Histogenesis of salivary gland neoplasms: a postulate with prognostic implications

Unusual Presentation of Adenoid Cystic Carcinoma of the Tongue: A Case Report and Review of the Literature

Adenoid cystic carcinoma (ACC) is a rare malignant tumor that affects the salivary glands. Its notable characteristics include aggressive local growth, infiltration of nerves (perineural invasion), a propensity to disseminate to other parts of the body (metastasize), and a high likelihood of recurrence. Here, we present the case of a 71-year-old male patient who presented with swelling on the posterior left side of his tongue, which had been causing him difficulty in chewing for the past six months. The parotid gland is frequently impacted in the head and neck area, with the tongue being comparatively uncommon. While distant metastasis is frequent, metastasis to nearby lymph nodes is not as common. However, if it does occur, it is associated with a poor prognosis and reduces the average survival age of the patient. The preferred treatment for ACC is surgical removal with wide resected margins. If it metastasizes to lymph nodes, then adjunct therapy is the treatment modality for the lesion. ACC exhibits three histopathological patterns: solid, tubular, and cribriform. The solid type is associated with a poorer prognosis compared to cribriform type, which typically has a better prognosis. This case, occurring on the tongue, is rare.

Observation Rather than Surgery for Benign Parotid Tumors: Why, When, and How

Surgery is the preferred treatment of benign parotid lesions, but it carries a risk of complications. Therefore, the approach toward the surgery of these lesions should seek to avoid complications. There are no guidelines or recommendations for when not to operate. Integration of comorbidities and other factors shift the scales from surgery toward observation in a small subset of patients presenting with parotid tumors. When observation is chosen, the patient should be followed frequently and cautiously, and the surgeon should be prepared to change strategy to surgical excision if in doubt.

Whole-Genome Sequencing of Common Salivary Gland Carcinomas: Subtype-Restricted and Shared Genetic Alterations

PURPOSE

Salivary gland carcinomas (SGCs) are pathologically classified into several widely diverse subtypes, of which adenoid cystic carcinoma (ACC), mucoepidermoid carcinoma (MEC), and salivary duct carcinoma (SDC) are the most commonly encountered. A comparative genetic analysis of these subtypes provides detailed information on the genetic alterations that are associated with their tumorigenesis and may lead to the identification of biomarkers to guide tumor-specific clinical trials.

EXPERIMENTAL DESIGN

Whole-genome sequencing of 58 common SGCs (20 ACCs, 20 SDCs, and 18 MECs) was performed to catalog structural variations, copy number, rearrangements, and driver mutations. Data were bioinformatically analyzed and correlated with clinicopathologic parameters, and selected targets were validated.

RESULTS

Novel and recurrent type-specific and shared genetic alterations were identified within and among 3 subtypes. Mutually exclusive canonical fusion and nonfusion genomic alterations were identified in both ACC and MEC. In ACCs, loss of chromosome 12q was dominant in MYB or MYBL1 fusion-positive tumors and mutations of NOTCH pathway were more common in these fusion negatives. In MECs, CRTC1-MAML2 fusion-positive tumors showed frequent BAP1 mutation, and tumors lacking this fusion were enriched with LRFN1 mutation. SDCs displayed considerable genetic instability, lacked recurrent chromosomal rearrangements, and demonstrated nonoverlapping TP53 mutation and ERBB2 amplification in a subset of tumors. Limited genetic alterations, including focal amplifications of 8q21-q23, were shared by all subtypes and were associated with poor survival.

CONCLUSIONS

This study delineates type-specific and shared genetic alterations that are associated with early phenotypic commitment and the biologic progression of common SGCs. These alterations, upon validation, could serve as biomarkers in tumor-specific clinical trials.

Oncogenic Orphan Nuclear Receptor NR4A3 Interacts and Cooperates with MYB in Acinic Cell Carcinoma

Acinic cell carcinoma (AcCC) is a morphologically distinctive salivary gland malignancy often associated with chromosome rearrangements leading to overexpression of the NR4A3 transcription factor. However, little is known about how NR4A3 contributes to AcCC biology. Detailed RNA-sequencing of 21 archived AcCC samples revealed fusion reads arising from recurrent t(4;9), t(9;12), t(8;9) or t(2;4) chromosomal translocations, which positioned highly active enhancers adjacent to the promoter of the NR4A3 gene or the closely related NR4A2 gene, resulting in their aberrant overexpression. Transcriptome analyses revealed several distinct subgroups of AcCC tumors, including a subgroup that overexpressed both NR4A3 and MSANTD3. A poor survival subset of the tumors with high-grade transformation expressed NR4A3 and POMC as well as MYB, an oncogene that is the major driver in a different type of salivary gland tumor, adenoid cystic carcinoma. The combination of NR4A3 and MYB showed cooperativity in regulating a distinct set of genes. In addition, the ligand binding domain of NR4A3 directly bound the Myb DNA binding domain. Transformation assays indicated that, while overexpressed NR4A3 was sufficient to generate transformed colonies, the combination of NR4A3 plus Myb was more potent, leading to anchorage-independent growth and increased cellular invasiveness. The results confirm that NR4A3 and NR4A2 are the main driver genes of AcCC and suggest that concurrent overexpression of NR4A3 and MYB defines a subset of AcCC patients with high-grade transformation that display exceptionally poor outcome.

Bronchoscopic management of a primary endobronchial salivary epithelial-myoepithelial carcinoma: A case report

Here, we discussed a 55 y/o African man who recently immigrated from Nigeria to the United States and who presented to Parkland Memorial Hospital with a productive, intermittent cough of one year duration. The cough was associated with shortness of breath and chest pain. Cough was not associated with voice hoarseness, hemoptysis, melanoptysis, and wheezing. He had a computed tomography (CT) scan of the chest that showed a 1.9 cm mass in the right main stem bronchus with ipsilateral right lower lobe consolidation and bronchiectasis. The patient was seen by pulmonology who recommended bronchoscopy for diagnosis and possible intervention. Bronchoscopy showed a 90% obstructing mass in the proximal right mainstem bronchus and bronchus intermedius. The mass was large and endobronchial, circumferential, exophytic, and polypoid. The decision was made to undergo bronchoscopic tumor ablation using electrocautery snare, argon plasma coagulation (APC), suction, and forceps. The tumor was successful ablated. Microscopic examination revealed eosinophilic ducts tightly coupled with a surrounding layer of clear cell myoepithelial cells and the diagnosis of epithelial-myoepithelial carcinoma (EMC) of the lung was made. The patient was discharged from the hospital with scheduled outpatient visits for monitoring of the carcinoma by pulmonology and thoracic surgery. Unfortunately, he was lost to follow up.

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Primary salivary epithelial-myoepithelial carcinoma are extremely rare malignancies found in the airways.

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This type of tumor can be seen in patients who present with chronic cough without other symptomatology.

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Although management is primarily surgical, here we report the successful bronchoscopic removal of this malignancy.

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There were no complications following the bronchoscopic removal of the tumor.

Spatio-Temporal Genomic Heterogeneity, Phylogeny, and Metastatic Evolution in Salivary Adenoid Cystic Carcinoma

Background

Adenoid cystic carcinoma (ACC), an uncommon and indolent salivary gland malignancy, is characterized by varied morphologic and clinical manifestations. Molecular genetic studies of ACC identified certain structural and mutational alterations that may play a driver role in tumor development. The evolution and regional consistency of these events in ACC development progression are uncertain.

