Loss of TRAIL-receptors is a recurrent feature in pancreatic cancer and determines the prognosis of patients with no nodal metastasis after surgery

INTRODUCTION

Agonistic antibodies targeting TRAIL-receptors 1 and 2 (TRAIL-R1 and TRAIL-R2) are being developed as a novel therapeutic approach in cancer therapy including pancreatic cancer. However, the cellular distribution of these receptors in primary pancreatic cancer samples has not been sufficiently investigated and no study has yet addressed the issue of their prognostic significance in this tumor entity.

AIMS AND METHODS

Applying tissue microarray (TMA) analysis, we performed an immunohistochemical assessment of TRAIL-receptors in surgical samples from 84 consecutive patients affected by pancreatic adenocarcinoma and in 26 additional selected specimens from patients with no lymph nodes metastasis at the time of surgery. The prognostic significance of membrane staining and staining intensity for TRAIL-receptors was evaluated.

RESULTS

The fraction of pancreatic cancer samples with positive membrane staining for TRAIL-R1 and TRAIL-R2 was lower than that of cells from surrounding non-tumor tissues (TRAIL-R1: p<0.001, TRAIL-R2: p = 0.006). In addition, subgroup analyses showed that loss of membrane staining for TRAIL-R2 was associated with poorer prognosis in patients without nodal metastases (multivariate Cox regression analysis, Hazard Ratio: 0.44 [95% confidence interval: 0.22-0.87]; p = 0.019). In contrast, analysis of decoy receptors TRAIL-R3 and -R4 in tumor samples showed an exclusively cytoplasmatic staining pattern and no prognostic relevance.

CONCLUSION

This is a first report on the prognostic significance of TRAIL-receptors expression in pancreatic cancer showing that TRAIL-R2 might represent a prognostic marker for patients with early stage disease. In addition, our data suggest that loss of membrane-bound TRAIL-receptors could represent a molecular mechanism for therapeutic failure upon administration of TRAIL-receptors-targeting antibodies in pancreatic cancer. This hypothesis should be evaluated in future clinical trials.

Heat shock protein 27 as a prognostic and predictive biomarker in pancreatic ductal adenocarcinoma

A role of heat shock protein 27 (HSP27) as a potential biomarker has been reported in various tumour entities, but comprehensive studies in pancreatic cancer are lacking. Applying tissue microarray (TMA) analysis, we correlated HSP27 protein expression status with clinicopathologic parameters in pancreatic ductal adenocarcinoma specimens from 86 patients. Complementary, we established HSP27 overexpression and RNA-interference models to assess the impact of HSP27 on chemo- and radiosensitivity directly in pancreatic cancer cells. In the TMA study, HSP27 expression was found in 49% of tumour samples. Applying univariate analyses, a significant correlation was found between HSP27 expression and survival. In the multivariate Cox-regression model, HSP27 expression emerged as an independent prognostic factor. HSP27 expression also correlated inversely with nuclear p53 accumulation, indicating either protein interactions between HSP27 and p53 or TP53 mutation-dependent HSP27-regulation in pancreatic cancer. In the sensitivity studies, HSP27 overexpression rendered HSP27 low-expressing PL5 pancreatic cancer cells more susceptible towards treatment with gemcitabine. Vice versa, HSP27 protein depletion in HSP27 high-expressing AsPC-1 cells caused increased gemcitabine resistance. Importantly, HSP27 expression was inducible in pancreatic cancer cell lines as well as primary cells. Taken together, our study suggests a role for HSP27 as a prognostic and predictive marker in pancreatic cancer. Assessment of HSP27 expression could thus facilitate the identification of specific patient subpopulations that might benefit from individualized treatment options. Additional studies need to clarify whether modulation of HSP27 expression could represent an attractive concept to support the incorporation of hyperthermia in clinical treatment protocols for pancreatic cancer.

Effect of raloxifene on human pancreatic adenocarcinoma growth in vitro and in vivo

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Background: The role of estrogen receptor (ER) signaling in pancreatic cancer is unknown. Recently, we demonstated that expression of the isoform ER beta correlates with an adverse prognosis in patients with pancreatic cancer. Here, we show that raloxifene, a specific estrogen receptor modulator (SERM), suppresses in vitro and in vivo tumor growth by interfering with ER beta signaling in human pancreatic adenocarcinoma.

