Tumor cell integrin ß4 and tumor stroma E-/P-selectin cooperatively regulate tumor growth in vivo.

BACKGROUND: The immunological composition of the tumor microenvironment has a decisive influence on the biological course of cancer and is therefore of profound clinical relevance. In this study, we analyzed the cooperative effects of integrin ß4 (ITGB4) on tumor cells and E-/P-selectin on endothelial cells within the tumor stroma for regulating tumor growth by shaping the local and systemic immune environment. METHODS: We used several preclinical mouse models for different solid human cancer types (xenograft and syngeneic) to explore the role of ITGB4 (shRNA-mediated knockdown in tumor cells) and E-/P-selectins (knockout in mice) for tumor growth; effects on apoptosis, proliferation and intratumoral signaling pathways were determined by histological and biochemical methods and 3D in vitro experiments; changes in the intratumoral and systemic immune cell composition were determined by flow cytometry and immunohistochemistry; chemokine levels and their attracting potential were measured by ELISA and 3D invasion assays. RESULTS: We observed a very robust synergism between ITGB4 and E-/P-selectin for the regulation of tumor growth, accompanied by an increased recruitment of CD11b+ Gr-1Hi cells with low granularity (i.e., myeloid-derived suppressor cells, MDSCs) specifically into ITGB4-depleted tumors. ITGB4-depleted tumors undergo apoptosis and actively attract MDSCs, well-known to promote tumor growth in several cancers, via increased secretion of different chemokines. MDSC trafficking into tumors crucially depends on E-/P-selectin expression. Analyses of clinical samples confirmed an inverse relationship between ITGB4 expression in tumors and number of tumor-infiltrating leukocytes. CONCLUSIONS: These findings suggest a distinct vulnerability of ITGB4Lo tumors for MDSC-directed immunotherapies.

A Critical Role of the IL-22-IL-22 Binding Protein Axis in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) ranks among the five most common cancer entities worldwide and leads to hundred-thousands of deaths every year. Despite some groundbreaking therapeutical revelations during the last years, the overall prognosis remains poor. Although the immune system fights malignant transformations with a robust anti-tumor response, certain immune mediators have also been shown to promote cancer development. For example, interleukin (IL)-22 has been associated with HCC progression and worsened prognosis in multiple studies. However, the underlying mechanisms of the pathological role of IL-22-signaling as well as the role of its natural antagonist IL-22 binding protein (IL-22BP) in HCC remain elusive. Here, we corroborate the pathogenic role of IL-22 in HCC by taking advantage of two mouse models. Moreover, we observed a protective role of IL-22BP during liver carcinogenesis. While IL-22 was mainly produced by CD4+ T cells in HCC, IL-22BP was abundantly expressed by neutrophils during liver carcinogenesis. Hepatocytes could be identified as a major target of this pathological IL-22-signaling. Moreover, abrogation of IL-22 signaling in hepatocytes in IL22ra1flox/flox × AlbCre+ mice reduced STEAP4 expression-a known oncogene-in HCC in vivo. Likewise, STEAP4 expression correlated with IL22 levels in human HCC samples, but not in healthy liver specimens. In conclusion, these data encourage the development of therapeutical approaches that target the IL-22-IL-22BP axis in HCC.

Truncated O-GalNAc glycans impact on fundamental signaling pathways in pancreatic cancer.