Methods

To investigate the spatial and temporal clonal landscape of ACC, whole-genome sequencing and variant analyses were performed on 34 regionally sampled primary tumors and their concurrent and metachronous metastatic deposits from eight patients.

Results

The average mutation rate per case (primary and metastasis) was 0.32 per million base pairs, and the average incidence of shared mutations in primary and metastatic specimens in each case was 21.9% (range = 0%-44.4%). The analyses revealed considerable spatial clonal differences within and between primary tumors and metastatic disease. Phylogeny formation displayed branching evolution with a main trunk and two distinct mono-splits in all cases. One of the main branches represented intratumor subclonal diversity, and the other delineated metastatic departure and progression. All metastatic tumors shared clonal linkage to their matching primary in concordance with parallel dissemination of metastasis. Synchronous metastases were genomically more similar to their primary than metachronous metastatic disease. Truncal genetic alterations included somatic mutations in the NOTCH pathway genes (NOTCH1 and SPEN) and t(6;9) associated gene fusions.

Conclusions

Our study delineated clonal and subclonal phylogeny for primary and metastatic ACC, defined early genetic drivers, and provides a conceptual framework for a rational strategy to integrate heterogeneity in clinical assessment.

Does laser phototherapy influence the proliferation of myoepithelial cells in the salivary gland of hypothyroid rats?

Thyroid hormones influence both development and growth of organs and tissues and guarantee metabolic demands that interfere with the quality of digestive secretions, including those of the salivary glands. Laser phototherapy - LPT can modulate various biological phenomena and its diverse effects permit the action on different cell types. The aim of this study was to evaluate the influence of laser phototherapy on myoepithelial cells of salivary glands of hypothyroid rats. Forty-two albino Wistar rats were divided into two main groups: euthyroid (EU) and hypothyroid (HYPO). Hypothyroidism was induced using propylthiouracil (PTU) for 4weeks. Each group was divided into subgroups: control (without laser) and laser groups (Red/infrared - IR). LPT was used on the submandibular gland and was carried out using a diode laser (λ660 or λ780nm, 40mW, spot size 0.04cm², irradiation area 1cm², 300s, 6J/cm² per gland, 12J/cm² per session) and started two weeks after PTU treatment. LPT was repeated every other day for two weeks. After animal death, the glands were removed, dissected and processed for immunohistochemical analysis. It was observed an increase in the number of myoepithelial cells of hypothyroid control rats in comparison to euthyroid controls (p=0.001). Visible LPT (λ660nm) caused significant higher proliferation of myoepithelial cells in EU rats when compared to IR LPT (λ 780nm)(p≤0.001).It is concluded that, despite the LPT protocol used did not influence myoepithelial proliferation on hypothyroid rats it significantly increased the proliferation on euthyroid animals.

Regenerative capacity of allogenic gingival margin- derived stem cells with fibrin glue on albino rats' partially dissected submandibular salivary glands

OBJECTIVE

To evaluate the possible regenerative effect of allogenic gingival margin-derived stem cells (GMSCs) with or without autologous fibrin glue on partially dissected submandibular salivary glands of albino rats.

METHODS

Forty rats were randomly divided into four equal groups. Group I, where no operation was performed, was considered the negative control. Group II rats were considered the positive control and were subjected to a rectangular cut on the outer surface of the center right of the submandibular salivary gland and received no other treatment. Groups III and IV rats were handled as those in group II, but the cut areas of group III were filled with fibrin glue and the cut borders of group IV were injected with 1×10⁵cell/ml GMSCs and then glued with fibrin glue. Five animals from each group were euthanized at the end of the first postoperative week, while the remaining animals were euthanized at the end of the second postoperative week, i.e., end of the experiment.

RESULTS

Regeneration of ductal, acinar, and myoepithelial cells was better in group IV. A two-way ANOVA for proliferating cell nuclear antigen and α-smooth muscle actin revealed an overall significant difference between the different groups (P<0.05). In addition, an LSD post hoc test for multiple comparisons revealed a significant difference between each two groups. An independent sample t-test revealed significant differences between time periods for groups II, III, and IV, but there were no significant differences between the time periods for group I.

CONCLUSION

Injecting GMSCs at the cut borders and gluing the cut area with autologous fibrin glue ameliorates the regeneration of partially dissected submandibular salivary gland better than using fibrin glue alone.

Mutational landscape of lacrimal gland carcinomas and implications for treatment

BACKGROUND

Lacrimal gland carcinomas are rare. Identification of molecular abnormalities underlying lacrimal gland carcinogenesis is critical to the development of new targeted therapies for lacrimal gland carcinomas. The purpose of our study was to look for mutations that can be targeted as new treatments for lacrimal gland carcinomas.

METHODS

Genomic DNA from patients with lacrimal gland epithelial neoplasms was analyzed. The Sequenom matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass ARRAY platform was used to profile 168 common oncogenic point mutations in 40 genes. Mutation frequency was assessed overall and by histologic diagnosis. These genetic mutations were then correlated with clinical outcomes in the patients.

RESULTS

The study included 14 men and 10 women with a median age of 45 years (range, 17-75 years). The histologic diagnoses were as follows: adenoid cystic carcinoma (n = 16), low-grade carcinoma ex pleomorphic adenoma (n = 2), high-grade carcinoma ex pleomorphic adenoma (n = 2), squamous carcinoma (n = 1), and pleomorphic adenoma (n = 3). Analysis revealed 18 oncogenic mutations in 13 patients: KRAS mutations in 10 patients (46%), NRAS mutations in 2 patients (8%), MET mutations in 3 patients (13%), PIK3CA mutation in 1 patient (4%), and BRAF mutation in no patients. About half of the patients with adenoid cystic carcinoma had oncogenic mutations (7 of 16; 44%). Of the 16 patients with adenoid cystic carcinoma, 5 had KRAS mutations, 1 had MET mutations, and 1 had an NRAS mutation.

CONCLUSION

KRAS, NRAS, and MET mutations are frequent in epithelial neoplasms of the lacrimal gland, with the highest rate of mutations found in adenoid cystic carcinoma. Therapies targeting these genes may be effective treatments for lacrimal gland carcinomas. © 2015 Wiley Periodicals, Head Neck 38: E-E, 2016.

The role of Nrf2 in pathology of pleomorphic adenoma in parotid gland

Background

Pleomorphic adenoma (benign mixed tumor) is one of the most common salivary gland tumors. However, the processes involved in its carcinogenesis are not well defined. This study aimed to define the contribution of Nfr2 (nuclear factor (erythroid-derived 2)-like 2) to pleomorphic adenoma pathology. The Nrf2-controlled gene system is one of the most critical cytoprotective mechanisms, providing antioxidant responses.

Material/Methods

The study was carried out in pleomorphic adenoma and control parotid gland tissues, investigating gene expression of NFE2L2, as well as KEAP1 (Kelch-like ECH-associated protein 1) and NQO1 (quinone oxidoreductase), at mRNA and protein (immunohistochemistry) levels. Functional evaluation of Nrf2 system in the parotid gland was evaluated in HSY cells (human parotid gland adenocarcinoma cells).

