Mouse transient receptor potential melastatin 2 (TRPM2) isoform 7 attenuates full-length mouse TRPM2 activity through reductions in its expression by targeting it to ER-associated degradation.

Transient receptor potential melastatin 2 (TRPM2) assembles into tetramers to function as an oxidative stress-sensitive Ca2+ channel at the surface membrane. Limited information is currently available on the 10 protein isoforms of mouse TRPM2 (mTRPM2) identified. This study investigated whether these isoforms function as Ca2+ channels and examined their effects on full-length mTRPM2 activity using the HEK 293 cell exogenous expression system. Only full-length mTRPM2, isoform 1 localized to the surface membrane and was activated by oxidative stress. Isoform 7 was clearly recognized by protein quality control systems and degraded by endoplasmic reticulum-associated degradation after transmembrane proteolysis. In the co-expression system, the activation and expression of full-length mTRPM2 were attenuated by its co-expression with isoform 7, but not with the other isoforms. This decrease in the expression of full-length mTRPM2 was recovered by the proteasomal inhibitor. The present results suggest that isoforms other than isoform 1 did not function as oxidative stress-sensitive channels and also that only isoform 7 attenuated the activation of full-length mTRPM2 by targeting it to endoplasmic reticulum-associated degradation. The present study will provide important information on the functional nature of mTRPM2 isoforms for the elucidation of their roles in physiological and patho-physiological responses in vivo using mouse models.

Antitumor effects of pyrrole-imidazole polyamide modified with alkylating agent on prostate cancer cells.

Androgens and androgen receptor (AR) have a central role in prostate cancer progression by regulating its downstream signaling. Although androgen depletion therapy (ADT) is the primary treatment for most prostate cancers, they acquires resistance to ADT and become castration resistant prostate cancers (CRPC). AR complex formation with multiple transcription factors is important for enhancer activity and transcriptional regulation, which can contribute to cancer progression and resistance to ADT. We previously demonstrated that OCT1 collaborates with AR in prostate cancer, and that a pyrrole-imidazole (PI) polyamide (PIP) targeting OCT1 inhibits cell and castration-resistant tumor growth (Obinata D et al. Oncogene 2016). PIP can bind to DNA non-covalently without a drug delivery system unlike most DNA targeted therapeutics. In the present study, we developed a PIP modified with a DNA alkylating agent, chlorambucil (ChB) (OCT1-PIP-ChB). Then its effect on the growth of prostate cancer LNCaP, 22Rv1, and PC3 cells, pancreatic cancer BxPC3 cells, and colon cancer HCT116 cells, as well as non-cancerous MCF-10A epithelial cells, were analyzed. It was shown that the IC50s of OCT1-PIP-ChB for 22Rv1 and LNCaP were markedly lower compared to other cells, including non-cancerous MCF-10A cells. Comprehensive gene expression analysis of CRPC model 22Rv1 cells treated with IC50 concentrations of OCT1-PIP-ChB revealed that the gene group involved in DNA double-strand break repair was the most enriched among gene sets repressed by OCT1-PIP-ChB treatment. Importantly, in vivo study using 22Rv1 xenografts, we showed that OCT1-PIP-ChB significantly reduced tumor growth compared to the control group without showing obvious adverse effects. Thus, the PIP combined with ChB can exert a significant inhibitory effect on prostate cancer cell proliferation and castration-resistant tumor growth, suggesting a potential role as a therapeutic agent.

Identification of new octamer transcription factor 1-target genes upregulated in castration-resistant prostate cancer.

