Characterization of tumorigenic cell lines from the recurrence and lymph node metastasis of a human salivary mucoepidermoid carcinoma

Establishment and characterization of cMYB-expressing human salivary adenoid cystic carcinoma cell lines (UM-HACC-14, UM-HACC-6) and matching patient-derived xenograft model (UM-PDX-HACC-14)

OBJECTIVE

Limited availability of authentic human adenoid cystic carcinoma (ACC) cell lines has hindered progress in understanding mechanisms underpinning the biology of this disease and the development of safe and effective therapies.

STUDY DESIGN

Surgical human ACC specimens (UM-HACC-6, UM-HACC-14) were dissociated into single cell suspensions and cultured in fibronectin-coated flasks. Alternatively, tumor fragments were transplanted subcutaneously into female immunodeficient (SCID) mice to establish patient-derived xenograft tumors (PDX; UM-PDX-HACC-14).

RESULTS

Both ACC cell lines showed continuous growth in monolayers for over 100 passages. Total RNA-Seq, RT-PCR, and FISH analysis revealed that both are MYB-NFIB fusion negative. Western blots revealed passage-dependent expression of E-Cadherin, PCNA, p63, phospho-c-MYB, and NFIB. Both, UM-HACC-14 and UM-HACC-6 cells exhibited tumorigenic potential when injected orthotopically into mouse submandibular glands.

CONCLUSION

UM-HACC-14, patient-matching UM-PDX-HACC-14, and the UM-HACC-6 cell line are new, authenticated preclinical models of ACC that are well suited for mechanistic and developmental therapeutics studies.

Molecular Aspects of Mucoepidermoid Carcinoma and Adenoid Cystic Carcinoma of the Salivary Gland

BACKGROUND

Salivary gland tumors (SGTs) are rare and highly heterogeneous lesions, making diagnosis a challenging activity. In addition, the small number of studies and samples evaluated difficults the determination of prognosis and diagnosis. Despite the solid advances achieved by research, there is still an intense need to investigate biomarkers for diagnosis, prognosis and that explain the evolution and progression of SGTs.

METHODS

We performed a comprehensive literature review of the molecular alterations focusing on the most frequent malignant SGTs: mucoepidermoid carcinoma and adenoid cystic carcinoma.

RESULTS

Due to the importance of biomarkers in the tumorigenenic process, this review aimed to address the mechanisms involved and to describe molecular and biomarker pathways to better understand some aspects of the pathophysiology of salivary gland tumorigenesis.

CONCLUSIONS

Molecular analysis is essential not only to improve the diagnosis and prognosis of the tumors but also to identify novel driver pathways in the precision medicine scenario.

Effects of bisphenol A on murine salivary glands and human tumor cell lines

Bisphenol A (BPA) is an endocrine-disrupting chemical with a potential role in endocrine cancers. However, the effects of BPA on the salivary glands have been barely explored. We investigated the impact of in vivo sub-chronic exposure to BPA and its in vitro effects on human salivary gland mucoepidermoid carcinoma cell lines. Male and female mice were exposed to BPA (30 mg/kg/day). Sublingual and submandibular salivary glands from an estrogen-deficiency model were also analyzed. BPA concentration in salivary glands was evaluated by gas chromatography coupled to ion trap mass spectrometry. Immunohistochemical analysis using anti-p63 and anti-α-SMA antibodies was performed on mouse salivary gland tissues. Gene expression of estrogen receptors alpha and beta, P63 and α-SMA was quantified in mouse salivary gland and/or mucoepidermoid (UM-HMC-1 and UM-HMC-3A) cell lines. Cell viability, p63 and Ki-67 immunostaining were evaluated in vitro. BPA disrupted the tissue architecture of the submandibular and sublingual glands, particularly in female mice, and increased the expression of estrogen receptors and p63, effects that were accompanied by significant BPA accumulation in these tissues. Conversely, ovariectomy slightly impacted BPA-induced morphological changes. In vitro, BPA did not affect the proliferation of neoplastic cells, but augmented the expression of p63 and estrogen receptors. The present data highlight a potential harmful effect of BPA on salivary gland tissues, particularly in female mice, and salivary gland tumor cells. Our findings suggest that estrogen-dependent pathways may orchestrate the effects of BPA in salivary glands.

Salivary gland cancer organoids are valid for preclinical genotype-oriented medical precision trials

Salivary gland cancers (SGCs) are heterogeneous tumors, and precision oncology represents a promising therapeutic approach; however, its impact on SGCs remains obscure. This study aimed to establish a translational model for testing molecular-targeted therapies by combining patient-derived organoids and genomic analyses of SGCs. We enrolled 29 patients, including 24 with SGCs and 5 with benign tumors. Resected tumors were subjected to organoid and monolayer cultures, as well as whole-exome sequencing. Organoid and monolayer cultures of SGCs were successfully established in 70.8% and 62.5% of cases, respectively. Organoids retained most histopathological and genetic profiles of their original tumors. In contrast, 40% of the monolayer-cultured cells did not harbor somatic mutations of their original tumors. The efficacy of molecular-targeted drugs tested on organoids depended on their oncogenic features. Organoids recapitulated the primary tumors and were useful for testing genotype-oriented molecular targeted therapy, which is valuable for precision medicine in patients with SGCs.

Establishment of Mucoepidermoid Carcinoma Cell Lines from Surgical and Recurrence Biopsy Specimens

Patients with advanced/recurrent mucoepidermoid carcinoma (MEC) have a poor prognosis. This study aimed to establish and characterize human mucoepidermoid carcinoma cell lines from the initial surgical specimen and biopsy specimen upon recurrence from the same patient to provide a resource for MEC research. MEC specimens from the initial surgical procedure and biopsy upon recurrence were used to establish cell lines. The established cell lines were cytogenetically characterized using multi-color fluorescence in situ hybridization and detection, and the sequence of the CRTC1-MAML2 chimeric gene was determined. Furthermore, the susceptibility of head and neck mucoepidermoid carcinoma to standard treatment drugs such as cisplatin, 5-fluorouracil, and cetuximab was investigated. We successfully established unique MEC cell lines, AMU-MEC1, from an initial surgical specimen and AMU-MEC1-R1 and AMU-MEC1-R2 from the recurrent biopsy specimen in the same patient. These cell lines exhibited epithelial morphology and developed in vitro-like cobblestones. They shared eight chromosomal abnormalities, including der(19)ins(19;11)(p13;?), which resulted in a chimeric CRTC1-MAML2 gene, indicating the same origin of the cell lines. The susceptibility of all cell lines to cisplatin and 5-fluorouracil was low. Interestingly, EGFR dependency for cell growth decreased in AMU-MEC-R1 and AMU-MEC-R2 but was retained in AMU-MEC1. These cytogenetic and biochemical findings suggest that the established cell lines can be used to investigate the disease progression mechanisms and develop novel therapeutics for MEC.

