Direct Pharmacological Targeting of a Mitochondrial Ion Channel Selectively Kills Tumor Cells In Vivo

The potassium channel Kv1.3 is highly expressed in the mitochondria of various cancerous cells. Here we show that direct inhibition of Kv1.3 using two mitochondria-targeted inhibitors alters mitochondrial function and leads to reactive oxygen species (ROS)-mediated death of even chemoresistant cells independently of p53 status. These inhibitors killed 98% of ex vivo primary chronic B-lymphocytic leukemia tumor cells while sparing healthy B cells. In orthotopic mouse models of melanoma and pancreatic ductal adenocarcinoma, the compounds reduced tumor size by more than 90% and 60%, respectively, while sparing immune and cardiac functions. Our work provides direct evidence that specific pharmacological targeting of a mitochondrial potassium channel can lead to ROS-mediated selective apoptosis of cancer cells in vivo, without causing significant side effects.

E2F1 Signalling is Predictive of Chemoresistance and Lymphogenic Metastasis in Penile Cancer: A Pilot Functional Study Reveals New Prognostic Biomarkers

BACKGROUND

For penile cancer (PC) there are no known molecular predictors of lymphatic spread and/or chemoresistance.

OBJECTIVE

To identify functional biomarkers that can predict malignant progression and treatment responsiveness.

DESIGN, SETTING, AND PARTICIPANTS

We used four patient-derived PC cell lines and measured invasion and capillary tube formation, chemoresponsiveness, and mRNA and protein expression. Data were further validated in E2F1 transcription factor knockdown and overexpression experiments. We quantified E2F1 transcript levels in a set of nonmetastatic tumours (NM), metastasised primary tumours (PT), and lymph node metastases (M) from 24 patients. E2F1 immunohistochemistry was performed in another set of 13 PC biopsies.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Relationships between different parameters were analysed using Student t tests. Transcript levels in patient samples were compared using Mann-Whitney U tests. Significance was set at p<0.05.

RESULTS AND LIMITATIONS

In cell lines established from lymph node metastases, E2F1 was more abundantly expressed, pRB was inactivated, and CDK2, CDK4, and cyclins D and E were elevated in comparison to cells from primary PC. Overexpression of E2F1 enhanced migratory capacity and lymphatic endothelial tubule formation, while depletion reduced invasiveness and increased chemosensitivity. VEGFR-3 and VEGF-C and mesenchymal markers were upregulated by high E2F1. E2F1 was clearly upregulated in infiltrative and metastatic primary tumours and metastases (NM vs PT, p<0.05; NM vs M, p<0.0005). E2F1 Quick scores increased from grade I to grade III tumours. A limitation of the study is the small number of patients.

CONCLUSIONS

E2F1 is a driver of invasion and lymphatic dissemination and promotes chemoresistance. E2F1-related biomarkers might assist in stratifying PC patients for different treatment regimens.

PATIENT SUMMARY

The availability of penile cancer cell lines allows molecular research on the mechanisms underlying metastasis and chemotherapy. A critical pathway involved in both features has been identified and may lead to better patient stratification for treatment selection.

Detection of circulating tumor cells with CK20 RT-PCR is an independent negative prognostic marker in colon cancer patients - a prospective study

Background

Detection of circulating (CTC) or disseminated tumor cells (DTC) has been associated with negative prognosis and outcome in patients with colorectal cancer, though testing for these cells is not yet part of clinical routine. There are several different methodological approaches to detect tumor cells but standardized detection assays are not implemented so far.

Methods

In this prospective monocentric study 299 patients with colon cancer were included. CTC and DTC were detected using CK20 RT-PCR as well as immunocytochemistry staining with anti-pan-keratin and anti-EpCAM antibodies. The primary endpoints were: Evaluation of CTC and DTC at the time of surgery and correlation with main tumor characteristics and overall (OS) and disease free survival (DFS).

Results

Patients with detectable CTC had a 5-year OS rate of 68% compared to a 5-year OS rate of 85% in patients without detectable CTC in the blood (p = 0.002). Detection of DTC in the bone marrow with CK20 RT-PCR was not associated with a worse OS or DFS. Detection of pan-cytokeratin positive DTC in the bone marrow correlated with a significantly reduced 5-year OS rate (p = 0.048), but detection of DTC in the bone marrow with the anti-EpCAM antibody did not significantly influence the 5-year OS rate (p = 0.958). By multivariate analyses only detection of CTC with CK20 RT-PCR in the blood was revealed to be an independent predictor of worse OS (HR1.94; 95% CI 1.0–3.7; p = 0.04) and DFS (HR 1.94; 95% CI 1.1–3.7; p = 0.044).

Conclusions

Detection of CTC with CK20 RT-PCR is a highly specific and independent prognostic marker in colon cancer patients. Detection of DTC in the bone marrow with CK20 RT-PCR or immunohistochemistry with anti-EpCAM antibody is not associated with a negative prognostic influence.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-3035-1) contains supplementary material, which is available to authorized users.

