Context-Dependent Distinct Roles of SOX9 in Combined Hepatocellular Carcinoma-Cholangiocarcinoma.

Combined hepatocellular carcinoma-cholangiocarcinoma (cHCC-CCA) is a challenging primary liver cancer subtype with limited treatment options and a devastating prognosis. Recent studies have underscored the context-dependent roles of SOX9 in liver cancer formation in a preventive manner. Here, we revealed that liver-specific developmental Sox9 elimination using Alb-Cre;Sox9(flox/flox) (LKO) and CRISPR/Cas9-based tumor-specific acute Sox9 elimination (CKO) in SB-HDTVI-based Akt-YAP1 (AY) and Akt-NRAS (AN) cHCC-CCA models showed contrasting responses. LKO abrogates the AY CCA region while stimulating poorly differentiated HCC proliferation, whereas CKO prevents AY and AN cHCC-CCA development irrespective of tumor cell fate. Additionally, AN, but not AY, tumor formation partially depends on the Sox9-Dnmt1 cascade. SOX9 is dispensable for AY-mediated, HC-derived, LPC-like immature CCA formation but is required for their maintenance and transformation into mature CCA. Therapeutic Sox9 elimination using the OPN-CreERT2 strain combined with inducible Sox9 iKO specifically reduces AY but not AN cHCC-CCA tumors. This necessitates the careful consideration of genetic liver cancer studies using developmental Cre and somatic mutants, particularly for genes involved in liver development. Our findings suggest that SOX9 elimination may hold promise as a therapeutic approach for a subset of cHCC-CCA and highlight the need for further investigation to translate these preclinical insights into personalized clinical applications.

Loss of ß-catenin reveals a role for glutathione in regulating oxidative stress during cholestatic liver disease.

BACKGROUND: Cholestasis is an intractable liver disorder that results from impaired bile flow. We have previously shown that the Wnt/ß-catenin signaling pathway regulates the progression of cholestatic liver disease through multiple mechanisms, including bile acid metabolism and hepatocyte proliferation. To further explore the impact of these functions during intrahepatic cholestasis, we exposed mice to a xenobiotic that causes selective biliary injury. METHODS: α-naphthylisothiocyanate (ANIT) was administered to liver-specific knockout (KO) of ß-catenin and wild-type mice in the diet. Mice were killed at 6 or 14 days to assess the severity of cholestatic liver disease, measure the expression of target genes, and perform biochemical analyses. RESULTS: We found that the presence of ß-catenin was protective against ANIT, as KO mice had a significantly lower survival rate than wild-type mice. Although serum markers of liver damage and total bile acid levels were similar between KO and wild-type mice, the KO had minor histological abnormalities, such as sinusoidal dilatation, concentric fibrosis around ducts, and decreased inflammation. Notably, both total glutathione levels and expression of glutathione-S-transferases, which catalyze the conjugation of ANIT to glutathione, were significantly decreased in KO after ANIT. Nuclear factor erythroid-derived 2-like 2, a master regulator of the antioxidant response, was activated in KO after ANIT as well as in a subset of patients with primary sclerosing cholangitis lacking activated ß-catenin. Despite the activation of nuclear factor erythroid-derived 2-like 2, KO livers had increased lipid peroxidation and cell death, which likely contributed to mortality. CONCLUSIONS: Loss of ß-catenin leads to increased cellular injury and cell death during cholestasis through failure to neutralize oxidative stress, which may contribute to the pathology of this disease.

Therapeutic potential of SOX9 dysruption in Combined Hepatocellular Carcinoma-Cholangiocarcinoma.

