Mect1-Maml2 fusion oncogene linked to the aberrant activation of cyclic AMP/CREB regulated genes

Long read sequencing identifies complex structural variant landscape and recurrent TERT rearrangements in mucoepidermoid carcinoma

Mucoepidermoid Carcinoma (MEC) is a common salivary malignant neoplasm. Approximately 60 % of MECs harbor translocations between CRTC1 or CRTC3 and MAML2, which are thought to drive disease pathogenesis. However, the precise structural mechanism driving this rearrangement remains uncharacterized. Here, we performed multi-omic and long read genomic sequencing, discovering a chain of alterations that created the CRTC1::MAML2 fusion, but also an unexpected MAML2 to MYBL1 rearrangement, suggesting that MYBL1 may play a larger role in salivary gland cancers than previously recognized. Furthermore, we discovered and validated recurrent TERT rearrangements and amplifications in MEC models. 5/5 MEC cell lines and 36/39 (92 %) primary MEC tumors harbored a TERT rearrangement or copy number amplification. Custom sequencing of the TERT locus confirmed translocation breakpoints in 13/33 (39 %) MECs, while exome sequencing confirmed frequent TERT amplifications. Critically, TERT knockdown in NCI-H292, a cell line with TERT promoter rearrangement, reduced clonogenic cell survival, supporting a critical role of this gene in MEC tumorigenesis. Overall, our data suggest that complex chromothripsis rearrangement mechanisms drive the formation of structural variation in CRTC1::MAML2 fusion positive and negative tumors and reveal highly recurrent structural variation driving TERT rearrangement in MEC.

Systemic therapies for salivary gland carcinoma (excluding adenoid cystic carcinoma): REFCOR recommendations by the formal consensus method

OBJECTIVE

To determine the therapeutic indications for systemic medical treatment in the management of salivary gland carcinoma (excluding adenoid cystic carcinoma) according to the clinical situation.

MATERIALS AND METHODS

The French Network of Rare Head and Neck Tumors (REFCOR) formed a steering group who drafted a narrative review of the literature published on Medline and proposed recommendations. The level of adherence to the recommendations was then assessed by a rating group, according to the formal consensus method.

RESULTS

Salivary gland carcinoma is rare and there is currently insufficient evidence to indicate chemotherapy at the localized stage. At the metastatic stage, initial management can be based on a phase of monitoring for indolent disease. Some histological subtypes (salivary duct carcinoma and adenocarcinoma) are more aggressive and require systemic treatment from the outset. To guide systemic treatment, it is recommended to perform immunohistochemistry and molecular biology analyses (overexpression of HER2 and androgen receptors, NTRK fusion, next-generation sequencing).

CONCLUSION

Salivary gland carcinoma is a rare tumor for which there are currently few effective medical treatments. It is therefore recommended to include patients in clinical trials.

Current diagnosis and treatment of salivary gland-type tumors of the lung

Salivary gland-type tumors of the lung are thought to originate from the submucosal exocrine glands of the large airways. Due to their rare occurrence, reports of their study are limited to small-scale or case reports. Therefore, daily clinical practices often require a search for previous reports. In the last 20 years, several genetic rearrangements have been identified, such as MYB::NF1B rearrangements in adenoid cystic carcinoma, CRTC1::MAML2 rearrangements in mucoepidermoid carcinoma, EWSR1::ATF1 rearrangements in hyalinizing clear cell carcinoma and rearrangements of the EWSR1 locus or FUS (TLS) locus in myoepithelioma and myoepithelial carcinoma. These molecular alterations have been useful in diagnosing these tumors, although they have not yet been linked to molecularly targeted therapies. The morphologic, immunophenotypic, and molecular characteristics of these tumors are similar to those of their counterparts of extrapulmonary origin, so clinical and radiologic differential diagnosis is required to distinguish between primary and metastatic disease of other primary sites. However, these molecular alterations can be useful in differentiating them from other primary lung cancer histologic types. The management of these tumors requires broad knowledge of the latest diagnostics, surgery, radiotherapy, bronchoscopic interventions, chemotherapy, immunotherapy as well as therapeutic agents in development, including molecularly targeted agents. This review provides a comprehensive overview of the current diagnosis and treatment of pulmonary salivary gland tumors, with a focus on adenoid cystic carcinoma and mucoepidermoid carcinoma, which are the two most common subtypes.

p53 Inhibits Bmi-1-driven Self-Renewal and Defines Salivary Gland Cancer Stemness

PURPOSE

Mucoepidermoid carcinoma (MEC) is a poorly understood salivary gland malignancy with limited therapeutic options. Cancer stem cells (CSC) are considered drivers of cancer progression by mediating tumor recurrence and metastasis. We have shown that clinically relevant small molecule inhibitors of MDM2-p53 interaction activate p53 signaling and reduce the fraction of CSC in MEC. Here we examined the functional role of p53 in the plasticity and self-renewal of MEC CSC.

EXPERIMENTAL DESIGN

Using gene silencing and therapeutic activation of p53, we analyzed the cell-cycle profiles and apoptosis levels of CSCs in MEC cell lines (UM-HMC-1, -3A, -3B) via flow cytometry and looked at the effects on survival/self-renewal of the CSCs through sphere assays. We evaluated the effect of p53 on tumor development (N = 51) and disease recurrence (N = 17) using in vivo subcutaneous and orthotopic murine models of MEC. Recurrence was followed for 250 days after tumor resection.

RESULTS

Although p53 activation does not induce MEC CSC apoptosis, it reduces stemness properties such as self-renewal by regulating Bmi-1 expression and driving CSC towards differentiation. In contrast, downregulation of p53 causes expansion of the CSC population while promoting tumor growth. Remarkably, therapeutic activation of p53 prevented CSC-mediated tumor recurrence in preclinical trials.

CONCLUSIONS

Collectively, these results demonstrate that p53 defines the stemness of MEC and suggest that therapeutic activation of p53 might have clinical utility in patients with salivary gland MEC.

Thymic Mucoepidermoid Carcinoma: A Clinicopathologic and Molecular Study

Thymic mucoepidermoid carcinoma (MEC) is a rare tumor, and its characteristics remain to be clarified. Here we investigated 20 cases of thymic MEC to systematically characterize its clinical, histopathologic, and molecular features. The median age of the patients was 56 years (range, 19 to 80 y), there was a slight male predilection (3:2), and 44% of the patients were asymptomatic at diagnosis. The median tumor size was 6.8 cm in diameter, 55% were pT1 tumors, and 50% were TNM stage I tumors. When 4 tumor grading systems for salivary MEC (Armed Forces Institutes of Pathology, Brandwein, modified Healey, and the Memorial Sloan-Kettering) were employed, low-grade, intermediate-grade, and high-grade tumors accounted for 35% to 70%, 5% to 25%, and 25% to 50%, respectively. Many histologic variants were noted, and 70% of the cases were classified as nonclassic variants. MAML2 rearrangement was detected in 56% of cases, and the fusion partner was CRTC1 in all cases. CRTC1-MAML2 fusion was associated with lower pT classification and lower TNM stage. The overall survival rate of all patients was 69% and 43% at 5 and 10 years, respectively. Worse overall survival was associated with higher pT stage, higher TNM stage, residual tumors, greater tumor size, high-grade tumor histology (Armed Forces Institutes of Pathology and Memorial Sloan-Kettering, but not the other 2), and with the absence of CRTC1-MAML2 fusion. Of note, none of the patients with CRTC1-MAML2 fusion-positive tumors died during the follow-up. In conclusion, the clinicopathologic and molecular findings of thymic MEC presented here are expected to contribute to the management of this rare tumor.

miR-22 and miR-205 Drive Tumor Aggressiveness of Mucoepidermoid Carcinomas of Salivary Glands

Objectives

To integrate mRNA and miRNA expression profiles of mucoepidermoid carcinomas (MECs) and normal salivary gland (NSGs) tissue samples and identify potential drivers.

Material and Methods

Gene and miRNA expression arrays were performed in 35 MECs and six NSGs.