Methods: The human pancreatic adenocarcinoma cell line L3.6pl was cultured and exposed to raloxifene in vitro, and cell proliferation was determined by the BrdU assay. To analyze the specificity of raloxifene induced effects, ER knockdown was performed using siRNA specific for ER alpha and ER beta. In an in vivo model of orthotopic tumor xenografts in nude mice, raloxifene was administered daily, and tumor growth was monitored. Expression of ER beta and the proliferation marker Ki-67 were determined by immunohistochemistry.

Results: Raloxifene treatment resulted in a potent, dose dependent reduction of proliferation in vitro over a nanomolar dose range. This effect was completely reversed by siRNA knockdown of ER beta, but not ER alpha, indicating an ER isotype specific signaling. In vivo, orthotopic tumor growth, as well as lymph node and liver metastases, was significantly suppressed in raloxifene treated mice. Analogous to the in vitro data, Ki-67 expression in vivo was significantly reduced in raloxifene treated mice, while ER beta expression was not changed in vivo.

Conclusions: Inhibition of ER beta signaling by raloxifene results in a potent reduction of human pancreatic adenocarcinoma growth in vitro and in vivo. Treatment with SERMs may be an attractive therapeutic option in subjects expressing the ER beta isotype.

No significant financial relationships to disclose.

Src tyrosine kinase inhibition suppresses lymphangiogenesis in vitro and in vivo

PURPOSE

The close association of lymphatic and blood vessels and their coordinated development in vivo suggest that there are parallel mechanisms regulating hemangiogenesis and lymphangiogenesis. Here, we hypothesize that inhibition of the Src tyrosine kinase, apart from anti-hemangiogenic effects, results in a suppression of lymphangiogenesis.

EXPERIMENTAL DESIGN

The ability of the Src kinase inhibitor PP2 to block Src in isolated lymphatic endothelial cells (LECs) was analyzed by Western Blot. The effects of PP2 on LEC proliferation, migration, and sprouting were assessed by MTT, Boyden chamber, and spheroid assays, respectively. The level of VEGF-C secreted by L3.6pl pancreatic carcinoma cells was measured by ELISA. For in vivo assessment of lymphangiogenesis, Src kinase inhibitor AZM475271 was used in mouse corneal micropocket and lymphangioma models.

RESULTS

VEGF-C stimulation of isolated LECs led to an increased phosphorylation of Src kinase that was abrogated by PP2. Treatment with PP2 inhibited spheroid sprouting of LECs at even lower concentrations than suggested by the proliferation assay. Src inhibition significantly reduced the level of VEGF-C in L3.6pl supernatant. Treatment with PP2 also resulted in a significant reduction in the migratory activity of LECs. In vivo, Src inhibition reduced de novo formation of lymphangiomas and corneal neovascularization.

CONCLUSIONS

Inhibition of Src kinase shows strong anti-lymphangiogenic activity in vitro and in vivo. Together with anti-angiogenic effects mediated by Src inhibition, this strategy may be attractive in the treatment of lymphatic and hematogeneous metastasis of cancer.

Abstract 1330: Low dose irradiation reverts chemoresistance towards fluorouracil in human pancreatic adenocarcinoma cells by upregulation of thymidine phosphorylase

Background: Resistance towards cytotoxic drugs and ionizing radiation (IR) accounts for poor therapy response in pancreatic cancer. The radiosensitizing effects of fluorouracil (FU) are well characterized, however, it is not known whether IR itself exerts sensitizing effects towards cytotoxic chemotherapy. Here, we hypothesize that IR induced upregulation of thymidine phosphorylase (TP) results in a reversal of resistance towards FU.

Methods: An FU resistant variant of the human pancreatic adenocarcinoma cell line AsPC-1 was developed by long term in vitro FU exposure. Proliferation of AsPC-1 and AsPC-1FUres cells was determined by an MTT proliferation assay after previous low dose (0.05 Gy) exposure of IR. To antagonize a possible effect mediated by TP upregulation, anti-TP siRNA was added in the same setting. TP expression in AsPC-1 cells before and after IR was determined by Western blotting.

