Cytokine Interaction With Cancer-Associated Fibroblasts in Esophageal Cancer.

Esophageal cancer (EC) is a highly aggressive cancer with poor outcomes under current treatment regimens. More recent findings suggest stroma elements, specifically cancer-associated fibroblasts (CAFs), play a role in disease occurrence and progression. Cancer-associated fibroblasts are largely the product of converted fibroblasts, but a variety of other local cell types including epithelial cells, endothelial cells, and mesenchymal cells have also been shown to transform to CAFs under the correct conditions. Cancer-associated fibroblasts primarily function in the communication between the tumor microenvironment and cancer cells via cytokine and chemokine secretions that accentuate immunosuppression and cancer growth. Cancer-associated fibroblasts also pose issues for EC treatment by contributing to resistance of current chemotherapeutics like cisplatin. Targeting this cell type directly proves difficult given the heterogeneity between CAFs subpopulations, but emerging research provides hope that treatment is on the horizon. This review aims to unravel some of the complexities surrounding CAFs' impact on EC growth and therapy.

Targeted dual inhibition of c-Met/VEGFR2 signalling by foretinib improves antitumour effects of nanoparticle paclitaxel in gastric cancer models.

Elevated expression of multiple growth factors and receptors including c-Met and VEGFR has been reported in gastric adenocarcinoma (GAC) and thus provides a potentially useful therapeutic target. The therapeutic efficacy of foretinib, a c-Met/VEGFR2 inhibitor, was determined in combination with nanoparticle paclitaxel (NPT) in GAC. Animal studies were conducted in NOD/SCID mice in subcutaneous and peritoneal dissemination xenografts. The mechanism of action was assessed by Immunohistochemical and Immunoblot analyses. In c-Met overexpressing MKN-45 cell-derived xenografts, NPT and foretinib demonstrated inhibition in tumour growth, while NPT plus foretinib showed additive effects. In c-Met low-expressing SNU-1 or patient-derived xenografts, the foretinib effect was smaller, while NPT had a similar effect compared with MKN-45, as NPT plus foretinib still exhibited an additive response. Median mice survival was markedly improved by NPT (83%), foretinib (100%) and NPT plus foretinib (230%) in peritoneal dissemination xenografts. Subcutaneous tumour analyses exhibited that foretinib increased cancer cell death and decreased cancer cell proliferation and tumour vasculature. NPT and foretinib suppressed the proliferation of GAC cells in vitro and had additive effects in combination. Further, foretinib caused a dramatic decrease in phosphorylated forms of c-Met, ERK, AKT and p38. Foretinib led to a decrease in Bcl-2, and an increase in p27, Bax, Bim, cleaved PARP-1 and cleaved caspase-3. Thus, these findings highlight the antitumour impact of simultaneous suppression of c-Met and VEGFR2 signalling in GAC and its potential to enhance nanoparticle paclitaxel response. This therapeutic approach might lead to a clinically beneficial combination to increase GAC patients' survival.

Therapeutic efficacy of anti-MMP9 antibody in combination with nab-paclitaxel-based chemotherapy in pre-clinical models of pancreatic cancer.

Matrix metalloproteinase 9 (MMP9) is involved in the proteolysis of extracellular proteins and plays a critical role in pancreatic ductal adenocarcinoma (PDAC) progression, invasion and metastasis. The therapeutic potential of an anti-MMP9 antibody (αMMP9) was evaluated in combination with nab-paclitaxel (NPT)-based standard cytotoxic therapy in pre-clinical models of PDAC. Tumour progression and survival studies were performed in NOD/SCID mice. The mechanistic evaluation involved RNA-Seq, Luminex, IHC and Immunoblot analyses of tumour samples. Median animal survival compared to controls was significantly increased after 2-week therapy with NPT (59%), Gem (29%) and NPT+Gem (76%). Addition of αMMP9 antibody exhibited further extension in survival: NPT+αMMP9 (76%), Gem+αMMP9 (47%) and NPT+Gem+αMMP9 (94%). Six-week maintenance therapy revealed that median animal survival was significantly increased after NPT+Gem (186%) and further improved by the addition of αMMP9 antibody (218%). Qualitative assessment of mice exhibited that αMMP9 therapy led to a reduction in jaundice, bloody ascites and metastatic burden. Anti-MMP9 antibody increased the levels of tumour-associated IL-28 (1.5-fold) and decreased stromal markers (collagen I, αSMA) and the EMT marker vimentin. Subcutaneous tumours revealed low but detectable levels of MMP9 in all therapy groups but no difference in MMP9 expression. Anti-MMP9 antibody monotherapy resulted in more gene expression changes in the mouse stroma compared to the human tumour compartment. These findings suggest that anti-MMP9 antibody can exert specific stroma-directed effects that could be exploited in combination with currently used cytotoxics to improve clinical PDAC therapy.

