EDIL3 is a novel regulator of epithelial-mesenchymal transition controlling early recurrence of hepatocellular carcinoma.

BACKGROUND & AIMS: Patients with advanced hepatocellular carcinoma (HCC) continue to have a dismal prognosis. Early recurrence, metastases and angiogenesis are the major obstacles to improve the outcome of HCC. Epithelial-mesenchymal transition (EMT) is a key contributor to cancer metastasis and recurrence, which are the major obstacles to improve prognosis of HCC. METHODS: Combining gene expression profiles of HCC samples with or without early recurrence and established cell lines with epithelial or mesenchymal phenotype, EDIL3 was identified as a novel regulator of EMT. The expression of EDIL3 was evaluated by quantitative PCR, Western blotting or immunohistochemistry. The effects of EDIL3 on the angiogenesis and metastasis of HCC cells were examined by wound healing, Matrigel invasion and tube formation assay in vitro and orthotopic xenograft mouse model of HCC in vivo. The signaling pathways of EDIL3 mediated were investigated through microarray and Western blotting analysis. RESULTS: EDIL3 was identified as a novel regulator of EMT, which contributes to angiogenesis, metastasis and recurrence of HCC. EDIL3 induces EMT and promotes HCC migration, invasion and angiogenesis in vitro. Mechanistically, overexpression of EDIL3, which was regulated by the downregulation of miR-137 in HCC, triggered the activation of ERK and TGF-ß signaling through interactions with αvß3 integrin. Blocking ERK and TGF-ß signaling overcomes EDIL3 induced angiogenesis and invasion. Using the orthotopic xenograft mouse model of HCC, we demonstrated that EDIL3 enhanced the tumorigenic, metastatic and angiogenesis potential of HCC in vivo. CONCLUSIONS: EDIL3-mediated activation of TGF-ß and ERK signaling could provide therapeutic implications for HCC.

MicroRNA-216a/217-induced epithelial-mesenchymal transition targets PTEN and SMAD7 to promote drug resistance and recurrence of liver cancer.

UNLABELLED: Tumor recurrence and metastases are the major obstacles to improving the prognosis of patients with hepatocellular carcinoma (HCC). To identify novel risk factors associated with HCC recurrence and metastases, we have established a panel of recurrence-associated microRNAs (miRNAs) by comparing miRNA expression in recurrent and nonrecurrent human HCC tissue samples using microarrays (recurrence is defined as recurrent disease occurring within a 2-year time point of the original treatment). Among the panel, expression of the miR-216a/217 cluster was consistently and significantly up-regulated in HCC tissue samples and cell lines associated with early tumor recurrence, poor disease-free survival, and an epithelial-mesenchymal transition (EMT) phenotype. Stable overexpression of miR-216a/217-induced EMT increased the stem-like cell population, migration, and metastatic ability of epithelial HCC cells. Phosphatase and tensin homolog (PTEN) and mothers against decapentaplegic homolog 7 (SMAD7) were subsequently identified as two functional targets of miR-216a/217, and both PTEN and SMAD7 were down-regulated in HCC. Ectopic expression of PTEN or SMAD7 partially rescued miR-216a/217-mediated EMT, cell migration, and stem-like properties of HCC cells. Previously, SMAD7 was shown to be a transforming growth factor beta (TGF-ß) type 1 receptor antagonist. Here, we further demonstrated that overexpression of miR-216a/217 acted as a positive feedback regulator for the TGF-ß pathway and the canonical pathway involved in the activation of phosphoinositide 3-kinase/protein kinase K (PI3K/Akt) signaling in HCC cells. Additionally, activation of the TGF-ß- and PI3K/Akt-signaling pathways in HCC cells resulted in an acquired resistance to sorafenib, whereas blocking activation of the TGF-ß pathway overcame miR-216a/217-induced sorafenib resistance and prevented tumor metastases in HCC. CONCLUSION: Overexpression of miR-216a/217 activates the PI3K/Akt and TGF-ß pathways by targeting PTEN and SMAD7, contributing to hepatocarcinogenesis and tumor recurrence in HCC.

Chemokine-driven lymphocyte infiltration: an early intratumoural event determining long-term survival in resectable hepatocellular carcinoma.

