Induction of apoptosis in tumor-associated endothelial cells and therapy of orthotopic human pancreatic carcinoma in nude mice

Metastasis and MAPK Pathways

Cancer is a leading cause of death worldwide. In many cases, the treatment of the disease is limited due to the metastasis of cells to distant locations of the body through the blood and lymphatic drainage. Most of the anticancer therapeutic options focus mainly on the inhibition of tumor cell growth or the induction of cell death, and do not consider the molecular basis of metastasis. The aim of this work is to provide a comprehensive review focusing on cancer metastasis and the mitogen-activated protein kinase (MAPK) pathway (ERK/JNK/P38 signaling) as a crucial modulator of this process.

Gemcitabine kills proliferating endothelial cells exclusively via acid sphingomyelinase activation

Gemcitabine is a widely-used anti-cancer drug with a well-defined mechanism of action in normal and transformed epithelial cells. However, its effect on endothelial cells is largely unknown. Acid sphingomyelinase (ASMase) is highly expressed in endothelial cells, converting plasma membrane sphingomyelin to pro-apoptotic ceramide upon activation by diverse stresses. In the current study, we investigated gemcitabine impact in primary cultures of endothelial cells. We find baseline ASMase increases markedly in bovine aortic endothelial cells (BAEC) as they transit from a proliferative to a confluent growth-arrested state. Further, gemcitabine activates ASMase and induces release of a secretory ASMase form into the media only in proliferating endothelial cells. Additionally, proliferative, but not growth-arrested BAEC, are sensitive to gemcitabine-induced apoptotic death, an effect blocked by inhibiting ASMase with imipramine or by binding ceramide on the cell surface with an anti-ceramide Ab. Confluent growth-arrested BAEC can be re-sensitized to gemcitabine-induced apoptosis by provision of exogenous sphingomyelinase. A highly similar phenotype was observed in primary cultures of human coronary artery endothelial cells. These findings reveal a previously-unrecognized mechanism of gemcitabine cytotoxicity in endothelium that may well contribute to its clinical benefit, and suggest the potential for further improvement of its clinical efficacy via pharmacologic modulation of ASMase/ceramide signaling in proliferative tumor endothelium.

The challenge of targeting metastasis

Metastases that are resistant to conventional therapy are the major cause of death from cancer. In most patients, metastasis has already occurred by the time of diagnosis. Thus, the prevention of metastasis is unlikely to be of therapeutic benefit. The biological heterogeneity of metastases presents a major obstacle to treatment. However, the growth and survival of metastases depend on interactions between tumor cells and host homeostatic mechanisms. Targeting these interactions, in addition to the tumor cells, can produce synergistic therapeutic effects against existing metastases.

Akt1 activity regulates vessel maturation in a tissue engineering model of angiogenesis

Akt kinase is a central signal transduction node that integrates extracellular cues that regulate cell migratory, proliferative, and morphological functions during angiogenesis. However, how Akt activity is modulated and contributes to subsequent vessel maturation is unclear. In this study we investigated the role of Akt1 in vessel maturation using human dermal microvascular endothelial cells (HDMVECs) expressing constitutively active and hemiphosphorylated Akt1 epi-alleles with graded kinase activity. HDMVECs expressing Akt1 epi-alleles were analyzed in vivo in a tissue engineering setting using a model of angiogenesis comprising cell-seeded poly-L-lactic acid scaffolds implanted subcutaneously into NOD/SCID murine hosts. The resultant intraimplant microvasculature was quantified for vascular parameters, including vessel diameter, perfusion, vascular density, and pericyte coverage. We found that constitutive Akt1 kinase activity in implanted HDMVECs correlated with loss of neovasculature function. Further, we found that the presence of coimplanted vascular smooth muscle cells (vSMCs) in the implants failed to promote blood vessel growth and maturation in a graded, Akt1 kinase activity-dependent manner. These results indicate that constitutive Akt1 activity disrupts the normal blood vessel growth and maturation. Therefore, we suggest that a downregulation of Akt1 activity is necessary for vSMC-induced maturation of newly formed blood vessels to occur.