Establishment of experimental salivary gland cancer models using organoid culture and patient-derived xenografting

Purpose

Depending on its histological subtype, salivary gland carcinoma (SGC) may have a poor prognosis. Due to the scarcity of preclinical experimental models, its molecular biology has so far remained largely unknown, hampering the development of new treatment modalities for patients with these malignancies. The aim of this study was to generate experimental human SGC models of multiple histological subtypes using patient-derived xenograft (PDX) and organoid culture techniques.

Methods

Tumor specimens from surgically resected SGCs were processed for the preparation of PDXs and patient-derived organoids (PDOs). Specimens from SGC PDXs were also processed for PDX-derived organoid (PDXO) generation. In vivo tumorigenicity was assessed using orthotopic transplantation of SGC organoids. The pathological characteristics of each model were compared to those of the original tumors using immunohistochemistry. RNA-seq was used to analyze the genetic traits of our models.

Results

Three series of PDOs, PDXs and PDXOs of salivary duct carcinomas, one series of PDOs, PDXs and PDXOs of mucoepidermoid carcinomas and PDXs of myoepithelial carcinomas were successfully generated. We found that PDXs and orthotopic transplants from PDOs/PDXOs showed similar histological features as the original tumors. Our models also retained their genetic traits, i.e., transcription profiles, genomic variants and fusion genes of the corresponding histological subtypes.

Conclusion

We report the generation of SGC PDOs, PDXs and PDXOs of multiple histological subtypes, recapitulating the histological and genetical characteristics of the original tumors. These experimental SGC models may serve as a useful resource for the development of novel therapeutic strategies and for investigating the molecular mechanisms underlying the development of these malignancies.

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.

Regulation of MMP9 transcription by ETS1 in immortalized salivary gland epithelial cells of patients with salivary hypofunction and primary Sjögren's syndrome

Primary Sjögren’s syndrome (pSS) patients exhibit enhanced degradation of the salivary epithelium initially through MMP9 overexpression. We assessed the expression of MMP9 and an associated transcription factor, ETS1, in primary salivary gland epithelial cells (SGECs) and investigated potential regulatory mechanism(s) in immortalized SGECs. SGECs and iSGECs were derived from pSS and/or xerostomic “sicca” patients. siRNA knockdown of ETS1 in iSGECs was performed to determine MMP9 mRNA (qRT-PCR) and protein expression (ELISA). ETS1 binding to MMP9 promoter was assessed by luciferase activity and binding confirmed by mutagenesis and ChIP. Effects of ETS1 overexpression on progenitor and Epithelial-Mesenchymal transition (EMT) associated markers were determined by Western blot. Expression of ETS1 and its phosphorylated form in iSGECs was determined by immunofluorescence microscopy. ETS1 and MMP9 were overexpressed in SGECs of pSS and non-pSS sicca patients with salivary gland lymphocytic infiltration compared to non-pSS sicca patients without infiltration. ETS1 siRNA knockdown reduced both MMP9 mRNA and protein levels. ETS1 overexpression affected the expression of EMT and progenitor cell markers. Lastly, ETS1 bound the MMP9 promoter within the DNA region of −296 bp to −339 bp. ETS1 may impair salivary function through direct transcriptional control of the MMP9 promoter. ETS1 upregulation may also affect other factors involved in repair of the dysfunctional pSS salivary epithelium.

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.

Cephaeline is an inductor of histone H3 acetylation and inhibitor of mucoepidermoid carcinoma cancer stem cells

AIM

To evaluate the potential use of Cephaeline as a therapeutic strategy to manage mucoepidermoid carcinomas (MEC) of the salivary glands.

MATERIAL AND METHODS

UM-HMC-1, UM-HMC-2, and UM-HMC-3A MEC cell lines were used to establish the effects of Cephaeline over tumor viability determined by MTT assay. In vitro wound healing scratch assays were performed to address cellular migration while immunofluorescence staining for histone H3 lysine 9 (H3k9ac) was used to identify the acetylation status of tumor cells upon Cephaeline administration. The presence of cancer stem cells was evaluated by the identification of ALDH enzymatic activity by flow cytometry and through functional assays using in vitro tumorsphere formation.

RESULTS

A single administration of Cephaeline resulted in reduced viability of MEC cells along with the halt on tumor growth and cellular migration potential. Administration of Cephaeline resulted in chromatin histone acetylation as judged by the increased levels of H3K9ac and disruption of tumorspheres formation. Interestingly, ALDH levels were increased in UM-HMC-1 and UM-HMC-3A cell lines, while UM-HMC-2 showed a reduced enzymatic activity.

CONCLUSION

Cephaeline has shown anti-cancer properties in all MEC cell lines tested by regulating tumor cells' viability, migration, proliferation, and disrupting the ability of cancer cells to generate tumorspheres.

Altered presence of extra cellular matrix components in murine skin cancer: Modulation by Azadirachta indica leaf extract

BACKGROUND AND AIM

Although, the anticancer potential of Aqueous Azadirachta indica leaf extract (AAILE) has been robustly established against cutaneous squamous cell carcinoma (SCC) in mice, however, its ability in modulating tumor associated extra cellular matrix (ECM) is largely unknown. Therefore, the present study was conceived to explore changes in ECM during murine skin cancer and its chemoprevention by AAILE.

EXPERIMENTAL PROCEDURE

Skin tumors were induced using a two-stage model of carcinogenesis employing topical application of 7,12-Dimethylbenz(a)anthracene (DMBA) and 12-O-tetradecanoyl phorbol-13-acetate (TPA) as carcinogen and promoter respectively. AAILE was administered orally to the animals. Male Laca mice were divided into four groups: control, AAILE, DMBA/TPA and AAILE + DMBA/TPA.

RESULTS

The tumors obtained in DMBA/TPA and AAILE + DMBA/TPA groups were histologically identified as SCC. Tumor induction in these groups was accompanied by raised serum carcinoembryonic antigen (CEA) levels when compared to control counterparts. Assessment of hydroxyproline levels and histochemical staining with sirius red and trichrome stain revealed an increase in collagen in tumors of DMBA/TPA group. An increase in glycosaminoglycans (GAGs) levels was also observed in DMBA/TPA group as made evident by biochemical studies and histochemical staining using mucicarmine and alcian blue-periodic acid schiff's stain. Administration of AAILE to DMBA/TPA treated animals caused a decrease in collagen and GAG levels along with a decrease in serum CEA levels.