Ion channels in control of pancreatic stellate cell migration

Pancreatic stellate cells (PSCs) play a critical role in the progression of pancreatic ductal adenocarcinoma (PDAC). Once activated, PSCs support proliferation and metastasis of carcinoma cells. PSCs even co-metastasise with carcinoma cells. This requires the ability of PSCs to migrate. In recent years, it has been established that almost all "hallmarks of cancer" such as proliferation or migration/invasion also rely on the expression and function of ion channels. So far, there is only very limited information about the function of ion channels in PSCs. Yet, there is growing evidence that ion channels in stromal cells also contribute to tumor progression. Here we investigated the function of KCa3.1 channels in PSCs. KCa3.1 channels are also found in many tumor cells of different origin. We revealed the functional expression of KCa3.1 channels by means of Western blot, immunofluorescence and patch clamp analysis. The impact of KCa3.1 channel activity on PSC function was determined with live-cell imaging and by measuring the intracellular Ca2+ concentration ([Ca2+]i). KCa3.1 channel blockade or knockout prevents the stimulation of PSC migration and chemotaxis by reducing the [Ca2+]i and calpain activity. KCa3.1 channels functionally cooperate with TRPC3 channels that are upregulated in PDAC stroma. Knockdown of TRPC3 channels largely abolishes the impact of KCa3.1 channels on PSC migration. In summary, our results clearly show that ion channels are crucial players in PSC physiology and pathophysiology.

Negative control of TRAIL-R1 signaling by transforming growth factor β1 in pancreatic tumor cells involves Smad-dependent down regulation of TRAIL-R1

Pancreatic ductal adenocarcinoma (PDAC) is characterized by both, overexpression of transforming growth factor (TGF)β and resistance of the tumor cells to many apoptosis-inducing stimuli. The latter negatively impacts the outcome of therapeutic efforts and represents one important mechanism which tumor cells utilize to escape the immune surveillance. Since TGFβ acts as a tumor promoter in advanced tumor stages and suppression of apoptosis is a known driver of tumor progression, it is possible that TGFβ functions as a crucial determinant of tumor cell sensitivity to apoptosis in PDAC. Here, we have studied the impact of TGFβ on TNF-related apoptosis inducing ligand (TRAIL)-induced signaling in PDAC cells. In TGFβ-responsive Panc1 and Colo357 cells, TGFβ1 reduced total and plasma membrane-associated levels of TRAIL-R1 but not those of TRAIL-R2. Consistent with the known predominant role of TRAIL-R1 in TRAIL-mediated signaling in PDAC, TGFβ1 inhibited TRAIL-induced DISC formation and apoptosis as well as phosphorylation of MAPKs and IκBα. Similarly, it also reduced signaling of TRAIL-R1 following its specific activation with an agonistic antibody. In contrast, specific TRAIL-R2 signaling remained unchanged. The TGFβ1 effect on TRAIL-R1 expression was mimicked by ectopic expression of a kinase-active version of the TGFβ type I receptor ALK5 (ALK5-T204D) but not by ALK5 double mutant lacking the ability to phosphorylate Smad proteins (RImL45-T204D). Moreover, TGFβ regulation of TRAIL-R1 was absent in two PDAC cell lines lacking the Smad4 gene DPC4 and siRNA-mediated silencing of Smad4 in Smad4-positive Panc1 cells abolished the TGFβ-mediated decrease in TRAIL-R1 expression, together showing that ALK5/Smad4 signaling is crucial for TGFβ regulation of TRAIL-R1 expression. Our results suggest a novel tumor-promoting function of TGFβ1. By downregulating TRAIL-R1, TGFβ1 may not only promote tumor escape from immune surveillance but also negatively impact on TRAIL- or TRAIL-R1-based therapy regimens for treatment of PDAC.

Increased survival rate by local release of diclofenac in a murine model of recurrent oral carcinoma

Despite aggressive treatment with radiation and combination chemotherapy following tumor resection, the 5-year survival rate for patients with head and neck cancer is at best only 50%. In this study, we examined the therapeutic potential of localized release of diclofenac from electrospun nanofibers generated from poly(D,L-lactide-co-glycolide) polymer. Diclofenac was chosen since anti-inflammatory agents that inhibit cyclooxygenase have shown great potential in their ability to directly inhibit tumor growth as well as suppress inflammation-mediated tumor growth. A mouse resection model of oral carcinoma was developed by establishing tumor growth in the oral cavity by ultrasound-guided injection of 1 million SCC-9 cells in the floor of the mouth. Following resection, mice were allocated into four groups with the following treatment: 1) no treatment, 2) implanted scaffolds without diclofenac, 3) implanted scaffolds loaded with diclofenac, and 4) diclofenac given orally. Small animal ultrasound and magnetic resonance imaging were utilized for longitudinal determination of tumor recurrence. At the end of 7 weeks following tumor resection, 33% of mice with diclofenac-loaded scaffolds had a recurrent tumor, in comparison to 90%–100% of the mice in the other three groups. At this time point, mice with diclofenac-releasing scaffolds showed 89% survival rate, while the other groups showed survival rates of 10%–25%. Immunohistochemical staining of recurrent tumors revealed a near 10-fold decrease in the proliferation marker Ki-67 in the tumors derived from mice with diclofenac-releasing scaffolds. In summary, the local application of diclofenac in an orthotopic mouse tumor resection model of oral cancer reduced tumor recurrence with significant improvement in survival over a 7-week study period following tumor resection. Local drug release of anti-inflammatory agents should be investigated as a therapeutic option in the prevention of tumor recurrence in oral squamous carcinoma.