Endothelial Monocyte-Activating Polypeptide II Mediates Macrophage Migration in the Development of Hyperoxia-Induced Lung Disease of Prematurity.

Myeloid cells are key factors in the progression of bronchopulmonary dysplasia (BPD) pathogenesis. Endothelial monocyte-activating polypeptide II (EMAP II) mediates myeloid cell trafficking. The origin and physiological mechanism by which EMAP II affects pathogenesis in BPD is unknown. The objective was to determine the functional consequences of elevated EMAP II levels in the pathogenesis of murine BPD and to investigate EMAP II neutralization as a therapeutic strategy. Three neonatal mouse models were used: (1) BPD (hyperoxia), (2) EMAP II delivery, and (3) BPD with neutralizing EMAP II antibody treatments. Chemokinic function of EMAP II and its neutralization were assessed by migration in vitro and in vivo. We determined the location of EMAP II by immunohistochemistry, pulmonary proinflammatory and chemotactic gene expression by quantitative polymerase chain reaction and immunoblotting, lung outcome by pulmonary function testing and histological analysis, and right ventricular hypertrophy by Fulton's Index. In BPD, EMAP II initially is a bronchial club-cell-specific protein-derived factor that later is expressed in galectin-3+ macrophages as BPD progresses. Continuous elevated expression corroborates with baboon and human BPD. Prolonged elevation of EMAP II levels recruits galectin-3+ macrophages, which is followed by an inflammatory state that resembles a severe BPD phenotype characterized by decreased pulmonary compliance, arrested alveolar development, and signs of pulmonary hypertension. In vivo pharmacological EMAP II inhibition suppressed proinflammatory genes Tnfa, Il6, and Il1b and chemotactic genes Ccl2 and Ccl9 and reversed the severe BPD phenotype. EMAP II is sufficient to induce macrophage recruitment, worsens BPD progression, and represents a targetable mechanism of BPD development.

The N terminus of pro-endothelial monocyte-activating polypeptide II (EMAP II) regulates its binding with the C terminus, arginyl-tRNA synthetase, and neurofilament light protein.

Pro-endothelial monocyte-activating polypeptide II (EMAP II), one component of the multi-aminoacyl tRNA synthetase complex, plays multiple roles in physiological and pathological processes of protein translation, signal transduction, immunity, lung development, and tumor growth. Recent studies have determined that pro-EMAP II has an essential role in maintaining axon integrity in central and peripheral neural systems where deletion of the C terminus of pro-EMAP II has been reported in a consanguineous Israeli Bedouin kindred suffering from Pelizaeus-Merzbacher-like disease. We hypothesized that the N terminus of pro-EMAP II has an important role in the regulation of protein-protein interactions. Using a GFP reporter system, we defined a putative leucine zipper in the N terminus of human pro-EMAP II protein (amino acid residues 1-70) that can form specific strip-like punctate structures. Through GFP punctum analysis, we uncovered that the pro-EMAP II C terminus (amino acids 147-312) can repress GFP punctum formation. Pulldown assays confirmed that the binding between the pro-EMAP II N terminus and its C terminus is mediated by a putative leucine zipper. Furthermore, the pro-EMAP II 1-70 amino acid region was identified as the binding partner of arginyl-tRNA synthetase, a polypeptide of the multi-aminoacyl tRNA synthetase complex. We also determined that the punctate GFP pro-EMAP II 1-70 amino acid aggregate colocalizes and binds to the neurofilament light subunit protein that is associated with pathologic neurofilament network disorganization and degeneration of motor neurons. These findings indicate the structure and binding interaction of pro-EMAP II protein and suggest a role of this protein in pathological neurodegenerative diseases.

Comparative benefits of Nab-paclitaxel over gemcitabine or polysorbate-based docetaxel in experimental pancreatic cancer.