Combined hepatocellular carcinoma-cholangiocarcinoma (cHCC-CCA) represents a challenging subtype of primary liver cancer with limited treatment options and a poor prognosis. Recently, we and others have highlighted the context-dependent roles of the biliary-specific transcription factor SOX9 in the pathogenesis of liver cancers using various Cre applications in Sox9 (flox/flox) strains, to achieve elimination for exon 2 and 3 of the Sox9 gene locus as a preventive manner. Here, we reveal the contrasting responses of developmental Sox9 elimination using Alb-Cre;Sox9 (flox/flox) ( Sox9 LKO) versus CRISPR/Cas9 -based tumor specific acute Sox9 CKO in SB-HDTVI-based Akt-YAP1 and Akt-NRAS cHCC-CCA formation. Sox9 LKO specifically abrogates the Akt-YAP1 CCA region while robustly stimulating the proliferation of remaining poorly differentiated HCC pertaining liver progenitor cell characteristics, whereas Sox9 CKO potently prevents Akt-YAP1 and Akt-NRAS cHCC-CCA development irrespective of fate of tumor cells compared to respective controls. Additionally, we find that Akt-NRAS , but not Akt-YAP1 , tumor formation is partially dependent on the Sox9-Dnmt1 cascade. Pathologically, SOX9 is indispensable for Akt-YAP1 -mediated HC-to-BEC/CCA reprogramming but required for the maintenance of CCA nodules. Lastly, therapeutic elimination of Sox9 using the OPN-CreERT2 strain combined with an inducible CRISPR/Cas9 -based Sox9 iKO significantly reduces Akt-YAP1 cHCC-CCA tumor burden, similar to Sox9 CKO. Thus, we contrast the outcomes of acute Sox9 deletion with developmental Sox9 knockout models, emphasizing the importance of considering adaptation mechanisms in therapeutic strategies. This necessitates the careful consideration of genetic liver cancer studies using developmental Cre and somatic mutant lines, particularly for genes involved in hepatic commitment during development. Our findings suggest that SOX9 elimination may hold promise as a therapeutic approach for cHCC-CCA and underscore the need for further investigation to translate these preclinical insights into clinical applications.

Expression of tumor antigens within an oncolytic virus enhances the anti-tumor T cell response.

Although patients benefit from immune checkpoint inhibition (ICI) therapy in a broad variety of tumors, resistance may arise from immune suppressive tumor microenvironments (TME), which is particularly true of hepatocellular carcinoma (HCC). Since oncolytic viruses (OV) can generate a highly immune-infiltrated, inflammatory TME, OVs could potentially restore ICI responsiveness via recruitment, priming, and activation of anti-tumor T cells. Here we find that on the contrary, an oncolytic vesicular stomatitis virus, expressing interferon-ß (VSV-IFNß), antagonizes the effect of anti-PD-L1 therapy in a partially anti-PD-L1-responsive model of HCC. Cytometry by Time of Flight shows that VSV-IFNß expands dominant anti-viral effector CD8 T cells with concomitant relative disappearance of anti-tumor T cell populations, which are the target of anti-PD-L1. However, by expressing a range of HCC tumor antigens within VSV, combination OV and anti-PD-L1 therapeutic benefit could be restored. Our data provide a cautionary message for the use of highly immunogenic viruses as tumor-specific immune-therapeutics by showing that dominant anti-viral T cell responses can inhibit sub-dominant anti-tumor T cell responses. However, through encoding tumor antigens within the virus, oncolytic virotherapy can generate anti-tumor T cell populations upon which immune checkpoint blockade can effectively work.

Selective Targeting of α4ß7/MAdCAM-1 Axis Suppresses Fibrosis Progression by Reducing Proinflammatory T Cell Recruitment to the Liver.

Integrin α4ß7+ T cells perpetuate tissue injury in chronic inflammatory diseases, yet their role in hepatic fibrosis progression remains poorly understood. Here, we report increased accumulation of α4ß7+ T cells in the liver of people with cirrhosis relative to disease controls. Similarly, hepatic fibrosis in the established mouse model of CCl4-induced liver fibrosis was associated with enrichment of intrahepatic α4ß7+ CD4 and CD8 T cells. Monoclonal antibody (mAb)-mediated blockade of α4ß7 or its ligand mucosal addressin cell adhesion molecule (MAdCAM)-1 attenuated hepatic inflammation and prevented fibrosis progression in CCl4-treated mice. Improvement in liver fibrosis was associated with a significant decrease in the infiltration of α4ß7+ CD4 and CD8 T cells, suggesting that α4ß7/MAdCAM-1 axis regulates both CD4 and CD8 T cell recruitment to the fibrotic liver, and α4ß7+ T cells promote hepatic fibrosis progression. Analysis of hepatic α4ß7+ and α4ß7- CD4 T cells revealed that α4ß7+ CD4 T cells were enriched for markers of activation and proliferation, demonstrating an effector phenotype. The findings suggest that α4ß7+ T cells play a critical role in promoting hepatic fibrosis progression, and mAb-mediated blockade of α4ß7 or MAdCAM-1 represents a promising therapeutic strategy for slowing hepatic fibrosis progression in chronic liver diseases.

