Multiple circulating proangiogenic factors induced by sunitinib malate are tumor-independent and correlate with antitumor efficacy. Proc Natl Acad Sci U S A. 2007;104:17069-17074. [PMID: 17942672 DOI: 10.1073/pnas.0708148104]

VEGF and angiopoietin signaling in tumor angiogenesis and metastasis

Solid tumors require blood vessels for growth and dissemination, and lymphatic vessels as additional conduits for metastatic spread. The identification of growth factor receptor pathways regulating angiogenesis has led to the clinical approval of the first antiangiogenic molecules targeted against the vascular endothelial growth factor (VEGF)-VEGF receptor (VEGFR)-2 pathway. However, in many cases resistance to anti-VEGF-VEGFR therapy occurs, and thus far the clinical benefit has been limited to only modest improvements in overall survival. Therefore, novel treatment modalities are required. Here, we discuss the members of the VEGF-VEGFR family as well as the angiopoietin growth factors and their Tie receptors as potential novel targets for antiangiogenic and antilymphangiogenic therapies.

Phase II study of sunitinib as first-line treatment of urothelial cancer patients ineligible to receive cisplatin-based chemotherapy: baseline interleukin-8 and tumor contrast enhancement as potential predictive factors of activity

BACKGROUND

A strong rationale supports the role of antiangiogenic drugs in urothelial cancer. This trial was designed to assess the activity of sunitinib as first-line treatment in patients with metastatic urothelial cancer ineligible for cisplatin and to explore molecular and imaging variables predictive of clinical benefit.

PATIENTS AND METHODS

This was a multicenter phase II trial with sunitinib 50 mg daily in 4/2-week schedule. Eligibility criteria were as follows: creatinine clearance 30-60 ml/min, Eastern Cooperative Oncology Group Pperformance Sstatus of one or less, and adequate hepatic and hematologic function. Twelve circulating cytokines were evaluated at baseline and sequentially using Luminex xMAP(®) (Austin, TX). Baseline and treatment-related changes in perfusion were evaluated in a patient subgroup using contrast-enhanced computed tomography.

RESULTS

On intention-to-treat analysis, 38 patients showed 3 (8%) partial responses (PRs) and 19 (50%) presented with stable disease (SD), 17 (45%) of them ≥3 months. Clinical benefit (PR + SD) was 58%. Median time to progression (TTP) was 4.8 months and median overall survival 8.1 months. Toxicity was consistent with previous reports for sunitinib. Low interleukin-8 (IL-8) baseline levels were significantly associated with increased TTP. Baseline tumor contrast enhancement with >40 Hounsfield units was associated with clinical benefit.

CONCLUSIONS

This study highlights the potential role of the angiogenic pathway as a therapy target in urothelial cancer. Baseline IL-8 serum levels and contrast enhancement of lesions warrant further study.

Chronic exposure of colorectal cancer cells to bevacizumab promotes compensatory pathways that mediate tumour cell migration

BACKGROUND

Bevacizumab (Bev), a monoclonal antibody to vascular endothelial growth factor (VEGF), is used in combination with chemotherapy for the treatment of metastatic colorectal cancer (CRC). The effects of Bev on angiogenesis have been well described, but the direct effect of Bev on tumour cells is unknown. This study was carried out to determine the molecular and phenotypic changes in CRC cells after chronic Bev exposure in vitro.

METHODS

Human CRC cell lines were chronically exposed (3 months) to Bev in vitro to develop Bev-adapted (Bev-A) cell lines. Vascular endothelial growth factor family members were determined by reverse transcription-polymerase chain reaction and western blotting. Migration and invasion was determined using standard in vitro assays. Intravenous injection of tumour cells was carried out to evaluate metastatic potential in mice.

RESULTS

Bevacizumab-adapted cells were found to be more migratory and invasive than control cells (P<0.001). Bevacizumab-adapted cells showed higher levels of VEGF-A, -B, -C, placental growth factor (PlGF), VEGF receptor-1 (VEGFR-1) and phosphorylation of VEGFR-1. Furthermore, treatment with SU5416, a VEGFR protein tyrosine kinase inhibitor, led to significantly decreased cell migration in vitro (P<0.001). Bevacizumab-adapted cells were more metastatic in vivo (P<0.05).

CONCLUSION

Chronic exposure of CRC cells to Bev (1) increased expression of VEGF-A, -B, -C, PlGF, VEGFR-1 and VEGFR-1 phosphorylation, (2) increased tumour cell migration and invasion, and (3) metastatic potential in vivo. Our study shows the functional significance of autocrine VEGF signalling in CRC cells.