Octamer transcription factor 1 (OCT1) is an androgen receptor (AR)-interacting partner and regulates the expression of target genes in prostate cancer cells. However, the function of OCT1 in castration-resistant prostate cancer (CRPC) is not fully understood. In the present study, we used 22Rv1 cells as AR-positive CRPC model cells to analyze the role of OCT1 in CRPC. We showed that OCT1 knockdown suppressed cell proliferation and migration of 22Rv1 cells. Using microarray analysis, we identified four AR and OCT1-target genes, disks large-associated protein 5 (DLGAP5), kinesin family member 15 (KIF15), non-SMC condensin I complex subunit G (NCAPG), and NDC80 kinetochore complex component (NUF2) in 22Rv1 cells. We observed that knockdown of DLGAP5 and NUF2 suppresses growth and migration of 22Rv1 cells. Furthermore, immunohistochemical analysis showed that positive expression of DLGAP5 in prostate cancer specimens is related to poor cancer-specific survival rates of patients. Notably, enhanced expression of DLGAP5 was observed in CRPC tissues of patients. Thus, our findings suggest that these four genes regulated by the AR/OCT1 complex could have an important role in CRPC progression.

Short TRPM2 prevents the targeting of full-length TRPM2 to the surface transmembrane by hijacking to ER associated degradation.

Membrane proteins are targeted to the surface transmembrane after folding and assembling in the endoplasmic reticulum (ER). Misfolded- and unassembled-proteins are degraded by proteasomes following ubiquitination, termed ER-associated degradation (ERAD). Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive channel. One of the TRPM2 splicing variants, short TRPM2 (TRPM2-S) having only the N-terminus and first two transmembrane domains, was reported to prevent full-length TRPM2 (TRPM2-L) activation. Although TRPM2-S interacts with TRPM2-L, the inhibitory mechanisms of TRPM2-S are unclear. We found that TRPM2-S prevents transmembrane expression of TRPM2-L by targeting ERAD. TRPM2-S expression was lower than that of TRPM2-L, and was increased by an ERAD inhibitor. TRPM2-S was not expressed at the transmembrane. This suggests that TRPM2-S is a substrate for ERAD. Upon the simultaneous expression of TRPM2-S, the transmembrane expression of TRPM2-L was attenuated and the poly-ubiquitination of TRPM2-L was facilitated. Our study may clarify why TRPM2-S inhibits oxidative stress-induced TRPM2-L activation.

Protective Effects of Duloxetine against Cerebral Ischemia-Reperfusion Injury via Transient Receptor Potential Melastatin 2 Inhibition.

Activation of transient receptor potential melastatin 2 (TRPM2), an oxidative stress-sensitive Ca2+-permeable channel, contributes to the aggravation of cerebral ischemia-reperfusion (CIR) injury. Recent studies indicated that treatment with the antidepressant duloxetine for 24 hours (long term) attenuates TRPM2 activation in response to oxidative stress in neuronal cells. To examine the direct effects of antidepressants on TRPM2 activation, we examined their short-term (0-30 minutes) treatment effects on H2O2-induced TRPM2 activation in TRPM2-expressing human embryonic kidney 293 cells using the Ca2+ indicator fura-2. Duloxetine exerted the strongest inhibitory effects on TRPM2 activation among the seven antidepressants tested. These inhibitory effects appeared to be due to the inhibition of H2O2-induced TRPM2 activation via an open-channel blocking-like mechanism, because duloxetine reduced the sustained phase but not the initial phase of increases in intracellular Ca2+ concentrations. In a whole-cell patch-clamp study, duloxetine reduced the TRPM2-mediated inward current during the channel opening state. We also examined the effects of duloxetine in a mouse model of CIR injury. The administration of duloxetine to wild-type mice attenuated CIR injury, similar to that in Trpm2 knockout (KO) mice. The administration of duloxetine did not reduce CIR injury further in Trpm2 KO mice, suggesting that it exerts neuroprotective effects against CIR injury by inhibiting TRPM2 activation. Regarding drug repositioning, duloxetine may be a useful drug in reperfusion therapy for ischemic stroke because it has already been used clinically in therapeutics for several disorders, including depression.

Tyrphostin AG-related compounds attenuate H2O2-induced TRPM2-dependent and -independent cellular responses.