Results

Pleomorphic adenoma specimens showed cytoplasmic and nuclear Nfr2 expression in epithelial cells, as well as more variable lower Nrf2 level in mesenchymal cells. In the parotid gland, Nrf2 was expressed in cytoplasm of serous, mucous, and duct cells. Nuclear Nrf2 expression was predominantly seen in serous cells, whereas mucous and duct cells were mostly negative. Comparable mRNA levels of NFE2L2 and NQO1 genes and significantly higher expression of KEAP1 in pleomorphic adenoma were seen. HSY cell incubation with oltipraz demonstrated significant elevation of NFE2L2 after 24 and 48 hours of stimulation, whereas NQO1 was elevated, but significantly only after 24 hours, and KEAP1 expression remained unchanged.

Conclusions

Summarizing both in vitro and in vivo observations, it can be stated that Nrf2 may play a role in the pathology of pleomorphic adenoma.

Alterations associated with androgen receptor gene activation in salivary duct carcinoma of both sexes: potential therapeutic ramifications

PURPOSE

To investigate the molecular events associated with the activation of androgen receptor (AR) as a potential therapeutic target in patients with salivary duct carcinoma (SDC).

EXPERIMENTAL DESIGN

Comprehensive molecular and expression analysis of the AR gene in 35 tumor specimens (20 males and 15 females) and cell lines derived from SDC using Western blotting and RT-PCR, FISH analysis, and DNA sequencing was conducted. In vitro and in vivo animal studies were also performed.

RESULTS

AR expression was detected in 70% of the tumors and was mainly nuclear and homogenous in both male and female SDCs, although variable cytoplasmic and/or nuclear localization was also found. We report the identification of ligand-independent AR splice variants, mutations, and extra AR gene copy in primary untreated SDC tumors. In contrast to prostate cancer, no AR gene amplification was observed. In vitro knockdown of AR in a female derived SDC cell line revealed marked growth inhibition in culture and in vivo androgen-independent tumor growth.

CONCLUSIONS

Our study provides new detailed information on the molecular and structural alterations associated with AR gene activation in SDC and sheds more light on the putative functional role of AR in SDC cells. On the basis of these data, we propose that patients with SDC (male and female) can be stratified for hormone-based therapy in future clinical trials.

The Justy mutant mouse strain produces a spontaneous murine model of salivary gland cancer with myoepithelial and basal cell differentiation

We previously identified a novel mutant mouse strain on the C3HeB/FeJ background named Justy. This strain bears a recessive mutation in the Gon4l gene that greatly reduces expression of the encoded protein, a nuclear factor implicated in transcriptional regulation. Here, we report that Justy mutant mice aged 6 months or older spontaneously developed carcinomas with myoepithelial and basaloid differentiation in salivary glands with an incidence of ∼25%. Tumors developed proximate to submandibular glands and to a lesser extent in the sublingual and parotid glands. Histologically, tumors often had central cavitary lesions filled with necrotic debris that were lined by tumor cells, and had spindle and epithelioid cell differentiation with lesser basaloid to clear cell features. Tumor tissue often had variable evidence of a high mitotic rate, pleomorphism, and invasion into adjacent salivary glands. Neoplastic cells had diffuse immunoreactivity for pancytokeratin (AE1/AE3) and p63. Although CK5/6 immunostaining was seen in the much of the tumor cells, it was often lacking in pleomorphic areas. Tumor cells lacked immunoreactivity for alpha-smooth muscle actin, S100, c-Kit, and glial fibrillary acid protein. In addition, tumors had immunoreactivity for phosphorylated and total epidermal growth factor receptor, suggesting that EGFR signaling may participate in growth regulation of these tumors. These findings indicate that the salivary gland carcinomas occur spontaneously in Justy mice, and that these tumors may offer a valuable model for study of EGFR regulation. In combination, our data suggest that Justy mice warrant further investigation for use as a mouse model for human salivary gland neoplasia.

CD24 and CD44 in salivary gland pleomorphic adenoma and in human salivary gland morphogenesis: differential markers of glandular structure or stem cell indicators?

AIMS

Salivary gland neoplasms originate from salivary gland compartments, to which they are histologically related. Pleomorphic adenoma (PA) is a benign salivary gland neoplasm that comprises epithelial and myoepithelial cells and a complex stroma, whose structure, architecture and origin (from intercalated ducts) suggest stem cell participation. We compared the expression of CD24 and CD44 in PA and in developing human salivary glands to investigate whether these markers can be considered as cancer stem cell markers.

METHODS AND RESULTS

One hundred and one cases of PA and salivary gland specimens from 20 human fetuses were examined by immunohistochemistry and real-time reverse transcription polymerase chain reaction (RT-PCR). All PAs were positive for CD24 and CD44 by immunohistochemistry: neoplastic luminal structures were positive for CD24; modified myoepithelial cells were positive for CD44. In fetal salivary glands, these markers were restricted to the intercalated duct region. Real-time RT-PCR assays detected increased expression of CD44, but not CD24, in PA specimens in comparison with normal salivary gland controls.

CONCLUSIONS

PA and stem cells share the expression of CD24 and CD44; their value as markers of neoplastic cell multipotency and the implications of their expression for tumour behaviour are yet to be determined.

Detailed genome-wide SNP analysis of major salivary carcinomas localizes subtype-specific chromosome sites and oncogenes of potential clinical significance

The molecular genetic alterations underlying the development and diversity of salivary gland carcinomas are largely unknown. To characterize these events, comparative genomic hybridization analysis was performed, using a single-nucleotide polymorphism microarray platform, of 60 fresh-frozen specimens that represent the main salivary carcinoma types: mucoepidermoid carcinoma (MEC), adenoid cystic carcinoma (ACC), and salivary duct carcinoma (SDC). The results were correlated with the clinicopathologic features and translocation statuses to characterize the genetic alterations. The most commonly shared copy number abnormalities (CNAs) in all types were losses at chromosomes 6q23-26 and the 9p21 region. Subtype-specific CNAs included a loss at 12q11-12 in ACC and a gain at 17q11-12 in SDC. Focal copy number losses included 1p36.33-p36-22 in ACC, 9p13.2 in MEC, and 3p12.3-q11-2, 6q21-22.1, 12q14.1, and 12q15 in SDC. Tumor-specific amplicons were identified at 11q23.3 (PVRL1) in ACC, 11q13.3 (NUMA1) in MEC, and 6p21.1 (CCND3), 9p13.2 (PAX5), 12q15 (CNOT2/RAB3IP), 12q21.1 (GLIPR1L1), and 17q12 (ERBB2/CCL4) in SDC. A comparative CNA analysis of fusion-positive and fusion-negative ACCs and MECs revealed relatively lower CNAs in fusion-positive tumors than in fusion-negative tumors in both tumor types. An association between CNAs and high grade and advanced stage was observed in MECs only. These findings support the pathogenetic segregation of these entities and define novel chromosomal sites for future identification of biomarkers and therapeutic targets.

