Reduced expression of p27Kip1 protein in relation to salivary adenoid cystic carcinoma metastasis

The Epigenesis of Salivary Glands Carcinoma: From Field Cancerization to Carcinogenesis

Salivary gland carcinomas (SGCs) are a diverse collection of malignant tumors with marked differences in biological activity, clinical presentation and microscopic appearance. Although the etiology is varied, secondary radiation, oncogenic viruses as well as chromosomal rearrangements have all been linked to the formation of SGCs. Epigenetic modifications may also contribute to the genesis and progression of SGCs. Epigenetic modifications are any heritable changes in gene expression that are not caused by changes in DNA sequence. It is now widely accepted that epigenetics plays an important role in SGCs development. A basic epigenetic process that has been linked to a variety of pathological as well as physiological conditions including cancer formation, is DNA methylation. Transcriptional repression is caused by CpG islands hypermethylation at gene promoters, whereas hypomethylation causes overexpression of a gene. Epigenetic changes in SGCs have been identified, and they have been linked to the genesis, progression as well as prognosis of these neoplasms. Thus, we conduct a thorough evaluation of the currently known evidence on the involvement of epigenetic processes in SGCs.

EZH2 is a sensitive marker of malignancy in salivary gland tumors

BACKGROUND

The immunohistochemical detection of Enhancer of zeste homologue 2 (EZH2) proved to be a useful tool to recognize the malignant nature of tumors in a wide variety of neoplasms. The histological diagnostics of salivary gland tumors is a challenging task, and a reliable marker of malignancy would be extremely helpful.

METHODS

EZH2 expression was investigated in 54 malignant and 40 benign salivary gland tumors of various histological types by standard immunohistochemistry.

RESULTS

The majority (n = 52) of the malignant tumors stained positively, while all the investigated benign tumors were negative for EZH2.

CONCLUSIONS

EZH2 expression in salivary gland tumors, similarly to the tumors of other organs is not characteristic for any tumor type, but is a solid marker of the malignant nature of the tumors.

Expression of p27Kip1 and E-cadherin in Head and Neck Squamous Cell Carcinoma of Indonesian Patients

Cancer cells exhibit characteristic damage of DNA and its expression. The expression of the tumor suppressors E-cadherin and p27^Kip1 has been tested on 57 head and neck squamous cell carcinomas (HNSCC) of Indonesian subjects. HNSCC tumor samples including both primary and (unrelated) nodal cases were obtained from the archives of Indonesian hospitals, in accordance with acknowledged ethical requirements. Only modest correlation was found between reduced expression of E-cadherin or p27^Kip1 with increased malignancy of primary and nodal growth. The observed strong correlation regardless of malignancy between the expressed levels of E-cadherin and p27^Kip1 suggests that also in combination these would not help to better predict the outcome of HNSCC.

Takahashi R, Nagai T, Yoshida M, Suzuki F, Obikane H, Yamashina M, Matsubayashi J. Immunohistochemical analysis of salivary gland tumors: application for surgical pathology practice

Salivary gland tumors are relatively uncommon and there exists a considerable diagnostic difficulty owing to their diverse histological features in individual lesions and the presence of a number of types and variants, in addition to overlapping histological patterns similar to those observed in different tumor entities. The classification is complex, but is closely relevant to the prognostic and therapeutic aspects. Although hematoxylin-eosin staining is still the gold standard method used for the diagnosis, immunohistochemistry (IHC) can enhance the accuracy and be a helpful tool when in cases to investigate the subjects that cannot be assessed by histological examination, such as the cell nature and differentiation status, cell proliferation, and tumor protein expression. This review depicts on the practical diagnostic utility of IHC in salivary gland tumor pathology under the following issues: assessment of cell differentiation, focusing on neoplastic myoepithelial cells; discrimination of histologically mimic tumor groups; diagnosis of specific tumor types, e.g., pleomorphic adenoma, adenoid cystic carcinoma, and salivary duct carcinoma; and evaluation of malignancy and prognostic factors. IHC plays a limited, even though important, role in the diagnosis of salivary gland tumors, but is often useful to support the histological assessment. However, unfortunately few tumor type-specific markers are still currently available. For these reasons, IHC should be considered a method that can be used to assist the final diagnosis, and its results themselves do not directly indicate a definitive diagnosis.

