gamma-Aminobutyric acid inhibits cholangiocarcinoma growth by cyclic AMP-dependent regulation of the protein kinase A/extracellular signal-regulated kinase 1/2 pathway

Oncogenic fatty acid oxidation senses circadian disruption in sleep-deficiency-enhanced tumorigenesis

Circadian disruption predicts poor cancer prognosis, yet how circadian disruption is sensed in sleep-deficiency (SD)-enhanced tumorigenesis remains obscure. Here, we show fatty acid oxidation (FAO) as a circadian sensor relaying from clock disruption to oncogenic metabolic signal in SD-enhanced lung tumorigenesis. Both unbiased transcriptomic and metabolomic analyses reveal that FAO senses SD-induced circadian disruption, as illustrated by continuously increased palmitoyl-coenzyme A (PA-CoA) catalyzed by long-chain fatty acyl-CoA synthetase 1 (ACSL1). Mechanistically, SD-dysregulated CLOCK hypertransactivates ACSL1 to produce PA-CoA, which facilitates CLOCK-Cys194 S-palmitoylation in a ZDHHC5-dependent manner. This positive transcription-palmitoylation feedback loop prevents ubiquitin-proteasomal degradation of CLOCK, causing FAO-sensed circadian disruption to maintain SD-enhanced cancer stemness. Intriguingly, timed β-endorphin resets rhythmic Clock and Acsl1 expression to alleviate SD-enhanced tumorigenesis. Sleep quality and serum β-endorphin are negatively associated with both cancer development and CLOCK/ACSL1 expression in patients with cancer, suggesting dawn-supplemented β-endorphin as a potential chronotherapeutic strategy for SD-related cancer.

Involvement of neuronal factors in tumor angiogenesis and the shaping of the cancer microenvironment

Emerging evidence suggests that nerves within the tumor microenvironment play a crucial role in regulating angiogenesis. Neurotransmitters and neuropeptides released by nerves can interact with nearby blood vessels and tumor cells, influencing their behavior and modulating the angiogenic response. Moreover, nerve-derived signals may activate signaling pathways that enhance the production of pro-angiogenic factors within the tumor microenvironment, further supporting blood vessel growth around tumors. The intricate network of communication between neural constituents and the vascular system accentuates the potential of therapeutically targeting neural-mediated pathways as an innovative strategy to modulate tumor angiogenesis and, consequently, neoplastic proliferation. Hereby, we review studies that evaluate the precise molecular interplay and the potential clinical ramifications of manipulating neural elements for the purpose of anti-angiogenic therapeutics within the scope of cancer treatment.

Exogenous γ-Aminobutyric Acid (GABA) Enhanced Response to Abiotic Stress in Hypsizygus marmoreus by Improving Mycelial Growth and Antioxidant Capacity

γ-Aminobutyric (GABA) acid is a nutrient and signaling molecule existing in many plants, participating in the regulation of metabolism and various physiological activities. Two strains of Hypsizygus marmoreus (a white variety and a brown variety) were investigated to study the impact of exogenous GABA on mycelial growth and the response to stress. Mycelial growth, microscopic morphology, antioxidant profile, and gad2 expression in H. marmoreu were investigated under salt, dehydration, or cold stress. The results indicated that 5 mM GABA stimulated mycelial growth under standard cultivation conditions, whereas GABA addition over 10 mM hindered the growth. Under salt, dehydration, or cold stress, treatment with 5 mM GABA significantly enhanced the mycelial growth rate and density of both H. marmoreus strains by promoting front hyphae branching. Meanwhile, the activities of key antioxidant enzymes such as peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were enhanced by GABA, thereby augmenting the defensive network against abiotic stress. Additionally, gad2 expression and GABA concentration were increased under abiotic stresses as a resistance regulation response. The exogenous addition of GABA strengthened the upregulation of gad2 expression and GABA production. These findings indicated that exogenously adding low concentrations of GABA effectively enhanced the mycelial growth and antioxidant profile of H. marmoreus, thereby improving its resistance against stresses.

GABBR2 as a Downstream Effector of the Androgen Receptor Induces Cisplatin Resistance in Bladder Cancer

The precise molecular mechanisms responsible for resistance to cisplatin-based chemotherapy in patients with bladder cancer remain elusive, while we have indicated that androgen receptor (AR) activity in urothelial cancer is associated with its sensitivity. Our DNA microarray analysis in control vs. AR-knockdown bladder cancer sublines suggested that the expression of a GABA B receptor GABBR2 and AR was correlated. The present study aimed to determine the functional role of GABBR2 in modulating cisplatin sensitivity in bladder cancer. AR knockdown and dihydrotestosterone treatment considerably reduced and induced, respectively, GABBR2 expression, and the effect of dihydrotestosterone was at least partially restored by an antiandrogen hydroxyflutamide. A chromatin immunoprecipitation assay further revealed the binding of AR to the promoter region of GABBR2 in bladder cancer cells. Meanwhile, GABBR2 expression was significantly elevated in a cisplatin-resistant bladder cancer subline, compared with control cells. In AR-positive bladder cancer cells, knockdown of GABBR2 or treatment with a selective GABA B receptor antagonist, CGP46381, considerably enhanced the cytotoxic activity of cisplatin. However, no additional effect of CGP46381 on cisplatin-induced growth suppression was seen in GABBR2-knockdown cells. Moreover, in the absence of cisplatin, CGP46381 treatment and GABBR2 knockdown showed no significant changes in cell proliferation or migration. These findings suggest that GABBR2 represents a key downstream effector of AR signaling in inducing resistance to cisplatin treatment. Accordingly, inhibition of GABBR2 has the potential of being a means of chemosensitization, especially in patients with AR/GABBR2-positive bladder cancer.

γ-aminobutyric acid B2 receptor: A potential therapeutic target for cholangiocarcinoma in patients with diabetes mellitus

BACKGROUND

The association between diabetes mellitus (DM) and the increased risk and progression of cholangiocarcinoma (CCA) has been reported with unclear underlying mechanisms. Previous studies showed that γ-aminobutyric acid (GABA) B2 receptor (GABBR2) was upregulated in CCA cells cultured in high glucose (HG) conditions. Roles of GABA receptors in CCA progression have also been studied, but their association with DM and hyperglycemia in CCA remains unclarified.

AIM

To investigate the effects of hyperglycemia on GABBR2 expression and the potential use of GABBR2 as a CCA therapeutic target.

METHODS

CCA cells, KKU-055 and KKU-213A, were cultured in Dulbecco Modified Eagle's Medium supplemented with 5.6 mmol/L (normal glucose, NG) or 25 mmol/L (HG) glucose and assigned as NG and HG cells, respectively. GABBR2 expression in NG and HG cells was investigated using real-time quantitative polymerase chain reaction and western blot. Expression and localization of GABBR2 in CCA cells were determined using immunocytofluorescence. GABBR2 expression in tumor tissues from CCA patients with and without DM was studied using immunohistochemistry, and the correlations of GABBR2 with the clinicopathological characteristics of patients were analyzed using univariate analysis. Effects of baclofen, a GABA-B receptor agonist, on CCA cell proliferation and clonogenicity were tested using the MTT and clonogenic assays. Phospho-kinases arrays were used to screen the affected signaling pathways after baclofen treatment, and the candidate signaling molecules were validated using the public transcriptomic data and western blot.