Levels of circulating CD45(dim)CD34(+)VEGFR2(+) progenitor cells correlate with outcome in metastatic renal cell carcinoma patients treated with tyrosine kinase inhibitors

Background:

Predicting the efficacy of antiangiogenic therapy would be of clinical value in patients (pts) with metastatic renal cell carcinoma (mRCC). We tested the hypothesis that circulating endothelial cell (CEC), bone marrow-derived CD45^dimCD34⁺VEGFR2⁺ progenitor cell or plasma angiogenic factor levels are associated with clinical outcome in mRCC pts undergoing treatment with tyrosine kinase inhibitors (TKI).

Methods:

Fifty-five mRCC pts were prospectively monitored at baseline (day 1) and day 14 during treatment (46 pts received sunitinib and 9 pts received sorafenib). Circulating endothelial cells (CD45⁻CD31⁺CD146⁺7-amino-actinomycin (7AAD)⁻ cells) were measured in 1 ml whole blood using four-color flow cytometry (FCM). Circulating CD45^dimCD34⁺VEGFR2⁺7AAD⁻ progenitor cells were measured in progenitor-enriched fractions by four-color FCM. Plasma VEGF, sVEGFR2, SDF-1α and sVCAM-1 levels were determined by ELISA. Correlations between baseline CEC, CD45^dimCD34⁺VEGFR2⁺7AAD⁻ progenitor cells, plasma factors, as well as day 1–day 14 changes in CEC, CD45^dimCD34⁺VEGFR2⁺7AAD⁻ progenitor, plasma factor levels, and response to TKI, progression-free survival (PFS) and overall survival (OS) were examined.

Results:

No significant correlation between markers and response to TKI was observed. No association between baseline CEC, plasma VEGF, sVEGFR-2, SDF-1α, sVCAM-1 levels with PFS and OS was observed. However, baseline CD45^dimCD34⁺VEGFR2⁺7AAD⁻ progenitor cell levels were associated with PFS (P=0.01) and OS (P=0.006). Changes in this population and in SDF-1α levels between day 1 and day 14 were associated with PFS (P=0.03, P=0.002). Changes in VEGF and SDF-1α levels were associated with OS (P=0.02, P=0.007).

Conclusion:

Monitoring CD45^dimCD34⁺VEGFR2⁺ progenitor cells, plasma VEGF and SDF-1α levels could be of clinical interest in TKI-treated mRCC pts to predict outcome.

Phase I evaluation of telatinib, a VEGF receptor tyrosine kinase inhibitor, in combination with bevacizumab in subjects with advanced solid tumors

BACKGROUND

Blocking both receptor and ligand of the vascular endothelial growth factor (receptor) VEGF(R) pathway might be feasible and increase antitumor activity. This phase I study investigated telatinib, an oral tyrosine kinase inhibitor targeting VEGFR-2, combined with bevacizumab, in adults with solid tumors.

PATIENTS AND METHODS

Twenty-six patients were treated in successive cohorts with telatinib (twice-daily continuously, 450-900 mg) or bevacizumab (bi-weekly, starting dose 5 mg/kg). Safety, pharmacokinetics, endothelial (progenitor) cell (E(P)C)/growth factor kinetics and efficacy were assessed.

RESULTS

Most frequent adverse events were pain, nausea, voice changes and fatigue. Five dose-limiting toxicities (DLTs) occurred: hypertension (cohort I and II), bowel perforation, lipase increase and atrial flutter (cohort III). Cumulative toxicity resulted in a bevacizumab dose reduction to 1 mg/kg (cohort III). Due to three DLTs (n = 14), this cohort represented the best-tolerated dose level. Bevacizumab effectively neutralized plasma VEGF even at 1 mg/kg. Twelve patients had stable disease (clinical benefit 46%). EPC and SDF-1α levels increased during monotherapy telatinib.

CONCLUSIONS

Telatinib (450 mg b.i.d.) combined with bevacizumab (1 mg/kg bi-weekly) shows antitumor activity, but accumulating constitutional toxicity impedes long-term treatment of patients. Therefore, this combination will not be pursued in a phase II setting.

