Toshikatsu Okumura

Natural History of Branch Duct Intraductal Papillary-Mucinous Neoplasms of the Pancreas without Mural Nodules: Long-term Follow-up Results

Background and aim: Although branch duct intraductal papillary-mucinous neoplasms (IPMNs) of the pancreas without mural nodules are frequently observed in asymptomatic subjects, the natural history of these lesions has never been studied. The aim of this study was to elucidate the natural history of branch duct IPMNs without mural nodules. Methods: Eighty-two patients who had no apparent mural nodules on initial examination were selected for follow-up. All subjects underwent examinations by imaging modalities including endoscopic retrograde pancreatography, and were followed-up by regular examinations once or twice a year. Serial changes of the maximum cystic diameter and the appearance of mural nodules were studied during the observation periods ranging from 14 to 148 months (median, 61 months). Results: Nine (11.0%) of 82 patients exhibited obvious progression of cystic dilatation (median, 59 months). Of these nine patients with cystic enlargement, six continued with regular follow-up examinations. Three cases underwent surgical resection, and were pathologically diagnosed as adenoma in two and borderline in one. Four patients (4.9%) showed newly developed mural nodules in dilated branch ducts (median, 105 months). Histological analysis revealed three cases classified as adenoma and one as carcinoma in situ. None of the remaining 69 patients (84.1%) showed any changes in dilated branch ducts (median, 57 months). Conclusions: Most branch duct IPMNs without mural nodules remained unchanged during long-term follow-up. Although follow-up with careful examination is required to detect newly developed mural nodules in dilated branch ducts, branch duct IPMNs without mural nodules can be followed-up without surgery.

Gemcitabine chemoresistance and molecular markers associated with gemcitabine transport and metabolism in human pancreatic cancer cells

To identify predictive molecular markers for gemcitabine resistance, we investigated changes in the expression of four genes associated with gemcitabine transport and metabolism during the development of acquired gemcitabine resistance of pancreatic cancer cell lines. The expression levels of human equilibrative nucleoside transporter-1 (hENT1), deoxycytidine kinase (dCK), RRM1, and RRM2 mRNA were analysed by real-time light cycler-PCR in various subclones during the development of acquired resistance to gemcitabine. Real-time light cycler-PCR demonstrated that the expression levels of either RRM1 or RRM2 progressively increased during the development of gemcitabine resistance. Expression of dCK was slightly increased in cells resistant to lower concentrations of gemcitabine, but was decreased below the undetectable level in higher concentration-resistant subclones. Expression of hENT1 was increased in the development of gemcitabine resistance. As acquired resistance to gemcitabine seems to correlate with the balance of these four factors, we calculated the ratio of hENT1 × dCK/RRM1 × RRM2 gene expression in gemcitabine-resistant subclones. The ratio of gene expression decreased progressively with development of acquired resistance in gemcitabine-resistant subclones. Furthermore, the expression ratio significantly correlated with gemcitabine sensitivity in eight pancreatic cancer cell lines, whereas no single gene expression level correlated with the sensitivity. These results suggest that the sensitivity of pancreatic cancer cells to gemcitabine is determined by the ratio of four factors involved in gemcitabine transport and metabolism. The ratio of the four gene expression levels correlates with acquired gemcitabine-resistance in pancreatic cancer cells, and may be useful as a predictive marker for the efficacy of gemcitabine therapy in pancreatic cancer patients.

Pancreatic ductal adenocarcinomas in long-term follow-up patients with branch duct intraductal papillary mucinous neoplasms.