RESULTS

GABBR2 expression in CCA cells was induced by HG in a dose- and time-dependent manner. CCA tissues from patients with DM and hyperglycemia also showed a significantly higher GABBR2 expression compared with tumor tissues from those with euglycemia (P < 0.01). High GABBR2 expression was significantly associated with a poorer non-papillary histological subtype but with smaller sizes of CCA tumors (P < 0.05). HG cells of both tested CCA cell lines were more sensitive to baclofen treatment. Baclofen significantly suppressed the proliferation and clonogenicity of CCA cells in both NG and HG conditions (P < 0.05). Phospho-kinase arrays suggested glycogen synthase kinase 3 (GSK3), β-catenin, and the signal transducer and activator of transcription 3 (STAT3) as candidate signaling molecules under the regulation of GABBR2, which were verified in NG and HG cells of the individual CCA cell lines. Cyclin D1 and c-Myc, the common downstream targets of GSK3/β-catenin and STAT3 involving cell proliferation, were accordingly downregulated after baclofen treatment.

CONCLUSION

GABBR2 is upregulated by HG and holds a promising role as a therapeutic target for CCA regardless of the glucose condition.

Criteria for preclinical models of cholangiocarcinoma: scientific and medical relevance

Cholangiocarcinoma (CCA) is a rare malignancy that develops at any point along the biliary tree. CCA has a poor prognosis, its clinical management remains challenging, and effective treatments are lacking. Therefore, preclinical research is of pivotal importance and necessary to acquire a deeper understanding of CCA and improve therapeutic outcomes. Preclinical research involves developing and managing complementary experimental models, from in vitro assays using primary cells or cell lines cultured in 2D or 3D to in vivo models with engrafted material, chemically induced CCA or genetically engineered models. All are valuable tools with well-defined advantages and limitations. The choice of a preclinical model is guided by the question(s) to be addressed; ideally, results should be recapitulated in independent approaches. In this Consensus Statement, a task force of 45 experts in CCA molecular and cellular biology and clinicians, including pathologists, from ten countries provides recommendations on the minimal criteria for preclinical models to provide a uniform approach. These recommendations are based on two rounds of questionnaires completed by 35 (first round) and 45 (second round) experts to reach a consensus with 13 statements. An agreement was defined when at least 90% of the participants voting anonymously agreed with a statement. The ultimate goal was to transfer basic laboratory research to the clinics through increased disease understanding and to develop clinical biomarkers and innovative therapies for patients with CCA.

GABAB1e promotes the malignancy of human cancer cells by targeting the tyrosine phosphatase PTPN12

Neurotransmitter receptors are involved in cancer progression. Among them, the heterodimeric GABA_B receptor, activated by the main inhibitory neurotransmitter GABA, is composed of the transmembrane GABA_B1 and GABA_B2 subunits. The oncogenic role of the isoform GABA_B1e (GB_1e) containing only the extracellular domain of GABA_B1 remains unclear. We revealed that GB_1e is largely expressed in human breast cancer (BrCa) cell lines as well as in BrCa tissues where it is upregulated. Moreover, GB_1e promoted the malignancy of BrCa cells both in vitro and in vivo. We propose that GB_1e favors EGFR signaling by interacting with PTPN12 to disrupt the interaction between EGFR and PTPN12, and phosphorylation of Y230 and Y404 on GB_1e is required in this process. Our data highlight that the GABBR1 gene through the expression of the GB_1e isoform might play an important oncogenic role in BrCa and that GB_1e is of interest for the treatment of some cancers.

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GABA_B1e promotes the malignancy of breast cancer cells both in vitro and in vivo

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Specific phosphorylation of GABA_B1e is critical for its association with PTPN12

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GABA_B1e disrupts EGFR interacting with PTPN12 and induces EGFR-PI3K/Akt signaling

Cyclic AMP Signaling in Biliary Proliferation: A Possible Target for Cholangiocarcinoma Treatment?

Cholangiocarcinoma is a lethal disease with scarce response to current systemic therapy. The rare occurrence and large heterogeneity of this cancer, together with poor knowledge of its molecular mechanisms, are elements contributing to the difficulties in finding an appropriate cure. Cholangiocytes (and their cellular precursors) are considered the liver component giving rise to cholangiocarcinoma. These cells respond to several hormones, neuropeptides and molecular stimuli employing the cAMP/PKA system for the translation of messages in the intracellular space. For instance, in physiological conditions, stimulation of the secretin receptor determines an increase of intracellular levels of cAMP, thus activating a series of molecular events, finally determining in bicarbonate-enriched choleresis. However, activation of the same receptor during cholangiocytes’ injury promotes cellular growth again, using cAMP as the second messenger. Since several scientific pieces of evidence link cAMP signaling system to cholangiocytes’ proliferation, the possible changes of this pathway during cancer growth also seem relevant. In this review, we summarize the current findings regarding the cAMP pathway and its role in biliary normal and neoplastic cell proliferation. Perspectives for targeting the cAMP machinery in cholangiocarcinoma therapy are also discussed.

The Aging GABAergic System and Its Nutritional Support

Aging is associated with a decline in hormones and an associated decline in GABAergic function and calcium and ion current dysregulation. Neurosteroid hormones act as direct calcium channel blockers, or they can act indirectly on calcium channels through their interaction with GABA receptors. The calcium channel dysfunction associated with hormone loss further leads to an excitatory cell state, which can ultimately lead to cell death. The calcium theory of aging posits that cellular mechanisms, which maintain the homeostasis of cytosol Ca2+ concentration, play a key role in brain aging and that sustained changes in Ca2+ homeostasis provide the final common pathway for age-associated brain changes. There is a link between hormone loss and calcium dysregulation. Loss of calcium regulation associated with aging can lead to an excitatory cell state, primarily in the mitochondria and nerve cells, which can ultimately lead to cell death if not kept in check. A decline in GABAergic function can also be specifically tied to declines in progesterone, allopregnanolone, and DHEA levels associated with aging. This decline in GABAergic function associated with hormone loss ultimately affects GABAergic inhibition or excitement and calcium regulation throughout the body. In addition, declines in GABAergic function can also be tied to vitamin status and to toxic chemicals in the food supply. The decline in GABAergic function associated with aging has an effect on just about every body organ system. Nutritional support of the GABAergic system with supportive foods, vitamins, and GABA or similar GABA receptor ligands may address some of the GABAergic dysfunction associated with aging.

Evolution of the Experimental Models of Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a rare, aggressive disease with poor overall survival. In advanced cases, surgery is often not possible or fails; in addition, there is a lack of effective and specific therapies. Multidisciplinary approaches and advanced technologies have improved the knowledge of CCA molecular pathogenesis, highlighting its extreme heterogeneity and high frequency of genetic and molecular aberrations. Effective preclinical models, therefore, should be based on a comparable level of complexity. In the past years, there has been a consistent increase in the number of available CCA models. The exploitation of even more complex CCA models is rising. Examples are the use of CRISPR/Cas9 or stabilized organoids for in vitro studies, as well as patient-derived xenografts or transgenic mouse models for in vivo applications. Here, we examine the available preclinical CCA models exploited to investigate: (i) carcinogenesis processes from initiation to progression; and (ii) tools for personalized therapy and innovative therapeutic approaches, including chemotherapy and immune/targeted therapies. For each model, we describe the potential applications, highlighting both its advantages and limits.

In Vivo Models for Cholangiocarcinoma-What Can We Learn for Human Disease?