Truncated O-GalNAc glycosylation is an important feature of pancreatic ductal adenocarcinomas (PDAC) and expression of truncated O-GalNAc glycans is strongly associated with decreased survival and poor prognosis. It has been proven, that aberrant O-GalNAc glycosylation influence PDAC signaling to promote oncogenic properties, but elucidation of the influence of truncated O-GalNAc glycosylation on different signaling molecules has just been started. We herein elucidated the impact of aberrant O-GalNAc glycosylation on two important PDAC signaling pathways, namely AKT/mTOR and RAS/MAPK. In PDAC cells expressing truncated O-GalNAc glycans, we identified differentially expressed proteins associated with AKT/mTOR and RAS/MAPK pathways using quantitative proteomics. Since AKT, a key-signaling molecule in PDAC, was among the identified proteins, we analyzed AKT and found a strikingly enhanced S473 phosphorylation and identified a previously unknown O-GalNAc-modification. Consecutive analysis of COSMC knockdowns in PDAC revealed strong effects on AKT upstream and downstream effector molecules. Interestingly, truncated O-GalNAc glycans could facilitate an mTORC1 inhibitor resistance using AZD8055. In addition, as AKT/mTOR pathway has extensive cross talks with RAS/MAPK pathway we analyzed the pathways and found it negatively regulated. Finally, we found that the expression of epithelial-mesenchymal-transition markers, key features of aggressive PDACs cells, are enhanced and truncated O-GalNAc glycans enhance pancreatic cancer cell growth in a xenograft mouse model. Our study demonstrates that truncated O-GalNAc glycans have a strong impact on AKT/mTOR and RAS/MAPK signaling pathways, are modulated by EGF or IGF-1 signaling and should be considered for targeted therapy of these pathways in PDAC.

Temporomandibular Joint Osteoarthritis: Regenerative Treatment by a Stem Cell Containing Advanced Therapy Medicinal Product (ATMP)-An In Vivo Animal Trial.

Temporomandibular joint osteoarthritis (TMJ-OA) is a chronic degenerative disease that is often characterized by progressive impairment of the temporomandibular functional unit. The aim of this randomized controlled animal trial was a comparative analysis regarding the chondroregenerative potency of intra-articular stem/stromal cell therapy. Four weeks after combined mechanical and biochemical osteoarthritis induction in 28 rabbits, therapy was initiated by a single intra-articular injection, randomized into the following groups: Group 1: AB Serum (ABS); Group 2: Hyaluronic acid (HA); Group 3: Mesenchymal stromal cells (STx.); Group 4: Mesenchymal stromal cells in hyaluronic acid (HA + STx.). After another 4 weeks, the animals were euthanized, followed by histological examination of the removed joints. The histological analysis showed a significant increase in cartilage thickness in the stromal cell treated groups (HA + STx. vs. ABS, p = 0.028; HA + ST.x vs. HA, p = 0.042; STx. vs. ABS, p = 0.036). Scanning electron microscopy detected a similar heterogeneity of mineralization and tissue porosity in the subchondral zone in all groups. The single intra-articular injection of a stem cell containing, GMP-compliant advanced therapy medicinal product for the treatment of iatrogen induced osteoarthritis of the temporomandibular joint shows a chondroregenerative effect.

Retrospective analysis of bacterial colonization of necrotic bone and antibiotic resistance in 98 patients with medication-related osteonecrosis of the jaw (MRONJ).

OBJECTIVES: The aim of our study was to describe microbial flora associated with MRONJ and characterize the susceptibility of pathogens to help guide an effective empiric antibiotic treatment in these patients. MATERIALS AND METHODS: A retrospective, single-center analysis was performed, using 116 bone samples from 98 patients. The bone samples were homogenized and subjected to routine culture methods. Growing bacteria were differentiated to the species level using whole-cell mass spectrometry and subjected to susceptibility testing. RESULTS: A highly diverse microbial flora was detected in necrotic bone, with a simultaneous presence of two or more bacterial species in 79% of all patients. In at least 65% of samples, gram-negative isolates were detected. Therefore, bacterial species resistant against ß-lactamase inhibitors were present in at least 70% of all patients. CONCLUSIONS: The empiric choice of antibiotics in MRONJ patients should consider the high rate of gram-negative bacteria and resistance against ß-lactam antibiotics. CLINICAL RELEVANCE: According to recent guidelines and recommendations, systemic antibiotic treatment is a key component in the treatment of all stage 2 and 3 MRONJ patients. We recommend using fluoroquinolones for empiric treatment and emphasize the use of bacterial cultivation and susceptibility testing to enable an effective antibiotic treatment.

Differential regulation of extracellular matrix proteins in three recurrent liver metastases of a single patient with colorectal cancer.

