Targeting angiogenesis in advanced breast cancer

Toll-Like Receptor 7 Mediates Inflammation Resolution and Inhibition of Angiogenesis in Non-Small Cell Lung Cancer

Simple Summary

The progression of cancer is strictly linked to the formation of new blood vessels responsible for nutrition supply of the tumor. We identified TLR7 as an inhibitor of lung cancer vascularization. TLR7 is part of a large family of immune receptors that function as “sensors” of pathogen- and damage-derived signals. We found that TLR7 exerts antitumor functions in non-small cell lung cancer by inducing the production of specific molecules with inhibitory properties against new blood vessel formation. These molecules are known as specialized pro-resolving mediators (SPMs) and are derived from ω-3 and ω-6 fatty acids. We believe that the results obtained suggest novel potential targets and strategies to treat lung cancer.

Abstract

Pattern recognition receptors (PRR) promote inflammation but also its resolution. We demonstrated that a specific PRR—formyl peptide receptor 1 (FPR1)—sustains an inflammation resolution response with anti-angiogenic and antitumor potential in gastric cancer. Since toll-like receptor 7 (TLR7) is crucial in the physiologic resolution of airway inflammation, we asked whether it could be responsible for pro-resolving and anti-angiogenic responses in non-small cell lung cancer (NSCLC). TLR7 correlated directly with pro-resolving and inversely with angiogenic mediators in NSCLC patients, as revealed by a publicly available RNAseq analysis. In NSCLC cells, depletion of TLR7 caused an upregulation of angiogenic mediators and a stronger vasculogenic response of endothelial cells compared to controls, assessed by qPCR, ELISA, protein array, and endothelial cell responses. TLR7 activation induced the opposite effects. TLR7 silencing reduced, while its activation increased, the pro-resolving potential of NSCLC cells, evaluated by qPCR, flow cytometry, and EIA. The increased angiogenic potential of TLR7-silenced NSCLC cells is due to the lack of pro-resolving mediators. MAPK and STAT3 signaling are responsible for these activities, as demonstrated through Western blotting and inhibitors. Our data indicate that TLR7 sustains a pro-resolving signaling in lung cancer that inhibits angiogenesis. This opens new possibilities to be exploited for cancer treatment.

Efficacy of Bevacizumab-Capecitabine in Combination for the First-Line Treatment of Metastatic Breast Cancer

There is an ongoing need for development of new chemotherapeutic regimens for metastatic breast cancer [mBC], especially when tumors lack therapeutic targets such as the estrogen or progesterone receptor [ER/PR], or the human epidermal growth factor receptor-2 [HER2]. Capecitabine is an orally bioavailable fluoropyrimidine approved for monotherapy in mBC, and bevacizumab is a monoclonal antibody targeting vascular endothelial growth factor which has shown to be active in mBC and tolerable in combination with other chemotherapeutics. The combination of these two agents has been explored in multiple phase II and III clinical studies, with improvements in progression-free survival and overall response rates noted as compared to capecitabine monotherapy. However, the use of bevacizumab in combination with capecitabine and other chemotherapy agents for mBC remains beset with controversy due to safety concerns, cost issues, and pending regulatory decisions.

AAV-P125A-endostatin and paclitaxel treatment increases endoreduplication in endothelial cells and inhibits metastasis of breast cancer

Endostatin potentiates the antimitotic effects of paclitaxel (taxol) on endothelial cells (ECs). P125A-endostatin and taxol-treated ECs showed multipolar spindles and nuclear lobulation, leading to mitotic catastrophe and cell death. Induction of nuclear abnormalities was found to be dependent on β-catenin levels as wnt-mediated overexpression of β-catenin reversed the changes in nuclear morphology. These results prompted us to investigate whether antiangiogenic gene therapy and paclitaxel chemotherapy can synergistically inhibit angiogenesis and tumor growth. We first determined the effect of combination treatment in a transgenic mouse model of breast cancer. Intramuscular injection of recombinant adeno-associated virus type-2 virus induced sustained expression of P125A-endostatin. In vivo studies showed that combination therapy inhibited mammary cancer growth, delayed the onset of multifocal mammary adenocarcinomas, decreased tumor angiogenesis and increased survival in treated mice. In a second model, female athymic mice were orthotopically transplanted with a metastatic human breast cancer cell line. Antiangiogenic gene therapy in combination with paclitaxel inhibited tumor angiogenesis and lung/lymph-node metastasis in this model. These studies demonstrate cooperation between endostatin gene therapy and chemotherapy to inhibit tumor initiation, growth and metastasis.

