Etiology-independent activation of the LTß-LTßR-RELB axis drives aggressiveness and predicts poor prognosis in HCC.

BACKGROUND AND AIMS: HCC is the most common primary liver tumor, with an increasing incidence worldwide. HCC is a heterogeneous malignancy and usually develops in a chronically injured liver. The NF-κB signaling network consists of a canonical and a noncanonical branch. Activation of canonical NF-κB in HCC is documented. However, a functional and clinically relevant role of noncanonical NF-κB and its downstream effectors is not established. APPROACH AND RESULTS: Four human HCC cohorts (total n = 1462) and 4 mouse HCC models were assessed for expression and localization of NF-κB signaling components and activating ligands. In vitro , NF-κB signaling, proliferation, and cell death were measured, proving a pro-proliferative role of v-rel avian reticuloendotheliosis viral oncogene homolog B (RELB) activated by means of NF-κB-inducing kinase. In vivo , lymphotoxin beta was identified as the predominant inducer of RELB activation. Importantly, hepatocyte-specific RELB knockout in a murine HCC model led to a lower incidence compared to controls and lower maximal tumor diameters. In silico , RELB activity and RELB-directed transcriptomics were validated on the The Cancer Genome Atlas HCC cohort using inferred protein activity and Gene Set Enrichment Analysis. In RELB-active HCC, pathways mediating proliferation were significantly activated. In contrast to v-rel avian reticuloendotheliosis viral oncogene homolog A, nuclear enrichment of noncanonical RELB expression identified patients with a poor prognosis in an etiology-independent manner. Moreover, RELB activation was associated with malignant features metastasis and recurrence. CONCLUSIONS: This study demonstrates a prognostically relevant, etiology-independent, and cross-species consistent activation of a lymphotoxin beta/LTßR/RELB axis in hepatocarcinogenesis. These observations may harbor broad implications for HCC, including possible clinical exploitation.

Identification of BCL-XL as highly active survival factor and promising therapeutic target in colorectal cancer.

Since metastatic colorectal cancer (CRC) is a leading cause of cancer-related death, therapeutic approaches overcoming primary and acquired therapy resistance are an urgent medical need. In this study, the efficacy and toxicity of high-affinity inhibitors targeting antiapoptotic BCL-2 proteins (BCL-2, BCL-XL, and MCL-1) were evaluated. By RNA sequencing analysis of a pan-cancer cohort comprising >1500 patients and subsequent prediction of protein activity, BCL-XL was identified as the only antiapoptotic BCL-2 protein that is overactivated in CRC. Consistently, pharmacologic and genetic inhibition of BCL-XL induced apoptosis in human CRC cell lines. In a combined treatment approach, targeting BCL-XL augmented the efficacy of chemotherapy in vitro, in a murine CRC model, and in human ex vivo derived CRC tissue cultures. Collectively, these data show that targeting of BCL-XL is efficient and safe in preclinical CRC models, observations that pave the way for clinical translation.

MCL1 Is Required for Maintenance of Intestinal Homeostasis and Prevention of Carcinogenesis in Mice.

BACKGROUND & AIMS: Intestinal epithelial homeostasis depends on a tightly regulated balance between intestinal epithelial cell (IEC) death and proliferation. While the disruption of several IEC death regulating factors result in intestinal inflammation, the loss of the anti-apoptotic BCL2 family members BCL2 and BCL2L1 has no effect on intestinal homeostasis in mice. We investigated the functions of the antiapoptotic protein MCL1, another member of the BCL2 family, in intestinal homeostasis in mice. METHODS: We generated mice with IEC-specific disruption of Mcl1 (Mcl1ΔIEC mice) or tamoxifen-inducible IEC-specific disruption of Mcl1 (i-Mcl1ΔIEC mice); these mice and mice with full-length Mcl1 (controls) were raised under normal or germ-free conditions. Mice were analyzed by endoscopy and for intestinal epithelial barrier permeability. Intestinal tissues were analyzed by histology, in situ hybridization, proliferation assays, and immunoblots. Levels of calprotectin, a marker of intestinal inflammation, were measured in intestinal tissues and feces. RESULTS: Mcl1ΔIEC mice spontaneously developed apoptotic enterocolopathy, characterized by increased IEC apoptosis, hyperproliferative crypts, epithelial barrier dysfunction, and chronic inflammation. Loss of MCL1 retained intestinal crypts in a hyperproliferated state and prevented the differentiation of intestinal stem cells. Proliferation of intestinal stem cells in MCL1-deficient mice required WNT signaling and was associated with DNA damage accumulation. By 1 year of age, Mcl1ΔIEC mice developed intestinal tumors with morphologic and genetic features of human adenomas and carcinomas. Germ-free housing of Mcl1ΔIEC mice reduced markers of microbiota-induced intestinal inflammation but not tumor development. CONCLUSION: The antiapoptotic protein MCL1, a member of the BCL2 family, is required for maintenance of intestinal homeostasis and prevention of carcinogenesis in mice. Loss of MCL1 results in development of intestinal carcinomas, even under germ-free conditions, and therefore does not involve microbe-induced chronic inflammation. Mcl1ΔIEC mice might be used to study apoptotic enterocolopathy and inflammatory bowel diseases.