CONCLUSION

Skin tumors exhibited altered presence of ECM components which is indicative of a modified ECM. AAILE administration antagonised tumor associated ECM alterations which may be contributing to its chemopreventive activity as reported previously.

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.

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.

Survival of salivary gland cancer stem cells requires mTOR signaling

Advanced salivary gland mucoepidermoid carcinoma (MEC) is a relentless cancer that exhibits resistance to conventional chemotherapy. As such, treatment for patients with advanced MEC is tipically radical surgery and radiotherapy. Facial disfigurement and poor quality of life are frequent treatment challenges, and many patients succumb to loco-regional recurrence and/or metastasis. We know that cancer stem-like cells (CSC) drive MEC tumorigenesis. The current study tests the hypothesis that MEC CSC are sensitive to therapeutic inhibition of mTOR. Here, we report a correlation between the long-term clinical outcomes of 17 MEC patients and the intratumoral expression of p-mTOR (p = 0.00294) and p-S6K1 (p = 0.00357). In vitro, we observed that MEC CSC exhibit constitutive activation of the mTOR signaling pathway (i.e., mTOR, AKT, and S6K1), unveiling a potential strategy for targeted ablation of these cells. Using a panel of inhibitors of the mTOR pathway, i.e., rapamycin and temsirolimus (mTOR inhibitors), buparlisib and LY294002 (AKT inhibitors), and PF4708671 (S6K1 inhibitor), we observed consistently dose-dependent decrease in the fraction of CSC, as well as inhibition of secondary sphere formation and self-renewal in three human MEC cell lines (UM-HMC-1,-3A,-3B). Notably, therapeutic inhibition of mTOR with rapamycin or temsirolimus induced preferential apoptosis of CSC, when compared to bulk tumor cells. In contrast, conventional chemotherapeutic drugs (cisplatin, paclitaxel) induced preferential apoptosis of bulk tumor cells and accumulation of CSC. In vivo, therapeutic inhibition of mTOR with temsirolimus caused ablation of CSC and downregulation of Bmi-1 expression (major inducer of stem cell self-renewal) in MEC xenografts. Transplantation of MEC cells genetically silenced for mTOR into immunodeficient mice corroborated the results obtained with temsirolimus. Collectively, these data demonstrated that mTOR signaling is required for CSC survival, and unveiled the therapeutic potential of targeting the mTOR pathway for elimination of highly tumorigenic cancer stem-like cells in salivary gland mucoepidermoid carcinoma.

Immortalization of Salivary Gland Epithelial Cells of Xerostomic Patients: Establishment and Characterization of Novel Cell Lines

Primary Sjögren’s Syndrome (pSS) is an autoimmune disease mainly affecting salivary and lacrimal glands. Previous pSS studies have relied on primary cell culture models or cancer cell lines with limited relevance to the disease. Our objective was to generate and characterize immortalized salivary gland epithelial cells (iSGECs) derived from labial salivary gland (LSG) biopsies of pSS patients (focus score > 1) and non-Sjögren’s Syndrome (nSS) xerostomic (i.e., sicca) female patients. To characterize iSGECs (n = 3), mRNA expression of specific epithelial and acinar cell markers was quantified by qRT-PCR. Protein expression of characterization markers was determined by immunocytochemistry and Western blot. Secretion of α-amylase by iSGECs was confirmed through colorimetric activity assay. Spheroid formation and associated alterations in expression markers were determined using matrigel-coated cell culture plates. Consistent mRNA and protein expressions of both epithelial and pro-acinar cell markers were observed in all three iSGEC lines. When cultured on matrigel medium, iSGECs formed spheroids, secreted α-amylase after β-adrenergic stimulation, and expressed multiple acinar cell markers at late passages. One iSGEC line retained adequate cell morphology without a loss of SV40Lt expression and proliferation potential after over 100 passages. In conclusion, our established iSGEC lines represent a viable model for salivary research due to their passaging capacity and maintenance of pro-acinar cell characteristics.

TrkB-Targeted Therapy for Mucoepidermoid Carcinoma

The brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (TrkB) pathway was previously associated with key oncogenic outcomes in a number of adenocarcinomas. The aim of our study was to determine the role of this pathway in mucoepidermoid carcinoma (MEC). Three MEC cell lines (UM-HMC-2, H253 and H292) were exposed to Cisplatin, the TrkB inhibitor, ANA-12 and a combination of these drugs. Ultrastructural changes were assessed through transmission electron microscopy; scratch and Transwell assays were used to assess migration and invasion; and a clonogenic assay and spheroid-forming assay allowed assessment of survival and percentage of cancer stem cells (CSC). Changes in cell ultrastructure demonstrated Cisplatin cytotoxicity, while the effects of ANA-12 were less pronounced. Both drugs, used individually and in combination, delayed MEC cell migration, invasion and survival. ANA-12 significantly reduced the number of CSC, but the Cisplatin effect was greater, almost eliminating this cell population in all MEC cell lines. Interestingly, the spheroid forming capacity recovered, following the combination therapy, as compared to Cisplatin alone. Our studies allowed us to conclude that the TrkB inhibition, efficiently impaired MEC cell migration, invasion and survival in vitro, however, the decrease in CSC number, following the combined treatment of ANA-12 and Cisplatin, was less than that seen with Cisplatin alone; this represents a limiting factor.

Lycopene enriched tomato extract suppresses chemically induced skin tumorigenesis in mice

Abstract. The present study revealed the effects of Lycopene enriched tomato extract (LycT) on chemically induced skin cancer in mice. Skin tumors were induced by topical application of 7,12-Dimethylbenz(a)anthracene (DMBA) [500 nmol/100 ul of acetone, twice a week for two weeks] and 12-O-tetradecanoyl phorbol-13-acetate (TPA) [1.7 nmol/100 ul of acetone, twice a week for eighteen weeks] and LycT (5 mg/kg b.w.) was administered orally. Male Balb/c mice were divided into four groups (n = 15 per group): control, DMBA/TPA, LycT and LycT + DMBA/TPA. The chemopreventive response of LycT to skin tumorigenesis was evident by inhibition in tumor incidence, number, size, burden and volume in LycT + DMBA/TPA group when compared to DMBA/TPA group. This was associated with inhibition of cell proliferation in LycT + DMBA/TPA group as observed by the decrease in epidermal morphometric parameters and mRNA and protein expression of proliferating cell nuclear antigen when compared to DMBA/TPA group (p ≤ 0.05). LycT decreased (p ≤ 0.05) the mRNA and protein expression of angiogenic genes (vascular endothelial growth factor, angiopoietin-2, basic fibroblast growth factor) in LycT + DMBA/TPA group, suggesting its anti-angiogenic effects. The increase (p ≤ 0.05) in protein expression of connexin-32 and 43 in LycT + DMBA/TPA group suggests improved inter cellular communication when compared to DMBA/TPA group. Histochemical studies demonstrated that the components of extracellular matrix (fibrous proteins and mucopolysaccharides) were also modulated during skin carcinogenesis and its chemoprevention by LycT. The decrease in cell proliferation parameters and expression of angiogenesis associated genes, modulation of ECM components and increase in expression of connexins suggest that LycT improved multiple dysregulated processes during chemoprevention of skin cancer.