PURPOSE: TRPM2 is a Ca2+-permeable channel that is activated by H2O2. TRPM2-mediated Ca2+ signaling has been implicated in the aggravation of inflammatory diseases. Therefore, the development of TRPM2 inhibitors to prevent the aggravation of these diseases is expected. We recently reported that some Tyrphostin AG-related compounds inhibited the H2O2-induced activation of TRPM2 by scavenging the intracellular hydroxyl radical. In the present study, we examined the effects of AG-related compounds on H2O2-induced cellular responses in human monocytic U937 cells, which functionally express TRPM2. METHODS: The effects of AG-related compounds on H2O2-induced changes in intracellular Ca2+ concentrations, extracellular signal-regulated kinase (ERK) activation, and CXCL8 secretion were assessed using U937 cells. RESULTS: Ca2+ influxes via TRPM2 in response to H2O2 were blocked by AG-related compounds. AG-related compounds also inhibited the H2O2-induced activation of ERK, and subsequent secretion of CXCL8 mediated by TRPM2-dependent and -independent mechanisms. CONCLUSION: Our results show that AG-related compounds inhibit H2O2-induced CXCL8 secretion following ERK activation, which is mediated by TRPM2-dependent and -independent mechanisms in U937 cells. We previously reported that AG-related compounds blocked H2O2-induced TRPM2 activation by scavenging the hydroxyl radical. The inhibitory effects of AG-related compounds on TRPM2-independent responses may be due to scavenging of the hydroxyl radical.

Contribution of calumin to embryogenesis through participation in the endoplasmic reticulum-associated degradation activity.

Calumin is an endoplasmic reticulum (ER)-transmembrane protein, and little is known about its physiological roles. Here we showed that calumin homozygous mutant embryos die at embryonic days (E) 10.5-11.5. At mid-gestation, calumin was expressed predominantly in the yolk sac. Apoptosis was enhanced in calumin homozygous mutant yolk sacs at E9.5, pointing to a possible link to the embryonic lethality. Calumin co-immunoprecipitated with ERAD components such as p97, BIP, derlin-1, derlin-2 and VIMP, suggesting its involvement in ERAD. Indeed, calumin knockdown in HEK 293 cells resulted in ERAD being less efficient, as demonstrated by attenuation in both degradations of a misfolded α1-antitrypsin variant and the ER-to-cytosol dislocation of cholera toxin A1 subunit. In calumin homozygous mutant yolk sac endoderm cells, ER stress-associated alterations were observed, including lipid droplet accumulation, fragmentation of the ER and dissociation of ribosomes from the ER. In this context, the ER-overload response, assumed to be cytoprotective, was also triggered in the mutant endoderm cells, but seemed to fully counteract the excessive ER stress generated due to defective ERAD. Taken together, our findings suggested that calumin serves to maintain the yolk sac integrity through participation in the ERAD activity, contributing to embryonic development.

Prevention of aberrant protein aggregation by anchoring the molecular chaperone αB-crystallin to the endoplasmic reticulum.

The chaperone αB-crystallin (αBC) is a member of the small heat shock protein family and its point or truncated mutants cause the muscular disorder α-crystallinopathy. The illness is histologically characterized by accumulation of protein aggregates in muscle cells. Expression of the myopathy-causing R120G mutant of αBC, harboring an arginine-to-glycine mutation at position 120, results in aggregate formation. We demonstrated that tethering αBC to the endoplasmic reticulum (ER) membrane represses the protein aggregation mediated by the R120G mutant. ER-anchored αBC decreased the amount of the R120G mutant through autophagic proteolysis. In contrast, knockdown of ATG5, an E3 ligase essential for autophagy, in ER-anchored αBC-transfected cells restored the quantity of the R120G mutant. In this context, aggregate formation was still suppressed, indicating that ER-anchored αBC profoundly constrains aggregation competency of the R120G mutant separately from downregulating the abundance of the mutant. We have proposed that protein aggregation is prevented by manipulation of the ER microenvironment with αBC, and have shed light on a novel aspect of the ER as a therapeutic target.