TGF-β1 Promotes Migration and Invasion of Salivary Adenoid Cystic Carcinoma

Salivary adenoid cystic carcinoma (SACC) is one of the most common subtypes of salivary gland carcinomas and frequently metastasizes to distant organs. However, little is known about the molecular mechanisms that promote SACC metastasis. In this study, we report that transforming growth factor (TGF)-β1 was highly expressed in the highly metastatic SACC-LM cell line as compared with its parental low-metastatic SACC-83 cell line. Exogenous addition of TGF-β1 induced Smad2 phosphorylation and promoted the migration and invasion of SACC-83 cells. Consistently, the inhibition of endogenous TGF-β1 signaling in SACC-LM cells by an inhibitor specific to the type I TGF-β1 receptor (TβRI) suppressed cell migration and invasion. Moreover, we found that TGF-β1 expression was significantly increased in human primary SACC samples with metastasis. Taken together, our results suggest that TGF-β1 may play a crucial role in SACC metastasis.

Downregulation of runt-related transcription factor 3 associated with poor prognosis of adenoid cystic and mucoepidermoid carcinomas of the salivary gland

Runt-related transcription factor 3 (RUNX3) is a transcription factor of the transforming growth factor (TGF)-β superfamily and acts as a tumor suppressor gene, which is silenced by hypermethylation of the promoter region in various cancers. In this study, we examined the expression and methylation status of RUNX3 in the salivary gland cancers pleomorphic adenoma (PA), adenoid cystic carcinoma (ACC) and mucoepidermoid carcinoma (MEC). The cytoplasmic expression rates of RUNX3 in PA, ACC and MEC were 65% (13/20), 22.2% (8/36) and 20.6% (7/34), respectively. Low expression or deletion of RUNX3 in ACC and MEC was significantly associated with tumor progression and poor prognosis. Using microdissected cDNA, we found that RUNX3 mRNA expression was lower in ACC and MEC than in PA and noncancerous salivary glands; furthermore, hypermethylation of RUNX3 was detected more frequently in PA (2/8, 25%), ACC (6/8, 75%) and MEC (7/8, 87.5%) than in noncancerous salivary glands (0/8, 0%). Our results suggest that low expression or deletion of RUNX3 in salivary gland tumors might play a pivotal role in tumorigenesis and tumor progression and poor prognosis in the case of salivary gland ACC and MEC. Recovery of the tumor suppressive function of RUNX3 might inhibit tumorigenesis and cancer progression in the human salivary gland.

Mitochondrial mutations in adenoid cystic carcinoma of the salivary glands

Background

The MitoChip v2.0 resequencing array is an array-based technique allowing for accurate and complete sequencing of the mitochondrial genome. No studies have investigated mitochondrial mutation in salivary gland adenoid cystic carcinomas.

Methodology

The entire mitochondrial genome of 22 salivary gland adenoid cystic carcinomas (ACC) of salivary glands and matched leukocyte DNA was sequenced to determine the frequency and distribution of mitochondrial mutations in ACC tumors.

Principal Findings

Seventeen of 22 ACCs (77%) carried mitochondrial mutations, ranging in number from 1 to 37 mutations. A disproportionate number of mutations occurred in the D-loop. Twelve of 17 tumors (70.6%) carried mutations resulting in amino acid changes of translated proteins. Nine of 17 tumors (52.9%) with a mutation carried an amino acid changing mutation in the nicotinamide adenine dinucleotide dehydrogenase (NADH) complex.

Conclusions/Significance

Mitochondrial mutation is frequent in salivary ACCs. The high incidence of amino acid changing mutations implicates alterations in aerobic respiration in ACC carcinogenesis. D-loop mutations are of unclear significance, but may be associated with alterations in transcription or replication.

Reg IV expression is associated with cell growth and prognosis of adenoid cystic carcinoma in the salivary gland

AIMS

Regenerating islet-derived family, member 4 (Reg IV) is associated with the progression of various cancers. The aim was to examine Reg IV expression in adenoid cystic carcinomas (ACCs) in salivary glands.