Colorectal cancer (CRC) patients suffer from the second highest mortality among all cancer entities. In half of all CRC patients, colorectal cancer liver metastases (CRLM) can be observed. Metastatic colorectal cancer is associated with poor overall survival and limited treatment options. Even after successful surgical resection of the primary tumor, metachronous liver metastases occur in one out of eight cases. The only available curative intended treatment is hepatic resection, but metachronous CRLM frequently recur after approximately 1 year. In this study, we performed a proteome analysis of three recurrent liver metastases of a single CRC patient by mass spectrometry. Despite surgical resection of the primary CRC and adjuvant chemotherapy plus cetuximab treatment, the patient developed three metachronous CRLM which occurred consecutively after 9, 21 and 31 months. We identified a set of 1132 proteins expressed in the three metachronous CRLM, of which 481 were differentially regulated, including 81 proteins that were associated with the extracellular matrix (ECM). 56 ECM associated proteins were identified as upregulated in the third metastasis, 26 (46%) of which were previously described as negative prognostic markers in CRC, including tenascin C, nidogen 1, fibulin 1 and vitronectin. These data may reflect an ascending trend of malignancy from the first to the third metachronous colorectal cancer liver metastasis. Additionally, the results indicate different ECM phenotypes for recurrent metachronous metastasis, associated with different grades of malignancy and highlights the importance of individual analysis of molecular features in different, consecutive metastatic events in a single patient.

Ectopic Expression of Hematopoietic SHIP1 in Human Colorectal Cancer.

Colorectal cancer (CRC) is a heterogeneous disease that results from the accumulation of mutations in colonic mucosa cells. A subclass of CRC is characterized by microsatellite instability, which is thought to occur mainly through inactivation of the DNA mismatch repair genes MLH1 and MSH2. The inositol 5-phosphatase SHIP1 is expressed predominantly in hematopoietic cells. In this study, the expression of SHIP1 in carcinomas and its putative correlation with clinicopathologic parameters, expression of DNA repair genes and microsatellite instability was investigated. By analyzing a multi-tumor tissue microarray, expression of SHIP1 was detected in 48 out of 72 cancer entities analyzed. The expression of SHIP1 protein of 145 kDa was confirmed by Western blot analysis in 7 out of 14 carcinoma cell lines. Analysis of a large colorectal cancer tissue microarray with 1009 specimens revealed SHIP1 expression in 62% of the samples analyzed. SHIP1 expression was inversely correlated with lymph node metastasis, vascular invasion and tumor grade, and it was positively associated with left-sided tumor localization. Interestingly, a strong relationship between the expression of SHIP1 and nuclear and membranous beta-catenin and the DNA repair genes MLH1 and MSH2 was observed.

Combined Targeting of AKT and mTOR Inhibits Proliferation of Human NF1-Associated Malignant Peripheral Nerve Sheath Tumour Cells In Vitro but not in a Xenograft Mouse Model In Vivo.

Persistent signalling via the PI3K/AKT/mTOR pathway is a major driver of malignancy in NF1-associated malignant peripheral nerve sheath tumours (MPNST). Nevertheless, single targeting of this pathway is not sufficient to inhibit MPNST growth. In this report, we demonstrate that combined treatment with the allosteric pan-AKT inhibitor MK-2206 and the mTORC1/mTORC2 inhibitor AZD8055 has synergistic effects on the viability of MPNST cell lines in comparison to the treatment with each compound alone. However, when treating animals bearing experimental MPNST with the combined AKT/mTOR regime, no influence on tumour growth was observed. Further analysis of the MPNST xenograft tumours resistant to AKT/mTOR treatment revealed a reactivation of both AKT and mTOR in several tumour samples. Additional targeting of the RAS/RAF/MEK/MAPK pathway with the allosteric MEK1/2 inhibitor AZD6244 showed synergistic effects on the viability of MPNST cell lines in vitro in comparison to the dual AKT/mTOR inhibition. In summary, these data indicate that combined treatment with AKT and mTOR inhibitors is effective on MPNST cells in vitro but tumour resistance can occur rapidly in vivo by restoration of AKT/mTOR signalling. Our data further suggest that a triple treatment with inhibitors against AKT, mTORC1/2 and MEK1/2 may be a promising treatment option that should be further analysed in an experimental MPNST mouse model in vivo.