TRIM50 protein regulates vesicular trafficking for acid secretion in gastric parietal cells.

Of the TRIM/RBCC family proteins taking part in a variety of cellular processes, TRIM50 is a stomach-specific member with no defined biological function. Our biochemical data demonstrated that TRIM50 is specifically expressed in gastric parietal cells and is predominantly localized in the tubulovesicular and canalicular membranes. In cultured cells ectopically expressing GFP-TRIM50, confocal microscopic imaging revealed dynamic movement of TRIM50-associated vesicles in a phosphoinositide 3-kinase-dependent manner. A protein overlay assay detected preferential binding of the PRY-SPRY domain from the TRIM50 C-terminal region to phosphatidylinositol species, suggesting that TRIM50 is involved in vesicular dynamics by sensing the phosphorylated state of phosphoinositol lipids. Trim50 knock-out mice retained normal histology in the gastric mucosa but exhibited impaired secretion of gastric acid. In response to histamine, Trim50 knock-out parietal cells generated deranged canaliculi, swollen microvilli lacking actin filaments, and excess multilamellar membrane complexes. Therefore, TRIM50 seems to play an essential role in tubulovesicular dynamics, promoting the formation of sophisticated canaliculi and microvilli during acid secretion in parietal cells.

TRPA1 underlies a sensing mechanism for O2.

Oxygen (O(2)) is a prerequisite for cellular respiration in aerobic organisms but also elicits toxicity. To understand how animals cope with the ambivalent physiological nature of O(2), it is critical to elucidate the molecular mechanisms responsible for O(2) sensing. Here our systematic evaluation of transient receptor potential (TRP) cation channels using reactive disulfides with different redox potentials reveals the capability of TRPA1 to sense O(2). O(2) sensing is based upon disparate processes: whereas prolyl hydroxylases (PHDs) exert O(2)-dependent inhibition on TRPA1 activity in normoxia, direct O(2) action overrides the inhibition via the prominent sensitivity of TRPA1 to cysteine-mediated oxidation in hyperoxia. Unexpectedly, TRPA1 is activated through relief from the same PHD-mediated inhibition in hypoxia. In mice, disruption of the Trpa1 gene abolishes hyperoxia- and hypoxia-induced cationic currents in vagal and sensory neurons and thereby impedes enhancement of in vivo vagal discharges induced by hyperoxia and hypoxia. The results suggest a new O(2)-sensing mechanism mediated by TRPA1.

Possible involvement of TRPM2 activation in 5-fluorouracil-induced myelosuppression in mice.

Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca2+-permeable channel. The activation of TRPM2 by H2O2 causes cell death in various types of cells. 5-Fluorouracil (5-FU) is an important anticancer drug, but myelosuppression is one of the most frequent adverse effects. The involvement of oxidative stress in 5-FU-induced myelosuppression has been reported, and bone marrow cells are known to express TRPM2. The aim of this study was to investigate whether TRPM2 is involved in 5-FU-induced myelosuppression. Enhancement of H2O2-induced intracellular Ca2+ concentration ([Ca2+]i) increase by 5-FU treatment was observed in human embryonic kidney 293 (HEK) cells stably expressing TRPM2 but not in HEK cells, indicating that 5-FU stimulates TRPM2 activation. In CD117 positive cells from wild type (WT) mouse bone marrow, 5-FU also enhanced the H2O2-induced [Ca2+]i increases, but not in cells from Trpm2 knockout (KO) mice. In the CFU-GM colony assay, the 5-FU-induced reduction of colony number was alleviated by Trpm2 deficiency. Moreover, the reduction of leukocytes in blood by administration with 5-FU in WT mice was also alleviated in Trpm2 KO mice. The activation of TRPM2 in bone marrow cells seems to be involved in 5-FU-induced myelosuppression.