In silico analysis of the transportome in human pancreatic ductal adenocarcinoma

The altered expression and/or activity of ion channels and transporters (transportome) have been associated with malignant behavior of cancer cells and were proposed to be a hallmark of cancer. However, the impact of altered transportome in epithelial cancers, such as pancreatic ductal adenocarcinoma (PDAC), as well as its pathophysiological consequences, still remains unclear. Here, we report the in silico analysis of 840 transportome genes in PDAC patients' tissues. Our study was focused on the transportome changes and their correlation with functional and behavioral responses in PDAC tumor and stromal compartments. The dysregulated gene expression datasets were filtered using a cut-off of fold-change values ≤-2 or ≥2 (adjusted p value ≤0.05). The dysregulated transportome genes were clearly associated with impaired physiological secretory mechanisms and/or pH regulation, control of cell volume, and cell polarity. Additionally, some down-regulated transportome genes were found to be closely linked to epithelial cell differentiation. Furthermore, the observed decrease in genes coding for calcium and chloride transport might be a mechanism for evasion of apoptosis. In conclusion, the current work provides a comprehensive overview of the altered transportome expression and its association with predicted PDAC malignancy with special focus on the epithelial compartment.

Influence of mTOR-inhibitors and mycophenolic acid on human cholangiocellular carcinoma and cancer associated fibroblasts

Background

The incidence of Cholangiocellular Carcinoma (CCA) is increasing in the western world. The tumour has a high proportion of desmoplastic stroma and is correlated with a worse prognosis when cancer associated myofibroblasts (CAFs) are present. Recent studies showed promising results after liver transplantation (LTx) in non-resectable early stage CCA. Mycophenolic acid (MPA) and the mTor inhibitor Everolimus are used to prevent organ rejection but recently were shown to exhibit an antiproliferative effect on CCA-cells. Little is known about the influence of immunosuppressive drugs on tumour cell proliferation and migration after paracrine stimulation by CAFs. Moreover, it is still unknown, which signaling pathways are activated following these specific cell-cell interactions.

Methods

CCA cell lines HuCCT1 and TFK1 were utilized for the study. CAFs were derived from resected CCA cancer tissue. Cell viability was measured by the crystal violet assay and tumour cell invasion was quantified using a modified co-culture transmigration assay. Semiquantitative cytokine-expression was measured using a cytokine-array. Protein expression and phosphorylation of ERK, STAT3 and AKT was determined by Western-blot analysis.

Results

CCA cells treated with MPA exhibited a dose related decrease in cell viability in contrast to Cyclosporine A (CSA) treatment which had no effect on cell viability. Everolimus significantly inhibited proliferation at very low concentrations. The pro-invasive effect of CAFs in co-culture transmigration assay was significantly reduced by Everolimus at a concentration of 1nM (p = 0.047). In contrast, MPA and CSA showed no effect on tumour cell invasion. Treatment of CAFs with 1nM Everolimus showed a significant reduction in the expression of IL 8, IL 13, MCP1, MIF and Serpin E1. CCA-cells showed significant increases in phosphorylation of ERK, STAT3 and AKT under the influence of conditioned CAF-media. This effect was suppressed by Everolimus.

Conclusions

The secretion of proinflammatory cytokines by CAFs may lead to increased activation of JAK/STAT3-, ERK- and AKT-signaling and increased migration of CCA-cells. Everolimus abrogates this effect and inhibits proliferation of CCA-cells even at low concentrations.

LTx for non-resectable early stage CCA is currently performed in several clinical studies. Consistent with a role for common immunosuppressants in inhibiting tumour cell-proliferation and -invasion, our study indicates that a combination of standard therapies with Everolimus and MPA is a promising therapy option to treat CCA following LTx.

TRAIL-R2 promotes skeletal metastasis in a breast cancer xenograft mouse model

Despite improvements in detection, surgical approaches and systemic therapies, breast cancer remains typically incurable once distant metastases occur. High expression of TRAIL-R2 was found to be associated with poor prognostic parameters in breast cancer patients, suggesting an oncogenic function of this receptor. In the present study, we aimed to determine the impact of TRAIL-R2 on breast cancer metastasis. Using an osteotropic variant of MDA-MB-231 breast cancer cells, we examine the effects of TRAIL-R2 knockdown in vitro and in vivo. Strikingly, in addition to the reduced levels of the proliferation-promoting factor HMGA2 and corresponding inhibition of cell proliferation, knockdown of TRAIL-R2 increased the levels of E-Cadherin and decreased migration. In vivo, these cells were strongly impaired in their ability to form bone metastases after intracardiac injection. Evaluating possible underlying mechanisms revealed a strong downregulation of CXCR4, the receptor for the chemokine SDF-1 important for homing of cancers cells to the bone. In accordance, cell migration towards SDF-1 was significantly impaired by TRAIL-R2 knockdown. Conversely, overexpression of TRAIL-R2 upregulated CXCR4 levels and enhanced SDF-1-directed migration. We therefore postulate that inhibition of TRAIL-R2 expression could represent a promising therapeutic strategy leading to an effective impairment of breast cancer cell capability to form skeletal metastases.