Salivary gland cancers: biology and molecular targets for therapy

Salivary gland carcinomas are a heterogeneous group of tumors with different biologic behavior. Given the lack of large randomized studies, there is no standard treatment for advanced and/or metastatic salivary gland tumors, and systemic therapy is empirically based. Tumor-specific recurrent chromosomal translocations and fusion oncogenes in aggressive head and neck malignancies have diagnostic, therapeutic, and prognostic implications. Pathognomonic fusion transcripts have been identified in subsets of mucoepidermoid carcinoma and adenoid cystic carcinoma. These translocations target 1) transcription factors involved in growth factor signaling and cell cycle regulation, 2) transcriptional co-activators, and 3) tyrosine kinase receptors. Prioritizing studies with a translational component to advance the molecular understanding of these cancers and molecular-targeted therapy clinical trials is critical.

Novel therapeutic strategies for malignant salivary gland tumors: lessons learned from breast cancer

Malignant salivary gland tumors (MSGTs) account for 2–6% of all head and neck cancers. Despite the rarity, MSGTs have been of great interest due to a wide variety of pathological features and high metastasis rates resulting in poor prognosis. Surgical resection followed by radiation therapy represents the main treatment of this malignancy. Adjuvant therapy is reserved for the management of local recurrence, no longer amenable to additional local therapy, and for metastasis. Based on the studies from other types of tumors, particularly breast cancer, the expression and function of sex steroid hormone receptors in cancer have been extensively studied and applied to diagnosis and treatment. Although a number of studies in MSGTs have been published, the rationale for hormone therapy is still controversial due to the disparate results and insufficient number of cases. However, some recent reports have demonstrated that certain salivary gland neoplasms are similar to breast cancer, not only in terms of the pathological features, but also at the molecular level. Here, we shed light on the biological similarity between MSGTs and certain types of breast cancer, and describe the potential use of hormone and additional therapies for MSGTs.

P27/SKP-2 histochemical profile is relevant to malignant salivary gland tumors (MST) histogenesis and tumor grade

Malignant salivary gland tumors (MST) represent over more than 24 distinct morphological subtypes. Most high grade tumors arise from the excretory duct portion of the salivary gland apparatus; the remainder from the intercalated duct portion. Altered p27/skp-2 expression has been associated with tumor aggressiveness and histologic differentiation. In our study, we analyzed p27/skp-2 expression proteins on series of malignant salivary gland tumors in order to assess their value as a histogenetic marker, which is relevant to tumor grade. 61 MST cases were segregated by proposed histogenesis and immunohistochemistry was performed using antibodies directed against p27 and skp-2. MST of proposed intercalated duct origin (n=27) showed strong p27 expression (n=25/27; 93%) in the vast majority of cases and all cases weakly expressed skp-2. MST of proposed excretory duct origin (n=32) showed strong p27 expression (n=18/32; 56%) and moderately strong/strong skp-2 expression (n=18/32; 56%), respectively, in over half the cases. MST of intercalated duct origin showed evident p27/skp-2 inverse correlation. Differences in p27/skp-2 expression among the MST subtypes correlated with histogenesis and tumor grade, which reinforces the notion that tumor behavior is relevant to the portion of the salivary gland unit from which they arise. MST of proposed intercalated duct origin strongly expressed p27, and not skp-2, unlike MST of proposed excretory duct origin. The immunohistochemical profile of high grade mucoepidermoid carcinoma was distinct from its low/intermediate grade counterparts, suggesting a separate identity. These results may influence future decision making when formulating workable MST categorization schemes. Further studies on a larger series of MST are warranted in order to support the value of our findings.

Novel chromosomal rearrangements and break points at the t(6;9) in salivary adenoid cystic carcinoma: association with MYB-NFIB chimeric fusion, MYB expression, and clinical outcome

OBJECTIVE

To investigate the molecular genetic heterogeneity associated with the t(6:9) in adenoid cystic carcinoma (ACC) and correlate the findings with patient clinical outcome.

EXPERIMENTAL DESIGN

Multimolecular and genetic techniques complemented with massive pair-ended sequencing and single-nucleotide polymorphism array analyses were used on tumor specimens from 30 new and 52 previously analyzed fusion transcript-negative ACCs by reverse transcriptase PCR (RT-PCR). MYB mRNA expression level was determined by quantitative RT-PCR. The results of 102 tumors (30 new and 72 previously reported cases) were correlated with the clinicopathologic factors and patients' survival.

RESULTS

The FISH analysis showed 34 of 82 (41.5%) fusion-positive tumors and molecular techniques identified fusion transcripts in 21 of the 82 (25.6%) tumors. Detailed FISH analysis of 11 out the 15 tumors with gene fusion without transcript formation showed translocation of NFIB sequences to proximal or distal sites of the MYB gene. Massive pair-end sequencing of a subset of tumors confirmed the proximal translocation to an NFIB sequence and led to the identification of a new fusion gene (NFIB-AIG1) in one of the tumors. Overall, MYB-NFIB gene fusion rate by FISH was in 52.9% whereas fusion transcript forming incidence was 38.2%. Significant statistical association between the 5' MYB transcript expression and patient survival was found.

CONCLUSIONS

We conclude that: (i) t(6;9) results in complex genetic and molecular alterations in ACC, (ii) MYB-NFIB gene fusion may not always be associated with chimeric transcript formation, (iii) noncanonical MYB-NFIB gene fusions occur in a subset of tumors, (iv) high MYB expression correlates with worse patient survival.

Expression and regulation of the ΔN and TAp63 isoforms in salivary gland tumorigenesis clinical and experimental findings

The TP63 gene, a TP53 homologue, encodes for two main isoforms by different promoters: one retains (TA) and the other lacks (ΔN) the transactivation domain. p63 plays a critical role in the maintenance of basal and myoepithelial cells in ectodermally derived tissues and is implicated in tumorigenesis of several neoplastic entities. However, the biological and regulatory roles of these isoforms in salivary gland tumorigenesis remain unknown. Our results show a reciprocal expression between TA and ΔN isoforms in both benign and malignant salivary tumors. The most dominantly expressed were the ΔN isoforms, whereas the TA isoforms showed generally low levels of expression, except in a few tumors. High ΔNp63 expression characterized tumors with aggressive behavior, whereas tumors with high TAp63 expression were significantly smaller and less aggressive. In salivary gland cells, high expression of ΔNp63 led to enhanced cell migration and invasion and suppression of cell senescence independent of TAp63 and/or TP53 gene status. We conclude the following: i) overexpression of ΔNp63 contributes to salivary tumorigenesis, ii) ΔNp63 plays a dominant negative effect on the TA isoform in the modulation of cell migration and invasion, and iii) the ΔN isoform plays an oncogenic role and may represent an attractive target for therapeutic intervention in patients with salivary carcinomas.

Comprehensive analysis of the MYB-NFIB gene fusion in salivary adenoid cystic carcinoma: Incidence, variability, and clinicopathologic significance

PURPOSE

The objectives of this study were to determine the incidence of the MYB-NFIB fusion in salivary adenoid cystic carcinoma (ACC), to establish the clinicopathologic significance of the fusion, and to analyze the expression of MYB in ACCs in the context of the MYB-NFIB fusion.

EXPERIMENTAL DESIGN

We did an extensive analysis involving 123 cancers of the salivary gland, including primary and metastatic ACCs, and non-ACC salivary carcinomas. MYB-NFIB fusions were identified by reverse transcriptase-PCR (RT-PCR) and sequencing of the RT-PCR products, and confirmed by fluorescence in situ hybridization. MYB RNA expression was determined by quantitative RT-PCR and protein expression was analyzed by immunohistochemistry.