Gemcitabine has limited clinical benefits in pancreatic ductal adenocarcinoma. The solvent-based traditional taxanes docetaxel and paclitaxel have not shown clinical results superior to gemcitabine. Nab-paclitaxel, a water-soluble albumin-bound paclitaxel, may carry superior distribution properties into the tumor microenvironment and has shown efficacy in multiple tumor types. We evaluated nab-paclitaxel effects compared with gemcitabine or docetaxel. For pancreatic ductal adenocarcinoma cells AsPC-1, BxPC-3, MIA PaCa-2 and Panc-1, gemcitabine IC50 ranged from 494nM to 23.9 µM; docetaxel IC50 range was from 5 to 34nM; nab-paclitaxel IC50 range was from 243nM to 4.9 µM. Addition of IC25 dose of docetaxel or nab-paclitaxel decreased gemcitabine IC50. Net tumor growth inhibition after gemcitabine, docetaxel or nab-paclitaxel was 67, 31 and 72%, which corresponded with intratumoral proliferative and apoptotic indices. Tumor stromal density was decreased by nab-paclitaxel and to a lesser extent by docetaxel as measured through reduction in α-smooth muscle actin, S100A4 and collagen 1 expression. Animal survival was prolonged after nab-paclitaxel treatment (41 days, P < 0.002) compared with gemcitabine (32 days, P = 0.005), docetaxel (32 days, P = 0.005) and controls (20 days). Survival in nab-paclitaxel/gemcitabine and docetaxel/gemcitabine sequential treatment groups was not superior to nab-paclitaxel alone. Low-dose combination of gemcitabine with nab-paclitaxel or docetaxel was more effective compared with controls or gemcitabine alone but not superior to regular dose nab-paclitaxel alone. Combination treatment of gemcitabine+nab-paclitaxel or gemcitabine+docetaxel increased gemcitabine concentration in plasma and tumor. The superior antitumor activity of nab-paclitaxel provides a strong rationale for considering nab-paclitaxel as first-line monotherapy in pancreatic ductal adenocarcinoma.

Establishing a peritoneal dissemination xenograft mouse model for survival outcome assessment of experimental gastric cancer.

BACKGROUND: Peritoneal dissemination of gastric cancer is a common reason for unresectability, a frequent recurrence mechanism, and a common cause for death. The present study was performed to test peritoneal dissemination gastric cancer xenografts mouse models that would support survival outcome analyses. MATERIALS AND METHODS: Human gastric cancer cell lines AGS, NCI-N87, and SNU-16 were intraperitoneally injected into nude mice and severe combined immunodeficiency (SCID) mice. The peritoneal tumor formation and mouse survival were compared among different groups. Mice were treated with oxaliplatin (5 mg/kg) and NVP-BEZ235 (10 mg/kg). RESULTS: The formation rate of peritoneal cancer after intraperitoneal injection of 5 × 10(6) SNU16, NCI-N87, and AGS cells was 2/8, 6/8, and 0/8 in nude mice, and 6/6, 6/6, and 0/6 in SCID mice, respectively. Median animal survival with peritoneal dissemination was 74 d for NCI-N87 cells (10 × 10(6)), 95 d for SNU16 cells (10 × 10(6)), 78 d for SNU16 cells (20 × 10(6)), and 44 d for SNU16 cells (40 × 10(6)). In a therapeutic experiment with 40 × 10(6) SNU16 cells, animal survival was significantly improved by oxaliplatin treatment compared with the control group (58.5 d versus 45 d, P < 0.001), but not by NVP-BEZ235 (48 d versus 45 d, P = 0.249) treatment. In the accompanying subcutaneous SNU16 mouse model, relative tumor volume compared with controls was not significantly decreased by oxaliplatin treatment (P = 0.151) but by NVP-BEZ235 therapy (P = 0.008). CONCLUSIONS: Peritoneal gastric cancer xenografts were successfully established after intraperitoneal injection NCI-N87 and SNU16 cells. These findings provide a useful survival outcome assessment model for experimental gastric cancer research.

Nab-Paclitaxel in the Treatment of Gastrointestinal Cancers-Improvements in Clinical Efficacy and Safety.

Taxanes (paclitaxel and docetaxel) are one of the most useful classes of anticancer drugs. Taxanes are highly hydrophobic; therefore, these drugs must be dissolved in organic solvents (polysorbate or Cremophor EL), which contribute to their toxicities. To reduce this toxicity and to enhance their efficacy, novel formulations have been developed. Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is an albumin-stabilized, Cremophor-free, and water-soluble nanoparticle formulation of paclitaxel. Nab-paclitaxel has better solubility and less infusion-associated toxicity compared to solvent-based paclitaxel. Additionally, nab-paclitaxel can be given at higher doses and concentrations compared with solvent-based paclitaxel. Based on its superior clinical efficacy and safety profile, nab-paclitaxel received FDA approval for metastatic breast cancer (2008) and NSCLC (2011). Among gastrointestinal cancers, it is now approved in the USA for treating patients with metastatic adenocarcinoma of the pancreas as first-line therapy in combination with gemcitabine. Furthermore, several clinical trials have suggested the potential efficacy of nab-paclitaxel as a single agent or in combination with other agents for the treatment of metastatic esophageal, gastric, bowel, and biliary tract cancers. Nab-paclitaxel has been demonstrated to have greater overall response rates (ORR) with enhanced progression-free survival (PFS), overall survival (OS) and a superior safety profile with fewer adverse effects in patients with gastrointestinal tract cancers. This review summarizes the advantages associated with nab-paclitaxel-based regimens in terms of improving clinical efficacy and the safety profile in upper gastrointestinal cancer.