Interleukin-6 trans-signaling increases the expression of carcinoembryonic antigen-related cell adhesion molecules 5 and 6 in colorectal cancer cells

Background

Colorectal cancer (CRC) is among the five most frequent causes for cancer-related deaths in Europe. One of the most important tumor-associated antigens for CRC is carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), which is involved in cell adhesion, migration, anoikis, tumor invasion and metastasis. Its family member CEACAM6 is also upregulated in adenomas and carcinomas of the colon and an independent predictor of poor survival. Previous studies have reported a link between upregulation of CEACAM5 and interleukin-6 (IL-6). IL-6 plays an important role in CRC progression, and signaling is mediated via two pathways (classic and trans-signaling). However, this link could not be confirmed by other studies, and the role of IL-6 trans-signaling in the CEACAM5 upregulation has not been elucidated. Moreover, the impact of IL-6 on the expression of CEACAM6 has not yet been examined.

Methods

The expression of IL-6, IL-6 receptor (IL-6R), glycoprotein (gp) 130, CEACAM5 and CEACAM6 was analyzed by RT-PCR, Western blot, flow cytometry or qPCR. Colon cell lines were incubated with IL-6 or Hyper-IL-6 (mediating IL-6 trans-signaling), and subsequently, the expression of CEACAMs was determined by qPCR or Western blot. FLLL31, an inhibitor of the phosphorylation of signal transducer and activator of transcription-3 (STAT3), was used to determine the role of STAT3 phosphorylation.

Results

We confirmed that colon carcinoma cell lines express IL-6 and IL-6R. We observed only a weak upregulation of CEACAM5 and CEACAM6 by classic IL-6 signaling, but a strong increase by IL-6 trans-signaling. This upregulation depended on the phosphorylation of STAT3.

Conclusions

Our data show the upregulation of the tumor-associated antigens CEACAM5/6 by trans-signaling of the pro-inflammatory cytokine IL-6. This mechanism may contribute to the tumor-promoting role of IL-6 and could therefore be a target for therapeutic intervention in particular by specific inhibitors such as sgp130Fc.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1950-1) contains supplementary material, which is available to authorized users.

Cytokeratin 20 positive circulating tumor cells are a marker for response after neoadjuvant chemoradiation but not for prognosis in patients with rectal cancer

Background

Several studies have shown, that circulating tumor cells (CTC) have a negative prognostic value in colorectal cancer patients. Aim of this study was to evaluate the role of CTC in specifically rectal cancer patients regarding the influence on overall survival and to elucidate the impact of CTC in predicting response after chemoradiation (RCTX).

Methods

In this prospective monocentric study 267 patients with rectal cancer were included. Patients with locally advanced tumors were treated with RCTX followed by surgery. The primary endpoints were: Evaluation of CTC at the time of surgery and correlation with main tumor characteristics, response to neoadjuvant RCTX and overall survival (OS). CTC were detected in the blood using CK20 RT-PCR.

Results

Sixty-three patients were treated with neoadjuvant RCTX. In 46.8 % of the patients receiving neoadjuvant RCTX CTC were detected, which was significantly higher than in the group without RCTX (p = 0.002). Histopathologic regression after RCTX was evident in 27.8 % of the patients. In the subgroup of responders after RCTX we found CTC at a significantly lower rate than in non-responders (p = 0.03). No significant association was found between CTC detection and tumor characteristics and OS. The OS was significantly improved for responders compared to non-responders (p = 0.007).

Conclusions

Responders after neoadjuvant RCTX had a lower incidence of CTC compared to non-responders, which might be a result of effective systemic and local treatment prior to surgery. Interestingly, detection of CTC did not correlate with tumor stage and OS, which is in contrast to previous reports of patients with colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1989-z) contains supplementary material, which is available to authorized users.

A novel NHE1-centered signaling cassette drives epidermal growth factor receptor-dependent pancreatic tumor metastasis and is a target for combination therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers principally because of early invasion and metastasis. The epidermal growth factor receptor (EGFR) is essential for PDAC development even in the presence of Kras, but its inhibition with erlotinib gives only a modest clinical response, making the discovery of novel EGFR targets of critical interest. Here, we revealed by mining a human pancreatic gene expression database that the metastasis promoter Na⁺/H⁺ exchanger (NHE1) associates with the EGFR in PDAC. In human PDAC cell lines, we confirmed that NHE1 drives both basal and EGF-stimulated three-dimensional growth and early invasion via invadopodial extracellular matrix digestion. EGF promoted the complexing of EGFR with NHE1 via the scaffolding protein Na +/H + exchanger regulatory factor 1, engaging EGFR in a negative transregulatory loop that controls the extent and duration of EGFR oncogenic signaling and stimulates NHE1. The specificity of NHE1 for growth or invasion depends on the segregation of the transient EGFR/Na +/H + exchanger regulatory factor 1/NHE1 signaling complex into dimeric subcomplexes in different lipid raftlike membrane domains. This signaling complex was also found in tumors developed in orthotopic mice. Importantly, the specific NHE1 inhibitor cariporide reduced both three-dimensional growth and invasion independently of PDAC subtype and synergistically sensitized these behaviors to low doses of erlotinib.