Claudin expression is maintained in mucoepidermoid carcinoma of the salivary gland

OBJECTIVE

The aim of the present study was to investigate the expression of claudin-1, -3, -4, -5 and -7 proteins in mucoepidermoid carcinoma of oral cavity and analyze whether EGF may interfere in the expression of the genes that encode claudins using in vitro models.

MATERIAL AND METHODS

Using immunohistochemistry, the expression of claudins was searched in 36 histologically graded cases of mucoepidermoid carcinoma. The association of expression of claudins with clinical-pathological parameters was evaluated. An in vitro step investigated the influence of EGF on gene expression of claudins by real time RT-PCR technique.

RESULTS

Claudin-1, -3, -4, -5, and -7 were highly expressed in most mucoepidermoid carcinomas. These expressions were compared with clinicopathological parameters. High expression of claudin-1 was associated with patients over 40 years-old (p = 0.05) and Caucasians (p = 0.024). In vitro experiments demonstrated a tendency for Claudin gene expression increase after EGF stimulus.

CONCLUSIONS

The expression of claudins is maintained in mucoepidermoid carcinoma cells and EGF could be related with this expression. Our results point out to a fundamental biological importance to CLDNs in normal and neoplastic tissue. The expression patterns of CLDNs does not yet allow a clinical application, but the biological knowledge will ground evidence to new studies towards possible target-therapies.

Clinical Outcome of Minor Salivary Gland Cancers in the Oral Cavity: A Comparative Analysis With Squamous Cell Carcinomas of the Oral Cavity

Purpose: Salivary gland cancer (SGC) in the oral cavity is not common and has been less studied in comparison with oral squamous cell carcinoma (SCC). This study aimed to identify the clinical characteristics and outcomes of SGC in the oral cavity compared with oral SCC.

Methods: The medical charts of the patients with SGC (N = 68) arising from minor salivary glands and SCC (N = 750) in the oral cavity between 1995 and 2017 were reviewed retrospectively. The clinical and pathological factors and treatment outcomes were compared to identify clinical differences between oral SGC and SCC in total cases and in tumor size and subsite (propensity score)-matched pairs (N = 68 in each group). In addition, pattern of local invasion was pathologically assessed in a subset of SGC and SCC tumors.

Results: Patients with SGC in the oral cavity showed >90% survival at 5 years. Most common pathologies of SGC were mucoepidermoid carcinoma (39.7%) and adenoid cystic carcinoma (35.3%), where high-grade tumors (including adenoid cystic carcinomas having solid components, grade 2 or 3) represented only 36.8%. Compared with oral SCC, surgery for SGC had narrow surgical safety margin. However, local control was very successful in SGC even with <5 mm or positive resection margin through surgery plus adjuvant radiation treatments or surgery alone for small low-grade tumors. Pathologic analysis revealed that the frequency of oral SGC with infiltrative tumor border was significantly lower than that of oral SCC (46.4 vs. 87.2%, P < 0.001).

Conclusions: SGC in the oral cavity represents relatively good prognosis and has a locally less aggressive pathology compared with oral SCC. Adjuvant radiation can be very effective to control minimal residual disease in oral SGC. Our study proposed that a different treatment strategy for oral SGC would be reasonable in comparison with oral SCC.

Aquaporin 1, 3, and 5 Patterns in Salivary Gland Mucoepidermoid Carcinoma: Expression in Surgical Specimens and an In Vitro Pilot Study

Salivary gland aquaporins (AQPs) are essential for the control of saliva production and maintenance of glandular structure. However, little is known of their role in salivary gland neoplasia. Salivary gland tumors comprise a heterogeneous group of lesions, featuring variable histological characteristics and diverse clinical behaviors. Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. The aim of this study was to evaluate the expression of AQP1, AQP3, and AQP5 in 24 MEC samples by immunohistochemistry. AQP1 expression was observed in vascular endothelium throughout the tumor stroma. AQP3 was expressed in epidermoid and mucosal cells and AQP5 was expressed in mucosal cells of MEC. These proteins were expressed in the human MEC cell line UH-HMC-3A. Cellular ultrastructural aspects were analyzed by electron microscopy to certificate the tumor cell phenotype. In summary, our results show that, despite the fact that these molecules are important for salivary gland physiology, they may not play a distinct role in tumorigenesis in MEC. Additionally, the in vitro model may offer new possibilities to further investigate mechanisms of these molecules in tumor biology and their real significance in prognosis and possible target therapies.

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 (ALDH^highCD44^high) 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 ALDH^highCD44^high (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.

UM-HACC-2A: MYB-NFIB fusion-positive human adenoid cystic carcinoma cell line

OBJECTIVES

Limited availability of validated human adenoid cystic carcinoma (ACC) cell lines has hindered the mechanistic understanding of the pathobiology of this malignancy and the development of effective therapies. The purpose of this work was to generate and characterize a human ACC cell line.

MATERIAL AND METHODS

Immediately after surgery, a tumor fragment from a minor salivary gland from the tongue of a female Caucasian was minced, dissociated, and a single cell suspension was plated in fibronectin-coated flasks. A culture medium containing bovine brain extract and rhEGF was optimized for these cells. Whole exome sequencing was used to evaluate the presence of MYB-NFIB translocation.

