John P. Fruehauf

Reactive Oxygen Species: A Breath of Life or Death?

New insights into cancer cell–specific biological pathways are urgently needed to promote development of rationally targeted therapeutics. Reactive oxygen species (ROS) and their role in cancer cell response to growth factor signaling and hypoxia are emerging as verdant areas of exploration on the road to discovering cancers Achilles heel. One of the distinguishing and near-universal hallmarks of cancer growth is hypoxia. Unregulated cellular proliferation leads to formation of cellular masses that extend beyond the resting vasculature, resulting in oxygen and nutrient deprivation. The resulting hypoxia triggers a number of critical adaptations that enable cancer cell survival, including apoptosis suppression, altered glucose metabolism, and an angiogenic phenotype. Ironically, recent investigations suggest that oxygen depletion stimulates mitochondria to elaborate increased ROS, with subsequent activation of signaling pathways, such as hypoxia inducible factor 1α, that promote cancer cell survival and tumor growth. Because mitochondria are key organelles involved in chemotherapy-induced apoptosis induction, the relationship between mitochondria, ROS signaling, and activation of survival pathways under hypoxic conditions has been the subject of increased study. Insights into mechanisms involved in ROS signaling may offer novel avenues to facilitate discovery of cancer-specific therapies. Preclinical and clinical evaluation of agents that modify ROS signaling in cancer offers a novel avenue for intervention. This review will cover recent work in ROS-mediated signaling in cancer cells and its potential as a target for developmental therapeutics.

BEAM: A Randomized Phase II Study Evaluating the Activity of Bevacizumab in Combination With Carboplatin Plus Paclitaxel in Patients With Previously Untreated Advanced Melanoma

PURPOSE Metastatic melanoma, a highly vascularized tumor with strong expression of vascular endothelial growth factor, has an overall poor prognosis. We conducted a placebo-controlled, double-blind phase II study of carboplatin plus paclitaxel with or without bevacizumab in patients with previously untreated metastatic melanoma. PATIENTS AND METHODS Patients were randomly assigned in a two-to-one ratio to carboplatin (area under the curve, 5) plus paclitaxel (175 mg/m(2)) and bevacizumab (15 mg/kg; CPB) or placebo (CP) administered intravenously once every 3 weeks. Progression-free survival (PFS) was the primary end point. Secondary end points included overall survival (OS) and safety. RESULTS Two hundred fourteen patients (73% with M1c disease) were randomly assigned. With a median follow-up of 13 months, median PFS was 4.2 months for the CP arm (n = 71) and 5.6 months for the CPB arm (n = 143; hazard ratio [HR], 0.78; P = .1414). Overall response rates were 16.4% and 25.5%, respectively (P = .1577). With 13-month follow-up, median OS was 8.6 months in the CP arm versus 12.3 months in the CPB arm (HR, 0.67; P = .0366), whereas in an evaluation 4 months later, it was 9.2 versus 12.3 months, respectively (HR, 0.79; P = .1916). In patients with elevated serum lactate dehydrogenase (n = 84), median PFS and OS were longer in the CPB arm (PFS: 4.4 v 2.7 months; HR, 0.62; OS: 8.5 v 7.5 months; HR, 0.52). No new safety signals were observed. CONCLUSION The study did not meet the primary objective of statistically significant improvement in PFS with the addition of bevacizumab to carboplatin plus paclitaxel. A larger phase III study will be necessary to determine whether there is benefit to the addition of bevacizumab to carboplatin plus paclitaxel in this disease setting.

Diastolic Blood Pressure as a Biomarker of Axitinib Efficacy in Solid Tumors

Purpose: To evaluate if diastolic blood pressure (dBP) ≥90 mm Hg during axitinib treatment is a marker of efficacy. Experimental Design: The relationship between dBP ≥90 mm Hg and efficacy was retrospectively explored across 5 phase II studies of single-agent axitinib for the treatment of 4 different tumor types. All patients had baseline BP ≤140/90 mm Hg and were stratified into 2 groups based on in-clinic BP measurements after initiating therapy: those with dBP <90 mm Hg throughout therapy and those with at least 1 dBP ≥90 mm Hg. Median overall survival (mOS), median progression-free survival (mPFS), objective response rate (ORR), and adverse events were evaluated by dBP group in individual and pooled analyses. Results: Two-hundred thirty patients were evaluated. Patients with dBP ≥90 mm Hg had a significantly lower relative risk of death than those with dBP <90 mm Hg [adjusted HR (95% CI) = 0.55 (0.39, 0.77); P < 0.001]. The relative risk of progression was also lower in patients with dBP ≥90 mm Hg [HR (95% CI) = 0.76 (0.54, 1.06), P = 0.107], and ORR was significantly higher (43.9% vs. 12.0%; P < 0.001). In an 8-week landmark analysis, mOS (25.8 vs. 14.9 months) and mPFS (10.2 vs. 7.1 months) were greater for patients in the ≥90 mm Hg group. Adverse events were similar between groups. Conclusions: Axitinib efficacy correlated with dBP ≥90 mm Hg. Further investigation of dBP as a predictive biomarker of efficacy in patients receiving axitinib is warranted. Clin Cancer Res; 17(11); 3841–9. ©2011 AACR.