Results: FU resistant AsPC-1 cells showed a 7.5-fold increase of the IC50 after FU exposure, compared to non-resistant cells. When challenging both cell lines with FU after low dose IR, no significant difference of proliferation was observed in AsPC-1 cells and their FU resistant variant, suggesting a reversal of chemoresistance by IR. This chemosensitizing effect was abrogated when blocking TP by anti-TP siRNA before IR. In cell lysates harvested from AsPC-1 cells, an increase of TP expression was seen after exposure of low dose IR (0.05 Gy) as well as high dose IR (2.0 Gy).

Conclusion: Our results suggest a TP mediated reversal of chemoresistance towards FU that is triggered by low dose IR in vitro. These results have to be confirmed in an in vivo model. In conclusion, induction of TP expression by low dose irradiation may be an interesting concept to overcome chemotherapy resistance in pancreatic cancer.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1330.

Abstract 3911: Dysegulation of Sox9-dependent gene expression leads to enhancement of angiogenesis and metastases in pancreatic cancer

Background: The understanding of invasion, angiogenesis and metastasis is essential for the development of new targeted molecular therapy against pancreatic cancer. The aim of this study is to analyse the regulation of differentially expressed genes in highly proangiogenic and prometastatic compared to low metastatic and low angiogenic pancreatic cancer cells

Materials and methods: The transcriptome of the low metastatic pancreatic cancer cell line and its highly angiogenic and metastatic derivate L3.6pl have been compared under the normoxic and hypoxic conditions using Affymetrix HGU133plus 2.0 arrays. The hierarchic cluster analysis has been performed using SOTA algorithm. Promoters of the differentially expressed genes have been analysed using oPOSSUM 2 program. Affymetrix data have been validated via qRT-PCR and via ELISA. Chromosomal DNA containing promoters of the relevant genes has been amplified via PCR and sequenced.

Results: The Affymetrix analysis revealed clusters of differentially regulated genes with regard to the cell line and the oxygen level. While VEGF expression was upregulated in FG cells under hypoxic condition, it was constitutively upregulated already under normoxic conditions in L3.6pl and no further stimulation was observed under hypoxic conditions. This regulation pattern was similar in a cluster of genes that share a promoter sequence coding for a binding site for the transcription factor Sox9. Sox9 itself shows a similar regulation, leading to the assumption that expression changes of Sox9 are involved in the different hypoxic gene expressions. Promoter analysis of Sox9 in FG and L3.6pl cells showed mutations in the promoter region in L3.6pl, while the VEGF promoter was unchanged. Further analysis has shown that this mutation is not relevant for biological function. Refined analysis revealed differential Sox9 promoter methylation as reason for observed phenomenon.

Conclusions: Proangiogenic genes such as VEGF are upregulated in the more aggressive cell line L3.6pl, compared to FG. We identified a gene cluster that is constitutively upregulated in L3.6pl, independent of hypoxia. These genes are controlled by the transcription factor Sox9. A Sox9 promoter differential methylation may be the reason for the escape from hypoxic regulation in L3.6pl cells and thus may contribute to the higher angiogenic and metastatic potential. Taken together, Sox9 may be an interesting new diagnostic and therapeutic target in pancreatic cancer progression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3911.

Abstract 3901: Sox9-associated overexpression of IFIT3 leads to pancreatic cancer progression by activation of “pseudoinflammatory” pathways

The understanding of invasion, angiogenesis and metastasis is essential for the development of new molecular therapy against cancer. Inflammation plays important role in tumour initiation and progression. Here we report the role of the transcription factor Sox9 for regulation of IFIT3 an inflammation-related and tumour-promoting protein in pancreatic cancer. For in vivo and in vitro experiments we utilized the following human pancreatic cancer cell lines: low metastatic FG, high metastatic L3.6pl, and the stable transfected cell line FG-IFIT3. To demonstrate effects on primary tumor growth and metastases in vivo we orthotopically injected the different cell lines in the pancreas of nude mice. To evaluate the VEGF depending angiogenic capacity of the different cell lines ELISA technology was used. By One STrEP technology we were able to identify IFIT3-binding partners. Chromosomal immunoprecipitation (ChIP) using anti-Sox9 antibody, followed by PCR amplifying the IFIT3-promoter was used to identify the interaction of the IFIT3 promoter with the transcription factor Sox9. To investigate Sox9-depending expression of IFIT3 (protein and RNA) we used stable transfected L3.6pl-Sox9-shRNA cells under control of the Tet-CMV promoter in presence or absence of tetracycline, respectively. Analysis of differential gene expression by gene array technology demonstrated that the IFIT3 gene is up-regulated in L3.6pl cells as compared to FG cells. Results of animal experiment and in vitro experiments clearly demonstrated tumor-promoting, pro-metastatic and pro-angiogenic features of IFIT3. RT-PCR has revealed that both treatment with IFna as well as NFkB led to up-regulation of IFIT3-RNA expression. One STrEP experiments identified JNK and STAT1 as binding partners of IFIT3. ChIP has demonstrated binding of the transcription factor Sox9 to the IFIT3 promoter. RT-PCR and immunoblot data demonstrated constitutive up-regulation of Sox9 expression in L3.6pl cells. By Western blotting and RT-PCR we could show that diminishing of Sox9 expression in stable transfected L3.6pl Sox9-shRNA cells leads to a significant down-regulation of IFIT3-epression on the RNA and protein level.