Inhibition of breast cancer cell growth and invasiveness by dual silencing of HER-2 and VEGF

Overexpression of HER-2 accounts for approximately 25% of all breast cancer cases, while 87.7% of HER-2 positive breast cancers are associated with upregulated VEGF. The objective of this study is to explore the combination therapy of blocking HER-2 and VEGF expressions simultaneously using siRNA. This is the first report to examine the effect of dual silencing of HER-2 and VEGF genes on tumor growth and invasiveness. We have designed nine HER-2 siRNAs and ten VEGF siRNAs, and identified potent siRNA which can silence the target gene up to 75-83.5%. The most potent HER-2 and VEGF siRNAs were used to conduct functional studies in HER-2 positive breast cancer cells. Tumor invasiveness properties including cell morphology change, in vitro migration, cell spreading, and adhesion to ECM were evaluated. In addition, cell proliferation and apoptosis were examined after the siRNA treatment. Our data demonstrated for the first time that HER-2 siRNA could inhibit cell migration and invasion abilities. Combination of HER-2 and VEGF siRNAs exhibited synergistic silencing effect on VEGF. Both HER-2 siRNA and VEGF siRNA showed significant inhibition on cell migration and proliferation. HER-2 siRNA also demonstrated dramatic suppression on cell spreading and adhesion to ECM, as well as induction of apoptosis. Dual silencing of HER-2 and VEGF exhibited significant cell morphology change, and substantial suppression on migration, spreading, cell adhesion, and proliferation. Our observations suggested that HER-2 positive breast cancer may be more effectively treated by dual inhibition of HER-2 and VEGF gene expressions using siRNA.

The role of HER2 in cancer therapy and targeted drug delivery

HER2 is highly expressed in a significant proportion of breast cancer, ovarian cancer, and gastric cancer. Since the discovery of its role in tumorigenesis, HER2 has received great attention in cancer research during the past two decades. Successful development of the humanized monoclonal anti-HER2 antibody (Trastuzumab) for the treatment of breast cancer further spurred scientists to develop various HER2 specific antibodies, dimerization inhibitors and kinase inhibitors for cancer therapy. On the other hand, the high expression of HER2 and the accessibility of its extracellular domain make HER2 an ideal target for the targeted delivery of anti-tumor drugs as well as imaging agents. Although there is no natural ligand for HER2, artificial ligands targeting HER2 have been developed and applied in various targeted drug delivery systems. The emphasis of this review is to elucidate the roles of HER2 in cancer therapy and targeted drug delivery. The structure and signal pathway of HER2 will be briefly described. The role of HER2 in tumorigenesis and its relationship with other tumor markers will be discussed. For the HER2 targeted cancer therapy, numerous strategies including the blockage of receptor dimerization, inhibition of the tyrosine kinase activity, and interruption of the downstream signal pathway will be summarized. For the targeted drug delivery to HER2 positive tumor cells, various targeting ligands and their delivery systems will be described in details.

In vivo monitoring of angiogenesis inhibitory treatment effects by dynamic contrast-enhanced computed tomography in a xenograft tumor model

RATIONALE AND OBJECTIVES

To evaluate the potential of dynamic CT enhanced by iohexol or a novel macromolecular contrast agent, PEG12000-Gen4-triiodo, to monitor microvascular changes in tumors treated with the angiogenesis inhibitor bevacizumab.

MATERIALS AND METHODS

Ten female nude rats with MDA-MB 435 xenograft tumors were treated with 1 mg intraperitoneal bevacizumab when tumors reached 1 cm diameter and, for 4 rats, treated again 7 days later. Just before and 24 hours after the first injection of anti-VEGF antibody, the tumors were imaged by dynamic CT scans enhanced with PEG12000-Gen4-triiodo (n = 3 rats) or iohexol (n = 3 rats). The other 4 rats underwent dynamic CT scans enhanced with PEG12000-Gen4-triiodo just before and 24 hours after the second injection of anti-VEGF antibody. Microvascular leakiness (K(PS)) was calculated for the tumors using a 2-compartment tissue model.

