Muscarinic acetylcholine receptor-mediated phosphorylation of extracellular signal-regulated kinase in HSY salivary ductal cells involves distinct signaling pathways

OBJECTIVES

Typical agonists of G protein-coupled receptors (GPCRs), including muscarinic acetylcholine receptors (mAChRs), activate both G-protein and β-arrestin signaling systems, and are termed balanced agonists. In contrast, biased agonists selectively activate a single pathway, thereby offering therapeutic potential for the specific activation of that pathway. The mAChR agonists carbachol and pilocarpine are known to induce phosphorylation of extracellular signal-regulated kinase-1/2 (ERK1/2) via G-protein-dependent and -independent pathways, respectively. We investigated the involvement of β-arrestin and its downstream mechanisms in the ERK1/2 phosphorylation induced by carbachol and pilocarpine in the human salivary ductal cell line, HSY cells.

METHODS

HSY cells were stimulated with pilocarpine or carbachol, with or without various inhibitors. The cell lysates were analyzed by western blotting using the antibodies p44/p42MAPK and phosphor-p44/p42MAPK.

RESULTS

Western blot analysis revealed that carbachol elicited greater stimulation of ERK1/2 phosphorylation compared to pilocarpine. ERK1/2 phosphorylation was inhibited by atropine and gefitinib, suggesting that mAChR activation induces transactivation of epidermal growth factor receptors (EGFR). Moreover, inhibition of carbachol-mediated ERK1/2 phosphorylation was achieved by GF-109203X (a PKC inhibitor), a βARK1/GRK2 inhibitor, barbadin (a β-arrestin inhibitor), pitstop 2 (a clathrin inhibitor), and dynole 34-2 (a dynamin inhibitor). In contrast, pilocarpine-mediated ERK1/2 phosphorylation was only inhibited by barbadin (a β-arrestin inhibitor) and PP2 (a Src inhibitor).

CONCLUSION

Carbachol activates both G-protein and β-arrestin pathways, whereas pilocarpine exclusively activates the β-arrestin pathway. Additionally, downstream of β-arrestin, carbachol activates clathrin-dependent internalization, while pilocarpine activates Src.

Engineering of an electrically charged hydrogel implanted into a traumatic brain injury model for stepwise neuronal tissue reconstruction

Neural regeneration is extremely difficult to achieve. In traumatic brain injuries, the loss of brain parenchyma volume hinders neural regeneration. In this study, neuronal tissue engineering was performed by using electrically charged hydrogels composed of cationic and anionic monomers in a 1:1 ratio (C1A1 hydrogel), which served as an effective scaffold for the attachment of neural stem cells (NSCs). In the 3D environment of porous C1A1 hydrogels engineered by the cryogelation technique, NSCs differentiated into neuroglial cells. The C1A1 porous hydrogel was implanted into brain defects in a mouse traumatic damage model. The VEGF-immersed C1A1 porous hydrogel promoted host-derived vascular network formation together with the infiltration of macrophages/microglia and astrocytes into the gel. Furthermore, the stepwise transplantation of GFP-labeled NSCs supported differentiation towards glial and neuronal cells. Therefore, this two-step method for neural regeneration may become a new approach for therapeutic brain tissue reconstruction after brain damage in the future.

Insertion of circularly permuted cyan fluorescent protein into the ligand-binding domain of inositol 1,4,5-trisphosphate receptor for enhanced FRET upon binding of fluorescent ligand

Binding of fluorescent ligand (FL) to the cyan fluorescent protein (CFP)-coupled ligand-binding domain of the inositol 1,4,5-trisphosphate (IP₃) receptor (CFP-LBP) produces fluorescence (Förster) resonance energy transfer (FRET). A competitive fluorescent ligand assay (CFLA), using the FRET signal from competition between FLs and IP₃, can measure IP₃ concentration. The FRET signal should be enhanced by attaching a FRET donor to an appropriate position. Herein, we inserted five different circularly permuted CFPs in the loop between the second and third α-helices to generate membrane-targeted fluorescent ligand-binding proteins (LBPs). Two such proteins, LBP-cpC157 and LBP-cpC173, localized at the plasma membrane, displayed FRET upon binding the high-affinity ligand fluorescent adenophostin A (F-ADA), and exhibited a decreased fluorescence emission ratio (480 nm / 535 nm) by 1.6- to 1.8-fold that of CFP-LBP. In addition, binding of a fluorescent low-affinity ligand (F-LL) also reduced the fluorescence ratio in a concentration-dependent manner, with EC₅₀ values for LBP-cpC157 and LBP-cpC173 of 34.7 nM and 27.6 nM, respectively. These values are comparable to that with CFP-LBP (29.2 nM), indicating that insertion of cpC157 and cpC173 did not disrupt LBP structure and function. The effect of 100 nM F-LL on the decrease in fluorescence ratio was reversed upon addition of IP₃, indicating binding competition between F-LL and IP₃. We also constructed cytoplasmic fluorescent proteins cyLBP-cpC157 and cyLBP-cpC173, and bound them to DYK beads for imaging analyses. Application of F-ADA decreased the fluorescence ratio of the beads from the periphery to the center over 3 - 5 min. Application of F-LL also decreased the fluorescence ratio of cyLBP-cpC157 and cyLBP-cpC173 by 20-25%, and subsequent addition of IP₃ recovered the fluorescence ratio in a concentration-dependent manner. The EC₅₀ value and Hill coefficient obtained by curve fitting against the IP₃-dependent recovery of fluorescence ratio can be used to estimate the IP₃ concentration.

Spontaneous calcium responses of SF2 rat dental epithelial cells stably expressing the calcium sensor G-GECO

Genetically-encoded calcium indicators such as G-GECO are useful for studying Ca²⁺ responses during long-term processes. In this study, we employed a lentiviral vector and established a rat dental epithelial cell line that stably expressed G-GECO (SF2-G-GECO). Ca²⁺ imaging analysis under cell culture conditions revealed that SF2-G-GECO cells exhibited spontaneous Ca²⁺ responses, which could be classified into the following three major patterns depending on the cell density: localized Ca²⁺ responses at cell protrusions at a low density, a cell-wide spread of Ca²⁺ responses at a medium density, and Ca²⁺ responses in clusters of 3-20 cells at a high density. The P2Y receptor inhibitor suramin (10 μM), the ATP-degrading enzyme apyrase (5 units/mL), and the fibroblast growth factor (FGF) receptor inhibitor FIIN-2 (1 μM) decreased the frequency of spontaneous Ca²⁺ responses. These results indicate that ATP and FGF are involved in the spontaneous Ca²⁺ responses. SF2 cells differentiate into ameloblasts via interactions with mesenchymal cells. Therefore, SF2-G-GECO cells are expected to be a useful tool for studying the functions of Ca²⁺ responses in regulating gene expression during tooth development.

Synthetic poly(2-acrylamido-2-methylpropanesulfonic acid) gel induces chondrogenic differentiation of ATDC5 cells via a novel protein reservoir function

We previously demonstrated that a synthetic negatively charged poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) gel induced chondrogenic differentiation of ATDC5 cells. In this study, we clarified the underlying molecular mechanism, in particular, focusing on the events that occurred at the interface between the gel and the cells. Gene expression profiling revealed that the expression of extracellular components was enhanced in the ATDC5 cells that were cultured on the PAMPS gel, suggesting that extracellular proteins secreted from the ATDC5 cells might be adsorbed in the PAMPS gel, thereby contributing to the induction of chondrogenic differentiation. Therefore, we created "Treated-PAMPS gel," which adsorbed various proteins secreted from the cultured ATDC5 cells during 7 days. Proteomic analysis identified 27 proteins, including extracellular matrix proteins such as Types I, III, and V collagens and thrombospondin (THBS) in the Treated-PAMPS gel. The Treated-PAMPS gel preferentially induced expression of chondrogenic markers, namely, aggrecan and Type II collagen, in the ATDC5 cells compared with the untreated PAMPS gel. Addition of recombinant THBS1 to the ATDC5 cells significantly enhanced the PAMPS-induced chondrogenic differentiation, whereas knockdown of THBS1 completely abolished this response. In conclusion, we demonstrated that the PAMPS gel has the potential to induce chondrogenic differentiation through novel reservoir functions, and the adsorbed THBS plays a significant role in the induction.