RESULTS

The University of Michigan-Human Adenoid Cystic Carcinoma (UM-HACC)-2A cells showed continuous growth in monolayers for at least 180 in vitro passages while maintaining epithelial morphology. Short-tandem repeat (STR) profiling confirmed a 100% match to patient DNA. Whole exome sequencing revealed the presence of the MYB-NFIB fusion in UM-HACC-2A cells, which was confirmed by PCR analysis. Western blots revealed high expression of epithelial markers (e.g. E-cadherin, EGFR, pan-cytokeratin) and proteins associated with ACC (e.g. c-Myb, p63). Developmental therapeutic studies showed that UM-HACC-2A cells were resistant to cisplatin (IC₅₀ = 44.7 µM) while more responsive to paclitaxel (IC₅₀ = 0.0006 µM). In a pilot study, we observed that UM-HACC-2A cells survived orthotopic transplantation into the submandibular gland. Notably, one of the mice injected with UM-HACC-2A cells exhibited lung metastasis after 6 months.

CONCLUSION

UM-HACC-2A is a MYB-NFIB fusion-positive ACC cell line that is suitable for mechanistic and developmental therapeutics studies.

Inhibition of Protein Phosphatase 2A Sensitizes Mucoepidermoid Carcinoma to Chemotherapy via the PI3K-AKT Pathway in Response to Insulin Stimulus

BACKGROUND/AIMS

Protein phosphatase 2A (PP2A) is a ubiquitous serine/threonine phosphatase that mediates cell cycle regulation and metabolism. Mounting evidence has indicated that PP2A inhibition exhibits considerable anticancer potency in multiple types of human cancers. However, the efficacy of PP2A inhibition remains unexplored in mucoepidermoid carcinoma (MEC), especially in locally advanced and metastatic cases with limited systemic treatment. In this study, we demonstrated the therapeutic potency of LB100 in mucoepidermoid carcinoma.

METHODS

In this study, the expression of PP2A was evaluated using immunohistochemical (IHC) staining. The effects associated with LB100 alone and in combination with cisplatin for the treatment of mucoepidermoid carcinoma were investigated both in vitro, regarding metabolism, proliferation, and migration, and in vivo in a mucoepidermoid carcinoma xenograft model. In addition, with LB100 treatment and in response to an insulin stimulus, the expression levels and phosphorylation levels of targets in the PI3K-AKT pathway were determined using western blot analysis and immunoblotting.

RESULTS

The expression of protein phosphatase 2A was significantly upregulated in the clinical specimens of high-grade MECs compared with those of low-/medium-grade MECs and normal controls. In this article, we report that a small molecule PP2A inhibitor, LB100, decreased cellular viability and glycolytic activity and induced G2/M cell cycle arrest. Importantly, LB100 enhanced the efficacy of cisplatin in mucoepidermoid carcinoma cells both in vitro and in vivo. PP2A inhibition by LB100 increased the phosphorylation of insulin receptor substrate 1(IRS-1) on serine residues, downregulated the expression of phosphatidylinositol 3-kinase (PI3K) p110 alpha subunit and dephosphorylated AKT at Ser473 and Thr308 in mucoepidermoid carcinoma cells in response to insulin stimulus.

CONCLUSION

These results highlight the translational potential of PP2A inhibition to synergize with cisplatin in mucoepidermoid carcinoma treatment.

Autophagic reliance promotes metabolic reprogramming in oncogenic KRAS-driven tumorigenesis

Defects in basal autophagy limit the nutrient supply from recycling of intracellular constituents. Despite our understanding of the prosurvival role of macroautophagy/autophagy, how nutrient deprivation, caused by compromised autophagy, affects oncogenic KRAS-driven tumor progression is poorly understood. Here, we demonstrate that conditional impairment of the autophagy gene Atg5 (atg5-KO) extends the survival of KRASG12V-driven tumor-bearing mice by 38%. atg5-KO tumors spread more slowly during late tumorigenesis, despite a faster onset. atg5-KO tumor cells displayed reduced mitochondrial function and increased mitochondrial fragmentation. Metabolite profiles indicated a deficiency in the nonessential amino acid asparagine despite a compensatory overexpression of ASNS (asparagine synthetase), key enzyme for de novo asparagine synthesis. Inhibition of either autophagy or ASNS reduced KRASG12V-driven tumor cell proliferation, migration, and invasion, which was rescued by asparagine supplementation or knockdown of MFF (mitochondrial fission factor). Finally, these observations were reflected in human cancer-derived data, linking ASNS overexpression with poor clinical outcome in multiple cancers. Together, our data document a widespread yet specific asparagine homeostasis control by autophagy and ASNS, highlighting the previously unrecognized role of autophagy in suppressing the metabolic barriers of low asparagine and excessive mitochondrial fragmentation to permit malignant KRAS-driven tumor progression.

Salivary Gland Cancer Patient-Derived Xenografts Enable Characterization of Cancer Stem Cells and New Gene Events Associated with Tumor Progression

Purpose: Salivary gland cancers (SGC) frequently present with distant metastases many years after diagnosis, suggesting a cancer stem cell (CSC) subpopulation that initiates late recurrences; however, current models are limited both in their availability and suitability to characterize these rare cells.Experimental Design: Patient-derived xenografts (PDX) were generated by engrafting patient tissue onto nude mice from one acinic cell carcinoma (AciCC), four adenoid cystic carcinoma (ACC), and three mucoepidermoid carcinoma (MEC) cases, which were derived from successive relapses from the same MEC patient. Patient and PDX samples were analyzed by RNA-seq and Exome-seq. Sphere formation potential and in vivo tumorigenicity was assessed by sorting for Aldefluor (ALDH) activity and CD44-expressing subpopulations.Results: For successive MEC relapses we found a time-dependent increase in CSCs (ALDH⁺CD44^high), increasing from 0.2% to 4.5% (P=0.033), but more importantly we observed an increase in individual CSC sphere formation and tumorigenic potential. A 50% increase in mutational burden was documented in subsequent MEC tumors, and this was associated with increased expression of tumor-promoting genes (MT1E, LGR5, and LEF1), decreased expression of tumor-suppressor genes (CDKN2B, SIK1, and TP53), and higher expression of CSC-related proteins such as SOX2, MYC, and ALDH1A1. Finally, genomic analyses identified a novel NFIB-MTFR2 fusion in an ACC tumor and confirmed previously reported fusions (NTRK3-ETV6 and MYB-NFIB)Conclusions: Sequential MEC PDX models preserved key patient features and enabled the identification of genetic events putatively contributing to increases in both CSC proportion and intrinsic tumorigenicity, which mirrored the patient's clinical course. Clin Cancer Res; 24(12); 2935-43. ©2018 AACR.

