In Vitro Carbon Ion Beam and Gemcitabine Chemoradiation in a Mucoepidermoid Carcinoma Cell Line.

BACKGROUND/AIM: To determine the interaction of gemcitabine in chemoradiotherapy with heavy carbon ions in vitro in a mucoepidermoid carcinoma (MEC) cell line. MATERIALS AND METHODS: The human lymphatic MEC metastasis cell line NCI-H292 was used. The cells were treated with photons, carbon ions, and gemcitabine. Survival fractions (SF), apoptosis, and cell cycle progression were analyzed. A paired two-sided t-test was used. Significance was defined as p<0.05. RESULTS: Cell proliferation assays showed a significant reduction in SF for combined photon chemoradiation versus photons only. The linear-quadratic fits of combined therapy with carbon ion dose of 0 to 2.5 Gy led to reductions of mean 15% in SF. The LD50 (lethal radiation dose required to reduce cell survival by 50%) for carbon ions only was 0.7 Gy and for carbon ions with gemcitabine 0.6 Gy. The LD50 for photons (with gemcitabine) was 2.8 Gy (2.0 Gy) and for carbon ions (with gemcitabine) 0.7 Gy (0.6 Gy), resulting in a relative biological effectiveness at 10% cell survival (RBE10) of 3.0 (2.7). Carbon ions and photons reduced S phase and increased G2/M phase cell distribution. Isolated treatment with gemcitabine as well as combination with photons led to prolonged S phase transit, whereas combined treatment with carbon ions led to early accumulation in G2/M phase. A significant increase in the sub-G1 population as a hint of relevant number of apoptotic cells was not observed. CONCLUSION: Gemcitabine showed radiosensitizing effects in combination with photons. The combination of gemcitabine and carbon ions had independent additive effects. Carbon ions only had a RBE10 of 3.0, compared to photons only. The combination of gemcitabine, photon, and carbon ions in patients with MEC seems promising and warrants further investigation.

Mucoepidermoid carcinoma cured by a combination of high-frequency snare and photodynamic therapy: A case report.

Mucoepidermoid carcinoma (MEC) is a rare salivary gland tumor, accounting for 0.2% of all lung tumors. The standard treatment for MEC of the primary bronchus is surgery, although intraluminal bronchoscopic treatment has recently become an option. A 68-year-old man presented with an asymptomatic bronchial tumor in the right intermediate bronchus. The tumor was resected using a high-frequency snare (HFS) during bronchoscopy, and the specimen was pathologically diagnosed as low-grade MEC. A residual lesion was detected in the resected area by autofluorescence imaging. The tumor appeared to be localized within the subepithelial layer without metastases, and photodynamic therapy (PDT) was performed as a local treatment. The patient had no recurrence for 18 months. PDT is effective and safe for patients with centrally located early-stage lung cancer, but there are few reports of its use for rare tumors, such as MEC. In this case, PDT allowed for local control and avoided surgery, including bronchoplasty, for MEC. Combined treatment of tumor reduction by HFS and PDT of the residual lesion may be an optimal treatment for MEC of the bronchus.

Immunotherapy combined with chemotherapy in the treatment for rare primary mucoepidermoid carcinoma of the liver: a case report.

Primary mucoepidermoid carcinoma of the liver (PMCL) is rare in the hepatic system, with no standard treatment and poor prognosis with a median overall survival of only 120 days. PMCL with immunotherapy has not been reported yet. Here, we present a case of PMCL treated by immunotherapy and chemotherapy. A 64-year-old male with PMCL underwent partial right hepatectomy and liver lesion resection on 19 June 2020. Two months later, the chest computed tomography indicated the presence of multiple nodules in both lungs with higher tumor markers. Considering the presence of a tumor metastasis, the patient received four courses of immunotherapy plus mGEMOX chemotherapy from 8 September 2020. The patient tolerated the combined therapy well, with red moles on the face and chest which were considered as grade 1 reactive cutaneous capillary endothelial proliferation. He also had grade 2 thrombocytopenia and leucopenia after the first course of chemotherapy, but no neutropenia, fatigue, vomiting or diarrhea. However, his disease progressed. The patient refused further treatment and died on 20 April 2021. The overall survival time after diagnosis was 301 days. We describe here the first case report on immunotherapy treatment for PMCL. That suggested immunotherapy combined with chemotherapy may be an option after a hepatic lobectomy for PMCL.