Integrin α4 mediates ATDC5 cell adhesion to negatively charged synthetic polymer hydrogel leading to chondrogenic differentiation

Negatively charged synthetic hydrogels have been known to facilitate various cellular responses including cell adhesion, proliferation, and differentiation; however, the molecular mechanism of hydrogel-dependent control of cell behavior remains unclear. Recently, we reported that negatively charged poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) gel induces chondrogenic differentiation of ATDC5 cells via novel protein reservoir function. In this study, we identified the cell adhesion molecules binding to PAMPS gels that act as mechanoreceptors. First, we performed a pull-down assay by particle gels using cell membrane proteins of ATDC5, and found that multiple membrane proteins bound to the PAMPS gel, whereas the uncharged poly(N,N'-dimethylacrylamide) gel as control did not bind to any membrane proteins. Western blot analysis indicated differential binding of integrin (ITG) isoforms to the PAMPS gel, in which the α4 isoform, but not α5 and αv, efficiently bound to the PAMPS gel. ITG α4 knockdown decreased cell spreading of ATDC5 on PAMPS gels, whereas the enhanced expression increased the behavior. Furthermore, ITG α4 depletion suppressed PAMPS gel-induced expression of bone morphogenic protein (BMP) 4 contributing to chondrogenic differentiation, in concordance with the reduction of ERK activation. These results demonstrated that membrane protein binding to PAMPS gels occurred in a charge-dependent manner, and that ITG α4 plays a crucial role in cell spreading on PAMPS gels and acts as a mechanoreceptor triggering cellular signaling leads to chondrogenic differentiation.

Exosomes containing ErbB2/CRK induce vascular growth in premetastatic niches and promote metastasis of bladder cancer

Locally advanced and metastatic invasive bladder cancer (BC) has a poor prognosis, and no advanced therapies beyond cisplatin‐based combination chemotherapy have been developed. Therefore, it is an urgent issue to elucidate the underlying mechanisms of tumor progression and metastasis of invasive BC for the development of new therapeutic strategies. Here, we clarified a novel role of exosomes containing ErbB2 and CRK in a formation of premetastatic niches and subsequent metastases. CRK adaptors were overexpressed in invasive UM‐UC‐3 BC cells. In an orthotopic xenograft model, metastases to lung, liver, and bone of UM‐UC‐3 cells were completely abolished by CRK elimination. Mass spectrometry analysis identified that ErbB2 was contained in UM‐UC‐3‐derived exosomes in a CRK‐dependent manner; the exosomes significantly increased proliferation and invasion properties of low‐grade 5637 BC cells and HUVECs through FAK and PI3K/AKT signaling pathways. In athymic mice educated with UM‐UC‐3‐derived exosomes, i.v. implanted UM‐UC‐3 cells were trapped with surrounding PKH67‐labeled exosomes in lung and led to development of lung metastasis with disordered vascular proliferation. In contrast, exosomes derived from CRK‐depleted BC cells failed to induce these malignant features. Taken together, we showed that CRK adaptors elevated the expression of ErbB2/3 in BC cells, and these tyrosine kinase/adaptor units were transferred from host BC cells to metastatic recipient cells by exosomes, leading to vascular leakiness and proliferation and contributing to the formation of distant metastasis. Thus, CRK intervention with ErbB2/3 blockade might be a potent therapeutic strategy for patients with ErbB2 overexpressing advanced and metastatic BC.

Micro patterning of hydroxyapatite by soft lithography on hydrogels for selective osteoconduction

Mechanically robust hydrogels are promising biomaterials as artificial supportive tissue. These applications require selective and robust bonding of the hydrogels to living tissue. Recently, we achieved strong in vivo bone bonding of a tough double network (DN) hydrogel, a potential material for use as artificial cartilage and tendon, by hybridizing osteoconductive hydroxyapatite (HAp) in the gel surface layer. In this work, we report micro patterning of HAp at the surface of the DN hydrogel for selective osteoconduction. Utilizing the dissolution of HAp in an acidic environment, the soft lithography technique using an acid gel stamp was adopted to form a high-resolution HAp pattern on the gel. The HAp-patterned gel showed well-regulated migration and adhesion of cells in vitro. Moreover, the HAp-patterned gel showed selective and robust bonding to the rabbit bone tissue in vivo. This HAp soft lithography technique allows for simple and quick preparation of tailor-made osteoconductive hydrogels and can be applied to other hydrogels for selective bone bonding. STATEMENT OF SIGNIFICANCE: Hydrogels, preserving large amount of water, have been studied for next-generation artificial soft tissues. However, fixation of hydrogels to living tissue was unsolved issue for clinical application. Recently, we achieved robust bonding of a tough double network gel to bone in vivo by coating of osteoconductive hydroxyapatite in the gel surface layer. For further progress for practical use, we report the micro patterning of HAp at the surface of the DN hydrogel by using soft lithography technique, to perform selective bonding to only objective area without unnecessary coalescence. The HAp lithography technique is simple, quick and non-toxic method to prepare tailor-made osteoconductive hydrogels and has universality of species of hydrogels.

Activation of focal adhesion kinase via M1 muscarinic acetylcholine receptor is required in restitution of intestinal barrier function after epithelial injury

Impairment of epithelial barrier is observed in various intestinal disorders including inflammatory bowel diseases (IBD). Numerous factors may cause temporary damage of the intestinal epithelium. A complex network of highly divergent factors regulates healing of the epithelium to prevent inflammatory response. However, the exact repair mechanisms involved in maintaining homeostatic intestinal barrier integrity remain to be clarified. In this study, we demonstrate that activation of M1 muscarinic acetylcholine receptor (mAChR) augments the restitution of epithelial barrier function in T84 cell monolayers after ethanol-induced epithelial injury, via ERK-dependent phosphorylation of focal adhesion kinase (FAK). We have shown that ethanol injury decreased the transepithelial electrical resistance (TER) along with the reduction of ERK and FAK phosphorylation. Carbachol (CCh) increased ERK and FAK phosphorylation with enhanced TER recovery, which was completely blocked by either MT-7 (M1 antagonist) or atropine. The CCh-induced enhancement of TER recovery was also blocked by either U0126 (ERK pathway inhibitor) or PF-228 (FAK inhibitor). Treatment of T84 cell monolayers with interferon-γ (IFN-γ) impaired the barrier function with the reduction of FAK phosphorylation. The CCh-induced ERK and FAK phosphorylation were also attenuated by the IFN-γ treatment. Immunological and binding experiments exhibited a significant reduction of M1 mAChR after IFN-γ treatment. The reduction of M1 mAChR in inflammatory area was also observed in surgical specimens from IBD patients, using immunohistochemical analysis. These findings provide important clues regarding mechanisms by which M1 mAChR participates in the maintenance of intestinal barrier function under not only physiological but also pathological conditions.

