Roberta Rosa

Vascular Endothelial Growth Factor Receptor-1 Contributes to Resistance to Anti–Epidermal Growth Factor Receptor Drugs in Human Cancer Cells

Purpose: The resistance to selective EGFR inhibitors involves the activation of alternative signaling pathways, and Akt activation and VEGF induction have been described in EGFR inhibitor–resistant tumors. Combined inhibition of EGFR and other signaling proteins has become a successful therapeutic approach, stimulating the search for further determinants of resistance as basis for novel therapeutic strategies. Experimental Design: We established human cancer cell lines with various degrees of EGFR expression and sensitivity to EGFR inhibitors and analyzed signal transducers under the control of EGFR-dependent and EGFR-independent pathways. Results: Multitargeted inhibitor vandetanib (ZD6474) inhibited the growth and the phosphorylation of Akt and its effector p70S6 kinase in both wild-type and EGFR inhibitor–resistant human colon, prostate, and breast cancer cells. We found that the resistant cell lines exhibit, as common feature, VEGFR-1/Flt-1 overexpression, increased secretion of VEGF and placental growth factor, and augmented migration capabilities and that vandetanib is able to antagonize them. Accordingly, a new kinase assay revealed that in addition to VEGF receptor (VEGFR)-2, RET, and EGFR, vandetanib efficiently inhibits also VEGFR-1. The contribution of VEGFR-1 to the resistant phenotype was further supported by the demonstration that VEGFR-1 silencing in resistant cells restored sensitivity to anti-EGFR drugs and impaired migration capabilities, whereas exogenous VEGFR-1 overexpression in wild-type cells conferred resistance to these agents. Conclusions: This study shows that VEGFR-1 contributes to anti-EGFR drug resistance in different human cancer cells. Moreover, vandetanib inhibits VEGFR-1 activation, cell proliferation, and migration, suggesting its potential utility in patients resistant to EGFR inhibitors.

Inhibition of mTOR pathway by everolimus cooperates with EGFR inhibitors in human tumours sensitive and resistant to anti-EGFR drugs

Inhibition of a single transduction pathway is often inefficient due to activation of alternative signalling. The mammalian target of rapamycin (mTOR) is a key intracellular kinase integrating proliferation, survival and angiogenic pathways and has been implicated in the resistance to EGFR inhibitors. Thus, mTOR blockade is pursued to interfere at multiple levels with tumour growth. We used everolimus (RAD001) to inhibit mTOR, alone or in combination with anti-EGFR drugs gefitinib or cetuximab, on human cancer cell lines sensitive and resistant to EGFR inhibitors, both in vitro and in vivo. We demonstrated that everolimus is active against EGFR-resistant cancer cell lines and partially restores the ability of EGFR inhibitors to inhibit growth and survival. Everolimus reduces the expression of EGFR-related signalling effectors and VEGF production, inhibiting proliferation and capillary tube formation of endothelial cells, both alone and in combination with gefitinib. Finally, combination of everolimus and gefitinib inhibits growth of GEO and GEO-GR (gefitinib resistant) colon cancer xenografts, activation of signalling proteins and VEGF secretion. Targeting mTOR pathway with everolimus overcomes resistance to EGFR inhibitors and produces a cooperative effect with EGFR inhibitors, providing a valid therapeutic strategy to be tested in a clinical setting.

Hypoxia-increased RAGE and P2X7R expression regulates tumor cell invasion through phosphorylation of Erk1/2 and Akt and nuclear translocation of NF-κB