Correlation of dynamic contrast enhancement MRI parameters with microvessel density and VEGF for assessment of angiogenesis in breast cancer

To investigate the association between parameters obtained from dynamic contrast enhanced MRI (DCE‐MRI) of breast cancer using different analysis approaches, as well as their correlation with angiogenesis biomarkers (vascular endothelial growth factor and vessel density).

Prediction of drug response in breast cancer using integrative experimental/computational modeling

Nearly 30% of women with early-stage breast cancer develop recurrent disease attributed to resistance to systemic therapy. Prevailing models of chemotherapy failure describe three resistant phenotypes: cells with alterations in transmembrane drug transport, increased detoxification and repair pathways, and alterations leading to failure of apoptosis. Proliferative activity correlates with tumor sensitivity. Cell-cycle status, controlling proliferation, depends on local concentration of oxygen and nutrients. Although physiologic resistance due to diffusion gradients of these substances and drugs is a recognized phenomenon, it has been difficult to quantify its role with any accuracy that can be exploited clinically. We implement a mathematical model of tumor drug response that hypothesizes specific functional relationships linking tumor growth and regression to the underlying phenotype. The model incorporates the effects of local drug, oxygen, and nutrient concentrations within the three-dimensional tumor volume, and includes the experimentally observed resistant phenotypes of individual cells. We conclude that this integrative method, tightly coupling computational modeling with biological data, enhances the value of knowledge gained from current pharmacokinetic measurements, and, further, that such an approach could predict resistance based on specific tumor properties and thus improve treatment outcome.

Mathematical modeling of cancer progression and response to chemotherapy

The complex, constantly evolving and multifaceted nature of cancer has made it difficult to identify unique molecular and pathophysiological signatures for each disease variant, consequently hindering development of effective therapies. Mathematical modeling and computer simulation are tools that can provide a robust framework to better understand cancer progression and response to chemotherapy. Successful therapeutic agents must overcome biological barriers occurring at multiple space and time scales and still reach targets at sufficient concentrations. A multiscale computer simulator founded on the integration of experimental data and mathematical models can provide valuable insights into these processes and establish a technology platform for analyzing the effectiveness of chemotherapeutic drugs, with the potential to cost-effectively and efficiently screen drug candidates during the drug-development process.

Multicenter, Phase II Study of Axitinib, a Selective Second-Generation Inhibitor of Vascular Endothelial Growth Factor Receptors 1, 2, and 3, in Patients with Metastatic Melanoma

Purpose: This multicenter, open-label, phase II study evaluated the safety and clinical activity of axitinib, a potent and selective second-generation inhibitor of vascular endothelial growth factor receptors (VEGFR)–1, 2, and 3, in patients with metastatic melanoma. Experimental Design: Thirty-two patients with a maximum of one prior systemic therapy received axitinib at a starting dose of 5 mg twice daily. The primary endpoint was objective response rate. Results: Objective response rate was 18.8% [95% confidence interval (CI), 7.2–36.4], comprising one complete and five partial responses with a median response duration of 5.9 months (95% CI, 5.0–17.0). Stable disease at 16 weeks was noted in six patients (18.8%), with an overall clinical benefit rate of 37.5%. Six-month progression-free survival rate was 33.9%, 1-year overall survival rate was 28.1%, and median overall survival was 6.6 months (95% CI, 5.2–9.0). The most frequently (>15%) reported nonhematologic, treatment-related adverse events were fatigue, hypertension, hoarseness, and diarrhea. Treatment-related fatal bowel perforation, a known class effect, occurred in one patient. Axitinib selectively decreased plasma concentrations of soluble VEGFR (sVEGFR)-2 and sVEGFR-3 compared with soluble stem cell factor receptor (sKIT). No significant association was noted between plasma levels of axitinib and response. However, post hoc analyses indicated potential relationships between efficacy endpoints and diastolic blood pressure of 90 mm Hg or higher as well as baseline serum lactate dehydrogenase levels. Conclusions: Axitinib was well tolerated, showed a selective VEGFR-inhibitory profile, and showed single-agent activity in metastatic melanoma. Further evaluations of axitinib, alone and combined with chemotherapy, are ongoing. Clin Cancer Res; 17(23); 7462–9. ©2011 AACR.