Knockdown of Atg7 Induces Nuclear-LC3 Dependent Apoptosis and Augments Chemotherapy in Colorectal Cancer Cells.

Autophagy is a catabolic process that enables cells to degrade obsolete content and refuel energy depots. In colorectal cancer (CRC) autophagy has been shown to promote tumorigenesis through energy delivery in the condition of uncontrolled proliferation. With this study, we aimed at evaluating whether autophagy sustains CRC cell viability and if it impacts therapy resistance. Initially, a colorectal cancer tissue micro array, containing mucosa (n = 10), adenoma (n = 18) and adenocarcinoma (n = 49) spots, was stained for expression of essential autophagy proteins LC3b, Atg7, p62 and Beclin-1. Subsequently, central autophagy proteins were downregulated in CRC cells using siRNA technology. Viability assays, flow cytometry and immunoblotting were performed and three-dimensional cell culture was utilized to study autophagy in a tissue mimicking environment. In our study we found an upregulation of Atg7 in CRC. Furthermore, we identified Atg7 as crucial factor within the autophagy network for CRC cell viability. Its disruption induced cell death via triggering apoptosis and in combination with conventional chemotherapy it exerted synergistic effects in inducing CRC cell death. Cell death was strictly dependent on nuclear LC3b, since simultaneous knockdown of Atg7 and LC3b completely restored viability. This study unravels a novel cell death preventing function of Atg7 in interaction with LC3b, thereby unmasking a promising therapeutic target in CRC.

Rationally derived drug combinations with the novel Mcl-1 inhibitor EU-5346 in breast cancer.

PURPOSE: Recent studies have emphasized a key role for the anti-apoptotic Bcl-2 family member Mcl-1 in conferring tumor cell survival and drug resistance in breast cancer (BC). Mcl-1 inhibitors, such as the BH3-mimetic EU-5346, therefore represent an exciting new class of targeting agents and are a current focus of widespread cancer-drug development efforts. METHODS: ONCOMINE analysis was utilized to compare expression profiles of Bcl-2 family members across all major BC subgroups. Potential toxicities of EU-5346 were evaluated using iPS-generated cardiomyocytes, blood cells and astrocytes. The anti-BC cell activity of EU-5346-based therapies was evaluated using [3H]-thymidine uptake and spheroid-forming assays as well as immunoblotting and the Chou-Talalay method. Protein level-based activity of EU-5346, the specific anti-Bcl-2 inhibitor ABT-199 and the specific anti-Bcl-xL inhibitor WEHI-539 was verified in Mcl-1Δ/null versus Mcl-1wt/wt MEFs. RESULTS: We previously demonstrated significant anti-tumor activity of EU-5346 in all BC subtypes. Our present results go further and suggest that EU-5346 may induce limited adverse events such as cardiotoxicity, hematotoxicity, and neurotoxicity, frequently observed with other BH3 mimetics. As demonstrated by our mathematical scoring model, the prediction of EU-5643-induced IC50 not only relies on the protein level of Mcl-1 but also on Bak, Bim, and Noxa. Synergistic anti-BC activity of low-dose EU-5346 with the BH3 mimetics ABT-199 or WEHI-539 was observed only in those BC cells expressing Bcl-2 or Bcl-xL, respectively. Similarly, when combined with tamoxifen or trastuzumab, low-dose EU-5346 induced significant anti-BC activity in hormone receptor positive or Her2-positive BC cells, respectively. Finally, EU-5346 in combination with paclitaxel induced synergistic anti-BC activity in both paclitaxel-sensitive and paclitaxel-resistant TNBC cells. CONCLUSION: These data strongly support the further clinical development of EU-5346 to improve BC patient survival.