M1 is a major subtype of muscarinic acetylcholine receptors on mouse colonic epithelial cells

BACKGROUND

Muscarinic acetylcholine receptors (mAChRs) are major regulators of gut epithelial functions. However, the precise subtype composition has not been clarified.

METHODS

We characterized the pharmacological profile of mAChRs on mouse colonic crypts, employing [(3)H]-N-methyl scopolamine chloride as a radioligand and several subtype-selective chemicals, and the functional aspect by measuring short-circuit current (I sc) in Ussing chambers and by evaluating MAP kinase phosphorylation in mouse colonic mucosal sheets.

RESULTS

The mAChRs were detected on the crypts (K d = 163.2 ± 32.3 pM, B max = 47.3 ± 2.6 fmol/mg of total cell protein). Muscarinic toxin 7 (MT-7, M1 subtype selective) gave a displacement curve with high affinity, but there was a part insensitive to MT-7 (18.8 ± 0.4 % of the total specific binding). The MT-7-insensitive component was displaced completely by darifenacin (M3 selective) with high affinity. ACh induced an increase in I sc, which was significantly enhanced by MT-7 but was completely inhibited by darifenacin or atropine. Colitis induction resulted in a significant decrease in the density of mAChRs, which occurred mainly in the MT-7-sensitive component (M1 subtype). Immunological experiments exhibited a reduction of M1 but not of M3 signal after colitis induction. Muscarinic stimulation induced an increase in MAP kinase phosphorylation, which was completely suppressed by MT-7 and was attenuated by inflammation, in mouse colonic epithelium.

CONCLUSIONS

These results suggest that mAChRs in mouse colonic epithelial cells consist of two subtypes, M1 (80 %) and M3 (20 %). The major M1 subtype was likely to regulate epithelial chloride secretion negatively and was susceptible to inflammation and may be relevant to inflammatory gut dysfunction.

Role of JC virus agnoprotein in virion formation

JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and causes progressive multifocal leukoencephalopathy in humans. JCV encodes early proteins (large T antigen, small T antigen, and T' antigen) and four late proteins (agnoprotein, and three viral capsid proteins, VP1, VP2, and VP3). In the current study, a novel function for JCV agnoprotein in the morphogenesis of JC virion particles was identified. It was found that mature virions of agnoprotein-negative JCV are irregularly shaped. Sucrose gradient sedimentation and cesium chloride gradient ultracentrifugation analyses revealed that the particles of virus lacking agnoprotein assemble into irregularly sized virions, and that agnoprotein alters the efficiency of formation of VP1 virus-like particles. An in vitro binding assay and immunocytochemistry revealed that agnoprotein binds to glutathione S-transferase fusion proteins of VP1 and that some fractions of agnoprotein colocalize with VP1 in the nucleus. In addition, gel filtration analysis of formation of VP1-pentamers revealed that agnoprotein enhances formation of these pentamers by interacting with VP1. The present findings suggest that JCV agnoprotein plays a role, similar to that of SV40 agnoprotein, in facilitating virion assembly.

Ablation of smooth muscle caldesmon affects the relaxation kinetics of arterial muscle

Smooth muscle caldesmon (h-CaD) is an actin- and myosin-binding protein that reversibly inhibits the actomyosin ATPase activity in vitro. To test the function of h-CaD in vivo, we eliminated its expression in mice. The h-CaD-null animals appeared normal and fertile, although the litter size was smaller. Tissues from the homozygotes lacked h-CaD and exhibited upregulation of the non-muscle isoform, l-CaD, in visceral, but not vascular tonic smooth muscles. While the Ca(2+) sensitivity of force generation of h-CaD-deficient smooth muscle remained largely unchanged, the kinetic behavior during relaxation in arteries was different. Both intact and permeabilized arterial smooth muscle tissues from the knockout animals relaxed more slowly than those of the wild type. Since this difference occurred after myosin dephosphorylation was complete, the kinetic effect most likely resulted from slower detachment of unphosphorylated crossbridges. Detailed analyses revealed that the apparently slower relaxation of h-CaD-null smooth muscle was due to an increase in the amplitude of a slower component of the biphasic tension decay. While the identity of this slower process has not been unequivocally determined, we propose it reflects a thin filament state that elicits fewer re-attached crossbridges. Our finding that h-CaD modulates the rate of smooth muscle relaxation clearly supports a role in the control of vascular tone.

Regulation of PTEN expression by the SWI/SNF chromatin-remodelling protein BRG1 in human colorectal carcinoma cells

Background:

Aberrant expression of Brahma-related gene-1 (BRG1), a core component of the SWI/SNF chromatin-remodelling complex, has been implicated in cancer development; however, the biological significance of BRG1 in colorectal carcinoma (CRC) remains unknown.

Methods:

In CRC tissues, expression of BRG1 and Brahma (BRM) was investigated immunohistochemically. Colorectal carcinoma-derived DLD-1 cells were used for knockdown of BRG1 and PTEN with small interfering RNA (siRNA) and transduction of Akt. Complementary DNA (cDNA) microarray analysis was performed to explore the genes affected by BRG1.

Results:

Expression of BRG1, but not BRM, was frequently elevated in CRC specimens, and knockdown of BRG1 suppressed cell proliferation of DLD-1 cells. By cDNA microarray, we determined that PTEN expression was negatively regulated by BRG1 in DLD-1 cells, which subsequently influenced the cyclin D1 levels via the phosphoinositide 3-OH kinase (PI3K)–Akt signalling pathway. The interplay of BRG1 on cyclin D1 expression was confirmed by the introduction of Akt and knockdown of PTEN in the BRG1 siRNA-transduced DLD-1 cells. Interestingly, this positive correlation between BRG1 and cyclin D1 expression was also observed in CRC specimens.

Conclusion:

Brahma-related gene-1 has an important role in the process of CRC development by activating the PI3K–Akt signalling pathway and resultant upregulation of cyclin D1 levels.

Oxazolone-induced over-expression of focal adhesion kinase in colonic epithelial cells of colitis mouse model

We examined the change of protein tyrosine kinases (PTKs) expression levels in colonic epithelial cells isolated from mice in which colitis was induced by oxazolone administration, using the monoclonal antibody YK34, which cross-reacts with a wide variety of PTKs. We identified focal adhesion kinase (FAK) and found the expression level increased due to the induction of colitis. Furthermore, we found that there was a positive correlation between FAK expression and the severity of colitis. Also, FAK expression localized in the colonic epithelium but not in the lamina propria, implying FAK functions in epithelial cells during colitis formation and/or wound repairing.

Direct cancer-stromal interaction increases fibroblast proliferation and enhances invasive properties of scirrhous-type gastric carcinoma cells

BACKGROUND

Scirrhous-type gastric carcinoma (SGC) exhibits an extensive submucosal fibrosis and extremely poor patient prognosis. We investigated the importance of the cancer-stromal interaction in the histogenesis of SGC.

METHODS

Gastric fibroblasts NF-25 and intestinal fibroblasts NF-j2 were co-cultured with SGC-derived (HSC-39) or non-SGC-derived (HSC-57 and HSC-64) cells. To identify genes that are up- or downregulated in NF-25, complementary DNA (cDNA) microarray analysis was performed. The antibody against vascular-cell adhesion molecule-1 (VCAM-1) was used for cell growth test and immunohistochemistry. Moreover, the impact of interaction with NF-25 fibroblasts on HSC-39 cells was investigated using western blot and reverse transcription-polymerase chain reaction.