OBJECTIVE: Hepatocellular carcinoma (HCC) is a heterogeneous disease with poor prognosis and limited methods for predicting patient survival. The nature of the immune cells that infiltrate tumours is known to impact clinical outcome. However, the molecular events that regulate this infiltration require further understanding. Here the ability of immune genes expressed in the tumour microenvironment to predict disease progression was investigated. METHODS: Using quantitative PCR, the expression of 14 immune genes in resected tumour tissues from 57 Singaporean patients was analysed. The nearest-template prediction method was used to derive and test a prognostic signature from this training cohort. The signature was then validated in an independent cohort of 98 patients from Hong Kong and Zurich. Intratumoural components expressing these critical immune genes were identified by in situ labelling. Regulation of these genes was analysed in vitro using the HCC cell line SNU-182. RESULTS: The identified 14 immune-gene signature predicts patient survival in both the training cohort (p=0.0004 and HR=5.2) and the validation cohort (p=0.0051 and HR=2.5) irrespective of patient ethnicity and disease aetiology. Importantly, it predicts the survival of patients with early disease (stages I and II), for whom classical clinical parameters provide limited information. The lack of predictive power in late disease stages III and IV emphasises that a protective immune microenvironment has to be established early in order to impact disease progression significantly. This signature includes the chemokine genes CXCL10, CCL5 and CCL2, whose expression correlates with markers of T helper 1 (Th1), CD8(+) T and natural killer (NK) cells. Inflammatory cytokines (tumour necrosis factor α, interferon γ) and Toll-like receptor 3 ligands stimulate intratumoural production of these chemokines which drive tumour infiltration by T and NK cells, leading to enhanced cancer cell death. CONCLUSION: A 14 immune-gene signature, which identifies molecular cues driving tumour infiltration by lymphocytes, accurately predicts survival of patients with HCC especially in early disease.

Extending Surgical Resection for Hepatocellular Carcinoma Beyond Barcelona Clinic for Liver Cancer (BCLC) Stage A: A Novel Application of the Modified BCLC Staging System.

Objective: We aimed to prognosticate survival after surgical resection of HCC stratified by stage with amalgamation of the modified Barcelona Clinic Liver Cancer (BCLC) staging system and location of tumour. Methods: This single-institutional retrospective cohort study included patients with HCC who underwent surgical resection between 1st January 2000 to 30th June 2016. Participants were divided into 6 different subgroups: A-u) Within MC with Unilobar lesions; A-b) Within MC + Bilobar lesions; B1-u) Out of MC + within Up-To-7 + Unilobar lesions; B1-b) Out of MC + within Up-to-7 + Bilobar lesions; B2-u) Out of MC + Out of Up-To-7 + Unilobar lesions; B2-b) Out of MC + Out of Up-To-7 + Bilobar lesions. A separate survival analysis was conducted for solitary HCC lesions according to three subgroups: A-S (Within MC); B1-S (Out of MC + within Up-To-7); B2-S (Out of MC + out of Up-To-7). Results: A total of 794 of 1043 patients with surgical resection for HCC were analysed. Groups A-u (64.6%), A-b (58.4%) and B1-u (56.2%) had 5-year cumulative overall survival (OS) rates above 50% after surgical resection and median OS exceeding 60 months (P = 0.0001). The 5-year cumulative recurrence-free survival rates (RFS) were 40.4% (group A-u), 38.2% (group A-b), 36.3% (group B1-u), 24.6% (group B2-u), and 7.3% (group B2-b)(P=0.0001). For solitary lesions, the 5-year OS for the subgroups were A-S (65.1%), B1-S (56.0%) and B2-S (47.1%) (P = 0.0003). Compared to A-S, there was also a significant trend towards relatively poorer OS as the lesion sizes increased in B1-S (HR 1.46, 95% CI 1.03-2.08) and B2-S (HR 1.65, 95% CI 1.25-2.18). Conclusion: We adopted a novel approach combining the modified BCLC B sub-classification and dispersion of tumour to show that surgical resection in intermediate stage HCC can be robustly prognosticated. We found that size prognosticates resection outcomes in solitary tumours.

Modulation of iron-regulatory genes in human hepatocellular carcinoma and its physiological consequences.