METHODS AND RESULTS

Reg IV expression was detected by immunohistochemistry and compared with clinicopathological parameters. Expression of phosphorylated epidermal growth factor receptor (pEGFR), phosphorylated AKT (pAKT) and MUC2 was examined by immunohistochemistry. Reg IV function was assessed with Reg IV antisense S-oligodeoxynucleotides (AS) in ACC3 human ACC cells. Reg IV was expressed by salivary duct epithelia and acinus myoepithelia, but not in squamous epithelia. Reg IV expression was found in 41% (17/41) of ACCs, but in none of 40 oral squamous cell carcinomas (OSCCs) and was associated with nodal metastasis (P = 0.047) and poor prognosis (P = 0.012) in ACCs. Reg IV expression was associated with pEGFR (14/17, 82%) in Reg IV+ ACCs, but had no relationship with pAKT or MUC2 expression in ACCs. Cell growth was inhibited by AS treatment in Reg IV+ ACC3 cells, but not in HSC-4 OSCC cells, whereas in vitro invasion of neither cell types was affected by AS treatment.

CONCLUSIONS

These results suggest that Reg IV might accelerate cell growth and disease progression of ACCs.

Effects of small interfering RNA targeting thymidylate synthase on survival of ACC3 cells from salivary adenoid cystic carcinoma

Background

Thymidylate synthase (TS) is an important target for chemotherapeutic treatment of cancer and high expression of TS has been associated with poor prognosis or refractory disease in several cancers including colorectal and head and neck cancer. Although TS is known to regulate cell cycles and transcription factors, its potency as a therapeutic target has not been fully explored in adenoid cystic carcinoma (ACC).

Methods

An ACC cell line (ACC3) was transfected with siRNA targeting the TS gene and inhibition of cell growth and induction of apoptosis-associated molecules were evaluated in vitro. In addition, the in vivo effect of TS siRNA on tumor progression was assessed using a xenograft model.

Results

Our results demonstrated that ACC3 cells showed significantly higher TS expression than non-cancer cell lines and the induction of TS siRNA led to inhibition of cell proliferation. The effect was associated with an increase in p53, p21, and active caspase-3 and S-phase accumulation. We also found up-regulation of spermidine/spermine N1-acetyltransferase (SSAT), a polyamine metabolic enzyme. Furthermore, treatment with TS siRNA delivered by atelocollagen showed a significant cytostatic effect through the induction of apoptosis in a xenograft model.

Conclusion

TS may be an important therapeutic target and siRNA targeting TS may be of potential therapeutic value in ACC.

Aberrant methylation in promoter regions of cyclin-dependent kinase inhibitor genes in adenoid cystic carcinoma of the salivary gland

Adenoid cystic carcinoma (ACC) is a common malignant neoplasm of the salivary gland. The mechanism underlying ACC carcinogenesis is not fully elucidated, although data on associated genetic alterations are accumulating. Cyclin-dependent kinase inhibitors (CKIs) act as tumor suppressors in various cancers, and aberrant methylation in the CKI gene promoter region has been linked to gene silencing and downregulation of expression. The present study investigated methylation of CKI genes, p15, p18, p19, p21, and p27, in 34 cases of ACC. We found frequent and plural methylations of these genes in most cases (68.8% in p15, 90.3% in p18, 78.8% in p19, 92.3% in p21, and 26.5% in p27). Cell cycle disruption induced by these epigenetic aberrations might be important in the tumorigenesis of ACC.

Skp2 expression is associated with down-regulation of p27 protein and cell proliferation in salivary adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is a malignant salivary gland tumor, which shows frequent recurrence and metastasis, ultimately with a poor outcome. We previously demonstrated that p27 down-regulation is frequently found and is due to an enhancement of its degradation in ACC. In this study, we transfected nondegradable p27 mutant (T187A) and wild-type gene into ACC cell line. Transfection of T187A mutant gene was more effective on inhibition of cell growth of ACC cells, suggesting that aberration of p27 degradation may be present in ACC. As F-box protein S-phase kinase-associated protein 2 (Skp2), which is necessary for ubiquitin-mediated degradation of p27, is involved in p27 down-regulation in various cancers, we examined the Skp2 expression and its association with p27 expression in 50 ACC cases. We found Skp2 expression in 36% of ACC cases and inverse association between the expression of Skp2 and p27. Moreover, Skp2 small interfering ribonucleic acid (siRNA) transfection decreased Skp2 protein and accumulation of p27 protein and inhibited the cell growth of ACC cells in vitro. These findings, overall, suggest that Skp2 may play an important role in ACC development through the down-regulation of p27 and that Skp2 siRNA can be a novel modality of cancer gene therapy for suppression of p27 down-regulation in ACC.