Silencing Met receptor tyrosine kinase signaling decreased oral tumor growth and increased survival of nude mice

OBJECTIVES

The hepatocyte growth factor receptor (Met) is frequently overexpressed in Head and Neck Squamous Cell Carcinoma (HNSCC), correlating positively with high-grade tumors and shortened patient survival. As such, Met may represent an important therapeutic target. The purpose of this study was to explore the role of Met signaling for HNSCC growth and locoregional dissemination.

MATERIALS AND METHODS

Using a lentiviral system for RNA interference, we knocked down Met in established HNSCC cell lines that express high levels of the endogenous receptor. The effect of Met silencing on in vitro proliferation, cell survival and migration was examined using western analysis, immunohistochemistry and live cell imaging. In vivo tumor growth, dissemination and mouse survival was assessed using an orthotopic tongue mouse model for HNSCC.

RESULTS

We show that Met knockdown (1) impaired activation of downstream MAPK signaling; (2) reduced cell viability and anchorage independent growth; (3) abrogated HGF-induced cell motility on laminin; (4) reduced in vivo tumor growth by increased cell apoptosis; (5) caused reduced incidence of tumor dissemination to regional lymph nodes and (6) increased the survival of nude mice with orthotopic xenografts.

CONCLUSION

Met signaling is important for HNSCC growth and locoregional dissemination in vivo and that targeting Met may be an important strategy for therapy.

Dual HER/VEGF receptor targeting inhibits in vivo ovarian cancer tumor growth

Ovarian cancer mortality ranks highest among all gynecologic cancers with growth factor pathways playing an integral role in tumorigenesis, metastatic dissemination, and therapeutic resistance. The HER and VEGF receptor (VEGFR) are both overexpressed and/or aberrantly activated in subsets of ovarian tumors. While agents targeting either the HER or VEGF pathways alone have been investigated, the impact of these agents have not led to overall survival benefit in ovarian cancer. We tested the hypothesis that cotargeting HER and VEGFR would maximize antitumor efficacy at tolerable doses. To this end, ovarian cancer xenografts grown intraperitoneally in athymic nude mice were tested in response to AC480 (pan-HER inhibitor, "HERi"), cediranib (pan-VEGFR inhibitor "VEGFRi"), or BMS-690514 (combined HER/VEGFR inhibitor "EVRi"). EVRi was superior to both HERi and VEGFRi in terms of tumor growth, final tumor weight, and progression-free survival. Correlative tumor studies employing phosphoproteomic antibody arrays revealed distinct agent-specific alterations, with EVRi inducing the greatest overall effect on growth factor signaling. These data suggest that simultaneous inhibition of HER and VEGFR may benefit select subsets of ovarian cancer tumors. To this end, we derived a novel HER/VEGF signature that correlated with poor overall survival in high-grade, late stage, serous ovarian cancer patient tumors.

Met receptor tyrosine kinase signaling induces secretion of the angiogenic chemokine interleukin-8/CXCL8 in pancreatic cancer

At diagnosis, the majority of pancreatic cancer patients present with advanced disease when curative resection is no longer feasible and current therapeutic treatments are largely ineffective. An improved understanding of molecular targets for effective intervention of pancreatic cancer is thus urgent. The Met receptor tyrosine kinase is one candidate implicated in pancreatic cancer. Notably, Met is over expressed in up to 80% of invasive pancreatic cancers but not in normal ductal cells correlating with poor overall patient survival and increased recurrence rates following surgical resection. However the functional role of Met signaling in pancreatic cancer remains poorly understood. Here we used RNA interference to directly examine the pathobiological importance of increased Met signaling for pancreatic cancer. We show that Met knockdown in pancreatic tumor cells results in decreased cell survival, cell invasion, and migration on collagen I in vitro. Using an orthotopic model for pancreatic cancer, we provide in vivo evidence that Met knockdown reduced tumor burden correlating with decreased cell survival and tumor angiogenesis, with minimal effect on cell growth. Notably, we report that Met signaling regulates the secretion of the pro-angiogenic chemokine interleukin-8/CXCL8. Our data showing that the interleukin-8 receptors CXCR1 and CXCR2 are not expressed on pancreatic tumor cells, suggests a paracrine mechanism by which Met signaling regulates interleukin-8 secretion to remodel the tumor microenvironment, a novel finding that could have important clinical implications for improving the effectiveness of treatments for pancreatic cancer.