Results

We found 46 differentially expressed (DE) miRNAs and 3,162 DE mRNAs. Supervised hierarchical clustering analysis of the DE transcripts revealed two clusters in both miRNA and mRNA profiles, which distinguished MEC from NSG samples. The integrative miRNA-mRNA analysis revealed a network comprising 696 negatively correlated interactions (44 miRNAs and 444 mRNAs) involving cell signaling, cell cycle, and cancer-related pathways. Increased expression levels of miR-205-5p and miR-224-5p and decreased expression levels of miR-139-3p, miR-145-3p, miR-148a-3p, miR-186-5p, miR-338-3p, miR-363-3p, and miR-4324 were significantly related to worse overall survival in MEC patients. Two overexpressed miRNAs in MEC (miR-22 and miR-205) were selected for inhibition by the CRISPR-Cas9 method. Cell viability, migration, and invasion assays were performed using an intermediate grade MEC cell line. Knockout of miR-205 reduced cell viability and enhanced ZEB2 expression, while miR-22 knockout reduced cell migration and invasion and enhanced ESR1 expression. Our results indicate a distinct transcriptomic profile of MEC compared to NSG, and the integrative analysis highlighted miRNA-mRNA interactions involving cancer-related pathways, including PTEN and PI3K/AKT.

Conclusion

The in vitro functional studies revealed that miR-22 and miR-205 deficiencies reduced the viability, migration, and invasion of the MEC cells suggesting they are potential oncogenic drivers in MEC.

Establishment of a patient‑derived mucoepidermoid carcinoma cell line with the CRTC1‑MAML2 fusion gene

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of the major and minor salivary glands. Surgical resection is the only curative treatment and there is no effective post-operative therapy for MEC. The present study reports an Institutional Review Board-approved case of a 45-year-old Japanese female diagnosed with low-grade MEC in the hard palate. Radical resection, supraomohyoid neck dissection and antero-lateral thigh flap reconstruction was performed. A MEC cell line was then established from the resected tumor tissue. Short tandem repeat profiling confirmed the origin and authenticity of the cell line, that harbors a CRTC1-MAML2 translocation, which is frequently observed in MEC. Amphiregulin (AREG), identified as one of the targets of the CRTC1-MAML2 fusion gene, was expressed in the cell line. The AREG receptor, epidermal growth factor receptor (EGFR) was also highly phosphorylated. The results predicted that AREG-EGFR signaling, which is required for tumor growth and survival, might be activated in the cell line in a cell-autonomous manner. As AREG expression is associated with EGFR-targeted drug resistance, this cell line might assist with the identification of novel strategies for MEC treatment.

Dependency of human and murine LKB1-inactivated lung cancer on aberrant CRTC-CREB activation

Lung cancer with loss-of-function of the LKB1 tumor suppressor is a common aggressive subgroup with no effective therapies. LKB1-deficiency induces constitutive activation of cAMP/CREB-mediated transcription by a family of three CREB-regulated transcription coactivators (CRTC1-3). However, the significance and mechanism of CRTC activation in promoting the aggressive phenotype of LKB1-null cancer remain poorly characterized. Here, we observed overlapping CRTC expression patterns and mild growth phenotypes of individual CRTC-knockouts in lung cancer, suggesting functional redundancy of CRTC1-3. We consequently designed a dominant-negative mutant (dnCRTC) to block all three CRTCs to bind and co-activate CREB. Expression of dnCRTC efficiently inhibited the aberrantly activated cAMP/CREB-mediated oncogenic transcriptional program induced by LKB1-deficiency, and specifically blocked the growth of human and murine LKB1-inactivated lung cancer. Collectively, this study provides direct proof for an essential role of the CRTC-CREB activation in promoting the malignant phenotypes of LKB1-null lung cancer and proposes the CRTC-CREB interaction interface as a novel therapeutic target.

Epithelial cell plasticity: breaking boundaries and changing landscapes

Epithelial tissues respond to a wide variety of environmental and genotoxic stresses. As an adaptive mechanism, cells can deviate from their natural paths to acquire new identities, both within and across lineages. Under extreme conditions, epithelial tissues can utilize "shape-shifting" mechanisms whereby they alter their form and function at a tissue-wide scale. Mounting evidence suggests that in order to acquire these alternate tissue identities, cells follow a core set of "tissue logic" principles based on developmental paradigms. Here, we review the terminology and the concepts that have been put forward to describe cell plasticity. We also provide insights into various cell intrinsic and extrinsic factors, including genetic mutations, inflammation, microbiota, and therapeutic agents that contribute to cell plasticity. Additionally, we discuss recent studies that have sought to decode the "syntax" of plasticity-i.e., the cellular and molecular principles through which cells acquire new identities in both homeostatic and malignant epithelial tissues-and how these processes can be manipulated for developing novel cancer therapeutics.

The CRTC1-MAML2 fusion is the major oncogenic driver in mucoepidermoid carcinoma

No effective systemic treatment is available for patients with unresectable, recurrent, or metastatic mucoepidermoid carcinoma (MEC), the most common salivary gland malignancy. MEC is frequently associated with a t(11;19)(q14-21;p12-13) translocation that creates a CRTC1-MAML2 fusion gene. The CRTC1-MAML2 fusion exhibited transforming activity in vitro; however, whether it serves as an oncogenic driver for MEC establishment and maintenance in vivo remains unknown. Here, we show that doxycycline-induced CRTC1-MAML2 knockdown blocked the growth of established MEC xenografts, validating CRTC1-MAML2 as a therapeutic target. We further generated a conditional transgenic mouse model and observed that Cre-induced CRTC1-MAML2 expression caused 100% penetrant formation of salivary gland tumors resembling histological and molecular characteristics of human MEC. Molecular analysis of MEC tumors revealed altered p16-CDK4/6-RB pathway activity as a potential cooperating event in promoting CRTC1-MAML2–induced tumorigenesis. Cotargeting of aberrant p16-CDK4/6-RB signaling and CRTC1-MAML2 fusion–activated AREG/EGFR signaling with the respective CDK4/6 inhibitor Palbociclib and EGFR inhibitor Erlotinib produced enhanced antitumor responses in vitro and in vivo. Collectively, this study provides direct evidence for CRTC1-MAML2 as a key driver for MEC development and maintenance and identifies a potentially novel combination therapy with FDA-approved EGFR and CDK4/6 inhibitors as a potential viable strategy for patients with MEC.

Synergistic efficacy of combined EGFR and HDAC inhibitors overcomes tolerance to EGFR monotherapy in salivary mucoepidermoid carcinoma

OBJECTIVES

Mucoepidermoid carcinoma (MEC) is the most common type of salivary gland malignancy. Advanced or high-grade MECs are refractory to chemotherapy, often leading to tumor recurrence/metastasis and abysmal ~35% 5-year survival. Causal links have been established between Epithelial Growth Factor Receptor (EGFR) activation and poor outcome. Herein we investigated the therapeutic efficacy of EGFR inhibition against MEC using in vitro pre-clinical models.

MATERIALS AND METHODS

Five human MEC cell lines were used in cell viability, cytotoxicity, apoptosis, cell cycle, 2D-clonogenicity, and 3D-spheroid formation assays following treatment with Erlotinib (EGFR inhibitor), SAHA (Histone Deacetylase inhibitor; HDAC) and CUDC-101 (dual EGFR-HDAC inhibitor). Effects on MEC cancer stem cells were evaluated using flow cytometry. Gene expression and pathway regulation were evaluated via qPCR and Western blot, respectively.

RESULTS

MEC cells enter a quiescent, non-proliferative yet rapidly reversible drug tolerant state upon EGFR inhibition. Despite robust suppression of MEC cell proliferation, no discernable apoptosis is detected. Combination of EGFR and HDAC inhibitors exhibits synergistic effects, exerting ~5-fold more potent cell cytotoxicity compared to HDAC or EGFR monotherapy. CUDC-101, a single molecule with dual EGFR-HDAC inhibitor moieties, exerts irreversible and potent cytotoxic activity against MEC cells and blunts MEC cancer stem-cell tumorigenicity.

