Pseudocyst formation by adenoid cystic carcinoma cells in collagen gel culture and in SCID mice

Immunohistochemical analysis of laminin expression in adenoid cystic carcinoma

BACKGROUND AND OBJECTIVES

This study aims at the observation of the immunohistochemical expression of laminin in adenoid cystic carcinoma (ACC) of salivary gland origin and to analyze the distribution of laminin in various components of the tumor and correlate the expression of laminin with the growth and differentiation of the tumor.

MATERIALS AND METHODS

THIRTY CASES OF ACC WERE SUBJECTED TO IMMUNOHISTOCHEMICAL STUDY USING POLYCLONAL ANTIHUMAN LAMININ PRIMARY ANTIBODY, DISTRIBUTION OF LAMININ IN EACH CASE OF ACC WAS OBSERVED IN THE FOLLOWING AREAS: Intracellularly, inner borders of the pseudocystic spaces, within the lumen of the pseudocysts, around the tumor islands and in the intervening stroma.

RESULTS

Laminin positivity was observed in the inner aspect of the pseudocystic spaces in 15 cases, within the lumen of pseudocystic spaces in 22 cases, in the intervening stroma in 20 cases, bordering the tumor islands in 16 cases and intracellularly in 4 cases.

INTERPRETATION AND CONCLUSION

Based on these observations, it can be assumed that laminin plays a major role in proliferation of the tumor cells and in pseudocyst formation. Thus, laminin might play a significant role in the growth and differentiation of ACC and also help in assessing the prognosis of the tumor.

The mutational landscape of adenoid cystic carcinoma

Adenoid cystic carcinomas (ACCs) are among the most enigmatic of human malignancies. These aggressive salivary cancers frequently recur and metastasize despite definitive treatment, with no known effective chemotherapy regimen. Here, we determined the ACC mutational landscape and report the exome or whole genome sequences of 60 ACC tumor/normal pairs. These analyses revealed a low exonic somatic mutation rate (0.31 non-silent events/megabase) and wide mutational diversity. Interestingly, mutations selectively involved chromatin state regulators, such as SMARCA2, CREBBP, and KDM6A, suggesting aberrant epigenetic regulation in ACC oncogenesis. Mutations in genes central to DNA damage and protein kinase A signaling also implicate these processes. We observed MYB-NFIB translocations and somatic mutations in MYB-associated genes, solidifying these aberrations as critical events. Lastly, we identified recurrent mutations in the FGF/IGF/PI3K pathway that may potentially offer new avenues for therapy (30%). Collectively, our observations establish a molecular foundation for understanding and exploring new treatments for ACC.

The effect of proteoglycans inhibited by RNA interference on metastatic characters of human salivary adenoid cystic carcinoma

BACKGROUND

Salivary adenoid cystic carcinoma (SACC) is one of the most common malignancies of salivary gland. Recurrence or/and early metastasis is its biological properties. In SACC, neoplastic myoepithelial cells secrete proteoglycans unconventionally full of the cribriform or tubular and glandular structures of SACC. Literatures have demonstrated that extracellular matrix provided an essential microenvironment for the biological behavior of SACC. However, there is rare study of the effect of proteoglycans on the potential metastasis of SACC.In this study, human xylosyltransferase-I (XTLY-I) gene, which catalyzes the rate-limited step of proteoglycans biosynthesis, was knocked down by RNA interference (RNAi) to inhibit the proteoglycans biosynthesis in SACC cell line with high tendency of lung metastasis (SACC-M). The impact of down-regulated proteoglycans on the metastasis characters of SACC-M cells was analyzed and discussed. This research could provide a new idea for the clinical treatment of SACC.

METHODS

The eukaryotic expression vector of short hairpin RNA (shRNA) targeting XTLY-I gene was constructed and transfected into SACC-M cells. A stably transfectant cell line named SACC-M-WJ4 was isolated. The XTLY-I expression was measured by real-time PCR and Western blot; the reduction of proteoglycans was measured. The invasion and metastasis of SACC-M-WJ4 cells were detected; the effect of down-regulated proteoglycans on the potential lung metastasis of nude mice was observed, respectively.