Objective: Although branch duct intraductal papillary mucinous neoplasms (BD-IPMNs) are slow-growing tumors with a favorable prognosis, the synchronous occurrence of pancreatic ductal adenocarcinomas (PDAs) in patients with BD-IPMNs has been reported. This study was aimed to elucidate the development of PDAs in long-term follow-up patients with BD-IPMNs. Methods: We investigated 89 BD-IPMN patients who had no mural nodules and followed them up conservatively at least 2 years (median follow-up, 64 months; range, 25-158 months). All subjects underwent examinations by imaging modalities including endoscopic retrograde pancreatography. We calculated the standardized incidence ratio (SIR) from the vital statistics compiled by the Ministry of Health, Labor, and Welfare of Japan. Results: Among the 89 patients, 4 cases of PDAs distant from BD-IPMN were observed in 552 patient-years of follow-up (7.2 per 1000 patient-years). The expected number was 0.25, and the SIR of PDAs was 15.8 (95% confidence interval [CI], 4.3-40.4; P = 0.00014). Subgroup analyses showed that the incidence of PDAs was significantly increased in patients 70 years or older (SIR 16.7; 95% CI, 3.4-48.7; P = 0.0008) and in women (SIR 22.5; 95% CI, 2.7-81.1; P = 0.0037). Conclusions: Patients with BD-IPMNs are at a high risk for PDAs. During the follow-up, careful examination is required to detect the development of PDAs in patients with BD-IPMNs.Abbreviations: IPMN - intraductal papillary mucinous neoplasm, PDA - pancreatic ductal adenocarcinoma, ERCP - endoscopic retrograde cholangiopancreatography, MRCP - magnetic resonance cholangiopancreatography, EUS - endoscopic ultrasonography, CT - computed tomography, SIR - standardized incidence ratio

Orexinergic projections to the cat midbrain mediate alternation of emotional behavioural states from locomotion to cataplexy.

Orexinergic neurones in the perifornical lateral hypothalamus project to structures of the midbrain, including the substantia nigra and the mesopontine tegmentum. These areas contain the mesencephalic locomotor region (MLR), and the pedunculopontine and laterodorsal tegmental nuclei (PPN/LDT), which regulate atonia during rapid eye movement (REM) sleep. Deficiencies of the orexinergic system result in narcolepsy, suggesting that these projections are concerned with switching between locomotor movements and muscular atonia. The present study characterizes the role of these orexinergic projections to the midbrain. In decerebrate cats, injecting orexin‐A (60 μm to 1.0 mm, 0.20–0.25 μl) into the MLR reduced the intensity of the electrical stimulation required to induce locomotion on a treadmill (4 cats) or even elicit locomotor movements without electrical stimulation (2 cats). On the other hand, when orexin was injected into either the PPN (8 cats) or the substantia nigra pars reticulata (SNr, 4 cats), an increased stimulus intensity at the PPN was required to induce muscle atonia. The effects of orexin on the PPN and the SNr were reversed by subsequently injecting bicuculline (5 mm, 0.20–0.25 μl), a GABAA receptor antagonist, into the PPN. These findings indicate that excitatory orexinergic drive could maintain a higher level of locomotor activity by increasing the excitability of neurones in the MLR, while enhancing GABAergic effects on presumably cholinergic PPN neurones, to suppress muscle atonia. We conclude that orexinergic projections from the hypothalamus to the midbrain play an important role in regulating motor behaviour and controlling postural muscle tone and locomotor movements when awake and during sleep. Furthermore, as the excitability is attenuated in the absence of orexin, signals to the midbrain may induce locomotor behaviour when the orexinergic system functions normally but elicit atonia or narcolepsy when the orexinergic function is disturbed.

Serine/Threonine Kinase AKT Is Frequently Activated in Human Bile Duct Cancer and Is Associated with Increased Radioresistance

The prognosis for patients with bile duct cancer (BDC) remains poor. Although BDC cells are essentially radioresistant, recent reports have suggested that radiation therapy, in addition to its palliative role in the management of BDC, may improve patient survival. A better understanding of the mechanisms that lead to cellular radioresistance may assist in the development of more effective BDC therapies based on radiotherapy in combination with radiosensitizing agents. The serine/threonine kinase AKT/protein kinase B, a downstream effector of phosphatidylinositol 3′-kinase, is a well-characterized kinase that is known to play a critical role in antiapoptotic signaling pathways. In this investigation, we sought to clarify the role of AKT signaling in the radioresistance in BDC cells. First, to examine whether activated AKT is expressed in BDCs, tumor specimens were obtained from 19 consecutive BDC cases. Immunohistochemical staining using an anti-phosphorylated-AKT antibody showed that phosphorylated (activated) AKT was expressed in cancer cells but not in neighboring normal mucosa in 16 cases (84.2%). Next, to evaluate the role of AKT activation in the regulation of BDC cell radiosensitivity, clonogenic assays were performed using the phosphatidylinositol 3′-kinase inhibitor LY294002 with and without irradiation. LY294002 inhibited AKT activation in BDC cells and, on irradiation, decreased clonogenic survival in a radiation dose-dependent manner. Only a small decrease in cell viability was observed in cells exposed to LY294002. Expression of constitutively active AKT in BDC cells resulted in decreased radiosensitivity, whereas a dominant-negative AKT increased radiosensitivity. Furthermore, constitutively active AKT also inhibited radiation-induced apoptosis. Collectively, these results indicate that activated AKT in BDC cells is associated with radioresistance and suggest that pharmacological or genetic modulation of AKT activity may have important therapeutic implications in BDC patients treated with radiation.