RESULTS

The MYB-NFIB fusion was detected in 28% primary and 35% metastatic ACCs, but not in any of the non-ACC salivary carcinomas analyzed. Different exons in both the MYB and NFIB genes were involved in the fusions, resulting in expression of multiple chimeric variants. Notably, MYB was overexpressed in the vast majority of the ACCs, although MYB expression was significantly higher in tumors carrying the MYB-NFIB fusion. The presence of the MYB-NFIB fusion was significantly associated (P = 0.03) with patients older than 50 years of age. No correlation with other clinicopathologic markers, factors, and survival was found.

CONCLUSIONS

We conclude that the MYB-NFIB fusion characterizes a subset of ACCs and contributes to MYB overexpression. Additional mechanisms may be involved in MYB overexpression in ACCs lacking the MYB-NFIB fusion. These findings suggest that MYB may be a specific novel target for tumor intervention in patients with ACC.

A study of HER-2/neu expression and silver binding nucleolar organizer regions (Ag NORs) in perilesional normal salivary gland tissue

Salivary gland neoplasms comprise phenotypically and biologically diverse lesions of uncertain histogenesis.

OBJECTIVES

The present study was carried out to assess the immunohistochemical expression of HER-2/neu protein and of silver binding nucleolar organizer regions in normal salivary tissue.

MATERIALS AND METHODS

Twenty paraffin blocks of salivary tumors containing surrounding normal salivary tissue were used in the study. One section was processed to investigate HER-2/neu protein expression and another section was stained to assess the mean Ag NOR counts in normal salivary tissue.

RESULTS

Only two cases of the studied normal salivary tissue showed HER-2/neu expression (10%), which was expressed only in ductal cells with 4.2 ± 2.1 mean number of reactive cells per five high power fields (HPFs). Statistically significant (P = 0.01) higher mean Ag NOR counts in ductal (2 ± 0.83) than in acinar cells (1.2 ± 0.01) of normal salivary tissue were found.

CONCLUSION

It was concluded from the data of the present study that ductal cells of normal salivary tissue are a proliferative pool and an oncogenic target which plays an important role in the histogenesis of salivary gland tumors.

Calponin expression in laryngeal myoepithelial carcinoma and its prognostic implications: a case report and literature review

A case report of laryngeal myoepithelial carcinoma (MEC) is presented and the literature concerning prognostic factors in MEC is reviewed. A 61-year old man was admitted to hospital with hoarseness and progressive dyspnoea. On examination, both vocal cords were fixed in the midline with a glottic fissure of only 3 mm. No tumour was seen, but the subglottis was not completely visible. A computed tomography scan showed a soft mass below the right vocal cord obstructing two-thirds of the larynx. On suspension laryngoscopy, a dull mass (1.5 x 1.5 cm) was seen below the right vocal cord, which was malignant on frozen biopsy. A total laryngectomy was performed and the patient received radiotherapy. He died of recurrence 25 months later. The tumour was positive for cytokeratin 14, S-100 protein and calponin. MEC of the larynx is extremely rare. The clinical behaviour of MEC is variable and prognostic factors have been poorly analysed. Calponin expression may be a prognostic factor, but other factors also affect the outcome in MEC.

Quantitative promoter hypermethylation analysis of cancer-related genes in salivary gland carcinomas: comparison with methylation-specific PCR technique and clinical significance

PURPOSE

To compare the methylation status of tumor-associated genes by quantitative pyrosequencing and qualitative methylation-specific PCR (MSP) techniques and to correlate the results with clinicopathologic features and patients outcome to determine which method might have greater clinical utility.

EXPERIMENTAL DESIGN

The hypermethylation status of the retinoid acid receptor beta2 (RARbeta2), RAS association domain family 1A (RASSF1A), O(6)-methylguanine-DNA methyltransferase (MGMT), and E-cadherin genes was analyzed in five salivary carcinoma cell lines and 69 human salivary gland carcinoma specimens by pyrosequencing and MSP techniques. The two datasets were compared by linear regression. Correlations between methods and with clinicopathologic characteristics were assessed by Pearson's chi(2) test or the two-tailed Fisher exact test, as applicable, using cutoff points determined from the regression curves and empirical fitting. We also investigated the effect of demethylating agents on methylated genes in cell lines to assess their effect on the expression of these genes.

RESULTS

Overall, regression analysis indicated high degrees of correlation of the two methods for measurement of methylation for the RARb2, RASSF1A, and MGMT genes (adjusted R(2) = 0.319, 0.835, and 0.178; P < 0.001, <0.001, and 0.0002, respectively) among the 69 tumors tested. However, the pyrosequencing technique yielded four more instances of methylation above background levels than MSP for RARbeta2 and three more for RASSF1. Methylation of either RARbeta2 and RASSF1A alone or both by pyrosequencing were correlated with tumor type (P = 0.027, 0.014, and 0.012, respectively). Methylation of RARbeta2 alone and in combination with RASSF1A by pyrosequencing were also significantly correlated with tumor grade (P = 0.014 and 0.011, respectively) and 3-year survival (P = 0.002 and 0.004, respectively). The survival curves of patients who had hypermethylation at both RARbeta2 and RASSF1A were significantly lower than those of patients who had hypermethylation at neither or just for the RASSF1A (P = 0.008 and 0.007, respectively). 5-Azadeoxycytidine treatment of methylated cell lines led to the reactivation of RARbeta2 expression in only one of the five cell lines.

CONCLUSIONS

(a) Although the methylation status of RARb2, RASSF1A, and MGMT genes by both techniques were significantly correlated, pyrosequencing is generally more sensitive and its results correlate better with the clinical variables than those of MSP. (b) The methylation level of the RARbeta2 and/or RASSF1A by pyrosequencing is significantly associated with aggressive tumor phenotypes and patients survival.

Salivary gland malignancies: the role for chemotherapy and molecular targeted agents

Salivary gland tumors are a rare and clinically diverse group of neoplasms that represent less than 1% of all malignancies. In locoregional recurrent or metastatic disease, systemic therapy is the standard approach. Numerous phase II studies with small sample sizes have assessed the activity of different cytotoxic agents, either alone or in combination. For these agents, the objective response rates are generally modest, ranging from 15% to 50%. Duration of response is typically cited in the range of 6 to 9 months. Further evaluation of novel therapies is mandated in this disease. With the emergence of molecular targeted therapy, these tumors become optimal candidates for trials of investigational drugs and established drugs for new indications. Often, salivary gland carcinomas are indolent. As such, one should wish only to treat patients with progressive disease. Study designs must incorporate stringent inclusion criteria to enable accurate reporting of disease response and stabilization, especially in the evaluation of new drugs and novel combinations. Salivary gland-focused cooperative groups are necessary in order to accrue patients to these clinical trials and establish new treatment guidelines for these patients.