CONCLUSION

MEC cells are intrinsically tolerant to EGFR inhibition. Combining EGFR and HDAC inhibitors exerts synergistic and potent cytotoxic effects, suggesting that EGFR inhibitors still hold significant promise against MEC. Future studies are needed to assess the applicability and efficacy of dual EGFR-HDAC inhibitors for the clinical management of MEC.

Molecular Pathology of Salivary Gland Neoplasms: Diagnostic, Prognostic, and Predictive Perspective

Salivary gland neoplasms are an uncommon and widely heterogeneous group of tumors. In recent years, there has been considerable progress in efforts to reveal the molecular landscape of these tumors, although it is still limited and appears to be only the tip of the iceberg. Genomic aberrations, especially specific chromosomal rearrangements including CRTC1-MAML2 and CRTC3-MAML2 in mucoepidermoid carcinoma, MYB-NFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 alterations in pleomorphic adenoma and carcinoma ex pleomorphic adenoma, ETV6-NTRK3 and ETV6-RET in secretory carcinoma, EWSR1-ATF1 and EWSR1-CREM in clear cell carcinoma, provide new insights into the molecular pathogenesis of various salivary gland neoplasms and help to better classify them. These genetic aberrations primarily serve as diagnostic tools in salivary gland tumor diagnosis; however, some also have promise as prognostic or predictive biomarkers. This review summarizes the latest developments in molecular pathology of salivary gland tumors with a focus on distinctive molecular characteristics.

CRTC1/MAML2 directs a PGC-1α-IGF-1 circuit that confers vulnerability to PPARγ inhibition

Mucoepidermoid carcinoma (MEC) is a life-threatening salivary gland cancer that is driven primarily by a transcriptional coactivator fusion composed of cyclic AMP-regulated transcriptional coactivator 1 (CRTC1) and mastermind-like 2 (MAML2). The mechanisms by which the chimeric CRTC1/MAML2 (C1/M2) oncoprotein rewires gene expression programs that promote tumorigenesis remain poorly understood. Here, we show that C1/M2 induces transcriptional activation of the non-canonical peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) splice variant PGC-1α4, which regulates peroxisome proliferator-activated receptor gamma (PPARγ)-mediated insulin-like growth factor 1 (IGF-1) expression. This mitogenic transcriptional circuitry is consistent across cell lines and primary tumors. C1/M2-positive tumors exhibit IGF-1 pathway activation, and small-molecule drug screens reveal that tumor cells harboring the fusion gene are selectively sensitive to IGF-1 receptor (IGF-1R) inhibition. Furthermore, this dependence on autocrine regulation of IGF-1 transcription renders MEC cells susceptible to PPARγ inhibition with inverse agonists. These results yield insights into the aberrant coregulatory functions of C1/M2 and identify a specific vulnerability that can be exploited for precision therapy.

Targeting Notch and EGFR signaling in human mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most common type of salivary gland cancers and patients with advanced, metastatic, and recurrent MECs have limited therapeutic options and poor treatment outcomes. MEC is commonly associated with a chromosomal translocation t(11;19) (q14-21;p12-13) that encodes the CRTC1-MAML2 oncogenic fusion. The CRTC1-MAML2 fusion is required for MEC growth in part through inducing autocrine AREG-EGFR signaling. Growing evidence suggests that MEC malignancy is maintained by cancer stem-like cells. In this study, we aimed to determine critical signaling for maintaining MEC stem-like cells and the effect of combined targeting of stem cell signaling and CRTC1-MAML2-induced EGFR signaling on blocking MEC growth. First, we evaluated the significance of Notch signaling in regulating MEC stem-like cells. Aberrantly activated Notch signaling was detected in human fusion-positive MEC cells. The inhibition of Notch signaling with genetic or pharmacological inhibitors reduced oncosphere formation and ALDH-bright population in vitro and blocked the growth of MEC xenografts in vivo. Next, we investigated the effect of co-targeting Notch signaling and EGFR signaling, and observed enhanced inhibition on MEC growth in vivo. Collectively, this study identified a critical role of Notch signaling in maintaining MEC stem-like cells and tumor growth, and revealed a novel approach of co-targeting Notch and EGFR signaling as a potential effective anti-MEC treatment.

Prognostic impact of CRTC1/3-MAML2 fusions in salivary gland mucoepidermoid carcinoma: A multiinstitutional retrospective study

Mucoepidermoid carcinoma (MEC) is rare, but the most common primary malignancy of the salivary gland and not infrequent in young individuals. CRTC1/3-MAML2 fusions are frequently detected in MEC and are useful as a diagnostic biomarker. However, there has been debate as to whether the fusions have prognostic significance. In this study, we retrospectively collected 153 salivary gland MEC cases from 11 tertiary hospitals in Japan. As inclusion criteria, the MEC patients in this study had curative surgery as the initial treatment, received no preoperative treatment, and had no distant metastasis at the time of the initial surgery. The MEC diagnosis was validated by a central pathology review by five expert salivary gland pathologists. The CRTC1/3-MAML2 fusions were detected using FISH and RT-PCR. In 153 MEC cases, 90 (58.8%) were positive for CRTC1/3-MAML2 fusions. During the follow-up period, 28 (18.3%) patients showed tumor recurrence and 12 (7.8%) patients died. The presence of the fusions was associated with favorable tumor features. Of note, none of the fusion-positive patients died during the follow-up period. Statistical analysis showed that the presence of the fusions was a prognostic indicator of a better overall survival in the total and advanced-stage MEC cohorts, but not in the early-stage MEC cohort. In conclusion, CRTC1/3-MAML2 fusions are an excellent biomarker for favorable overall survival of patients with salivary gland MEC.

Gefitinib Represses JAK-STAT Signaling Activated by CRTC1-MAML2 Fusion in Mucoepidermoid Carcinoma Cells

BACKGROUND

Gefitinib is well-known as a tyrosine kinase inhibitor targeting non-smalllung- cancer (NSCLC) containing EGFR mutations. However, its effectiveness in treating mucoepidermoid carcinoma (MEC) without such EGFR mutations suggests additional targets.

OBJECTIVE

The CRTC1-MAML2 (C1-M2) fusion typical for MEC has been proposed to be a gefitinib target.

METHODS

To test this hypothesis, we developed a set of siRNAs to down-regulate C1-M2 expression. RNA-seq and Western blot techniques were applied to analyze the effects of gefitinib and siC1-M2 on the transcriptome of and the phosphorylation of tyrosine kinases in a MEC cell line H292.

RESULTS

Deep-sequencing transcriptome analysis revealed that gefitinib extensively inhibited transcription of genes in JAK-STAT and MAPK/ERK pathways. Both siC1-M2 and gefitinib inhibited the phosphorylation of multiple signaling kinases in these signaling pathways, indicating that gefitinib inhibited JAK-STAT and MAPK/ERK pathways activated by C1-M2 fusion. Moreover, gefitinib inhibition of EGFR and MAPK/ERK was more effective than that of AKT, JAK2 and STATs, and their dependence on C1-M2 could be uncoupled. Taken together, our results suggest that gefitinib simultaneously represses phosphorylation of multiple key signaling proteins which are activated in MEC, in part by C1-M2 fusion. Gefitinib-repressed kinase phosphorylation explains the transcriptional repression of genes in JAK-STAT and MAPK/ERK pathways.

CONCLUSION

These findings provide new insights into the efficacy of gefitinib in treating mucoepidermoid carcinoma, and suggest that a combination of gefitinib and other inhibitors specifically against C1-M2 fusion could be more effective.

Clinicopathological significance of EGFR pathway gene mutations and CRTC1/3-MAML2 fusions in salivary gland mucoepidermoid carcinoma

AIMS

Mucoepidermoid carcinoma (MEC) is one of the most common salivary gland carcinomas. Epidermal growth factor receptor (EGFR) signalling pathway gene mutations are important in predicting a patient's prognosis, selecting molecularly targeted drugs and estimating the efficacy of a molecular therapy. However, their significance in MEC have been poorly clarified. CRTC1/3-MAML2 fusions are specific to MEC and may be associated with favourable characteristics in these patients.