Multi-color palette of fluorescent proteins for imaging the tumor microenvironment of orthotopic tumorgraft mouse models of clinical pancreatic cancer specimens

Pancreatic-cancer-patient tumor specimens were initially established subcutaneously in NOD/SCID mice immediately after surgery. The patient tumors were then harvested from NOD/SCID mice and passaged orthotopically in transgenic nude mice ubiquitously expressing red fluorescent protein (RFP). The primary patient tumors acquired RFP-expressing stroma. The RFP-expressing stroma included cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs). Further passage to transgenic nude mice ubiquitously expressing green fluorescent protein (GFP) resulted in tumors that acquired GFP stroma in addition to their RFP stroma, including CAFs and TAMs as well as blood vessels. The RFP stroma persisted in the tumors growing in the GFP mice. Further passage to transgenic nude mice ubiquitously expressing cyan fluorescent protein (CFP) resulted in tumors acquiring CFP stroma in addition to persisting RFP and GFP stroma, including RFP- and GFP-expressing CAFs, TAMs and blood vessels. This model can be used to image progression of patient pancreatic tumors and to visually target stroma as well as cancer cells and to individualize patient therapy.

Macitentan (ACT-064992), a tissue-targeting endothelin receptor antagonist, enhances therapeutic efficacy of paclitaxel by modulating survival pathways in orthotopic models of metastatic human ovarian cancer

Potential treatments for ovarian cancers that have become resistant to standard chemotherapies include modulators of tumor cell survival, such as endothelin receptor (ETR) antagonist. We investigated the therapeutic efficacy of the dual ETR antagonist, macitentan, on human ovarian cancer cells, SKOV3ip1 and IGROV1, growing orthotopically in nude mice. Mice with established disease were treated with vehicle (control), paclitaxel (weekly, intraperitoneal injections), macitentan (daily oral administrations), or a combination of paclitaxel and macitentan. Treatment with paclitaxel decreased tumor weight and volume of ascites. Combination therapy with macitentan and paclitaxel reduced tumor incidence and further reduced tumor weight and volume of ascites when compared with paclitaxel alone. Macitentan alone occasionally reduced tumor weight but alone had no effect on tumor incidence or ascites. Immunohistochemical analyses revealed that treatment with macitentan and macitentan plus paclitaxel inhibited the phosphorylation of ETRs and suppressed the survival pathways of tumor cells by decreasing the levels of pVEGFR2, pAkt, and pMAPK. The dose of macitentan necessary for inhibition of phosphorylation correlated with the dose required to increase antitumor efficacy of paclitaxel. Treatment with macitentan enhanced the cytotoxicity mediated by paclitaxel as measured by the degree of apoptosis in tumor cells and tumor-associated endothelial cells. Collectively, these results show that administration of macitentan in combination with paclitaxel prevents the progression of ovarian cancer in the peritoneal cavity of nude mice in part by inhibiting survival pathways of both tumor cells and tumor-associated endothelial cells.

Modification of the primary tumor microenvironment by transforming growth factor alpha-epidermal growth factor receptor signaling promotes metastasis in an orthotopic colon cancer model

The transforming growth factor alpha (TGFalpha)/epidermal growth factor receptor (EGFR) signaling pathway appears to play a critical role in colon cancer progression, but the cellular and molecular mechanisms that contribute to metastasis remain unknown. KM12C colon cancer cell clones expressing high (C9) or negligible (C10) levels of TGFalpha were implanted into the cecal walls of nude mice. C9 tumors formed autocrine and paracrine EGFR networks, whereas C10 tumors were unable to signal through EGFR. The tumor microenvironment of C9, but not C10, contained cells enriched in vascular endothelial growth factor (VEGF) A, interleukin-8, and matrix metalloproteinases-2 and -9 and had a high vascular surface area. C9 tumors recruited a macrophage population that co-expressed F4/80 and lymphatic vessel endothelial hyaluronic acid receptor and produced VEGFC. The mean lymphatic density of C9 tumors was threefold higher than that of C10 tumors. C9, but not C10, tumor cells metastasized to regional lymph nodes in all mice and to the liver in 5 of 10 mice. Forced expression of TGFalpha in C10 tumor cells led to the generation of autocrine and paracrine EGFR signaling, macrophage recruitment, enhanced blood and lymphatic vascular surface areas, and increased lymphatic metastasis. Collectively, these data show that activation of TGFalpha-EGFR signaling in colon cancer cells creates a microenvironment that is conducive for metastasis, providing a rationale for efforts to inhibit EGFR signaling in TGFalpha-positive colon cancers.