Nuclear Translocation of RELB Is Increased in Diseased Human Liver and Promotes Ductular Reaction and Biliary Fibrosis in Mice.

BACKGROUND & AIMS: Cholangiocyte proliferation and ductular reaction contribute to the onset and progression of liver diseases. Little is known about the role of the transcription factor nuclear factor-κB (NF-κB) in this process. We investigated the activities of the RELB proto-oncogene NF-κB subunit in human cholangiocytes and in mouse models of liver disease characterized by a ductular reaction. METHODS: We obtained liver tissue samples from patients with primary sclerosing cholangitis, primary biliary cholangitis, hepatitis B or C virus infection, autoimmune hepatitis, alcoholic liver disease, or without these diseases (controls) from a tissue bank in Germany. Tissues were analyzed by immunohistochemistry for levels of RELB and lymphotoxin ß (LTB). We studied mice with liver parenchymal cell (LPC)-specific disruption of the cylindromatosis (CYLD) lysine 63 deubiquitinase gene (Cyld), with or without disruption of Relb (CyldΔLPC mice and Cyld/RelbΔLPC mice) and compared them with C57BL/6 mice (controls). Mice were fed 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or standard chow diets to induce biliary injury or were given injections of CCl4 to induce non-cholestatic liver fibrosis. Liver tissues were analyzed by histology, immunohistochemistry, immunoblots, in situ hybridization, and quantitative real-time polymerase chain reaction. Cholangiocytes were isolated from normal human liver, incubated with LTB receptor agonist, and transfected with small interfering RNAs to knock down RELB. RESULTS: In liver tissues from patients with primary sclerosing cholangitis, primary biliary cholangitis, chronic infection with hepatitis B or C virus, autoimmune hepatitis, or alcoholic liver disease, we detected increased nuclear translocation of RELB and increased levels of LTB in cholangiocytes that formed reactive bile ducts compared with control liver tissues. Human cholangiocytes, but not those with RELB knockdown, proliferated with exposure to LTB. The phenotype of CyldΔLPC mice, which included ductular reaction, oval cell activation, and biliary fibrosis, was completely lost from Cyld/RelbΔLPC mice. Compared with livers from control mice, livers from CyldΔLPC mice (but not Cyld/RelbΔLPC mice) had increased levels of mRNAs encoding cytokines (LTB; CD40; and tumor necrosis factor superfamily [TNFSF] members TNFSF11 [RANKL], TNFSF13B [BAFF], and TNFSF14 [LIGHT]) produced by reactive cholangiocytes. However, these strains of mice developed similar levels of liver fibrosis in response to CCl4 exposure. CyldΔLPC mice and Cyld/RelbΔLPC mice had improved liver function on the DDC diet compared with control mice fed the DDC diet. CONCLUSION: Reactive bile ducts in patients with chronic liver diseases have increased levels of LTB and nuclear translocation of RELB. RELB is required for the ductular reaction and development of biliary fibrosis in CyldΔLPC mice. Deletion of RELB and CYLD from LPCs protects mice from DDC-induced cholestatic liver fibrosis.

Survival of Hepatocellular Carcinoma Patients Treated with Sorafenib beyond Progression.

BACKGROUND/AIM: Sorafenib leads to improved survival in advanced hepatocellular carcinoma (HCC) patients. Continuation of sorafenib beyond progression has been a possible treatment strategy when further approved therapeutic agents are lacking. METHODS: We performed a retrospective analysis of all HCC patients at our institution with documented disease progression under treatment with sorafenib. Overall survival (OS) from start of sorafenib treatment was compared between patients who received sorafenib for > 3 weeks beyond progression (group 1) and those who discontinued sorafenib ≤3 weeks after progression (group 2). Group 1 was further subdivided into those patients who received sorafenib for > 3 months (group 1a) and those who received it for ≤3 months (group 1b). RESULTS: A total of 71 patients were analyzed. Median OS for all patients was 15.4 months. OS in group 1 (15.6 months) and 2 (13.0 months) was similar (p = 0.90). Patients in group 1a showed significantly prolonged median OS (19.7 months) compared to that of patients in group 1b (13.6 months, p = 0.004), and they showed a trend towards prolonged OS compared to group 2 (p = 0.126). For patients with a poor prognosis according to their Child-Pugh stage, performance status, alpha-fetoprotein, and response to prior sorafenib treatment, OS was significantly prolonged in group 1 versus group 2 (12.1 vs. 6.4 months, p = 0.019). CONCLUSION: In HCC patients, continuing sorafenib beyond progression for > 3 months is associated with improved survival compared to discontinuing sorafenib within 3 months. Furthermore, patients with a poor prognosis who continue sorafenib beyond progression in general show significantly prolonged survival.