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.

Prolonged response to checkpoint inhibitor therapy in two metastatic mucoepidermoid salivary gland carcinoma cases: a research report.

Salivary gland tumors (SGTs) are heterogeneous tumors that range from benign masses to aggressive high-grade carcinomas with distant metastatic potential and limited response to chemotherapy. Mucoepidermoid carcinoma (MEC) accounts for 10% of SGTs and has a poor prognosis. In this research report, we describe two cases of metastatic high-grade MECs with prolonged response to immune checkpoint inhibitor pembrolizumab. Case 1 presented with a left neck mass, and biopsy of the parotid mass revealed MEC. The patient underwent surgical resection and adjuvant chemoradiation therapy for stage IVB disease. Post-treatment, she was found to have brain and spinal metastases and was placed on pembrolizumab. Case 2 presented with a left neck mass, and biopsy of the right parotid gland revealed MEC. Further staging demonstrated metastatic disease in the lungs, and he was placed on pembrolizumab. Both cases of MEC demonstrated prolonged extracranial responses to pembrolizumab. Although both cases reported little to no PD-L1 expression, these results demonstrate immunotherapy efficacy in advanced/metastatic MEC.

HER-2 Neu gene: A valuable therapeutic target in metastatic mucoepidermoid carcinoma.

INTRODUCTION: Salivary gland neoplasms (SGNs) respond poorly to the traditional chemotherapy agents limiting the availability of systemic treatment options in the metastatic setting. The recent identification of actionable molecular targets in SGNs has led to the evaluation of targeted therapies in non-approved advanced SGNs. CASE REPORT: We present the case of an elderly male with HER-2 Neu overexpressing metastatic mucoepidermoid carcinoma (MEC) who demonstrated a prompt and sustained disease response to targeted therapies directed against HER-2 Neu with long survival interrupted by hepatoxicity to Trastuzumab emtansine (TDM-1) treatment.Management and Outcome: The patient was started on Trastuzumab and Pertuzumab on a clinical trial and resulted in an objective improvement sustained over 3 years. Following the disease progression, TDM-1 was started with a response until the patient developed severe hepatotoxicity as an adverse effect of TDM-1 therapy resulting in its discontinuation. Close follow-up post-treatment-discontinuation demonstrated continued clinical improvement until 6 months, when the patient developed brain metastasis. He passed away a few months later in hospice care. DISCUSSION: The metastatic MEC in our patient overexpressed HER-2 Neu. Owing to Trastuzumab and Pertuzumab response, Trastuzumab emtansine (TDM-1) was initiated on a compassionate basis which further extended the survival but had to be terminated owing to adverse effects. Given the paucity of data on targeted therapies in the treatment of metastatic SGNs and the safety, tolerability, and efficacy of TDM-1 therapy among the elderly, further studies are warranted to answer these important questions and to identify eligible patients for this novel treatment option.

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.

[Long-term follow-up of a multimodally managed pulmonary mucoepidermoid carcinoma in a cat]. / Langzeitstudie einer multimodalen Behandlung eines mukoepidermoiden Lungenkarzinoms bei einer Katze.

INTRODUCTION: The present case describes the treatment of a mucoepidermoid carcinoma in a 13-year-old female sterilized European domestic cat, using lung lobectomy and -accompanying mitoxantrone chemotherapy. Six, 14, 19 and 27 months after the initial treatment tomodensitometric and radiographic examinations showed no abnormalities. However, the cat had to be euthanized 27 months after the lung lobectomy due to a soft tissue sarcoma in the interscapular area.