RESULTS

The shRNA plasmid targeting XTLY-I gene showed powerful efficiency of RNAi. The mRNA level of target gene decreased by 86.81%, the protein level was decreased by 80.10%, respectively. The silence of XTLY-I gene resulted in the reduction of proteoglycans significantly in SACC-M-WJ4 cells. The inhibitory rate of proteoglycans was 58.17% (24 h), 66.06% (48 h), 57.91% (72 h), 59.36% (96 h), and 55.65% (120 h), respectively. The reduction of proteoglycans suppressed the adhesion, invasion and metastasis properties of SACC-M cells, and decreased the lung metastasis of SACC-M cells markedly either.

CONCLUSION

The data suggested that the silence of XTLY-I gene in SACC-M cells could suppress proteoglycans biosynthesis and secretion significantly. The reduction of proteoglycans inhibited cell adhesion, invasion and metastasis of SACC-M cells. There is a close relationship between proteoglycans and the biological behavior of SACC.

Metastasis-associated genes in oral squamous cell carcinoma and salivary adenoid cystic carcinoma: a differential DNA chip analysis between metastatic and nonmetastatic cell systems

Overall modes of differential gene expressions were analyzed between human oral/salivary carcinoma cell systems with (MK-1 and ACCM) and without (ZK-1/ZK-2 and ACC2/ACC3) metastatic potential by using micro-array analysis with cancer-associated DNA chips to determine the kinds of genes associated with metastatic behaviors. MK-1 and/or ACCM showed lower levels of gene expression in extracellular matrix-related molecules, such as collagen type IV, laminin, and adhesion molecules such as cadherin 2, but higher levels of genes which control extracellular matrix degradation, such as MMP 9, as well as cell growth and cycle, such as FGF7 and cyclin D1. Among the differentially expressed genes, similar protein expression tendencies for FGF7, laminin, cyclin D1, and collagen type IV were confirmed by immunofluorescence. Metastatic potentials of oral/salivary carcinoma cells seem to have resulted from certain combinations of over-/underexpression of the genes, which were responsible for extracellular matrix metabolism and cell growth in particular.

Expression of basement membrane components in odontogenic tumors

OBJECTIVE

The objective was to characterize the expression of BMCs (laminins 1 and 5, collagen type IV, and fibronectin) in ameloblastomas, calcifying cystic odontogenic tumors (CCOTs), and adenomatoid odontogenic tumors (AOTs).

STUDY DESIGN

BMCs were analyzed in 14 ameloblastomas, 7 CCOTs, and 7 AOTs using immunohistochemistry.

RESULTS

In normal oral mucosa, linear deposits of these proteins were found at the epithelial-mesenchymal junction, but not in epithelial cytoplasm. In all tumors studied, linear deposits of all proteins were found at the epithelial-mesenchymal junction; laminin 1 was expressed in all tumor cells, regardless of cell types. For CCOTs, laminin 5 was found faintly in suprabasal cells, but expressed strongly in ghost cells. For AOTs, laminin 5 strongly decorated tumor cells adjacent to mineralization.

CONCLUSIONS

Laminin 1 may be a marker for odontogenic epithelium. Additionally, laminin 5 may be involved in ghost cell formation and initiation of calcification.

Effect of Matrigel on adenoid cystic carcinoma cell line differentiation

Adenoid cystic carcinoma (ACC) is a frequent malignant salivary gland neoplasm presenting different growth patterns described as tubular, cribriform and solid, which represent distinct differentiation stages. Cell lines originated from ACCs grown inside three-dimensional environments have not been capable to reproduce all in vivo ACC growth patterns. As ACC cells in vivo present replicated basement membrane, to mimic this situation in vitro ACC cells (CAC2 cells) were grown on the top of a reconstituted basement membrane (Matrigel). Phenotype differences were assessed by light, fluorescence and transmission electron microscopy. The cultures grown on the top of Matrigel presented three-dimensional arrangement of cells intercepted by cellular cords. At these, cell nests pseudocyst formations were observed. This morphological structure entirely reproduced the cribriform growth pattern of ACC. We suggest that the cribriform differentiation of ACC in culture is dependent of proteins and growth factors associated in a bi-dimensional structure.