Phosphorylated epidermal growth factor receptor on tumor-associated endothelial cells is a primary target for therapy with tyrosine kinase inhibitors

We determined whether phosphorylated epidermal growth factor receptor (EGFR) expressed on tumor-associated endothelial cells is a primary target for therapy with EGFR tyrosine kinase inhibitors (TKIs). Human colon cancer cells SW620CE2 (parental) that do not express EGFR or human epidermal growth factor receptor 2 (HER2) but express transforming growth factor alpha (TGF-alpha) were transduced with a lentivirus carrying nontargeting small hairpin RNA (shRNA) or TGF-alpha shRNA. The cell lines were implanted into the cecum of nude mice. Two weeks later, treatment began with saline, 4-[R]-phenethylamino-6-[hydroxyl] phenyl-7H-pyrrolo [2,3-D]-pyrimidine (PKI166), or irinotecan. Endothelial cells in parental and nontargeting shRNA tumors expressed phosphorylated EGFR. Therapy with PKI166 alone or with irinotecan produced apoptosis of these endothelial cells and necrosis of the EGFR-negative tumors. Endothelial cells in tumors that did not express TGF-alpha did not express EGFR, and these tumors were resistant to treatment with PKI166. The response of neoplasms to EGFR antagonists has been correlated with EGFR mutations, HER2 expression, Akt activation, and EGFR gene copy number. Our present data using colon cancer cells that do not express EGFR or HER2 suggest that the expression of TGF-alpha by tumor cells leading to the activation of EGFR in tumor-associated endothelial cells is a major determinant for the susceptibility of neoplasms to therapy by specific EGFR-TKI.

Targeting EGFR activity in blood vessels is sufficient to inhibit tumor growth and is accompanied by an increase in VEGFR-2 dependence in tumor endothelial cells

Epidermal growth factor receptor (EGFR) targeting agents such as kinase inhibitors reduce tumor growth and progression. We have previously reported that EGFR is not only expressed by the tumor cells but by the tumor endothelial cells (EC) as well (Amin, D. N., Hida, K., Bielenberg, D. R., Klagsbrun, M., 2006. Tumor endothelial cells express epidermal growth factor receptor (EGFR) but not ErbB3 and are responsive to EGF and to EGFR kinase inhibitors. Cancer Res. 66, 2173-80). Thus, targeting tumor blood vessel EGFR may be a viable strategy for tumor growth inhibition. We describe here a melanoma xenograft model where the tumor cells express very little or no EGFR but the tumor blood vessels express activated EGFR. The EGFR kinase inhibitor, gefitinib (Iressa), retarded tumor growth with a size decrease of 38% compared to control mice, ostensibly due to targeting of the blood vessels. EC were isolated from tumors of gefitinib-treated mice. These EC were unable to proliferate in response to EGF and displayed relatively weaker activation of MAPK and AKT signaling in response to EGF compared to tumor EC isolated from vehicle-treated mice. In contrast, the tumor EC from gefitinib-treated mice expressed higher levels of VEGFR-2 both at the mRNA and protein level. In addition, these cells were less sensitive to EGFR kinase inhibitors in vitro but more sensitive to a VEGFR-2 kinase inhibitor. These results suggest that in tumor EC from gefitinib-treated mice there is a switch from dependence on EGFR activity to signaling via VEGFR-2. Our data provide a molecular rationale for combination therapies targeting both EGF and VEGF signaling on the tumor vasculature.

Differential efficacy of combined therapy with radiation and AEE788 in high and low EGFR-expressing androgen-independent prostate tumor models

PURPOSE

To determine the efficacy of combining radiation (XRT) with a dual epidermal growth factor receptor (EGFR)/vascular endothelial growth factor receptor inhibitor, AEE788, in prostate cancer models with different levels of EGFR expression.