Cholangiocarcinoma (CCA) comprises a heterogeneous group of primary liver tumors. They emerge from different hepatic (progenitor) cell populations, typically via sporadic mutations. Chronic biliary inflammation, as seen in primary sclerosing cholangitis (PSC), may trigger CCA development. Although several efforts were made in the last decade to better understand the complex processes of biliary carcinogenesis, it was only recently that new therapeutic advances have been achieved. Animal models are a crucial bridge between in vitro findings on molecular or genetic alterations, pathophysiological understanding, and new therapeutic strategies for the clinic. Nevertheless, it is inherently difficult to recapitulate simultaneously the stromal microenvironment (e.g., immune-competent cells, cholestasis, inflammation, PSC-like changes, fibrosis) and the tumor biology (e.g., mutational burden, local growth, and metastatic spread) in an animal model, so that it would reflect the full clinical reality of CCA. In this review, we highlight available data on animal models for CCA. We discuss if and how these models reflect human disease and whether they can serve as a tool for understanding the pathogenesis, or for predicting a treatment response in patients. In addition, open issues for future developments will be discussed.

A novel heterozygous mutation in the HMBS gene in a patient with acute intermittent porphyria and posterior reversible encephalopathy syndrome

Acute intermittent porphyria (AIP) is a rare inherited disorder, which is caused by the partial deficiency of hydroxymethylbilane synthase (HMBS), an enzyme of the heme biosynthetic pathway. Abdominal pain, neuropsychiatric disturbance and neuropathy are the typical manifestations of the disease. Complications such as posterior reversible encephalopathy syndrome (PRES), a rare type of brain lesion present on MRI, are also observed in patients with AIP. The present study reports on the case of a 36‑year‑old Chinese female patient with AIP and PRES. Genomic DNA were obtained from peripheral blood leukocytes and genomic regions of the HMBS gene were amplified as 2 fragments, which together contained all the exons and flanking intronic regions. Sanger sequencing of the amplified DNA fragments from the patient and the patient's family revealed a novel frameshift deletion (c.405‑406delAA) in exon 8 of the HMBS gene. This mutation leads to a subsequent truncated protein (p.Glu135AspfsX74). The recombinant mutant protein had 62% activity relative to the wild‑type protein but similar thermostability. It was confirmed that this novel mutation was the cause of AIP. Accumulation of D‑aminolevulinic acid (ALA) due to HMBS dysfunction is a potential mechanism of PRES. The manifestation of PRES may be associated with ALA‑induced cytotoxicity and the destruction of the blood‑brain barrier. In summary, in the present study, a novel pathogenic HMBS mutation was identified, expanding on the molecular heterogeneity of AIP.

Profiling of how nociceptor neurons detect danger - new and old foes

The host evolves redundant mechanisms to preserve physiological processing and homeostasis. These functions range from sensing internal and external threats, creating a memory of the insult and generating reflexes, which aim to resolve inflammation. Impairment in such functioning leads to chronic inflammatory diseases. By interacting through a common language of ligands and receptors, the immune and sensory nervous systems work in concert to accomplish such protective functions. Whilst this bidirectional communication helps to protect from danger, it can contribute to disease pathophysiology. Thus, the somatosensory nervous system is anatomically positioned within primary and secondary lymphoid tissues and mucosa to modulate immunity directly. Upstream of this interplay, neurons detect danger, which prompts the release of neuropeptides initiating (i) defensive reflexes (ranging from withdrawal response to coughing) and (ii) chemotaxis, adhesion and local infiltration of immune cells. The resulting outcome of such neuro-immune interplay is still ill-defined, but consensual findings start to emerge and support neuropeptides not only as blockers of T_H 1-mediated immunity but also as drivers of T_H 2 immune responses. However, the modalities detected by nociceptors revealed broader than mechanical pressure and temperature sensing and include signals as various as cytokines and pathogens to immunoglobulins and even microRNAs. Along these lines, we aggregated various dorsal root ganglion sensory neuron expression profiling datasets supporting such wide-ranging sensing capabilities to help identifying new danger detection modalities of these cells. Thus, revealing unexpected aspects of nociceptor neuron biology might prompt the identification of novel drivers of immunity, means to resolve inflammation and strategies to safeguard homeostasis.

Neuroendocrine regulation of cholangiocarcinoma: A status quo review

Increasing studies have demonstrated that neuroendocrine system is involved in the development and progression of cholangiocarcinoma. The neuroendocrine hormones, neurotransmitters and neuropeptides regulate cholangiocarcinoma via affecting pathophysiology of tumor cells. The developing interaction and interplay between neuroendocrine-associated factors and tumor cells provide novel insights into neural control of tumorigenesis and reveal potential therapeutic effect on patients with cholangiocarcinoma. Herein we reviewed the latest findings and achievements which demonstrate the close interactions between neuroendocrine regulation and progression of cholangiocarcinoma. Also, future therapeutic approaches targeting neuroendocrine-associated factors are discussed which may help improve management and treatment of cholangiocarcinoma.

Animal models of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary tract malignancy with a poor overall prognosis. There is a critical need to develop effective targeted therapies for the treatment of this lethal disease. In an effort to address this challenge, preclinical in vivo studies have become paramount in understanding CCA carcinogenesis, progression, and therapy. Various CCA animal models exist including carcinogen-based models in which animals develop CCA after exposure to a carcinogen, genetically engineered mouse models in which genetic changes are induced in mice leading to CCA, murine syngeneic orthotopic models, as well as xenograft tumors derived from xenotransplantation of CCA cells, organoids, and patient-derived tissue. Each type has distinct advantages as well as shortcomings. In the ideal animal model of CCA, the tumor arises from the biliary tract in an immunocompetent host with a species-matched tumor microenvironment. Such a model would also be time-efficient, recapitulate the genetic and histopathological features of human CCA, and predict therapeutic response in humans. Recently developed biliary tract transduction and orthotopic syngeneic transplant mouse models encompass several of these elements. Herein, we review the different animal models of CCA, their advantages and deficiencies, as well as features which mimic human CCA.

Epidermal growth factor-like domain multiple 7 (EGFL7): Expression and possible effect on biliary epithelium growth in cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary tract malignancy with limited treatment options and low survival rates. The intrahepatic subtype comprises two forms: mucin-iCCA and mixed-iCCA. Epidermal growth factor-like domain multiple (EGFL7) is overexpressed in less differentiated liver tumors. The aim of this study was to assess the presence of EGFL7 due to its possible role in the growth of CCA. Hematoxylin & Eosin and periodic acid- Schiff staining were used to evaluate the morphological aspects and glycogen deposition. Immunohistochemistry and immunofluorescence were performed to identify the presence of EGFL7 both in tumor sections ex vivo and in appropriate cell lines in culture. We found that EGFL7 is expressed in malignant cholangiocytes of mixed-iCCA and absent in mucin-iCCA. In conclusion the expression of EGFL7 might be useful in the classification of CCA subtypes.

Animal models of cholangiocarcinoma: What they teach us about the human disease

Despite recent advances, pathogenesis of cholangiocarcinoma, a highly lethal cancer, remains enigmatic. Furthermore, treatment options are still limited and often disappointing. For this reason, in the last few years there has been a mounting interest towards the generation of experimental models able to reproduce the main features associated with this aggressive behavior. Toxic and infestation-induced, genetically engineered and cell implantation rodent models have been generated, contributing to a deeper understanding of the complex cell biology of the tumor, sustained by multiple cell interactions and driven by a huge variety of molecular perturbations. Herein, we will overview the most relevant animal models of biliary carcinogenesis, highlighting the methodological strategy, the molecular, histological and clinical phenotypes consistent with the human condition, their particular strengths and weaknesses and the novel therapeutic approaches that have been developed.