RESULTS

HSC-39 cells stimulated growth of NF-25 but not NF-j2 when co-cultured. Induction of VCAM-1 in NF-25 fibroblasts was identified, which was specific when co-cultured with HSC-39 but not with non-SGC-derived HSC-57 and HSC-64 cells. Neutralising antibody to VCAM-1 suppressed NF-25 growth in dose-dependent manners. In tissue samples, positive immunoreactivity of VCAM-1 in SGC-derived fibroblasts was significantly higher than that in non-SGC-derived fibroblasts. Furthermore, interaction with NF-25 fibroblasts not only induced the epithelial-mesenchymal transition-like change, but also expressions of matrix metalloproteinase- related genes in HSC-39 cells.

CONCLUSION

Direct interaction between SGC cells and gastric fibroblasts establishes the tumour microenvironment and reinforces the aggressiveness of SGC.

Nitric oxide-induced biphasic mechanism of vascular relaxation via dephosphorylation of CPI-17 and MYPT1

Nitric oxide (NO) from endothelium is a major mediator of vasodilatation through cGMP/PKG signals that lead to a decrease in Ca(2+) concentration. In addition, NO-mediated signals trigger an increase in myosin light chain phosphatase (MLCP) activity. To evaluate the mechanism of NO-induced relaxation through MLCP deinhibition, we compared time-dependent changes in Ca(2+), myosin light chain (MLC) phosphorylation and contraction to changes in phosphorylation levels of CPI-17 at Thr38, RhoA at Ser188, and MYPT1 at Ser695, Thr696 and Thr853 in response to sodium nitroprusside (SNP)-induced relaxation in denuded rabbit femoral artery. During phenylephrine (PE)-induced contraction, SNP reduced CPI-17 phosphorylation to a minimal value within 15 s, in parallel with decreases in Ca(2+) and MLC phosphorylation, followed by a reduction of contractile force having a latency period of about 15 s. MYPT1 phosphorylation at Ser695, the PKG-target site, increased concurrently with relaxation. Phosphorylation of RhoA, MYPT1 Thr696 and Thr853 differed significantly at 5 min but not within 1 min of SNP exposure. Inhibition of Ca(2+) release delayed SNP-induced relaxation while inhibition of Ca(2+) channel, BK(Ca) channel or phosphodiesterase-5 did not. Pretreatment of resting artery with SNP suppressed an increase in Ca(2+), contractile force and phosphorylation of MLC, CPI-17, MYPT1 Thr696 and Thr853 at 10 s after PE stimulation, but had no effect on phorbol ester-induced CPI-17 phosphorylation. Together, these results suggest that NO production suppresses Ca(2+) release, which causes an inactivation of PKC and rapid CPI-17 dephosphorylation as well as MLCK inactivation, resulting in rapid MLC dephosphorylation and relaxation.

DDX1 promotes proliferation of the JC virus through transactivation of its promoter

Recently, we demonstrated that the DEAD box protein 1 (DDX1), an RNA helicase, and the cleavage stimulation factor (CstF) form a complex that binds to the JC virus transcriptional control region (JCV-TCR). Here, we examined the function of DDX1, which is expressed at much higher levels in the JCV-susceptible cell line IMR-32 than in non-susceptible cell lines. DDX1 had no effect on the replication efficiency of JCV, but overexpression of DDX1 significantly increased transactivation of the JCV promoter. Furthermore, DDX1 enhanced the expression of JCV proteins in JCV infected cells, and knockdown of DDX1 using small interfering (si) RNA suppressed the expression of JCV proteins. Our results clearly demonstrate that DDX1 regulates proliferation of JCV in vitro through transcriptional activation.

Identification of DDX1 as a JC virus transcriptional control region-binding protein

To investigate the mechanism behind JC virus (JCV) cell specificity we performed electrophoretic mobility shift assays (EMSA) using probes derived from the JCV transcriptional control region (JCV-TCR). Using nuclear extracts from the JCV-susceptible neuroblastoma cell line IMR-32, EMSA revealed a 670 kDa JCV-TCR-binding protein complex designated as #3-bp. This complex could not be detected in nuclear extracts from non-susceptible cell lines. Using column chromatographic purifi-cation and microsequencing, we identified cleavage stimulation factor (CstF) as a component of #3-bp. However, as CstF is present in many cell types, we speculated that the IMR-32-specific component(s) of #3-bp bind CstF. We performed a yeast two-hybrid assay using CstF-77 as the bait against a HeLa cDNA-subtracted IMR-32 cDNA library. This analysis detected binding between CstF-77 and the RNA helicase DDX1. Subsequently, biotinylated DNA affinity precipitation and chromatin immunoprecipitation assays also confirmed that DDX1 binds specifically to JCV-TCR. Our findings indicate that an association between DDX1 and the JCV-TCR may play a significant role in JCV infection in IMR-32 cells.

High PRL-3 expression in human gastric cancer is a marker of metastasis and grades of malignancies: an in situ hybridization study

Phosphatase of regenerating liver (PRL)-3, encoding a 22-kD low molecular weight tyrosine phosphatase, has been reported to be associated with metastasis of colorectal carcinoma. We assessed the levels of PRL-3 mRNA expression to know whether its up-regulation was involved in progression and metastasis of gastric carcinoma. Levels of PRL-3 expression in 94 human gastric adenocarcinomas and 54 matched lymph node metastases were detected by in situ hybridization and compared with clinicopathological characteristics including prognosis. High PRL-3 expression was detected in 36.2% of primary gastric carcinoma (with nodal metastasis, 55.6%; without nodal metastasis, 10%; P < 0.001) and in 74.1% of lymph node metastases. The incidence of high PRL-3 expression in lymph node metastasis was significantly higher than in primary tumors (P < 0.044). Moreover, high expression of PRL-3 was closely associated with tumor size, lymphatic invasion, venous invasion, extent of lymph node metastasis, and tumor stage. These results suggest that high PRL-3 expression may participate in the progression and metastasis of gastric carcinoma. PRL-3 might be a novel molecular marker for aggressive gastric cancer.

Assessment of microsatellite instability status for the prediction of metachronous recurrence after initial endoscopic submucosal dissection for early gastric cancer

The technique of endoscopic submucosal dissection (ESD) has been developed for en bloc resection of early gastric cancer (EGC); however, little is known about the risk of metachronous cancer in the remnant stomach after initial ESD. In this study, we investigated the correlation between microsatellite instability (MSI) status and the incidence of metachronous recurrence of gastric cancer. According to the genetic/molecular background determined with MSI status and expression levels of hMLH1 and p53 tumour suppressor, 110 EGCs removed with ESD were subclassified into three groups: the mutator/MSI-type (8%), suppressor/p53-type (45%) and unclassified type (47%). Interestingly, patients with the mutator/MSI-type tumour had a high incidence (67%) of metachronous recurrence of gastric cancer within a 3-year observation after initial ESD, which was significantly higher than those with the suppressor/p53-type and unclassified type tumours (P<0.01). Although we investigated mucin phenotypes, there was no correlation between mucin phenotype and the recurrence of EGC. These findings suggest that subclassification of molecular pathological pathways in EGCs is required for the assessment of patients with a high risk of recurrent gastric cancer. The information delivered from our investigation is expected to be of value for decisions about therapy and surveillance after ESD.