Targeting KRAS for the potential treatment of pancreatic ductal adenocarcinoma: Recent advancements provide hope (Review).

Kirsten rat sarcoma viral oncogene homolog (KRAS) is one of the most frequently mutated oncogenes in solid tumors. More than 90% of pancreatic ductal adenocarcinoma (PDAC) are driven by mutations in the KRAS gene, suggesting the importance of targeting this oncogene in PDAC. Initial efforts to target KRAS have been unsuccessful due to its small size, high affinity for guanosine triphosphate/guanosine diphosphate, and lack of distinct drug­binding pockets. Therefore, much of the focus has been directed at inhibiting the activation of major signaling pathways downstream of KRAS, most notably the PI3K/AKT and RAF/MAPK pathways, using tyrosine kinase inhibitors and monoclonal antibodies. While preclinical studies showed promising results, clinical data using the inhibitors alone and in combination with other standard therapies have shown limited practicality, largely due to the lack of efficacy and dose­limiting toxicities. Recent therapeutic approaches for KRAS­driven tumors focus on mutation­specific drugs such as selective KRASG12C inhibitors and son of sevenless 1 pan­KRAS inhibitors. While KRASG12C inhibitors showed great promise against patients with non­small cell lung cancer (NSCLC) harboring KRASG12C mutations, they were not efficacious in PDAC largely because the major KRAS mutant isoforms in PDAC are G12D, G12V, and G12R. As a result, KRASG12D and pan­KRAS inhibitors are currently under investigation as potential therapeutic options for PDAC. The present review summarized the importance of KRAS oncogenic signaling, challenges in its targeting, and preclinical and clinical targeted agents including recent direct KRAS inhibitors for blocking KRAS signaling in PDAC.

Enhancing gastric cancer conventional chemotherapy effects by triple angiokinase inhibitor nintedanib in preclinical models.

Background: Gastric adenocarcinoma (GAC) is the fourth leading cause of cancer death worldwide. Systemic chemotherapy is a preferred treatment option for advanced and recurrent GAC, but response rates and survival prolongation remain limited. Tumor angiogenesis plays a critical role in GAC growth, invasion and metastasis. We investigated the antitumor efficacy of nintedanib, a potent triple angiokinase inhibitor for VEGFR-1/2/3, PDGFR-α/ß and FGFR-1/2/3, alone or in combination with chemotherapy, in preclinical models of GAC. Methods: Animal survival studies were performed in peritoneal dissemination xenografts in NOD/SCID mice using human GAC cell lines MKN-45 and KATO-III. Tumor growth inhibition studies were performed in subcutaneous xenografts in NOD/SCID mice using human GAC cell lines MKN-45 and SNU-5. The mechanistic evaluation involved Immunohistochemistry analyses in tumor tissues obtained from subcutaneous xenografts. In vitro cell viability assays were performed using a colorimetric WST-1 reagent. Results: In MKN-45 GAC cell-derived peritoneal dissemination xenografts, animal survival was improved by nintedanib (33%), docetaxel (100%) and irinotecan (181%), while oxaliplatin, 5-FU and epirubicin had no effect. The addition of nintedanib to docetaxel (157%) or irinotecan (214%) led to a further extension in animal survival. In KATO-III GAC cell-derived xenografts carrying FGFR2 gene amplification, nintedanib extended survival by 209%. Again, the addition of nintedanib further enhanced the animal survival benefits of docetaxel (273%) and irinotecan (332%). In MKN-45 subcutaneous xenografts, nintedanib, epirubicin, docetaxel and irinotecan reduced tumor growth (range: 68-87%), while 5-FU and oxaliplatin had a smaller effect (40%). Nintedanib addition to all chemotherapeutics demonstrated a further reduction in tumor growth. Subcutaneous tumor analysis revealed that nintedanib attenuated tumor cell proliferation, reduced tumor vasculature and increased tumor cell death. Conclusion: Nintedanib showed notable antitumor efficacy and significantly improved taxane or irinotecan chemotherapy responses. These findings indicate that nintedanib, alone and in combination with a taxane or irinotecan, has the potential for improving clinical GAC therapy.