Evaluation of Periodontal Space Widening in Patients with Antiresorptive Drug-related Osteonecrosis of the Jaws (ARONJ) on Panoramic Radiographs.

BACKGROUND/AIM: The purpose of this study was to evaluate a potential widening of the periodontal space as an initial measurable imaging criterium on panoramic radiographs in patients with the diagnosis of antiresorptive drug related osteonecrosis of the jaw (ARONJ). PATIENTS AND METHODS: A retrospective analysis of panoramic radiographs of 16 patients (12 females and 4 males; mean age is 70.5 years, standard deviation is 14 years) was performed, over a period of 12 months with the diagnosis of ARONJ. Panoramic radiographs of 16 healthy patients (12 females and 4 males; mean age was 70.6 years, standard deviation was 13.8 years) without diagnosis of ARONJ served as controls. All images were taken with the same device and were evaluated by two experienced maxillofacial surgeons and one dentist. RESULTS: Compared to the control group, a mean widening of the periodontal space of 0.06 mm (confidence interval (CI)=0.05-0.17 mm) was found in the study group. However, this difference was not statistically significant. CONCLUSION: Although a very extensive and sophisticated interindividual comparison was performed to evaluate for slight changes of the periodontal space in patients with antiresorptive drug therapy, our results demonstrate that PDS widening is not a predictive parameter for ARONJ. Therefore, our results indicate that panoramic radiographs are not sufficient enough to allow assessment of stages and disease progress in ARONJ patients regarding to periodontal space widening.

Circulating tumor cells as liquid biomarker for high HCC recurrence risk after curative liver resection.

BACKGROUND: Early hepatocellular carcinoma (HCC) has a limited prognosis due to recurrence rates of more than 50% after liver resection. Recurrence within two years is believed to be caused by untraceable micro metastases at the time of resection. The objective of this study was to investigate EpCAM-positive circulating tumor cells (CTC) as liquid biomarker to identify patients with high risk of recurrence after liver resection. METHODS: 61 patients undergoing resection between 2011 and 2015 were consecutively enrolled. Blood specimens were obtained prior to surgery and processed with the CellSearchTM system, detecting EpCAM-positive CTC. The primary endpoint was recurrence-free survival (RFS). RESULTS: 13 women and 44 men (63.6 ± 11.1 years) were finally evaluated. CTC-positive patients had a significantly higher risk of recurrence with a hazard ratio (HR) of 2.3 (p=0.027), and a shorter RFS compared to CTC-negative patients (5.0 ± 1.5 vs. 12.0 ± 2.5 months, p=0.039). As expected, incomplete resection (R1) was also associated with shorter RFS (HR=2.6, p=0.035), but vascular invasion was not. However, the predictive power of CTC status was independent of R1. CONCLUSION: Bloodstream detection of CTC prior to curative-intended liver resection discloses an elevated risk of HCC recurrence and could identify patients, who might benefit from adjuvant treatment.

High expression of micro RNA-135A in hepatocellular carcinoma is associated with recurrence within 12 months after resection.

BACKGROUND: Hepatocellular carcinoma has a dismal prognosis due to recurrence rates of up to 70% after curative resection. Early recurrence is driven by synchronous microscopic intrahepatic metastases. The predictive value of histological parameters is discussed controversially and adjuvant therapy is not established. The aim of this study was to identify patients at high risk for early intrahepatic recurrence by expression profiling of selected micro RNAs. METHODS: In 52 patients undergoing HCC resection between 2011 and 2014, liver and tumor tissue was collected during surgery. Twelve patients with incomplete data regarding HCC recurrence, secondary liver transplantation, or perioperative death were excluded, leaving 40 patients with early recurrence <12 months (R+) or without recurrence for >24 months (R-) to compare grading, T, L, V, and R status. If tissue quality permitted, micro RNAs were measured in HCC and liver tissue. RESULTS: Ten women and 30 men (64.0 ± 10.2 years) were analyzed. R+ occurred in 29 patients 6.2 ± 4.5 months after resection. Surveillance of R- was 26.2 ± 5.2 months. High intratumoral expression of miR-135a was associated with high risk of recurrence (HR = 4.2, p = 0.024, time to recurrence 8.8 ± 2.0 vs. 24.8 ± 4.4 months in patients with low miR-135a expression). As expected, T3 status was correlated with early recurrence, while other histological parameters and expression of miR-21, miR-122, and miR-125a did not. CONCLUSIONS: We show a significant association between high expression of miR-135a and early HCC recurrence. Therefore, high intratumoral miR-135a expression might serve as a novel biomarker to identify patients urgently requiring adjuvant therapy post resection.

