MALT1 Inhibition of Oral Carcinoma Cell Invasion and ERK/MAPK Activation

The expression of mucosa-associated lymphoid tissue 1 (MALT1) that activates nuclear factor (NF)–κB in lymphocyte lineages is rapidly inactivated in oral carcinoma cells at the invasive front and the patients with worst prognosis. However, its mechanism to accelerate carcinoma progression remains unknown, and this study was carried out to examine the role in invasion. HSC2 oral carcinoma cells stably expressing wild-type MALT1 (wtMALT1) reduced the invasion of basement membrane matrices and collagen gels, and the dominant-negative form (∆MALT1)–expressing cells aggressively invaded into collagen gels. MALT1 decelerated proliferation and migration of cells and downregulated expression of matrix metalloproteinase 2 and 9, which were confirmed by short interfering RNA transfections. Reporter assays and immunoblot analysis showed that MALT1 does not affect the NF-κB pathway but inhibits ERK/MAPK activation. This was confirmed by endogenous MALT1 expression in oral carcinoma cell lines. Orthotopic implantation of ∆MALT1-expressing HSC2 cells in mice grew rapid expansive and invasive tongue tumors in contrast to an absence of tumor formation by wtMALT1-expressing cells. These results demonstrate that MALT1 suppresses oral carcinoma invasion by inhibiting proliferation, migration, and extracellular matrix degradation and that the ERK/MAPK pathway is a target of MALT1 and further suggests a role as a suppressor of carcinoma progression.

Epithelial and stromal genetic instability contributes to genesis of colorectal adenomas

BACKGROUND

Previously, we indicated that stromal genetic instability might contribute to tumorigenesis of both sporadic and ulcerative colitis associated colorectal adenocarcinomas. Considering the established adenoma-adenocarcinoma sequence, in this study we analysed genetic instability in colorectal adenoma cells and surrounding stroma.

METHODS

In 164 colorectal tumours (34 hyperplastic polyps, 38 tubular adenomas with low grade dysplasia (TA-L), 51 tubular adenomas with high grade dysplasia (TA-H), and 41 invasive carcinomas), epithelial and stromal genetic instability with National Cancer Institute standard microsatellite markers and chromosome 17 (Chr17) markers, were analysed by a combination of laser capture microdissection and GeneScan approaches.

RESULTS

While frequencies of both loss of heterozygosity (LOH) and microsatellite instability (MSI) were extremely low in hyperplastic polyps, LOH in tubular adenomas was detected in both epithelial (TA-L 13.2%, TA-H 27.5%) and stromal (5.3% and 5.9%, respectively) elements, along with MSI (5.3% and 13.7%, and 5.3 and 5.9%, respectively). Frequencies of epithelial alterations were higher in TA-H than in TA-L, and greatest in the carcinoma group. On the other hand, frequencies of stromal LOH or MSI were almost constant (5.3% approximately 17.1%, 5.3% approximately 17.1%, respectively) in adenomas and invasive carcinomas. In addition, p53 was found to be significantly overexpressed in a greater proportion of TA-L with LOH than in those without genetic instability.

CONCLUSION

The results indicate the presence of genetic alterations in stroma from an early stage of carcinogenesis, accompanied by stepwise increasing genetic instability of epithelia with progression to cancer. Thus microenvironmental changes due to genetic alteration in Chr17 markers in stromal cells may play an important role in colon adenoma and adenocarcinoma development.

[A case of asymptomatic urachal cyst in autopsy--histopathological study of urachal cyst and review of the literature of 99 cases during a 10 year period in Japan]

Disorders of urachal remnants are common. While urachal cysts are usually asymptomatic, infection may mimic a variety of acute abdomen. Here we report a very rare case of urachal cyst that protruded in the urinary bladder cavity and among 99 accumulated cases, only 4 cases have been reported similar to this case characterized by intravesical development from 1990 to 1999. An uninfected urachal cyst was found in a 79-year-old male who had died of bile duct carcinoma. The cyst showed ovoid protrusion into urinary bladder cavity from the dome (3.5 x 2.0 x 2.0 cm in size). Histopathologically, the cyst wall was thin and consisted of fibrous connective tissue with muscular tissue and peripheral nerve, and lined by cuboidal epithelium but no inflammatory cells could be seen. Urachal cysts occur in both sexes are affected with equal frequency, and frequently occur in a younger population. In clinical symptoms the umbilical manifestations are predominant in patients younger than 30 years old, while the bladder manifestations are predominant in those older than 30.

Histopathological studies on virulence of dipeptidyl aminopeptidase IV (DPPIV) of Porphyromonas gingivalis in a mouse abscess model: use of a DPPIV-deficient mutant

To elucidate the role of dipeptidyl aminopeptidase IV (DPPIV) in the virulence of Porphyromonas gingivalis, mice were infected with either a wild-type strain or a DPPIV-deficient mutant using an abscess model. Histopathological analysis of the resulting lesions indicated that DPPIV participates in virulence through the destruction of connective tissue and the less effective mobilization of inflammatory cells.

