Activation of the EGFR/ERK pathway in high-grade mucoepidermoid carcinomas of the salivary glands

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.

Immunological and biological dissection of normal and tumoral salivary glands

Salivary glands naturally play central roles in oral immunity. The salivary glands microenvironment inevitable may be exposed to exogenous factors consequently triggering the initiation and formation of various malignant and benign tumors. Mesenchymal stem cells are recruited into salivary gland microenvironment, interact with tumor cells, and induce inhibitory cytokines as well as cells with immunosuppressive phenotypes such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). The immune components and tumor immune responses in malignant and benign SGTs are still under investigation. Immune responses may directly play a limiting role in tumor growth and expansion, or may participate in formation of a rich milieu for tumor growth in cooperation with other cellular and regulatory molecules. Immune checkpoint molecules (e.g. PDLs, HLA-G and LAG3) are frequently expressed on tumor cells and/or tumor-infiltrating lymphocytes (TILs) in salivary gland microenvironment, and an increase in their expression is associated with T cell exhaustion, immune tolerance and tumor immune escape. Chemokines and chemokine receptors have influential roles on aggressive behaviors of SGTs, and thereby they could be candidate targets for cancer immunotherapy. To present a broad knowledge on salivary glands, this review first provides a brief description on immunological functions of normal salivary glands, and then describe the SGT's tumor microenvironment, by focusing on mesenchymal stem cells, immune cell subsets, immune checkpoint molecules, chemokines and chemokine receptors, and finally introduces immune checkpoint inhibitors as well as potential targets for cancer therapy.

Molecular Targets in Salivary Gland Cancers: A Comprehensive Genomic Analysis of 118 Mucoepidermoid Carcinoma Tumors

INTRODUCTION

Salivary gland carcinomas (SGC) are histologically diverse cancers and next-generation sequencing (NGS) to identify key molecular targets is an important aspect in the management of advanced cases.

METHODS

DNA was extracted from paraffin embedded tissues of advanced SGC and comprehensive genomic profiling (CGP) was carried out to evaluate for base substitutions, short insertions, deletions, copy number changes, gene fusions and rearrangements. Tumor mutation burden (TMB) was calculated on approximately 1.25 Mb. Some 324 genes in the FoundationOne CDX panel were analyzed.

RESULTS

Mucoepidermoid carcinoma (MECa) mutations were assessed. CDKN2A and CDKN2B GA were common in mucoepidermoid carcinoma (MECa) (52.5 and 30.5%). PIK3CA was also common in MECa (16.9%). ERBB2 amplification/short variants (amp/SV) were found in MECa (5.9/0%). HRAS GA was common in MECa (14.4%) as well. Other targets, including BAP1, PTEN, and KRAS, were noted but had a low incidence. In terms of immunotherapy (IO)-predictive markers, TMB > 10 was more common in MECa (16.9%). PDL1 high was also seen in MECa (4.20%).

CONCLUSION

SGC are rare tumors with no FDA-approved treatment options. This large dataset reveals many opportunities for IO and targeted therapy contributing to the continuously increased precision in the selection of treatment for these patients.

Overexpression of LAG3, TIM3, and A2aR in adenoid cystic carcinoma and mucoepidermoid carcinoma

OBJECTIVE

Adenoid cystic carcinoma (AdCC) and mucoepidermoid carcinoma (MEC) are the two most frequent malignancies of salivary glands. This study aims to explore the expression and migration of LAG3, TIM3, and A2aR in AdCC and MEC, and the potential relationship with oncogenic signaling molecules and immunosuppressive cytokines.

MATERIALS AND METHODS

Custom made human salivary gland tissue microarrays included 81 AdCCs, 52 MECs, 76 normal salivary glands (NSG), and 14 pleomorphic adenoma (PMA) samples. Immunohistochemical analysis of lymphocyte activation gene 3 (LAG3), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM3), adenosine 2a receptor (A2aR), oncogenic phosphorylated S6 kinase (p-S6) and ERK_1/2 (p-ERK_1/2 ), and TGF-β1 was performed with salivary gland tissue microarrays of human samples. The correlation of the immunostaining was analyzed based on a digital pathological system, and data were evaluated by hierarchical cluster. Further in vitro studies of knockdown immune checkpoints LAG3, TIM3, and A2aR were carried out by siRNA transfection.

RESULTS

The expression levels of LAG3, TIM3, and A2aR were remarkably increased in AdCC and MEC, compared with NSG and PMA samples, but were independent of pathology grade. They were closely correlated with TGF-β1, slightly related to p-ERK_1/2 and p-S6. After the knockdown of immune checkpoints LAG3, TIM3, and A2aR, the migration of SACC-LM cell line was significantly reduced.

CONCLUSIONS

These results suggested that LAG3, TIM3, and A2aR are overexpressed in AdCC and MEC, may promote migration of SACC-LM cell and correlated with TGF-β1 and oncogenic signaling pathways.