INTRODUCTION: Ce cas décrit un carcinome mucoépidermoïde chez un chat européen femelle stérilisée de 13 ans, entité non rapportée jusqu'alors chez cette espèce, pris en charge par lobectomie pulmonaire et chimiothérapie adjuvante avec de la mitoxantrone. L'examen tomodensitométrique et les clichés radiographiques, réalisés respectivement 6 mois, 14, 19 mois, et 27 mois après la chirurgie, ne mettaient en évidence aucune anomalie. Cependant, vingt-sept mois après l'intervention chirurgicale, une euthanasie est réalisée suite à l'aggravation en quelques mois d'un sarcome des tissus mous en région inter-scapulaire.

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.

Targeting X chromosome-linked inhibitor of apoptosis protein in mucoepidermoid carcinoma of the head and neck: A novel therapeutic strategy using nitidine chloride.

Nitidine chloride (NC) was recently reported to exhibit a wide range of pharmacological properties for several diseases, including cancer. Here we report for the first time that NC is a potential therapeutic agent for mucoepidermoid carcinoma (MEC) occurring in the head and neck because it suppresses X chromosome-linked inhibitor of apoptosis protein (XIAP) in human MEC in vitro and in vivo. The antitumor effects of NC were evaluated by trypan blue exclusion assay, western blotting, live/dead assay, 4',6-diamidino-2-phenylindole (DAPI) staining, human apoptosis antibody array, immunofluorescence staining, immunohistochemistry, small interfering RNA assay, transient transfection of XIAP overexpression vector, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and histopathological examination of organs. NC inhibited cell viability and induced caspase-dependent apoptosis in vitro. A human apoptosis antibody array assay showed that XIAP is suppressed by NC treatment. XIAP was overexpressed in oral squamous cell carcinoma (OSCC) tissues that arose from the head and neck, and high XIAP expression was correlated with poor prognosis in OSCC patients. XIAP depletion significantly increased apoptosis, and ectopic XIAP overexpression attenuated the apoptosis induced by NC treatment. NC suppressed tumor growth in vivo at a dosage of 5 mg/kg/day. The number of TUNEL-positive cells increased and the protein expression of XIAP was consistently downregulated in NC-treated tumor tissues. In addition, NC caused no histopathological changes in the liver or kidney. These findings provide new insights into the mechanism of action underlying the anticancer effects of NC and demonstrate that NC is a promising therapeutic agent for the treatment of human MEC of the head and neck. KEY MESSAGES: • Nitidine chloride induces caspase-dependent apoptosis in MEC of the head and neck. • High XIAP expression correlates with poor prognosis of OSCC patients. • Nitidine chloride suppresses tumor growth in vivo without any systemic toxicities. • Targeting XIAP is a novel chemotherapeutic strategy for MEC of the head and neck.

Activating BRAF mutation in sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland: two case reports and review of the literature.

BACKGROUND: Sclerosing mucoepidermoid carcinoma with eosinophilia is a rare form of thyroid carcinoma. The underlying molecular mechanisms of sclerosing mucoepidermoid carcinoma with eosinophilia tumorigenesis remain unknown. CASE PRESENTATION: We present two cases of sclerosing mucoepidermoid carcinoma with eosinophilia, both with a concurrent papillary thyroid carcinoma. Patient 1, a 70-year-old Caucasian woman, presented with sclerosing mucoepidermoid carcinoma with eosinophilia with distant renal metastasis and coexisting papillary thyroid carcinoma. Patient 2, a 74-year-old Caucasian woman with a remote history of thyroid cancer treated with thyroidectomy, presented with locoregionally invasive sclerosing mucoepidermoid carcinoma with eosinophilia and recurrent papillary thyroid carcinoma in the thyroid bed. BRAF mutation studies were performed on the sclerosing mucoepidermoid carcinoma with eosinophilia tumors. In both cases, sclerosing mucoepidermoid carcinoma with eosinophilia was positive for the BRAF V600E mutation by polymerase chain reaction. Patient 1 is the first reported case of sclerosing mucoepidermoid carcinoma with eosinophilia with renal metastasis, to the best of our knowledge. CONCLUSIONS: Our findings suggest, for the first time, to our knowledge, involvement of the RAS-RAF-MEK-ERK signaling pathway in the pathogenesis of sclerosing mucoepidermoid carcinoma with eosinophilia. Thus, BRAF inhibitors may prove to be a useful targeted medical therapy in the treatment of a subset of patients with aggressive sclerosing mucoepidermoid carcinoma with eosinophilia tumors who exhibit BRAF activating mutation.