METHODS AND RESULTS

We looked for CRTC1/3-MAML2 fusions and gene alterations in the EGFR, RAS family (KRAS, HRAS and NRAS), PIK3CA, BRAF and AKT1 in 101 MEC cases. We also examined mutations in TP53. CRTC1/3-MAML2 fusions were found in 62.4% of the cases. KRAS, HRAS and PIK3CA mutations were detected in 6.9%, 2.0% and 6.9%, respectively, but other EGFR pathway genes were not mutated. In total, gene mutations (RAS/PIK3CA) in the EGFR pathway were detected in 14.9% of the cases. TP53 mutations were found in 20.8%. CRTC1/3-MAML2 fusions were associated with a better prognosis and RAS/PIK3CA mutations a worse prognosis of the patients, respectively, and both were selected as independent prognostic factors for the overall survival of the patients. TP53 mutations had no prognostic impact. CRTC1/3-MAML2 fusion-positive rates were inversely associated with the patients' age and the fusions were found in 82% of patients aged < 30 years.

CONCLUSIONS

RAS/PIK3CA mutations were frequently detected, and may be a biomarker for a poorer prognosis in MEC patients. CTRC1/3-MAML2 fusions were positive in most of the young MEC patients.

Metaplastic thymoma: a distinctive thymic neoplasm characterized by YAP1-MAML2 gene fusions

Metaplastic thymomas are rare biphasic thymic tumors that are characteristically well-circumscribed, confined to the thymus, and follow a benign to indolent clinical course. Their relationship to other thymic neoplasms remains unclear, and their molecular characteristics have not been defined. We report for the first time recurrent translocation events in metaplastic thymomas involving the Yes Associated Protein 1 (YAP1) and Mastermind Like Transcriptional Coactivator 2 (MAML2) genes. Eight metaplastic thymomas were retrieved from two institutions' archives over a 21-year period. Paraffin-embedded material from all cases underwent targeted DNA-based hybrid capture next-generation sequencing. Cases showing no somatic alterations subsequently underwent targeted RNA sequencing. Allele-specific real-time polymerase chain reaction was performed to detect GTF2I c.74146970T>A (p.L424H) mutations. All cases showed characteristic histologic features of metaplastic thymoma and demonstrated no local recurrence or distant metastatic disease at 1-22 years of follow-up. Six of eight cases were successfully sequenced, all showing YAP1-MAML2 fusions; in four cases the fusions were detected by DNA sequencing and in two cases by RNA sequencing. Two distinct products were identified: 5' YAP1 exon 1 fused to 3' MAML2 exons 2-5 or 5' YAP1 exons 1-5 fused to 3' MAML2 exons 2-5. All cases underwent allele-specific real-time polymerase chain reaction and demonstrated no GTF2I L424H mutations. Metaplastic thymoma is a distinct, clinically indolent thymic epithelial neoplasm characterized by YAP1-MAML2 fusion and lacking the GTF2I mutations found in Type A and AB thymomas.

Nasopharyngeal Hyalinizing Clear Cell Carcinoma: A Case Report and Review of the Literature

Background

Hyalinizing clear cell carcinomas (HCCCs) are rare, low-grade, malignant tumors which most often arise from the minor salivary glands primarily in palate and tongue but can arise in any location with minor salivary glands including the nasopharynx.

Methods

A case report of primary nasopharyngeal HCCC is presented. Because of the rarity of this tumor and location, a literature search was conducted to determine the most common presenting symptoms, treatment strategies, and outcomes.

Results

A 48-year-old man underwent biopsy of a 4.5 cm mass of the right nasopharynx with pathology suggesting an intermediate grade mucoepidermoid carcinoma. After discussing management with the patient, an endoscopic resection was performed. Final pathology revealed an HCCC which was confirmed after negative Mastermind-like 2 (MAML2) and positive Ewing sarcoma breakpoint region 1 (ESWR1) gene rearrangements on fluorescence in situ hybridization (FISH) studies. Literature review of other nasopharyngeal HCCC cases shows diverse presentation and overall excellent prognosis through surgical and radiation therapy.

Conclusion

HCCCs are rare, low-grade malignant tumors of the minor salivary glands and can present as a nasopharyngeal mass. Presenting symptoms are diverse but frequently involve otologic and sinonasal disturbances. HCCC is an indolent tumor with an excellent prognostic outcome when treated appropriately with surgical resection and adjuvant radiotherapy.

Integrated Genomic, Epigenomic, and Expression Analyses of Ovarian Cancer Cell Lines

To improve our understanding of ovarian cancer, we performed genome-wide analyses of 45 ovarian cancer cell lines. Given the challenges of genomic analyses of tumors without matched normal samples, we developed approaches for detection of somatic sequence and structural changes and integrated these with epigenetic and expression alterations. Alterations not previously implicated in ovarian cancer included amplification or overexpression of ASXL1 and H3F3B, deletion or underexpression of CDC73 and TGF-beta receptor pathway members, and rearrangements of YAP1-MAML2 and IKZF2-ERBB4. Dose-response analyses to targeted therapies revealed unique molecular dependencies, including increased sensitivity of tumors with PIK3CA and PPP2R1A alterations to PI3K inhibitor GNE-493, MYC amplifications to PARP inhibitor BMN673, and SMAD3/4 alterations to MEK inhibitor MEK162. Genome-wide rearrangements provided an improved measure of sensitivity to PARP inhibition. This study provides a comprehensive and broadly accessible resource of molecular information for the development of therapeutic avenues in ovarian cancer.

The overall survival of patients with late-stage ovarian cancer is dismal. To identify therapeutic opportunities, Papp et al. integrate genomic, epigenomic, and expression analyses to provide a resource of molecular abnormalities in ovarian cancer cell lines and use these to identify tumors sensitive to PARP, MEK, and PI3K inhibitors.

Prognostic value of CRTC1-MAML2 translocation in salivary mucoepidermoid carcinoma: Systematic review and meta-analysis

The presence of the CRTC1-MAML2 translocation has been described in mucoepidermoid carcinoma (MEC) as a predictor of better survival rates. However, the real prognostic value of the translocation has been debated due to recent controversial findings. The aim of this study was to perform a systematic review to understand the prognostic potential of the CRTC1-MAML2 translocation in MEC. An electronic search was carried out using the MEDLINE/PubMed, EMBASE and Scopus databases. Articles that assessed the association between the CRTC1-MAML2 translocation and survival of MEC patients were selected for the systematic review. Ten published articles were included in the qualitative synthesis. The prevalence of the translocation varied from 33.7% to 69.7%. Seven studies observed a significant association between the presence of the CRTC1-MAML2 translocation and a favourable clinical outcome, which could improve disease-free, disease-specific or overall survival. Five studies were included in the quantitative synthesis. Fixed-effects model confirmed that translocation-positive patients have a decreased risk of death (combined odds ratio 0.08, 95% confidence interval - 0.03-0.23, P < .00001). The detection of the CRTC1-MAML2 translocation appears to be useful as a prognostic factor in MEC. However, the level of evidence is not as high as it could be once important limitations were found in the published studies.

CRKL regulates alternative splicing of cancer-related genes in cervical cancer samples and HeLa cell

BACKGROUND

Aberrant spliced isoforms are specifically associated with cancer progression and metastasis. The cytoplasmic adaptor CRKL (v-crk avian sarcoma virus CT10 oncogene homolog-like) is a CRK like proto-oncogene, which encodes a SH2 and SH3 (src homology) domain-containing adaptor protein. CRKL is tightly linked to leukemia via its binding partners BCR-ABL and TEL-ABL, upregulated in multiple types of human cancers, and induce cancer cell proliferation and invasion. However, it remains unclear whether signaling adaptors such as CRKL could regulate alternative splicing.