Hepatocellular carcinoma (HCC) commonly develops in patients with underlying chronic liver disease. Additionally, the tumorous lesions of HCC patients are consistently characterized by the lack of iron accumulation even when arising in iron-loaded liver. However, the molecular mechanism leading to this observed phenomenon is currently poorly understood. In this study, all tumorous tissues from 24 HCC patients with chronic HBV infection were stained negative for iron when histologically assessed by Perls' Prussian blue stain, whereas excess iron deposits were present in 17 of the 24 adjacent non-tumorous liver tissues. To elucidate the concerted regulation of iron homeostasis in these patients, we studied the gene expression profiling of 42 relevant iron-regulatory genes in the tumorous and adjacent non-tumorous liver tissues of these HCC patients along with 10 normal liver controls. Expression for most of the iron-regulatory genes, including hepcidin, transferrin receptor 2 (TfR2), transferrin (Tf), ceruloplasmin (Cp) and iron regulatory protein 1 (IRP1), were significantly down-regulated in the tumorous tissues of these patients compared to the adjacent non-tumorous liver tissues and normal liver controls. On the other hand, expression of hepcidin, TfR2, ferroportin 1 and DMT1 were significantly up-regulated in iron-loaded non-cirrhotic non-tumorous liver tissues as compared with normal liver controls. Hence, the reduction of hepcidin expression within the iron-depleted tumorous lesions likely reflects the physiological consequence of the obligate demand for iron in the rapidly growing neoplastic cells, whereas the up-regulation of hepcidin expression in the iron-loaded adjacent non-tumorous liver tissues is likely a physiological response.

Circulating microRNAs as Potential Diagnostic and Prognostic Biomarkers in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common cancer with high mortality, due to late diagnosis and limited treatment options. Blood miRNAs, which circulate in a highly stable, cell-free form, show promise as novel potential biomarkers for early detection of HCC. Whole miRNome profiling was performed to identify deregulated miRNAs between HCC and normal healthy (NH) volunteers. These deregulated miRNAs were validated in an independent cohort of HCC, NH and chronic Hepatitis B (CHB) volunteers and finally in a 3rd cohort comprising NH, CHB, cirrhotic and HCC volunteers to evaluate miRNA changes during disease progression. The associations between circulating miRNAs and liver-damage markers, clinicopathological characteristics and survival outcomes were analysed to identify prognostic markers. Twelve miRNAs are differentially expressed between HCC and NH individuals in all three cohorts. Five upregulated miRNAs (miR-122-5p, miR-125b-5p, miR-885-5p, miR-100-5p and miR-148a-3p) in CHB, cirrhosis and HCC patients are potential biomarkers for CHB infection, while miR-34a-5p can be a biomarker for cirrhosis. Notably, four miRNAs (miR-1972, miR-193a-5p, miR-214-3p and miR-365a-3p) can distinguish HCC from other non-HCC individuals. Six miRNAs are potential prognostic markers for overall survival.

Identification and validation of a novel gene signature associated with the recurrence of human hepatocellular carcinoma.

PURPOSE: To improve the clinical management of human hepatocellular carcinoma (HCC) by accurate identification, at diagnosis, of patients at risk of recurrence after primary treatment for HCC. EXPERIMENTAL DESIGN: Two clinicopathologic variables available at diagnosis, vascular invasion and cirrhosis, together with molecular profiling using Affymetrix human HG-U133A and HG-U133B oligonucleotide probe arrays, were used to identify recurrent HCC disease. RESULTS: HCC patients presented clinically at diagnosis with vascular invasion and cirrhosis showed a high rate (78-83%) of developing recurrent disease within 6 to 35 months. In comparison, most of the HCC patients (80-100%) without vascular invasion and cirrhosis remained disease-free. However, the risk of recurrent disease for HCC patients with either vascular invasion or cirrhosis could not be accurately ascertained. Using a pool of 23 HCC patients with either vascular invasion or cirrhosis as training set, a 57-gene signature was derived and could predict recurrent disease at diagnosis, with 84% (sensitivity 86%, specificity 82%) accuracy, for a totally independent test set of 25 HCC patients with either vascular invasion or cirrhosis. On further analysis, the disease-free rate was significantly different between patients that were predicted to recur or not to recur in the test group (P = 0.002). CONCLUSION: We have presented data to show that by incorporating the status of vascular invasion and cirrhosis available at diagnosis for patients with HCC after partial curative hepatectomy and a novel 57-member gene signature, we could accurately stratify HCC patients with different risks of recurrence.

Infected pancreatic necrosis--an evaluation of the timing and technique of necrosectomy in a Southeast Asian population.