CRTC1/MAML2 fusion transcript in high grade mucoepidermoid carcinomas of salivary and thyroid glands and Warthin's tumors: implications for histogenesis and biologic behavior

We analyzed 55 primary salivary gland tumors including 22 mucoepidermoid carcinomas (MECs) to determine the association of MECT1/TORC1/CRTC1-MAML2 fusion transcript to tumor types, level of MEC differentiation and clinicopathologic parameters. Our primary salivary gland tumors were composed of 22 MECs, 11 Warthin's tumors, 10 adenoid cystic carcinomas, two basaloid carcinomas, five salivary duct carcinomas, and five adenocarcinomas, not otherwise specified. We also included, for the first time, three primary MECs of the thyroid gland. We used nested RT-PCR and subsequent sequencing techniques for detection and verification of the fusion transcript in fresh and archival specimens. Eighteen (81%) of the 22 primary salivary and one of the three thyroid glands with MEC were positive for the fusion transcript. The transcript was detected equally in low, intermediate and high grade as well as low and high stage MECs. Significant correlation between fusion negative tumors and distant metastasis was noted (P = 0.005). Four (36%) of the 11 Warthin's tumors were also positive for the transcript. None of the 22 primary non-MEC gland salivary carcinomas were positive for the transcript. We conclude that the CRTC1/MAML2 transcript may be detected in both low and high grade MEC, that fusion negative tumors may define a subset of biologically aggressive MEC's tumors, that the fusion is present in primary MECs of the thyroid gland and is also detectable in Warthin's tumor, and that a subset of MECs can be targeted for therapeutic intervention.

Overexpression of cyclooxygenase-2 correlates with cytoplasmic HuR expression in salivary mucoepidermoid carcinoma but not in pleomorphic adenoma

BACKGROUND

The overexpression of cyclooxygenase (COX)-2 in several human carcinomas suggests that COX-2 is related to carcinogenesis. Although COX-2 expression has been shown to be up-regulated in carcinomas of the salivary gland, its mechanisms are not completely understood. HuR is an mRNA-binding protein that controls the stability of certain transcripts including COX-2.

METHODS

The expression of COX-2 and HuR was determined by immunohistochemistry in 28 cases of salivary pleomorphic adenoma and 18 cases of salivary mucoepidermoid carcinoma.

RESULTS

28.6% and 72.2% of the pleomorphic adenomas and mucoepidermoid carcinomas showed high COX-2 expression respectively. 35.7% of pleomorphic adenomas and 72.2% of mucoepidermoid carcinomas were tested positive for HuR in the cytoplasm of tumor cells. There was a correlation between a high COX-2 immunoreactivity and cytoplasmic HuR expression in mucoepidermoid carcinomas but not in pleomorphic adenomas.

CONCLUSION

This study suggests that cytoplasmic HuR is correlated with COX-2 expression in salivary mucoepidermoid carcinomas. In addition, the immunoreactivity of COX-2 and cytoplasmic HuR might be used to evaluate the nature of a borderline malignancy in the salivary glands.

Implications of methylation patterns of cancer genes in salivary gland tumors

PURPOSE

We investigated the methylation status and protein expression of four tumor suppressor genes to determine their role in salivary gland tumorigenesis.

EXPERIMENTAL DESIGN

We performed methylation-specific PCR and protein analyses of 29 normal salivary glands, 23 benign, and 79 malignant salivary gland neoplasms to determine the pattern and potential diagnostic and/or biological role of the RASSF1, RARbeta2, DAPK, and MGMT tumor suppressor gene methylation in these tumors.

RESULTS

No methylation was detected in the normal tissues. Methylation occurred in 9 of 23 (39.1%) benign tumors; 3 (25.0%) pleomorphic adenomas and 6 (66.7%) Warthin's tumors at the MGMT, DAPK, or RASSF1 genes. Methylation occurred in 33 of 79 (41.8%) malignant tumors; 8 (30.8%) adenoid cystic carcinomas, 6 (33.3%) mucoepidermoid carcinomas, 6 (42.9%) acinic cell carcinomas, and 13 (62.0%) salivary duct carcinomas. RASSF1 and RARbeta2 represented 75.8% of methylation events occurring most frequently in salivary duct and acinic cell carcinomas. Overall, we found no significant correlation between protein expression and methylation status of individual genes, but observed low or absent protein expression in several methylated tumors. Significant correlations were found between methylation and aggressive malignant phenotypes (P = 0.0004) and age (P = 0.05).

CONCLUSIONS

(a) Benign and malignant salivary tumors differed in the frequency and pattern of gene methylation; (b) high-grade carcinomas were significantly methylated compared with low-grade phenotypes; (c) RASSF1 and RARbeta2 were highly methylated in malignant tumors and can be targeted for therapy; and (d) methylation pattern may serve as a diagnostic and biological marker in assessing these tumors.

TUNEL - an efficient prognosis predictor of salivary malignancies

Biological markers are necessary for predicting prognosis of salivary malignancies and better understanding the pathogenesis of salivary cancer. We analysed terminal deoxynucleotidyl transferase (TdT)-mediated biotinylated deoxyuridine-triphosphate (dUTP)-biotin nick-end labelling (TUNEL), p53 and Ki67 expression in 66 patients with malignant salivary tumours by immonohistochemistry, and correlated the data with survival, disease-free survival, tumour grade, stage, and local and distant metastasis. TUNEL efficiently predicted poor prognosis in salivary malignancies. The 5-year (5Y) survival probability dropped significantly with the level of TUNEL staining (from 83% in negatively stained tumours to 57 and 24% in TUNEL positively stained levels 1 and 2, respectively), (P=0.042). Extensive Ki67 staining (in addition to TUNEL) reduced the 5Y-survival rate even further and addition of positively stained p53 dropped the 5Y-survival rate to 0. The correlation rates between TUNEL and Ki67 was 58% (P=0.0001), and between TUNEL and p53 it was 50% (P=0.035). Concurrently, TUNEL correlated with metastasis, extracapsular spread, grade and stage. The correlation between TUNEL, p53 and Ki67 staining and survival probabilities, and the pathological grade, stage and metastasis spread of salivary malignancies makes this a highly effective tool in patient follow-up and prognosis.

Overexpression of cyclin D1 and cortactin is primarily independent of gene amplification in salivary gland adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) of the salivary glands exhibits persistent growth, invasion and metastasis. Chromosome 11q13 amplification is a frequent event associated with tumor progression in a number of carcinomas and is associated with poor prognosis. Two genes within the 11q13 amplicon that are overexpressed as a result of 11q13 amplification are the cell cycle regulatory protein cyclin D1 (CCND1) and cortactin (CTTN), a protein involved cell motility and invasion. To determine the expression and gene status of cyclin D1 and cortactin in ACC, we evaluated 39 ACC cases by immunohistochemistry (IHC) for cyclin D1 and cortactin expression. Amplification of CCND1 and CTTN was determined by fluorescent in situ hybridization (FISH). Cyclin D1 overexpression was present in 90% (35/39) and cortactin expression in 62% (24/39) of evaluated cases, although CCND1 and CTTN levels were elevated in only two cases (5%) as determined by FISH. Our results indicate that chromosome 11q13 amplification is uncommon in ACC, but that cyclin D1 and cortactin are frequently overexpressed and may therefore contribute to the growth and invasive potential of ACC.