METHODS

We analyzed the expression level of CRKL in 305 cervical cancer tissue samples available in TCGA database, and then selected two groups of cancer samples with CRKL differentially expressed to analyzed potential CRKL-regulated alternative splicing events (ASEs). CRKL was knocked down by shRNA to further study CRKL-regulated alternative splicing and the activity of SR protein kinases in HeLa cells using RNA-Seq and Western blot techniques. We validated 43 CRKL-regulated ASEs detected by RNA-seq in HeLa cells, using RT-qPCR analysis of HeLa cell samples and using RNA-seq data of the two group of clinical cervical samples.

RESULTS

The expression of CRKL was mostly up-regulated in stage I cervical cancer samples. Knock-down of CRKL led to a reduced cell proliferation. CRKL-regulated alternative splicing of a large number of genes were enriched in cancer-related functional pathways, among which DNA repair and G2/M mitotic cell cycle, GnRH signaling were shared among the top 10 enriched GO terms and KEGG pathways by results from clinical samples and HeLa cell model. We showed that CRKL-regulated ASEs revealed by computational analysis using ABLas software in HeLa cell were highly validated by RT-qPCR, and also validated by cervical cancer clinical samples.

CONCLUSIONS

This is the first report of CRKL-regulation of the alternative splicing of a number of genes critical in tumorigenesis and cancer progression, which is consistent with CRKL reported role as a signaling adaptor and a kinase. Our results underline that the signaling adaptor CRKL might integrate the external and intrinsic cellular signals and coordinate the dynamic activation of cellular signaling pathways including alternative splicing regulation.

Adaptive Transcriptional Responses by CRTC Coactivators in Cancer

Adaptive stress signaling networks directly influence tumor development and progression. These pathways mediate responses that allow cancer cells to cope with both tumor cell-intrinsic and cell-extrinsic insults and develop acquired resistance to therapeutic interventions. This is mediated in part by constant oncogenic rewiring at the transcriptional level by integration of extracellular cues that promote cell survival and malignant transformation. The cAMP-regulated transcriptional coactivators (CRTCs) are a newly discovered family of intracellular signaling integrators that serve as the conduit to the basic transcriptional machinery to regulate a host of adaptive response genes. Thus, somatic alterations that lead to CRTC activation are emerging as key driver events in the development and progression of many tumor subtypes.

Postoperative radiotherapy for T1/2N0M0 mucoepidermoid carcinoma positive for CRTC1/3-MAML2 fusions

BACKGROUND

The National Comprehensive Cancer Network (NCCN) guidelines recommend considering postoperative radiotherapy (PORT) for completely resected T1/2N0M0 salivary mucoepidermoid carcinomas when they show tumor spillage, perineural invasion, or intermediate/high-grade histology. CRTC1/3-MAML2 fusions have been associated with a favorable clinical outcome.

METHODS

Forty-seven T1/2N0M0 mucoepidermoid carcinoma cases positive for CRTC1/3-MAML2 fusions were completely resected and were not treated with PORT.

RESULTS

Pathologically, none of the cases showed tumor spillage or perineural invasion. Cases with intermediate/high-grade histology numbered 9 (19%) to 26 (55%) with the currently used 3 different grading systems. During the follow-up (median 60 months), locoregional tumor recurrence occurred in 4 cases, which were treated with surgery alone. At the last follow-up (median 60 months; 7-160), all patients were alive with no evidence of disease.

CONCLUSION

An excellent prognosis may be achieved without PORT in T1/2N0M0 mucoepidermoid carcinoma patients positive for CRTC1/3-MAML2 fusions when the tumors are completely resected without tumor spillage.

Genomics of mucoepidermoid and adenoid cystic carcinomas

Objective

To report on the current state of the literature on the genetics of mucoepidermoid and adenoid cystic carcinomas of the salivary glands with a focus on genomic screens and recently discovered genetic translocations.

Methods

A PubMed based literature review was performed to query for genetics related basic science and preclinical studies about mucoepidermoid and adenoid cystic carcinomas of the salivary glands.

Results and conclusions

Genetic translocations between CRTC1 and MAML2 in mucoepidermoid carcinoma and between MYB and NFIB in adenoid cystic carcinoma have been recently discovered and have therapeutic implications. Key signaling pathways such as the EGFR pathway in mucoepidermoid carcinoma and the Notch pathway, chromatin regulation, and c‐kit mediated epithelial‐mesenchymal transitions in adenoid cystic carcinoma have recently been elucidated, pointing to possible therapeutic targets in both cancers.

CRTC1-MAML2 fusion-induced lncRNA LINC00473 expression maintains the growth and survival of human mucoepidermoid carcinoma cells

Mucoepidermoid carcinoma (MEC) arises in many glandular tissues and contributes to the most common malignant salivary gland cancers. MEC is specifically associated with a unique t(11;19) translocation and the resulting CRTC1-MAML2 fusion is a major oncogenic driver for MEC initiation and maintenance. However, the molecular basis underlying the CRTC1-MAML2 oncogenic functions remain very limited. Through gene expression profiling analysis, we observed that LINC00473, a long noncoding RNA (lncRNA), was the top down-regulated target in CRTC1-MAML2-depleted human MEC cells. LncRNAs belong to a new class of non-coding RNAs with emerging roles in tumorigenesis and progression, but remain poorly characterized. In this study, we investigated the role of LINC00473 in mediating CRTC1-MAML2 oncogenic activity in human MEC. We found that LINC00473 transcription was significantly induced in human CRTC1-MAML2-positive MEC cell lines and primary MEC tumors, and was tightly correlated with the CRTC1-MAML2 RNA level. LINC00473 induction was dependent on the ability of CRTC1-MAML2 to activate CREB-mediated transcription. Depletion of LINC00473 significantly reduced the proliferation and survival of human MEC cells in vitro and blocked the in vivo tumor growth in a human MEC xenograft model. RNA in situ hybridization analysis demonstrated a predominantly nuclear localization pattern for LINC00473 in human MEC cells. Furthermore, gene expression profiling revealed that LINC00473 depletion resulted in differential expression of genes important in cancer cell growth and survival. LINC00473 likely regulates gene expression in part through its ability to bind to a cAMP signaling pathway component NONO, enhancing the ability of CRTC1-MAML2 to activate CREB-mediated transcription. Our overall results demonstrate that LINC00473 is a downstream target and an important mediator of the CRTC1-MAML2 oncoprotein. Therefore, LINC00473 acts as a promising biomarker and therapeutic target for human CRTC1-MAML2-positive MECs.

Drug screening to target nuclear orphan receptor NR4A2 for cancer therapeutics

Background

Our previous study suggested NR4A2, a subfamily member of orphan nuclear receptors, is essential for survival of human cancer cells such as mucoepidermoid carcinoma (MEC).

Methods

We conducted high throughput drug screening for NR4A2 inhibitors as a novel therapeutic modality. Positive screening was performed using a luciferase reporter vector containing NR4A2 binding sequence, and a CRE-reporter control vector was used to eliminate false positives. In vitro assays for positive hits were conducted.

Results

A total of 23 Food and Drug Administration (FDA) and 43 Life Science Library compounds were identified, including several epidermal growth factor inhibitors and Src inhibitors. Subsequent in vitro assays confirmed that identified compounds were preferentially active in NR4A2+ cancer cells. Several candidate compounds appeared to suppress NR4A2 via inhibition of p-ERK, whereas a novel compound KU0171309 may act as a more direct inhibitor.

Conclusions

Further research should focus on homologue selectivity, in vivo activity, and definitively deciphering the mechanism of action of KU0171309.

Immunohistochemical and molecular profile of salivary gland cancer in children

BACKGROUND

Pediatric salivary gland carcinomas (SGCs) are very rare. They differ from the adult SGCs in terms of epidemiologic and clinical behavior, being generally limited only to selected histotypes (e.g. low-grade mucoepidermoid [LG-MEC] and acinic cell cancer [AcCC]) and characterized by very good outcome. Our aim was to investigate therapeutic targets on a series of pediatric SGCs by immunohistochemical and molecular analysis.