Brainstem control of locomotion and muscle tone with special reference to the role of the mesopontine tegmentum and medullary reticulospinal systems

The lateral part of the mesopontine tegmentum contains functionally important structures involved in the control of posture and gait. Specifically, the mesencephalic locomotor region, which may consist of the cuneiform nucleus and pedunculopontine tegmental nucleus (PPN), occupies the interest with respect to the pathophysiology of posture-gait disorders. The purpose of this article is to review the mechanisms involved in the control of postural muscle tone and locomotion by the mesopontine tegmentum and the pontomedullary reticulospinal system. To make interpretation and discussion more robust, the above issue is considered largely based on our findings in the experiments using decerebrate cat preparations in addition to the results in animal experimentations and clinical investigations in other laboratories. Our investigations revealed the presence of functional topographical organizations with respect to the regulation of postural muscle tone and locomotion in both the mesopontine tegmentum and the pontomedullary reticulospinal system. These organizations were modified by neurotransmitter systems, particularly the cholinergic PPN projection to the pontine reticular formation. Because efferents from the forebrain structures as well as the cerebellum converge to the mesencephalic and pontomedullary reticular formation, changes in these organizations may be involved in the appropriate regulation of posture-gait synergy depending on the behavioral context. On the other hand, abnormal signals from the higher motor centers may produce dysfunction of the mesencephalic-reticulospinal system. Here we highlight the significance of elucidating the mechanisms of the mesencephalic-reticulospinal control of posture and locomotion so that thorough understanding of the pathophysiological mechanisms of posture-gait disorders can be made.

Inhibition of cell invasion and morphological change by troglitazone in human pancreatic cancer cells.

BackgroundWe have recently demonstrated that peroxisome proliferator activated receptor (PPAR) γ activation by its selective ligand, troglitazone, potently inhibited cell proliferation in human pancreatic cancer cells. The present study was performed to clarify the role of PPARγ in cell invasion/motility in human pancreatic cancer cells.MethodsCell invasive activity was assessed by an in vitro invasion assay, using a Transwell chamber, and by a wound-healing assay, in the human pancreatic cancer cell lines, PK-1 and PK-9. Cell morphology and actin structure were evaluated by phase-contrast and fluorescence microscopy.ResultsPPARγ activation by troglitazone inhibited cell invasion and cell migration in PK-1 and PK-9 cells. We also examined the effect of troglitazone on cell morphology and actin structure because of its effect on cell motility. The size of PK-1 and PK-9 cells that had been incubated with troglitazone became smaller, and the in shape changed from flat to spindle, followed by round. The troglitazone-induced cell rounding was reversible by replacement with troglitazone-free medium. Rhodamine-phalloidin staining revealed a decreased number of actin filaments in PK-1 cells treated with troglitazone. In cells treated with mycalolide B, an actin depolymerizing agent, troglitazone failed to induce cell rounding.ConclusionsThese results suggest that PPARγ activation by troglitazone inhibited cell motility and changed cell morphology through modulating actin organization.