INTRODUCTION: Acute pancreatitis appears to be less prevalent in multi-ethnic Southeast Asia, where the aetiology also appears to be influenced by ethnicity. As with acute pancreatitis elsewhere, however, pancreatic necrosis is a cause of significant mortality and the aim of this study was to review our institutional experience with pancreatic necrosectomy. MATERIALS AND METHODS: The records of all patients who underwent pancreatic necrosectomy from January 2000 to December 2004 were analysed. Indications for surgery were the presence of infected necrosis, unresolving sepsis attributable to ongoing pancreatitis or the presence of gas in the pancreatic bed on imaging. Surgical debridement was achieved by debridement with closure over drains or by debridement with open packing. RESULTS: The cohort comprised 14 of 373 patients admitted for acute pancreatitis (3.8%), with an overall mortality rate of 29%. All patients had infected necrosis with positive bacteriological cultures. Eight patients (57%) underwent debridement with closure over drains and 6 patients (43%) underwent debridement with open packing. All mortalities occurred in patients who underwent open packing, who were also associated with a higher mean Acute Physiology and Chronic Health Evaluation (APACHE) II score. The mortality rate in patients who underwent debridement less than 4 weeks after admission was 33% (2 of 6), compared with 25% (2 of 8) in patients who underwent debridement after 4 weeks. There were no mortalities in patients operated on after 6 weeks. CONCLUSION: Surgical debridement with closure of drains and a policy of performing delayed necrosectomy are viable in our population.

Image-guided radiofrequency ablation of liver malignancies: experience at Singapore General Hospital.

UNLABELLED: The aim of this paper was to study the efficacy, side effects and complications of radiofrequency (RF) ablation of primary and metastatic liver malignancies. MATERIALS AND METHODS: We retrospectively reviewed 57 patients (39 men, 18 women; mean age, 63 years; age range, 44 to 83 years) who underwent RF ablation for liver malignancies from January 2002 to December 2004. A total of 87 tumours were ablated - 71 (81.6%) hepatocellular carcinomas and 16 (18.4%) metastases (from primaries in the colon, stomach and pancreas). RF ablation was performed either percutaneously (n = 71) under conscious sedation or intraoperatively (n = 16) under general anaesthesia. Follow-up ranged from 1 month to 41 months (mean, 15.2) and included computed tomography (CT) 1 day, 1 month and 3 months after ablation, and half-yearly thereafter. Patients were observed for local tumour progression and for the emergence of new tumours. RESULTS: Four patients with a total of 5 tumours were lost to follow-up. Of the remaining 82 tumours treated, complete ablation was attained in 66 tumours after a single procedure, giving a primary effectiveness rate of 80.5%. Seven (8.5%) required 2 procedures to achieve complete ablation, giving a secondary effectiveness rate of 89% after 2 ablations. One tumour (1.2%) required 3 procedures to achieve complete ablation. One tumour required 4 procedures to date, with the latest follow-up CT still demonstrating incomplete ablation. Two tumours (2.4%) had an initial RF ablation and subsequent transarterial chemoembolisation (TACE). One tumour had an initial RF ablation followed by 32Phosphorus-biosilicon (BrachySil) injection, the latter as part of a Phase IIA trial. One tumour required 2 RF ablations and a subsequent TACE. Lastly, 3 tumours received initial RF ablation but subsequent local tumour progression was not treated as the patients were deemed unfit for repeat ablation. No procedure-related deaths or major complications were encountered. Minor complications were reported in 2 patients (3.8%) - subcapsular haematoma and thermal injury to the adjacent gastric antrum, both not necessitating surgical intervention. CONCLUSIONS: RF ablation is an effective, safe and relatively simple procedure for the treatment of unresectable liver malignancies.

The over-expression of survivin enhances the chemotherapeutic efficacy of YM155 in human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related deaths worldwide. The inability of chemotherapeutic drugs to selectively target HCC tumor cells because of their predominant resistant phenotype to most conventional anticancer agents bestows a major obstacle for the clinical management of HCC. In this report, we have examined and demonstrated the remarkable heterogeneity of expression of survivin and its phosphorylated active form (p-survivin) in HCC patients' tissues and cell lines. Furthermore, the expression of survivin and p-survivin in HCC cell lines was found to be associated with response to the small-molecule survivin suppressant YM155. Therefore, in the HCC cell lines that express elevated level of survivin and p-survivin, YM155 efficiently inhibited their proliferation, induced cell cycle arrest and apoptosis resulting in DNA damage through the dysregulation of cell-cycle checkpoint-related regulatory genes. Importantly, YM155 yielded significantly better therapeutic effect than sorafenib when tested in an orthotopic mouse model using patient-derived HCC xenografts with elevated survivin and p-survivin expression. Our results clearly demonstrated that the level of survivin and p-survivin expression could serve as molecular predictive biomarkers to select potential YM155-responsive patients, in a move towards delivering precision medicine for HCC patients.

