Antivascular agents for non-small-cell lung cancer: current status and future directions

Proteomic response to 5,6-dimethylxanthenone 4-acetic acid (DMXAA, vadimezan) in human non-small cell lung cancer A549 cells determined by the stable-isotope labeling by amino acids in cell culture (SILAC) approach

5,6-Dimethylxanthenone 4-acetic acid (DMXAA), also known as ASA404 and vadimezan, is a potent tumor blood vessel-disrupting agent and cytokine inducer used alone or in combination with other cytotoxic agents for the treatment of non-small cell lung cancer (NSCLC) and other cancers. However, the latest Phase III clinical trial has shown frustrating outcomes in the treatment of NSCLC, since the therapeutic targets and underlying mechanism for the anticancer effect of DMXAA are not yet fully understood. This study aimed to examine the proteomic response to DMXAA and unveil the global molecular targets and possible mechanisms for the anticancer effect of DMXAA in NSCLC A549 cells using a stable-isotope labeling by amino acids in cell culture (SILAC) approach. The proteomic data showed that treatment with DMXAA modulated the expression of 588 protein molecules in A549 cells, with 281 protein molecules being up regulated and 306 protein molecules being downregulated. Ingenuity pathway analysis (IPA) identified 256 signaling pathways and 184 cellular functional proteins that were regulated by DMXAA in A549 cells. These targeted molecules and signaling pathways were mostly involved in cell proliferation and survival, redox homeostasis, sugar, amino acid and nucleic acid metabolism, cell migration, and invasion and programed cell death. Subsequently, the effects of DMXAA on cell cycle distribution, apoptosis, autophagy, and reactive oxygen species (ROS) generation were experimentally verified. Flow cytometric analysis showed that DMXAA significantly induced G₁ phase arrest in A549 cells. Western blotting assays demonstrated that DMXAA induced apoptosis via a mitochondria-dependent pathway and promoted autophagy, as indicated by the increased level of cytosolic cytochrome c, activation of caspase 3, and enhanced expression of beclin 1 and microtubule-associated protein 1A/1B-light chain 3 (LC3-II) in A549 cells. Moreover, DMXAA significantly promoted intracellular ROS generation in A549 cells. Collectively, this SILAC study quantitatively evaluates the proteomic response to treatment with DMXAA that helps to globally identify the potential molecular targets and elucidate the underlying mechanism of DMXAA in the treatment of NSCLC.

Localization of sunitinib, its metabolites and its target receptors in tumour-bearing mice: a MALDI-MS imaging study

BACKGROUND AND PURPOSE

The clinical effects of anti-angiogenic agents remain controversial. Therefore, elucidating the pharmacological properties of these compounds is a pivotal issue.

EXPERIMENTAL APPROACH

The effects of treatment with sunitinib on tumour and normal tissues of mice bearing C-26 adenocarcinoma cells were analysed by matrix-assisted laser desorption ionization MS imaging (MALDI-MSI). Expression of the key targets of sunitinib--angiogenic receptors--was studied by immunofluorescent labelling.

KEY RESULTS

MALDI-MS assays showed that sunitinib and its fragment ions were present throughout tumour and normal tissues. Major metabolites were identified in blood and solid tissues, while minor drug metabolites were detectable only in blood. Tumour growth and intratumour VEGF receptor-2 expressions were significantly reduced in sunitinib-treated mice, while the expression of the other targeted receptors, PDGF receptor -α or -β and fibroblast growth factor receptor-1, remained unaffected. Within tumour tissue, the close proximity of sunitinib metabolites to the precursor ion suggested in situ metabolism of the administered drug. There were intratumour areas where the signal intensity of sunitinib correlated with expression of VEGF receptor-2.

CONCLUSIONS AND IMPLICATIONS

This is the first study that demonstrates MALDI-MSI is a versatile platform to study the intratumour localization of an unlabelled anti-angiogenic drug. The combination of MALDI-MSI and immunofluorescence analysis can provide further insights into the molecular interaction of drug compounds and their targets within tumour tissue.

Posttreatment plasma VEGF levels may be associated with the overall survival of patients with advanced non-small cell lung cancer treated with bevacizumab plus chemotherapy

We sought to find blood-based biomarkers that can be used to predict efficacy in advanced non-small cell lung cancer patients treated with bevacizumab plus chemotherapy. Blood was collected before treatment and after 6 weeks of therapy from patients who were participating in a phase 4 trial. Plasma vascular endothelial growth factor (VEGF) levels were evaluated by ELISA. A total of eight single nucleotide polymorphisms in four candidate genes were analyzed by PCR and sequencing. A total of 45 patients enrolled in a clinical trial at Guangdong General Hospital between August 2007 and March 2008 were used as subjects. The median survival times of OS was 25.6 and 13.4 months in the low and high groups, respectively, when the median posttreatment plasma VEGF level (46.63 pg/ml) was used as the cut-off point (P = 0.0284). Patients carrying the AA genotype at the -6C > A polymorphism in laminin 5 (LN5) were more likely to exhibit reduced hemoglobin compared with patients carrying the CA/CC genotype (OR = 8.364, χ(2) = 5.34, P = 0.021). Similar associations were found at the -89A > G and -260C > A polymorphisms in LN5. Patients with the CC genotype at the -6C > A polymorphism in LN5 had an increased risk of neutropenia than those with the CA/AA genotype (OR = 4.444, χ(2) = 5.116, P = 0.030). Our results show improved survival in patients with lower posttreatment plasma VEGF levels treated with bevacizumab plus chemotherapy; thus, the posttreatment plasma VEGF level may be a promising biomarker to predict clinical benefit early in the course of therapy. Polymorphisms in LN5 were associated with a reduced level of hemoglobin and neutropenia.

Apelin expression in human non-small cell lung cancer: role in angiogenesis and prognosis

INTRODUCTION

The recently discovered bioactive peptide, apelin, has been demonstrated to stimulate angiogenesis in various experimental systems. However, its clinical significance and role in tumor vascularization have not yet been investigated in a human malignancy. Therefore, our aim was to study whether apelin expression is associated with angiogenesis and/or tumor growth/behavior in human non-small cell lung cancer (NSCLC).

METHODS

A total of 94 patients with stage I-IIIA NSCLC and complete follow-up information were included. Apelin expression in human NSCLC samples and cell lines was measured by quantitative reverse-transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. Effects of exogenous apelin and apelin transfection were studied on NSCLC cell lines in vitro. In vivo growth of tumors expressing apelin or control vectors were also assessed. Morphometric variables of human and mouse tumor capillaries were determined by anti-CD31 labeling.

RESULTS

Apelin was expressed in all of the six investigated NSCLC cell lines both at the mRNA and protein levels. Although apelin overexpression or apelin treatments did not increase NSCLC cell proliferation in vitro, increasing apelin levels by gene transfer to NSCLC cells significantly stimulated tumor growth and microvessel densities and perimeters in vivo. Apelin mRNA levels were significantly increased in human NSCLC samples compared with normal lung tissue, and high apelin protein levels were associated with elevated microvessel densities and poor overall survival.

CONCLUSIONS

This study reveals apelin as a novel angiogenic factor in human NSCLC. Moreover, it also provides the first evidence for a direct association of apelin expression with clinical outcome in a human cancer.