The inflammation associated protein IFIT3 is up-regulated in metastatic L3.6pl human pancreatic cancer cells and is in part responsible for the aggressive primary pancreatic tumor growth in vivo. This gene is up-regulated by IFna and NFkB. Interestingly Sox9 binds to the IFIT3P and activates its expression. Since in L3.6pl cells Sox9 is constitutively over-expressed, IFIT3 is up-regulated independent on the presence of the cytokine IFna. Therefore, the pro-inflammatory IFna-signaling pathway is activated even without actual inflammation in absence pro-inflammatory cytokine. The activation of such a “pseudo-inflammatory pathway” seems to be in part responsible for pancreatic cancer progression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3901.

EFEMP1 binds the EGF receptor and activates MAPK and Akt pathways in pancreatic carcinoma cells

The EGF-related protein EFEMP1 (EGF-containing fibulin-like extracellular matrix protein 1) has been shown to promote tumor growth in human adenocarcinoma. To understand the mechanism of this action, the signal transduction activated upon treatment with this protein has been investigated. We show that EFEMP1 binds EGF receptor (EGFR) in a competitive manner relative to epidermal growth factor (EGF), implicating that EFEMP1 and EGF share the same or adjacent binding sites on the EGFR. Treatment of pancreatic carcinoma cells with purified EFEMP1 activates autophosphorylation of EGFR at the positions Tyr-992 and Tyr-1068, but not at the position Tyr-1048. This signal is further transduced to phosphorylation of Akt at position Thr-308 and p44/p42 MAPK (mitogen-activated protein kinase) at positions Thr-202 and Tyr-204. These downstream phosphorylation events can be inhibited by treatment with the EGFR kinase inhibitor PD 153035. The observed signal transduction upon treatment with EFEMP1 can contribute to the enhancement of tumor growth shown in pancreatic carcinoma cells overexpressing EFEMP1.

Determinants of morbidity and survival after elective non-curative resection of stage IV colon and rectal cancer

PURPOSE

The benefit of elective primary tumor resection for non-curable stage IV colorectal cancer (CRC) remains largely undefined. We wanted to identify risk factors for postoperative complications and short survival.

METHODS

Using a prospective database, we analyzed potential risk factors in 233 patients, who were electively operated for non-curable stage IV CRC between 1996 and 2002. Patients with recurrent tumors, resectable metastases, emergency operations, and non-resective surgery were excluded. Risk factors for increased postoperative morbidity and limited postoperative survival were identified by multivariate analyses.

RESULTS

Patients with colon cancer (CC = 156) and rectal cancer (RC = 77) were comparable with regard to age, sex, comorbidity, American Society of Anesthesiologists score, carcinoembryonic antigen levels, hepatic spread, tumor grade, resection margins, 30-day mortality (CC 5.1%, RC 3.9%) and postoperative chemotherapy. pT4 tumors, carcinomatosis, and non-anatomical resections were more common in colon cancer patients, whereas enterostomies (CC 1.3%, RC 67.5%, p < 0.0001), anastomotic leaks (CC 7.7%, RC 24.2%, p = 0.002), and total surgical complications (CC 19.9%, RC 40.3%, p = 0.001) were more frequent after rectal surgery. Independent determinants of an increased postoperative morbidity were primary rectal cancer, hepatic tumor load >50%, and comorbidity >1 organ. Prognostic factors for limited postoperative survival were hepatic tumor load >50%, pT4 tumors, lymphatic spread, R1-2 resection, and lack of chemotherapy.