Ca2+-dependent rapid Ca2+ sensitization of contraction in arterial smooth muscle

Ca(2+) ion is a universal intracellular messenger that regulates numerous biological functions. In smooth muscle, Ca(2+) with calmodulin activates myosin light chain (MLC) kinase to initiate a rapid MLC phosphorylation and contraction. To test the hypothesis that regulation of MLC phosphatase is involved in the rapid development of MLC phosphorylation and contraction during Ca(2+) transient, we compared Ca(2+) signal, MLC phosphorylation, and 2 modes of inhibition of MLC phosphatase, phosphorylation of CPI-17 Thr38 and MYPT1 Thr853, during alpha(1) agonist-induced contraction with/without various inhibitors in intact rabbit femoral artery. Phenylephrine rapidly induced CPI-17 phosphorylation from a negligible amount to a peak value of 0.38+/-0.04 mol of Pi/mol within 7 seconds following stimulation, similar to the rapid time course of Ca(2+) rise and MLC phosphorylation. This rapid CPI-17 phosphorylation was dramatically inhibited by either blocking Ca(2+) release from the sarcoplasmic reticulum or by pretreatment with protein kinase C inhibitors, suggesting an involvement of Ca(2+)-dependent protein kinase C. This was followed by a slow Ca(2+)-independent and Rho-kinase/protein kinase C-dependent phosphorylation of CPI-17. In contrast, MYPT1 phosphorylation had only a slow component that increased from 0.29+/-0.09 at rest to the peak of 0.68+/-0.14 mol of Pi/mol at 1 minute, similar to the time course of contraction. Thus, there are 2 components of the Ca(2+) sensitization through inhibition of MLC phosphatase. Our results support the hypothesis that the initial rapid Ca(2+) rise induces a rapid inhibition of MLC phosphatase coincident with the Ca(2+)-induced MLC kinase activation to synergistically initiate a rapid MLC phosphorylation and contraction in arteries with abundant CPI-17 content.

Fhit modulation of the Akt-survivin pathway in lung cancer cells: Fhit-tyrosine 114 (Y114) is essential

The Fhit tumor suppressor binds and hydrolyses diadenosine polyphosphates and the Fhit-substrate complex has been proposed as a proapoptotic effector, as determined by infection of susceptible cancer cells with adenoviruses carrying wild-type fragile histidine triad (FHIT) or catalytic site mutants. The highly conserved Fhit tyrosine 114 (Y114), within the unstructured loop C-terminal of the catalytic site, can be phosphorylated by Src family tyrosine kinases, although endogenous phospho-Fhit is rarely detected. To explore the importance of Y114 and identify Fhit-mediated signaling events, wild-type and Y114 mutant FHIT-expressing adenoviruses were introduced into two human lung cancer cell lines. Caspase-dependent apoptosis was effectively induced only by wild-type but not Y114 mutant Fhit proteins. By expression profiling of FHIT versus mutant FHIT-infected cells, we found that survivin, an Inhibitor of Apoptosis Protein (IAP) family member, was significantly decreased by wild-type Fhit. In addition, Fhit inhibited activity of Akt, a key effector in the phosphatidylinositol 3-OH kinase (PI3K) pathway; loss of endogenous Fhit expression caused increased Akt activity in vitro and in vivo, and overexpression of constitutively active Akt inhibited Fhit-induced apoptosis. The results indicate that the Fhit Y114 residue plays a critical role in Fhit-induced apoptosis, occurring through inactivation of the PI3K-Akt-survivin signal pathway.

Identification of FEZ1 as a protein that interacts with JC virus agnoprotein and microtubules: role of agnoprotein-induced dissociation of FEZ1 from microtubules in viral propagation

The human polyomavirus JC virus (JCV) is the causative agent of a fatal demyelinating disease, progressive multifocal leukoencephalopathy, and encodes six major proteins, including agnoprotein. Agnoprotein colocalizes with microtubules in JCV-infected cells, but its function is not fully understood. We have now identified fasciculation and elongation protein zeta 1 (FEZ1) as a protein that interacted with JCV agnoprotein in a yeast two-hybrid screen of a human brain cDNA library. An in vitro binding assay showed that agnoprotein interacted directly with FEZ1 and microtubules. A microtubule cosedimentation assay revealed that FEZ1 also associates with microtubules and that agnoprotein induces the dissociation of FEZ1 from microtubules. Agnoprotein inhibited the promotion by FEZ1 of neurite outgrowth in PC12 cells. Conversely, overexpression of FEZ1 suppressed JCV protein expression and intracellular trafficking in JCV-infected cells. These results suggest that FEZ1 promotes neurite extension through its interaction with microtubules, and that agnoprotein facilitates JCV propagation by inducing the dissociation of FEZ1 from microtubules.

Nuclear Entry Mechanism of the Human Polyomavirus JC Virus-like Particle

JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and causes progressive multifocal leukoencephalopathy in humans. Although transport of virions to the nucleus is an important step in JCV infection, the mechanism of this process has remained unclear. The outer shell of the JCV virion comprises the major capsid protein VP1, which possesses a putative nuclear localization signal (NLS), and virus-like particles (VLPs) consisting of recombinant VP1 exhibit a virion-like structure and physiological functions (cellular attachment and intracytoplasmic trafficking) similar to those of JCV virions. We have now investigated the mechanism of nuclear transport of JCV with the use of VLPs. Wild-type VLPs (wtVLPs) entered the nucleus of most HeLa or SVG cells. The virion structure of VLPs was preserved during transport to the nucleus as revealed by confocal microscopy of cells inoculated with fluorescein isothiocyanate-labeled wtVLPs containing packaged Cy3. The nuclear transport of wtVLPs in digitonin-permeabilized cells was dependent on the addition of importins alpha and beta and was prevented by wheat germ agglutinin or by antibodies to the nuclear pore complex. The nuclear entry of VLPs composed of VP1 with a mutated NLS was greatly inhibited, compared with that of wtVLPs, in both intact and permeabilized cells. Unlike wtVLPs, the mutant VLPs did not bind to importins alpha or beta. Limited proteolysis analysis revealed that the NLS of VP1 was exposed on the surface of wtVLPs. These results suggest that JCV VLPs bind to cellular importins via the NLS of VP1 and are transported into the nucleus through the nuclear pore complex.

Frequent nuclear accumulation of beta-catenin in pituitary adenoma

BACKGROUND

Beta-catenin (CTNNB1) is known to be a member of the cadherin-catenin superfamily and to function in cell-cell adhesion. However, it also has been reported that CTNNB1 plays an important role in carcinogenesis. In the current study, the authors observed expression of the CTNNB1 protein in primary pituitary adenomas to investigate the role of CTNNB1 in the development of pituitary adenomas.

METHODS

A total of 37 pituitary adenomas were analyzed. Expression of CTNNB1 and the cell proliferation marker Ki-67 were observed immunohistochemically. In addition, the authors performed direct sequencing to detect somatic mutations of exon 3 of the CTNNB1 gene.

RESULTS

Twenty-one of 37 pituitary adenomas (57%) demonstrated abnormal nuclear accumulation of CTNNB1. It is interesting to note that tumors with an accumulation of CTNNB1 in the nucleus showed a statistical tendency toward an association with increased immunoreactivity of Ki-67 (P < 0.05) whereas no significant correlation was detected between the status of CTNNB1 and other clinicopathologic features. Missense mutations in exon 3 of the CTNNB1 gene also were detected in the cases with abnormal nuclear accumulation of the CTNNB1 protein.

CONCLUSIONS

The results of the current study suggest that up-regulation of the Wnt signaling pathway, including accumulation of mutant CTNNB1 in the nuclei, plays an important role in the tumorigenesis and development of adenoma in the pituitary gland.