Results of resections for hepatocellular carcinoma in a new hepatobiliary unit.

BACKGROUND: Hepatocellular carcinoma (HCC) is the fourth commonest cancer in Singapore. Surgical resection offers the only chance of "cure". Resection tends to be difficult in HCC because of late presentation and concomitant liver cirrhosis. Specialized units with higher volume of operations are known to produce better results. The present review aims to evaluate early results with HCC resection and discuss the correlation between various tumour prognostic factors and the outcome. METHODS: The records of 81 consecutive hepatic resections for HCC in the hepatobiliary unit of the Department of General Surgery at the Singapore General Hospital from 1 January 1996 to 31 December 1998 were retrospectively reviewed. RESULTS: The mean age of the patients was 56.0 +/- 15.4 years. There were more men (M:F: 72:9) and Chinese patients (75 Chinese patients (92.6%); four Malay patients (4.9%); two Indian patients (2.5%)) affected by the disease. Hepatitis B and C carrier status were present in 67.1% (n = 51) and 3.9% (n = 1) of the patients, respectively. Forty-two patients (53.2%) had underlying liver cirrhosis. Twenty-eight patients (34.6%) underwent major hepatectomy and 53 (65.4%) underwent minor hepatectomies. Perioperative mortality was 4.9% (n = 4). The morbidity rate following hepatic resections was 28.4% (n = 23). The median follow up was 21 months (range: 1-52 months). The median survival was 43 months (95% confidence interval (CI): 34.6-51.4 months) after surgery and median time to recurrence was 9.6 months (range: 2-32 months). Overall survival was 79% and 59% at 1 and 3 years, respectively. Disease-free survival was 59% and 30% at 1 and 3 years, respectively. Advance pathological tumour, nodes, metastases (TNM) stage (III and IV), and presence of adjacent organ involvement were risk factors for early recurrence. Advance pathological TNM stage (III and IV) and blood loss of more than 2 L were poor prognostic factors for overall survival. CONCLUSION: The results of hepatectomies for HCC in the newly established unit at Singapore General Hospital have been shown to be comparable to other established specialized hepatobiliary units with similar perioperative mortality and morbidity rates.

MiR-214 targets ß-catenin pathway to suppress invasion, stem-like traits and recurrence of human hepatocellular carcinoma.

The down-regulation of miR-214 has previously been observed in human hepatocellular carcinoma (HCC). Here, we demonstrated the down-regulation of miR-214 is associated with cell invasion, stem-like traits and early recurrence of HCC. Firstly, we validated the suppression of miR-214 in human HCC by real-time quantitative RT-PCR (qRT-PCR) in 20 paired tumor and non-tumor liver tissues of HCC patients and 10 histologically normal liver tissues from colorectal cancer patients with liver metastases. Further qRT-PCR analysis of 50 HCC tissues from an independent cohort of HCC patients of whom 29 with early recurrent disease (<2 years) and 21 with late recurrent disease demonstrated that the suppression of miR-214 was significantly more suppressed in samples from HCC patients with early recurrent disease compared those from patients with no recurrence. Re-expression of miR-214 significantly suppressed the growth of HCC cells in vitro and reduced their tumorigenicity in vivo. The enhancer of zeste homologue 2 (EZH2) and ß-catenin (CTNNB1) was identified as two potential direct downstream targets of miR-214 through bioinformatics analysis and experimentally validated the miRNA-target interactions with a dual-firefly luciferase reporter assay. In corroborate with this, both EZH2 and CTNNB1 are found to be significantly overexpressed in human HCC biopsies. Since EZH2 can regulate CTNNB1, CTNNB1 can also be an indirect target of miR-214 through EZH2. Silencing EZH2 or CTNNB1 expression suppressed the growth and invasion of HCC cells and induced E-cadherin (CDH1), known to inhibit cell invasion and metastasis. Furthermore, the silencing of miR-214 or overexpression of EZH2 increased EpCAM(+) stem-like cells through the activation of CTNNB1. Interestingly, the up-regulation of EZH2, CTNNB1 and the down-regulation of CDH1 in HCC patients correlated with early recurrent disease and can be an independent predictor of poor survival. Therefore, miR-214 can directly or indirectly target CTNNB1 to modulate the ß-catenin signaling pathway in HCC.

Upregulation of Rac GTPase-activating protein 1 is significantly associated with the early recurrence of human hepatocellular carcinoma.