Mucoepidermoid Carcinoma of the Salivary Gland: Demographics and Comparative Analysis in U.S. Children and Adults with Future Perspective of Management

Background: Salivary gland neoplasms are uncommon in both pediatric and adult populations. Mucoepidermoid carcinoma (MEC) is one of the most common salivary gland tumors and usually presents with atypical clinical features. This study sought to evaluate the demographic and clinical factors affecting outcomes in adults and pediatric populations with MEC that could be used to risk stratification for treatment selection and clinical trial enrollment. Methods: Data on 4507 MEC patients were extracted from the Surveillance Epidemiology and End Result (SEER) database (2000−2018). Patients aged ≤ 18 years were classified into the pediatric population, and those older than 18 years were placed in the adult group. Kaplan−Meier survival curves were created to analyze survival probabilities for various independent factors. Results: The pediatric population comprised 3.7% of the entire cohort, with a predominance of females (51.5%), while the adult population constituted 96.3% of the cohort, with a predominance of female patients (52.2%). Caucasians were the predominant race overall (75.3%), while more African Americans were seen in the pediatric group. In tumor size of <2 cm overall, poorly differentiated tumors with higher metastasis rates were observed more in adults (11.3% and 9.3%) than in the pediatric population (3.0% and 4.8%, p < 0.05). Surgical resection was the most common treatment option (53.9%), making up 63.6% of the pediatric and 53.5% of the adult groups. A combination of surgical resection and radiation was used in 29.8% of the entire cohort while a combination of surgical resection, radiation, and chemotherapy made up only 3.2%. The pediatric group had a lower overall mortality rate (5.5%) than the adult group (28.6%). Females had a higher 5-year survival rate in comparison to males (86.5%, and 73.7%, respectively). Surgical resection led to a more prolonged overall survival and 5-year cancer-specific survival (98.4% (C.I, 93.7−99.6) in the pediatric group and 88.8% (C.I, 87.5−90.0) in the adult group), respectively. Metastasis to the lung, bone, brain, and/or liver was found to have significantly lower survival rates. Multivariate analysis demonstrated that adults (hazard ratio [HR] = 7.4), Asian or Pacific Islander (HR = 0.5), male (HR = 0.8), poorly differentiated histology (HR = 3.8), undifferentiated histology (HR = 4.5), regional spread (HR = 2.1), and distant spread (HR = 3.2) were associated with increased mortality (p < 0.05). Conclusions: Mucoepidermoid carcinoma of the salivary glands primarily affects Whites and is more aggressive in adults than in the pediatric population. Even with surgical resection, the overall survival is poor in the adult population as compared to its pediatric counterparts. Advanced age, larger tumor size, male sex, and lymph node invasion are associated with increased mortality.

Distinct histone H3 modification profiles correlate with aggressive characteristics of salivary gland neoplasms

Post-translational modification of histones is the crucial event that affect many tumor-specific traits. A diverse type of histone modifications had been reported in different cancers with prognostic implications. This study aimed to examine the degree of histone H3 modifications in salivary gland neoplasms and their associations with tumor pathologic characteristics and proliferative activity. The expression of H3K9Ac, H3K18Ac, H3K9Me3 and Ki-67 in 70 specimens of salivary gland neoplasms, consisting of 30 mucoepidermoid carcinoma (MEC), 20 adenoid cystic carcinoma (ACC) and 20 pleomorphic adenoma (PA), were investigated immunohistochemically. The immunohistochemical scoring of 3 histone modification types and Ki-67 labeling index were determined. Overall, MEC demonstrated elevated H3K9Ac level compared with benign PA. Increased H3K9Me3 in MEC was positively correlated with small nest invasion at tumor front, advanced pathologic grade, and elevated proliferative index. In addition, the significant upregulation of all 3 types of histone H3 modification was noted in solid subtype of ACC and associated with increased cell proliferation. This study indicates that salivary gland neoplasms differentially acquire distinct patterns of histone H3 modification, which impact prognostically relevant cancer phenotypes. The hyperacetylation and methylation of histone H3 could be underpinning the prognostically worsen solid type of ACC, and the trimethylation of H3K9 may be involved in aggressive characteristics of MEC.

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Molecular and Cellular Modelling of Salivary Gland Tumors Open New Landscapes in Diagnosis and Treatment

Salivary gland tumors are neoplasms affecting the major and minor salivary glands of the oral cavity. Their complex pathological appearance and overlapping morphological features between subtypes, pose major challenges in the identification, classification, and staging of the tumor. Recently developed techniques of three-dimensional culture and organotypic modelling provide useful platforms for the clinical and biological characterization of these malignancies. Additionally, new advances in genetic and molecular screenings allow precise diagnosis and monitoring of tumor progression. Finally, novel therapeutic tools with increased efficiency and accuracy are emerging. In this review, we summarize the most common salivary gland neoplasms and provide an overview of the state-of-the-art tools to model, diagnose, and treat salivary gland tumors.