Treatment with MAPKAP2 (MK2) inhibitor and DNA methylation inhibitor, 5-aza dC, synergistically triggers apoptosis in hepatocellular carcinoma (HCC) via tristetraprolin (TTP).

Over 100 putative driver genes that are associated with multiple recurrently altered pathways were detected in hepatocellular carcinoma (HCC), suggesting that multiple pathways will need to be inhibited for any therapeutic method to be effective. In this context, functional modification of the RNA regulating protein, tristetraprolin (TTP) that regulates approximately 2500 genes represents a promising strategy in HCC therapy. Since overexpression of TTP induces cell death in all cell types, it would be useful to target the regulator of TTP. In this study, we applied an inhibitor to MAPKAP2 (MK2) that suppresses TTP function. Importantly, cBIOportal for HCC genomics shows that expression level of the MK2 gene correlates with clinical outcome of HCC. We show that upon treatment with MK2 inhibitor, all 5 HCC cell lines, namely HepG2, Huh7, Hep3B, HLE and HLF, reduced cell growth, especially HepG2 and Hep3B cells underwent apoptosis. Simultaneously, TTP target genes such as c-Myc, IER3 or AKT-1 were downregulated. Depletion of the TTP gene rescued cells from apoptosis and restored the TTP-target mRNA expression in the presence of MK2 inhibitor. Furthermore, MK2 was activated in primary HCC that express TTP at high level. The TTP gene was induced upon treatment with DNA methylation inhibitor, 5-aza dC or interferon in three other cell lines, Huh7, HLE or HLF. Upon treatment with MK2 inhibitor and 5-aza dC or interferon these cells underwent apoptosis. The depletion of TTP in these cells partially rescued them from apoptosis, suggesting that the MK2/TTP pathway plays a role in proliferation and maintenance of HCCs. Notably, under the same conditions human hepatocyte cells (THLE-2) did not undergo apoptosis. These data also suggest that MK2 inhibitor with 5-aza dC or interferon may be a useful tool for therapy against HCC.

Associating liver partition and portal vein ligation for staged hepatectomy: From technical evolution to oncological benefit.

Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a novel approach in liver surgery that allows for extensive resection of liver parenchyma by inducing a rapid hypertrophy of the future remnant liver. However, recent reports indicate that not all patients eligible for ALPPS will benefit from this procedure. Therefore, careful patient selection will be necessary to fully exploit possible benefits of ALPPS. Here, we provide a comprehensive overview of the technical evolution of ALPPS with a special emphasis on safety and oncologic efficacy. Furthermore, we review the contemporary literature regarding indication and benefits, but also limitations of ALPPS.

Extracellular-signal regulated kinase (Erk1/2), mitogen-activated protein kinase-activated protein kinase 2 (MK2) and tristetraprolin (TTP) comprehensively regulate injury-induced immediate early gene (IEG) response in in vitro liver organ culture.