Knockdown of Sox4 expression by RNAi induces apoptosis in ACC3 cells

Microarray RNA gene expression profiling analysis has shown that Sox4 (Sry-related high mobility group (HMG) box 4) is one of the most upregulated genes in adenoid cystic carcinoma (ACC), relative to non-neoplastic tissue of origin. Here, we show that Sox4 protein is similarly upregulated in ACC by immunohistochemistry of 28 primary cancers and 20 normal tissues. To elucidate the functional significance of these findings, RNA interference (RNAi)-mediated RNA silencing was used to downregulate Sox4 expression in the ACC-derived cell line, ACC3. With confirmed knockdown of Sox4 protein, cell viability was reduced by 51%, with a corresponding increase of apoptosis to 85% as compared to 12% in controls. Apoptosis was confirmed by cell morphology, DNA fragmentation and flow cytometry. Cells could be rescued from the proapoptotic effects of Sox4 RNAi by co-transfection with a construct expressing functional Sox4. Microarray gene expression profiling of RNAi knockdown experiments shows that downregulation of Sox4-modulated expression of critical genes involved in apoptosis and cell cycle control. Overall, our findings suggest that Sox4 contributes to the malignant phenotype of ACC cells by promoting cell survival.

The biological behaviour of human adenoid cystic carcinoma cells transduced with interleukin-2-gene

Adenoid cystic carcinoma (ACC) of the salivary glands is a highly infiltrative malignant tumour with a tendency for lung metastasis. Gene therapy could be a potentially effective therapy for ACC and its metastasis. The aims of the study were: To transduce interleukin-2 (IL-2) gene into an ACC cell line with predisposition for lung metastasis (ACC-M); to compare the bioactivity of the gene-transduced cells and the parent cell line in vitro and in vivo. The IL-2 gene was transduced via a bicistronic retroviral vector into the ACC-M cells. The growth rate and DNA cell cycles of the parent ACC-M, the control viral vector AmGCEN, and the gene transduced AmIL-2 cell cultures were compared quantitatively and by flow cytometry, respectively. The tumourigenic ability of the three cell lines was verified by inoculation in athymic nude mice. The tumours developed were extracted and compared quantitatively and histologically. There was no difference in the growth rate and the DNA count between the ACC-M, AmGCEN, and AmIL-2 cell cultures. In the animal experiment, both the ACC-M and AmGCEN cells stimulated lung metastasis in all the mice, whereas there was no tumour found in the 1 x 10(6) AmIL-2 cells inoculation. On 3 x 10(6) AmIL-2 cells stimulation, three out of six mice developed tumours but the mass and volume of the tumours were smaller than the other two groups. Under light microscopy, the ACC-M tumours were mainly poorly differentiated with minimal cellular matrix, whereas the AmIL-2 tumours were well differentiated with ample matrix. The transduction of IL-2 gene can reduce the tumourigenicity of ACC-M cells and induces tumour cell differentiation in mice. The IL-2 gene can be a potential effective gene for the treatment of adenoid cystic carcinoma of salivary glands and its lung metastasis.

Polymorphous low-grade adenocarcinoma and adenoid cystic carcinoma: distinct architectural composition revealed by collagen IV, laminin and their integrin ligands (alpha2beta1 and alpha3beta1)

AIMS

Polymorphous low-grade adenocarcinoma (PLGA) and adenoid cystic carcinoma (ACC) are malignant salivary gland tumours bearing many similar histological patterns. This study was undertaken to show how the presence and distribution of collagen IV and laminin, and their ligands (integrin alpha2beta1 and alpha3beta1 components), can reveal histoarchitectural differences which distinguish these two entities.