An undifferentiated carcinoma at Klatskin-position with long-term complete remission after chemotherapy.

BACKGROUND: Neoplasms anatomically adjacent to the bile duct usually derive from malignantly transformed cholangiocytes forming cholangiocarcinoma (CCA). CCAs are divided in extrahepatic (eCCA) and intrahepatic (iCCA) tumors. Patients with irresectable CCAs are treated with systemic chemotherapy and have an unfavorable prognosis with a median survival of about one year. Here, we report a case of an undifferentiated carcinoma in Klatskin-position with long-term remission after systemic chemotherapy. CASE PRESENTATION: A 65-year-old Caucasian male presented with painless jaundice caused by an undifferentiated carcinoma in Klatskin-position (Type IIIb). Alpha fetoprotein (AFP; 3675 IU/mL) and carbohydrate antigen 19-9 (CA 19-9; 183 U/ml) were elevated. An exploratory laparotomy was carried out, but the patient was found to be irresectable due to severe fibrosis caused by biliary obstruction. Histology showed an undifferentiated carcinoma with high proliferation rate, and the patient was therefore subjected to poly-chemotherapy treatment according to the FOLFOX6-protocol. During therapy, AFP decreased to normal. Subsequent CT scans and ERC revealed a complete remission. Four years past initial diagnosis, a new suspicious lesion in the liver is visible on MRT; however, AFP and CA 19-9 are still in the normal range. CONCLUSIONS: Our case demonstrates that histopathological defined diagnosis may significantly inform therapeutic decision-making in irresectable cholangiocarcinoma even in regard to conventional systemic therapy. In case of an undifferentiated carcinoma poly-chemotherapy may provide significant success.

PICCA study: panitumumab in combination with cisplatin/gemcitabine chemotherapy in KRAS wild-type patients with biliary cancer-a randomised biomarker-driven clinical phase II AIO study.

BACKGROUND: Combination chemotherapy has shown benefit in the treatment of biliary cancer and further improvements might be achieved by the addition of a biological agent. We report here the effect of chemotherapy with the monoclonal EGFR antibody panitumumab as therapy for KRAS wild-type biliary cancer. PATIENTS AND METHODS: Patients with advanced biliary tract cancer were randomised (2:1) to receive cisplatin 25 mg/m2 and gemcitabine 1000 mg/m2 on day 1 and day 8/q3w with (arm A) or without panitumumab (arm B; 9 mg/kg BW, i.v q3w). The primary end-point was the evaluation of progression-free survival (PFS) at 6 months. Secondary end-points included objective response rate (ORR), overall survival (OS), and toxicity. In addition, a post hoc assessment of genetic alterations was performed. Finally, we performed a meta-analysis of trials with chemotherapy with and without EGFR antibodies. RESULTS: Sixty-two patients were randomised in arm A and 28 patients in arm B. Patients received 7 treatment cycles in median (1-35) with a median treatment duration of 4.7 months (141 days, 8-765). PFS rate at 6 months was 54% in patients treated with cisplatin/gemcitabine and panitumumab but was 73% in patients treated with cisplatin/gemcitabine without antibody, respectively. Secondary end-points were an ORR of 45% in treatment arm A compared with 39% receiving treatment B and a median OS of 12.8 months (arm A) and of 20.1 months (arm B), respectively. In contrast to the p53-status, genetic alterations in IDH1/2 were linked to a high response after chemotherapy and prolonged survival. In accordance with our results, the meta-analysis of 12 trials did not reveal a survival advantage for patients treated with EGFR antibodies compared with chemotherapy alone. CONCLUSIONS: Panitumumab in combination with chemotherapy does not improve ORR, PFS and OS in patients with KRAS wild-type, advanced biliary cancer. Genetic profiling should be included in CCA trials to identify and validate predictive and prognostic biomarkers. CLINICAL TRIALS NUMBER: The trial was registered with NCT01320254.

Phase I study of tomuzotuximab, a glycoengineered therapeutic antibody against the epidermal growth factor receptor, in patients with advanced carcinomas.