The efficacy of a novel, dual PI3K/mTOR inhibitor NVP-BEZ235 to enhance chemotherapy and antiangiogenic response in pancreatic cancer.

Gemcitabine has limited clinical benefits for pancreatic ductal adenocarcinoma (PDAC). The phosphatidylinositol-3-kinase (PI3K)/AKT and mammalian target of rapamycin (mTOR) signaling pathways are frequently dysregulated in PDAC. We investigated the effects of NVP-BEZ235, a novel dual PI3K/mTOR inhibitor, in combination with gemcitabine and endothelial monocyte activating polypeptide II (EMAP) in experimental PDAC. Cell proliferation and protein expression were analyzed by WST-1 assay and Western blotting. Animal survival experiments were performed in murine xenografts. BEZ235 caused a decrease in phospho-AKT and phospho-mTOR expression in PDAC (AsPC-1), endothelial (HUVECs), and fibroblast (WI-38) cells. BEZ235 inhibited in vitro proliferation of all four PDAC cell lines tested. Additive effects on proliferation inhibition were observed in the BEZ235-gemcitabine combination in PDAC cells and in combination of BEZ235 or EMAP with gemcitabine in HUVECs and WI-38 cells. BEZ235, alone or in combination with gemcitabine and EMAP, induced apoptosis in AsPC-1, HUVECs, and WI-38 cells as observed by increased expression of cleaved poly (ADP-ribose) polymerase-1 (PARP-1) and caspase-3 proteins. Compared to controls (median survival: 16 days), animal survival increased after BEZ235 and EMAP therapy alone (both 21 days) and gemcitabine monotherapy (28 days). Further increases in survival occurred in combination therapy groups BEZ235 + gemcitabine (30 days, P = 0.007), BEZ235 + EMAP (27 days, P = 0.02), gemcitabine + EMAP (31 days, P = 0.001), and BEZ235 + gemcitabine + EMAP (33 days, P = 0.004). BEZ235 has experimental PDAC antitumor activity in vitro and in vivo that is further enhanced by combination of gemcitabine and EMAP. These findings demonstrate advantages of combination therapy strategies targeting multiple pathways in pancreatic cancer treatment.

Augmenting Experimental Gastric Cancer Activity of Irinotecan through Liposomal Formulation and Antiangiogenic Combination Therapy.

Gastric adenocarcinoma (GAC) is the third most common cause of cancer-related deaths worldwide. Combination chemotherapy remains the standard treatment for advanced GAC. Liposomal irinotecan (nal-IRI) has improved pharmacokinetics (PK) and drug biodistribution compared with irinotecan (IRI, CPT-11). Angiogenesis plays a crucial role in the progression and metastasis of GAC. We evaluated the antitumor efficacy of nal-IRI in combination with novel antiangiogenic agents in GAC mouse models. Animal survival studies were performed in peritoneal dissemination xenografts. Tumor growth and PK studies were performed in subcutaneous xenografts. Compared with controls, extension in animal survival by nal-IRI and IRI was >156% and >94%, respectively. The addition of nintedanib or DC101 extended nal-IRI response by 13% and 15%, and IRI response by 37% and 31% (MKN-45 xenografts); nal-IRI response by 11% and 3%, and IRI response by 16% and 40% (KATO-III xenografts). Retardation of tumor growth was greater with nal-IRI (92%) than IRI (71%). Nintedanib and DC101 addition tend to augment nal-IRI or IRI response in this model. The addition of antiangiogenic agents enhanced tumor cell proliferation inhibition effects of nal-IRI or IRI. The tumor vasculature was decreased by nintedanib (65%) and DC101 (58%), while nal-IRI and IRI alone showed no effect. PK characterization in GAC xenografts demonstrated that compared with IRI, nal-IRI treatment groups had higher retention, circulation time, and tumor levels of CPT-11 and its active metabolite SN-38. These findings indicate that nal-IRI, alone and in combination with antiangiogenic agents, has the potential for improving clinical GAC therapy.