The role of hypoxia in regulating tumor progression is still controversial. Here, we demonstrate that, similarly to what previously observed by us in human prostate and breast tumor samples, hypoxia increases expression of the receptor for advanced glycation end products (RAGE) and the purinergic receptor P2X7 (P2X7R). The role of hypoxia was shown by the fact that hypoxia-inducible factor (HIF)-1α silencing downregulated RAGE and P2X7R protein levels as well as nuclear factor-kappaB (NF-κB) expression. In contrast, NF-κB silencing reduced P2X7R expression without affecting RAGE protein levels or nuclear accumulation of HIF-1α. Treatment of hypoxic tumor cells with HMGB1 and BzATP ligands, respectively, of RAGE and P2X7R, activated a signaling pathway that, through Akt and Erk phosphorylation, determines nuclear accumulation of NF-κB and increases cell invasion. Inhibition of Akt by SH5 and Erk by INH1 prevented both nuclear translocation of NF-κB and cell invasion. Moreover, silencing RAGE and P2X7R abolished nuclear accumulation of NF-κB as well as cell invasion without affecting HIF-1α stabilization. Once in the nucleus, NF-κB would contribute to cell survival and invasion under hypoxia, by maintaining RAGE and P2X7R expression levels and matrix metalloproteinases 2 and 9 synthesis. These results show that, hypoxia can upregulate expression levels of membrane receptors that, by binding extracellular molecules eventually released by necrotic cells, contribute to the increased invasiveness of transformed tumor cells. Moreover, these observations strengthen our working hypothesis that upregulation of damage-associated molecular patterns receptors by HIF-1α represents the crucial event bridging hypoxia and inflammation in obtaining the malignant phenotype.

Sphingosine Kinase 1 Overexpression Contributes to Cetuximab Resistance in Human Colorectal Cancer Models

Purpose: Although the anti–EGF receptor (EGFR) monoclonal antibody cetuximab is an effective strategy in colorectal cancer therapy, its clinical use is limited by intrinsic or acquired resistance. Alterations in the “sphingolipid rheostat”—the balance between the proapoptotic molecule ceramide and the mitogenic factor sphingosine-1-phosphate (S1P)—due to sphingosine kinase 1 (SphK1) overactivation have been involved in resistance to anticancer-targeted agents. Moreover, cross-talks between SphK1 and EGFR-dependent signaling pathways have been described. Experimental design: We investigated SphK1 contribution to cetuximab resistance in colorectal cancer, in preclinical in vitro/in vivo models, and in tumor specimens from patients. Results: SphK1 was found overexpressed and overactivated in colorectal cancer cells with intrinsic or acquired resistance to cetuximab. SphK1 contribution to resistance was supported by the demonstration that SphK1 inhibition by N,N-dimethyl-sphingosine or silencing via siRNA in resistant cells restores sensitivity to cetuximab, whereas exogenous SphK1 overexpression in sensitive cells confers resistance to these agents. Moreover, treatment of resistant cells with fingolimod (FTY720), a S1P receptor (S1PR) antagonist, resulted in resensitization to cetuximab both in vitro and in vivo, with inhibition of tumor growth, interference with signal transduction, induction of cancer cells apoptosis, and prolongation of mice survival. Finally, a correlation between SphK1 expression and cetuximab response was found in colorectal cancer patients. Clin Cancer Res; 19(1); 138–47. ©2012 AACR.

TLR9 agonist acts by different mechanisms synergizing with bevacizumab in sensitive and cetuximab-resistant colon cancer xenografts

Synthetic agonists of Toll-like receptor 9 (TLR9), a class of agents that induce specific immune response, exhibit antitumor activity and are currently being investigated in cancer patients. Intriguingly, their mechanisms of action on tumor growth and angiogenesis are still incompletely understood. We recently discovered that a synthetic agonist of TLR9, immune modulatory oligonucleotide (IMO), acts by impairing epidermal growth factor receptor (EGFR) signaling and potently synergizes with anti-EGFR antibody cetuximab in GEO human colon cancer xenografts, whereas it is ineffective in VEGF-overexpressing cetuximab-resistant GEO cetuximab-resistant (GEO-CR) tumors. VEGF is activated by EGFR, and its overexpression causes resistance to EGFR inhibitors. Therefore, we used IMO and the anti-VEGF antibody bevacizumab as tools to study IMOs role on EGFR and angiogenesis and to explore its therapeutic potential in GEO, LS174T, and GEO-CR cancer xenografts. We found that IMO enhances the antibody-dependent cell-mediated cytotoxicity (ADCC) activity of cetuximab, that bevacizumab has no ADCC, and IMO is unable to enhance it. Nevertheless, the IMO-plus-bevacizumab combination synergistically inhibits the growth of GEO and LS174T as well as of GEO-CR tumors, preceded by inhibition of signaling protein expression, microvessel formation, and human, but not murine, VEGF secretion. Moreover, IMO inhibited the growth, adhesion, migration, and capillary formation of VEGF-stimulated endothelial cells. The antitumor activity was irrespective of the TLR9 expression on tumor cells. These studies demonstrate that synthetic agonists of TLR9 interfere with growth and angiogenesis also by EGFR- and ADCC-independent mechanisms affecting endothelial cell functions and provide a strong rationale to combine IMO with bevacizumab and EGFR inhibitory drugs in colon cancer patients.