BACKGROUND: Changes in glycosylation of the constant domain (Fc) of monoclonal antibodies (mAbs) enhance antibody-dependent cell-mediated cytotoxicity independently of downstream effects following receptor blockade by the antibody, thus extending their indication. We investigated the safety, pharmacokinetics, pharmacodynamics and antitumour activity of tomuzotuximab, an IgG1 glycoengineered mAb against the epidermal growth factor receptor with enhanced tumour cytotoxicity in a phase I dose-escalation study (NTC01222637). PATIENTS AND METHODS: Forty-one patients with advanced solid tumours refractory to standard therapies received tomuzotuximab weekly (12-1370 mg) or two-weekly (990 mg) on a three-plus-three dose escalation design. RESULTS: A maximum tolerated dose was not reached. The most frequent treatment-related adverse events were infusion-related reactions in 31 (76%) patients (grade 3, 12%), mainly confined to the first dose, and skin toxicities (grade 1 or 2) in 30 (73%) patients. Hypomagnesaemia was observed in 9 out of 23 evaluable patients (39%). Similar to cetuximab, tomuzotuximab concentrations increased proportionally to dose from doses≥480 mg with a median terminal half life (t½) of 82 hours, range 55-113 hours. Antitumour activity included one complete response ongoing since more than 4.5 years in a patient with non-small-cell lung cancer and one partial response lasting 353 days in a patient with colorectal cancer. Twelve patients achieved stable disease (median, 166 days, range, 71-414 days) and two patients had prolonged control (>1 year) of their non-measurable disease. CONCLUSION: Tomuzotuximab was safe and showed promising antitumour activity in heavily pretreated patients with advanced metastatic disease. A phase IIb trial of chemotherapy and weekly tomuzotuximab or cetuximab followed with maintenance therapy with the corresponding mAb in patients with recurrent or metastatic head and neck squamous cell carcinoma is ongoing.

A Dual Role of Caspase-8 in Triggering and Sensing Proliferation-Associated DNA Damage, a Key Determinant of Liver Cancer Development.

Concomitant hepatocyte apoptosis and regeneration is a hallmark of chronic liver diseases (CLDs) predisposing to hepatocellular carcinoma (HCC). Here, we mechanistically link caspase-8-dependent apoptosis to HCC development via proliferation- and replication-associated DNA damage. Proliferation-associated replication stress, DNA damage, and genetic instability are detectable in CLDs before any neoplastic changes occur. Accumulated levels of hepatocyte apoptosis determine and predict subsequent hepatocarcinogenesis. Proliferation-associated DNA damage is sensed by a complex comprising caspase-8, FADD, c-FLIP, and a kinase-dependent function of RIPK1. This platform requires a non-apoptotic function of caspase-8, but no caspase-3 or caspase-8 cleavage. It may represent a DNA damage-sensing mechanism in hepatocytes that can act via JNK and subsequent phosphorylation of the histone variant H2AX.

Liver cancers with stem/progenitor-cell features - a rare chemotherapy-sensitive malignancy.

Primary liver tumors are a heterogeneous group of malignancies. Besides classical hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC), combined and intermediate forms of liver cancer exist and can express stem-cell markers like nuclear cell adhesion molecule (NCAM-1/CD56), c-kit (CD117) or epithelial cell adhesion molecule (EpCAM) together with high proliferative activity. Liver tumors with progenitor-cell features are associated with an unfavorable prognosis, but the phenotype has not resulted in therapeutic consequences so far. We report three patients with liver cancers with stem/progenitor-cell features that responded exceptionally well to chemotherapy. These encouraging results indicate that the identification of liver cancer with stem/progenitor-cell phenotype in a patient´s tumor might justify an attempt to treat the patient with chemotherapy. Further case studies and finally clinical trials will be necessary to determine the optimal treatment for patients with this rare form of liver cancer.

Activation of silent mating type information regulation 2 homolog 1 by human chorionic gonadotropin exerts a therapeutic effect on hepatic injury and inflammation.