Sexual dimorphism of porcine amelogenins: male-specific amelogenins have strong adsorption properties onto apatite crystals

The present studies were undertaken to investigate the sexual dimorphism of porcine amelogenins and to gain information as to whether excesses of male amelogenins, if any, possess functional significance in protein-crystal interactions. Enamel proteins, including the intact full-length amelogenins and their degraded polypeptides, were isolated from the secretory enamel of male and female pigs. To identify the amelogenins among the separated pools of male- and female-matrix proteins, rabbit anti-C13 and C25 peptide sera were used, which reacted specifically with the conserved C-terminal domain. Immunoblotting showed that a few extra members of the amelogenins, sharing common epitopes at the C-terminus, were recognized in male products. The apparent yield of the male amelogenins was only marginal, on the basis of their stained intensities on the gel, but the secreted male amelogenins demonstrated selective (probably the strongest among the amelogenins) adsorption properties onto apatite crystals. Reflecting the general symmetric electrophoretic profiles of the male- and female-enamel proteins in toto, there were no sex-linked differences in the protein-crystal interaction and the resulting regulatory function of crystal precipitation.

The secretion of amelogenins is associated with the induction of enamel and dentinoid in an ameloblastic fibro-odontoma

Ameloblastic fibro-odontoma is the unique entity of epithelial-ectomesenchymal odontogenic tumors, which is characterized by enamel formation in addition to dentine. We examined immunohistochemically a case of this tumor in which enamel having prism structures was developed in the absence of odontoblast differentiation but was in contact with mesenchymal matrices. Histological examination showed diverse morphological features of epithelial tumor cells, e.g., cuboidal cells comprising tooth bud-like projections, ameloblast- and stellate reticulum-like cells, and residual cells in forms of extended cords or islands of odontogenic epithelium. Immunostaining with anti-amelogenin sera proved that the intracellular production of amelogenins was initiated at the tooth bud-like stage. The secreted amelogenins were detected almost exclusively in the induced enamel and dentinoid areas, as well as in the core region of cementicle-like spheres deposited in the encapsulating stroma. The results obtained indicate that the odontogenic tumor epithelia and its products, i.e., amelogenins, participate in multifaceted aspects of dental hard tissue formation that takes place during oncogenesis.

Enamel mineralization and an initial crystalline phase

In this communication, we summarized our recent experimental approaches to an unsettled issue, i.e., the nature and role of an acidic precursor in enamel mineralization. The objectives we specially focused our attention on are: the composition, structure and high resolution images of enamel crystals at various developmental stages, thermodynamic and kinetic consideration of octacalcium phosphate (OCP) vs hydroxyapatite (HA) precipitation in physiological media simulating the enamel fluid, reversible changes in the composition and structure of OCP, effects of fluoride at low concentrations and enamel proteins on OCP hydrolysis, and adsorption of enamel proteins onto OCP and fluoridated hydrolysates at neutral pH and room temperature. On the basis of all experimental evidence, we propose that enamel crystal growth comprises two events: the two-dimensional growth of an OCP-like precursor in a narrow outermost zone adjacent to the ameloblasts and the subsequent overgrowth of apatite units on the template under discrete fluid environment in the underlying region distant from the cell layer. The experimental data also support the concept that the whole process of enamel mineralization is modulated substantially through interaction between enamel proteins and crystals including the acidic precursor.

Enzymatic properties of dipeptidyl aminopeptidase IV produced by the periodontal pathogen Porphyromonas gingivalis and its participation in virulence

Porphyromonas gingivalis is a major pathogen associated with adult periodontitis. We cloned and sequenced the gene (dpp) coding for dipeptidyl aminopeptidase IV (DPPIV) from P. gingivalis W83, based on the amino acid sequences of peptide fragments derived from purified DPPIV. An Escherichia coli strain overproducing P. gingivalis DPPIV was constructed. The enzymatic properties of recombinant DPPIV purified from the overproducer were similar to those of DPPIV isolated from P. gingivalis. The three amino acid residues Ser, Asp, and His, which are thought to form a catalytic triad in the C-terminal catalytic domain of eukaryotic DPPIV, are conserved in P. gingivalis DPPIV. When each of the corresponding residues of the enzyme was substituted with Ala by site-directed mutagenesis, DPPIV activity significantly decreased, suggesting that these three residues of P. gingivalis DPPIV are involved in the catalytic reaction. DPPIV-deficient mutants of P. gingivalis were constructed and subjected to animal experiments. Mice injected with the wild-type strain developed abscesses to a greater extent and died more frequently than those challenged with mutant strains. Mice injected with the mutants exhibited faster recovery from the infection, as assessed by weight gain and the rate of lesion healing. This decreased virulence of mutants compared with the parent strain suggests that DPPIV is a potential virulence factor of P. gingivalis and may play important roles in the pathogenesis of adult periodontitis induced by the organism.