METHODS AND MATERIALS

Immunoblotting was performed for EGFR, phosphorylated-EGFR, and phosphorylated-AKT in prostate cancer cells. Clonogenic assays were performed on DU145, PC-3, and human umbilical vein endothelial cells treated with XRT +/- AEE788. Tumor xenografts were established for DU145 and PC-3 on hind limbs of athymic nude mice assigned to four treatment groups: (1) control, (2) AEE788, (3) XRT, and (4) AEE788 + XRT. Tumor blood flow and growth measurements were performed using immunohistochemistry and imaging.

RESULTS

AEE788 effectively decreased phosphorylated-EGFR and phosphorylated-AKT levels in DU145 and PC-3 cells. Clonogenic assays showed no radiosensitization for DU145 and PC-3 colonies treated with AEE788 + XRT. However, AEE788 caused decreased proliferation in DU145 cells. AEE788 showed a radiosensitization effect in human umbilical vein endothelial cells and increased apoptosis susceptibility. Concurrent AEE788 + XRT compared with either alone led to significant tumor growth delay in DU145 tumors. Conversely, PC-3 tumors derived no added benefit from combined-modality therapy. In DU145 tumors, a significant decrease in tumor blood flow with combination therapy was shown by using power Doppler sonography and tumor blood vessel destruction on immunohistochemistry. Maldi-spectrometry (MS) imaging showed that AEE788 is bioavailable and heterogeneously distributed in DU145 tumors undergoing therapy.

CONCLUSIONS

AEE788 + XRT showed efficacy in vitro/in vivo with DU145-based cell models, whereas PC-3-based models were adequately treated with XRT alone without added benefit from combination therapy. These findings correlated with differences in EGFR expression and showed effects on both tumor cell proliferation and vascular destruction.

Inhibition of epidermal growth factor receptor and vascular endothelial growth factor receptor phosphorylation on tumor-associated endothelial cells leads to treatment of orthotopic human colon cancer in nude mice

The purpose of our study was to determine whether the dual inhibition of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) signaling pathways in tumor-associated endothelial cells can inhibit the progressive growth of human colon carcinoma in the cecum of nude mice. SW620CE2 human colon cancer cells growing in culture and orthotopically in the cecum of nude mice expressed a high level of transforming growth factor alpha (TGF-alpha) and vascular endothelial growth factor (VEGF) but were negative for EGFR, human epidermal growth factor receptor 2 (HER2), and VEGFR. Double immunofluorescence staining revealed that tumor-associated endothelial cells expressed EGFR, VEGFR2, phosphorylated EGFR (pEGFR), and phosphorylated VEGFR (pVEGFR). Treatment of mice with either 7H-pyrrolo [2,3-d]-pyrimidine lead scaffold (AEE788; an inhibitor of EGFR and VEGFR tyrosine kinase) or CPT-11 as single agents significantly inhibited the growth of cecal tumors (P < .01); this decrease was even more pronounced with AEE788 combined with CPT-11 (P < .001). AEE788 alone or combined with CPT-11 also inhibited the expression of pEGFR and pVEGFR on tumor-associated endothelial cells, significantly decreased vascularization and tumor cell proliferation, and increased the level of apoptosis in both tumor-associated endothelial cells and tumor cells. These data demonstrate that targeting EGFR and VEGFR signaling on tumor-associated endothelial cells provides a viable approach for the treatment of colon cancer.

Intratumoral heterogeneity for expression of tyrosine kinase growth factor receptors in human colon cancer surgical specimens and orthotopic tumors

The design of targeted therapy, particularly patient-specific targeted therapy, requires knowledge of the presence and intratumoral distribution of tyrosine kinase receptors. To determine whether the expression of such receptors is constant or varies between and within individual colon cancer neoplasms, we examined the pattern of expression of the ligands, epidermal growth factor, vascular endothelial growth factor, and platelet-derived growth factor-B as well as their respective receptors in human colon cancer surgical specimens and orthotopic human colon cancers growing in the cecal wall of nude mice. The expression of the epidermal growth factor receptor and the vascular endothelial growth factor receptor on tumor cells and stromal cells, including tumor-associated endothelial cells, was heterogeneous in surgical specimens and orthotopic tumors. In some tumors, the receptor was expressed on both tumor cells and stromal cells, and in other tumors the receptor was expressed only on tumor cells or only on stromal cells. In contrast, the platelet-derived growth factor receptor was expressed only on stromal cells in both surgical specimens and orthotopic tumors. Examination of receptor expression in both individual surgical specimens and orthotopic tumors revealed that the platelet-derived growth factor receptor was expressed only on stromal cells and that the patterns of epidermal growth factor receptor and vascular endothelial growth factor receptor 2 expression differed between tumor cells. This heterogeneity in receptor expression among different tumor cells suggests that targeting a single tyrosine kinase may not yield eradication of the disease.