Incidence and prevalence of inflammatory liver diseases has increased over the last years, but therapeutic options are limited. Pregnancy induces a state of immune tolerance, which can result in spontaneous improvement of clinical symptoms of certain autoimmune diseases including autoimmune hepatitis (AIH). We investigated the immune-suppressive mechanisms of the human pregnancy hormone, chorionic gonadotropin (hCG), in the liver. hCG signaling activates silent mating type information regulation 2 homolog 1 (SIRT1), which deacetylates forkhead box o3 (FOXO3a), leading to repression of proapoptotic gene expression, because the immunosuppressive consequence attributed to the absence of caspase-3 activity of hepatocellular interleukin 16 (IL-16) is no longer processed and released. Thus, serum levels of IL-16, a key chemotactic factor for CD4+ lymphocytes, were reduced and migration to injured hepatocytes prevented. Furthermore, elevated IL-16 levels are found in the sera from patients with AIH, hepatitis B virus, hepatitis C virus, and nonalcoholic steatohepatitis. CONCLUSION: Here, we report that hCG regulates the SIRT1/FOXO3a axis in hepatocytes, resulting in immune suppression by attenuating caspase-3-dependent IL-16 processing and release, which concomitantly prevents autoaggressive T-cell infiltration of the liver. Considering the low toxicity profile of hCG in humans, interrupting the inflammatory cycle by hCG opens new perspectives for therapeutic intervention of inflammatory liver diseases. (Hepatology 2017;65:2074-2089).

Possible Mechanisms of Ethanol-Mediated Colorectal Carcinogenesis: The Role of Cytochrome P4502E1, Etheno-DNA Adducts, and the Anti-Apoptotic Protein Mcl-1.

BACKGROUND: Chronic alcohol consumption is a risk factor for colorectal cancer. The mechanisms by which ethanol (EtOH) exerts its carcinogenic effect on the colorectal mucosa are not clear and may include oxidative stress with the action of reactive oxygen species (ROS) generated through EtOH metabolism via cytochrome P4502E1 (CYP2E1) leading to carcinogenic etheno-DNA adducts. ROS may also induce apoptosis. However, the effect of chronic EtOH consumption on CYP2E1, etheno-DNA adducts as well as anti-apoptotic proteins in the colorectal mucosa of heavy drinkers without colorectal inflammation is still not known. METHODS: Rectal biopsies from 32 alcoholics (>60 g EtOH/d) and from 12 controls (<20 g EtOH/d) were histologically examined, and immunohistochemistry for CYP2E1 and etheno-DNA adducts was performed. Apoptosis (cleaved PARP) as well as anti-apoptotic proteins including Bcl-xL , Bcl-2, and Mcl-1 were immunohistochemically determined. RESULTS: No significant difference in mucosal CYP2E1 or etheno-DNA adducts was observed between alcoholics and control patients. However, CYP2E1 and etheno-DNA adducts correlated significantly when both groups were combined (p < 0.001). In addition, although apoptosis was found not to be significantly affected by EtOH, the anti-apoptotic protein Mcl-1, but neither Bcl-xL nor Bcl-2, was found to be significantly increased in heavy drinkers as compared to controls (p = 0.014). CONCLUSIONS: Although colorectal CYP2E1 was not found to be significantly increased in alcoholics, CYP2E1 correlated overall with the level of etheno-DNA adducts in the colorectal mucosa, which identifies CYP2E1 as an important factor in colorectal carcinogenesis. Most importantly, however, is the up-regulation of the anti-apoptotic protein Mcl-1 in heavy drinkers counteracting apoptosis and possibly stimulating cancer development.

Bcl-xL is an oncogenic driver in colorectal cancer.

Colorectal cancer (CRC) is the second most common malignant neoplasia in women and men worldwide. The B-cell lymphoma 2 (Bcl-2) protein family is mainly known for its pivotal role in the regulation of the mitochondrial death pathway. Anti-apoptotic Bcl-2 proteins may provide survival benefits and induce therapy resistance in cancer cells. Among anti-apoptotic Bcl-2 proteins, we found solely Bcl-xL strongly upregulated in human CRC specimens. In order to study protein function in the context of tumor initiation and progression in vivo, we generated a mouse model lacking Bcl-xL in intestinal epithelial cells (Bcl-xL(IEC-KO)). If challenged in an inflammation-driven tumor model, Bcl-xL(IEC-KO) mice showed a significantly reduced tumor burden with lower tumor numbers per animal and decreased tumor sizes. Analysis of cell death events by immunohistochemistry and immunoblotting revealed a striking increase of apoptosis in Bcl-xL-negative tumors. qRT-PCR and immunohistochemistry excluded changes in proliferative capacity and immune cell infiltration as reasons for the reduced tumor load and thereby identify apoptosis as key mechanism. Human CRC tissue was cultured ex vivo and treated with the small molecule compound ABT-737, which inhibits Bcl-xL and Bcl-2. Under ABT-737 treatment, the amount of apoptotic tumor cells significantly increased compared with controls, whereas proliferation levels remained unaltered. In summary, our findings identify Bcl-xL as a driver in colorectal tumorigenesis and cancer progression, making it a valuable target for clinical application.