Integrins αvβ3 and αvβ5 as prognostic, diagnostic, and therapeutic targets in gastric cancer

BACKGROUND

We investigated the expression of two αv integrins, αvβ3 and αvβ5, in gastric cancer (GC) by testing the following hypotheses: that these molecules are expressed in GC; that they are implicated in GC biology; that they help to distinguish between the two major histological subtypes of GC, according to Laurén; and that they are prognostically relevant.

METHODS

Formalin-fixed and paraffin-embedded tissue samples from 482 GC samples were stained immunohistochemically using rabbit monoclonal antibodies directed against αvβ3 (EM22703) and αvβ5 (EM09902). Immunostaining of tumor, stroma, and endothelial cells was evaluated separately by the quantity and intensity, generating an immunoreactivity score. The immunoreactivity score of both antibodies was correlated with clinicopathology data and patient survival.

RESULTS

Each integrin was expressed in at least one tumor component in all GCs. Both were expressed significantly more often in the intestinal phenotype according to Laurén. Moreover, patients who grouped as "positive" for expression of αvβ3 on endothelial cells, and patients with an intestinal type GC, grouped as "negative" for expression of αvβ5 on stroma cells, had significantly longer survival. The expression of αvβ5 on stroma cells was confirmed to be an independent prognostic factor of intestinal-type GC.

CONCLUSION

The expression of αvβ3 and αvβ5 in at least one tumor component in all GC samples is an interesting new result that should form a basis for further investigations; for example, regarding selective integrin antagonists and the value of αvβ3 and αvβ5 as putative prognostic biomarkers. Moreover, both markers might be helpful in the routine classification of GC subtypes.

Molecular Mechanisms by Which a Fucus vesiculosus Extract Mediates Cell Cycle Inhibition and Cell Death in Pancreatic Cancer Cells

Pancreatic cancer is one of the most aggressive cancer entities, with an extremely poor 5-year survival rate. Therefore, novel therapeutic agents with specific modes of action are urgently needed. Marine organisms represent a promising source to identify new pharmacologically active substances. Secondary metabolites derived from marine algae are of particular interest. The present work describes cellular and molecular mechanisms induced by an HPLC-fractionated, hydrophilic extract derived from the Baltic brown seaweed Fucus vesiculosus (Fv1). Treatment with Fv1 resulted in a strong inhibition of viability in various pancreatic cancer cell lines. This extract inhibited the cell cycle of proliferating cells due to the up-regulation of cell cycle inhibitors, shown on the mRNA (microarray data) and protein level. As a result, cells were dying in a caspase-independent manner. Experiments with non-dividing cells showed that proliferation is a prerequisite for the effectiveness of Fv1. Importantly, Fv1 showed low cytotoxic activity against non-malignant resting T cells and terminally differentiated cells like erythrocytes. Interestingly, accelerated killing effects were observed in combination with inhibitors of autophagy. Our in vitro data suggest that Fv1 may represent a promising new agent that deserves further development towards clinical application.

Profile of serum factors and disseminated tumor cells before and after radiofrequency ablation compared to resection of colorectal liver metastases - a pilot study

BACKGROUND/AIM

The degree of systemic response after hepatic radiofrequency ablation (RFA) has not been well-compared to liver resection so far. This pilot study was designed to examine whether RFA, compared to liver resection, significantly varies concerning dissemination of circulating tumor cells and induction of different pro-inflammatory markers and liver-specific growth factors.

PATIENTS AND METHODS

Patients with colorectal liver metastases were treated with RFA, a combination of RFA and resection or liver resection only. Blood samples of 18 patients were obtained at different time points and interleukin (IL)-6, hepatocyte growth factor (HGF) and 70-kD heat shock protein (HSP70) serum levels were determined by ELISA. Circulating tumor cells were detected with reverse transcription-polymerase chain reaction (RT-PCR) amplification of cytokeratin 20 (CK20) mRNA (CK20 RT-PCR).

RESULTS

The detection of circulating tumor cells was not significantly different, but in two patients RFA induced tumor cell dissemination. Serum levels of IL-6 were strongly elevated after the operation without any significant differences between the treatment groups. The HGF ratio was significantly higher after RFA+resection compared to resection-alone and the HSP70 ratio also showed significantly higher values after RFA compared to resection alone. High postoperative IL-6 and HGF levels negatively influenced overall survival (OS) independently of the treatment group.

CONCLUSION

This pilot study demonstrates that RFA might influence tumor cell dissemination. There exist detectable differences in serum factors between RFA and liver resection after the operation but this did not influence the overall survival of the patients. For all patients, high postoperative IL-6 and HGF levels are negative prognostic markers.