Expression of epidermal growth factor (EGF)/transforming growth factor-alpha by human lung cancer cells determines their response to EGF receptor tyrosine kinase inhibition in the lungs of mice

Epidermal growth factor receptor (EGFR) has been extensively targeted in the treatment of non-small cell lung cancer, producing responses in a small number of patients. To study the role of ligand expression in mediating response to EGFR antagonism, we injected NCI-H441 [EGFR and EGF/transforming growth factor-alpha (TGF-alpha) positive] or PC14-PE6 (EGFR positive and EGF/TGF-alpha negative) human lung adenocarcinoma cells into the lungs of nude mice. We randomized the mice to receive treatment with the EGFR tyrosine kinase inhibitors gefitinib or AEE788 or vehicle. Treatment of mice bearing NCI-H441 but not PC14-PE6 lung tumors resulted in a significant reduction in primary tumor growth, pleural effusion, and lymph node metastasis. Immunohistochemical analyses revealed that NCI-H441 and PC14-PE6 cells expressed EGFR but that the expression of EGF/TGF-alpha was high in NCI-H441 cells and very low in PC14-PE6 cells. Consequently, EGFR was activated in both tumor and tumor-associated endothelial cells in the NCI-H441 tumors but not in the PC14-PE6 tumors. Antagonism of EGFR signaling by treatment of mice with AEE788 decreased proliferation and increased apoptosis of both tumor cells and tumor-associated endothelial cells in NCI-H441 tumors but not in PC14-PE6 tumors. However, after transfection of PC14-PE6 cells with TGF-alpha, lung tumors derived from the transfected cells expressed and activated EGFR in both tumor and tumor-associated endothelial cells and tumors responded to treatment with AEE788. Collectively, these results strongly suggest that the response of human lung cancers growing orthotopically in mice to the inhibition of EGFR signaling is determined by ligand (EGF/TGF-alpha) expression by tumor cells. Our findings provide an additional explanation for the susceptibility of lung cancers to treatment with EGFR tyrosine kinase inhibitors.

Novel therapeutic approaches in the treatment of advanced pancreatic carcinoma

Pancreatic cancer is still a malignant disease of grim prognosis despite all therapeutic efforts. Because clinical symptoms in the early stage are usually absent or aspecific, it is frequently discovered at advanced or metastatic stage, only around 15-20% of tumors are resectable. In the majority of patients only the chemotherapy offers a prolongation of life, but even the first-line chemotherapeutic agent, the gemcitabine has a modest survival benefit, and objective tumor response is rarely achieved. Combination of various cytostatics did not produce a significant improvement either. For that reason, continuous search for other agents is mandatory. Nowadays, in the era of molecular-targeted oncotherapeutic approaches, pancreatic cancer is also a subject such trials: epidermal growth factor receptor blockade, inhibition of angiogenesis, modulation of tumor response through the extracellular matrix, inhibition of cyclooxygenase-2, farnesyl transferase inhibitors, signal transduction inhibitors, ablation of the hormonal influence and some other aspects have all been studies, but to date, no breakthrough in the treatment of pancreatic carcinoma is proven. In several Phase II-III studies these compounds given alone displayed marginal effects, but when combined with the standard cytostatics, some beneficial effects were observed, however, some of them displayed a severe (sometimes fatal) toxicity. To date, the role of the molecular targeted therapy in pancreatic carcinoma is promising, but the results are not convincingly superior to the standard chemotherapeutic treatments. Pancreatic adenocarcinoma remains a great challenge for the oncologists, and continuous search for better molecules and/or combinations is inevitable.