METHODS AND RESULTS

Five cases of ACC and five cases of PLGA from the archives of the Oral Pathology Department of the School of Dentistry of the São Paulo University were submitted to immunostaining with the antibodies to collagen IV, laminin, and integrins alpha2beta1 and alpha3beta1 using the streptavidin-biotin-peroxidase technique. Positive and negative controls were included. PLGA showed a thin line of collagen IV and laminin surrounding structures composed of a single cell layer. Integrins were expressed as a widespread and granular pattern. A thick line of collagen and laminin was observed around the neoplastic structures of ACC. Both integrins were expressed in intercellular spaces and around luminal spaces of tubular structures.

CONCLUSIONS

Collagen IV and laminin, and their integrin ligands, are useful in demonstrating that neoplastic ductal units of PLGA are composed of a single cell layer, being distinct from ACC which contains structures composed of two layers of neoplastic cells.

High-molecular-weight fibronectin synthesized by adenoid cystic carcinoma cells of salivary gland origin

To understand the morphogenesis of characteristic cribriform structures and the frequent invasion of salivary adenoid cystic carcinomas (ACC) along such basement membrane-rich structures as peripheral nerves, we have isolated fibronectin (FN) from the culture media of ACC3 cells established from a parotid ACC and characterized its glycosylation and alternative splicing status. FN isolated from ACC3 cells (ACC-FN) showed a molecular mass of 315 kDa in SDS-PAGE and was less heterogeneous and larger than plasma FN (pFN) or FNs from other cell sources. Differential enzymatic treatments of immunoprecipitated ACC-FN with neuraminidase, peptide-N-glycosidase F and endo-alpha-N-acetylgalactosaminidase revealed that ACC-FN was composed of a polypeptide chain of 270 kDa, with 10 kDa each of N-linked and O-linked oligosaccharide chains. Reverse transcription polymerase chain reaction (RT-PCR), in-situ hybridization, and immunofluorescence studies showed that most ACC-FNs contained ED-A, ED-B and IIICS regions in the molecules. This alternative splicing status of ACC-FN seemed to contribute to its less heterogeneous and larger molecular form. Cell attachment assay demonstrated that ACC-FN was more potent than pFN in adhesion of ACC3 cells. The results indicated that ACC-FN may function as a substrate for attachment of ACC3 cells, or that ACC3 cells trap and retain ACC-FN in their pericellular space. This isoform of FN may play an important role in the mode of invasion of ACC and the formation of stromal pseudocysts in the characteristic cribriform structure of ACC.

Pericoronal hamartomatous lesions in the opercula of teeth delayed in eruption: an immunohistochemical study of the extracellular matrix

Opercula of teeth delayed in eruption were examined histopathologically and immunohistochemically to determine the possible causes for tooth eruption failure. Specimens were obtained from 58 patients with non-erupted teeth by surgical removal of their gingival opercula. Among the 61 specimens, 31 (50.8%) were diagnosed as pericoronal myxofibrous hyperplasia (PMH), 8 (13.1%) as infantile ameloblastic fibromatosis (IAF), and 19 (31.2%) as odontomas. Histopathologically, PMH is characterized by hyperplasia of odontogenic mesenchymal tissues with a myxoid appearance in which odontogenic epithelial islands and mesenchymal multinucleated giant cells are scattered randomly. Between the mucosal epithelium and the PMH, there is a layer of fibrosis, whose matrix is strongly immunopositive for tenascin. The PMH seems to induce its overlying gingival mucosa to remodel the connective tissue, which obstructs tooth eruption. IAF is usually located adjacent to the PMH and shows an ameloblastic fibroma-like histology with atrophic ameloblastic components and poor encapsulation. The findings suggest that IAF associated with PMH is not a true neoplasm and should be distinguished from ameloblastic fibromas by the name of IAF, and that both lesions are included in the range of hamartomas formed only in the pericoronal tissue of teeth in eruption. We propose to categorize these lesions into a new disease entity of pericoronal hamartomas of odontogenic origin.