Homoharringtonine, a clinically approved anti-leukemia drug, sensitizes tumor cells for TRAIL-induced necroptosis

BACKGROUND

One hallmark of cancer cells is their ability to evade physiologic signals causing regulated cell death (RCD). Correspondingly, TRAIL-based therapies to eliminate human cancer cells via enforced induction of apoptosis have been established and represent a promising approach in anti-cancer research. However, due to frequently appearing intrinsic or acquired resistances of tumor cells against apoptosis, TRAIL-based apoptotic strategies for the treatment of cancer patients have shown limited efficacy. As a potential alternative, regulated necrosis (and necroptosis triggered e.g. by TRAIL receptors 1/2) has recently gained considerable attention. Regulated necrosis represents a mode of RCD molecularly distinct from apoptosis whose potential in anti-cancer therapy is almost uncharacterized. Since in most cancer cells survival pathways counteract the effects of TRAIL-induced RCD, sensitizers such as cycloheximide (CHX) are frequently added in cell culture to overcome this problem. Unfortunately, those sensitizers are cytotoxic and therefore not suitable for the treatment of cancer patients. Here, we have alternatively employed homoharringtonine (HHT), a plant alkaloid which was recently approved by the U. S. Food and Drug Administration to treat patients with chronic myeloid lymphoma.

RESULTS

We show that HHT is an efficient sensitizer for TRAIL-induced necroptosis in multiple human cancer cell lines. In addition, HHT-enhanced TRAIL-mediated necroptosis occurs via the same signaling pathways (involving RIPK1/RIPK3/MLKL) as CHX-enhanced necroptosis. Importantly, consecutive treatment schedules of necroptosis and apoptosis in either combination revealed remarkable additive effects not reached by repetitive apoptotic treatments alone.

CONCLUSIONS

Taken together, our data demonstrate that HHT can replace harmful substances such as CHX to sensitize human cancer cells to TRAIL-induced necroptosis. Thus, HHT represents a promising enhancer in TRAIL-based necroptotic anti-cancer therapies also in patients.

Cancer cell-autonomous TRAIL-R signaling promotes KRAS-driven cancer progression, invasion, and metastasis

Many cancers harbor oncogenic mutations of KRAS. Effectors mediating cancer progression, invasion, and metastasis in KRAS-mutated cancers are only incompletely understood. Here we identify cancer cell-expressed murine TRAIL-R, whose main function ascribed so far has been the induction of apoptosis as a crucial mediator of KRAS-driven cancer progression, invasion, and metastasis and in vivo Rac-1 activation. Cancer cell-restricted genetic ablation of murine TRAIL-R in autochthonous KRAS-driven models of non-small-cell lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDAC) reduces tumor growth, blunts metastasis, and prolongs survival by inhibiting cancer cell-autonomous migration, proliferation, and invasion. Consistent with this, high TRAIL-R2 expression correlates with invasion of human PDAC into lymph vessels and with shortened metastasis-free survival of KRAS-mutated colorectal cancer patients.

Inhibition of IL-6 signaling significantly reduces primary tumor growth and recurrencies in orthotopic xenograft models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal human tumors, with radical surgical resection as the only curative treatment option. However, resection is only possible in a small fraction of patients, and about 80% of the patients develop recurrencies. PDAC development is facilitated by the cytokine interleukin-6 (IL-6), which acts via classic and trans-signaling. Both pathways are inhibited by the anti-IL-6-receptor antibody tocilizumab, whereas the fusion protein sgp130Fc specifically blocks trans-signaling. Here, we show that conservative or adjuvant therapy with both inhibitors reduces tumor growth in an orthotopic model of human Colo357 cells in SCID/bg mice. In the conservative setting, median primary tumor weight was reduced 2.4-fold for tocilizumab and 4.4-fold for sgp130Fc. sgp130Fc additionally led to a decrease in microvessel density, which was not observed with tocilizumab. In the adjuvant therapeutic setting after surgical resection of the primary tumor, treatment with tocilizumab or sgp130Fc decreased the local recurrence rate from 87.5% in the control group to 62.5 or 50%, respectively. Furthermore, the median weight of the local recurrent tumors was clearly diminished, and both inhibitors reduced the number of distant metastases. A significant reduction of tumor weight and metastases-comparable to gemcitabine treatment-was also observed with both inhibitors in another model using the poorly differentiated PancTuI cells. Our findings demonstrate the inhibition of IL-6 as a new treatment option in PDAC.

Circulating APRIL levels are correlated with advanced disease and prognosis in rectal cancer patients

We have previously shown that the tumor necrosis factor family member a proliferation-inducing ligand (APRIL) enhances intestinal tumor growth in various preclinical tumor models. Here, we have investigated whether APRIL serum levels at time of surgery predict survival in a large cohort of colorectal cancer (CRC) patients. We measured circulating APRIL levels in a cohort of CRC patients (n=432) using a novel validated monoclonal APRIL antibody (hAPRIL.133) in an enzyme-linked immunosorbent assay (ELISA) setup. APRIL levels were correlated with clinicopathological features and outcome. Overall survival was examined with Kaplan–Meier survival analysis, and Cox proportional hazards ratios were calculated. We observed that circulating APRIL levels were normally distributed among CRC patients. High APRIL expression correlated significantly with poor outcome measures, such as higher stage at presentation and development of lymphatic and distant metastases. Within the group of rectal cancer patients, higher circulating APRIL levels at time of surgery were correlated with poor survival (log-rank analysis P-value 0.008). Univariate Cox regression analysis for overall survival in rectal cancer patients showed that patients with elevated circulating APRIL levels had an increased risk of poor outcome (hazard ratio (HR) 1.79; 95% confidence interval (CI) 1.16–2.76; P-value 0.009). Multivariate analysis in rectal cancer patients showed that APRIL as a prognostic factor was dependent on stage of disease (HR 1.25; 95% CI 0.79–1.99; P-value 0.340), which was related to the fact that stage IV rectal cancer patients had significantly higher levels of APRIL. Our results revealed that APRIL serum levels at time of surgery were associated with features of advanced disease and prognosis in rectal cancer patients, which strengthens the previously reported preclinical observation of increased APRIL levels correlating with disease progression.