CONCLUSIONS

Palliative resection is associated with a particularly unfavorable outcome in rectal cancer patients presenting with a locally advanced tumor (pT4, expected R2 resection) or an extensive comorbidity, and in all CRC patients who show a hepatic tumor load >50%. For such patients, surgery might be contraindicated unless the tumor is immediately life-threatening.

Blumgart anastomosis for pancreaticojejunostomy minimizes severe complications after pancreatic head resection

BACKGROUND

Leakage from the pancreaticojejunostomy is the major cause of septic complications after partial pancreaticoduodenectomy. This study evaluated a new transpancreatic U-suture technique (Blumgart anastomosis, BA), which aims to avoid shear forces during knot-tying.

METHODS

Using a before-after study design, BA was compared with a modified Cattell-Warren anastomosis (CWA). Two patient cohorts (CWA, 90; BA, 92), which were similar with respect to primary diagnosis, age, sex and American Society of Anesthesiologists score, were compared retrospectively. Dependent variables were surgical and overall morbidity and mortality after partial pancreaticoduodenectomy.

RESULTS

Duration of operation (354 versus 328 min for CWA versus BA; P = 0.002), pancreatic leakage rate (13 versus 4 per cent; P = 0.032), postoperative haemorrhage (11 versus 3 per cent; P = 0.040), total surgical complications (31 versus 15 per cent; P = 0.011), general complications (36 versus 17 per cent; P = 0.005) and length of intensive care unit stay (median 5.4 versus 2.8 days; P = 0.015) were significantly reduced after BA. These effects were not related merely to an improvement over time.

CONCLUSION

BA appears to be a fast, simple and safe technique for pancreaticojejunostomy. It might reduce leakage rates and surgical complications after partial pancreaticoduodenectomy.

Pancreatic cancer stem cells: new understanding of tumorigenesis, clinical implications

PURPOSE

Since the discovery of cancer cells with stem-like characteristics in hematopoietic malignancies and, more recently, in solid tumors, enormous attention has been paid to the stem-cell nature of pancreatic cancer. Among the most important properties of cancer stem cells their high capacity for tumorigenicity as well as their ability to metastasize is under special research interest today.

METHODS

Here, we give a brief overview of main components used to confirm the stem-cell-like behavior of putative cancer stem cells and discuss markers and methods for identifying them in pancreatic cancer. Finally, the review provides some new suggestions as to how specifically target these cells and improve current therapy regimens.

RESULTS

The cancer stem-cell hypothesis is a fundamentally different model of carcinogenesis composed of two separate but dependent on each other characteristics of stem cells--aberrant activation of their tightly regulated processes of self-renewal and differentiation and their resistance towards chemo- and radiotherapy. The cancer stem cells may further be identified based on their expression of cell surface markers or their functional characteristics. The concept of molecular targeting of such highly tumorigenic cancer cells aimed to sensitize tumors toward conventional therapies and effectively abrogate tumor growth and metastasis.

CONCLUSIONS

The presence of cancer stem cells in pancreatic tumors has prognostic relevance and influences therapeutic response. Evidence suggests that metastatic potential may be conferred to these highly tumorigenic cells as well. A better understanding of the biological behavior of these cells may further improve therapeutic approaches and outcomes in patients with this devastating disease.

Cancer stem cells: how can we target them?

One of the most exciting concepts being explored in cancer research today is the idea of cancer stem cells. Evidence for the existence of such cells was first proposed for haematological malignancies and, more recently, for solid tumors, including breast, brain, colon and pancreatic cancer. The cancer stem cell hypothesis states that a minority of transformed stem cells, or progenitors with acquired self-renewal properties, are the source of tumor cell renewal and thereby determine the behaviour of tumors, including proliferation, spreading and response to chemo- and radiotherapy. Indeed, just as somatic stem cells may be resistant to the induction of apoptosis by cytotoxic agents and radiation therapy, cancer stem cells may display increased resistance to these agents as compared with the more differentiated cells that comprise the mass of tumors. More specifically, the reactivation of varied developmental signalling cascades (epidermal growth factor (EGF)/EGFR, stem cell factor (SCF)/KIT, sonic hedgehog, Notch, and/or Wnt/beta-catenin) combined with the increased DNA repair mechanisms and ABC transporter-mediated drug efflux in cancer stem cells may be responsible for their resistance to conventional therapies. Furthermore, changes in the local microenvironment of cancer stem cells may also influence their behaviour. Thus, the molecular targeting of such highly tumorigenic cancer cells must be considered for improving the efficacy of the current anti-cancer strategies with the aim to sensitize tumors toward conventional therapies and effectively abrogate tumorigenesis. This review provides a summary of some developments in the field of cancer stem cell targeting and highlights aspects where it could be of help in the drug discovery process.