Quantitative radiomics and qualitative LI-RADS imaging descriptors for non-invasive assessment of ß-catenin mutation status in hepatocellular carcinoma.

PURPOSE: Gain-of-function mutations in CTNNB1, gene encoding for ß-catenin, are observed in 25-30% of hepatocellular carcinomas (HCCs). Recent studies have shown ß-catenin activation to have distinct roles in HCC susceptibility to mTOR inhibitors and resistance to immunotherapy. Our goal was to develop and test a computational imaging-based model to non-invasively assess ß-catenin activation in HCC, since liver biopsies are often not done due to risk of complications. METHODS: This IRB-approved retrospective study included 134 subjects with pathologically proven HCC and available ß-catenin activation status, who also had either CT or MR imaging of the liver performed within 1 year of histological assessment. For qualitative descriptors, experienced radiologists assessed the presence of imaging features listed in LI-RADS v2018. For quantitative analysis, a single biopsy proven tumor underwent a 3D segmentation and radiomics features were extracted. We developed prediction models to assess the ß-catenin activation in HCC using both qualitative and quantitative descriptors. RESULTS: There were 41 cases (31%) with ß-catenin mutation and 93 cases (69%) without. The model's AUC was 0.70 (95% CI 0.60, 0.79) using radiomics features and 0.64 (0.52, 0.74; p = 0.468) using qualitative descriptors. However, when combined, the AUC increased to 0.88 (0.80, 0.92; p = 0.009). Among the LI-RADS descriptors, the presence of a nodule-in-nodule showed a significant association with ß-catenin mutations (p = 0.015). Additionally, 88 radiomics features exhibited a significant association (p < 0.05) with ß-catenin mutations. CONCLUSION: Combination of LI-RADS descriptors and CT/MRI-derived radiomics determine ß-catenin activation status in HCC with high confidence, making precision medicine a possibility.

Therapeutic targeting at genome mutations of liver cancer by the insertion of HSV1 thymidine kinase through Cas9-mediated editing.

BACKGROUND: Liver cancer is one of the most lethal malignancies for humans. The treatment options for advanced-stage liver cancer remain limited. A new treatment is urgently needed to reduce the mortality of the disease. METHODS: In this report, we developed a technology for mutation site insertion of a suicide gene (herpes simplex virus type 1- thymidine kinase) based on type II CRISPR RNA-guided endonuclease Cas9-mediated genome editing to treat liver cancers. RESULTS: We applied the strategy to 3 different mutations: S45P mutation of catenin beta 1, chromosome breakpoint of solute carrier family 45 member 2-alpha-methylacyl-CoA racemase gene fusion, and V235G mutation of SAFB-like transcription modulator. The results showed that the herpes simplex virus type 1-thymidine kinase insertion rate at the S45P mutation site of catenin beta 1 reached 77.8%, while the insertion rates at the breakpoint of solute carrier family 45 member 2 - alpha-methylacyl-CoA racemase gene fusion were 95.1%-98.7%, and the insertion at V235G of SAFB-like transcription modulator was 51.4%. When these targeting reagents were applied to treat mouse spontaneous liver cancer induced by catenin beta 1S45P or solute carrier family 45 member 2-alpha-methylacyl-CoA racemase, the mice experienced reduced tumor burden and increased survival rate. Similar results were also obtained for the xenografted liver cancer model: Significant reduction of tumor volume, reduction of metastasis rate, and improved survival were found in mice treated with the targeting reagent, in comparison with the control-treated groups. CONCLUSIONS: Our studies suggested that mutation targeting may hold promise as a versatile and effective approach to treating liver cancers.

shinyDeepDR: A user-friendly R Shiny app for predicting anti-cancer drug response using deep learning.