Mcl-1 confers protection of Her2-positive breast cancer cells to hypoxia: therapeutic implications.

BACKGROUND: Molecular mechanisms leading to the adaptation of breast cancer (BC) cells to hypoxia are largely unknown. The anti-apoptotic Bcl-2 family member myeloid cell leukemia-1 (Mcl-1) is frequently amplified in BC; and elevated Mcl-1 levels have been correlated with poor prognosis. Here we investigated the pathophysiologic role of Mcl-1 in Her2-positive BC cells under hypoxic conditions. METHODS: RNA interference and a novel small molecule inhibitor, EU-5346, were used to examine the role of Mcl-1 in Her2-positive BC cell lines and primary BC cells (sensitive or intrinsically resistant to Her2 inhibitors) under hypoxic conditions (using a hypoxic incubation chamber). Mechanisms-of-action were investigated by RT-PCR, mitochondrial isolation, as well as immunoprecipitation/blotting analysis, and microscopy. The specificity against Mcl-1 of the novel small molecule inhibitor EU5346 was verified in Mcl-1(Δ/null) versus Mcl-1(wt/wt) Murine Embryonic Fibroblasts (MEFs). Proliferation, survival, and spheroid formation were assessed in response to Mcl-1 and Her2 inhibition. RESULTS: We demonstrate for a strong correlation between high Mcl-1 protein levels and hypoxia, predominantly in Her2-positive BC cells. Surprisingly, genetic depletion of Mcl-1 decreased Her2 and Hif-1α levels followed by inhibition of BC cell survival. In contrast, Mcl-1 protein levels were not downregulated after genetic depletion of Her2 indicating a regulatory role of Mcl-1 upstream of Her2. Indeed, Mcl-1 and Her2 co-localize within the mitochondrial fraction and form a Mcl-1/Her2- protein complex. Similar to genetically targeting Mcl-1 the novel small molecule Mcl-1 inhibitor EU-5346 induced cell death and decreased spheroid formation in Her2-positive BC cells. Of interest, EU-5346 induced ubiquitination of Mcl-1- bound Her2 demonstrating a previously unknown role for Mcl-1 to stabilize Her2 protein levels. Importantly, targeting Mcl-1 was also active in Her2-positive BC cells resistant to Her2 inhibitors, including a brain-primed Her2-positive cell line. CONCLUSION: Our data demonstrate a critical role of Mcl-1 in Her2-positive BC cell survival under hypoxic conditions and provide the preclinical framework for the therapeutic use of novel Mcl-1- targeting agents to improve patient outcome in BC.

Prolyl Hydroxylase 3 Attenuates MCL-1-Mediated ATP Production to Suppress the Metastatic Potential of Colorectal Cancer Cells.

Hypoxia is a common feature of solid tumors. Prolyl hydroxylase enzymes (PHD1-3) are molecular oxygen sensors that regulate hypoxia-inducible factor activity, but their functions in metastatic disease remain unclear. Here, we assessed the significance of PHD enzymes during the metastatic spread of colorectal cancer. PHD expression analysis in 124 colorectal cancer patients revealed that reduced tumoral expression of PHD3 correlated with increased frequency of distant metastases and poor outcome. Tumorigenicity and metastatic potential of colorectal tumor cells over and underexpressing PHD3 were investigated in orthotopic and heterotopic tumor models. PHD3 overexpression in a syngeneic tumor model resulted in fewer liver metastases, whereas PHD3 knockdown induced tumor spread. The migration of PHD3-overexpressing tumor cells was also attenuated in vitro Conversely, migratory potential and colony formation were enhanced in PHD3-deficient cells, and this phenotype was associated with enhanced mitochondrial ATP production. Furthermore, the effects of PHD3 deficiency were accompanied by increased mitochondrial expression of the BCL-2 family member, member myeloid cell leukemia sequence 1 (MCL-1), and could be reversed by simultaneous inhibition of MCL-1. MCL-1 protein expression was likewise enhanced in human colorectal tumors expressing low levels of PHD3. Therefore, we demonstrate that downregulation of PHD3 augments metastatic spread in human colorectal cancer and identify MCL-1 as a novel downstream effector of oxygen sensing. Importantly, these findings offer new insight into the possible, context-specific deleterious effects of pharmacologic PHD inhibition. Cancer Res; 76(8); 2219-30. ©2016 AACR.