Overcoming adaptive resistance in mucoepidermoid carcinoma through inhibition of the IKK-β/IκBα/NFκB axis

Patients with mucoepidermoid carcinoma (MEC) experience low survival rates and high morbidity following treatment, yet the intrinsic resistance of MEC cells to ionizing radiation (IR) and the mechanisms underlying acquired resistance remain unexplored. Herein, we demonstrated that low doses of IR intrinsically activated NFκB in resistant MEC cell lines. Moreover, resistance was significantly enhanced in IR-sensitive cell lines when NFκB pathway was stimulated. Pharmacological inhibition of the IKK-β/IκBα/NFκB axis, using a single dose of FDA-approved Emetine, led to a striking sensitization of MEC cells to IR and a reduction in cancer stem cells. We achieved a major step towards better understanding the basic mechanisms involved in IR-adaptive resistance in MEC cell lines and how to efficiently overcome this critical problem.

Targeting histone deacetylase and NFκB signaling as a novel therapy for Mucoepidermoid Carcinomas

Malignancies from the salivary glands are rare and represent 11% of all cancers from the oropharyngeal anatomical area. Mucoepidermoid Carcinomas (MEC) is the most common malignancy from the salivary glands. Low survival rates of high-grade Mucoepidermoid Carcinomas (MEC) are particularly associated with the presence of positive lymph nodes, extracapsular lymph node spread, and perineural invasion. Most recently, the presence of cancer stem cells (CSC), and the activation of the NFκB signaling pathway have been suggested as cues for an acquired resistance phenotype. We have previously shown that NFκB signaling is very active in MEC tumors. Herein, we explore the efficacy of NFκB inhibition in combination with class I and II HDAC inhibitor to deplete the population of CSC and to destroy MEC tumor cells. Our finding suggests that disruption of NFκB signaling along with the administration of HDAC inhibitors constitute an effective strategy to manage MEC tumors.

Expanding primary cells from mucoepidermoid and other salivary gland neoplasms for genetic and chemosensitivity testing

Restricted availability of cell and animal models is a rate-limiting step for investigation of salivary gland neoplasm pathophysiology and therapeutic response. Conditionally reprogrammed cell (CRC) technology enables establishment of primary epithelial cell cultures from patient material. This study tested a translational workflow for acquisition, expansion and testing of CRC-derived primary cultures of salivary gland neoplasms from patients presenting to an academic surgical practice. Results showed that cultured cells were sufficient for epithelial cell-specific transcriptome characterization to detect candidate therapeutic pathways and fusion genes, and for screening for cancer risk-associated single nucleotide polymorphisms (SNPs) and driver gene mutations through exome sequencing. Focused study of primary cultures of a low-grade mucoepidermoid carcinoma demonstrated amphiregulin-mechanistic target of rapamycin-protein kinase B (AKT; AKT1) pathway activation, identified through bioinformatics and subsequently confirmed as present in primary tissue and preserved through different secondary 2D and 3D culture media and xenografts. Candidate therapeutic testing showed that the allosteric AKT inhibitor MK2206 reproducibly inhibited cell survival across different culture formats. By contrast, the cells appeared resistant to the adenosine triphosphate competitive AKT inhibitor GSK690693. Procedures employed here illustrate an approach for reproducibly obtaining material for pathophysiological studies of salivary gland neoplasms, and other less common epithelial cancer types, that can be executed without compromising pathological examination of patient specimens. The approach permits combined genetic and cell-based physiological and therapeutic investigations in addition to more traditional pathologic studies, and can be used to build sustainable bio-banks for future inquiries.This article has an associated First Person interview with the first author of the paper.

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.

Sensitizing mucoepidermoid carcinomas to chemotherapy by targeted disruption of cancer stem cells

Mucoepidermoid carcinoma (MEC) is the most common malignancy of salivary glands. The response of MEC to chemotherapy is unpredictable, and recent advances in cancer biology suggest the involvement of cancer stem cells (CSCs) in tumor progression and chemoresistance and radioresistance phenotype. We found that histone acetyltransferase inhibitors (HDACi) were capable of disrupting CSCs in MEC. Furthermore, administration of HDACi prior to Cisplatin (two-hit approach) disrupts CSCs and sensitizes tumor cells to Cisplatin. Our findings corroborate to emerging evidence that CSCs play a key role in tumor resistance to chemotherapy, and highlights a pharmacological two-hit approach that disrupts tumor resistance to conventional therapy.

Histones Acetylation and Cancer Stem Cells (CSCs)

Chromatin decondensation is a key mechanism that guarantees gene transcription and repair of the genome, regulated mainly by the acetylation of histones. Emerging evidence has pointed out to histones as a new controlling mechanism of stem cell maintenance and fate. In this chapter, we will focus on the methods used to enrich tumor cell lines for cancer stem cells, and in the methods to identify the status of the histone acetylation in cancer cells and stem cells using immunofluorescence, invasion, and adhesion assays and identification of nuclear size.

Microencapsulation of low-passage poorly-differentiated human mucoepidermoid carcinoma cells by alginate microcapsules: in vitro profiling of angiogenesis-related molecules

Background

Human mucoepidermoid carcinoma (MEC) is regarded as the most common primary salivary malignancy. High-grade MEC has a high risk of recurrence and poor prognosis. Tumor angiogenesis, induced by poorly differentiated cancer cells of high-grade MEC, contributes to tumor growth and metastasis. Therefore, elucidating molecular mechanisms underlying the pro-angiogenic ability of poorly differentiated MEC cells is critical for the understanding of high-grade MEC progression. It is well known that three-dimensional (3D) cell culture, in contrast with conventional two-dimensional (2D) culture, provides a better approach to in vitro recapitulation of in vivo characteristics of cancer cells and their surrounding microenvironment. The purpose of this study was to model a 3D environment for in vitro gene expression profiling of key molecules in poorly differentiated MEC cells for cancer neovascularization and compared them with traditional 2D cell culture.

Methods

Low-passage poorly differentiated MEC cells, derived from human patient samples of high-grade MEC, were microencapsulated in sodium alginate gel microcapsules (3D culture) and compared with cells grown in 2D culture. Cancer cell proliferation was determined by MTT assays for 1 week, and gene expression of VEGF-A, bFGF and TSP-1 was analyzed by western blotting or ELISA. The hypoxic environment in 3D versus 2D culture were assessed by western blotting or immunofluorescence for HIF1α, and the effect of hypoxia on VEGF-A gene expression in 3D cultured cancer cells was assessed by western blotting with the use of the HIF1α inhibitor, 2-methoxyestradiol (2-MeOE2).