Challenges in diagnosis of pulmonary mucoepidermoid carcinoma: A case report.

RATIONALE: Pulmonary mucoepidermoid carcinomas (PMECs) of the lung are rare malignant tumors. Despite progresses in examinations, the tumor represents a diagnostic challenge for pathologists and clinical physicians. Here, we present a patient who was eventually diagnosed with PMEC by the bronchoscopic examinations conducted three times. PATIENT CONCERNS: We present the case of a 41-year-old female who was initially diagnosed with pulmonary pleomorphic adenoma (PPA) with a 68 × 82 mm mass and nodules in her lung and eventually diagnosed with PMEC. DIAGNOSES: Based on histopathology, immunohistology, and imaging studies, the patient was diagnosed with PMEC (pT4N2M1). INTERVENTIONS: The patient received first-line systemic chemotherapy regime (gemcitabine combined with carboplatin). OUTCOMES: The patient received 2 cycles of chemotherapy. Based on the response evaluation criteria in solid tumor, she achieved partial response, and the mass was distinctly decreased from 68 × 22 mm to 41 × 17 mm. LESSONS: This case presents a rare PMEC overlapping with PPA, based on histological findings, suggesting that besides imaging studies and laboratory examinations, multiple biopsies and ThinPrep cytology tests are necessary to obtain an accurate diagnosis. The patient showed positive response to chemotherapy.

Heme Oxygenase-1 is a Key Molecule Underlying Differential Response of TW-37-Induced Apoptosis in Human Mucoepidermoid Carcinoma Cells.

TW-37 is a small-molecule inhibitor of Bcl-2 family proteins, which can induce anti-cancer activities in various types of cancer. In the current study, we investigated the potential molecular mechanism underlying the differential response to TW-37-induced apoptosis in two human mucoepidermoid carcinoma (MEC) cell lines. The differential response and underlying molecular mechanism of human MEC cells to TW-37 was evaluated by trypan blue exclusion assay, western blotting, 4', 6-diamidino-2-phenylindole staining, annexin V/propidium iodide double staining, analysis of the sub-G1 population, human apoptosis array, and measurements of intracellular reactive oxygen species (ROS). TW-37 decreased cell viability and induced apoptosis in YD-15 cells, but not in MC3 cells. Proteome profiling using a human apoptosis array revealed four candidate proteins and of these, heme oxygenase-1 (HO-1) was mainly related to the differential response to TW-37 of YD-15 and MC3 cells. TW-37 also led to a significant increase in intracellular levels of ROS in YD-15 cells, which is associated with apoptosis induction. The ectopic expression of HO-1 recovered YD-15 cells from TW-37-induced apoptosis by reducing intracellular levels of ROS. The expression of HO-1 was reduced through both transcriptional and post-translational modification during TW-37-mediated apoptosis. We conclude that HO-1 is a potential indicator to estimate response to TW37-induced apoptosis in human MEC.

Norcantharidin Suppresses YD-15 Cell Invasion Through Inhibition of FAK/Paxillin and F-Actin Reorganization.

Norcantharidin (NCTD), a demethylated derivative of cantharidin, has been reported to exhibit activity against various types of cancers. However, the anti-invasive effects of NCTD and its molecular mechanism in human mucoepidermoid carcinoma (MEC) remain incompletely elucidated. Clonogenic, wound healing, invasion, zymography, western blotting and immunocytochemistry assays were performed in YD-15 cells to investigate the anti-invasive effect of NCTD and its molecular mechanism of action. The inhibitory effects of NCTD on invasiveness were compared with those of a novel focal adhesion kinase (FAK) kinase inhibitor, PF-562271. NCTD markedly suppressed the colony formation, migration, and invasion of YD-15 cells as well as the activities of MMP-2 and MMP-9. It disrupted F-actin reorganization through suppressing the FAK/Paxillin axis. Moreover, NCTD exhibited a powerful anti-invasive effect compared with that of PF-562271 in YD-15 cells. Collectively, these results suggest that NCTD has a potential anti-invasive activity against YD-15 cells. This study may clarify the impact of NCTD on migration and invasion of human MEC cells.