Mechanisms by which thiazolidinediones induce anti-cancer effects in cancers in digestive organs

Increasing evidence suggests that thiazolidinediones (TZDs) could have a therapeutic potential for patients with cancers. Here, the evidence on the mechanisms by which TZDs could contribute to different steps of cancer biology in the digestive system is summarized. According to studies, TZDs induce anti-cancer actions through 3 main pathways: (1) cell growth arrest, (2) induction of apoptosis, and (3) inhibition of cell invasion. Cell growth arrest is induced by an increased level of p27Kip1. p27Kip1 accumulation results from the inhibition of the ubiquitin-proteasome system and/or inhibition of MEK–ERK signaling. TZDs induce apoptosis through increased levels of apoptotic molecules, such as p53 and PTEN and/or decreased level of anti-apoptotic molecules, such as Bcl-2 and survivin. Inhibition of MEK–ERK signaling-mediated up-regulation of E-cadherin and claudin-4, and/or decreased expression of matrix metalloproteinases (MMPs) such as MMP-2 and MMP-9, play a role in the TZD-induced inhibition of cancer cell invasion. Thus, TZDs are capable of inducing anti-tumor action in a variety of ways in gastrointestinal cancers.

Ramosetron Reduces Symptoms of Irritable Bowel Syndrome With Diarrhea and Improves Quality of Life in Women

BACKGROUND & AIMS Previous studies have indicated that serotonin-3-receptor antagonists might have a sex-specific effect in patients with irritable bowel syndrome with diarrhea (IBS-D). Alosetron has been approved for the treatment of only women, and ramosetron has been approved for the treatment for only men. We performed a randomized, placebo-controlled, phase 3 study to determine whether ramosetron reduces symptoms of IBS-D in women. METHODS We performed a prospective study of 576 female outpatients with IBS-D (according to the Rome III criteria), from February 2013 through February 2014, at 70 academic Gastroenterology Departments in Japan. After a 1-week baseline period, subjects received either 2.5 μg ramosetron (n = 292) or placebo (n = 284) once daily for 12 weeks. Primary end points were the monthly rates of response for relief from overall IBS symptoms and increased stool consistency at the last evaluation point. Quality of life (QOL) also was quantified. RESULTS A significantly higher proportion of patients given ramosetron reported global improvement (50.7%; 95% confidence interval [CI], 44.8-56.6) than patients given placebo (32.0%; 95% CI, 26.7-37.8)--a difference of 18.6% (95% CI, 10.7-26.5; P < .001). The relative risk was 1.58 (95% CI, 1.29-1.94) and the number needed to treat was 6 (95% CI, 4-10). A significantly higher proportion of patients in the ramosetron group reported increased stool consistency (40.8%; 95% CI, 35.1%-46.6%) than in the placebo group (24.3%; 95% CI, 19.4%-29.7%)--a difference of 16.5% (95% CI, 8.9%-24.0%; P < .001). Patients receiving ramosetron had significant reductions in abdominal pain and discomfort (P = .001) and greater improvement in QOL (P = .002) compared with placebo. Ramosetron induced constipation in 11.0% of patients. CONCLUSIONS In a randomized, placebo-controlled study of 576 women with IBS-D, 2.5 μg ramosetron per day reduced symptoms and increased stool consistency and QOL. Clinicaltrials.gov no: NCT01870895.

Role of orexin in central regulation of gastrointestinal functions

Orexins are neuropeptides that are localized in neurons within the lateral hypothalamus and regulate feeding behavior. The lateral hypothalamus plays an important role in not only feeding but also in the central regulation of gut function. Along this line, accumulating evidence has shown that orexins act in the central nervous system to regulate gastrointestinal functions. The purpose of this review is to summarize recent relevant findings on brain orexins and the digestive system, and discuss the pathophysiological roles of these peptides. Centrally administered orexin or endogenously released orexin in the brain potently stimulates gastric acid secretion in rats. The vagal cholinergic pathway is involved in the orexin-induced stimulation of acid secretion. Because of its stimulatory action on feeding, it can be hypothesized that orexin in the brain is a candidate mediator of cephalic phase gastric secretion. In addition, brain orexin may be involved in the development of depression and functional gastrointestinal disorders, which are frequently accompanied by inhibition of gut function, because lack of orexin activity might cause the inhibition of gastric physiological processes and evoke a depressive state. These lines of evidence suggest that orexin in the brain is a potential molecular target for treatment of functional gastrointestinal disorders.