EFEMP1 expression promotes in vivo tumor growth in human pancreatic adenocarcinoma

The progression of pancreatic cancer is dependent on local tumor growth, angiogenesis, and metastasis. EFEMP1, a recently discovered member of the fibulin family, was characterized with regard to these key elements of pancreatic cancer progression. Differential gene expression was assessed by mRNA microarray hybridization in FG human pancreatic adenocarcinoma cells and L3.6pl cells, a highly metastatic variant of FG. In vivo orthotopic tumor growth of EFEMP1-transfected FG cells was examined in nude mice. To assess the angiogenic properties of EFEMP1, vascular endothelial growth factor (VEGF) production of tumor cells, endothelial cell proliferation and migration, and tumor microvessel density were analyzed in response to EFEMP1. Further, tumor cell apoptosis, cell cycle progression, and resistance to cytotoxic agents were quantitated by propidium iodide staining and flow cytometry. In microarray hybridization, EFEMP1 was shown to be significantly up-regulated in L3.6pl cells compared with FG cells. Concordantly, EFEMP1 transfection of FG cells stimulated orthotopic and metastatic tumor growth in vivo. EFEMP1 expression resulted in a stimulation of VEGF production by tumor cells and an increased number of CD31-positive microvessels. Endothelial cell proliferation and migration were not altered by EFEMP1, indicating an indirect angiogenic effect. Further, EFEMP1 expression decreased apoptosis and promoted cell cycle progression in response to serum starvation or exposure to gemcitabine, 5-fluorouracil, and irinotecan. EFEMP1 has protumorigenic effects on pancreatic cancer in vivo and in vitro mediated by VEGF-driven angiogenesis and antiapoptotic mechanisms. Hence, EFEMP1 is a promising candidate for assessing prognosis and individualizing therapy in a clinical tumor setting.

Matuzumab short-term therapy in experimental pancreatic cancer: prolonged antitumor activity in combination with gemcitabine

PURPOSE

The epidermal growth factor receptor ErbB-1 is commonly expressed in pancreatic cancer and ErbB-1 targeting has shown promising results. We wanted to evaluate matuzumab (EMD72000), a fully humanized ErbB-1-specific monoclonal antibody in combination with gemcitabine in experimental pancreatic cancer.

EXPERIMENTAL DESIGN

Using the human pancreatic cancer cell line L3.6pl, we investigated matuzumab in vitro and in vivo. ErbB-1 phosphorylation and downstream pathway activation were evaluated by Western blot. Proliferation and migration assays and fluorescence-activated cell sorting analysis were done. For in vivo studies, we used an orthotopic nude mice model in which 40 mg/kg of matuzumab+/-100 mg/kg of gemcitabine were administered twice weekly. Different treatment durations (7, 14, 21, and 25 days) and varying time points of treatment initiation (days 8, 15, 22, and 29) were evaluated. Ki67, CD31, and phosphorylated p44/42 mitogen-activated protein kinase (MAPK) immunohistochemistry were done.

RESULTS

ErbB-1 phosphorylation and downstream MAPK and AKT signaling were significantly reduced by matuzumab. Matuzumab significantly inhibited proliferation and migration in vitro, and induced tumor cell apoptosis in a dose-dependant manner. Matuzumab therapy significantly lowered tumor volume in vivo, reduced lymph node and liver metastases, and decreased microvessel density and tumor cell proliferation. These effects were significantly enhanced when gemcitabine was added. A significant and prolonged antitumor activity was even evident with short-term therapy (7 days) and with a late onset of therapy (day 22 after tumor cell injection).

CONCLUSIONS

Matuzumab is an effective agent with long-lasting antiproliferative, proapoptotic, antiangiogenic, and antimetastatic activity in human pancreatic cancer models. These effects might be potentiated by gemcitabine.