Advancing precision oncology requires accurate prediction of treatment response and accessible prediction models. To this end, we present shinyDeepDR, a user-friendly implementation of our innovative deep learning model, DeepDR, for predicting anti-cancer drug sensitivity. The web tool makes DeepDR more accessible to researchers without extensive programming experience. Using shinyDeepDR, users can upload mutation and/or gene expression data from a cancer sample (cell line or tumor) and perform two main functions: "Find Drug," which predicts the sample's response to 265 approved and investigational anti-cancer compounds, and "Find Sample," which searches for cell lines in the Cancer Cell Line Encyclopedia (CCLE) and tumors in The Cancer Genome Atlas (TCGA) with genomics profiles similar to those of the query sample to study potential effective treatments. shinyDeepDR provides an interactive interface to interpret prediction results and to investigate individual compounds. In conclusion, shinyDeepDR is an intuitive and free-to-use web tool for in silico anti-cancer drug screening.

Matrix viscoelasticity promotes liver cancer progression in the pre-cirrhotic liver.

Type 2 diabetes mellitus is a major risk factor for hepatocellular carcinoma (HCC). Changes in extracellular matrix (ECM) mechanics contribute to cancer development1,2, and increased stiffness is known to promote HCC progression in cirrhotic conditions3,4. Type 2 diabetes mellitus is characterized by an accumulation of advanced glycation end-products (AGEs) in the ECM; however, how this affects HCC in non-cirrhotic conditions is unclear. Here we find that, in patients and animal models, AGEs promote changes in collagen architecture and enhance ECM viscoelasticity, with greater viscous dissipation and faster stress relaxation, but not changes in stiffness. High AGEs and viscoelasticity combined with oncogenic ß-catenin signalling promote HCC induction, whereas inhibiting AGE production, reconstituting the AGE clearance receptor AGER1 or breaking AGE-mediated collagen cross-links reduces viscoelasticity and HCC growth. Matrix analysis and computational modelling demonstrate that lower interconnectivity of AGE-bundled collagen matrix, marked by shorter fibre length and greater heterogeneity, enhances viscoelasticity. Mechanistically, animal studies and 3D cell cultures show that enhanced viscoelasticity promotes HCC cell proliferation and invasion through an integrin-ß1-tensin-1-YAP mechanotransductive pathway. These results reveal that AGE-mediated structural changes enhance ECM viscoelasticity, and that viscoelasticity can promote cancer progression in vivo, independent of stiffness.

Restoring glucose balance: Conditional HMGB1 knockdown mitigates hyperglycemia in a Streptozotocin induced mouse model.

Diabetes mellitus (DM) poses a significant global health burden, with hyperglycemia being a primary contributor to complications and high morbidity associated with this disorder. Existing glucose management strategies have shown suboptimal effectiveness, necessitating alternative approaches. In this study, we explored the role of high mobility group box 1 (HMGB1) in hyperglycemia, a protein implicated in initiating inflammation and strongly correlated with DM onset and progression. We hypothesized that HMGB1 knockdown will mitigate hyperglycemia severity and enhance glucose tolerance. To test this hypothesis, we utilized a novel inducible HMGB1 knockout (iHMGB1 KO) mouse model exhibiting systemic HMGB1 knockdown. Hyperglycemic phenotype was induced using low dose streptozotocin (STZ) injections, followed by longitudinal glucose measurements and oral glucose tolerance tests to evaluate the effect of HMGB1 knockdown on glucose metabolism. Our findings showed a substantial reduction in glucose levels and enhanced glucose tolerance in HMGB1 knockdown mice. Additionally, we performed RNA sequencing analyses, which identified potential alternations in genes and molecular pathways within the liver and skeletal muscle tissue that may account for the in vivo phenotypic changes observed in hyperglycemic mice following HMGB1 knockdown. In conclusion, our present study delivers the first direct evidence of a causal relationship between systemic HMGB1 knockdown and hyperglycemia in vivo, an association that had remained unexamined prior to this research. This discovery positions HMGB1 knockdown as a potentially efficacious therapeutic target for addressing hyperglycemia and, by extension, the DM epidemic. Furthermore, we have revealed potential underlying mechanisms, establishing the essential groundwork for subsequent in-depth mechanistic investigations focused on further elucidating and harnessing the promising therapeutic potential of HMGB1 in DM management.