Antiangiogenic therapy: impact on invasion, disease progression, and metastasis

Antiangiogenic drugs targeting the VEGF pathway have slowed metastatic disease progression in some patients, leading to progression-free survival (PFS) and overall survival benefits compared with controls. However, the results are more modest than predicted by most preclinical testing and benefits in PFS are frequently not accompanied by overall survival improvements. Questions have emerged about the basis of drug resistance and the limitations of predictive preclinical models, and also about whether the nature of disease progression following antiangiogenic therapy is different to classic cytotoxic therapies-in particular whether therapy may lead to more invasive or metastatic behavior. In addition, because of recent clinical trial failures of antiangiogenic therapy in patients with early-stage disease, and the fact that there are hundreds of trials underway in perioperative neoadjuvant and adjuvant settings, there is now greater awareness about the lack of appropriate preclinical testing that preceded these studies. Improved preclinical assessment of all stages of metastatic disease should be a priority for future antiangiogenic drug discovery and development.

CXCL12 (SDF1alpha)-CXCR4/CXCR7 pathway inhibition: an emerging sensitizer for anticancer therapies?

Addition of multiple molecularly targeted agents to the existing armamentarium of chemotherapeutics and radiotherapies represents a significant advance in the management of several advanced cancers. In certain tumor types with no efficacious therapy options, these agents have become the first line of therapy, for example, sorafenib in advanced hepatocellular carcinoma or bevacizumab in recurrent glioblastoma. Unfortunately, in many cases, the survival benefits are modest, lasting only weeks to a few months. Moreover, they may not show benefit in patients with localized disease (i.e., in the adjuvant setting). Recent studies have provided increasing evidence that activation of the chemokine CXCL12 (SDF1α) pathway is a potential mechanism of tumor resistance to both conventional therapies and biological agents via multiple complementary actions: (i) by directly promoting cancer cell survival, invasion, and the cancer stem and/or tumor-initiating cell phenotype; (ii) by recruiting "distal stroma" (i.e., myeloid bone marrow-derived cells) to indirectly facilitate tumor recurrence and metastasis; and (iii) by promoting angiogenesis directly or in a paracrine manner. Here, we discuss recent preclinical and clinical data that support the potential use of anti-CXCL12 agents (e.g., AMD3100, NOX-A12, or CCX2066) as sensitizers to currently available therapies by targeting the CXCL12/CXCR4 and CXCL12/CXCR7 pathways.

Drug delivery strategies for therapeutic angiogenesis and antiangiogenesis

INTRODUCTION

Angiogenesis is essential to human biology and of great clinical significance. Excessive or reduced angiogenesis can result in, or exacerbate, several disease states, including tumor formation, exudative age-related macular degeneration (AMD) and ischemia. Innovative drug delivery systems can increase the effectiveness of therapies used to treat angiogenesis-related diseases.

AREAS COVERED

This paper reviews the basic biology of angiogenesis, including current knowledge about its disruption in diseases, with the focus on cancer and AMD. Anti- and proangiogenic drugs available for clinical use or in development are also discussed, as well as experimental drug delivery systems that can potentially improve these therapies to enhance or reduce angiogenesis in a more controlled manner.

EXPERT OPINION

Laboratory and clinical results have shown pro- or antiangiogenic drug delivery strategies to be effective in drastically slowing disease progression. Further research in this area will increase the efficacy, specificity and duration of these therapies. Future directions with composite drug delivery systems may make possible targeting of multiple factors for synergistic effects.

Placental growth factor upregulation is a host response to antiangiogenic therapy

PURPOSE

Placental growth factor (PlGF) is an angiogenic protein. Upregulation of PlGF has been observed in the clinic following antiangiogenic regimens targeting the VEGF pathway. PlGF has been proposed as a therapeutic target for oncology. sFLT01 is a novel fusion protein that neutralizes mouse and human PlGF (mPlGF, hPlGF) and mouse and human VEGF-A (mVEGF-A, hVEGF-A). It was tested in syngeneic and xenograft tumor models to evaluate the effects of simultaneously neutralizing PlGF and VEGF-A and to investigate changes observed in the clinic in preclinical models.

EXPERIMENTAL DESIGN

Production of PlGF and VEGF-A by B16F10 and A673 cancer cells in vitro was assessed. Mice with subcutaneous B16F10 melanoma or A673 sarcoma tumors were treated with sFLT01. Tumor volumes and microvessel density (MVD) were measured to assess efficacy. Serum levels of hVEGF-A, hPlGF, and mPlGF at early and late time points were determined by ELISA.

RESULTS

Exposure of cancer cell lines to sFLT01 caused a decrease in VEGF secretion. sFLT01 inhibited tumor growth, prolonged survival, and decreased MVD. Analysis of serum collected from treated mice showed that sFLT01 administration caused a marked increase in circulating mPlGF but not hPlGF or hVEGF. sFLT01 treatment also increased circulating mPlGF levels in non-tumor-bearing mice.