Oncogenic K-Ras signals through epidermal growth factor receptor and wild-type H-Ras to promote radiation survival in pancreatic and colorectal carcinoma cells

Pancreatic and colorectal carcinomas frequently express oncogenic/mutant K-Ras that contributes to both tumorigenesis and clinically observed resistance to radiation treatment. We have previously shown that farnesyltransferase inhibitors (FTI) radiosensitize many pancreatic and colorectal cancer cell lines that express oncogenic K-ras at doses that inhibit the prenylation and activation of H-Ras but not K-Ras. In the present study, we have examined the mechanism of FTI-mediated radiosensitization in cell lines that express oncogenic K-Ras and found that wild-type H-Ras is a contributor to radiation survival in tumor cells that express oncogenic K-Ras. In these experiments, inhibiting the expression of oncogenic K-Ras, wild-type H-Ras, or epidermal growth factor receptor (EGFR) led to similar levels of radiosensitization as treatment with the FTI tipifarnib. Treatment with the EGFR inhibitor gefitinib led to similar levels of radiosensitization, and the combinations of tipifarnib or gefitinib plus inhibition of K-Ras, H-Ras, or EGFR expression did not provide additional radiosensitization compared with tipifarnib or gefitinib alone. Finally, supplementing culture medium with the EGFR ligand transforming growth factor alpha was able to reverse the radiosensitizing effect of inhibiting K-ras expression. Taken together, these findings suggest that EGFR-activated H-Ras signaling is initiated by oncogenic K-Ras to promote radiation survival in pancreatic and colorectal cancers.

COX-2 expression in hepatocellular carcinoma is an initiation event; while EGF receptor expression with downstream pathway activation is a prognostic predictor of survival

INTRODUCTION

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is a leading cause of cancer mortality with over 90% of HCC patients succumbing to the disease. Current systemic therapies have had no measurable impact on survival in this disease; however there are small subsets of patients who benefit from systemic therapy who have been difficult to identify. Improvements in patient stratification and the development of biological therapies have resulted from the elucidation of the molecular mechanisms integral to tumor development and progression. Recent studies have found that COX-2 and EGFR are frequently inappropriately expressed in HCC compared to normal liver expression; however the presence of surface receptors does not always mean that the downstream pathway is active. In this study, we investigate the incidence and impact of activated EGFR downstream messengers phosphorylated akt (pakt) and/or phosphorylated MAPK (pMAPK) on survival in patients with HCC.

METHOD

Thirty consecutive HCC patients treated at a single institution were retrospectively reviewed. Patient data including age, sex, Child's score, histological type, grade, stage, and survival were analyzed. Immunohistochemical staining was performed on formalin fixed, paraffin embedded tissues using monoclonal antibodies to COX-2, EGF receptor, pMAPK, and pakt. Histoscores were determined for each marker and evaluated for impact in survival, stage, and tumor grade.

RESULTS

The median age was 67 years (39-83) and 67% of patients were male. Median survival was 9.8 months (1-47 months) for the whole group. COX-2 and EGFR expression was present in 90 and 67% of the tumors, respectively. Expression of activated downstream EGFR messengers was present in 53% of tumors (pMAPK 41%, pakt 31%). Median survival was significantly better in patients with downstream messenger expression, 24.4 months, compared to no expression, 4.7 months (P = 0.03). These groups were matched in age, stage, and Child's score.

CONCLUSION

COX-2 and EGFR expression are commonly seen in HCC. Activated downstream EGFR expression is also common in HCC and is a predictor of improved survival. There may be a therapeutic role for EGFR tyrosine kinase inhibitors in this subset of patients and further investigation is warranted.

Immunohistochemical measurement of endothelial cell apoptosis and proliferation in formalin-fixed, paraffin-embedded human cancer tissue

There is a need for simple, reproducible methodology for measurement of endothelial cell (EC) apoptosis and proliferation in formalin-fixed, paraffin-embedded (FFPE) human tissue obtained in clinical trials of potential anti-angiogenic agents. Therefore, we developed colorimetric, dual-label immunohistochemical techniques for use on FFPE tissue, based on the use of single-stranded (ss) DNA and Ki-67 as markers of EC apoptosis and proliferation, respectively. Digital image analysis was used to obtain the total tumour microvessel density (MVD), from which the EC apoptosis index (AI) and proliferation index (PI) were derived manually as the number of positive ECs per vessel. Immunohistochemical measurement of EC apoptosis and proliferation was validated on human colorectal cancer liver metastases from a randomized, placebo-controlled trial of the selective cyclooxygenase-2 inhibitor rofecoxib. Proliferating and apoptotic ECs clustered in discrete areas of the tumour vasculature. ECAI (median [inter-quartile range, IQR] 0.0018 [0.0003-0.0064]) and ECPI (median [IQR] 0.0043 [0.002-0.014]) values were low and highly variable in tumours from both placebo- and rofecoxib-treated patients. Our novel dual-label immunohistochemical methods will be generally applicable in FFPE human cancer tissue and should prove invaluable for measuring the anti-angiogenic activity of experimental therapies in clinical trials. The low absolute level of and variability in EC apoptosis and proliferation detectable in human colorectal cancer liver metastases indicates that similar intervention studies using these end-points will need to ensure adequate size in order to be able to detect anti-angiogenic activity by immunohistochemical methods.