Role of the Nervous System in Tumor Angiogenesis

The development of cancer involves an intricate process, wherein many identified and unidentified factors play a role. Tumor angiogenesis, growth of new blood vessels, is one of the major prerequisites for tumor growth as tumor cells rely on adequate oxygen and nutrient supply as well as the removal of waste products. Growth factors including VEGF orchestrate the development of angiogenesis. In addition, nervous system via the release of neurotransmitters contributes to tumor angiogenesis. The nervous system governs functional activities of many organs, and, as tumors are not independent organs within an organism, this system is integrally involved in tumor growth and progression via regulating tumor angiogenesis. Various neurotransmitters have been reported to play an important role in tumor angiogenesis.

GABRA3 promotes lymphatic metastasis in lung adenocarcinoma by mediating upregulation of matrix metalloproteinases

Tumor metastasis is the main reason for the poor prognosis of lung cancer patients. The GABAA receptor subunit GABR_A3 is reportedly upregulated in lung cancer. Herein, we show that high GABR_A3 protein expression in lung adenocarcinoma correlated positively with disease stage, lymphatic metastasis status and poor patient survival. In addition, GABR_A3 induced MMP-2 and MMP-9 expression through activation of the JNK/AP-1 signaling pathway, which enhanced lymphatic metastasis by lung adenocarcinoma both in vitro and in vivo. These results indicate that GABR_A3 promotes lymph node metastasis and may thus be an effective therapeutic target for anticancer treatment.

Prolonged darkness reduces liver fibrosis in a mouse model of primary sclerosing cholangitis by miR-200b down-regulation

Melatonin therapy or prolonged exposure to complete darkness reduces biliary hyperplasia and liver fibrosis in bile-duct-ligated (BDL) rats; however, no information exists in primary sclerosing cholangitis (PSC). Thus, we aimed to determine the therapeutic effects of prolonged dark therapy or melatonin administration on hepatic fibrosis in the multidrug resistance gene 2-knockout (Mdr2^-/-) mouse model of PSC. Melatonin levels, biliary mass, liver fibrosis, angiogenesis and miR-200b expression were evaluated in wild-type and Mdr2^-/- mice exposed to darkness or melatonin treatment or in male patients with PSC and healthy controls. Mdr2^-/- mice were also treated with miR-200b inhibitor or control before evaluating biliary mass, liver fibrosis, and angiogenesis. After overexpression of arylalkylamine N-acetyltransferase (AANAT; the enzyme regulating melatonin synthesis) or inhibition of miR-200b in cholangiocytes and hepatic stellate cells in vitro, we evaluated angiogenesis and fibrosis gene expression. After exposure to darkness or administration of melatonin, Mdr2^-/- mice show elevated serum melatonin levels and inhibition of biliary mass, along with reduction of liver fibrosis and angiogenesis. MicroRNA PCR analysis demonstrated that miR-200b expression increased in Mdr2^-/- mice and patients with PSC compared with controls and decreased in Mdr2^-/- mice subjected to dark exposure or melatonin treatment. Inhibition of miR-200b in Mdr2^-/- ablates biliary proliferation, liver fibrosis, and angiogenesis. In vitro, overexpression of AANAT or inhibition of miR-200b in cholangiocytes and hepatic stellate cells decreased the expression of miR-200b, angiogenesis, and fibrosis genes. Dark therapy or targeting melatonin/miR-200b axis may be important in the management of biliary damage and liver fibrosis in cholangiopathies including PSC.-Wu, N., Meng, F., Zhou, T., Han, Y., Kennedy, L., Venter, J., Francis, H., DeMorrow, S., Onori, P., Invernizzi, P., Bernuzzi, F., Mancinelli, R., Gaudio, E., Franchitto, A., Glaser, S., Alpini G. Prolonged darkness reduces liver fibrosis in a mouse model of primary sclerosing cholangitis by miR-200b down-regulation.

GABABR-Induced EGFR Transactivation Promotes Migration of Human Prostate Cancer Cells

G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) act in concert to regulate cell growth, proliferation, survival, and migration. Metabotropic GABA_B receptor (GABA_BR) is the GPCR for the main inhibitory neurotransmitter GABA in the central nervous system. Increased expression of GABA_BR has been detected in human cancer tissues and cancer cell lines, but the role of GABA_BR in these cells is controversial and the underlying mechanism remains poorly understood. Here, we investigated whether GABA_BR hijacks RTK signaling to modulate the fates of human prostate cancer cells. RTK array analysis revealed that the GABA_BR-specific agonist baclofen selectively induced the transactivation of EGFR in PC-3 cells. EGFR transactivation resulted in the activation of ERK1/2 by a mechanism that is dependent on G_i/o protein and that requires matrix metalloproteinase-mediated proligand shedding. Positive allosteric modulators (PAMs) of GABA_BR, such as CGP7930, rac-BHFF, and GS39783, can function as PAM agonists to induce EGFR transactivation and subsequent ERK1/2 activation. Moreover, both baclofen and CGP7930 promoted cell migration and invasion through EGFR signaling. In summary, our observations demonstrated that GABA_BR transactivated EGFR in a ligand-dependent mechanism to promote prostate cancer cell migration and invasion, thus providing new insights into developing a novel strategy for prostate cancer treatment by targeting neurotransmitter signaling.

Nicotine Promotes Cholangiocarcinoma Growth in Xenograft Mice

Nicotine, the main addictive substance in tobacco, is known to play a role in the development and/or progression of a number of malignant tumors. However, nicotine's involvement in the pathogenesis of cholangiocarcinoma is controversial. Therefore, we studied the effects of nicotine on the growth of cholangiocarcinoma cells in vitro and the progression of cholangiocarcinoma in a mouse xenograft model. The predominant subunit responsible for nicotine-mediated proliferation in normal and cancer cells, the α7 nicotinic acetylcholine receptor (α7-nAChR), was more highly expressed in human cholangiocarcinoma cell lines compared with normal human cholangiocytes. Nicotine also stimulated the proliferation of cholangiocarcinoma cell lines and promoted α7-nAChR-dependent activation of proliferation and phosphorylation of extracellular-regulated kinase in Mz-ChA-1 cells. In addition, nicotine and PNU282987 (α7-nAChR agonist) accelerated the growth of the cholangiocarcinoma tumors in our xenograft mouse model and increased fibrosis, proliferation of the tumor cells, and phosphorylation of extracellular-regulated kinase activation. Finally, α7-nAChR was expressed at significantly higher levels in human cholangiocarcinoma compared with normal human control liver samples. Taken together, results of this study suggest that nicotine acts through α7-nAChR and plays a novel role in the pathogenesis of cholangiocarcinoma. Furthermore, nicotine may act as a mitogen in cholestatic liver disease processes, thereby facilitating malignant transformation.