Combined evaluation of a panel of protein and miRNA serum-exosome biomarkers for pancreatic cancer diagnosis increases sensitivity and specificity

Late diagnosis contributes to pancreatic cancer (PaCa) dismal prognosis, urging for reliable, early detection. Serum-exosome protein and/or miRNA markers might be suitable candidates, which we controlled for patients with PaCa. Protein markers were selected according to expression in exosomes of PaCa cell line culture supernatants, but not healthy donors' serum-exosomes. miRNA was selected according to abundant recovery in microarrays of patients with PaCa, but not healthy donors' serum-exosomes and exosome-depleted serum. According to these preselections, serum-exosomes were tested by flow cytometry for the PaCa-initiating cell (PaCIC) markers CD44v6, Tspan8, EpCAM, MET and CD104. Serum-exosomes and exosome-depleted serum was tested for miR-1246, miR-4644, miR-3976 and miR-4306 recovery by qRT-PCR. The majority (95%) of patients with PaCa (131) and patients with nonPa-malignancies reacted with a panel of anti-CD44v6, -Tspan8, -EpCAM and -CD104. Serum-exosomes of healthy donors' and patients with nonmalignant diseases were not reactive. Recovery was tumor grading and staging independent including early stages. The selected miR-1246, miR-4644, miR-3976 and miR-4306 were significantly upregulated in 83% of PaCa serum-exosomes, but rarely in control groups. These miRNA were also elevated in exosome-depleted serum of patients with PaCa, but at a low level. Concomitant evaluation of PaCIC and miRNA serum-exosome marker panels significantly improved sensitivity (1.00, CI: 0.95-1) with a specificity of 0.80 (CI: 0.67-0.90) for PaCa versus all others groups and of 0.93 (CI: 0.81-0.98) excluding nonPa-malignancies. Thus, the concomitant evaluation of PaCIC and PaCa-related miRNA marker panels awaits retrospective analyses of larger cohorts, as it should allow for a highly sensitive, minimally-invasive PaCa diagnostics.

Abstract 2955: Trail-R2: A death receptor turns malignant upon nuclear localization

High intracellular expression of death receptor TRAIL-R2 correlates with poor prognosis for different tumor entities and thus suggests tumor-promoting activity of intracellular TRAIL-R2. We demonstrate that TRAIL-R2 interacts with the core Microprocessor components Drosha and DGCR8 and the associated regulatory proteins p68, hnRNPA1, NF45 and NF90 in the nucleus. Knockdown of TRAIL-R2 enhances Drosha-mediated processing of pri-let-7 resulting in increased levels of mature let-7, reduced expression of let-7-targets Lin28B and HMGA2 and inhibition of cell proliferation. In contrast, high abundance of nuclear TRAIL-R2, often detected in pancreatic cancer, correlates with enhanced expression of HMGA2 and dictates worse prognosis. Importantly, knockdown of TRAIL-R2 inhibits pancreatic tumor growth in an orthotopic xenotransplantation mouse model and reduced nuclear levels of TRAIL-R2 accompany differentiation of pancreatic epithelial cells in vitro. In conclusion, we define a novel function of nuclear TRAIL death receptor contributing to malignancy by inhibition of let-7-maturation (Haselmann et al., Gastroenterology epub ahead of print).

In extension to our work on pancreatic cancer we further show nuclear TRAIL-R2 functions to be of relevance in breast cancer bone metastasis. Stably shRNA- transfected clones of MDAMB231 cells revealed metastatic lesions in only 2/12 mice upon TRAIL-R2 knock-down, whereas TRAIL-R1 and control knock-down clones exhibited multiple metastases throughout the groups of 12 mice each. Under in vitro conditions some decreased apoptosis rate was observed in both TRAIL-R knock-down clonal populations compared to the controls upon TRAIL treatment. Preliminary results suggest Mesenchymal-Epithelial-Transition (as indicated by increased E-Cadherin expression in TRAIL-R2 knock-down cells) as a mechanism for reduced metastasis.

In summary, we show nuclear death receptor TRAIL-R2 to significantly contribute to malignant progression in two different pre-clinical tumor models. Thus, targeted intervention to prevent nuclear localization may serve as a novel therapeutic strategy.

Supported by DFG (TR 1063/2-1 and TR 1063/3-1 - SKELMET FOR 1586).