PURPOSE: To assess the significance of Rac GTPase-activating protein 1 (RACGAP1) expression in identifying HBV-positive human hepatocellular carcinoma (HCC) patients who are at high risk for recurrent disease. EXPERIMENTAL DESIGN: The prognostic significance of RACGAP1 was compared with clinicopathologic parameters available at diagnosis using multivariate and log-rank test. RACGAP1 expression and outcome in recurrence was compared between 35 patients with recurrence and 41 patients without recurrence using Kaplan-Meier analysis. RACGAP1-targeted molecules and pathways were identified and characterized by inhibition with siRNA duplexes. RESULTS: Kaplan-Meier analysis showed that the level of RACGAP1 expression is sufficient to predict the early recurrence of HCC: high RACGAP1 expression correlates with high risk of postresection recurrent HCC (P < 0.0005). Silencing of RACGAP1 in Hep3B and MHCC97-H HCC cells with high endogenous RACGAP1 expression inhibited cell migration and invasion. Using Ingenuity Pathway Analysis, the target molecules silenced in the RACGAP1 interactome were mostly genes related to the mitotic roles of the polo-like kinases. These included PRC1, AURKB, CDC2, ECT2, KIF23, PAK1, and PPP2R5E. In providing clinical corroboration of these results, when expression of these transcripts was analyzed in an expression database that we have established previously for HBV-positive HCC patients, these genes was mostly upregulated in patients who exhibited early recurrent disease and hence provided important corroboration of these results. CONCLUSIONS: siRNA-silencing RACGAP1 mainly targeted genes in an interactome clinically relevant to early HCC recurrence. Besides being an independent informative prognostic biomarker, RACGAP1 could also be a potential molecular target for designing therapeutic strategies for HCC.

Transcriptional down-regulation of IGFBP-3 in human hepatocellular carcinoma cells is mediated by the binding of TIA-1 to its AT-rich element in the 3'-untranslated region.

Insulin-like growth factor binding protein-3 (IGFBP-3) plays key roles in regulating cell growth, differentiation, and apoptosis in a variety of cellular systems. We have observed significant down-regulation of IGFBP-3 expression in primary human hepatocellular carcinoma (HCC) tissues when compared to adjacent histologically normal tissues. In this study, we functionally mapped the entire 3'-UTR of the IGFBP-3 mRNA, spanning 1471 nt and identified a 210 bp fragment consisting of AT-rich elements at the distal downstream region preceding the consensus pre-mRNA polyadenylation signal that provide high affinity binding for TIA-1 to mediate the specific suppression of IGFBP-3 expression in human HCC cells.

Cystic neoplasms of the pancreas: current diagnostic modalities and management.

Cystic neoplasm of the pancreas is a relatively uncommon condition covering a wide spectrum of pathology. The increasing incidence as a result of routine imaging tests in asymptomatic patients presents a diagnostic and therapeutic problem to the clinician. This paper discusses the role of the various investigative modalities in the management of cystic neoplasia of the pancreas.

Cloning and identification of hepatocellular carcinoma down-regulated mitochondrial carrier protein, a novel liver-specific uncoupling protein.

We report the identification of a novel cDNA fragment that shows significantly reduced expression in cancerous tissue compared with paired non-cancerous liver tissue in patients with hepatocellular carcinoma (HCC). The full-length transcript of 1733 bp encodes a protein of 308 amino acids that has all the hallmark features of mitochondrial carrier proteins. We designate the novel protein as HDMCP (HCC-down-regulated mitochondrial carrier protein). The HDMCP orthologs in human, mouse, and rat are found to exhibit close similarity in protein sequence and gene organization, as well as exclusive expression in the liver. Moreover, conserved syntenic regions have been demonstrated at the HDMCP gene locus in the human, mouse, and rat genome. Taken together, we suggest that HDMCP might have a conserved and unique biological function in the liver. Overexpression of HDMCP in transiently transfected cancer cells results in the loss of staining by MitoTracker dye, indicating that HDMCP could induce the dissipation of mitochondrial membrane potential (DeltaPsim). However, HDMCP-mediated disruption of DeltaPsim is not related to mitochondrial permeability transition or apoptosis. In addition, we further demonstrate that the dissipation of DeltaPsim is accompanied by significant reduction of cellular ATP in 293T cells overexpressing HDMCP or uncoupling protein 2 (UCP2). Our present findings suggest that HDMCP might be one of the long postulated uncoupling proteins that catalyze the physiological "proton leak" in the liver. The down-regulation of HDMCP in HCC cancer cells might result in the elevation of DeltaPsim, a common phenomenon found in cancer cells.