Expert consensus document: Cholangiocarcinoma: current knowledge and future perspectives consensus statement from the European Network for the Study of Cholangiocarcinoma (ENS-CCA)

Cholangiocarcinoma (CCA) is a heterogeneous group of malignancies with features of biliary tract differentiation. CCA is the second most common primary liver tumour and the incidence is increasing worldwide. CCA has high mortality owing to its aggressiveness, late diagnosis and refractory nature. In May 2015, the "European Network for the Study of Cholangiocarcinoma" (ENS-CCA: www.enscca.org or www.cholangiocarcinoma.eu) was created to promote and boost international research collaboration on the study of CCA at basic, translational and clinical level. In this Consensus Statement, we aim to provide valuable information on classifications, pathological features, risk factors, cells of origin, genetic and epigenetic modifications and current therapies available for this cancer. Moreover, future directions on basic and clinical investigations and plans for the ENS-CCA are highlighted.

GABAB R/GSK-3β/NF-κB signaling pathway regulates the proliferation of colorectal cancer cells

Colorectal cancer is one of the leading causes of highly fatal cancer-related deaths in the whole world. Fast growth is critical characteristic of colorectal cancer, the underlying regulatory mechanism of colorectal cell fast proliferation remains largely unknown. Here, we reported that activation of metabotropic γ-Aminobutyric acid receptor (GABAB R) signaling significantly inhibited the colorectal cell HT29 proliferation by arresting the cell at G1 phase. Inhibition of GABAB R activated GSK-3β by reducing the phosphorylation level of GSK-3β. Activation of GSK-3β blocked the function of GABAB R signaling on repressing cell proliferation. We further found that GABAB R activation inhibited NF-κB activity. The promotion of cell proliferation caused by downregulation of GABRB R could be blocked by inhibition of NF-κB activation. Overall, activation of GABAB R leaded to inhibition of GSK-3β activation to repress the NF-κB function during colorectal cancer cell proliferation. This study revealed critical function of GABAB R/GSK-3β/NF-κB signaling pathway on regulating proliferation of colorectal cancer cell, which might provide a potential therapeutic target for clinical colorectal cancer treatment.

A role for cAMP-driven transactivation of EGFR in cancer aggressiveness - therapeutic implications

In many common cancers, production of cAMP boosts cancer proliferation, survival, and aggressiveness, reflecting the fact that, through mechanisms that require further clarification, cAMP can promote tyrosine phosphorylation, notably transactivation of the epidermal growth factor receptor (EGFR). Hormones which activate adenylate cyclase in many cancers include PGE2 - often produced by cox-2 activity within tumors - and adrenergic hormones, acting on beta2 receptors. NSAID cyclooxygenase inhibitors, including low-dose aspirin, clearly reduce risk for many adenocarcinomas, but the impact of cox-2 inhibitors in clinical cancer therapy remains somewhat equivocal. There is increasing evidence that increased sympathetic drive, often reflecting psychic stress or tobacco usage, increases risk for, and promotes the aggressiveness of, many cancers. The non-specific beta antagonist propranolol shows cancer-retardant activity in pre-clinical rodent studies, especially in stressed animals, and a limited amount of epidemiology concludes that concurrent propranolol usage is associated with superior prognosis in breast cancer, ovarian cancer, and melanoma. Epidemiology correlating increased resting heart rate with increased total cancer mortality can be interpreted as compelling evidence that increased sympathetic drive encourages the onset and progression of common cancers. Conversely, hormones which inhibit adenylate cyclase activity in cancers may have potential for cancer control; GABA, which can be administered as a well-tolerated nutraceutical, has potential in this regard. Combination regimens intended to down-regulate cancer cAMP levels, perhaps used in conjunction with EGFR inhibitors, may have considerable potential for suppressing the contribution of cAMP/EGFR to cancer aggressiveness. This model also predicts that certain other hormones which activate adenylate cylase in various tissue may play a yet-unsuspected role in cancer induction and spread.

GABAergic signaling facilitates breast cancer metastasis by promoting ERK1/2-dependent phosphorylation

The present study aims to determine the role of γ-aminobutyric acid (GABA) signaling molecules in breast cancer metastasis. Our results reveal that GABAergic system exists in breast cancer cells. Both the GABA synthetic enzyme. (GAD65/67) and GABAB receptor are expressed in 4T1 mouse breast cancer cells, MCF-7 human breast cancer cells and human breast cancer tissue. Baclofen, a GABABR agonist, significantly promoted 4T1 cells invasion and migration in vitro and metastasis in vivo, an event that was attenuated by GABABR antagonist CGP55845. Baclofen-induced breast cancer metastasis was mediated by ERK1/2 pathway.

Hydrodynamic transfection for generation of novel mouse models for liver cancer research

Primary liver cancers, including hepatocellular carcinoma and intrahepatic cholangiocarcinoma, are leading causes of cancer-related death worldwide. Recent large-scale genomic approaches have identified a wide number of genes whose deregulation is associated with hepatocellular carcinoma and intrahepatic cholangiocarcinoma development. Murine models are critical tools to determine the oncogenic potential of these genes. Conventionally, transgenic or knockout mouse models are used for this purpose. However, several limitations apply to the latter models. Herein, we review a novel approach for stable gene expression in mouse hepatocytes by hydrodynamic injection in combination with Sleeping Beauty-mediated somatic integration. This method represents a flexible, reliable, and cost-effective tool to generate preclinical murine models for liver cancer research. Furthermore, it can be used as an in vivo transfection method to study biochemical cross talks among multiple pathways along hepatocarcinogenesis and to test the therapeutic potential of drugs against liver cancer.

Pathogenesis, diagnosis, and management of cholangiocarcinoma

Cholangiocarcinomas (CCAs) are hepatobiliary cancers with features of cholangiocyte differentiation; they can be classified anatomically as intrahepatic CCA (iCCA), perihilar CCA (pCCA), or distal CCA. These subtypes differ not only in their anatomic location, but in epidemiology, origin, etiology, pathogenesis, and treatment. The incidence and mortality of iCCA has been increasing over the past 3 decades, and only a low percentage of patients survive until 5 years after diagnosis. Geographic variations in the incidence of CCA are related to variations in risk factors. Changes in oncogene and inflammatory signaling pathways, as well as genetic and epigenetic alterations and chromosome aberrations, have been shown to contribute to the development of CCA. Furthermore, CCAs are surrounded by a dense stroma that contains many cancer-associated fibroblasts, which promotes their progression. We have gained a better understanding of the imaging characteristics of iCCAs and have developed advanced cytologic techniques to detect pCCAs. Patients with iCCAs usually are treated surgically, whereas liver transplantation after neoadjuvant chemoradiation is an option for a subset of patients with pCCAs. We review recent developments in our understanding of the epidemiology and pathogenesis of CCA, along with advances in classification, diagnosis, and treatment.

