Malignant salivary gland tumors and cyclo-oxygenase-2: A histopathological and immunohistochemical analysis with implications on histogenesis

The current markers of cancer stem cell in oral cancers

Head and neck cancer (HNC) constitute 5% of all reported cancers. Among all, the oral cavity cancer is the most frequent type of HNC which accounts for over half of HNC cases. Mouth cancer ranks the sixth leading cause of cancer-related mortality. Generally, conventional chemotherapy has shown success at decreasing relapse and metastasis rates and improves the overall prognosis. Recently, target therapy and targeted drug delivery systems have been introduced as promising treatments. The elimination of efficiency of current therapeutic strategies due to the spared cancer stem cells that cause chemotherapy resistance, relapse and metastasis. Inefficiency methodologies in the elimination of all cancer cells in the body are a major problem that remained to be resolved before to confront the new cancer therapies. Many studies imply to cancer stem cell markers as important agents for targeted anti-cancer as well as improving chemotherapy efficiencies. The potentials of targeted cancer therapy led us to search for novel markers in the mouth cancer stem cells especially in rare cancers. The aimed of this research was, first a comprehensive critical review of the previous studies on the markers of cancer stem cells in oral cancers including oral squamous cell carcinoma, salivary gland cancers, and to highlight the most common cancer stem cell markers which have potential to be exploited as indicators for the preneoplastic lesion malignancy, oral cancer progression, and/or treatment prognosis.

Differential expression of cyclooxygenase-2 and cyclin D1 in salivary gland tumors

PURPOSE

Salivary gland tumors are complex and have a great histomorphological diversity; more than 30 histological subtypes are currently described and the study of proteins that help understand and differentiate these tumors is essential. We aimed to analyze the immunoexpression of cyclooxygenase-2 (COX-2) and cyclin D1 proteins in pleomorphic adenomas (PA), mucoepidermoid carcinomas (MEC) and adenoid cystic carcinomas (AdCC) of salivary glands.

METHODS

A total of 38 PA, 12 AdCC and 12 MEC underwent immunohistochemical study by the polymeric biotin-free technique. Immunopositive cells were analyzed semi-quantitatively. For statistical analysis, a significance level was set at p ≤ 0.05.

RESULTS

Overall, these tumors were more prevalent in women (n = 37). The mean age of these patients was 58-year-old and the parotid gland was the most affected anatomic site (n = 33). All cases of AdCC and MEC showed immunopositivity to cyclin D1; however, 39.5% of the PAs were negative (p < 0.001). Regarding COX-2 immunoexpression, we observed that all cases of CME were positive, whereas 60.5% of the PA and 75% of the CAC analyzed were completely negative (p = 0.042).

CONCLUSIONS

The overexpression of COX-2, observed only in MEC, emphasizes that salivary gland tumors have different profiles. Cyclin D1 is more immunoexpressed in malignant tumors. Together, these immunohistochemical findings may be useful in differentiating the studied tumors.

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.

Expression and localization of osteopontin, homing cell adhesion molecule/CD44, and integrin αvβ3 in mucoepidermoid carcinoma and acinic cell adenocarcinoma of salivary gland origin

OBJECTIVE

Osteopontin (OPN) plays a role in tumor progression. This study aimed to determine the expression of OPN, CD44, and integrin αvβ3 in pleomorphic adenoma (PA), acinic cell adenocarcinoma (ACA), and mucoepidermoid carcinoma (MEC).

STUDY DESIGN

Immunohistochemistry was used to semiquantify the levels of expression of OPN and its receptors in normal salivary glands (NSG) (n = 20), PA (n = 20), ACA (n = 11), and MEC (n = 29).

RESULTS

OPN expression was increased in ACA and MEC compared with PA and NSG (median scores, 6, 6, 4, and 4, respectively). CD44 expression was increased in ACA and reduced in MEC and PA compared with NSG (median scores, 8, 4, 3, and 5, respectively). Integrin αvβ3 median scores were 5 in ACA, 1 in MEC, and 0 in PA and NSG.

CONCLUSIONS

OPN is expressed in salivary gland tumors and is at higher levels in ACA and MEC.

New diagnostic markers in salivary gland tumors

Parotid gland tumors are a rare and heterogeneous entity. Molecular markers are sparse. The aim of the study was to identify new diagnostic markers in benign and malignant salivary tumors. A tissue microarray was constructed with 158 tumor samples. Expression of 21 tumor antigens involved in tumor cell survival and known for prognostic potential was assessed immunohistochemically in all parotid gland samples. CEA, Cox-1, Cox-2, Sigma, beta-Catenin, WISP-1 and PDGF-beta were differently regulated in benign and malignant parotid tumors. Subsequently, these seven proteins entered the step-wise logistic regression analysis. As a second step, we defined a score for differentiating benign versus malignant parotid lesions: 4*CEA+15*Cox-1+4*Cox-2+4*Sigma+3*PDGF-beta+10*beta-Catenin+14*Wisp1. Sensitivity and specificity of 94 and 83% were reached. Besides routine hematoxylin and eosin staining, definition of new diagnostic markers and subsequently a new diagnostic score are an attempt to create an additional tool for the diagnosis of parotid gland tumors.