Expression of betacellulin and epidermal growth factor receptor in hepatocellular carcinoma: implications for angiogenesis

Hepatocellular carcinoma (HCC) is becoming one of the common malignant tumors worldwide and is characterized by high vascularity. Angiogenesis (formation of new microvessels) is critical for growth and progression of various human solid tumors. Betacellulin (BTC) is a member of the epidermal growth factor (EGF) family, and its signal action is mediated through EGF receptors (EGFR). In this study, to understand the role of BTC in relation to EGFR in HCC, we examined localization, expression, and involvement in angiogenesis of BTC and EGFR. The results revealed that expression of BTC, EGFR, and tumor growth factor-alpha messenger RNA in HCC was increased by 80%, 60%, and 40%, respectively, as compared with those in the nontumorous tissues. Increased expression of BTC protein was observed in 31 (61%) of 51 HCC specimens, and the level of tumor growth factor-alpha protein was higher in 17 (33%) of 51 HCC specimens than in nonmalignant hepatocytes. Betacellulin was predominantly expressed in HCC cells, whereas EGFR was observed in sinusoidal endothelial cells of HCC in 25 tumors (49%). Betacellulin was secreted in all 4 examined HCC cell lines. The HCC specimens showing positive EGFR expression in tumor endothelial cells had a significantly higher microvessel density than those without EGFR expression (P < .005). A strong correlation was found between BTC expression in cancer cells and EGFR expression in tumor endothelial cells (P < .001). These findings suggest that overexpression of BTC by HCC cells and EGFR by tumor endothelial cells enhance vascularity in a paracrine manner.

Dual Epidermal Growth Factor Receptor and Vascular Endothelial Growth Factor Receptor Inhibition with NVP-AEE788 for the Treatment of Aggressive Follicular Thyroid Cancer

PURPOSE

Patients with radioiodine-resistant follicular thyroid cancer (FTC) have a poor prognosis, if metastasized, with currently available treatment modalities. Epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF) and their receptors (EGFR and VEGFR) have been reported to be overexpressed in FTC and have been implicated in FTC development. We hypothesized that inhibiting the phosphorylation of EGFR and VEGFR by treatment with NVP-AEE788 (AEE788), a novel dual specific EGFR and VEGFR inhibitor, either alone or in combination with paclitaxel, would inhibit the growth of FTC xenografts in an orthotopic nude mouse model.

EXPERIMENTAL DESIGN

To confirm previous reports, EGF and EGFR expression and vascularity were analyzed in human samples of FTC, Hürthle cell carcinoma, and normal thyroid tissues. EGFR expression in four FTC cell lines was measured using Western blotting. The antitumor effect of AEE788 on FTC cells in vitro was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and Western blotting. The effect of AEE788, alone and in combination with paclitaxel, on FTC tumor growth in an orthotopic nude mouse model was also investigated. Immunohistochemical analysis of EGFR and VEGFR signaling status, cell proliferation, apoptosis, and microvessel density was done.

RESULTS

EGF, EGFR, and vascularity were increased in human thyroid tumor samples and EGFR was increased in FTC cells. AEE788 inhibited FTC cell growth in vitro and reduced the phosphorylation status of EGFR, VEGFR, and two downstream targets, AKT and mitogen-activated protein kinase, in FTC cells. AEE788 alone and, to a greater extent, AEE788 plus paclitaxel suppressed FTC tumor growth in the thyroids of nude mice.

CONCLUSION

Dual inhibition of EGFR and VEGFR by AEE788 could represent a novel approach to the treatment of radioiodine-resistant FTC.