GABA induces the differentiation of small into large cholangiocytes by activation of Ca(2+) /CaMK I-dependent adenylyl cyclase 8

Large, but not small, cholangiocytes (1) secrete bicarbonate by interaction with secretin receptors (SRs) through activation of cystic fibrosis transmembrane regulator (CFTR), Cl(-) /HCO3 (-) (apex) anion exchanger 2 (Cl(-) /HCO3 (-) AE2), and adenylyl cyclase (AC)8 (proteins regulating large biliary functions) and (2) proliferate in response to bile duct ligation (BDL) by activation of cyclic adenosine monophosphate (cAMP) signaling. Small, mitotically dormant cholangiocytes are activated during damage of large cholangiocytes by activation of D-myo-inositol 1,4,5-trisphosphate/Ca(2+) /calmodulin-dependent protein kinase (CaMK) I. gamma-Aminobutyric acid (GABA) affects cell functions by modulation of Ca(2+) -dependent signaling and AC. We hypothesized that GABA induces the differentiation of small into large cholangiocytes by the activation of Ca(2+) /CaMK I-dependent AC8. In vivo, BDL mice were treated with GABA in the absence or presence of 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, tetraacetoxymethyl ester (BAPTA/AM) or N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide (W7) before evaluating apoptosis and intrahepatic bile ductal mass (IBDM) of small and large cholangiocytes. In vitro, control- or CaMK I-silenced small cholangiocytes were treated with GABA for 3 days before evaluating apoptosis, proliferation, ultrastructural features, and the expression of CFTR, Cl(-) /HCO3 (-) AE2, AC8, and secretin-stimulated cAMP levels. In vivo administration of GABA induces the apoptosis of large, but not small, cholangiocytes and decreases large IBDM, but increased de novo small IBDM. GABA stimulation of small IBDM was blocked by BAPTA/AM and W7. Subsequent to GABA in vitro treatment, small cholangiocytes de novo proliferate and acquire ultrastructural and functional phenotypes of large cholangiocytes and respond to secretin. GABA-induced changes were prevented by BAPTA/AM, W7, and stable knockdown of the CaMK I gene.

CONCLUSION

GABA damages large, but not small, cholangiocytes that differentiate into large cholangiocytes. The differentiation of small into large cholangiocytes may be important in the replenishment of the biliary epithelium during damage of large, senescent cholangiocytes.

Liver carcinogenesis: rodent models of hepatocarcinoma and cholangiocarcinoma

Hepatocellular carcinoma and cholangiocarcinoma are primary liver cancers, both represent a growing challenge for clinicians due to their increasing morbidity and mortality. In the last few years a number of in vivo models of hepatocellular carcinoma and cholangiocarcinoma have been developed. The study of these models is providing a significant contribution in unveiling the pathophysiology of primary liver malignancies. They are also fundamental tools to evaluate newly designed molecules to be tested as new potential therapeutic agents in a pre-clinical set. Technical aspects of each model are critical steps, and they should always be considered in order to appropriately interpret the findings of a study or its planning. The purpose of this review is to describe the technical and experimental features of the most significant rodent models, highlighting similarities or differences between the corresponding human diseases. The first part is dedicated to the discussion of models of hepatocellular carcinoma, developed using toxic agents, or through dietary or genetic manipulations. In the second we will address models of cholangiocarcinoma developed in rats or mice by toxin administration, genetic manipulation and/or bile duct incannulation or surgery. Xenograft or syngenic models are also proposed.

Suppression of Human Liver Cancer Cell Migration and Invasion via the GABAA Receptor

Objective

To investigate the roles of the γ-aminobutyric acid (GABA) in the metastasis of hepatocellular carcinoma (HCC) and to explore the potential of a novel therapeutic approach for the treatment of HCC.

Methods

The expression levels of GABA receptor subunit genes in various HCC cell lines and patients‘ tissues were detected by quantitative real-time polymerase chain reaction and Western blot analysis. Transwell cell migration and invasion assays were carried out for functional analysis. The effects of GABA on liver cancer cell cytoskeletal were determined by immunofluorescence staining. And the effects of GABA on HCC metastasis in nude mice were evaluated using an in vivo orthotopic model of liver cancer.

Results

The mRNA level of GABA receptor subunits varied between the primary hepatocellular carcinoma tissue and the adjacent non-tumor liver tissue. GABA inhibited human liver cancer cell migration and invasion via the ionotropic GABA_A receptor as a result of the induction of liver cancer cell cytoskeletal reorganization. Pretreatment with GABA also significantly reduced intrahepatic liver metastasis and primary tumor formation in vivo.

Conclusions

These findings introduce a potential and novel therapeutic approach for the treatment of cancer patients based on the modulation of the GABAergic system.

Gamma-aminobutyric acid binds to GABAb receptor to inhibit cholangiocarcinoma cells growth via the JAK/STAT3 pathway

BACKGROUND

Gamma-aminobutyric acid (GABA) has been reported to inhibit the growth of cholangiocarcinoma QBC939 cells, but the mechanisms are still not fully understood.

AIMS

To explore the mechanisms of the anti-cancer effect of GABA on QBC939 cells.

METHODS

An initial immunohistochemistry study of the expressions of GABA receptors in cholangiocarcinoma tissues was followed by the culture and treatment of QBC939 cells for 48 h with GABA, GABA + bicuculine (GABAA receptor antagonist), GABA + phaclofen (GABAB receptor antagonist), and GABA + AG490 (Janus Kinase inhibitor). MTT and Annexin V-FITC/PI binding assays were used to determine the proliferation and apoptosis of the QBC939 cells. The expression of the signal transducer and activator of transcription 3 (STAT3) and phosphorylated STAT3 (Tyr705) [p-STAT3 (Tyr705)] was evaluated by the western blot assay. The effect of GABA on the growth of QBC939 xenograft tumors in athymic nu/nu mice was examined, and p-STAT3 (Tyr705) expression in xenograft tumors was detected by immunohistochemistry.

RESULTS

A significant difference was only observed in GABAB receptor expression between cholangiocarcinoma and normal bile tissues. The MTT and Annexin V-FITC/PI assays showed that the antiproliferative and proapoptotic effects of GABA on QBC939 cells could be antagonized by phaclofen and AG490, but not bicuculine. GABA significantly down-regulated p-STAT3 (Tyr705) expression; this action was also antagonized by phaclofen and AG490. GABA also effectively inhibited xenograft tumor growth, and p-STAT3 (Tyr705) expression was significantly decreased in GABA-treated xenograft tumors.

CONCLUSIONS

GABA may inhibit the growth of cholangiocarcinoma QBC939 cells through the GABAB receptor, and the anti-cancer effects may be partly mediated via the JAK/STAT3 pathway.

Role of the nervous system in cancer metastasis

The notion that tumors lack innervation was proposed several years ago. However, nerve fibers are irregulatedly found in some tumor tissues. Their terminals interaction with cancer cells are considered to be neuro-neoplastic synapses. Moreover, neural-related factors, which are important players in the development and activity of the nervous system, have been found in cancer cells. Thus, they establish a direct connection between the nervous system and tumor cells. They modulate the process of metastasis, including degradation of base membranes, cancer cell invasion, migration, extravasation and colonization. Peripheral nerve invasion provides another pathway for the spread of cancer cells when blood and lymphatic metastases are absent, which is based on the interactions between the microenvironments of nerve fibers and tumor cells. The nervous system also modulates angiogenesis, the tumor microenvironment, bone marrow, immune functions and inflammatory pathways to influence metastases. Denervation of the tumor has been reported to enhance cancer metastasis. Stress, social isolation and other emotional factors may increase distant metastasis through releasing hormones from the brain, the hypothalamic-pituitary-adrenal axis and autonomic nervous system. Disruption of circadian rhythms will also promote cancer metastasis through direct and indirect actions of the nervous system. Therefore, the nervous system plays an important role in cancer metastasis.