Methylation of tumor suppressor genes p16(INK4a), p27(Kip1) and E-cadherin in carcinogenesis

Not only genomic mutations but also abnormal epigenetic methylation can significantly contribute to gene silencing and carcinogenesis. Methylation is particularly often observed in the CpG islands of the promoter regions in the regulatory genes. However, there are considerable differences in the incidence of methylation e.g. in the tumor suppressor genes, so that aberrant methylation of p16(INK4a) is relatively frequently observed in tumors, p27(Kip1) methylation is rare, and the incidence of E-cadherin methylation occurs at an intermediate rate. Although true genomic defects are generally much less common than methylation, parallel tendencies for both are often observed, probably reflecting the different levels of evolutionary advantage for tumor cells from inactivation of different genes. This also suggests that loss of p27 expression could be more a consequence of carcinogenesis, while lost p16 expression is a true oncogenic event. Due to the role of p27 in maintaining cellular quiescence, however, loss of its expression can still be a useful partial indicator of the aggressiveness of cancer. Loss of E-cadherin or its catenin partners of cellular adhesion will result in increasing invasiveness and metastatic potential of neoplastic cells but, because of several alternative routes to the same effect, incidence of lost expression for one component gene like E-cadherin does not need to be very high. Similarly, there must be a relatively high number of genes with modest or low incidence of aberrant silencing by methylation, to reflect multiple alternatives for the multistep process of carcinogenesis. Nevertheless, methylation of different genes also shows characteristic differences between different cancer and tumor types, and the epigenetic methylation patterns therefore have considerable diagnostic and prognostic potential. Realising this potential requires efficient methods for profiling the status of methylation. Such profiling methods have only recently become available and are still under relatively rapid development.

Genetic and epigenetic alteration profiles for multiple genes in salivary gland carcinomas

As combinations of genetic and/or epigenetic alterations occurring during salivary gland carcinogenesis are largely unknown, we here analyzed 36 salivary gland carcinomas (SGCs) for changes in INK4a/ARF, RB1, p21, p27, PTEN, p53, MDM2 and O6-MGMT genes using methylation specific PCR (MSP), loss of heterozygosity (LOH) assays and mutational analysis with immunohistochemistry (IHC), as well as histone H3 and H4 acetylation status. The RB1 gene was found to be the most frequently methylated (41.7% of cases), while methylation of p27(Kip1) and O6-MGMT were less frequent 8.3% and 5.6%, respectively). Two other genes, p21(Waf1) and PTEN, were unmethylated in the SGCs examined. RB1 methylation significantly correlated with loss of expression as determined by IHC (P=0.03), and also a poor prognosis (P=0.02). p53 mutations were found in 8 cases (22.2%), coupled with p14ARF hypermethylation in two cases. LOH in INK4a/ARF and the RB1 locus was observed in 33.3% and 28.6% of the lesions, respectively. There was no correlation between 9p21 LOH and methylation of the INK4a/ARF gene. Promoter hypermethylation of RB1 coupled with LOH was evident in three samples immuno-negative for RB1. Acetylation of histone H3 and H4 was detected in 6 and 5 cases, respectively. These findings indicate that epigenetic silencing of tumour suppressor genes via promoter hypermethylation might be crucial for salivary gland carcinogenesis, particularly in the RB1 gene. Thus epigenetic events including methylation and acetylation as well as genetic alterations may have important contributions.