Battle of the biopsies: Role of tissue and liquid biopsy in hepatocellular carcinoma.

The diagnosis and management of hepatocellular carcinoma (HCC) have improved significantly in recent years. With the introduction of immunotherapy-based combination therapy, there has been a notable expansion in treatment options for patients with unresectable HCC. Simultaneously, innovative molecular tests for early detection and management of HCC are emerging. This progress prompts a key question: as liquid biopsy techniques rise in prominence, will they replace traditional tissue biopsies, or will both techniques remain relevant? Given the ongoing challenges of early HCC detection, including issues with ultrasound sensitivity, accessibility, and patient adherence to surveillance, the evolution of diagnostic techniques is more relevant than ever. Furthermore, the accurate stratification of HCC is limited by the absence of reliable biomarkers which can predict response to therapies. While the advantages of molecular diagnostics are evident, their potential has not yet been fully harnessed, largely because tissue biopsies are not routinely performed for HCC. Liquid biopsies, analysing components such as circulating tumour cells, DNA, and extracellular vesicles, provide a promising alternative, though they are still associated with challenges related to sensitivity, cost, and accessibility. The early results from multi-analyte liquid biopsy panels are promising and suggest they could play a transformative role in HCC detection and management; however, comprehensive clinical validation is still ongoing. In this review, we explore the challenges and potential of both tissue and liquid biopsy, highlighting that these diagnostic methods, while distinct in their approaches, are set to jointly reshape the future of HCC management.

Defining spatiotemporal gene modules in liver regeneration using Analytical Dynamic Visual Spatial Omics Representation (ADViSOR).

BACKGROUND: The liver is the only organ with the ability to regenerate following surgical or toxicant insults, and partial hepatectomy serves as an experimental model of liver regeneration (LR). Dynamic changes in gene expression occur from the periportal to pericentral regions of the liver following partial hepatectomy; thus, spatial transcriptomics, combined with a novel computational pipeline (ADViSOR [Analytic Dynamic Visual Spatial Omics Representation]), was employed to gain insights into the spatiotemporal molecular underpinnings of LR. METHODS: ADViSOR, comprising Time-Interval Principal Component Analysis and sliding dynamic hypergraphs, was applied to spatial transcriptomics data on 100 genes assayed serially through LR, including key components of the Wnt/ß-catenin pathway at critical timepoints after partial hepatectomy. RESULTS: This computational pipeline identified key functional modules demonstrating cell signaling and cell-cell interactions, inferring shared regulatory mechanisms. Specifically, ADViSOR analysis suggested that macrophage-mediated inflammation is a critical component of early LR and confirmed prior studies showing that Ccnd1, a hepatocyte proliferative gene, is regulated by the Wnt/ß-catenin pathway. These findings were subsequently validated through protein localization, which provided further confirmation and novel insights into the spatiotemporal changes in the Wnt/ß-catenin pathway during LR. CONCLUSIONS: Thus, ADViSOR may yield novel insights in other complex, spatiotemporal contexts.

Huntingtin loss in hepatocytes is associated with altered metabolism, adhesion, and liver zonation.