Sodium valproate inhibits the growth of human cholangiocarcinoma in vitro and in vivo

Background. None of treatment options for Cholangiocarcinoma (CCA), including surgery, adjuvant radiotherapy and chemotherapy, and ultimately liver transplantation, have been shown to substantially improve the survival rate in patients with CCA. Valproic acid (VPA), a histone deacetylase inhibitor, has been shown to display potent antitumor effects. In this study, sodium valproate, the clinically available form of VPA, was tested for its ability to inhibit the growth of cholangiocarcinoma cells, both in vitro and in vivo. Materials and Methods. Cholangiocarcinoma cells (TFK-1, QBC939, and CCLP1) of different origins were treated with sodium valproate to determine their effects on cell proliferation and differentiation, cell cycle regulation, apoptosis, and autophagy. The in vivo effects of sodium valproate on cholangiocarcinoma growth were assessed using a xenograft mouse model injected with TFK-1 cells. Results. Sodium valproate inhibited cholangiocarcinoma cell growth by inducing cell cycle arrest, cell differentiation, and apoptosis; sodium valproate effects were independent of autophagy. Tumor growth inhibition was also observed in vivo using TFK-1 xenografts. Conclusion. The in vitro and in vivo outcomes provide preclinical rationale for clinical evaluation of sodium valproate, alone or in combination with other drugs, to improve patient outcome in cholangiocarcinoma.

GABA stimulates human hepatocellular carcinoma growth through overexpressed GABAA receptor theta subunit

AIM: To investigate the function of gamma-aminobutyric acid (GABA) and gamma-aminobutyric acid A receptor θ subunit (GABRQ) in hepatocellular carcinoma (HCC).

METHODS: Semiquantitative polymerase chain reaction was used for detecting the expression of GABRQ receptor among HCC cell line HepG2, normal liver cell line L-02, non-malignant Chang’s liver cells, 8 samples of HCC tissues and paired non-cancerous tissues. HepG2 cells were treated with GABA at serial concentrations (0, 1, 10, 20, 40 and 60 μmol/L), and their proliferating abilities were analyzed with the methyl thiazolyl tetrazolium assay, cell cycle analysis and tumor implanted in nude mice. Small interfering RNA was used for knocking down the endogenous GABRQ in HepG2. Proliferating abilities of these cells treated with or without GABA were analyzed.

RESULTS: We identified the overexpression of GABRQ in HCC cell lines and half of the tested HCC tissues. Knockdown of endogenous GABRQ expression in HepG2 attenuated HCC cell growth, suggesting its role in HCC cell viability. We studied the effect of GABA in the proliferation of GABRQ-positive cell lines in vitro and in vivo, and found that GABA increased HCC growth in a dose-dependent manner. Notably, the addition of GABA into the cell culture medium promoted the proliferation of GABRQ-expressing HepG2 cells, but not GABRQ-knockdown HepG2 cells, which means that GABA stimulates HepG2 cell growth through GABRQ.

CONCLUSION: GABRQ play important roles in HCC development and progression and could be a promising molecular target for the development of new diagnostic and therapeutic strategies of HCC.

Role of γ-aminobutyric acid and its receptors in carcinogenesis

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the adult mammalian brain and it is also expressed in the central nervous system, peripheral nerves and peripheral non-neural tissues. Recent studies have shown that GABA is involved in the proliferation and migration of tumor cells and other processes of tumor development. According to different sensitivity to agonists and antagonists, GABA receptors have been classified into three types: A, B and C. GABA receptors and their receptor subunits are involved in complicated regulation of tumor cells. Many studies have demonstrated that GABA binding to its receptors can activate or inhibit the cAMP signaling pathway and the MAPK/ERK pathway, and regulate cancer cell proliferation and migration. The potential value of GABA in cancer diagnosis, prognostic prediction and biotherapy has been gradually revealed. In the present article, we reviewed the recent progress in understanding the role of GABA and its receptors in carcinogenesis.

Cytotoxicity, toxicity, and anticancer activity of Zingiber officinale Roscoe against cholangiocarcinoma

Cholangiocarcinoma (CCA) is an uncommon adenocarcinoma which arises from the epithelial cells of the bile ducts. The aim of the study was to investigate the cytotoxicity, toxicity, and anticancer activity of a crude ethanolic extract of ginger (Zingiber officinale Roscoe) against CCA. Cytotoxic activity against a CCA cell line (CL-6) was assessed by calcein-AM and Hoechst 33342 assays and anti-oxidant activity was evaluated using the DPPH assay. Investigation of apoptotic activity was performed by DNA fragmentation assay and induction of genes that may be involved in the resistance of CCA to anticancer drugs (MDR1, MRP1, MRP2, and MRP3) was examined by real-time PCR. To investigate anti-CCA activity in vivo, a total of 80 OV and nitrosamine (OV/ DMN)-induced CCA hamsters were fed with the ginger extract at doses of 1000, 3000, and 5000 mg/kg body weight daily or every alternate day for 30 days. Control groups consisting of 10 hamsters for each group were fed with 5-fluorouracil (positive control) or distilled water (untreated control). Median IC50 (concentration that inhibits cell growth by 50%) values for cytotoxicity and anti-oxidant activities of the crude ethanolic extract of ginger were 10.95, 53.15, and 27.86 μg/ml, respectively. More than ten DNA fragments were visualized and up to 7-9 fold up-regulation of MDR1 and MRP3 genes was observed following exposure to the ethanolic extract of ginger. Acute and subacute toxicity tests indicated absence of any significant toxicity at the maximum dose of 5,000 mg/kg body weight given by intragastric gavage. The survival time and survival rate of the CCA-bearing hamsters were significantly prolonged compared to the control group (median of 54 vs 17 weeks). Results from these in vitro and in vivo studies thus indicate promising anticancer activity of the crude ethanolic extract of ginger against CCA with the absence of any significant toxicity. Moreover, MDR1 and MRP3 may be involved in conferring resistance of CCA to the ginger extract.

Molecular pathogenesis of cholangiocarcinoma

Epidemiological data from the last years show an increasing trend of incidence and mortality of cholangiocarcinoma (CC) worldwide. Many pathophysiologic aspects of this neoplasia are still unknown and need to be fully discovered. However, several progresses were recently made in order to establish the molecular mechanisms involved in the transformation and growth of malignant cholangiocytes. The principal concept that at least seems to be established is that cholangiocarcinogenesis is a multistep cellular process evolving from a normal condition of the epithelial biliary cells through a chronic inflammation status ending with malignant transformation. The bad prognosis related to CC justifies why a better identification of the molecular mechanisms involved in the growth and progression of this cancer is required for the development of effective preventive measures and valid treatment regimens. This Paper describes the scientific progresses made in the last years in defining the molecular pathways implicated in the generation of this devastating disease.

Primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic liver condition which may affect both intra and extrahepatic biliary tree. Etiology of PSC remains to be fully elucidated but genetic, autoimmune, inflammatory and possibly infective factors could all contribute to its development. More than two-thirds of patients are males and the most commonly associated condition is an inflammatory bowel disease which occurs in up to 70% of affected subjects. Endoscopic cholangiopancreatography (ERCP) and magnetic resonanse cholangiopancreatography (MRCP) remain a gold standard in the diagnosis of this condition. No curative treatment of PSC exists and a proportion of patients who develop liver failure or suffer from recurrent episodes of cholangitis requires liver transplantation. PSC is associated with increased risk of malignancies, in particular cholangiocarcinoma which may arise in 12% of patients. The main aim of this chapter is to review the current knowledge on pathogenesis and clinical aspects of PSC as well as its associated malignancies.