METHODS

A retrospective analysis was performed to search for cases of pediatric SGCs in the database of the Pediatric Oncology Unit at the Istituto Nazionale Tumori and in the Pathology database at the Gerhard-Seifert-Reference-Centre. The expressions of the most common tyrosine-kinase receptors (TKRs) reported in adult SGCs as EGFR, HER2, KIT and hormonal receptors (HRs) (estrogen α and β, progesterone as well as androgen receptors) were investigated. CRTC1/MAML2 and MYB/NFIB were also analyzed in MEC and adenoid cystic carcinoma cases, respectively.

RESULTS

Twenty-nine cases were identified: 22 MECs, 4 AcCCs, 1 adenoid cystic carcinoma (ACC), 1 adenocarcinoma not otherwise specified and 1 sialoblastoma. EGFR was the most expressed TKR, whilst HRs were negative in all cases except for ER-β in four cases of MEC. CRTC1/MAML2 was present in 15 out of 17 evaluable MEC cases and MYB/NFIB was identified in the ACC case.

CONCLUSIONS

The immunohistochemical and molecular profiles of pediatric SGCs analyzed in our series are similar to that observed in adults, especially for MEC, supporting a common biological background.

Correlation of Crtc1/3-Maml2 fusion status, grade and survival in mucoepidermoid carcinoma

OBJECTIVE

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of the salivary glands. Tumor stage and grade have historically been important predictors of survival. An oncogenic CRTC1- or CRTC3-MAML2 gene fusion has been identified in a number of MECs. Historically, these gene fusions have been associated with lower grade tumors and better survival. However, reported gene fusion rates and prognosis varies widely across studies, and have not controlled for tumor grade. We sought to identify gene fusion rates and outcomes in our cohort of MEC patients.

MATERIALS AND METHODS

An IRB-approved retrospective cohort of patients with MEC was identified at the University of Michigan. Clinical, histologic, and outcome data was collected from medical records. RNA was isolated from formalin fixed paraffin-embedded tumor sections, and qRT-PCR was performed to identify CRTC1/3-MAML2 gene fusions. Sanger sequencing of qRT-PCR products was used to confirm gene fusions.

RESULTS

Overall, 90 patient MEC tumors were collected (58 low-grade, 25 intermediate-grade, and 7 high-grade). Gene fusions were identified in 59% (53/90) of tumors. On univariate and bivariate analysis, fusion status did not significantly associate with grade or survival.

CONCLUSION

We have identified a high rate of CRTC1/3-MAML2 gene fusions in a large cohort of MEC. We do not identify any correlation between fusion status with tumor grade or survival. These findings suggest further characterization of MECs is needed before considering the CRTC1/3-MAML2 gene fusion as a prognostic biomarker. Additional genetic drivers may account for survival and grade in MECs.

Bronchial mucoepidermoid carcinoma: A case report

INTRODUCTION

Bronchial localization of Mucoepidermoid carcinoma (MEC) is rare. The precise nature of these neoplasms is not yet clear and little is known on the histogenesis and pathogenesis of the disease. Here we present a case of a bronchial MEC with a detailed pathological, immunohistochemical, and molecular analysis.

PRESENTATION OF A CASE

A 46 years old Caucasian male patient was referred to our Unit for fever, non productive cough and dyspnea lasting for two months. The chest CT scan evidenced an 8-mm intraluminal lesion in the left main bronchus, in correspondence of the origin of the lingular segmental bronchus. Multiple biopsies were performed through bronchoscopy, and the diagnosis of a mucoepidermoid carcinoma of the lung was obtained. A left upper lobectomy was performed. The histopathological examination confirmed the preoperative diagnosis and stage (pT1N0M0). No further therapies were employed, given the stage of the disease. The patient is presently free of disease, approximately three years after surgery.

DISCUSSION

The treatment of MECs is usually surgical by traditional or sleeve lobectomy, performed with an open or video-assisted technique, with the aim of an R0 resection. In this stage the prognosis is excellent. Conversely, high grade tumors seems to be particularly aggressive, even more than other NSCLC.

CONCLUSIONS

Low grade type of Bronchial MEC, as our case, is often characterized by an optimal clinical management and prognosis. The lack of EGFR sensitizing mutations does not preclude the use of TKIs, which may be extremely useful in patients non responsive to other therapies.

Expression of amphiregulin in mucoepidermoid carcinoma of the major salivary glands: a molecular and clinicopathological study

In mucoepidermoid carcinoma (MEC), CRTC1-MAML2 fusion indicates a favorable prognosis. Amphiregulin (AREG), an epidermal growth factor receptor (EGFR) ligand, has been shown to be a downstream target of CRTC1-MAML2 fusion, and to play a role in tumor growth and survival in CRTC1-MAML2-positive MEC cell lines. The aim of this study was to characterize the AREG and EGFR expression in the fusion-positive and fusion-negative MEC of the major salivary gland. The AREG and EGFR expression were studied by immunochemistry in 33 MEC cases of the major salivary glands. CRTC1-MAML2 fusion was tested by reverse-transcription polymerase chain reaction (23 CRTC1-MAML2 fusion-positive, 10 fusion-negative). Of 23 fusion-positive cases, AREG and EGFR overexpression were detected in 17 (73.9%) and 14 (60.9%) cases, respectively. Of 10 fusion-negative cases, AREG and EGFR overexpression were detected in 1 (10%) and 3 (30.0%) cases, respectively. There was a positive correlation between CRTC1-MAML2 fusion and AREG overexpression (P < .01), but not between CRTC1-MAML2 fusion and EGFR overexpression. The AREG overexpression was associated with a longer disease-free survival of the MEC patients (P = .042), but EGFR overexpression was not. In this study, we showed that AREG overexpression was detected more frequently in the CRTC1-MAML2 fusion-positive tumors than in fusion-negative tumors. Detection of AREG expression may be useful for identifying CRTC1-MAML2-positive MECs and as a marker for favorable prognosis.

Whole-Exome Sequencing of Salivary Gland Mucoepidermoid Carcinoma

PURPOSE

Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. To explore the genetic origins of MEC, we performed systematic genomic analyses of these tumors.

EXPERIMENTAL DESIGN

Whole-exome sequencing and gene copy-number analyses were performed for 18 primary cancers with matched normal tissue. FISH was used to determine the presence or absence of the MECT1-MAML2 translocation in 17 tumors.

RESULTS

TP53 was the most commonly mutated gene in MEC (28%), and mutations were found only in intermediate- and high-grade tumors. Tumors with TP53 mutations had more mutations overall than tumors without TP53 mutations (P = 0.006). POU6F2 was the second most frequently mutated gene, found in three low-grade MECs with the same in-frame deletion. Somatic alterations in IRAK1, MAP3K9, ITGAL, ERBB4, OTOGL, KMT2C, and OBSCN were identified in at least two of the 18 tumors sequenced. FISH analysis confirmed the presence of the MECT1-MAML2 translocation in 15 of 17 tumors (88%).

CONCLUSIONS

Through these integrated genomic analyses, MECT1-MAML2 translocation and somatic TP53 and POU6F2 mutations appear to be the main drivers of MEC. Clin Cancer Res; 23(1); 283-8. ©2016 AACR.

Fine-Needle Aspiration Biopsy of Salivary Gland Lesions

CONTEXT

Fine-needle aspiration (FNA) is a well-established diagnostic approach for salivary gland lesions; however, lack of a standard system of terminology for classification of salivary gland neoplasms collected by FNA and the relatively high frequency of uncertainty of diagnosis are likely partly responsible for current confusion in the interpretation of these FNA samples.

OBJECTIVE

To propose a novel classification system for reporting salivary gland FNA samples and summarize recent progress in application of molecular and immunohistochemical markers in selected salivary gland neoplasms.

DATA SOURCES

Literature review and authors' personal practice experience.

CONCLUSIONS

The new classification system provides a more succinct, standardized interpretation of results and will ultimately assist in communication between clinicians, clinical decision making, and preoperative patient counseling. Impressive advances have been made in recent years in the understanding of molecular pathogenesis of salivary gland tumors. With the newly acquired diagnostic tools, significant improvement in diagnostic accuracy of salivary gland FNA can certainly be expected.