Huntington's disease arises from a toxic gain of function in the huntingtin (HTT) gene. As a result, many HTT-lowering therapies are being pursued in clinical studies, including those that reduce HTT RNA and protein expression in the liver. To investigate potential impacts, we characterized molecular, cellular, and metabolic impacts of chronic HTT lowering in mouse hepatocytes. Lifelong hepatocyte HTT loss is associated with multiple physiological changes, including increased circulating bile acids, cholesterol and urea, hypoglycemia, and impaired adhesion. HTT loss causes a clear shift in the normal zonal patterns of liver gene expression, such that pericentral gene expression is reduced. These alterations in liver zonation in livers lacking HTT are observed at the transcriptional, histological, and plasma metabolite levels. We have extended these phenotypes physiologically with a metabolic challenge of acetaminophen, for which the HTT loss results in toxicity resistance. Our data reveal an unexpected role for HTT in regulating hepatic zonation, and we find that loss of HTT in hepatocytes mimics the phenotypes caused by impaired hepatic ß-catenin function.

A Novel Transgenic Mouse Model Implicates Sirt2 as a Promoter of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer deaths globally. Incidence rates are steadily increasing, creating an unmet need for new therapeutic options. Recently, the inhibition of sirtuin-2 (Sirt2) was proposed as a potential treatment for HCC, despite contradictory findings of its role as both a tumor promoter and suppressor in vitro. Sirt2 functions as a lysine deacetylase enzyme. However, little is known about its biological influence, despite its implication in several age-related diseases. This study evaluated Sirt2's role in HCC in vivo using an inducible c-MYC transgene in Sirt2+/+ and Sirt2-/- mice. Sirt2-/- HCC mice had smaller, less proliferative, and more differentiated liver tumors, suggesting that Sirt2 functions as a tumor promoter in this context. Furthermore, Sirt2-/- HCCs had significantly less c-MYC oncoprotein and reduction in c-MYC nuclear localization. The RNA-seq showed that only three genes were significantly dysregulated due to loss of Sirt2, suggesting the underlying mechanism is due to Sirt2-mediated changes in the acetylome, and that the therapeutic inhibition of Sirt2 would not perturb the oncogenic transcriptome. The findings of this study suggest that Sirt2 inhibition could be a promising molecular target for slowing HCC growth.

Loss of TAZ after YAP deletion severely impairs foregut development and worsens cholestatic hepatocellular injury.

BACKGROUND: We previously showed that loss of yes-associated protein 1 (YAP) in early liver development (YAPKO) leads to an Alagille syndrome-like phenotype, with failure of intrahepatic bile duct development, severe cholestasis, and chronic hepatocyte adaptations to reduce liver injury. TAZ, a paralog of YAP, was significantly upregulated in YAPKO hepatocytes and interacted with TEA domain family member (TEAD) transcription factors, suggesting possible compensatory activity. METHODS: We deleted both Yap1 and Wwtr1 (which encodes TAZ) during early liver development using the Foxa3 promoter to drive Cre expression, similar to YAPKO mice, resulting in YAP/TAZ double knockout (DKO) and YAPKO with TAZ heterozygosity (YAPKO TAZHET). We evaluated these mice using immunohistochemistry, serum biochemistry, bile acid profiling, and RNA sequencing. RESULTS: DKO mice were embryonic lethal, but their livers were similar to YAPKO, suggesting an extrahepatic cause of death. Male YAPKO TAZHET mice were also embryonic lethal, with insufficient samples to determine the cause. However, YAPKO TAZHET females survived and were phenotypically similar to YAPKO mice, with increased bile acid hydrophilicity and similar global gene expression adaptations but worsened the hepatocellular injury. TAZ heterozygosity in YAPKO impacted the expression of canonical YAP targets Ctgf and Cyr61, and we found changes in pathways regulating cell division and inflammatory signaling correlating with an increase in hepatocyte cell death, cell cycling, and macrophage recruitment. CONCLUSIONS: YAP loss (with or without TAZ loss) aborts biliary development. YAP and TAZ play a codependent critical role in foregut endoderm development outside the liver, but they are not essential for hepatocyte development. TAZ heterozygosity in YAPKO livers increased cell cycling and inflammatory signaling in the setting of chronic injury, highlighting genes that are especially sensitive to TAZ regulation.

Huntingtin loss in hepatocytes is associated with altered metabolism, adhesion, and liver zonation.