Differentiated hepatocytes are long-lived and normally do not undergo cell division, however they have the unique capacity to autonomously decide their replication fate after liver injury. In this context, the key players of liver regeneration immediately after injury have not been adequately studied. Using an in vitro liver culture system, we show that after liver injury, p38 mitogen-activated protein kinase (p38MAPK), mitogen-activated protein kinase-activated protein kinase 2 (MK2) and extracellular-signal regulated kinase (Erk)1/2 were activated within 15 min and continued to be phosphorylated for more than 2h. Both p38MAPK and Erk1/2 were activated at the edge of the cut as well as on the liver surface where the mesothelial cell sheet expresses several cytokines. Notably, in human liver Erk1/2 was also activated under the mesothelial cell sheet shortly after liver resections. Furthermore, in in vitro liver slice culture immediate early genes (IEGs) were upregulated within 1-2 h and the S phase marker proliferation-cell-nuclear-antigen (PCNA) appeared 24 h after injury. Although Erk1/2 was activated after injury, in MK2 depleted liver a set of IEGs, such as Dusp1, Cox2, or c-Myc and proliferation marker gene Ki67 were not induced. In addition, in immortalized hepatocyte cells, THLE-2, the same subset of genes was upregulated upon stimulation with lipopolysaccharide (LPS), but not in the presence of MK2 inhibitor. The protein level of tristetraprolin (TTP), a substrate for MK2 that plays a role in mRNA degradation, was increased in the presence of MK2 inhibitor. In this context, the depletion of TTP gene rescued Dusp1, Cox2, or c-Myc upregulation in the presence of MK2 inhibitor. These data imply that MK2 pathway is positively involved in Erk1/2 induced IEG response after liver injury. These data also suggest that in vitro liver culture may be a useful tool for measuring the proliferation potential of hepatocytes in individual liver.

Downregulation of AKT3 Increases Migration and Metastasis in Triple Negative Breast Cancer Cells by Upregulating S100A4.

BACKGROUND: Treatment of breast cancer patients with distant metastases represents one of the biggest challenges in today's gynecological oncology. Therefore, a better understanding of mechanisms promoting the development of metastases is of paramount importance. The serine/threonine kinase AKT was shown to drive cancer progression and metastasis. However, there is emerging data that single AKT isoforms (i.e. AKT1, AKT2 and AKT3) have different or even opposing functions in the regulation of cancer cell migration in vitro, giving rise to the hypothesis that inhibition of distinct AKT isoforms might have undesirable effects on cancer dissemination in vivo. METHODS: The triple negative breast cancer cell line MDA-MB-231 was used to investigate the functional roles of AKT in migration and metastasis. AKT single and double knockdown cells were generated using isoform specific shRNAs. Migration was analyzed using live cell imaging, chemotaxis and transwell assays. The metastatic potential of AKT isoform knockdown cells was evaluated in a subcutaneous xenograft mouse model in vivo. RESULTS: Depletion of AKT3, but not AKT1 or AKT2, resulted in increased migration in vitro. This effect was even more prominent in AKT2,3 double knockdown cells. Furthermore, combined downregulation of AKT2 and AKT3, as well as AKT1 and AKT3 significantly increased metastasis formation in vivo. Screening for promigratory proteins revealed that downregulation of AKT3 increases the expression of S100A4 protein. In accordance, depletion of S100A4 by siRNA approach reverses the increased migration induced by knockdown of AKT3. CONCLUSIONS: We demonstrated that knockdown of AKT3 can increase the metastatic potential of triple negative breast cancer cells. Therefore, our results provide a rationale for the development of AKT isoform specific inhibitors.

Vertical Targeting of AKT and mTOR as Well as Dual Targeting of AKT and MEK Signaling Is Synergistic in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the sixth most common cancer, and the third most common cause of cancer related death worldwide. The multi-kinase inhibitor Sorafenib represents the only systemic treatment option until today, and results from clinical trials with allosteric mTOR inhibitors were sobering. Since the PI3K/AKT/mTOR and RAF/MEK/ERK signaling pathways are frequently upregulated in HCC, we have analyzed the effects of AKT inhibitor MK-2206, MEK inhibitor AZD6244 (ARRY 142886) and mTOR kinase inhibitor AZD8055, given as single drugs or in combination, on proliferation and apoptosis of three HCC cell lines in vitro. We show that all three inhibitor combinations synergistically inhibit proliferation of the three HCC cell lines, with the strongest synergistic effect observed after vertical inhibition of AKT and mTORC1/2. We demonstrate that AKT kinase activity is restored 24h after blockade of mTORC1/2 by increased phosphorylation of T308, providing a rationale for combined targeting of AKT and mTOR inhibition in HCC. Our data suggest that a combination of inhibitors targeting those respective pathways may be a viable approach for future application in patients with hepatocellular carcinoma.