CONCLUSION

With the tumor cell lines and mouse models we used, antiangiogenic therapies that target both PlGF and VEGF may elicit a host response rather than, or in addition to, a malignant cell response that contribute to therapeutic resistance and tumor escape as suggested by others.

Angiogenesis in chronic liver disease and its complications

Nowadays, liver cancer, cirrhosis and other liver-related diseases are the fifth most common cause of mortality in the UK. Furthermore, chronic liver diseases (CLDs) are one of the major causes of death, which are still increasing year-on-year. Therefore, knowledge about the pathophysiology of CLDs and its complications is of uttermost importance. The goal of this review is to clarify the role of angiogenesis in the disease progression of various liver diseases. Looking closer at the pathophysiology of portal hypertension (PH), fibrosis, cirrhosis, non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC), we find that angiogenesis is a recurring factor in the disease progression. In PH, several factors involved in its pathogenesis, such as hypoxia, oxidative stress, inflammation and shear stress are potential mediators for the angiogenic response. The progression from fibrosis to cirrhosis, the end-point of CLDs, is distinguished by a prolonged inflammatory and fibrogenic process that leads to an abnormal angioarchitecture distinctive for cirrhosis. In several stages of NASH, a link might be made between the disease progression and hepatic microvasculature changes. HCC is one of the most vascular solid tumours in which angiogenesis plays an important role in its development, progression and metastasis. The close relationship between the progression of CLDs and angiogenesis emphasises the need for anti-angiogenic therapy as a tool for blocking or slowing down the disease progression. The fact that angiogenesis plays a pivotal role in CLDs gives rise to new opportunities for treating CLDs and its complications.

Effect of sorafenib on murine liver regeneration

Hepatocellular carcinoma (HCC) is a common cause of cancer-related death. Sorafenib prolongs survival of patients with advanced disease and is approved for the systemic treatment of unresectable HCC. It possesses antiangiogenic and antiproliferative properties by way of inhibition of the receptor tyrosine kinases vascular endothelial growth factor receptor 2 (VEGFR-2) and platelet-derived growth factor receptor-beta 1/2 (PDGFR-β) and the kinase RAF. Sorafenib represents a candidate compound for adjuvant therapy in HCC patients. The aim of our study was to investigate whether sorafenib affects liver regeneration. C57BL6 mice received sorafenib orally at 30 mg/kg/day or its vehicle either for 14 days until the day before hepatectomy or starting the day after surgery or both. Animals were sacrificed 24, 72, and 120 hours after hepatectomy. Liver regeneration was calculated as a percent of initial liver weight. Bromodeoxyuridine (BrdU) incorporation and phospho-extracellular signal-regulated kinase (pERK1/2) were determined by immunohistochemistry on liver sections. VEGF-A, PDGF-BB, and hepatocyte growth factor (HGF) levels were measured in liver tissue homogenates. Histological analysis of scar tissue was performed. Treatment stopped 1 day before surgery had no impact on liver regeneration. Continuous sorafenib treatment and treatment started 1 day after surgery had statistically significant effects on liver regeneration at 120 hours compared to vehicle-treated control animals (72% ± 12 versus control 88% ± 15 and 70% ± 13 versus control 86% ± 5 at 120 hours, both P ≤ 0.02). BrdU incorporation showed decreased numbers of positive nuclei in both groups receiving sorafenib after surgery. Phospho-ERK levels were reduced in sorafenib-treated animals. An increase of VEGF-A levels was observed in mice receiving sorafenib. Wound-healing complications were observed in animals receiving sorafenib after surgery and confirmed on histological sections.

CONCLUSION

This preclinical study shows that sorafenib did not impact on liver regeneration when ceased before surgery; however, administration after hepatectomy affected late liver regeneration.

Anti-angiogenic therapy: adapting strategies to overcome resistant tumors

Healthy cells, as well as benign and malignant tumors, depend upon the body's blood supply to bring in oxygen and nutrients and carry away waste products. Using this property against tumors, anti-angiogenic therapy targets the tumor vasculature with the aim of starving the tumor, and has demonstrated exceptional clinical efficacy against a number of tumors. This review discusses the current state of knowledge regarding anti-angiogenic therapies presently available to patients, and garners from both preclinical and clinical literature the benefits and side effects associated with anti-angiogenic therapies, the unfortunate mechanisms of acquired resistance to these novel therapeutics, and highlights promising next generation anti-angiogenics that may overcome the limitations encountered with first generation therapies.

Evaluation of KRAS mutations, angiogenic biomarkers, and DCE-MRI in patients with advanced non-small-cell lung cancer receiving sorafenib

PURPOSE

Sorafenib, a multikinase inhibitor targeting Raf and VEGFR, has shown activity in unselected patients with non-small-cell lung cancer (NSCLC). At present there are no validated biomarkers indicative of sorafenib activity.