The landscape of gene fusions and somatic mutations in salivary gland neoplasms - Implications for diagnosis and therapy

Recent studies of the genomic landscape of salivary gland tumors have provided important insights into the molecular pathogenesis of these tumors. The most consistent alterations identified include a translocation-generated gene fusion network involving transcription factors, transcriptional coactivators, tyrosine kinase receptors, and other kinases. In addition, next-generation sequencing studies of a few subtypes of salivary neoplasms have revealed hotspot mutations in individual genes and mutations clustering to specific pathways frequently altered in cancer. Although limited, these studies have opened up new avenues for improved classification and targeted therapies of salivary gland cancers. In this review, we summarize the latest developments in this field, focusing on tumor types for which clinically important molecular data are available.

Oncogenic cAMP responsive element binding protein 1 is overexpressed upon loss of tumor suppressive miR-10b-5p and miR-363-3p in renal cancer

Renal cell carcinoma (RCC) is the most common kidney cancer in adults and has a poor prognosis. cAMP responsive element binding protein 1 (CREB1) is a proto‑oncogenic transcription factor involved in malignancies of various organs. However, its functional role(s) have not yet been elucidated in RCC. We investigated the expression pattern, function and regulation of CREB1 in RCC. CREB1 was overexpressed in the RCC tissues and cell lines. Downregulation of CREB1 inhibited RCC tumorigenesis by affecting cell proliferation, migration and apoptosis. Multiple computational algorithms predicted that the 3'‑untranslated region (3'‑UTR) of human CREB1 mRNA is a target for miR‑10b‑5p and miR‑363‑3p. Luciferase reporter assay, qPCR and western blot analysis confirmed that miR‑10b‑5p and miR‑363‑3p bind directly to the 3'‑UTR of CREB1 mRNA and inhibit mRNA and protein expression of CREB1. qPCR data also revealed a significantly lower expression of miR‑10b‑5p and miR‑363‑3p in RCC tissues. Introduction of miR‑10b‑5p and miR‑363‑3p mimics led to suppressed expression of CREB1 and inhibited cell proliferation, migration and apoptosis reduction. Taken together, we propose that CREB1 is an oncogene in RCC and that upregulation of CREB1 by loss of tumor suppressive miR‑10b‑5p and miR‑363‑3p plays an important role in the tumorigenesis of RCC.

Mastermind-Like 3 Controls Proliferation and Differentiation in Neuroblastoma

Neuroblastoma cell lines can differentiate upon treatment with retinoic acid (RA), a finding that provided the basis for the clinical use of RA to treat neuroblastoma. However, resistance to RA is often observed, which limits its clinical utility. Using a gain-of-function genetic screen, we identified an unexpected link between RA signaling and mastermind-like 3 (MAML3), a known transcriptional coactivator for NOTCH. Our findings indicate that MAML3 expression leads to the loss of activation of a subset of RA target genes, which hampers RA-induced differentiation and promotes resistance to RA. The regulatory DNA elements of this subset of RA target genes show overlap in binding of MAML3 and the RA receptor, suggesting a direct role for MAML3 in the regulation of these genes. In addition, MAML3 has RA-independent functions, including the activation of IGF1R and downstream AKT signaling via upregulation of IGF2, resulting in increased proliferation. These results demonstrate an important mechanistic role for MAML3 in proliferation and RA-mediated differentiation.

IMPLICATIONS

MAML3 coordinates transcription regulation with receptor tyrosine kinase pathway activation, shedding new light on why this gene is mutated in multiple cancers. Mol Cancer Res; 14(5); 411-22. ©2016 AACR.

Primary lung mucoepidermoid carcinoma: analysis of prognostic factors using surveillance, epidemiology and end results program

INTRODUCTION

Mucoepidermoid carcinoma (MEC) primarily occurs in salivary glands, but can also arise in other organs; however, the impact of primary location on patient prognosis is largely unknown.

METHODS

Using Surveillance, Epidemiology and End Results Program (SEER) data we investigated whether the clinical and prognostic features of MEC differed among multiple organ sites. The SEER-18 dataset from 18 cancer registries in the US between 1972 and 2012 was chosen. The common organ sites with 100 or more cases were further analyzed. Survival analysis included Log-rank tests of Kaplan-Meier curves and univariate/multivariate proportional hazard analysis.

RESULTS

A total of 7,191 MEC cases with survival data were identified in the SEER data. Major salivary gland (MSG) was the primary site in 52.9% of cases, followed by gum and other mouth (23.6%), lung (5.9%), tongue (3.4%) and others. Compared to MSG-MEC, primary lung MEC had significantly more patients with age <=70, diagnosis in 2002 and earlier, distant stage, undetermined grade and nonsurgical treatment. Primary lung MEC, older age, male gender, early year of diagnosis, distant stage, high histologic grade and radiation alone were significantly associated with poor 5-year disease-specific survival rate. Among patients with primary lung MEC, univariate analysis demonstrated that those with main bronchus or upper lobe primary sites had significantly decreased 5-year disease-specific survival rate.

CONCLUSIONS

This study suggests that there is a major difference in prognosis of MEC among primary sites. Primary lung MEC might have poor prognosis over MSG-MEC.

A unifying gene signature for adenoid cystic cancer identifies parallel MYB-dependent and MYB-independent therapeutic targets

MYB activation is proposed to underlie development of adenoid cystic cancer (ACC), an aggressive salivary gland tumor with no effective systemic treatments. To discover druggable targets for ACC, we performed global mRNA/miRNA analyses of 12 ACC with matched normal tissues, and compared these data with 14 mucoepidermoid carcinomas (MEC) and 11 salivary adenocarcinomas (ADC). We detected a unique ACC gene signature of 1160 mRNAs and 22 miRNAs. MYB was the top-scoring gene (18-fold induction), however we observed the same signature in ACC without detectable MYB gene rearrangements. We also found 4 ACC tumors (1 among our 12 cases and 3 from public databases) with negligible MYB expression that retained the same ACC mRNA signature including over-expression of extracellular matrix (ECM) genes. Integration of this signature with somatic mutational analyses suggests that NOTCH1 and RUNX1 participate with MYB to activate ECM elements including the VCAN/HAPLN1 complex. We observed that forced MYB-NFIB expression in human salivary gland cells alters cell morphology and cell adhesion in vitro and depletion of VCAN blocked tumor cell growth of a short-term ACC tumor culture. In summary, we identified a unique ACC signature with parallel MYB-dependent and independent biomarkers and identified VCAN/HAPLN1 complexes as a potential target.

Gene expression profiling analysis of CRTC1-MAML2 fusion oncogene-induced transcriptional program in human mucoepidermoid carcinoma cells

Background

Mucoepidermoid carcinoma (MEC) arises from multiple organs and accounts for the most common types of salivary gland malignancies. Currently, patients with unresectable and metastatic MEC have poor long-term clinical outcomes and no targeted therapies are available. The majority of MEC tumors contain a t(11;19) chromosomal translocation that fuses two genes, CRTC1 and MAML2, to generate the chimeric protein CRTC1-MAML2. CRTC1-MAML2 displays transforming activity in vitro and is required for human MEC cell growth and survival, partially due to its ability to constitutively activate CREB-mediated transcription. Consequently, CRTC1-MAML2 is implicated as a major etiologic molecular event and a therapeutic target for MEC. However, the molecular mechanisms underlying CRTC1-MAML2 oncogenic action in MEC have not yet been systematically analyzed. Elucidation of the CRTC1-MAML2-regulated transcriptional program and its underlying mechanisms will provide important insights into MEC pathogenesis that are essential for the development of targeted therapeutics.

Methods

Transcriptional profiling was performed on human MEC cells with the depletion of endogenous CRTC1-MAML2 fusion or its interacting partner CREB via shRNA-mediated gene knockdown. A subset of target genes was validated via real-time RT-PCR assays. CRTC1-MAML2-perturbed molecular pathways in MEC were identified through pathway analyses. Finally, comparative analysis of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles was carried out to assess the contribution of CREB in mediating CRTC1-MAML2-induced transcription.