Discontinuing MEK inhibitors in tumor cells with an acquired resistance increases migration and invasion.

BACKGROUND: Development of small molecular inhibitors against BRAF and MEK has been a breakthrough in the treatment of malignant melanoma. However, the long-term effect is foiled in virtually all patients by the emergence of resistant tumor cell populations. Therefore, mechanisms resulting in the acquired resistance against BRAF and MEK inhibitors have gained much attention and several strategies have been proposed to overcome tumor resistance, including interval treatment or withdrawal of these compounds after disease progression. METHODS: Using a panel of cell lines with an acquired resistance against MEK inhibitors, we have evaluated the sensitivity of these cells against compounds targeting AKT/mTOR signaling, as well as novel ERK1/2 inhibitors. Furthermore, the effects of withdrawal of MEK inhibitor on migration in resistant cell lines were analyzed. RESULTS: We demonstrate that withdrawal of BRAF or MEK inhibitors in tumor cells with an acquired resistance results in reactivation of ERK1/2 signaling and upregulation of EMT-inducing transcription factors, leading to a highly migratory and invasive phenotype of cancer cells. Furthermore, we show that migration in these cells is independent from AKT/mTOR signaling. However, combined targeting of AKT/mTOR using MK-2206 and AZD8055 efficiently inhibits proliferation in all resistant tumor cell lines analyzed. CONCLUSIONS: We propose that combined targeting of MEK/AKT/mTOR or treatment with a novel ERK1/2 inhibitor downstream of BRAF/MEK suppresses proliferation as well as migration and invasion in resistant tumor cells. We provide a rationale against the discontinuation of BRAF or MEK inhibitors in patients with an acquired resistance, and provide a rationale for combined targeting of AKT/mTOR and MEK/ERK1/2, or direct targeting of ERK1/2 as an effective treatment strategy.

COSMC knockdown mediated aberrant O-glycosylation promotes oncogenic properties in pancreatic cancer.

BACKGROUND: Human pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal malignancies in the world and despite great efforts in research types of treatment remain limited. A frequently detected alteration in PDACs is a truncated O-linked N-acetylgalactosamine (GalNAc) glycosylation with expression of the Tn antigen. Changes in O-glycosylation affect posttranslationally modified O-GalNAc proteins resulting in profound cellular alterations. Tn antigen is a tumor associated glycan detected in 75-90 % of PDACs and up to 67 % in its precursor lesions. Since the role of Tn antigen expression in PDAC is insufficiently understood we analyzed the impact of COSMC mediated Tn antigen expression in two human PDAC cell lines on cellular oncogenic properties. METHODS: Forced expression of Tn antigen on O-glycosylated proteins in pancreatic cancer cells was induced by lentiviral-mediated knockdown of the COSMC chaperone, which prevented O-glycan elongation beyond the initial GalNAcα1- residue on O-linked glycoproteins. Altered O-GalNAc glycosylation was analyzed in human pancreatic cancer cell lines Panc-1 and L3.6pl using Western and Far-Western blot as well as immunocytochemical techniques. To assess the biological implications of COSMC function on oncogenic properties, cell viability assays, scratch assays combined with live cell imaging, migration and apoptosis assays were performed. Lectin based glycoprotein enrichment with subsequent mass spectrometric analysis identified new cancer O-GalNAc modified proteins. Expression of Tn antigen bearing Nucleolin in patient derived PDAC tumor specimens was evaluated and correlated with clinicopathological data. RESULTS: Tn antigen expression was induced on various O-GalNAc glycoproteins in COSMC deficient cell lines compared to the control. Proliferation was reduced (p < 0.001) in COSMC knockdown cells, whereas migration was increased (p < 0.001) and apoptosis was decreased (p = 0.03), highlighting the importance of Tn antigen expression on metastatic and anti-apoptotic behavior of PDAC derived cells. Nucleolin was identified as O-GalNAc modified protein in COSMC deficient PDAC cell lines. Interestingly, immunohistochemical staining and co-localization studies of patient derived PDACs revealed poor survival for patients with strong co-localization of Tn antigen and Nucleolin (p = 0.037). CONCLUSION: This study substantiates the influence of altered O-glycan (Tn/STn) expression on oncogenic properties in pancreatic cancer and identifies O-GalNAc modified Nucleolin as novel prognostic marker.