The prognostic value of tumor markers in patients with glioblastoma multiforme: analysis of 32 patients and review of the literature.

Although several studies have examined brain tumor markers for prognostic value, few investigations have stratified analysis based on specific histologic grade. The objective of this study was to evaluate a single histologic grade of glioma, the grade IV glioma or glioblastoma (World Health Organization Classification), with a comprehensive panel of tumor markers in an attempt to identify those with prognostic significance. Tumor samples from a cohort of patients with glioblastoma multiforme (n=32) were examined for tumor markers, DNA analysis, and clinical variables in an attempt to determine a ‘profile’ for this tumor. We used univariate and multivariate statistical analysis to determine the prognostic value of tumor cell ploidy, percent S-phase, DNA index, p53, and Ki-67 labeling index, as well as the variables of gender, race, age, location of tumor, history of chemotherapy, and primary versus recurrent tumor. Two additional tumor markers, multidrug resistance gene 1 and glutathione-S-transferase subtype pi, were included in the sample testing, but were not analyzed statistically. Univariate analysis indicated that increasing age had a strong association with decreased survival. Female gender, increasing Ki-67, no chemotherapy before sample collection, and primary glioblastoma showed some association with decreased survival in the univariate model. The univariate results indicated that race, side of tumor, ploidy, S-phase, DNA index, and p53 had no prognostic value. Multivariate modeling demonstrated that age, gender, and Ki-67 were the strongest factors associated with survival. The relevant literature is reviewed.

Reactive oxygen species: an Achilles' heel of melanoma?

The successful treatment of melanoma has been hampered by the unique biology of this cancer. Fortunately, research to further our understanding of how melanoma cells differ from normal tissues has led to the discovery of potential new avenues of attack. One promising strategy relates to targeting the excess free radicals produced by melanomas. Melanocyte transformation into cancer is associated with significant structural alterations in the melanosome. In addition to pigment production, melanosomes also protect the cell by scavenging free radicals generated by sunlight and cellular metabolism. In melanoma, the disrupted and disorganized melanosome structure reverses this process. Melanosomes found in melanoma produce free radicals, such as hydrogen peroxide, furthering DNA damage. Melanosome generation of reactive oxygen species (ROS), in tandem with those generated by cancer metabolism, activate cellular signal transduction pathways that prevent cell death. ROS activation of proto–oncogene pathways in melanoma contributes to their resistance to chemotherapy. Fortunately, it may be possible to target these free radicals, just as Paris was able to successfully target Achilles’ heel. The use of agents that block ROS scavenging, such as ATN-224 and disulfiram, have been explored clinically. A recent randomized Phase II trial with elesclomol, an agent that generates ROS, in combination with paclitaxel led to improved patient survival, suggesting that this may be a viable approach to advance the treatment of melanoma.

Anti-angiogenic effects of resveratrol mediated by decreased VEGF and increased TSP1 expression in melanoma-endothelial cell co-culture.

Resveratrol, a naturally occurring polyphenol, has been reported to be an anti-tumor and chemopreventive agent. Recent data show that it may also exert anti-angiogenic effects. We hypothesized that the anti-angiogenic activity of resveratrol may be caused by modulation of tumor cell release of thrombospondin-1 (TSP1) and vascular endothelial growth factor (VEGF) into the extracellular matrix, leading to vascular endothelial cell (VEC) apoptosis. We therefore evaluated the effects of resveratrol on melanoma cell lines co-cultured with vascular endothelial cells in monolayer and in three dimensional spheroids. We found that resveratrol stimulated isolated VEC proliferation, while it caused growth inhibition of VECs grown with melanoma cells in three-dimensional co-culture. This effect was associated with increased melanoma cell expression of tumor suppressor protein 53 and matrix protein TSP1, as well as decreased hypoxia-driven expression of hypoxia inducible factor-1α and inhibition of VEGF production.