Results

A total of 808 differentially expressed genes were identified in human MEC cells after CRTC1-MAML2 knockdown and a subset of known and novel fusion target genes was confirmed by real-time RT-PCR. Pathway Analysis revealed that CRTC1-MAML2-regulated genes were associated with network functions that are important for cell growth, proliferation, survival, migration, and metabolism. Comparison of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles revealed common and distinct genes regulated by CRTC1-MAML2 and CREB, respectively.

Conclusion

This study identified a specific CRTC1-MAML2-induced transcriptional program in human MEC cells and demonstrated that CRTC1-MAML2 regulates gene expression in CREB-dependent and independent manners. Our data provide the molecular basis underlying CRTC1-MAML2 oncogenic functions and lay a foundation for further functional investigation of CRTC1-MAML2-induced signaling in MEC initiation and maintenance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1827-3) contains supplementary material, which is available to authorized users.

Tumors of the lacrimal gland

Tumors of the lacrimal gland comprise a wide spectrum, of which the most common demonstrate epithelial and lymphoid differentiation. The diagnosis of lacrimal gland tumors depends primarily on histological evaluation, as do the choice of treatment and prognosis. For some lacrimal gland neoplasms, such as adenoid cystic carcinoma, the outlook is grave. Optimal treatment for several lacrimal gland tumors is also a matter of controversy. However, recent progress has been made in the molecular and genetic understanding of tumorigenesis for such lesions. This article presents an overview of the histopathology of lacrimal gland tumors, together with their epidemiological features, clinical characteristics, and treatment strategies.

Dysregulated CRTC1 activity is a novel component of PGE2 signaling that contributes to colon cancer growth

First identified as a dedicated CREB (cAMP response element-binding protein) co-activator, CRTC1 (CREB-regulated transcription co-activator 1) has been widely implicated in various neuronal functions because of its predominant expression in the brain. However, recent evidences converge to indicate that CRTC1 is aberrantly activated in an expanding number of adult malignancies. In this study, we provide strong evidences of enhanced CRTC1 protein content and transcriptional activity in mouse models of sporadic (APC(min/+) mice) or colitis-associated colon cancer azoxymethane/dextran sulfate sodium (AOM/DSS-treated mice), and in human colorectal tumors specimens compared with adjacent normal mucosa. Among signals that could trigger CRTC1 activation during colonic carcinogenesis, we demonstrate that treatment with cyclooxygenase 2 (COX2) inhibitors reduced nuclear CRTC1 active form levels in colonic tumors of APC(min/+) or AOM/DSS mice. In accordance, prostaglandins E2 (PGE2) exposure to human colon cancer cell lines promoted CRTC1 dephosphorylation and parallel nuclear translocation, resulting in enhanced CRTC1 transcriptional activity, through EP1 and EP2 receptors signaling and consecutive calcineurin and protein kinase A activation. In vitro CRTC1 loss of function in colon cancer cell lines was associated with reduced viability and cell division rate as well as enhanced chemotherapy-induced apoptosis on PGE2 treatment. Conversely, CRTC1 stable overexpression significantly increased colonic xenografts tumor growth, therefore demonstrating the role of CRTC1 signaling in colon cancer progression. Identification of the transcriptional program triggered by enhanced CRTC1 expression during colonic carcinogenesis, revealed some notable pro-tumorigenic CRTC1 target genes including NR4A2, COX2, amphiregulin (AREG) and IL-6. Finally, we demonstrate that COX2, AREG and IL-6 promoter activities triggered by CRTC1 are dependent on functional AP1 and CREB transcriptional partners. Overall, our study establishes CRTC1 as new mediator of PGE2 signaling, unravels the importance of its dysregulation in colon cancer and strengthens its use as a bona fide cancer marker.

Discovery of novel adenylyl cyclase inhibitor by cell-based screening

We screened 2400 compounds to find novel inhibitors of the adenylyl cyclase (AC)-protein kinase A (PKA)-cAMP response-element-binding protein (CREB) signaling pathway (AC/PKA/CREB pathway). Using a multistep cell-based screening system employing split luciferase technique, we narrowed down the candidates effectively from 2400 chemical compounds and identified a novel AC inhibitor (compound 1). Since dysregulation of the AC/PKA/CREB pathway is known to cause diseases not only in the nervous system but also in other organs, compound 1 is expected to be developed as a medicine for these diseases.

Thymic Mucoepidermoid Carcinoma

Thymic mucoepidermoid carcinoma (TMEC) is a vanishingly rare entity that usually presents as low to intermediate grade MEC and carries a better prognosis when compared with other poorly differentiated thymic carcinomas. The recently described fusions, t(11;19)(q21;p13) CREB (cAMP response element-binding protein)-regulated transcription coactivator 1 and MAML2, mastermind-like gene 2 (CRTC1-MAML2) and t(11:15)(q21;q26) CRTC3-MAML2 characterize a considerable proportion of MEC examples arising from a variety of anatomical sites. Recent data point out that the aberrant proteins produced by this fusion drive oncogenesis by disrupting the cAMP/CREB and NOTCH1 pathways. To date, only 2 TMEC cases have been reported to have MAML2 rearrangements, a feature that was found to be absent in TMEC mimics. These findings led the authors to recommend this test as a diagnostic tool in the differential diagnosis for thymic carcinoma. Herein, we present a case of TMEC arising in a 58-year-old woman, which was predominantly cystic with intracystic papillary formations composed of a mixture of mucinous cells and intermediate/epidermoid eosinophilic cells. This case was negative for CTCR1-MAML2 and CTCR3-MAML2 fusion transcripts by reverse transcriptase polymerase chain reaction and lacked a MAML2 rearrangement by fluorescence in situ hybridization. We report a CTCR1/3-MAML2 fusion and MAML2 rearrangement–negative TMEC, indicating that a different molecular pathway must be involved in the generation of these tumors. The possibility of fusion-negative TMEC should be taken into consideration in the differential diagnosis of a thymic carcinoma.

Role of LKB1-CRTC1 on glycosylated COX-2 and response to COX-2 inhibition in lung cancer

BACKGROUND

Cyclooxygenase-2 (COX-2) directs the synthesis of prostaglandins including PGE-2 linking inflammation with mitogenic signaling. COX-2 is also an anticancer target, however, treatment strategies have been limited by unreliable expression assays and by inconsistent tumor responses to COX-2 inhibition.

METHODS

We analyzed the TCGA and Director's Challenge lung cancer datasets (n = 188) and also generated an LKB1-null lung cancer gene signature (n = 53) to search the Broad Institute/Connectivity-MAP (C-MAP) dataset. We performed ChIP analyses, real-time polymerase chain reaction, immunoblotting, and drug testing of tumor cell lines (n = 8) and primary lung adenocarcinoma surgical resections (n = 13).

RESULTS

We show that COX-2 is a target of the cAMP/CREB coactivator CRTC1 signaling pathway. In addition, we detected a correlation between LKB1 status, CRTC1 activation, and presence of glycosylated, but not inactive hypoglycosylated COX-2 in primary lung adenocarcinoma. A search of the C-MAP drug database discovered that all high-ranking drugs positively associated with the LKB1-null signature are known CRTC1 activators, including forskolin and six different PGE-2 analogues. Somatic LKB1 mutations are present in 20.0% of lung adenocarcinomas, and we observed growth inhibition with COX-2 inhibitors in LKB1-null lung cancer cells with activated CRTC1 as compared with LKB1-wildtype cells (NS-398, P = .002 and Niflumic acid, P = .006; two-tailed t test).

CONCLUSION

CRTC1 activation is a key event that drives the LKB1-null mRNA signature in lung cancer. We also identified a positive feedback LKB1/CRTC1 signaling loop for COX-2/PGE2 regulation. These data suggest a role for LKB1 status and glycosylated COX-2 as specific biomarkers that provide a framework for selecting patients for COX-2 inhibition studies.