down in AsPC-1 and BxPC-3 cells. The results showed that miR-129-5p overexpression suppressed proliferation, migration and invasion, and induced apoptosis of PC cells, whereas miR-129-5p knockdown showed opposite effects. In addition, we found that pre-B-cell leukemia homeobox 3 (PBX3) overexpression promoted proliferation, migration and invasion, but reduced apoptosis of PC cells. PBX3 was identified as a target of miR-129-5p by informatics analysis and dual luciferase reporter assay. Finally, our results indicated that miR-129-5p suppressed cell proliferation and migration by targeting PBX3. This study demonstrated that miR-129-5p could function as a tumor suppressor in the progression and development of PC by targeting PBX3, providing a reliable prognostic factor and a new therapeutic strategy for PC.

PBX3 is essential for leukemia stem cell maintenance in MLL-rearranged leukemia.

Interaction of HOXA9/MEIS1/PBX3 is responsible for hematopoietic system transformation in MLL-rearranged (MLL-r) leukemia. Of these genes, HOXA9 has been shown to be critical for leukemia cell survival, while MEIS1 has been identified as an essential regulator for leukemia stem cell (LSC) maintenance. Although significantly high expression of PBX3 was observed in clinical acute myeloid leukemia (AML) samples, the individual role of PBX3 in leukemia development is still largely unknown. In this study, we explored the specific role of PBX3 and its associated regulatory network in leukemia progression. By analyzing the clinical database, we found that the high expression of PBX3 is significantly correlated with a poor prognosis in AML patients. ChIP-Seq/qPCR analysis in MLL-r mouse models revealed aberrant epigenetic modifications with increased H3K79me2, and decreased H3K9me3 and H3K27me3 levels in LSCs, which may account for the high expression levels of Pbx3. To further examine the role of Pbx3 in AML maintenance and progression, we used the CRISPR/Cas9 system to delete Pbx3 in leukemic cells in the MLL-AF9 induced AML mouse model. We found that Pbx3 deletion significantly prolonged the survival of leukemic mice and decreased the leukemia burden by decreasing the capacity of LSCs and promoting LSC apoptosis. In conclusion, we found that PBX3 is epigenetically aberrant in the LSCs of MLL-r AML and is essential for leukemia development. Significantly, the differential expression of PBX3 in normal and malignant hematopoietic cells suggests PBX3 as a potential prognostic marker and therapeutic target for MLL-r leukemia.

MicroRNA-144-3p suppresses gastric cancer progression by inhibiting epithelial-to-mesenchymal transition through targeting PBX3.

MicroRNAs are aberrantly expressed in a wide variety of human cancers. The present study aims to elucidate the effects and molecular mechanisms of miR-144-3p that underlie gastric cancer (GC) development. It was observed that miR-144-3p expression was significantly decreased in GC tissues compared to that in paired non-tumor tissues; moreover, its expression was lower in tissues of advanced stage and larger tumor size, as well as in lymph node metastasis tissues compared to that in control groups. miR-144-3p expression was associated with depth of invasion (P = 0.030), tumor size (P = 0.047), lymph node metastasis (P = 0.047), and TNM stage (P = 0.048). Additionally, miR-144-3p significantly inhibited proliferation, migration, and invasion in GC cells. It also reduced F-actin expression and suppressed epithelial-to-mesenchymal transition (EMT) in GC cells. Furthermore, pre-leukemia transcription factor 3 (PBX3) was a direct target gene of miR-144-3p. PBX3 was overexpressed in GC tissues and promoted EMT in GC cells. The effects of miR-144-3p mimics or inhibitors on cell migration, invasion, and proliferation were reversed by PBX3 overexpression or downregulation respectively. These results suggest that miR-144-3p suppresses GC progression by inhibiting EMT through targeting PBX3.