ErbB2 signaling activates the Hedgehog pathway via PI3K-Akt in human esophageal adenocarcinoma: identification of novel targets for concerted therapy concepts.

The Hedgehog pathway plays an important role in the pathogenesis of several tumor types, including esophageal cancer. In our study, we show an expression of the ligand Indian hedgehog (Ihh) and its downstream mediator Gli-1 in primary resected adenocarcinoma tissue by immunohistochemistry and quantitative PCR in fifty percent of the cases, while matching healthy esophagus mucosa was negative for both proteins. Moreover, a functionally important regulation of Gli-1 by ErbB2-PI3K-mTORC signaling as well as a Gli-1-dependent regulation of Ihh in the ErbB2 amplified esophageal adenocarcinoma cell line OE19 was observed. Treatment of OE19 cells with the Her2 antibody trastuzumab, the PI3K-mTORC1 inhibitor NVP BEZ235 (BEZ235) or the knockdown of Akt1 resulted in a downregulation of Gli-1 and Ihh as well as in a reduction of viable OE19 cells in vitro. Interestingly, the Hedgehog receptor Smo, which acts upstream of Gli-1, was not expressed in OE19 cells and in the majority of primary human esophageal adenocarcinoma, suggesting a non-canonical upregulation of Gli-1 expression by the ErbB2-PI3K axis. To translate our findings into a therapeutic concept, we targeted ErbB2-PI3K-mTORC1 by trastuzumab and BEZ235, combining both compounds with the Gli-1/2 inhibitor GANT61. The triple combination led to significantly stronger reduction of tumor cell viability than cisplatinum or each biological alone. Therefore, concomitant blockage of the ErbB2-PI3K pathway and the Hedgehog downstream mediator Gli-1 may provide a new therapeutic strategy for esophageal cancer.

ABO blood group IgM isoagglutinins interact with tumor-associated O-glycan structures in pancreatic cancer.

PURPOSE: The ABO gene locus is associated with the risk of developing pancreatic ductal adenocarcinoma (PDAC) resulting in an increased incidence in individuals with non-O blood groups. Up to 90% of PDAC specimens display alterations in mucin type O-GalNAc glycosylation. Because aberrant O-GalNAc glycans (Tn and T antigen) are structurally related to blood group A and B glycans, we investigated the role of IgM isoagglutinins in PDAC. EXPERIMENTAL DESIGN: Binding studies of IgM isoagglutinins toward blood group A, B, Tn antigen, and T antigen glycoconjugates from patients with PDAC and healthy individuals were conducted. Isoagglutinin titers and total IgM were compared between patients with PDAC and control group. An anti-A antibody was used for immunoprecipitation of aberrant O-glycosylated tumor proteins and subsequent mass spectromic analysis. RESULTS: We found that IgM isoagglutinins bind blood group antigens, Tn and T glycoconjugates as well as tumor-derived glycoproteins. Blood group A isoagglutinins exhibited a strong binding toward blood group B antigen and T antigen, whereas blood group B showed binding to blood group A antigen and Tn antigen. Furthermore, we confirmed a decreased frequency in individuals with blood group O and observed a significant decrease of IgM isoagglutinin titers in PDAC sera compared with control sera, whereas total IgM levels were unaltered. We identified new PDAC-derived O-GalNAc glycoproteins by mass spectrometry using a blood group A-specific antibody. CONCLUSION: Our data elucidated a novel interaction of blood group IgM isoagglutinins and PDAC O-GalNAc glycoproteins that may contribute to the pathogenesis and progression of pancreatic cancer.