Huntington's disease arises from a toxic gain of function in the huntingtin ( HTT ) gene. As a result, many HTT-lowering therapies are being pursued in clinical studies, including those that reduce HTT RNA and protein expression in the liver. To investigate potential impacts, we characterized molecular, cellular, and metabolic impacts of chronic HTT lowering in mouse hepatocytes. Lifelong hepatocyte HTT loss is associated with multiple physiological changes, including increased circulating bile acids, cholesterol and urea, hypoglycemia, and impaired adhesion. HTT loss causes a clear shift in the normal zonal patterns of liver gene expression, such that pericentral gene expression is reduced. These alterations in liver zonation in livers lacking HTT are observed at the transcriptional, histological and plasma metabolite level. We have extended these phenotypes physiologically with a metabolic challenge of acetaminophen, for which the HTT loss results in toxicity resistance. Our data reveal an unexpected role for HTT in regulating hepatic zonation, and we find that loss of HTT in hepatocytes mimics the phenotypes caused by impaired hepatic ß-catenin function.

Lysosomal mitochondrial interaction promotes tumor growth in squamous cell carcinoma of the head and neck.

Tumor growth and proliferation are regulated by numerous mechanisms. Communication between intracellular organelles has recently been shown to regulate cellular proliferation and fitness. The way lysosomes and mitochondria communicate with each other (lysosomal/mitochondrial interaction) is emerging as a major determinant of tumor proliferation and growth. About 30% of squamous carcinomas (including squamous cell carcinoma of the head and neck, SCCHN) overexpress TMEM16A, a calcium-activated chloride channel, which promotes cellular growth and negatively correlates with patient survival. TMEM16A has recently been shown to drive lysosomal biogenesis, but its impact on mitochondrial function is unclear. Here, we show that (1) patients with high TMEM16A SCCHN display increased mitochondrial content specifically complex I; (2) In vitro and in vivo models uniquely depend on mitochondrial complex I activity for growth and survival; (3) ß-catenin/NRF2 signaling is a critical linchpin that drives mitochondrial biogenesis, and (4) mitochondrial complex I and lysosomal function are codependent for proliferation. Taken together, our data demonstrate that LMI drives tumor proliferation and facilitates a functional interaction between lysosomes and mitochondria. Therefore, inhibition of LMI may serve as a therapeutic strategy for patients with SCCHN.

TMEM16A partners with mTOR to influence pathways of cell survival, proliferation, and migration in cholangiocarcinoma.

Expression of transmembrane protein 16 A (TMEM16A), a calcium activated chloride channel, is elevated in some human cancers and impacts tumor cell proliferation, metastasis, and patient outcome. Evidence presented here uncovers a molecular synergy between TMEM16A and mechanistic/mammalian target of rapamycin (mTOR), a serine-threonine kinase that is known to promote cell survival and proliferation in cholangiocarcinoma (CCA), a lethal cancer of the secretory cells of bile ducts. Analysis of gene and protein expression in human CCA tissue and CCA cell line detected elevated TMEM16A expression and Cl- channel activity. The Cl- channel activity of TMEM16A impacted the actin cytoskeleton and the ability of cells to survive, proliferate, and migrate as revealed by pharmacological inhibition studies. The basal activity of mTOR, too, was elevated in the CCA cell line compared with the normal cholangiocytes. Molecular inhibition studies provided further evidence that TMEM16A and mTOR were each able to influence the regulation of the other's activity or expression respectively. Consistent with this reciprocal regulation, combined TMEM16A and mTOR inhibition produced a greater loss of CCA cell survival and migration than their individual inhibition alone. Together these data reveal that the aberrant TMEM16A expression and cooperation with mTOR contribute to a certain advantage in CCA.NEW & NOTEWORTHY This study points to the dysregulation of transmembrane protein 16 A (TMEM16A) expression and activity in cholangiocarcinoma (CCA), the inhibition of which has functional consequences. Dysregulated TMEM16A exerts an influence on the regulation of mechanistic/mammalian target of rapamycin (mTOR) activity. Moreover, the reciprocal regulation of TMEM16A by mTOR demonstrates a novel connection between these two protein families. These findings support a model in which TMEM16A intersects the mTOR pathway to regulate cell cytoskeleton, survival, proliferation, and migration in CCA.