Salivary Gland Carcinoma: Novel Targets to Overcome Treatment Resistance in Advanced Disease

Salivary gland carcinomas (SGCs) account for <5% of head and neck malignant neoplasms, further subcategorized in over 20 histological subtypes. For the most part, treatment for advanced disease is guided by morphology. SGCs in general respond poorly to a wide array of standard chemotherapy, with short durability, and significant toxicity. More recently, next-generation sequencing provided significant input on the molecular characterization of each SGC subtype, not only improving diagnostic differentiation between morphologically similar tumor types but also identifying novel driver pathways that determine tumor biology and may be amenable to targeted therapy. Among the most common histological subtype is adenoid cystic carcinoma, which often harbors a chromosome translocation resulting in an MYB-NFIB oncogene, with various degrees of Myb surface expression. In a smaller subset, NOTCH1 mutations occur, conferring a more aggressive pattern and potential sensitivity to Notch inhibitors. Salivary duct carcinomas may overexpress Her-2 and androgen receptors, with promising clinical outcomes after exposure to targeted therapies approved for other indications. Secretory carcinoma, previously known as mammary analog secretory carcinoma, is distinguished by an ETV6-NTRK3 fusion that can both help differentiate it from its morphologically similar acinar cell carcinoma and make it susceptible to Trk inhibitors. In the present article, we discuss the molecular abnormalities, their impact on tumor biology, and therapeutic opportunities for the most common SGC subtypes and review published and ongoing clinical trials and future perspectives for this rare disease.

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.

Carcinomas of the lacrimal drainage system

Malignant tumors of epithelial origin are the most frequent neoplasms of the lacrimal drainage system (LDS). A total of 539 cases are reported in the literature from 1960 to 2019. LDS carcinoma is a disease of the middle-aged and elderly population, with a median age at diagnosis of 57 years. Overall, there is a slight male predominance. Reported risk factors are chronic inflammation, LDS papilloma, and infection with oncogenic viruses. Symptoms of an LDS carcinoma resemble those of benign, inflammatory diseases, with epiphora from obstruction of the LDS as the most frequently encountered symptom. The median time from symptoms to diagnosis is 12 months and even longer for patients reporting epiphora as the only initial symptom. This diagnostic delay leads to a substantial fraction of patients with locally advanced tumors and lymph node spread at the time of diagnosis. Surgery with adjuvant radiotherapy is the treatment of choice for most patients; however, the extension and aggressiveness of the disease and the patient's general health and preferences determine the definite treatment. Five-year overall survival is reported to range from 61 to 87.6%. A large tumor size and positive lymph node status correlate with a decreased overall and disease-free survival.

Assessing the prognostic significance of MUC4β in mucoepidermoid carcinoma of the salivary glands: An immunohistochemical study

Objectives

– Routine histopathological grading for salivary gland mucoepidermoid carcinoma (MEC) have failed to prognosticate these tumors, resulting in poor post-surgical outcomes. In developing countries, the lack of technologically advanced infrastructure curtails, efficient treatment modalities. This study aimed at determining if MUC4β can characterize salivary gland MEC and serve as a practical and inexpensive method to prognosticate salivary gland MEC.

Materials and methods

– Fifteen cases of archived paraffin embedded tissue blocks of mucoepidermoid carcinomas were reassessed for histopathological grading using Healey's system, modified by Batsakis and Luna and immunohistochemically evaluated for expression of MUC4β. Statistical analysis (Kappa statistics and Spearman's rho correlation coefficient) was performed to assess inter-observer reproducibility and to correlate the expression of MUC4β with the histopathological grade of the tumor.

Results

MUC4β expression is related to tumor differentiation in an inverse relationship. Two cases of high grade MEC were the exception to this rule.

Conclusion

Our study revealed that MUC4β alone cannot serve as a reliable prognostic marker due to its divergent tumor suppressor and oncogenic pathway. The role of MUC4β needs further evaluation and research so as to potentiate therapeutics depending upon its context dependent function, as a cancer marker or an oncogenic factor.

Mucoepidermoid Carcinoma of the Lacrimal Sac: Clinical-Pathologic Analysis, Including Molecular Genetics

Purpose

The aim of this study was to assess whether mucoepidermoid carcinoma of the lacrimal sac is a counterpart of CRTC1/3-MAML2 gene fusion-related salivary gland mucoepidermoid carcinoma.

Methods

In this retrospective observational case series, pathology records were searched for all cases of lacrimal sac mucoepidermoid carcinoma diagnosed between 1990 and 2018. Data collected included demographics, clinical findings, management, and follow-up. Pathologic parameters assessed included tumor morphology, immunohistochemistry, and MAML2 and EGFR fluorescence in situ hybridization (FISH) studies.