Dedifferentiated malignant myoepithelioma of the parotid gland

Dedifferentiated salivary gland tumor is a rare, recently recognized tumor type. A case of dedifferentiated malignant myoepithelioma in a 59-year-old man who presented with a painful mass in the left preauricular region is reported. Histologically, two distinct neoplastic cell populations were observed in the same tumor mass. The first population was composed of solid nests of polygonal eosinophilic or glycogen-rich clear cells showing neoplastic myoepithelial immunocytological features, such as positivity for cytokeratins, vimentin, S-100 protein (S-100), alpha-smooth muscle actin (SMA) and glial fibrillary acidic protein (GFAP). A multinodular growth pattern, necrosis and occasional mitotic figures suggested malignancy. This population was diagnosed as low-grade malignant myoepithelioma. The second population infiltrated diffusely into the parotid gland and facial nerves. It consisted of polygonal or short spindle cells with obvious pleomorphism and atypical mitoses. The tumor cells were positive for vimentin and cytokeratins, and showed an accumulation of p53 and cyclin D1. S-100 protein, SMA and GFAP were negative. This population was regarded as undifferentiated carcinoma. A final diagnosis of dedifferentiated malignant myoepithelioma was made. This seems to be the first published case of dedifferentiation in malignant myoepithelioma. Because any tumor type can undergo dedifferentiation with accumulation of additional genetic changes, complete sampling should be the standard approach to all salivary gland tumors in order to avoid missing a dedifferentiation component.

Expression of p16 protein and hypermethylation status of its promoter gene in adenoid cystic carcinoma of the head and neck

Reduced expression of the p16 gene product (protein), an inhibitor of cyclin-D-dependent protein kinase which regulates cell cycle at the G1/S boundary, is implicated in tumor progression in various neoplasms. Hypermethylation of the p16 promoter gene has recently been suggested to be one of the reasons for the reduced protein expression. To explore the role of p16 in the biological behavior of adenoid cystic carcinomas (ACC), we investigated the immunohistochemical expression of p16 protein in 38 ACC tumors (32 primary, 3 recurrent, and 3 metastatic tumors) and the methylation status of its promoter gene. We also examined their relationships to the histological grade of malignancy. Positive reaction of p16 protein was demonstrated in the nuclei of luminar cuboidal cells in areas with tubular patterns. The reactions were reduced in the areas with solid or large cribriform patterns. The levels of p16 expression correlated with the histological grade of malignancy. Recurrent or metastatic tumors did not differ with respect to histological grades from the original tumor except for 1 case, in which p16 expression was reduced compared to the primary tumor. Methylation-specific PCR demonstrated the hypermethylation status of the p16 promoter gene in 4 of 22 primary tumors (21%), all of which showed negative or low expression of the p16 protein. The study indicated that p16 expression was reduced in ACC cases of higher histological grade of malignancy and that hypermethylation of its promoter gene may be involved in its process in some cases.

Overexpression of cyclin D1 and underexpression of p27 predict lymph node metastases in papillary thyroid carcinoma

Lymph node metastasis in papillary thyroid carcinoma increases the morbidity of treatment and the risk of local regional relapse and may also affect cure rates and survival. Factors that predict lymph node metastasis are, however, unclear. We analyzed 125 patients with papillary thyroid carcinoma for factors that predict lymph node metastasis. On univariate analysis, age, extrathyroidal extension, tumor focality, overexpression of cyclin D1, and underexpression of p27 predicted lymph node metastasis, whereas patient gender and tumor size did not. On multivariate analysis, extrathyroidal extension, overexpression of cyclin D1, and underexpression of p27 proved to be strong independent predictors of lymph node metastasis. We suggest that immunohistochemistry for cyclin D1 and p27 will prove valuable in identifying papillary thyroid carcinomas with metastatic potential.

The biology of distant metastases in head and neck cancer

The detection and treatment of metastatic cancer continues to be a challenge for the head and neck oncologist. Unfortunately, head and neck cancer patients who develop distant metastases commonly present late in their course and rapidly succumb to their disease, despite advances in imaging technologies and increased sophistication of biochemical analyses. The development of a rational approach to detection and treatment of metastatic head and neck cancers should begin with an understanding of how these tumors occur and which patients are at greatest risk for developing them. This article presents an overview of the biological processes resulting in the speed of a malignancy from one site to another, with particular attention to head and neck carcinomas. The basic histopathologic, immunology and biochemical abnormalities associated with the development of these secondary tumors are also discussed.