The cadherin-catenin superfamily in endocrine tumors

It has been well-known that the cadherin-catenin complexes bind with intracellular skeleton actin, which result in stabilization of cellular structure and tissue organization. Therefore, the cadherin-catenin family has been considered prerequisite for normal cell function and the preservation of tissue integrity. In human malignancies especially colon cancers, dysfunction and/or decrease of expression of these proteins have been proposed to prevent differentiation of tumors and to increase invasiveness and poor prognosis. However, recent studies also revealed that a member of this superfamily, beta-catenin, may play an important role in Wnt/wingless intracellular signaling pathway. Decreased expression of this protein or somatic mutation of the beta-catenin gene has been also reported in human carcinomas including various endocrine tumors. Mutant beta-catenin is associated with abnormal nuclear accumulation in tumor cells and subsequently to activate other transcription factors such as Tcf/Lef. This activation eventually results in which upregulation of mRNA and protein levels of various cell growth mediators in these endocrine tumors. Therefore, dysfunction of the cadherin-catenin system is considered to be closely correlated with tumorigenesis and development in human endocrine tumors.

Not hMSH2 but hMLH1 is frequently silenced by hypermethylation in endometrial cancer but rarely silenced in pancreatic cancer with microsatellite instability

Disruption of the DNA mismatch repair (MMR) system has been found to play an important role in sporadic human cancers of several organs such as colorectum, stomach, endometrium, and pancreas. In cancers of the former three organs, disruption of the MMR system is mainly caused by hypermethylation of the hMLH1 gene. We investigated the expression of the hMLH1 and hMSH2 proteins immunohistochemically in pancreatic and endometrial cancers with high frequency microsatellite instability (MSI-H). Loss of expression of hMLH1 was found in none of seven pancreatic cancer, whereas eight (57%) of 14 endometrial cancer showed loss of expression of hMLH1. On the other hand, one (14%) of seven pancreatic cancers and two (14%) of 14 endometrial cancers showed loss of hMSH2 expression. We further analyzed the methylation status at the promoter region of the hMLH1 and hMSH2 genes and found hypermethylation of hMLH1 at the promoter region in the great majority of endometrial cancers with loss of expression. However, no pancreatic cancer showed hypermethylation. We then further analyzed 22 pancreatic cancer cell lines and obtained similar results. These results suggested that MSI-H in pancreatic cancer is probably caused by different mechanisms from those of other sporadic cancers with MSI-H.

An autopsy case of ovarian hyperstimulation syndrome with massive pulmonary edema and pleural effusion

Ovarian hyperstimulation syndrome (OHSS) is the most serious complication of ovulation induction with exogenous gonadotropins, such as human menopausal gonadotropin and follicle-stimulating hormone. These hormones are considered to increase capillary permeability and cause third space fluid shift. We report an autopsy case of severe OHSS in a 28-year-old Japanese female. The patient developed bilateral chest pain and progressive dyspnea during the course of administration of human gonadotropins. Pleural effusion and hypouresis clinically disappeared 4 days after the onset of the symptoms, but the patient died suddenly of rapid respiratory insufficiency. Autopsy examination revealed massive pulmonary edema, intra-alveolar hemorrhage and pleural effusion without any evidence of pulmonary thromboembolism. Histopathological examination of the ovary demonstrated multiple well-developed follicle formations, consistent with OHSS. It is very important to recognize that massive pulmonary edema can occur in a patient with OHSS. To the best of our knowledge, this is the first autopsy report of a patient with severe OHSS.

Analysis of the candidate target genes for mutation in microsatellite instability-positive cancers of the colorectum, stomach, and endometrium

Microsatellite instability (MSI) in human carcinoma DNA is a characteristic phenotype observed in hereditary non-polyposis colorectal cancer and also in some human sporadic cancers including multiple primary carcinomas. In this study, we analyzed mutations in the hCHK1, E2F4, hMSH3, and hMSH6 genes in MSI+ human cancers arising in colorectum, stomach and endometrium. The E2F4 and hMSH3 genes were mutated in all tumor types. Interestingly, the hMSH6 gene was mutated in colorectal and gastric cancers but not in endometrial cancer; this is similar to the TGFbetaRII gene. It is notable that the mutation status of the secondary mutators, hMSH3 and hMSH6, did not influence slippage-related frameshift mutations in genes harboring simple tandem-repeats, which suggests that the MSI phenotype may be affected mainly by abnormalities in the primary mutator genes, not by the secondary mutator genes. No mutations were observed in the cell cycle checkpoint gene hCHK1; mutations of this gene are thought to have a limited role, if any, in at least the tumor types analyzed in this study.

Mutational analysis of the CTNNB1 (beta-catenin) gene in human endometrial cancer: frequent mutations at codon 34 that cause nuclear accumulation

Recently, CTNNB1 (beta-catenin) has been found to function as an oncoprotein that works in the Wnt signaling pathway, and mutation of this gene has been reported in various human cancers. In this study, we analyzed 44 endometrial cancers and found somatic missense mutations in five (11%) tumors. Interestingly, four (80%) of the five tumors with mutations would cause amino acid alterations at residues next to Ser 33, one of the targets for phosphorylation of glycogen synthase kinase (GSK)-3beta. The tumors with mutations showed accumulation of the CTNNB1 protein in cytoplasm and nucleus. This is the first report of frequent somatic mutation of the CTNNB1 gene at codons adjacent to those encoding to Ser/Thr residues in endometrial cancer.

Expression of the DMBT1 gene is frequently suppressed in human lung cancer

DMBT1 (deleted in malignant brain tumors) is a candidate tumor suppressor gene that has been mapped to chromosome 10q25.3-q26.1, a region in which frequent loss of heterozygosity (LOH) has been observed in several human tumors. Since DMBT1 is highly expressed in the lung, we analyzed LOH at the DMBT1 locus and expression of this gene in lung cancer. Thirty-five (53%) of 66 primary lung cancers showed LOH, and diminished expression of DMBT1 was observed in 20 (91%) of 22 lung cancer cell lines: three (14%) of them showed loss of expression. We further determined the primary structure of DMBT1 and analyzed genetic alterations in this gene using 23 lung cancer cell lines. Two (9%) of them had homozygous deletion within the gene, and two cell lines had genetic aberrations: one was a rearrangement involving exons 5 and 6, and the other was a missense mutation at codon 52. These results suggest that inactivation of the DMBT1 gene plays an important role in human lung carcinogenesis.

Infrequent somatic mutations of the p73 gene in various human cancers

AIMS

It has already been reported that loss of heterozygosity (LOH) on chromosome 1p is frequent in a variety of human cancers. This finding implies the presence of some important tumour suppressor genes in this region. p73, a candidate tumour suppressor gene identified recently in chromosome band 1p36.33, encodes a protein highly homologous to p53. To investigate the role of the p73 gene in human carcinogenesis, we studied genetic alterations of this gene in various human cancers.

METHODS

We analysed the entire coding exons as well as their surrounding exon-intron boundaries of the p73 gene in 185 cases of various types of tumours (47 breast cancers, 43 colorectal cancers, 31 gastric cancers, 23 neuroblastomas, 21 lung cancer cell lines, and 20 pancreatic cancer cell lines); they are known as a group of tumours with frequent LOHs in the 1p region. PCR-SSCP analysis was performed and tumours in which aberrant migrating sized bands were observed were subjected to direct sequencing analyses.

RESULTS

Of the 185 cases, only one somatic mis-sense mutation of glutamine from arginine at codon 269 in exon 7 was found in one breast cancer. In addition, several polymorphisms were found at codons 137, 336, 349, and 610, as well as in introns 6, 8, and 9. Monoallelic expression was also observed in pancreatic cancer cell lines.

CONCLUSIONS

Our results suggest that inactivation of the p73 gene does not play a major role in the tumour types analysed in the present study.