Results

Six patients with mucoepidermoid carcinoma of the lacrimal sac, 5 males and 1 female, with a median age of 63 years (range 24-66) were identified. Five tumors were managed with radical resection and 1 patient underwent orbital exenteration. None of the patients developed recurrence or metastases with an average follow-up of 18 months (range 13-23). All tumors had morphologic and immunohistochemical features of mucoepidermoid carcinoma and overexpressed EGFR. MAML2 FISH was negative for MAML2 rearrangement in all tumors. EGFR FISH demonstrated EGFR amplification in 1 tumor.

Conclusions

Mucoepidermoid carcinoma of the lacrimal sac is not a lacrimal sac counterpart of CRTC1/3-MAML2 gene fusion-related salivary gland mucoepidermoid carcinoma. EGFR pathway activation and EGFR amplification in a subset of these neoplasms suggest the potential role for anti-EGFR agents.

Genomics of mucoepidermoid and adenoid cystic carcinomas

Objective

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

Methods

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

Results and conclusions

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

Silymarin and its active component silibinin act as novel therapeutic alternatives for salivary gland cancer by targeting the ERK1/2-Bim signaling cascade

PURPOSE

Approximately 20% of all salivary gland cancer patients who are treated with current treatment modalities will ultimately develop metastases. Its most common form, mucoepidermoid carcinoma (MEC) is a highly aggressive tumor with an overall 5-year survival rate of ~30%. Until now, several chemotherapeutic drugs have been tested for the treatment of salivary gland tumors, but the results have been disappointing and the drugs often cause unwanted side effects. Therefore, several recent studies have focused on the potential of alternative and/or complementary therapeutic options, including the use of silymarin.

METHODS

The effects of silymarin and its active component silibinin on salivary gland cancer-derived MC3 and HN22 cells and their underlying molecular mechanisms were examined using trypan blue exclusion, 4'-6-diamidino-2-phenylindole (DAPI) staining, Live/Dead, Annexin V/PI staining, mitochondrial membrane potential (ΔΨm) measurement, quantitative RT-PCR, soft agar colony formation and Western blotting analyses.

RESULTS

We found that silymarin and silibinin dramatically increased the expression of the pro-apoptotic protein Bim in a concentration- and time-dependent manner and, concomitantly, induced apoptosis in MC3 and HN22 cells. We also found that ERK1/2 signaling inhibition successfully sensitized these cells to the apoptotic effects of silymarin and silibinin, which indicates that the ERK1/2 signaling pathway may act as an upstream regulator that modulates the silymarin/silibinin-induced Bim signaling pathway.

CONCLUSIONS

Taken together, we conclude that ERK1/2 signaling pathway inhibition by silymarin and silibinin increases the expression of the pro-apoptotic Bcl-2 family member Bim which, subsequently, induces mitochondria-mediated apoptosis in salivary gland cancer-derived cells.

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

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

Cytomegalovirus and Mucoepidermoid carcinoma: A possible causal relationship? A pilot study

BACKGROUND

Human cytomegalovirus (CMV) infection has tropism for salivary gland ductal epithelium and establishes a persistent and lifelong infection. Mucoepidermoid carcinoma (MEC) is the most common salivary gland tumor. Recent studies have established that mouse CMV-induced tumorigenesis displays histologic and molecular characteristics similar to human MEC. We wished to explore further down the lane by analyzing the expression of pp65 and the key oncogenic signaling pathway in cases of MEC and their etiological relevance in the Indian scenario as a pilot study.

MATERIALS AND METHODS

Histopathologically confirmed cases of MEC (n = 4) and normal salivary gland tissue (n = 4) were subjected to immunohistochemical analysis using the markers pp65 and epidermal growth factor receptor (EGFR).

RESULTS

The pp65 antigen expression was found to be negative in all the studied cases and one case of high-grade MEC showed EGFR expression.

CONCLUSION

The purpose of the study was to explore the role of CMV in the development of MEC, as it might help to exploit this etiological agent as a therapeutic target. Similar to human papillomavirus (HPV), these might identify a subset of neoplasms with a varied biological behavior and alternative therapies. However, this vision is obscured by contradicting evidence in the literature. As of today, surgery remains the only best possible management for these patients unless proven otherwise.

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

Background

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

Methods

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

Results

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

Conclusion

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

Electronic supplementary material

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

Pulmonary mucoepidermoid carcinoma in Chinese population: a clinicopathological and radiological analysis

BACKGROUND

Pulmonary mucoepidermoid carcinoma (PMEC) is a rare malignant neoplasm with remarkable resemblance to mucoepidermoid carcinoma of the salivary glands. It constitutes a unique set of patient population. In this study we briefly discussed the current state of knowledge of PMEC and described the clinical presentation and management of 27 PMEC cases. This study aimed to discuss the utility of surgical treatment in the patients with pulmonary mucoepidermoid carcinoma.