Functional maintenance of calcium store by ShcB adaptor protein in cerebellar Purkinje cells.

Intracellular Ca2+ levels are changed by influx from extracellular medium and release from intracellular stores. In the central nervous systems, Ca2+ release is involved in various physiological events, such as neuronal excitability and transmitter release. Although stable Ca2+ release in response to stimulus is critical for proper functions of the nervous systems, regulatory mechanisms relating to Ca2+ release are not fully understood in central neurons. Here, we demonstrate that ShcB, an adaptor protein expressed in central neurons, has an essential role in functional maintenance of Ca2+ store in cerebellar Purkinje cells (PCs). ShcB-knockout (KO) mice showed defects in cerebellar-dependent motor function and long-term depression (LTD) at cerebellar synapse. The reduced LTD was accompanied with an impairment of intracellular Ca2+ release. Although the expression of Ca2+ release channels and morphology of Ca2+ store looked intact, content of intracellular Ca2+ store and activity of sarco/endoplasmic reticular Ca2+-ATPase (SERCA) were largely decreased in the ShcB-deficient cerebellum. Furthermore, when ShcB was ectopically expressed in the ShcB-KO PCs, the Ca2+ release and its SERCA-dependent component were restored. These data indicate that ShcB plays a key role in the functional maintenance of ER Ca2+ store in central neurons through regulation of SERCA activity.

Comparison of therapeutic effects between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas.

BACKGROUND: Although thermal ablation therapies have gained fairly wide acceptance as an effective treatment for small hepatocellular carcinoma (HCC), there have been only a few clinical studies comparing the response to radiofrequency ablation (RFA) and percutaneous microwave coagulation therapy (PMCT). We evaluated the therapeutic efficacy and safety of these two procedures for the treatment of small HCC measuring < or = 2 cm in diameter. METHODS: Thirty-four patients who had 37 nodules were treated by RFA and were compared with 49 patients (56 nodules) who underwent PMCT. Treatment was repeated until complete tumor necrosis was confirmed by contrast computed tomography (CT) scanning. The therapeutic efficacy and complications were retrospectively compared between the two procedures. RESULTS: (i) There were significantly fewer treatment sessions (P < 0.001) in the RFA group than in the PMCT group, but the necrotic area was significantly larger (P < 0.001) in the former group. (ii) The local recurrence rate was significantly lower (P = 0.031) after RFA than after PMCT, although the ectopic recurrence rate showed no significant difference. (iii) The cumulative survival rate was significantly higher (P = 0.018) after RFA than after PMCT. (iv) The incidence of pain and fever after treatment was significantly higher in the PMCT group. Bile duct injury, pleural effusion, and ascites were also significantly more common in the PMCT group. CONCLUSIONS: RFA is more useful than PMCT for the treatment of small HCC because it is minimally invasive and achieves a low local recurrence rate, high survival rate, and extensive necrosis after only a few treatment sessions.

Integrative Genomic Analysis of OCT1 Reveals Coordinated Regulation of Androgen Receptor in Advanced Prostate Cancer.