Microsatellite instabilities in gastric cancer patients with multiple primary cancers

To answer whether microsatellite instability (MSI) can serve as a molecular marker for the risk-assessment of the development of multiple cancers, 26 tumors from 10 gastric cancer cases with multiple primary cancers were investigated. Six out of 10 cases revealed MSI in one or more cancer DNA. Significant statistical association was observed between MSI positive gastric cancer and cancer multiplicity (chi2 test, P<0.05). The complicated primary tumors in MSI-positive cases arose in colorectum, urogenital tract and ovary, which mimicked the tumor spectrum of hereditary non-polyposis colorectal cancer (HNPCC). On the other hand, most of the multiple cancers in MSI negative group were found synchronously and limited to the digestive organs. These observations suggest that MSI test on gastric cancer may be considered as a good marker for the assessment of multiple cancer development especially in the sites where tumors of HNPCC usually develop.

Frequent microsatellite instability and loss of heterozygosity in the region including BRCA1 (17q21) in young patients with gastric cancer

It is known that nearly 5% of gastric carcinomas arise under the age of 40. To elucidate genetic alterations in these patients, we performed studies using microsatellite assay in 27 gastric cancers under 35 years of age, composed of 5 well and 22 poorly differentiated adenocarcinomas. We detected replication errors (RERs) in 18 (67%) of 27 tumors, but no germline mutation in DNA mismatch repair genes (hMLH1 and hMSH2), except fory 3 somatic mutations in the hMLH1 gene. Loss of heterozygosity (LOH) at D17S855, located on chromosome 17q21 (BRCA1), was detected in 8 (40%) of 20 informative cases. In 12 (44%) of 27 cases, LOH on chromosome 17q12-21 including the BRCA1 was found in several neighboring markers in this region, while no mutation was found in the BRCA1 gene. Four (40%) of 10 scirrhous type gastric cancers exhibited wide allelic deletions on chromosome 17q12-21. These results overall suggest that young gastric cancer patients display highly frequent micro-satellite instability that might be due to defect of DNA repair system rather than hMLH1 and hMSH2. In addition, chromosome 17q12-21 including BRCA1 locus may contain a candidate for tumor suppressor gene, particularly in scirrhous type gastric cancers arising in young patients.

Altered microsatellites in incomplete-type intestinal metaplasia adjacent to primary gastric cancers

AIM

To investigate the presence of genetic instability in precancerous lesions of the stomach.

METHODS

Fifteen cases of sporadic gastric cancers with a background of intestinal metaplasia were studied by microsatellite assay at nine loci. Altered metaplastic mucosa was microdissected, reconstructed topographically, and examined immunohistochemically with an anti-p53 antibody, comparing its positive area with foci of microsatellite instability in each individual.

RESULTS

Alterations at one or more loci were observed in seven of 15 cancers (46.7%) and four of 15 intestinal metaplasias (26.7%). Two cases of replication error positive phenotype had no microsatellite alterations in their metaplastic mucosa. All the microsatellite alterations in the metaplastic mucosa were restricted to incomplete-type intestinal metaplasia around the respective cancers. Moreover, in one case, an identical pattern of microsatellite alteration was detected in the cancer tissue and in the adjacent metaplastic mucosa, suggesting the sequential development of gastric cancer from intestinal metaplasia. Frequent alteration was found at the locus D1S191 (1q), indicating that this locus might be altered early in the development of intestinal-type gastric cancer. No significant association between microsatellite instability and p53 immunoreactivity was observed in the cases examined.

CONCLUSION

These results indicate that microsatellite instability may be an early event in stomach carcinogenesis, especially in intestinal-type cancers.

Rapid and long-term effects of PTH(1-34) on growth plate chondrocytes are mediated through two different pathways in a cell-maturation-dependent manner

The aims of this study were to clarify the role of cell maturation stage on chondrocyte response to parathyroid hormone (PTH) by examining the effect of PTH(1-34) on alkaline-phosphatase-specific activity (ALPase) of chondrocyte cultures at two distinct stages of maturation, and to determine the signaling pathways used by the cells to mediate this effect. Confluent, fourth passage rat costochondral resting zone (RC) and growth zone (GC) chondrocytes were used. ALPase was measured in the cell layer, as well as in matrix vesicles (MV) and plasma membranes (PM), after the addition of 10(-7) 10(-11) mol/L bovine PTH(1-34), the active peptide, or bovine PTH(3-34), the inactive peptide, to the cultures. PTH(1-34) increased ALPase in the GC cultures at two separate times: between 5 and 180 min, with maximal stimulation at 10 min, and 36 to 48 h. In contrast, PTH(3-34) had no effect. At 10 min and 48 h, PTH(1-34) produced a dose-dependent increase in ALPase of both MV and PM isolated from GC cultures. Addition of forskolin and IBMX to increase cAMP increased ALPase in GC cultures to a level similar to that seen after addition of PTH(1-34). In contrast, the addition of PTH(1-34) to RC cells only increased ALPase between 5 and 60 min, with peak activity at 10 min. As with GC, PTH increased ALPase in both MV and PM. Moreover, the addition of PTH(3-34) or forskolin and IBMX had no effect on ALPase in RC. PTH(1-34) had no effect on GC protein kinase C (PKC) activity; however, the addition of PTH(1-34) to RC caused a dose-dependent increase in PKC activity. H8, an inhibitor of PKA, had no effect on PTH-stimulated ALPase in RC cells, but inhibited the PTH-dependent response in GC cells. In contrast, chelerythrine, an inhibitor of PKC activity, inhibited PTH-stimulated ALPase in RC cells, but had no effect on PTH-stimulated ALPase in GC cells. This study shows that the effect of PTH(1-34) on RC and GC cells is maturation dependent in terms of time course and mechanism. Whereas both cell types exhibit a rapid response to PTH, only GC cells show a long-term response. In GC, the effects of PTH are associated with changes in cAMP and may also involve at least one other pathway, whereas, in RC, the PTH effects appear to be associated with changes in PKC.

Expression of p21WAF1/CIP1 in colorectal adenomas and adenocarcinomas and its correlation with p53 protein expression

The expression of p53-inducible cyclin-dependent kinase inhibitor, p21WAF1/CIP1 in non-neoplastic mucosa, adenoma and adenocarcinoma of the colorectum was examined by immunohistochemistry and western blotting and its relation with the expression of p53 protein was analyzed. Non-neoplastic epithelial cells at the surface area showing no proliferative activity expressed p21WAF1/CIP1. The expression of p21WAF1/CIP1 was immunohistochemically detected in 55% (206/377) of the adenomas and 66% (190/289) of the adenocarcinomas, respectively. The incidence of strongly positive cases was significantly higher in the adenocarcinomas (27%) than in the adenomas (18%) (P < 0.05). The incidence of cases with strong p21WAF1/CIP1 expression was higher in stages 0, 1 and 2 carcinomas than in stages 3 and 4 carcinomas (P < 0.05). A decrease in the incidence of cases with strong expression was detected in carcinomas invading deeper than muscularis propria. The incidence of strongly positive cases was significantly lower in carcinomas with lymph node metastasis than those without metastasis (P < 0.05). The expression of p21 as well as p53 detected by western blotting was compatible with the results of immunohistochemistry in most cases examined. However, there was no significant correlation between the expression of p21WAF1/CIP1 and the abnormal accumulation of p53. These findings overall suggest that: (i) the physiological expression of p21WAF1/CIP1 may be associated with cellular senescence of colorectal mucosa; (ii) reduced expression of p21WAF1/CIP1 may participate in the progression of colorectal carcinoma; and (iii) p53-independent pathway may be considerably involved in the induction of p21WAF1/CIP1.