METHODS

We retrospectively studied 27 cases with the diagnosis of PMEC, divided into low grade and high grade based on histopathological characteristics. The clinical symptoms, radiological manifestations, pathological characteristics, treatment strategy and prognosis were systemically analyzed.

RESULTS

The tumor could occur in any lobe of the lungs. The treatment included surgical intervention and/or adjuvant therapies. While the sex-age distribution and initial staging was not different between low- and high- grade PMEC, the disease control rate (95%) and 5 year survival (95%) were much higher in low-grade PMEC than the high-grade cases (57.1% and 42.9%, respectively).

CONCLUSION

The clinical, radiographical and pathological features of PMECs were systemically analyzed and summarized, and the utility of pathological grading system as the independent prognostic factor in addition to clinical staging was confirmed.

CMV-induced pathology: pathway and gene-gene interaction analysis

Mucoepidermoid carcinoma (MEC) is the most prevalent malignant tumor in major and minor salivary glands (SGs). We have recently identified human cytomegalovirus (hCMV) as a principle component in the multifactorial causation of SG-MEC. This finding is corroborated by the ability of the purified mouse CMV (mCMV) to induce malignant transformation of SG cells in a three-dimensional in vitro mouse model, using a similar oncogenic signaling pathway. Our prior studies indicate that the core tumor microenvironment (TME) is a key regulator of pathologic progression, particularly the cancer-associated fibroblast (CAF) component. Studies of early CAFs immunodetect aberrant expression of ECM components, as well as multiple growth factors, cytokines and transcription factors. Here we present the mechanistic insight derived from a mathematical structure ("wiring diagram") used to model complex relationships between a highly relevant (p=9.43×10(-12)) global "cancer network" of 32 genes and their known links. Detailed characterization of the functional architecture of the examined "cancer network" exposes the critical crosstalk and compensatory pathways that limit the efficacy of targeted anti-kinase therapies.

Salivary mucoepidermoid carcinoma revisited

Clinicopathological features, prognosis and therapeutic strategies for mucoepidermoid carcinoma originating in salivary and salivary-type glands of the head and neck are reviewed. We emphasise histopathological aspects, appraise the value of histochemistry, electron microscopy, immunohistochemistry and cytophotometry, and discuss histogenesis and characteristic gene translocations. We additionally consider possible diagnostic difficulties, problems related to histological grading and accuracy of existing literature, and areas of controversy or uncertainty which may benefit from further investigations.

Aberrantly activated AREG-EGFR signaling is required for the growth and survival of CRTC1-MAML2 fusion-positive mucoepidermoid carcinoma cells

Salivary gland tumors (SGT) are a group of highly heterogeneous head and neck malignancies with widely varied clinical outcomes and no standard effective treatments. The CRTC1-MAML2 fusion oncogene, encoded by a recurring chromosomal translocation t(11;19)(q14-21;p12-13), is a frequent genetic alteration found in >50% of mucoepidermoid carcinomas (MEC), the most common malignant SGT. In this study, we aimed to define the role of the CRTC1-MAML2 oncogene in the maintenance of MEC tumor growth and to investigate critical downstream target genes and pathways for therapeutic targeting of MEC. By performing gene expression analyses and functional studies via RNA interference and pharmacological modulation, we determined the importance of the CRTC1-MAML2 fusion gene and its downstream AREG-EGFR signaling in human MEC cancer cell growth and survival in vitro and in vivo using human MEC xenograft models. We found that CRTC1-MAML2 fusion oncogene was required for the growth and survival of fusion-positive human MEC cancer cells in vitro and in vivo. The CRTC1-MAML2 oncoprotein induced the upregulation of the epidermal growth factor receptor (EGFR) ligand Amphiregulin (AREG) by co-activating the transcription factor CREB, and AREG subsequently activated EGFR signaling in an autocrine manner that promoted MEC cell growth and survival. Importantly, CRTC1-MAML2-positive MEC cells were highly sensitive to EGFR signaling inhibition. Therefore, our study revealed that aberrantly activated AREG-EGFR signaling is required for CRTC1-MAML2-positive MEC cell growth and survival, suggesting that EGFR-targeted therapies will benefit patients with advanced, unresectable CRTC1-MAML2-positive MEC.

Predictors of cervical lymph node metastasis in salivary gland cancer

BACKGROUND

This study compares clinicopathological parameters with novel molecular markers for predicting cervical lymph node metastasis in salivary gland cancer.

METHODS

Three hundred sixteen salivary gland carcinomas were included in this study. Genomic epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), phosphatase and tensin homolog (PTEN), and hepatocyte growth factor receptor (MET) was determined by fluorescence in situ hybridization (FISH). Chi-square tests, multivariate regression, and Kaplan-Meier survival analysis were used for statistics.