Expression of 16 kDa proteolipid of vacuolar-type H(+)-ATPase in human pancreatic cancer

Recent studies have shown that bafilomycin A1-sensitive vacuolar-type H(+)-ATPase (V-ATPase) plays important roles in cell growth and differentiation. However, there is no published study that has focused on the expression of V-ATPase in human tumour tissues. This study was designed to examine the mRNA and protein levels for the 16 kilodalton (kDa) proteolipid of V-ATPase in human pancreatic carcinoma tissues. We first investigated the mRNA level for V-ATPase in six cases of invasive pancreatic cancers and two normal pancreases, using reverse transcription-polymerase chain reaction technique. Then, we examined immunohistochemically the level of V-ATPase protein in 49 pancreatic cancers and ten benign cystic neoplasms of the pancreas, using antisera raised against the 16 kDa proteolipid. There was a notable difference in the level of V-ATPase mRNA between normal and pancreatic carcinoma tissues, with no evident difference in the expression of the beta-actin gene. Immunohistochemically, 42 out of 46 invasive ductal cancers (92%) displayed a mild to marked immunoreactivity for V-ATPase in the cytoplasm, whereas neither non-invasive ductal cancers nor benign cystic neoplasms expressed detectable immunoreactive proteins. These findings suggest that the overexpression of V-ATPase protein is characteristic of invasive pancreatic tumours. V-ATPase may play some crucial roles in tumour progression.

Reversible structural changes of octacalcium phosphate and labile acid phosphate

Acid phosphate is one of the major impurities incorporated into bioapatites, and its quantity and environment in forming mineral have been used as diagnostic probes to pursue acidic precursor(s). Currently, little is known about the structural feature of nonstoichiometric octacalcium phosphate (OCP), which has been advocated to be, most plausibly, mineral salt initially formed during amelogenesis. In the present report, we attempt to define the state of acid phosphate in OCP crystals which were Ca-deficient and contained 40% total phosphate as acid phosphate. We assessed fractions of acid phosphate in discrete environments by extracting the crystals in either deionized water, 10 mmol/L NaOH solution (initial pH 11), or 150 mmol/L Tris buffer at pH 7.4. Solid samples before and after the treatments were examined by chemical analyses and x-ray diffraction. The results indicated that successive extractions with use of the alkaline solution brought about a reversible change (not hydrolysis) in the interior structure of OCP, which accompanied a marked decrease in acid phosphate. A substantial part of the lost acid phosphate was restored during subsequent treatments at neutral pH, and, intriguingly, this restoration accompanied a re-ordering of OCP structure. The data suggested that the acid phosphate in OCP is separated into three pools: (a) a stable pool corresponding to roughly 50 to 60% of the total acid phosphate, (b) a reversibly exchangeable pool corresponding to 25 to 30% of the acid phosphate which may exist either in the water layer or on crystal surfaces, and (c) an unstable (or irreversibly lost) pool corresponding to 15 to 20% of the acid phosphate, a part of which might be explained by the presence of excess hydrogen in OCP. The present work supports the concept that protons and, to a lesser magnitude, phosphate species can diffuse into and out of the OCP lattice prior to initiation of its hydrolytic transition into apatite.

Confocal laser scanning microscopic studies on alveolar bone remodeling with orthodontic tooth movement and retention

Alveolar bone reconstruction in growing dog during the retention period following orthodontic tooth movement was studied. Three beagle dogs (8-10 kg body weight, about one-year-old) were used and two of the animals were subjected to histological observation. The upper 2nd and lower 3rd premolars on both sides were extracted prior to the orthodontic treatments. After a healing period of one month, the upper 3rd premolar and the lower 4th premolar on the right side were moved mesially with a conventional orthodontic force for 8 weeks, and then retained in their new position for 4 weeks. The contralateral corresponding premolars were used as control. The alveolar bone was double-labeled with tetracycline (TC) during the movement and calcein (Cal) during the retention period. Alveolar bone structure and labeling patterns were examined by contact microradiography, conventional fluorescence microscopy, and confocal laser scanning microscopy (CLSM). Optimizing the separation of TC and Cal labelings in the alveolar bone was attained by the simultaneous use of ultraviolet (364 nm) and argon (488 nm) laser sources for excitation of TC and Cal, respectively. Cal labeling, indicative of new bone deposition showed two distinct patterns: lamination at the periodontal surface and rings circumscribing the vascular canal. The cementum surface also exhibited active deposition during the experimental period. Bone formation was affected by slight changes in magnitude and direction of orthodontic or occlusal forces. CLSM is valuable in deciphering the process of alveolar bone remodeling.