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.

Ablation of Cancer Stem Cells by Therapeutic Inhibition of the MDM2-p53 Interaction in Mucoepidermoid Carcinoma.

PURPOSE: Unique cells characterized by multipotency, self-renewal, and high tumorigenic potential have been recently discovered in mucoepidermoid carcinomas. These cells are defined by high aldehyde dehydrogenase activity and high CD44 expression (ALDHhighCD44high) and function as cancer stem cells (CSC). It has been recently shown that p53 regulates cell differentiation, suggesting that induction of p53 by therapeutic blockade of the MDM2-p53 interaction may constitute a novel strategy to ablate CSCs. Here, we evaluated the effect of a small-molecule inhibitor of MDM2-p53 interaction (MI-773) on the fraction of CSCs in mucoepidermoid carcinoma. EXPERIMENTAL DESIGN: Human mucoepidermoid carcinoma cells (UM-HMC-1,-3A,-3B) were used to assess the effect of MI-773 on cell survival, cell cycle, fraction of CSCs, and expression of p53, p21, MDM2, and Bmi-1 (key regulator of self-renewal). Mice bearing xenograft tumors generated with these mucoepidermoid carcinoma cells were treated with MI-773 to determine the effect of MDM2-p53 inhibition on CSCs in vivo. RESULTS: MDM2 is highly expressed in human mucoepidermoid carcinoma tissues. MI-773 induced expression of p53 and its downstream targets p21 and MDM2, caused G1 cell-cycle arrest, and induced mucoepidermoid carcinoma tumor cell apoptosis in vitro. Importantly, a marked decrease in expression of Bmi-1 and in the fraction of ALDHhighCD44high (CSCs) was caused by MI-773 in vitro and in mice harboring mucoepidermoid carcinoma xenografts. CONCLUSIONS: Collectively, these data demonstrate that MI-773 reduces the fraction of CSCs, suggesting that patients with mucoepidermoid carcinoma might benefit from therapeutic inhibition of the MDM2-p53 interaction.

Interfering with bromodomain epigenome readers as therapeutic option in mucoepidermoid carcinoma.

PURPOSE: Emerging evidence indicates that bromodomains comprise a conserved class of epigenome readers involved in cancer development and inflammation. Bromodomains are associated with epigenetic modifications of gene transcription through interactions with lysine residues of histone tails. Particularly, the bromodomain and extra-terminal domain (BET) family member BRD4 has been found to be involved in the control over oncogenes, including c-MYC, and in the maintenance of downstream inflammatory processes. The objective of this study was to evaluate the effect of pharmacologically displacing BRD4 in mucoepidermoid carcinoma (MEC) cells. METHODS: We assessed the presence of BRD4 levels in a panel of human MEC tissue samples in conjunction with histological grading and clinical information. In vitro studies were carried out using human MEC-derived cell lines. The BET inhibitor iBET762 was administered to MEC cells to assess the impact of disrupted BRD4 signaling on colony forming capacities and cell cycle status. The activation of cellular senescence induced by iBET762 was determined by immunohistochemical staining for p16ink4. Flow cytometry was used to identify populations of cancer stem cells in MEC-derived cell lines. RESULTS: We found that primary human MECs and MEC-derived cell lines are endowed with high BRD4 expression levels compared to those in normal salivary glands. We also found that, by displacing BRD4 from chromatin using the BET inhibitor iBET762, MEC cells lose their colony forming capacities and undergo G1 cell cycle arrest and senescence. Finally, we found that targeted displacement of BRD4 from chromatin results in depletion of cancer stem cells from the overall MEC cell populations. CONCLUSIONS: Our findings indicate that bromodomain-mediated gene regulation constitutes an epigenetic mechanism that is deregulated in MEC cells and that the use of BET inhibitors may serve as a feasible therapeutic strategy to manage MECs.