RESULTS

Nodal staging determines long-term survival. Clinicopathological parameters associated with positive neck nodes are advanced age (p = .006), T3/T4 classification, histological high-grade malignancy, and diagnosis of salivary duct carcinoma (p < .001 each). Neck node metastases also correlate with copy number gain of EGFR (p = .004) and HER2, aberration of MET, and deletion of PTEN (p < .001 each). Multivariate analysis showed SDC (p = .002) to be the strongest predictor of lymph node metastasis, followed by MET aberration (p = .009), T3/T4 classification (p = .017), PTEN deletion (p = .042), and adenocarcinoma not otherwise specified (NOS; p = .047).

CONCLUSION

The histological subtype is crucial for decisions regarding neck dissection. New molecular parameters may also indicate elective treatment of the neck.

Management of salivary gland tumors

Surgery after proper imaging (MRI or CT scan) is the main stay of treatment for salivary gland tumors. Although excision margins should be ≥5 mm for malignant tumors in cases of parotid gland carcinoma, the facial nerve should be preserved whenever it is not infiltrated. Adjuvant external radiation is indicated for malignant tumors with high-risk features such as close (or invaded) margins, perineural speed, lymphatic and/or vascular invasion, lymph-node involvement and high-grade histology. A Phase II trial testing adjuvant concomitant cisplatin plus radiation therapy versus adjuvant radiation therapy alone after surgery is currently under investigation for high-risk salivary gland cancer. For inoperable cancers, photons combined with proton boost seem to be a valuable option. Even if protons or carbon ions are promising, access to the latter is limited for usual treatment. For recurrent and/or metastatic cancer, polychemotherapy (cisplatin based) gives a 25% response rate in adenoid cystic carcinoma and should be used when the disease is overtly in progression. Targeted therapies with anti-EGF receptor molecules, antiangiogenic agents and tyrosine kinase inhibitors are ongoing, but more trials are needed to establish their efficacy, as is the use of bortezomib followed by doxorubicin. The products of fusion oncogenes, which have a pathogenic role in some adenoid cystic carcinoma and mucoepidermoid carcinomas, are of interest as potential therapeutic targets.

Cytomegalovirus-induced salivary gland pathology: resistance to kinase inhibitors of the upregulated host cell EGFR/ERK pathway is associated with CMV-dependent stromal overexpression of IL-6 and fibronectin

Background

Recently we identified a relationship between human cytomegalovirus (hCMV) and human salivary gland (SG) mucoepidermoid carcinoma (MEC) in over 90% of cases; tumorigenesis in these cases uniformly correlated with active hCMV protein expression and an upregulation of the EGFR → ERK pathway. Our previously characterized, novel mouse organ culture model of mouse CMV (mCMV)-induced tumorigenesis displays a number of histologic and molecular characteristics similar to human MEC.

Methods

Newborn mouse submandibular glands (SMGs) were incubated with 1 × 10⁵ PFU/ml of lacZ-tagged mCMV RM427+ on day 0 for 24 hours and then cultured in virus-free media for a total of 6 or 12 days with or without EGFR/ERK inhibitors and/or aciclovir. SMGs were collected for histology, immunolocalization (pERK, FN, IL-6), viral distribution, or Western blot analysis (pERK).

Results

Here we report: (1) mouse SMG tumors soon exhibit an acquired resistance to EGFR/ERK pathway kinase inhibitors, alone or in combination; (2) long term tumor regression can only be sustained by concurrent inhibitor and antiviral treatment; (3) CMV-dependent, kinase inhibitor resistance is associated with overexpression of fibronectin and IL-6 proteins in abnormal stromal cells.

Conclusions

Acquired resistance to kinase inhibitors is dependent upon CMV dysregulation of alternative pathways with downstream effectors common with the targeted pathway, a phenomenon with important therapeutic implications for human MEC of salivary glands.

The Molecular Pathology of Salivary Gland Tumors with Translocations

Presented here are the salivary gland tumors now recognized to have significant and highly prevalent translocations. These include both common and uncommon malignancies: mucoepidermoid carcinoma, adenoid cystic carcinoma, mammary analog secretory carcinoma, and clear cell carcinoma. These mutations have potential diagnostic applications, particularly in difficult and challenging variant morphologies are unusually challenging differential diagnoses. Practical applications of the molecular pathology of these tumors is discussed. The mutational assessment may also prove to have therapeutic importance, as targeted therapies may be generated for these tumors in the future.

Primary pulmonary mucoepidermoid carcinoma: an analysis of 21 cases

Background

The optimal treatment for pulmonary mucoepidermoid carcinoma (MEC), a rare type of tumor, has not been established yet. This study analyzed the survival of pulmonary MEC patients and attempted to find clues for optimal treatment.

Methods

A total of 21 patients with pulmonary MEC from November 2004 to January 2011 were included in the investigation. Immunohistochemistry, epidermal growth factor receptor (EGFR) mutation, and survival were retrospectively studied.