The ligand-dependent transcription factor androgen receptor (AR) plays a critical role in prostate cancer progression. We previously reported that Octamer transcription factor 1 (OCT1), an AR collaborative factor, facilitated the AR genomic bindings to regulate diverse programs of gene expression in AR-dependent prostate cancer cells. Repression of OCT1 binding can serve as a potential treatment strategy for advanced prostate cancer. However, the precise mechanism underlying the functions of OCT1 in advanced prostate cancer, especially lethal castration-resistant prostate cancer (CRPC), is still unclear. To uncover specific OCT1 functions in disease progression, we explored global OCT1-binding regions by performing chromatin immunoprecipitation sequencing in CRPC model 22Rv1 cells. We found that the OCT1 expression level and the obtained OCT1-binding regions increased in 22Rv1 cells compared with AR-dependent prostate cancer LNCaP cells. Interestingly, microarray analysis revealed that OCT1 regulates CRPC-specific target genes in addition to representative AR-regulated genes such as ACSL3. Pathway analysis showed the importance of OCT1 in regulating cell cycle‒related genes. By performing the chromatin immunoprecipitation assay, we validated anillin actin-binding protein (ANLN), which is highly expressed in CRPC and robustly regulated with OCT1 recruitment to the intron and promoter regions in 22Rv1 cells in comparison with LNCaP cells. Furthermore, knockdown of ANLN exhibited impaired cell growth and cell cycle progression, suggesting an important function of ANLN in CRPC cells. In conclusion, these findings raise the possibility that OCT1 coordinates AR signaling in a specific manner that is dependent on disease stage and promotes progression to CRPC.

Transient receptor potential channels in Alzheimer's disease.

Cognitive impairment and emotional disturbances in Alzheimer's disease (AD) result from the degeneration of synapses and neuronal death in the limbic system and associated regions of the cerebral cortex. An alteration in the proteolytic processing of the amyloid precursor protein (APP) results in increased production and accumulation of amyloid beta-peptide (Abeta) in the brain. Abeta can render neurons vulnerable to excitotoxicity and apoptosis by disruption of cellular Ca(2+) homeostasis and neurotoxic factors including reactive oxygen species (ROS), nitric oxide (NO), and cytokines. Many lines of evidence have suggested that transient receptor potential (TRP) channels consisting of six main subfamilies termed the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and TRPA (ankyrin) are involved in Ca(2+) homeostasis disruption. Thus, emerging evidence of the pathophysiological role of TRP channels has yielded promising candidates for molecular entities mediating Ca(2+) homeostasis disruption in AD. In this review, we focus on the TRP channels in AD and highlight some TRP "suspects" for which a role in AD can be anticipated. An understanding of the involvement of TRP channels in AD may lead to the development of new target therapies.

Robotic gait trainer in water: development of an underwater gait-training orthosis.

PURPOSE: To develop a robotic gait trainer that can be used in water (RGTW) and achieve repetitive physiological gait patterns to improve the movement dysfunctions. METHOD: The RGTW is a hip-knee-ankle-foot orthosis with pneumatic actuators; the control software was developed on the basis of the angular motions of the hip and knee joint of a healthy subject as he walked in water. Three-dimensional motions and electromyographic (EMG) activities were recorded in nine healthy subjects to evaluate the efficacy of using the RGTW while walking on a treadmill in water. RESULTS: The device could preserve the angular displacement patterns of the hip and knee and foot trajectories under all experimental conditions. The tibialis anterior EMG activities in the late swing phase and the biceps femoris throughout the stance phase were reduced whose joint torques were assisted by the RGTW while walking on a treadmill in water. CONCLUSION: Using the RGTW could expect not only the effect of the hydrotherapy but also the standard treadmill gait training, in particular, and may be particularly effective for treating individuals with hip joint movement dysfunction.

Characteristics of the gait adaptation process due to split-belt treadmill walking under a wide range of right-left speed ratios in humans.

