Hypoxia-Inducible Factor-1 Target Genes as Indicators of Tumor Vessel Response to Vascular Endothelial Growth Factor Inhibition

Abstract

Antiangiogenic therapy improves survival in patients with advanced stage cancers. Currently, there are no reliable predictors or markers for tumor vessel response to antiangiogenic therapy. To model effective antiangiogenic therapy, we disrupted the VEGF gene in three representative cancer cell lines. HCT116 xenografts had low proportions of endothelial tubes covered by pericytes that stained with A-smooth muscle actin (SMA) antibody. Upon disruption of VEGF, HCT116 VEGFÀ/À xenografts had significantly decreased tumor microvessel perfusion compared with their parental counterparts. Furthermore, HCT116 VEGFÀ/À xenografts mounted a tumor-reactive response to hypoxia, characterized by the induction of hypoxia-inducible factor-1 (HIF-1) target genes. One highly induced protein was DPP4, a measurable serum protein that has well-described roles in cancer progression. In contrast, LS174T and MKN45 tumor xenografts had high proportion of endothelial tubes that were covered by SMA+ pericytes. Upon disruption of VEGF, LS174TVEGFÀ/À and MKN45 VEGFÀ/À xenografts maintained tumor microvessel perfusion. As such, there were no changes in intratumoral hypoxia or HIF-1A induction. Together, these data show that the extent of tumor vessel response to angiogenic inhibition could be correlated with (a) the preexisting coverage of tumor endothelial tubes with SMA+ pericytes and (b) differential tumor induction of HIF-1 target genes. The data further show that DPP4 is a novel marker of HIF-1 induction. Altogether, these preclinical findings suggest novel clinical trials for predicting and monitoring tumor vessel responses to antiangiogenic therapy.

Hyperpolarized 13C Spectroscopy Detects Early Changes in Tumor Vasculature and Metabolism after VEGF Neutralization

“…6B). These changes in LDH activity and lactate concentration were consistent with an increase in hypoxia in the LoVo tumors (29,41). There was no change in fumarase activity from the pretreatment level of 0.40 AE 0.04 mmole/min/mg protein (Fig.…”

“…In this preclinical study, we sought to detect early metabolic and vascular changes induced by bevacizumab treatment in 2 colorectal cancer xenograft models with differential sensitivity to VEGF blockade. LoVo tumors display a higher dependence on VEGF, with greater vessel permeability (31) and lower vessel pericyte coverage (29) than HT29 tumors, therefore upon VEGF blockade will exhibit reduced MVD and perfusion, along with marked expansion of hypoxic regions (29). Conversely, HT29 tumor cells are less sensitive to VEGF Figure 4.…”

“…Flux of hyperpolarized 13 C label between pyruvate and lactate is sensitive to tumor perfusion, membrane transport of pyruvate, endogenous lactate concentration, and lactate dehydrogenase (LDH) activity (27), whereas the production of labeled malate from fumarate has been shown to be a sensitive indicator of tumor cell necrosis (28). In this study, we show that hyperpolarized 13 C MRS can detect the early effects of antiangiogenic therapy in 2 colorectal cancer xenograft models (LoVo and HT29) that are known to display differential response to VEGF blockade, being more and less sensitive, respectively (29)(30)(31). Furthermore, we compare these results with those obtained using functional MRI techniques that are used currently in the clinic, as the first clinical trial of hyperpolarized [1][2][3][4][5][6][7][8][9][10][11][12][13] C]pyruvate is now underway (32).…”

Epithelial-to-mesenchymal transition confers pericyte properties on cancer cells

“…However, microscopic studies have revealed the nearly ubiquitous presence of pericytes on tumor vessels, although such pericytes are more loosely attached to the vasculature and at reduced density compared with respective normal tissues (25,(43)(44)(45). Different cancer cells exhibit dramatically varying pericyte coverage when transplanted to form tumor xenografts (46). In our study, DCIS cell-derived tumor xenografts had very few pericytes whereas blood vessels in neuT tumors were well covered by pericytes ( Figure 7A and Supplemental Figures 1B and 8).…”

Gene Expression Signatures Predictive of Bevacizumab/Erlotinib Therapeutic Benefit in Advanced Nonsquamous Non–Small Cell Lung Cancer Patients (SAKK 19/05 trial)

“…However, survival benefits are observed only in a subset of patients, as a significant number of patients show only modest response presumably because of intrinsic or rapidly acquired resistance to antiangiogenic therapy (14). One proposed mechanism of resistance to antiangiogenic agents is the onset of hypoxia within the tumor as a result of vessel regression during the course of antiangiogenic therapy (15,16). Moreover, effective inhibition of neovascularization using antiangiogenic therapy was shown in some cases to change the phenotype of tumors by increasing their invasion and metastatic potential (17).…”