Systemic therapy in the palliative management of advanced salivary gland cancers

Cancers of the salivary glands are unusual lesions that vary widely in their histologic appearance and molecular characteristics. Likewise, there is a wide spectrum of biologic behavior, ranging from low-grade, minimally invasive tumors, to highly lethal malignancies. There are few data on the role of systemic therapies in the management of these cancers, and chemotherapy is generally reserved for the palliative management of advanced disease that is not amenable to local therapies such as surgery and/or radiation. The majority of patients for whom systemic therapy is considered will have either adenoid cystic carcinoma, mucoepidermoid carcinoma, or high-grade adenocarcinoma. This article will review the available literature regarding the use of palliative chemotherapy for patients with advanced salivary gland cancer of these histologies, with an emphasis on the potential role of targeted agents. There is a need for a determined, coordinated effort to conduct high-quality clinical trials in patients with these rare cancers.

Biological behavior of myoepithelial cells in the regeneration of rat atrophied sublingual glands following release from duct ligation

The present study aimed to clarify how myoepithelial cells behave during regeneration of an atrophied sublingual gland by investigating cell proliferation and ultrastructure. Atrophy of rat sublingual glands was induced by unilateral ligation of the excretory duct near the hilum with metal clips, which were then removed after one week of ligation for regeneration. The sublingual glands 0-14 days after unligation were examined with single immunohistochemistry for actin as a marker of myoepithelial cells, double immunohistochemistry for actin and proliferating cell nuclear antigen (PCNA) as a marker of proliferating cells, and transmission electron microscopy (TEM). The single immunohistochemistry and TEM showed that myoepithelial cells surrounded residual ducts in the atrophied glands and immature and mature acini in the regenerating glands. Although PCNA-positive myoepithelial cells were identified during regeneration, PCNA labeling indices of myoepithelial cells were low at all time points except at day 7. Ultrastructurally, myoepithelial cells showing bizarre shaped structures in the atrophy changed with maturation of differentiating acinar cells and appeared normal in the regenerated glands. There was no differentiation of the remaining duct cells to myoepithelial cells. These observations suggest that proliferation of myoepithelial cells and differentiation to myoepithelial cells do not commonly participate in the regeneration of atrophied sublingual glands and that the bizarre shaped myoepithelial cells in the atrophied sublingual glands recover the original shapes with acinar cell regeneration.

Differential expression of p63 isotypes (DeltaN and TA) in salivary gland neoplasms: biological and diagnostic implications

To determine the association between the expression of p63 gene isoforms (TA and DeltaN) and salivary gland tumorigenesis, we performed reverse transcription-polymerase chain reaction analysis of these markers in 71 benign and malignant salivary gland neoplasms. The results were correlated with the expression of Notch ligand JAG1 gene and the clinicopathologic features and the full-length p63 protein expression by immunohistochemistry. Both p63 isoforms were either negative or weakly expressed in normal salivary gland tissues. TAp63 was highly expressed in most benign tumors and was either negative or weakly positive in most carcinomas. Conversely, DeltaNp63 was negative or faintly positive in most benign neoplasms and was highly expressed in adenoid cystic, mucoepidermoid, and myoepithelial carcinomas. Immunohistochemical analysis using anti-full-length p63 protein showed ubiquitous nuclear staining in basal and myoepithelial cells in both benign and malignant neoplasms. JAG1 was expressed in most benign and malignant tumors and did not correlate with p63 isoforms expression. We conclude that (1) p63 isoforms are differentially expressed in most benign and malignant tumors and may play distinct biological roles in certain salivary gland neoplasms; (2) p63 immunostaining do not correlate with the isoforms expression; and (3) isoform-specific antibodies are required for better cellular localization and biological correlations.

PLAG1 gene alterations in salivary gland pleomorphic adenoma and carcinoma ex-pleomorphic adenoma: a combined study using chromosome banding, in situ hybridization and immunocytochemistry

Pleomorphic adenoma is the most common benign tumor of the salivary glands. It has marked histological diversity with epithelial, myoepithelial and mesenchymal-type cells arranged in a variety of architectural and differentiation patterns. Pleomorphic adenoma gene 1 (PLAG1), shown to be consistently rearranged in pleomorphic adenomas, is activated by chromosomal translocations involving 8q12, the chromosome region that is most frequently affected in these tumors. In this study, we evaluated PLAG1 involvement in salivary gland tumorigenesis by determining the frequency of its alterations in a selected group of 20 salivary gland tumors: 16 pleomorphic adenomas and four carcinomas ex-pleomorphic adenoma, having in common the presence of karyotypic chromosome 8 deviations, either structural, with 8q12 rearrangements, or numerical, with gain of chromosome 8. PLAG1 status was analyzed using in situ hybridization techniques, on metaphase cells, by fluorescence detection and/or interphase cells in paraffin sections, by chromogenic detection. Except for one pleomorphic adenoma case (5%) that lacked PLAG1 involvement, 17 tumors (85%), (14 pleomorphic adenomas and three carcinomas ex-pleomorphic adenoma) showed intragenic rearrangements of PLAG1 and the remaining two cases (10%), (one pleomorphic adenoma and one carcinoma ex-pleomorphic adenoma), had chromosome trisomy 8 only. To further investigate the role of PLAG1 on pleomorphic adenomas tumorigenesis, as well as the putative morphogenesis mechanism, we attempted to identify the cell types (epithelial vs myoepithelial) carrying 8q12/PLAG1 abnormalities by a combined phenotypic/genotypic analysis in four cases (three pleomorphic adenoma and one carcinoma ex-pleomorphic adenoma) characterized by 8q12 translocations and PLAG1 rearrangement. In these cases, both cells populations carried PLAG1 rearrangements. This finding further supports the pluripotent single-cell theory, which postulates that the tumor-initiated, modified myoepithelial cell, evolves into the varied somatic cell phenotypes present in pleomorphic adenoma, and reinforces the role of PLAG1 on the tumorigenesis of benign and malignant pleomorphic adenoma.

HER2 Expression in Salivary Gland Carcinomas

PURPOSE

Previous evaluation of HER2 overexpression in salivary gland cancers indicated an incidence varying between 7 and 56%, with no clear difference among three histologically different subtypes. As part of a Phase II trial of trastuzumab for treatment of incurable salivary gland cancer, we screened 137 tumors for HER2 expression.

EXPERIMENTAL DESIGN

Unstained sections of paraffin-embedded tumor samples were stained with p185/HER2 receptor antibody. Tumors with moderate (2+) to strong (3+) complete membrane staining in at least 10% of the tumor cells were scored as positive for overexpression.

RESULTS

The overall frequency of overexpression for HER2 was 17% (23 of 137), whereas it was only 8% in the three most common histological subtypes screened. Overexpression was distinctly rare in the most common subtype screened, adenoid cystic carcinoma (4%, 3 of 70). Overexpression was very common in salivary duct cancers; 10 (83%) of 12 were positive for HER2. This observation is consistent with the typical high-grade histological features and aggressive behavior of this subtype as well as with its histogenetic similarity to breast cancer. Analysis based on histogenesis (intercalated duct versus excretory duct) indicated a higher frequency of overexpression in the latter (55%) than in the former (7%).

CONCLUSIONS

Our overall results suggest that trastuzumab will not have a major role in treatment of salivary gland cancers of intercalated duct origin. Further systematic evaluation of trastuzumab in subtypes of excretory duct origin could be supported.