Pan-Bcl-2 inhibitor Obatoclax is a potent late stage autophagy inhibitor in colorectal cancer cells independent of canonical autophagy signaling.

BACKGROUND: Colorectal cancer is the third most common malignancy in humans and novel therapeutic approaches are urgently needed. Autophagy is an evolutionarily highly conserved cellular process by which cells collect unnecessary organelles or misfolded proteins and subsequently degrade them in vesicular structures in order to refuel cells with energy. Dysregulation of the complex autophagy signaling network has been shown to contribute to the onset and progression of cancer in various models. The Bcl-2 family of proteins comprises central regulators of apoptosis signaling and has been linked to processes involved in autophagy. The antiapoptotic members of the Bcl-2 family of proteins have been identified as promising anticancer drug targets and small molecules inhibiting those proteins are in clinical trials. METHODS: Flow cytometry and colorimetric assays were used to assess cell growth and cell death. Long term 3D cell culture was used to assess autophagy in a tissue mimicking environment in vitro. RNA interference was applied to modulate autophagy signaling. Immunoblotting and q-RT PCR were used to investigate autophagy signaling. Immunohistochemistry and fluorescence microscopy were used to detect autophagosome formation and autophagy flux. RESULTS: This study demonstrates that autophagy inhibition by obatoclax induces cell death in colorectal cancer (CRC) cells in an autophagy prone environment. Here, we demonstrate that pan-Bcl-2 inhibition by obatoclax causes a striking, late stage inhibition of autophagy in CRC cells. In contrast, ABT-737, a Mcl-1 sparing Bcl-2 inhibitor, failed to interfere with autophagy signaling. Accumulation of p62 as well as Light Chain 3 (LC3) was observed in cells treated with obatoclax. Autophagy inhibition caused by obatoclax is further augmented in stressful conditions such as starvation. Furthermore, our data demonstrate that inhibition of autophagy caused by obatoclax is independent of the essential pro-autophagy proteins Beclin-1, Atg7 and Atg12. CONCLUSIONS: The objective of this study was to dissect the contribution of Bcl-2 proteins to autophagy in CRC cells and to explore the potential of Bcl-2 inhibitors for autophagy modulation. Collectively, our data argue for a Beclin-1 independent autophagy inhibition by obatoclax. Based on this study, we recommend the concept of autophagy inhibition as therapeutic strategy for CRC.

Survival analysis of proposed BCLC-B subgroups in hepatocellular carcinoma patients.

BACKGROUND & AIMS: The BCLC-staging system is used to facilitate treatment decisions in patients with hepatocellular carcinoma (HCC). Owing to the observed clinical heterogeneity of the intermediate stage BCLC-B, a subclassification was proposed taking Child-Pugh score and extended criteria for transplantation into account. Analysis of the prognostic significance of a proposed subclassification of the BCLC-B score in a European cohort of HCC patients. METHODS: Eight hundred and eighty four consecutive HCC patients were retrospectively analysed. Patients with stage BCLC-B were grouped according to the proposed subclassification. Baseline patient and tumour characteristics, therapy and overall survival were analysed. RESULTS: Two hundred and fifty four patients with stage BCLC-B were classified as B1/B2/B3 and B4 in 16.1/56.7/7.9 and 19.3%. OS compared between adjacent subgroups (B1 vs. B2, B2 vs. B3, B3 vs. B4) did not reach statistical significance. Groupwise comparison showed significant differences between B1 vs. B3 (P = 0.035), B1 vs. B4 (P = 0.006) and B2 vs. B4 (P < 0.0001). OS was significantly improved in patients undergoing OLT (P < 0.0001). Cox regression showed no significant influence of the BCLC-B substage on survival. CONCLUSIONS: No significant survival differences between subgroups were found in the retrospective analysis. We could not confirm the BCLC-B subclassification to be prognostically meaningful in our cohort. As liver function and therapy influenced survival in this study, a more refined BCLC-B subclassification has the potential to be a useful tool to better stratify treatment decisions. Further studies in larger collectives with homogenous staging and treatment strategies are warranted to confirm the prognostic significance of the proposed subclassifications.