The adaptability of human bipedal locomotion has been studied using split-belt treadmill walking. Most of previous studies utilized experimental protocol under remarkably different split ratios (e.g. 1:2, 1:3, or 1:4). While, there is limited research with regard to adaptive process under the small speed ratios. It is important to know the nature of adaptive process under ratio smaller than 1:2, because systematic evaluation of the gait adaptation under small to moderate split ratios would enable us to examine relative contribution of two forms of adaptation (reactive feedback and predictive feedforward control) on gait adaptation. We therefore examined a gait behavior due to on split-belt treadmill adaptation under five belt speed difference conditions (from 1:1.2 to 1:2). Gait parameters related to reactive control (stance time) showed quick adjustments immediately after imposing the split-belt walking in all five speed ratios. Meanwhile, parameters related to predictive control (step length and anterior force) showed a clear pattern of adaptation and subsequent aftereffects except for the 1:1.2 adaptation. Additionally, the 1:1.2 ratio was distinguished from other ratios by cluster analysis based on the relationship between the size of adaptation and the aftereffect. Our findings indicate that the reactive feedback control was involved in all the speed ratios tested and that the extent of reaction was proportionally dependent on the speed ratio of the split-belt. On the contrary, predictive feedforward control was necessary when the ratio of the split-belt was greater. These results enable us to consider how a given split-belt training condition would affect the relative contribution of the two strategies on gait adaptation, which must be considered when developing rehabilitation interventions for stroke patients.

Radiofrequency ablation versus percutaneous microwave coagulation therapy for small hepatocellular carcinomas: a retrospective comparative study.

BACKGROUND/AIMS: Although local ablation procedures are useful in eradication treatment for small hepatocellular carcinoma (HCC), there have only been a few clinical studies comparing the response to radiofrequency ablation (RFA) and percutaneous microwave coagulation therapy (PMCT). We evaluated the clinical effect and safety of these two procedures for the treatment of small HCCs measuring 2cm or less in diameter. METHODOLOGY: Twenty-four patients with HCC who were treated by RFA and were compared with 39 patients with HCC who underwent PMCT. These procedures were repeated until complete tumor necrosis was achieved. The therapeutic and adverse effects were retrospectively compared between the two procedures. RESULTS: (1) There were significantly fewer treatment sessions (P < 0.001) in the RFA group than the PMCT group, and the necrotic area was significantly larger (P < 0.001) in the former group. (2) The local recurrence rate was significantly lower (P = 0.012) after RFA than after PMCT, even though the ectopic recurrence rate showed no significant difference. 3) The cumulative survival rate was significantly higher (P = 0.028) in the RFA group. (4) The incidence of pain and fever after treatment was significantly higher after PMCT than after RFA. Bile duct injury and pleural effusion were also more frequent in the PMCT group. CONCLUSIONS: RFA is more useful than PMCT in the treatment of small HCCs because it is minimally invasive and achieves a low local recurrence rate, high survival rate, and extensive necrosis after only a few treatment sessions.

[Hepatocellular carcinoma occurring after 11 year-long sustained viral response to interferon therapy for chronic hepatitis C].

The patient was a 61-year-old man with chronic hepatitis C who achieved a sustained virological response to interferon therapy in 1993. As a result, the status of his liver improved pathologically from F2A2 to F1A1. Eleven years later, however, a tumor measuring 15 mm in diameter in segment 6 of the liver was indicated by CT. A well-differentiated hepatocellular carcinoma was detected by a fine needle biopsy. The lesion was treated by transcatheter arterial chemoembolization combined with radiofrequency ablation. Even if patients with chronic hepatitis C have achieved a sustained virological response to interferon therapy, patients with risk factors for the development of hepatocellular carcinoma, such as being a male of advanced age and with progressive fibrosis of the liver, should receive careful long-term follow-up.

[Pyogenic liver abscess complicated by gastric fistula and bacterial meningitis].

A 77-year-old woman was admitted suffering from fever and headache. On laboratory examination, bacterial meningitis and sepsis due to Klebsiella pneumoniae were diagnosed. In addition, a hepatic cystic lesion measuring 13 cm in diameter in the left lobe was indicated on diagnostic imaging. After treatment with antibiotics, her signs of infection improved and the hepatic lesion decreased in size. After discharge, however, the cystic liver mass increased and a gastric fistula developed. Hepatic and gastric resections were performed because of the possibility of biliary cystadenocarcinoma and gastric invasion. Pathologically, a pyogenic liver abscess complicated by gastric fistula was diagnosed.