Smac mimetic-derived augmentation of chemotherapeutic response in experimental pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to conventional chemotherapy, in part due to the overexpression of inhibitors of apoptosis proteins (IAPs). Smac is an endogenous IAP-antagonist, which renders synthetic Smac mimetics attractive anticancer agents. We evaluated the benefits of combining a Smac mimetic, JP1201 (JP), with conventional chemotherapy agents used for PDAC management. METHODS: Cell viability assays and protein expression analysis were performed using WST-1 reagent and Western blotting, respectively. Apoptosis was detected by annexin V/propidium iodide staining. In vivo tumor growth and survival studies were performed in murine PDAC xenografts. RESULTS: JP and gemcitabine (Gem) inhibited PDAC cell proliferation with additive effects in combination. The percentage of early apoptotic cells in controls, JP, Gem and JP + Gem was 17%, 26%, 26% and 38%, respectively. JP-induced apoptosis was accompanied by PARP-1 cleavage. Similar additive anti-proliferative effects were seen for combinations of JP with doxorubicin (Dox) and docetaxel (DT). The JP + Gem combination caused a 30% decrease in tumor size in vivo compared to controls. Median animal survival was improved significantly in mice treated with JP + Gem (38 d) compared to controls (22 d), JP (28 d) or Gem (32 d) (p = 0.01). Animal survival was also improved with JP + DT treatment (32 d) compared to controls (16 d), JP (21 d) or DT alone (27 d). CONCLUSIONS: These results warrant further exploration of strategies that promote chemotherapy-induced apoptosis of tumors and highlight the potential of Smac mimetics in clinical PDAC therapy.

Antitumour activity of sunitinib in combination with gemcitabine in experimental pancreatic cancer.

BACKGROUND: Gemcitabine (Gem) has limited clinical benefits in pancreatic ductal adenocarcinoma (PDAC). Sunitinib (Su) is a novel, multi-target receptor tyrosine kinase inhibitor that has antitumour activities. This study tested the benefits of combined gemcitabine and sunitinib in PDAC. METHODS: Cell viability and protein expression were evaluated by WST-1 assay and Western blotting. Tumour growth and survival experiments were performed in murine xenografts. RESULTS: In PDAC cells, Gem, Su and Su + Gem, respectively, caused 28%, 22% and 48% inhibition in proliferation at 100 nM. In endothelial cells, Gem, Su and Su + Gem, respectively, caused 49%, 32% and 72% inhibition in proliferation. In fibroblasts, Gem, Su and Su + Gem, respectively, caused 65%, 14% and 79% inhibition in proliferation. Su increased apoptosis, as evidenced by the cleavage of caspase-3 and PARP-1 proteins. Net tumour growth compared with controls in the Gem, Su and Su + Gem groups was 57%, 6% and 1%, respectively. Intratumoral proliferative activity was reduced by 33%, 82% and 75% in the Gem, Su and Su + Gem groups, respectively, compared with controls. Median survival in the control, Su, Gem and Su + Gem groups was 16, 21, 24 and 30 days, respectively (P=0.007). CONCLUSIONS: These findings support a combination approach using multi-target antiangiogenic agents such as sunitinib with standard gemcitabine therapy in the treatment of PDAC.

Therapeutic Potential of the Cyclin-Dependent Kinase Inhibitor Flavopiridol on c-Myc Overexpressing Esophageal Cancer.

Tumors with elevated c-Myc expression often exhibit a highly aggressive phenotype, and c-Myc amplification has been shown to be frequent in esophageal cancer. Emerging data suggests that synthetic lethal interactions between c-Myc pathway activation and small molecules inhibition involved in cell cycle signaling can be therapeutically exploited to preferentially kill tumor cells. We therefore investigated whether exploiting elevated c-Myc expression is effective in treating esophageal cancer with the CDK inhibitor flavopiridol. We found frequent overexpression of c-Myc in human esophageal cancer cell lines and tissues. c-Myc overexpression correlated with accelerated esophageal cancer subcutaneous xenograft tumor growth. Esophageal cancer cells with elevated c-Myc expression were found preferentially more sensitive to induction of apoptosis by the CDK inhibition flavopiridol compared to esophageal cancer cells with lower c-Myc expression. In addition, we observed that flavopiridol alone or in combination with the chemotherapeutic agent nanoparticle albumin-bound paclitaxel (NPT) or in combinations with the targeted agent BMS-754807 significantly inhibited esophageal cancer cell proliferation and subcutaneous xenograft tumor growth while significantly enhancing overall mice survival. These results indicate that aggressive esophageal cancer cells with elevated c-Myc expression are sensitive to the CDK inhibitor flavopiridol, and that flavopiridol alone or in combination can be a potential therapy for c-Myc overexpressing esophageal cancer.

Targeted FGFR/VEGFR/PDGFR inhibition with dovitinib enhances the effects of nab-paclitaxel in preclinical gastric cancer models.