RESULTS

PEG12000-Gen4-triiodo-enhanced CT scans showed progressive reductions in K(PS) from day 1 to 2 to 9 (from 2.55 to 1.27 to 0.69 microL min(-1) cm(-3), respectively, P < 0.005 for each comparison of day 1-2 and day 2-9). No significant difference was seen in the K(PS) estimates derived from iohexol-enhanced CT scans obtained before or after treatment (276 vs. 223.8 microL min(-1) cm(-3), respectively, P = 0.54). The microvascular leak (K(PS)) was significantly larger for iohexol than for PEG12000-Gen4-triiodo-enhanced CT, P < 0.05.

CONCLUSION

Dynamic macromolecular contrast-enhanced CT can be used to monitor serial decreases in tumor microvessel leakiness induced by repeated doses of an angiogenesis inhibitor drug.

Anti-angiogenesis effect of generation 4 polyamidoamine/vascular endothelial growth factor antisense oligodeoxynucleotide on breast cancer in vitro

OBJECTIVE

To study the effects of the generation 4 polyamidoamine/vascular endothelial growth factor antisense oligodeoxynucleotide (G4PAMAM/VEGFASODN) compound on the expressions of vascular endothelial growth factor (VEGF) and its mRNA of breast cancer cells and on the inhibition of vascular endothelial cells.

METHODS

We examined the morphology of G4PAMAM/VEGFASODN compound and its pH stability, in vitro transfection efficiency and toxicity, and the expressions of VEGF and its mRNA. Methyl thiazolyl tetrazolium assay was used to detect the inhibitory function of the compound on vascular endothelial cells.

RESULTS

The compound was about 10 nm in diameter and was homogeneously netlike. From pH 5 to 10, it showed quite a buffered ability. The 48-h transfection rate in the charge ratio of 1:40 was 98.76%, significantly higher than that of the liposome group (P<0.05). None of the transfection products showed obvious toxicity on the cells. The expressions of both VEGF protein and its mRNA after G4PAMAM/VEGFASODN transfection decreased markedly.

CONCLUSION

With a low toxicity, high safety, and high transfection rate, G4PAMAM/VEGFASODN could be a promising gene vector. Specifically, it inhibits VEGF gene expression efficiently, laying a basis for further in vivo animal studies.

Molecularly targeted therapeutics for breast cancer

Thomas Beatson's celebrated description in 1896 of bilateral oophorectomy as effective therapy for premenopausal breast cancer could be considered as the first demonstration of response of any cancer to a 'targeted therapy.' At that time, however, the understanding of the mechanism of the intervention was minimal. In recent years a host of new rationally designed, molecularly targeted cancer therapies have been introduced from both large pharmaceutic and small biotechnology companies, and the portfolio of new targeted treatments in the pipeline appears to be unending. The existence of this array of potential new therapies is the result of a prodigious effort in the researching and defining of the molecular components of the cancer phenotype, and the subsequent rational design of agents to target candidate pathways. Experience with endocrine therapy has shown that targeted therapies require the target to be not merely expressed in the cancer phenotype, but important in regulating growth of cancer cells. We may well look back at many of the current targeted therapy trials as unrealistically simplistic in failing to adequately and define the target phenotype. This approach risks rejecting highly active treatments for a small subgroup of a study population where minimal activity is present for the majority. The future for breast cancer therapy is promising, but it is important to be prepared for disappointment, as early success in animal models cannot guarantee a successful human therapy. Stunning results such as the adjuvant trastuzumab trials are likely to remain the exceptions rather that the rule, and most gains will be modest advances. A better understanding of the molecular biology of cancer may also aid in guiding the most appropriate use of existing therapies such as conventional chemotherapy. This knowledge will facilitate the rational selection of drug combinations and/or sequencing based on their mechanisms of action at a molecular level. The aim of this paper is to review the current state-of-the-art in novel targeted therapies for breast cancer based on an understanding of this disease at the molecular level, with particular reference to those agents entering the clinic.