The GPIIIA PlA2 polymorphism is associated with an increased risk of cardiovascular adverse events.

BackgroundThe clinical impact of PlA2 polymorphism has been investigated in several diseases, but the definition of its specific role on thrombotic cardiovascular complications has been challenging. We aimed to explore the effect of PlA2 polymorphism on outcome in patients with atherosclerosis.MethodsWe studied 400 consecutive patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention. A replication study was conducted in 74 hypertensive patients with cerebrovascular events while a group of 100 healthy subjects was included as control population. PlA genotype was determined by PCR-RFLP on genomic DNA from peripheral blood cells. Major adverse cardiac events (MACE), were considered as end points, and recorded at a mean follow up of 24 ± 4.3 months.ResultsThe frequencies of PlA2 polymorphism was similar between groups and genotype distribution was in Hardy-Weinberg equilibrium. In patients with CAD, the presence of PlA2 allele was associated with higher incidence of cardiac death (13.1% vs. 1.5%, p = 0.0001), myocardial infarction (10.7% vs. 2.6%, p = 0.004) and needs of new revascularization (34.8% vs. 17.7%, p = 0.010). Accordingly, the Kaplan-Meier analysis for event free survival in patients harboring the PlA2 allele showed worse long-term outcome for these patients (p = 0.015). Cox regression analysis identified the presence of PlA2 as an independent predictor of cardiac death (OR: 9.594, 95% CI: 2.6 to 35.3, p = 0.002) and overall MACE (OR: 1.829, 95% CI: 1.054 to 3.176, p = 0.032). In the replication study, the PlA2 polymorphism increased the risk of stroke (OR: 4.1, 95% CI: 1.63-12.4, p = 0.02) over TIA and was identified as an independent risk factor for stroke (B:-1.39; Wald: 7.15; p = 0.001).ConclusionsOur study demonstrates that in patients with severe atherosclerosis the presence of PlA2 allele is associated with thrombotic cardiovascular complications.

The dual PI3K/mTOR inhibitor PKI-587 enhances sensitivity to cetuximab in EGFR-resistant human head and neck cancer models

Background:Cetuximab is the only targeted agent approved for the treatment of head and neck squamous cell carcinomas (HNSCC), but low response rates and disease progression are frequently reported. As the phosphoinositide 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) pathways have an important role in the pathogenesis of HNSCC, we investigated their involvement in cetuximab resistance.Methods:Different human squamous cancer cell lines sensitive or resistant to cetuximab were tested for the dual PI3K/mTOR inhibitor PF-05212384 (PKI-587), alone and in combination, both in vitro and in vivo.Results:Treatment with PKI-587 enhances sensitivity to cetuximab in vitro, even in the condition of epidermal growth factor receptor (EGFR) resistance. The combination of the two drugs inhibits cells survival, impairs the activation of signalling pathways and induces apoptosis. Interestingly, although significant inhibition of proliferation is observed in all cell lines treated with PKI-587 in combination with cetuximab, activation of apoptosis is evident in sensitive but not in resistant cell lines, in which autophagy is pre-eminent. In nude mice xenografted with resistant Kyse30 cells, the combined treatment significantly reduces tumour growth and prolongs mice survival.Conclusions:Phosphoinositide 3-kinase/mammalian target of rapamycin inhibition has an important role in the rescue of cetuximab resistance. Different mechanisms of cell death are induced by combined treatment depending on basal anti-EGFR responsiveness.