Reduced expression of cyclin-dependent kinase inhibitor p27Kip1 is associated with advanced stage and invasiveness of gastric carcinomas

Reduced expression of a cyclin-dependent kinase inhibitor p27Kip1 has recently been shown to predict poor survival of patients with breast and colorectal cancers. We studied the expression of p27Kip1 in gastric carcinomas by northern blotting, western blotting and immunohistochemistry to determine whether lack of p27 has implications for aggressiveness of gastric cancer. Reduced expression of p27 was detected in 40% of the gastric carcinomas at the mRNA level, while it was detected in 57% at the protein level. No gross alterations of the p27 gene were observed in any of the cases examined by Southern blot analysis. Immunohistochemical studies revealed that the expression of p27 was well preserved in most of the gastric adenomas, whereas it was so in only 26% of the gastric carcinomas. Fifty-six percent of the carcinomas showed almost no p27-positive cells. Decrease of p27-positive cells significantly correlated with advanced stage, depth of tumor invasion and lymph node metastasis. The expression of p27 showed an inverse correlation with the expression of cyclin E. These findings suggest that reduction of p27Kip1 protein may reflect the progression of gastric carcinomas and may be an indicator of high-grade malignancy.

Expression of cyclin-dependent kinase inhibitor p21WAF1/CIP1 in non-neoplastic mucosa and neoplasia of the stomach: relationship with p53 status and proliferative activity

The expression of the p53-inducible cyclin-dependent kinase inhibitor p21WAF1/CIP1 in non-neoplastic mucosa, adenoma, and adenocarcinoma of the stomach was examined immunohistochemically and its relationship with p53 expression and proliferative activity was analysed. In normal gastric mucosa as well as in intestinal metaplasia the epithelial cells at the surface which showed no proliferative activity expressed p21WAF1/CIP1, whereas the cells in the deep area of the glands expressing Ki-67 did not. In the neoplastic lesions, the expression of p21WAF1/CIP1 was detected in 78 per cent (112/144) of the adenomas and 76 per cent (262/343) of the adenocarcinomas. The incidence of p21WAF1/CIP1 expression did not differ among histological types of gastric carcinoma. The strong expression of p21WAF1/CIP1 was more frequently observed in carcinomas invading into submucosa or in cases of stages 2, 3, and 4 than in carcinomas limited to the mucosa or in stage 1 cases. The incidence of strongly positive cases was higher in carcinomas with lymph node metastasis than in those without metastasis. There was no apparent correlation between the expression of p21WAF1/CIP1 and the abnormal accumulation of p53 or with proliferative activity measured by Ki-67 expression. These findings overall suggest that p21WAF1/CIP1 might be associated with the senescence of non-neoplastic gastric epithelial cells; that a p53-independent pathway might be substantially involved in the induction of p21WAF1/CIP1 in gastric neoplasia; and that the proliferative activity of gastric cancer might not be solely dependent on control of the cell cycle by p21WAF1/CIP1.

Expression of cyclin E in colorectal adenomas and adenocarcinomas: correlation with expression of Ki-67 antigen and p53 protein

The expression of cyclin E in human colorectal adenomas and adenocarcinomas was examined immunohistochemically to elucidate the role of cyclin E in the colorectal carcinogenesis. The expression of cyclin E was detected in 25% (91/358) of the adenomas and 56% (149/267) of the adenocarcinomas. The incidence of strongly positive cases was significantly higher in the adenocarcinomas (20%) than in the adenomas (5%) (P < 0.01). Among adenomas, a significant correlation was noticed between the expression of cyclin E and the grade of atypia. The incidence of cyclin E expression was significantly higher in the adenocarcinomas without an adenoma component (62%; 104/169) than in those with this component (46%; 45/98) (P < 0.05). Furthermore, the incidence of the cyclin E expression was higher in stages 1 and 2 carcinoma than in stage 0 and stages 3 and 4 carcinoma. The expression of cyclin E was the most prominent in tumors invading the submucosa and muscularis propria. The expression of cyclin E was significantly correlated with the proliferative activity of the tumor cells measured by Ki-67 antigen expression (P < 0.01). It was also correlated with the expression of p53 protein in the tumor cells (P < 0.01). Overexpression of cyclin E and subsequent deregulation of cell cycle may contribute to the development and early progression of the colorectal carcinomas.

Molecular biological observations in gastric cancer

Alterations in the structure and function of oncogenes and tumor suppressor genes, as well as genetic instability at several other genetic foci may be responsible for stomach carcinogenesis. The particular combination of multiple gene changes found in gastric cancer differs depending on the two histological types, strongly indicating that different genetic pathways exist for well differentiated or intestinal type and poorly differentiated or diffuse type gastric cancers. In general, genetic instability, telomerase activity, CD44 abnormal transcripts, and p53 mutation, all of which are common events of two types of gastric cancer, may be involved mainly in the early stage of stomach carcinogenesis, whereas activation of oncogenes and overexpression of the epidermal growth factor-related growth factor system may chiefly confer progression on gastric cancer. A new strategy of molecular diagnosis of gastrointestinal cancer, which has been implemented as a routine service in the Hiroshima University Clinical Laboratory, may provide new opportunities for early cancer diagnosis and more accurate evaluation of prognosis or grade of malignancy.

Microsatellite instability in precancerous lesions and adenocarcinomas of the stomach

BACKGROUND

It is generally known that replication errors (RERs) at microsatellite loci detected in human malignancies reflect a genetic instability that is caused by abnormalities of DNA mismatch repair system and underlie human carcinogenesis. The authors analyzed RERs in precancerous lesions and adenocarcinomas of the stomach to learn when genetic instability occurs in stomach carcinogenesis. In addition, the authors examined genetic instability occurs in stomach carcinogenesis. In addition, the authors examined genetic alterations of the p53 and adenomatous polyposis coli (APC) genes to investigate the correlation between genetic instability and genetic alterations in these tumor suppressor genes.

METHODS

The authors examined microsatellite assay at 9 microsatellite loci in 24 sporadic gastric cancers, 12 gastric adenomas, and 9 intestinal metaplasia mucosae of the stomach from patients with gastric cancers using fresh frozen or formalin fixed and paraffin embedded samples paired with normal mucosae. They also screened loss of heterozygosity (LOH) of the p53 and APC genes by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

In total, the RER(+) phenotypes were observed in 8 of 24 (33%) gastric cancers, 5 of 12 (42%) gastric adenomas, and 3 of 9 (33%) intestinal metaplasia mucosae of the stomach. Histology, RERs were detected in 3 of 9 (33%) well differentiated adenocarcinomas, 2 of 11 (18%) poorly differentiated adenocarcinomas, and 3 of 4 (75%) scirrhous type gastric cancers respectively. Several cases showed RERs at many microsatellite loci simultaneously. Some RER(+) phenotypes had genetic alterations of the p53 or APC genes detected by LOH using PCR-RFLP analysis. However, no significant correlation was found between RER(+) phenotypes and LOH in these genes.

CONCLUSIONS

The frequency of RERs in detected gastric cancers were almost the same when compared with previously reported data. Interestingly, RERs were detected in greater than 30% of precancerous lesions, suggesting that genetic instability is an early somatic event of multistep stomach carcinogenesis. It also suggests that the adenoma-carcinoma sequence does exist in stomach carcinogenesis, especially in well differentiated adenocarcinomas. Moreover, alterations in the p53 and APC genes detected by PCR-RFLP analysis did not correlate with RER(+) phenotypes.