Results

Among the 21 pulmonary MEC patients, 17 were diagnosed with low-grade malignancy and 4 with high-grade malignancy through pathological examination. The prognosis was found to be poor in the presence of lymph nodes. The expression rates of EGFR and HER2 were 28.6% and 0%, respectively, which correlated with neither grade nor prognosis. The mutation rate of EGFR was 0. Log-rank test results indicated that age, grade, lymph node metastasis, and tumor-node-metastasis stage were prognostic factors.

Conclusion

Age, grade, lymph node metastasis and tumor-node-metastasis stage correlate with the survival of pulmonary MEC patients.

Trial registration

This study was approved and registered by the Ethics Committee of Zhongshan Hospital. Written informed consent was obtained from all participants prior to treatment.

Salivary gland carcinomas

INTRODUCTION

Salivary gland carcinomas are rare tumours of heterogeneous morphology that require distinctive surgical and adjuvant therapy.

METHODS

Relevant studies were electronically searched in PubMed and reviewed for innovative and important information.

RESULTS

Recent insights in genetic alterations like chromosomal aberrations, expression of receptor tyrosine kinases, malfunction of tumour suppressor genes or DNA promoter methylations increased the knowledge about aetiology and pathogenesis. New histological subtypes are recognised, and a three-tiered grading system seems reasonable. Ultrasound remains the basic diagnostic imaging procedure. New developments comprise the diffusion-weighed magnetic resonance imaging, while fluorodeoxyglucose positron emission tomography/computed tomography shows good diagnostic accuracy in detecting distant metastases and local recurrence. Fine-needle aspiration cytology helps in differentiating a neoplasia from a non-neoplastic lesion while being unreliable in recognising malignancy. In contrast, additional core needle biopsy and/or intraoperative frozen section diagnosis increase the accuracy in diagnosing a malignant lesion. Conservative parotid surgery with nerve monitoring remains state-of-the-art. Free flaps or musculoaponeurotic flaps are proposed for prevention of Frey's syndrome. As parotid cancer often shows skip metastases, complete ipsilateral neck dissection (level I-V) is indicated particularly in high-grade lesions. Adjuvant radio(chemo)therapy increases local tumour control, whereas overall survival is not necessarily improved. Current results of systemic chemotherapy or targeted therapy in advanced tumour stages are disappointing.

CONCLUSION

Despite several developments, salivary gland carcinomas remain a heterogeneous group of tumours challenging both pathologists and clinicians.

Loss of PTEN is associated with elevated EGFR and HER2 expression and worse prognosis in salivary gland cancer

Background:

Activity of the tumour-suppressor gene PTEN is reduced in different types of cancer and implicates non-responsiveness to targeted therapy. This study evaluates the gene and protein status of PTEN in salivary gland carcinomas.

Methods:

A total of 287 carcinomas of the major and minor salivary glands were investigated for phosphatase and tensin homologue located on chromosome 10 (PTEN) deletion and loss of PTEN expression using fluorescence in situ hybridisation (FISH) and immunohistochemistry (IHC), respectively. Results were correlated to clinicopathological parameters, long-term survival, epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) (IHC and FISH) status of the tumours.

Results:

Hemizygous deletions of PTEN were found in 35 out of 232 (15.1%) carcinomas, while homozygous deletions were observed in 17 out of 232 (7.3%) tumours. Phosphatase and tensin homologue located on chromosome 10 deletion was common in certain histological subtypes and especially homozygous deletion was associated with high-grade malignancy, lymph node metastases and unfavourable long-term prognosis (P<0.001). Loss of PTEN expression was present in 59 out of 273 (21.6%) carcinomas and was significantly correlated to genomic PTEN deletion, high-grade malignancy (P<0.001), increased tumour size (P=0.036), lymph node metastases (P=0.007) and worse disease-specific survival (P=0.002). Genomic PTEN deletion, in particular homogenous deletion (P<0.001) predominantly occurred in tumours with increased gene copy number of EGFR (60.0%) and/or amplification of HER2 (63.6%). Loss of PTEN expression was frequently found in tumours overexpressing EGFR (28.6%) and/or HER2 (52.6%).

Conclusion:

PTEN function is reduced in different types of salivary gland cancer indicating unfavourable prognosis. Its association with EGFR and HER2 signalling might affect targeted therapy.