Standard chemotherapy regimens for gastric adenocarcinoma (GAC) have limited efficacy and considerable toxicity profiles. Nab-paclitaxel has shown promising antitumor benefits in previous GAC preclinical studies. Dovitinib inhibits members of the receptor tyrosine kinase family including FGFR, VEGFR and PDGFR, and has exhibited antitumor effects in many solid tumors including GAC. Based on the antimitotic, antistromal and EPR effects of nab-paclitaxel, we investigated augmentation of nab-paclitaxel response by dovitinib in multiple GAC preclinical models. In MKN-45 subcutaneous xenografts, inhibition in tumor growth by nab-paclitaxel and dovitinib was 75% and 76%, respectively. Dovitinib plus nab-paclitaxel had an additive effect on tumor growth inhibition and resulted in tumor regression (85% of its original value). Dovitinib monotherapy resulted in minimal improvement in animal survival (25 days) compared to control (23 days), while nab-paclitaxel monotherapy or dovitinib plus nab-paclitaxel combination therapy led to a clinically significant lifespan extension of 83% (42 days) and 187% (66 days), respectively. IHC analysis of subcutaneous tumors exhibited reduced tumor cell proliferation and tumor vasculature by dovitinib. In vitro studies demonstrated that dovitinib and nab-paclitaxel individually reduced tumor cell proliferation, with an additive effect from combination therapy. Immunoblot analyses of MKN-45 and KATO-III cells revealed that dovitinib decreased phospho-FGFR, phospho-AKT, phospho-ERK, phospho-p70S6K, phospho-4EBP1, Bcl-2 and increased cleaved PARP-1, cleaved-caspase-3, p27, Bax, Bim, with an additive effect from combination therapy. These results demonstrate that the FGFR/VEGFR/PDGFR inhibitor, dovitinib, has the potential to augment the antitumor effects of nab-paclitaxel, with implications for use in the advancement of clinical GAC therapy.

EMAP II-based antiangiogenic-antiendothelial in vivo combination therapy of pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) frequently resists conventional cytotoxic therapy. The antitumor effects of endothelial monocyte-activating polypeptide II (EMAP) have been attributed to its antiendothelial and antiangiogenic activities. We tested the hypothesis that a combination of EMAP with bevacizumab (Bev) and gemcitabine (Gem) targets different pathways of PDAC progression and represents more effective treatment. METHODS: Proliferation of PDAC and endothelial cell lines was evaluated in vitro. In vivo tumor growth and survival PDAC xenograft experiments were performed with EMAP, Bev, and Gem, either alone or in combination. Intratumoral microvessel density and proliferative activity were analyzed by immunostaining with PECAM-1 and proliferating cell nuclear antigen antibodies, and apoptotic activity was measured by the TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) procedure. RESULTS: Compared with controls, net reduction in tumor growth in EMAP, Bev, Gem, EMAP + Bev, EMAP + Gem, Bev + Gem, and EMAP + Bev + Gem groups was 58, 40, 40, 67, 68, 69, and 96%, respectively. Addition of EMAP to the Bev + Gem group statistically significantly improved survival at a median of >8 days while inducing long-term survival in some animals after maintenance therapy. Combination treatment of EMAP with Bev and Gem reduced proliferation of endothelial but not of PDAC cells. Addition of EMAP to Bev and Gem statistically significantly decreased proliferative activity while maintaining a comparable rate of microvessel density and apoptosis. CONCLUSIONS: Addition of antiendothelial EMAP to a Bev and Gem regimen improves antitumor effects in a xenograft model of PDAC. This multitargeting strategy to prevent PDAC progression shows therapeutic promise and may overcome limitations by combinations of Gem with anti-vascular endothelial growth factor agents alone.

Endothelial monocyte activating polypeptide II interferes with VEGF-induced proangiogenic signaling.