β2-Adrenergic Receptor Stimulation Improves Endothelial Progenitor Cell–Mediated Ischemic Neoangiogenesis

Rationale: Endothelial progenitor cells (EPCs) are present in the systemic circulation and home to sites of ischemic injury where they promote neoangiogenesis. &bgr;2-Adrenergic receptor (&bgr;2AR) plays a critical role in vascular tone regulation and neoangiogenesis. Objective: We aimed to evaluate the role of &bgr;2AR on EPCs’ function. Methods and Results: We firstly performed in vitro analysis showing the expression of &bgr;2AR on EPCs. Stimulation of wild-type EPCs with &bgr;-agonist isoproterenol induced a significant increase of Flk-1 expression on EPCs as assessed by fluorescence-activated cell sorter. Moreover, &bgr;2AR stimulation induced a significant increase of cell proliferation, improved the EPCs migratory activity, and enhanced the EPCs’ ability to promote endothelial cell network formation in vitro. Then, we performed in vivo studies in animals model of hindlimb ischemia. Consistent with our in vitro results, in vivo EPCs’ treatment resulted in an improvement of impaired angiogenic phenotype in &bgr;2AR KO mice after induction of ischemia, whereas no significant amelioration was observed when &bgr;2AR knock out (KO) EPCs were injected. Indeed, wild-type–derived EPCs’ injection resulted in a significantly higher blood flow restoration in ischemic hindlimb and higher capillaries density at histological analysis as compared with not treated or &bgr;2AR KO EPC-treated mice. Conclusions: The present study provides the first evidence that EPCs express a functional &bgr;2AR. Moreover, &bgr;2AR stimulation results in EPCs proliferation, migration, and differentiation, enhancing their angiogenic ability, both in vitro and in vivo, leading to an improved response to ischemic injury in animal models of hindlimb ischemia.

No-Reflow Phenomenon Pathophysiology, Diagnosis, Prevention, and Treatment. A Review of the Current Literature and Future Perspectives

No-reflow is responsible for 40% of the primary percutaneous coronary intervention without complete myocardial reperfusion despite successful reopening of the infarct-related artery. This review describes the main pathophysiological mechanisms of no-reflow, its clinical manifestation, including the strong association with increased in-hospital mortality, malignant arrhythmias, and cardiac failure as well as the diagnostic methods. The latter ranges from simple angiographic thrombolysis in myocardial infarction grade score to more complex angiographic indexes, imaging techniques such as myocardial contrast echo or cardiac magnetic resonance, and surrogate clinical end points such as ST-segment resolution. This review also summarizes the strategies of prevention and treatment of no-reflow, considering the most recent studies results regarding medical therapy and devices.

Toll-like Receptor 9 Agonist IMO Cooperates with Cetuximab in K-Ras Mutant Colorectal and Pancreatic Cancers

Purpose: K-Ras somatic mutations are a strong predictive biomarker for resistance to epidermal growth factor receptor (EGFR) inhibitors in patients with colorectal and pancreatic cancer. We previously showed that the novel Toll-like receptor 9 (TLR9) agonist immunomodulatory oligonucleotide (IMO) has a strong in vivo activity in colorectal cancer models by interfering with EGFR-related signaling and synergizing with the anti-EGFR monoclonal antibody cetuximab. Experimental Design: In the present study, we investigated, both in vitro and in vivo, the antitumor effect of IMO alone or in combination with cetuximab in subcutaneous colon and orthotopic pancreatic cancer models harboring K-Ras mutations and resistance to EGFR inhibitors. Results: We showed that IMO was able to significantly restore the sensitivity of K-Ras mutant cancer cells to cetuximab, producing a marked inhibition of cell survival and a complete suppression of mitogen—activated protein kinase phosphorylation, when used in combination with cetuximab. IMO interfered with EGFR-dependent signaling, modulating the functional interaction between TLR9 and EGFR. In vivo, IMO plus cetuximab combination caused a potent and long-lasting cooperative antitumor activity in LS174T colorectal cancer and in orthotopic AsPC1 pancreatic cancer. The capability of IMO to restore cetuximab sensitivity was further confirmed by using K-Ras mutant colorectal cancer cell models obtained through homologous recombination technology. Conclusions: We showed that IMO markedly inhibits growth of K-Ras mutant colon and pancreatic cancers in vitro and in nude mice and cooperates with cetuximab via multiple mechanisms of action. Therefore, we propose IMO plus cetuximab as a therapeutic strategy for K-Ras wild-type as well for K-Ras mutant, cetuximab-resistant colorectal and pancreatic cancers. Clin Cancer Res; 17(20); 6531–41. ©2011 AACR.