GABA-B receptor activation inhibits the in vitro migration of malignant hepatocytes

There are conflicting data regarding whether activation of γ-aminobutyric acid-B (GABA-B) receptors results in inhibition of tumor growth and invasion. The objectives of this study were to document the effects of the GABA-B receptor agonist baclofen on malignant hepatocyte proliferation and migration. We also sought to determine whether any effects on cell migration were mediated by changes in cyclic adenosine monophosphate (cAMP) signaling or matrix metalloproteinase (MMP) expression. Finally, GABA-B(1) and -B(2) receptor expression was documented in 2 malignant hepatocyte cell lines (PLC/PRF/5 and Huh-7) and 12 sets of human hepatocellular carcinoma and adjacent nontumor tissues. Cell proliferative activity was documented by WST-1 absorbance, migration by wound healing assays, cAMP levels by enzyme-linked immunoassay (ELISA), MMP by immunohistochemistry and ELISA, and GABA-B receptor expression by flow cytometry and reverse transcriptase - polymerase chain reaction. Although baclofen had no effect on cell proliferation, wound healing was delayed, an effect that was reversed by the GABA-B receptor antagonist CGP. cAMP levels were decreased in Huh-7 but not PLC cells exposed to baclofen. MMP expression remained unaltered in both cell lines. Finally, GABA-B(1) receptor expression was present and consistently expressed, but GABA-B(2) expression was limited and varied with the number of cell passages and (or) duration of culture. In conclusion, activation of GABA-B receptors has no effect on malignant hepatocyte proliferation but does decrease cell migration. This inhibitory effect may involve cAMP signaling but not MMP expression. GABA-B(2) receptor expression is limited and variable, which may help to explain discrepancies with previously published results.

Neuropeptide Y inhibits cholangiocarcinoma cell growth and invasion

No information exists on the role of neuropeptide Y (NPY) in cholangiocarcinoma growth. Therefore, we evaluated the expression and secretion of NPY and its subsequent effects on cholangiocarcinoma growth and invasion. Cholangiocarcinoma cell lines and nonmalignant cholangiocytes were used to assess NPY mRNA expression and protein secretion. NPY expression was assessed by immunohistochemistry in human liver biopsies. Cell proliferation and migration were evaluated in vitro by MTS assays and matrigel invasion chambers, respectively, after treatment with NPY or a neutralizing NPY antibody. The effect of NPY or NPY depletion on tumor growth was assessed in vivo after treatment with NPY or the neutralizing NPY antibody in a xenograft model of cholangiocarcinoma. NPY secretion was upregulated in cholangiocarcinoma compared with normal cholangiocytes. Administration of exogenous NPY decreased proliferation and cell invasion in all cholangiocarcinoma cell lines studied and reduced tumor cell growth in vivo. In vitro, the effects of NPY on proliferation were blocked by specific inhibitors for NPY receptor Y2, but not Y1 or Y5, and were associated with an increase in intracellular d-myo-inositol 1,4,5-trisphosphate and PKCα activation. Blocking of NPY activity using a neutralizing antibody promoted cholangiocarcinoma growth in vitro and in vivo and increased the invasiveness of cholangiocarcinoma in vitro. Increased NPY immunoreactivity in human tumor tissue occurred predominantly in the center of the tumor, with less expression toward the invasion front of the tumor. We demonstrated that NPY expression is upregulated in cholangiocarcinoma, which exerts local control on tumor cell proliferation and invasion. Modulation of NPY secretion may be important for the management of cholangiocarcinoma.

Resveratrol enhances the sensitivity of cholangiocarcinoma to chemotherapeutic agents

Cholangiocarcinomas are devastating cancers that are resistant to chemotherapies. Resveratrol, a food-derived polyphenol with antitumorigenic properties, can regulate the expression of cytochrome p450 1b1 (Cyp1b1), which may confer chemoresistance in various cancers. Our aims were to assess the effects of resveratrol on the sensitivity of cholangiocarcinoma cells to chemotherapeutic agents and show an association between Cyp1b1 expression and chemosensitivity. Cholangiocarcinoma cell lines were treated with resveratrol before the addition of 5-fluorouracil (5-FU), gemcitabine, or mitomycin C. Cell proliferation and apoptosis were assessed by MTS assays and Annexin staining. Resveratrol effects on cholangiocarcinoma tumor sensitivity to 5-FU was assessed in an in vivo xenograft model using Mz-ChA-1 cells. After resveratrol treatment, Cyp1b1 expression was assessed by real-time PCR and immunoblotting. Stable-transfected cell lines with Cyp1b1 expression knocked down (Mz-Cyp1b1) were used to assess sensitivity to chemotherapeutic agents by MTS assays and Annexin staining and in a xenograft model using Mz-ChA-1 and Mz-Cyp1b1 cells, respectively. For each chemotherapeutic agent, co-treatment with resveratrol in vitro decreased cell proliferation and increased apoptosis to a greater extent than with the chemotherapeutic agent alone. In vivo, 5-FU+resveratrol decreased tumor size and increased TUNEL staining to a greater extent than 5-FU alone. In parallel, resveratrol decreased Cyp1b1 expression in Mz-ChA-1 cells and in cholangiocarcinoma tumors. Mz-Cyp1b1 cells were more sensitive to chemotherapeutic agents in vitro than mock-transfected cells, and Mz-Cyp1b1-induced tumors were more susceptible to 5-FU treatment. We suggest that resveratrol treatment may be a useful adjunct therapy to improve chemosensitivity in cholangiocarcinoma.

Recent advances in the regulation of cholangiocarcinoma growth

Cholangiocarcinomas arise after the neoplastic transformation of the cholangiocytes that line the intra- and extrahepatic biliary epithelium. Symptoms usually do not present until late in the course of the disease, at which time they are relatively resistant to chemotherapeutic agents and as such are difficult to treat and display a poor prognosis. Because of the relative rarity of this disease, the overall volume of research into the molecular pathophysiology associated with this disease is small compared with other more prevalent tumors. However, the incidence of this devastating cancer is on the rise and renewed efforts to understand the pathogenesis of cholangiocarcinoma is needed to design novel therapeutic strategies to combat this disease. This review summarizes the recent advances into our knowledge and understanding of cholangiocarcinoma and highlights potential novel therapeutic strategies that may prove useful to treat this deadly disease.

Histamine regulation of hyperplastic and neoplastic cell growth in cholangiocytes

Histamine has long been known to be involved in inflammatory events. The discovery of antihistamines dates back to the first half of the 20^th century when a Swiss-Italian pharmacologist, Daniel Bovet began his work. In 1957 he was awarded a Nobel Prize for his production of antihistamines for allergy relief. Since that time, histamine has been found to play a role in other events besides allergic reaction. Possibly unbelievable to Bovet and his peers, histamine has now been marked as playing a role in liver pathologies including hepatobiliary diseases.

Molecular mechanisms of cholangiocarcinoma

Cholangiocarcinoma (CC), the malignant tumor of the epithelial cells lining the biliary ducts, has undergone a worldwide increase in incidence and mortality. The malignant transformation of the biliary cells originates from a multistep process evolving through chronic inflammation of the biliary tract to CC. In the last few years several advances have been towards understanding and clarifying the molecular mechanisms implicated in the cholangiocarcinogenesis process. However, many pathophysiologic aspects governing the growth of CC are still undefined. The poor prognosis of this tumor underlines the urgent need to codify the underlying molecular mechanisms involved in the growth and progression of CC in order to design effective preventive measures and valid treatment regimens. This review reports on progresses made in the last few years in clarifying the molecular pathways involved in the process of cholangiocarcinogenesis.