The challenge of pancreatic anastomosis

BACKGROUND AND AIMS

Significant progress in surgical technique and perioperative management has substantially reduced the mortality rate of pancreatic surgery. However, morbidity remains considerably high, even in expert hands and leakage from the pancreatic stump still accounts for the majority of surgical complications after pancreatic head resection. For that reason, management of the pancreatic remnant after partial pancreatoduodenectomy remains a challenge. This review will focus on technique, pitfalls, and complication management of pancreaticoenteric anastomoses.

MATERIALS AND METHODS

A medline search for surgical guidelines, prospective randomized controlled trials, systematic metaanalysis, and clinical reports was performed with regard to surgical technique and complication management of pancreatic anastomoses.

RESULTS

Pancreaticojejunostomy appears to be most widely performed, but pancreaticogastrostomy is a reasonable alternative. Postoperative treatment with octreotide can be recommended only for patients with soft pancreatic tissue, and neither stents of the pancreatic duct nor drainages have proven to effectively reduce anastomotic complications. Gastroparesis remains the most common complication after pancreatic surgery and should be treated conservatively. However, it may be a symptom of other local complications, such as anastomotic leakage, pancreatic fistula or abscess. All septic complications may finally result in late postoperative hemorrhage, which requires immediate diagnostic workup and therapy. Today, interventional radiology has emerged as a standard tool in the management of local septic complications and bleeding. Therefore, relaparotomy has become less frequent and salvage pancreatectomy is now a rare procedure in case of local complications.

CONCLUSION

The surgeon's experience with one or the other technique of pancreatic anastomosis appears to be more important than the technique itself.

Role of mTOR in solid tumor systems: a therapeutical target against primary tumor growth, metastases, and angiogenesis

The mammalian target of rapamycin (mTOR) is a controller of cell growth with multiple effects on cancer development and progression. Being closely linked to key oncogenic pathways that regulate tumor cell growth and cell cycle progression, mTOR integrates the cellular response to mitogenic and growth stimuli. Rapamycin and its analogs temsirolimus and everolimus are specific inhibitors of mTOR that exert suppressive effects on proliferation, invasion, and metastasis and induce apoptosis of tumor cells. Apart from the direct effects of mTOR inhibitors on tumor cells, rapamycin and its analogs have potent antiangiogenic properties related to the suppression of vascular endothelial growth factor signal transduction. While the use of mTOR inhibitors as a monotherapy seems to be insufficient to effectively control tumor progression in most tumor entities, combination with tyrosine kinase inhibitors or cytotoxic agents might potentiate the antitumoral effects of mTOR inhibition. In a clinical setting, mTOR inhibitors show an acceptable safety profile over a wide dose range. Currently, mTOR inhibitors are tested in multiple trials in combination with other agents in various cancer entities in intermittent schedules to avoid immunosuppression. However, lacking adequate surrogate and response parameters, the most effective biological dosing schedules remain to be defined. Considering these apparent limitations, the full clinical potential of this promising class of drugs is at risk to be missed by applying them inadequately.

Rapamycin induces tumor-specific thrombosis via tissue factor in the presence of VEGF

Therapeutic strategies that target and disrupt the already-formed vessel networks of growing tumors are actively pursued. The goal of these approaches is to induce a rapid shutdown of the vascular function of the tumor so that blood flow is arrested and tumor cell death occurs. Here we show that the mammalian target of rapamycin (mTOR) inhibitor rapamycin, when administered to tumor-bearing mice, selectively induced extensive local microthrombosis of the tumor microvasculature. Importantly, rapamycin administration had no detectable effect on the peritumoral or normal tissue. Intravital microscopy analysis of tumors implanted into skinfold chambers revealed that rapamycin led to a specific shutdown of initially patent tumor vessels. In human umbilical vein endothelial cells vascular endothelial growth factor (VEGF)–induced tissue factor expression was strongly enhanced by rapamycin. We further show by Western blot analysis that rapamycin interferes with a negative feedback mechanism controlling this pathologic VEGF-mediated tissue factor expression. This thrombogenic alteration of the endothelial cells was confirmed in a one-step coagulation assay. The circumstance that VEGF is up-regulated in most tumors may explain the remarkable selectivity of tumor vessel thrombosis under rapamycin therapy. Taken together, these data suggest that rapamycin, besides its known antiangiogenic properties, has a strong tumor-specific, antivascular effect in tumors.