Citation Format: Holger Kalthoff, Verena Haselmann, Alexandra Kurz, Uwe Bertsch, Sebastian Huebner, Hendrik Fritsche, Charlotte Hauser, Christian Schem, Rob Tower, Thorsten Heilmann, Sanjay Tiwari, Claus C. Glüer, Anna Trauzold. Trail-R2: A death receptor turns malignant upon nuclear localization. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2955. doi:10.1158/1538-7445.AM2014-2955

Compartmentalization of TNF-related apoptosis-inducing ligand (TRAIL) death receptor functions: emerging role of nuclear TRAIL-R2

Localized in the plasma membrane, death domain-containing TNF-related apoptosis-inducing ligand (TRAIL) receptors, TRAIL-R1 and TRAIL-R2, induce apoptosis and non-apoptotic signaling when crosslinked by the ligand TRAIL or by agonistic receptor-specific antibodies. Recently, an increasing body of evidence has accumulated that TRAIL receptors are additionally found in noncanonical intracellular locations in a wide range of cell types, preferentially cancer cells. Thus, besides their canonical locations in the plasma membrane and in intracellular membranes of the secretory pathway as well as endosomes and lysosomes, TRAIL receptors may also exist in autophagosomes, in nonmembraneous cytosolic compartment as well as in the nucleus. Such intracellular locations have been mainly regarded as hide-outs for these receptors representing a strategy for cancer cells to resist TRAIL-mediated apoptosis. Recently, a novel function of intracellular TRAIL-R2 has been revealed. When present in the nuclei of tumor cells, TRAIL-R2 inhibits the processing of the primary let-7 miRNA (pri-let-7) via interaction with accessory proteins of the Microprocessor complex. The nuclear TRAIL-R2-driven decrease in mature let-7 enhances the malignancy of cancer cells. This finding represents a new example of nuclear activity of typically plasma membrane-located cytokine and growth factor receptors. Furthermore, this extends the list of nucleic acid targets of the cell surface receptors by pri-miRNA in addition to DNA and mRNA. Here we review the diverse functions of TRAIL-R2 depending on its intracellular localization and we particularly discuss the nuclear TRAIL-R2 (nTRAIL-R2) function in the context of known nuclear activities of other normally plasma membrane-localized receptors.

Interleukin-6: a villain in the drama of pancreatic cancer development and progression

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a poor prognosis and little treatment options. The development and progression of the disease is fostered by inflammatory cells and cytokines. One of these cytokines is interleukin-6 (IL-6), which plays an important role in a wide range of biologic activities.

DATA SOURCES

A systematic search of PubMed was performed to identify relevant studies using key words such as interleukin-6, inflammatory cytokines, inflammation and pancreatic cancer or PDAC. Articles related to IL-6 and pancreatic cancer were systematically reviewed.

RESULTS

IL-6 is elevated in the serum of pancreatic cancer patients and correlates with cachexia, advanced tumor stage and poor survival. Its expression is enhanced by hypoxia and proteins involved in pancreatic cancer development like Kras, mesothelin or ZIP4. IL-6 in turn contributes to the generation of a pro-tumorigenic microenvironment and is probably involved in angiogenesis and metastasis. In experimental mouse models of PDAC, IL-6 was important for the development and progression of precursor lesions.

CONCLUSION

IL-6 emerges as a key player in pancreatic cancer development and progression, and hence should be considered as a new therapeutic target.

Comparative characterization of stroma cells and ductal epithelium in chronic pancreatitis and pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extensive stroma being also present in chronic pancreatitis (CP). Using immunohistochemistry, the stroma of CP and PDAC was comprehensively analyzed and correlated with epithelial/carcinoma-related alterations and clinicopathological patient characteristics. While there were no significant differences between CP and PDAC regarding the distribution of CD3+ T cells and α-SMA+ fibroblasts, proportions of CD4+ and CD8+ T cells were significantly lower and numbers of CD25+(CD4+) and FoxP3+(CD4+) regulatory T cells were greater in PDAC compared with CP. Macrophages were more prevalent in CP, but localized more closely to carcinoma cells in PDAC, as were γδ-T cells. Duct-related FoxP3 and L1CAM expression increased from CP to PDAC, while vimentin expression was similarly abundant in both diseases. Moreover, stromal and epithelial compartments of well-differentiated tumors and CPs shared considerable similarities, while moderately and poorly differentiated tumors significantly differed from CP tissues. Analysis of 27 parameters within each pancreatic disease revealed a significant correlation of i) CD4+ and FoxP3+CD4+ T cells with FoxP3 expression in PDAC cells, ii) α-SMA+ fibroblasts with L1CAM expression and proliferation in PDAC cells, iii) CD3 and CD8 expression with γδ-TCR expression in both pancreatic diseases and iv) CD68+ and CD163+ macrophages with vimentin expression in PDAC cells. High expression of FoxP3, vimentin and L1CAM in PDAC cells as well as a tumor-related localization of macrophages each tended to correlate with higher tumor grade. Multivariate survival analysis revealed a younger age at time of surgery as a positive prognostic marker for PDAC patients with the most frequently operated disease stage T3N1M0. Overall this study identified several interrelationships between stroma and epithelial/carcinoma cells in PDACs but also in CP, which in light of previous experimental data strongly support the view that the inflammatory stroma contributes to malignancy-associated alterations already in precursor cells during CP.