Regeneration in chronic sialadenitis: an analysis of proliferation and apoptosis based on double immunohistochemical labelling

The understanding of regeneration in salivary glands as a finely tuned balance of cellular proliferation, differentiation and apoptosis has been limited by the difficulty of identifying proliferating cells. This has been overcome in the present investigation by double immunohistochemical labelling for the proliferation-associated antigen Ki67 and for different cell-type-specific antigens applied to 8 specimens of normal parotids and 16 specimens of chronic parotid sialadenitis with particular reference to acini and intercalated ducts. In comparison with low baseline rates of proliferation in normal parotids, proliferative indices were significantly increased in chronic sialadenitis in mature acinar cells, intercalated ductal cells and myoepithelial cells without evidence of proliferation by an additional population of cells. In accordance with findings in glands of experimental animals, the present data do not support the previously postulated concept of regeneration of acini and intercalated ducts by a hypothetical population of uncommitted ductal stem cells. The demonstration of a profound capacity for intrinsic glandular regeneration from differentiated cells represents a biological basis for the good results obtained from conservative therapy of chronic sialadenitis and offers hope for novel therapies designed to reconstitute impaired salivary flow.

A prospective study of salivary gland function in patients undergoing radiotherapy for squamous cell carcinoma of the oropharynx

OBJECTIVE

We sought to investigate the impact of head and neck cancer treatment on salivary function.

STUDY DESIGN

The study was conducted on 54 patients with advanced squamous cell carcinoma with confirmed (n = 50) or suspected (n = 4) primary oropharyngeal localization who were treated with radiation alone or in combination with surgery or chemotherapy, or both. The following groups were considered in the evaluation: 1, the entire pool of patients; 2, those undergoing surgery and those not undergoing surgery before radiation; 3, those undergoing resection and those not undergoing resection of the submandibular gland. The flow rates, pH, and buffering capacity were determined before, during, and up to 12 months after the completion of radiation.

RESULTS

Head and neck surgery, particularly when submandibular gland resection was performed, had a negative impact on salivary flow rates but did not influence pH or buffering capacity. Nonetheless, the effect of surgery on salivary flow rates decreased progressively and disappeared at 3 to 6 months after radiotherapy. More than two thirds of the salivary output was lost during radiation treatment. All patients were experiencing salivary dysfunction at 1 year after completion of radiotherapy, with average decreases of 93% (P < .0001) and 95% (P < .0001) for whole resting salivary flow and whole stimulated salivary flow, respectively, compared with the preradiotherapy values. The buffering capacity decreased to 67% of its preradiotherapy value, and whole stimulated saliva became acidic.

CONCLUSIONS

The result of this study confirms that cancer treatment involving full-dose radiotherapy (RTH) to all major salivary glands for locally advanced squamous cell carcinoma of the oropharynx induces severe hyposalivation with alteration of salivary pH and buffering capacity. Head and neck surgery has a negative impact on salivary flow rates, especially when the submandibular gland is removed. However, surgery before irradiation is not a factor aggravating hyposalivation when postoperative radiotherapy includes all the major salivary glands.

Immunocytochemistry of myoepithelial cells in the salivary glands

MECs are distributed on the basal aspect of the intercalated duct and acinus of human and rat salivary glands. However, they do not occur in the acinus of rat parotid glands, and sometimes occur in the striated duct of human salivary glands. MECs, as the name implies, have structural features of both epithelial and smooth muscle cells. They contract by autonomic nervous stimulation, and are thought to assist the secretion by compressing and/or reinforcing the underlying parenchyma. MECs can be best observed by immunocytochemistry. There are three types of immunocytochemical markers of MECs in salivary glands. The first type includes smooth muscle protein markers such as alpha-SMA, SMMHC, h-caldesmon and basic calponin, and these are expressed by MECs and the mesenchymal vasculature. The second type is expressed by MECs and the duct cells and includes keratins 14, 5 and 17, alpha 1 beta 1 integrin, and metallothionein. Vimentin is the third type and, in addition to MECs, is expressed by the mesenchymal cells and some duct cells. The same three types of markers are used for studying the developing gland. Development of MECs starts after the establishment of an extensively branched system of cellular cords each of which terminates as a spherical cell mass, a terminal bud. The pluripotent stem cell generates the acinar progenitor in the terminal bud and the ductal progenitor in the cellular cord. The acinar progenitor differentiates into MECs, acinar cells and intercalated duct cells, whereas the ductal progenitor differentiates into the striated and excretory duct cells. Both in the terminal bud and in the cellular cord, the immediate precursors of all types of the epithelial cells appear to express vimentin. The first identifiable MECs are seen at the periphery of the terminal bud or the immature acinus (the direct progeny of the terminal bud) as somewhat flattened cells with a single cilium projecting toward them. They express vimentin and later alpha-SMA and basic calponin. At the next developmental stage, MECs acquire cytoplasmic microfilaments and plasmalemmal caveolae but not as much as in the mature cell. They express SMMHC and, inconsistently, K14. This protein is consistently expressed in the mature cell. K14 is expressed by duct cells, and vimentin is expressed by both mesenchymal and epithelial cells. After development, the acinar progenitor and the ductal progenitor appear to reside in the acinus/intercalated duct and the larger ducts, respectively, and to contribute to the tissue homeostasis. Under unusual conditions such as massive parenchymal destruction, the acinar progenitor contributes to the maintenance of the larger ducts that result in the occurrence of striated ducts with MECs. The acinar progenitor is the origin of salivary gland tumors containing MECs. MECs in salivary gland tumors are best identified by immunocytochemistry for alpha-SMA. There are significant numbers of cells related to luminal tumor cells in the non-luminal tumor cells that have been believed to be neoplastic MECs.

Salivary gland hyperplasia

Thirteen cases of adenomatous ductal hyperplasia (ADH) of the major salivary glands coexisting with salivary gland tumors or chronic parotitis are reported. The proliferating ducts have the morphology and immunohistochemistry similar to intercalated duct epithelium. Adenomatous ductal hyperplasia is compared to adenomatoid acinar hyperplasia (AAH), a lesion found predominantly in intraoral salivary glands and histologically composed of hyperplastic acinar cells. The exact nature of both lesions is not clear. However, ADH may be a precursor lesion of salivary gland tumors (especially epithelial-myoepithelial carcinomas), whereas AAH may represent a reactive process of idiopathic nature.

Apoptosis and proliferation of myoepithelial cells in atrophic rat submandibular glands

This study was designed to determine whether apoptosis and proliferation of myoepithelial cells occur in atrophic rat submandibular glands. The excretory duct of the right submandibular gland was doubly ligated with metal clips. The atrophic right submandibular glands removed after 1-28 days of duct ligation were investigated using immunohistochemical double staining for actin as a marker for myoepithelial cells and proliferating cell nuclear antigen (PCNA) as a marker for proliferating cells, double staining for actin immunohistochemistry, nick end-labeling (TUNEL) as a marker for apoptotic cells, and transmission electron microscopy (TEM). A few PCNA- and no TUNEL-positive myoepithelial cells were found in the control submandibular glands taken from animals with no operation. In the experimental glands, PCNA-positive myoepithelial cells were common 2 and 3 days after duct ligation and then decreased in number. TUNEL-positive myoepithelial cells appeared at 2 days and were observed most frequently at 5 days. Apoptotic myoepithelial cells were also identified by TEM. These observations suggest that both apoptosis and proliferation of myoepithelial cells occur, especially in the early phase of atrophy, in the rat submandibular gland.