Results

When encapsulated in alginate gel microcapsules, low-passage poorly differentiated human MEC cells grew in blocks and demonstrated stronger and relatively unlimited proliferation activities. Moreover, significant differences were found in gene expression, with 3D-grown cancer cells a significant increment of VEGF-A and bFGF and a drastic reduction of TSP-1. Consistently, 3D-grown cancer cells secreted significantly more VEGF-A than 2D culture cancer cells. Furthermore, 3D-grown cancer cells showed significantly higher expression of HIF1α, a molecular indicator of hypoxia; the increased expression of VEGF-A in 3D cultured cancer cells was shown to be dependent on the HIF1α activities.

Conclusions

The present work shows the effects of 3D culture model by alginate microencapsulation on the proangiogenic potentials of low-passage poorly differentiated human MEC cells. Cancer cells in this 3D system demonstrate significant intensification of key molecular processes for tumor angiogenesis. This is due to a better modeling of the hypoxic tumor microenvironment during 3D culture.

Unlocking the chromatin of adenoid cystic carcinomas using HDAC inhibitors sensitize cancer stem cells to cisplatin and induces tumor senescence

Adenoid cystic carcinoma (ACC) is an uncommon malignancy of the salivary glands that is characterized by local recurrence and distant metastasis due to its resistance to conventional therapy. Platinum-based therapies have been extensively explored as a treatment for ACC, but they show little effectiveness. Studies have shown that a specific group of tumor cells, harboring characteristics of cancer stem cells (CSCs), are involved in chemoresistance of myeloid leukemias, breast, colorectal and pancreatic carcinomas. Therapeutic strategies that target CSCs improve the survival of patients by decreasing the rates of tumor relapse, and epigenetic drugs, such as histone deacetylase inhibitors (HDACi), have shown promising results in targeting CSCs. In this study, we investigated the effect of the HDACi Suberoylanilide hydroxamic acid (Vorinostat), and cisplatin, alone or in combination, on CSCs and non-CSCs from ACC. We used CSCs as a biological marker for tumor resistance to therapy in patient-derived xenograft (PDX) samples and ACC primary cells. We found that cisplatin reduced tumor viability, but enriched the population of CSCs. Systemic administration of Vorinostat reduced the number of detectable CSCs in vivo and in vitro, and a low dose of Vorinostat decreased tumor cell viability. However, the combination of Vorinostat and cisplatin was extremely effective in depleting CSCs and reducing tumor viability in all ACC primary cells by activating cellular senescence. These observations suggest that HDACi and intercalating agents act more efficiently in combination to destroy tumor cells and their stem cells.

Prognostic factors of palatal mucoepidermoid carcinoma: a retrospective analysis based on a double-center study

Mucoepidermoid carcinoma (MEC) of the palate is a common malignancy of minor salivary glands. This study was designed to identify the prognostic factors for MEC of the palate. The medical records of patients diagnosed with MEC of the palate who visited the Department of Oral and Maxillofacial Surgery at Nanjing Stomatological Hospital and the Department of Stomatology at Central Hospital of Xuzhou were retrospectively studied. The prognostic factors were determined using a Cox proportional hazards model. Furthermore, the expression of cancer stem cell (CSC) markers CD44, CD133, Nanog and Sox2 were detected in neoplastic samples of these patients by immunohistochemistry. As a result, both univariate analysis and multivariate analysis proved a high histological grade and an advanced tumor stage as negative prognostic factors for overall survival. By immunohistochemistry staining and survival analysis, a combination of CD44/CD133/SOX2 was found to have the strongest prognostic value for palatal MEC patients. In conclusion, the proposed nomogram which include histological grade and tumor stage along with cancer stem cell markers provides a more accurate long-term prediction for palatal MEC patients.

Patient-derived xenograft (PDX) tumors increase growth rate with time

Patient-derived xenograft (PDX) models are frequently used for translational cancer research, and are assumed to behave consistently as the tumor ages. However, growth rate constancy as a function of time is unclear. Notably, variable PDX growth rates over time might have implications for the interpretation of translational studies. We characterized four PDX models through several in vivo passages from primary human head and neck squamous cell carcinoma and salivary gland adenoid cystic carcinoma. We developed a mathematical approach to merge growth data from different passages into a single measure of relative tumor volume normalized to study initiation size. We analyzed log-relative tumor volume increase with linear mixed effect models. Two oral pathologists analyzed the PDX tissues to determine if histopathological feature changes occurred over in vivo passages. Tumor growth rate increased over time. This was determined by repeated measures linear regression statistical analysis in four different PDX models. A quadratic statistical model for the temporal effect predicted the log-relative tumor volume significantly better than a linear time effect model. We found a significant correlation between passage number and histopathological features of higher tumor grade. Our mathematical treatment of PDX data allows statistical analysis of tumor growth data over long periods of time, including over multiple passages. Non-linear tumor growth in our regression models revealed the exponential growth rate increased over time. The dynamic tumor growth rates correlated with quantifiable histopathological changes that related to passage number in multiple types of cancer.

ALDH/CD44 identifies uniquely tumorigenic cancer stem cells in salivary gland mucoepidermoid carcinomas

A small sub-population of cells characterized by increased tumorigenic potential, ability to self-renew and to differentiate into cells that make up the tumor bulk, has been characterized in some (but not all) tumor types. These unique cells, namedcancer stem cells, are considered drivers of tumor progression in these tumors. The purpose of this work is to understand if cancer stem cells play a functional role in the tumorigenesis of salivary gland mucoepidermoid carcinomas. Here, we investigated the expression of putative cancer stem cell markers (ALDH, CD10, CD24, CD44) in primary human mucoepidermoid carcinomas by immunofluorescence, in vitro salisphere assays, and in vivo tumorigenicity assays in immunodeficient mice. Human mucoepidermoid carcinoma cells (UM-HMC-1, UM-HMC-3A, UM-HMC-3B) sorted for high levels of ALDH activity and CD44 expression (ALDHhighCD44high) consistently formed primary and secondary salispheres in vitro, and showed enhanced tumorigenic potential in vivo (defined as time to tumor palpability, tumor growth after palpability), when compared to ALDHlowCD44low cells. Cells sorted for CD10/CD24, and CD10/CD44 showed varying trends of salisphere formation, but consistently low in vivo tumorigenic potential. And finally, cells sorted for CD44/CD24 showed inconsistent results in salisphere formation and tumorigenic potential assays when different cell lines were evaluated. Collectively, these data demonstrate that salivary gland mucoepidermoid carcinomas contain a small population of cancer stem cells with enhanced tumorigenic potential and that are characterized by high ALDH activity and CD44 expression. These results suggest that patients with mucoepidermoid carcinoma might benefit from therapies that ablate these highly tumorigenic cells.