Endothelial monocyte activating polypeptide II (EMAP II) is a proinflammatory cytokine with antiangiogenic properties. EMAP II functions as a potent inhibitor of primary and metastatic tumor growth, has strong inhibitory effects on endothelial cells (ECs), and can reduce intratumoral expression of the angiogenesis inducer vascular endothelial growth factor (VEGF). VEGF influences EC functions such as proliferation, migration, survival and tube formation. Therapeutic strategies that target VEGF have been demonstrated to reduce the tumor growth. We investigated the effects of EMAP II on VEGF-induced angiogenesis signaling. Primary human fetal lung ECs (HFLECs) and human umbilical vein ECs (HUVECs) were grown in E-Stim medium. Protein binding was analyzed using enzyme-linked immunosorbent assay (ELISA). Protein expression was determined by western blot analysis. EC proliferation and migration was determined using WST-1 reagent and transwell membrane, respectively. EMAP II efficiently and dose dependently binds to VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) as observed by ELISA. B(max) values for VEGFR1 and VEGFR2 were 0.45 and 0.17, respectively. In addition, EMAP II inhibited binding of VEGF to VEGFR1 and VEGFR2. EMAP II significantly reduced VEGF-induced expression of phosphorylated VEGFR1 (in HFLEC and HUVEC) by >50%, and of phosphorylated VEGFR2 (in HUVEC) by 66%. EMAP II also inhibited downstream VEGF signaling. Although VEGF-induced phosphorylation of Akt, Erk1/2, p38 and Raf 2.8-, 1.5-, 2.2- and 3.6-fold, respectively, EMAP II preincubation blocked this induction in phosphorylation to control levels. VEGF-induced EC proliferation 2.5-fold, and EMAP II pretreatment abrogated this effect. Similarly, VEGF-induced EC migration (2.5-fold) was significantly inhibited by EMAP II. These finding suggest that inhibition of VEGF signaling is one possible antiangiogenic mechanism of EMAP II, which may explain its in vivo antitumor activity and delineate therapeutic strategies to enhance anti-VEGF therapy to inhibit tumor growth.

Proteasome inhibition enhances antitumour effects of gemcitabine in experimental pancreatic cancer.

BACKGROUND: The clinical benefit of gemcitabine, the standard systemic therapy of pancreatic cancer (PaCa), remains modest as a result of high chemoresistance. The proteasome inhibitor bortezomib has antitumour activity against PaCa in vitro and in vivo. We examined the antitumour activity of combination PaCa therapy with bortezomib and gemcitabine. METHODS: Cell proliferation assays were performed using WST-1 reagent. Protein expression was determined by Western blotting. Efficacy of bortezomib and/or gemcitabine was tested in vivo in a survival study. RESULTS: Bortezomib at 10 microM caused 29% and 72% inhibition in AsPC-1 PaCa cell proliferation at 48 and 96 h incubation, respectively. Bortezomib was even more active against PaCa cell lines Panc-1 and MiaPaCa, with 80% inhibition of proliferation at 48 h. The combination of bortezomib and gemcitabine inhibited AsPC-1 proliferation more effectively compared with each single agent alone. Poly(ADP-ribose) polymerase (PARP) cleavage, an apoptotic indicator, reached 6.6-, 2- and 8.5-fold over controls for bortezomib, gemcitabine and the combination. The median survival was 31 (controls and bortezomib), 40 (gemcitabine) and 48 days (combination), respectively (P < 0.002). CONCLUSIONS: Bortezomib and gemcitabine demonstrate additive antitumour activity in vitro and in an experimental PaCa model, indicating the potential for clinical PaCa benefits of additional multiagent therapies that will be based upon the bortezomib and gemcitabine combination.

Combination effect of lapatinib with foretinib in HER2 and MET co-activated experimental esophageal adenocarcinoma.

Recent studies have demonstrated that HER2 and MET receptor tyrosine kinases are co-overexpressed in a subset esophageal adenocarcinoma (EAC). We therefore studied the usefulness of combining HER2 and MET targeting by small-molecule inhibitors lapatinib and foretinib, respectively, both in in-vitro and in-vivo models of experimental EAC. We characterized MET and HER2 activation in a panel of human EAC cell lines, and the differential susceptibility of these EAC cell lines to single agent or combination of foretinib and lapatinib. We then explored the antitumor efficacy with survival advantage following foretinib and lapatinib monotherapy and in combination in murine subcutaneous xenograft and peritoneal metastatic survival models of human EAC. The OE33 EAC cell line with strong expression of phosphorylated both MET and HER2, demonstrated reduced sensitivity to foretinib and lapatinib when used as a single agent. The co-administration of foretinib and lapatinib effectively inhibited both MET and HER2 phosphorylation, enhanced inhibition of cell proliferation and xenograft tumor growth by inducing apoptosis, and significantly enhanced mouse overall survival, overcoming single agent resistance. In the OE19 EAC cell line with mainly HER2 phosphorylation, and the ESO51 EAC cell line with mainly MET phosphorylation, profound cell growth inhibition with induction of apoptosis was observed in response to single agent with lack of enhanced growth inhibition when the two agents were combined. These data suggest that combination therapy with foretinib and lapatinib should be tested as a treatment option for HER2 positive patients with MET-overexpressing EAC, and could be a novel treatment strategy for specific EAC patients.