Salivary gland cancer stem cells

Emerging evidence suggests the existence of a tumorigenic population of cancer cells that demonstrate stem cell-like properties such as self-renewal and multipotency. These cells, termed cancer stem cells (CSC), are able to both initiate and maintain tumor formation and progression. Studies have shown that CSC are resistant to traditional chemotherapy treatments preventing complete eradication of the tumor cell population. Following treatment, CSC are able to re-initiate tumor growth leading to patient relapse. Salivary gland cancers are relatively rare but constitute a highly significant public health issue due to the lack of effective treatments. In particular, patients with mucoepidermoid carcinoma or adenoid cystic carcinoma, the two most common salivary malignancies, have low long-term survival rates due to the lack of response to current therapies. Considering the role of CSC in resistance to therapy in other tumor types, it is possible that this unique sub-population of cells is involved in resistance of salivary gland tumors to treatment. Characterization of CSC can lead to better understanding of the pathobiology of salivary gland malignancies as well as to the development of more effective therapies. Here, we make a brief overview of the state-of-the-science in salivary gland cancer, and discuss possible implications of the cancer stem cell hypothesis to the treatment of salivary gland malignancies.

Expression of gelatinases (MMP-2, MMP-9) and cyclooxygenases (COX-1, COX-2) in some benign salivary gland tumors

Salivary gland tumors, most of which are rare benign tumors, represent a histologically heterogenous group with the greatest diversity of morphological and cellular features. The aim of this study is to analyse the expression and possible interactions between gelatinases (MMP-2, MMP-9) and cyclooxygenases (COX-1, COX-2) in some benign salivary gland tumors. We investigated the expression of gelatinases and cyclooxigenases in control salivary gland, Pleomorphic adenoma and Warthin's tumor through immunohistochemistry and Reverse Transcription - Polymerase Chain Reaction (PCR). We identified the expression of both classes of enzyme in normal samples and in the two types of pathological samples without any quantitative differences. From the present data no significant differences emerge in the expression of these enzymes among the different pathologies examined. Nevertheless, due to the small number of samples included in this study, general statements regarding correlation between the degree of severity of the tumoral pathology and the quantitative expression of these potential tumoral markers can not be made.

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.

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."

Clinical significance of Myb protein and downstream target genes in salivary adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC), the second most frequent malignancy of the major and minor salivary glands, comprise of approximately 15-23% of all carcinomas at these locations. ACC is uniquely formed of dual epithelial and myoepithelial cells that give rise to different phenotypic patterns. We hypothesize that the dual myoepithelial/ epithelial composition of ACCs underlie their biological heterogeneity and may impact on their therapeutic management. A recurrent reciprocal translocation of t(6;9)(q22-23; p23-24) resulting in fusion gene partners comprising MYB gene the transcription factor NFIB has been reported in ACC of breast, salivary, lachrymal and ceruminal glands. In fusion positive and a subset of fusion negative ACCs, high expression of the transcript Myb was found. However, the role of Myb protein expression and the potential effect on the downstream targets have not been investigated. To investigate the biological and prognostic significance of use of elevated levels of Myb and its downstream target genes (c-kit, cox-2, bcl-2), we analyzed, by immunohistochemistry, the protein expression of these genes in 156 ACCs. We have found that 55% of ACCs have increased Myb expression mainly confined to myoepithelial cells. We validated Myb expression on a large cohort of ACCs (156 patients). Although no significant effects of the individual Myb and downstream targets c-kit, bcl-2 and cox-2 on survival was noticed, the combinations survival curve for Myb+/c-kit+/cox-2+ showed better survival than combination Myb-/c-kit+/cox-2+. Myb may serve as a new target for the management of this disease, and future therapeutic trials of these tumors may be better based on biomarker stratification and the cellular composition of these tumors.

Progressive genetic alterations of adenoid cystic carcinoma with high-grade transformation

CONTEXT

Although genome-wide imbalances have been characterized in conventional adenoid cystic carcinoma, other than p53 mutational status, the molecular profile of adenoid cystic carcinoma with high-grade transformation has not been explored.

OBJECTIVE

To evaluate progressive genetic alterations in adenoid cystic carcinoma with high-grade transformation using array comparative genomic hybridization.

DESIGN

Five adenoid cystic carcinomas with high-grade transformation (4 primary tumors and 1 paired metastasis) were selected and characterized at the DNA level by array comparative genomic hybridization on formalin-fixed paraffin-embedded tissue. Select alterations were validated by fluorescence in situ hybridization.

RESULTS

Chromosomal gains were mostly confined to the areas of high-grade transformation while losses were seen only in the conventional areas. Chromosomal regions with significant gains included 8q24, 17q11.2-q12, 17q23, and 15q11-13. Regions that showed the significant losses included 9q34, 4p16, 1p36.1, and 11q22. Fluorescence in situ hybridization analysis demonstrated increases in C-MYC (8q24.12-q24.13) and a low level increases in ERBB2 ( formerly HER2/neu ) (17q11.2-q12) in cases showing gains by array comparative genomic hybridization in these regions. However, no tumor showed HER2/ neu immunopositivity.

CONCLUSIONS

High-grade transformation in adenoid cystic carcinoma is a complex process that is reflected by several chromosomal alterations. Our findings implicate C-MYC amplification in this progression, although the role of HER2/neu is still unclear. Other candidate oncogenes, particularly on chromosome 17q23, warrant investigation in this rare tumor.