EGFR, HER2, survivin, and loss of pSTAT3 characterize high-grade malignancy in salivary gland cancer with impact on prognosis

Increased gene copy number (high polysomy or amplification) of EGFR and HER2 has evolved as a predictor for response to targeted therapy. STAT3 and the apoptosis inhibitor survivin represent distinct oncogenes in various human neoplasms. The purpose of this study was to evaluate protein and gene status of these biomarkers by immunohistochemistry and dual color fluorescence in situ hybridization on tissue microarrays of 286 salivary gland carcinomas in the context of clinical and histopathologic characteristics. Diverse tumor types showed overexpression and increased gene copy number of EGFR and HER2. Amplification of HER2 was found in 35.5% of salivary duct carcinomas. Protein overexpression was strongly associated with high gene copy number for both EGFR and HER2 (P < .001). Overexpression and increased gene copy number of EGFR and HER2 were correlated to high-grade malignancy (P < .001) and unfavorable prognosis (P < .001). Strong nuclear staining of survivin was found in 18.9% of tumors and was associated with high-grade malignancy (P < .001), overexpression, and high gene copy number of EGFR and HER2 (P ≤ .05) as well as unfavorable prognosis (P < .001). Overexpression of nuclear pSTAT3 was found in 28.3% of tumors and correlated with well tumor differentiation (P < .001) and favorable prognosis (P = .001). Loss or weak expression of pSTAT3 was inversely associated with overexpression of survivin (P < .001) as well as overexpression and high gene copy number of EGFR and HER2 (P < .05). Overall, overexpression and increased gene copy number of EGFR and HER2 characterize high-grade malignancy with unfavorable prognosis in salivary gland cancer. Nuclear survivin typifies aggressive tumors with worse prognosis, whereas nuclear pSTAT3 might play a role as a tumor suppressor in absence of EGFR, HER2, and survivin.

Human cytomegalovirus and mucoepidermoid carcinoma of salivary glands: cell-specific localization of active viral and oncogenic signaling proteins is confirmatory of a causal relationship

Human cytomegalovirus (hCMV) infection is common. Although still controversial, there is growing evidence that active hCMV infection is associated with a variety of malignancies, including brain, breast, lung, colon, and prostate. Given that hCMV is frequently resident in salivary gland (SG) ductal epithelium, we hypothesized that hCMV would be important to the pathogenesis of SG mucoepidermoid carcinoma (MEC). This was initially supported by our finding that purified CMV induces malignant transformation in SG cells in an in vitro mouse model, and utilizes a pathogenic pathway previously reported for human MEC. Here we present the histologic and molecular characterizations of 39 human SG MECs selected randomly from a repository of cases spanning 2004-2011. Serial sections were obtained from formalin-fixed, paraffin embedded, tissue blocks from previous incisional or excisional biopsies. Immunohistochemical assays were performed for active hCMV proteins (IE1 and pp65) and the activated COX/AREG/EGFR/ERK signaling pathway. All four prospective causal criteria for viruses and cancer are fully satisfied: (1) protein markers for active hCMV are present in 97% of MECs; (2) markers of active hCMV are absent in non-neoplastic SG tissues; (3) hCMV-specific proteins (IE1, pp65) are in specific cell types and expression is positively correlated with severity; (4) hCMV correlates and colocalizes with an upregulation and activation of an established oncogenic signaling pathway (COX/AREG/EGFR/ERK). Thus, the evidential support reported here and previously in a mouse model is strongly confirmatory of a causal relationship between hCMV and SG mucoepidermoid carcinoma. To our knowledge, this is the first demonstration of hCMV's role in human oncogenesis that fully responds to all of Koch's Postulates as revised for viruses and cancer. In the absence of any contrary evidence, hCMV can reasonably be designated an "oncovirus."

Histologic grading and prognostic biomarkers in salivary gland carcinomas

Both the variety and rarity of salivary gland carcinomas pose challenge for using histologic grade and biomarkers to predict outcome. Mucoepidermoid carcinoma is the histologic subtype for which grading is most prognostically and therapeutically relevant. This tumor is graded using standard schemes in a 3-tier manner with the intermediate-grade category shows the most variability between grading systems and thus the most controversy in management. The t(11;19)(q21; p13) MECT1-MAML2 translocation may be an objective marker that can help to further stratify difficult cases. Adenoid cystic carcinomas are graded based on pattern with solid areas correlating with a worse prognosis. Occasionally, adenoid cystic carcinomas may undergo transformation to highly aggressive pleomorphic high-grade carcinomas with frequent nodal metastases. Comparative genomic hybridization has revealed several chromosomal regions (such as 1p32-p36, 6q23-q27) of prognostic interest in adenoid cystic carcinoma. Carcinoma ex-pleomorphic adenoma is actually a category of tumors rather than a single tumor type with both aggressive and indolent versions. These tumors should be further qualified as to type/grade of carcinoma and extent, as intracapsular and minimally invasive tumors behave favorably. Acinic cell carcinomas, although generally considered low grade, can recur, metastasize, or even prove lethal in a significant number of cases suggesting amenability to a grading scheme to separate these biologic groups. Although aggressive histologic parameters (anaplasia, necrosis, and mitoses) are predictive of poor outcome, a standard grading scheme does not yet exists. Acinic cell carcinomas can also undergo high-grade transformation.