IL-6 Inhibition With MEDI5117 Decreases The Fraction of Head and Neck Cancer Stem Cells and Prevents Tumor Recurrence

Head and neck squamous cell carcinomas (HNSCC) exhibit a small population of uniquely tumorigenic cancer stem cells (CSC) endowed with self-renewal and multipotency. We have recently shown that IL-6 enhances the survival and tumorigenic potential of head and neck cancer stem cells (i.e. ALDH(high)CD44(high) cells). Here, we characterized the effect of therapeutic inhibition of IL-6 with a novel humanized anti-IL-6 antibody (MEDI5117) using three low-passage patient-derived xenograft (PDX) models of HNSCC. We observed that single agent MEDI5117 inhibited the growth of PDX-SCC-M1 tumors (P < .05). This PDX model was generated from a previously untreated HNSCC. In contrast, MEDI5117 was not effective at reducing overall tumor volume for PDX models representing resistant disease (PDX-SCC-M0, PDX-SCC-M11). Low dose MEDI5117 (3 mg/kg) consistently decreased the fraction of cancer stem cells in PDX models of HNSCC when compared to IgG-treated controls, as follows: PDX-SCC-M0 (P < .001), PDX-SCC-M1 (P < .001), PDX-SCC-M11 (P = .04). Interestingly, high dose MEDI5117 (30 mg/kg) decreased the CSC fraction in the PDX-SCC-M11 model (P = .002), but not in PDX-SCC-M0 and PDX-SCC-M1. MEDI5117 mediated a dose-dependent decrease in the number of orospheres generated by ALDH(high)CD44(high) cells cultured in ultra-low attachment plates (P < .05), supporting an inhibitory effect on head and neck cancer stem cells. Notably, single agent MEDI5117 reduced the overall recurrence rate of PDX-SCC-M0, a PDX generated from the local recurrence of human HNSCC. Collectively, these data demonstrate that therapeutic inhibition of IL-6 with low-dose MEDI5117 decreases the fraction of cancer stem cells, and that adjuvant MEDI5117 inhibits recurrence in preclinical models of HNSCC.

Targeting MDM2 for Treatment of Adenoid Cystic Carcinoma

PURPOSE

There are no effective treatment options for patients with advanced adenoid cystic carcinoma (ACC). Here, we evaluated the effect of a new small molecule inhibitor of the MDM2-p53 interaction (MI-773) in preclinical models of ACC.

EXPERIMENTAL DESIGN

To evaluate the anti-tumor effect of MI-773, we administered it to mice harboring three different patient-derived xenograft (PDX) models of ACC expressing functional p53. The effect of MI-773 on MDM2, p53, phospho-p53, and p21 was examined by Western blots in 5 low passage primary human ACC cell lines and in MI-773-treated PDX tumors.

RESULTS

Single-agent MI-773 caused tumor regression in the 3 PDX models of ACC studied here. For example, we observed a tumor growth inhibition index of 127% in UM-PDX-HACC-5 tumors that was associated with an increase in the fraction of apoptotic cells (P = 0.015). The number of p53-positive cells was increased in MI-773-treated PDX tumors (P < 0.001), with a correspondent shift in p53 localization from the nucleus to the cytoplasm. Western blots demonstrated that MI-773 potently induced expression of p53 and its downstream targets p21, MDM2, and induced phosphorylation of p53 (serine 392) in low passage primary human ACC cells. Notably, MI-773 induced a dose-dependent increase in the fraction of apoptotic ACC cells and in the fraction of cells in the G1 phase of cell cycle (P < 0.05).

CONCLUSIONS

Collectively, these data demonstrate that therapeutic inhibition of the MDM2-p53 interaction with MI-773 activates downstream effectors of apoptosis and causes robust tumor regression in preclinical models of ACC. Clin Cancer Res; 22(14); 3550-9. ©2016 AACR.

Anti-tumor effect of inhibition of IL-6 signaling in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most frequent malignant salivary gland cancer. Response to chemoradiotherapy is modest, and therefore radical surgery remains the standard-of-care. Emerging evidence suggests that Interleukin (IL)-6 signaling correlates with the survival of cancer stem cells and resistance to therapy. Here, we investigated whether inhibition of IL-6 receptor (IL-6R) signaling with tocilizumab (humanized anti-human IL-6R antibody) sensitizes MEC to chemotherapy using human mucoepidermoid carcinoma cell lines (UM-HMC) and correspondent xenograft models. In vitro, we observed that tocilizumab inhibited STAT3 phosphorylation but had no measurable effect in MEC cell viability (UM-HMC-1,-3A,-3B). In contrast, the anti-tumor effect of single agent tocilizumab on MEC xenografts was comparable to paclitaxel or cisplatin. Combination of tocilizumab with cisplatin or paclitaxel enhanced the inhibitory effect of chemotherapy on xenograft growth (P < 0.05), time to failure (P < 0.01), decreased vascular endothelial growth factor (VEGF) expression and tumor microvessel density (P < 0.05) without added systemic toxicities. Notably, tocilizumab decreased the fraction of MEC cancer stem cells (ALDH(high)CD44(high)) in vitro, and prevented paclitaxel-induced increase in the fraction of cancer stem cells in vivo (P < 0.05). Collectively, these findings demonstrate that tocilizumab enhances the anti-tumor effect of conventional chemotherapy in preclinical models of mucoepidermoid carcinoma, and suggest that patients might benefit from combination therapy with an inhibitor of IL-6R signaling and chemotherapeutic agent such as paclitaxel.

Ductal activation of oncogenic KRAS alone induces sarcomatoid phenotype

Salivary duct carcinoma (SDC) is an uncommon, but aggressive malignant tumor with a high mortality rate. Herein, we reported the detection of somatic KRAS A146T and Q61H mutations in 2 out of 4 (50%) sarcomatoid SDC variants. Transgenic mice carrying the human oncogenic KRAS^G12V, which spatiotemporal activation by tamoxifen (TAM)-inducible Cre recombinase Ela-CreERT in the submandibular gland (SMG) ductal cells, was established and characterized. Visible carcinoma was detected as early as day-15 following oncogenic KRAS^G12V induction alone, and these tumors proliferate rapidly with a median survival of 28-days accompanied with histological reminiscences to human sarcomatoid SDC variants. Moreover, these tumors were resistant to cetuximab treatment despite augmented EGFR signaling, attesting its malignancy. Our findings suggest that LGL-KRas^G12V;Ela-CreERT transgenic mice could serve as a useful preclinical model for investigating underlying mechanisms and developing potential therapies.