EXPERIMENTAL DESIGN

Patients received sorafenib 400 mg BID daily to determine activity and tolerability and to measure its biological effects. KRAS mutation status (N = 34), angiogenesis markers (VEGF, bFGF, FLT-1, PLGF-1) and imaging with DCE-MRI (dynamic contrast enhanced MRI) to determine early changes in tumor vascular characteristics were evaluated. Three parameters K(trans), K(ep), and V(e) were measured by DCE-MRI at baseline and day 14 of cycle 1. Cytokine analysis was done on days 0, 14, 28, and 54.

RESULTS

Thirty-seven patients with previously treated stage IV NSCLC were enrolled in this single-center phase II trial. In 34 evaluable patients, 2 had partial responses and 20 had stable disease for 3 to 17 months, a disease control rate of 65%. The median progression-free survival (PFS) was 3.4 months, and median overall survival (OS) was 11.6 months. Toxicity was consistent with the known side effects of sorafenib. KRAS (32%) and EGFR mutations (22%) showed no correlation with response, PFS, or OS. K(ep), was significant in predicting an improvement in OS (P = 0.035) and PFS (P = 0.029). Cytokine analysis demonstrated an improved OS for bFGF day 0 (<6 vs. >6 pg/mL; P = 0.042), whereas a PFS benefit was seen with bFGF at day 28 (<6 vs. >6; P = 0.028).

CONCLUSIONS

KRAS and EGFR mutational status showed no correlation with response, PFS, or OS. Radiologic and cytokine changes may act as biomarkers indicative of early angiogenesis inhibition.

In pursuit of new anti-angiogenic therapies for cancer treatment

Despite advances in surgery, radiation therapy, and chemotherapy, patients with cancer have a poor prognosis. Sustained aberrant tumor angiogenesis and metastasis is a major obstacle for effective cancer treatment. Just a few years ago, few would argue that one of the key success stories of the modern cancer medicine were the anti-angiogenic drugs targeting the vascular endothelial growth factor (VEGF) signaling pathway approved by FDA. This initial success inspired many researchers to search for new anti-angiogenic targets and drugs with the hope that one day, anti-angiogenic therapy might really become the panacea for cancer patients. Unfortunately, the limited clinical benefits achieved with anti-angiogenic drugs conflicts with the widely accepted notion that angiogenesis is a key event in tumor progression. Emerging data indicate that unique characteristics of the tumor vasculature within the tumor microenvironment may hold the key for success of anti-angiogenic therapy. In particular, the molecular and cellular alterations that sustain aberrant tumor angiogenesis in the face of angiogenic inhibitors represents novel targets for rationally designing and improving current anti-angiogenic strategies.

Circulating endothelial cells are an early predictor in renal cell carcinoma for tumor response to sunitinib

BACKGROUND

Tyrosine kinase inhibitors (TKI) have enriched the therapeutic options in patients with renal cell carcinoma (RCC), which frequently induce morphological changes in tumors. However, only little is known about the biological activity of TKI. Circulating endothelial cells (CEC) have been associated with endothelial damage and, hence, may serve as a putative marker for the biological activity of TKI. The main objective of our study was to evaluate the predictive value of CEC, monocytes, and soluble vascular endothelial growth factor receptor (sVEGFR)-2 in RCC patients receiving sunitinib treatment.

METHODS

Analyses of CEC, monocytes, and sVEGFR-2 were accomplished for twenty-six consecutive patients with metastatic RCC who received treatment with sunitinib (50 mg, 4 wks on 2 wks off schedule) at our institution in 2005 and 2006.

RESULTS

In RCC patients CEC are elevated to 49 ± 44/ml (control 8 ± 8/ml; P = 0.0001). Treatment with sunitinib is associated with an increase in CEC within 28 days of treatment in patients with a Progression free survival (PFS) above the median to 111 ± 61 (P = 0.0109), whereas changes in patients with a PFS below the median remain insignificant 69 ± 61/ml (P = 0.1848). Monocytes and sVEGFR2 are frequently altered upon sunitinib treatment, but fail to correlate with clinical response, defined by PFS above or below the median.

CONCLUSIONS

Sunitinib treatment is associated with an early increase of CEC in responding patients, suggesting superior endothelial cell damage in these patients as a putative predictive biomarker.

C-X-C receptor type 4 promotes metastasis by activating p38 mitogen-activated protein kinase in myeloid differentiation antigen (Gr-1)-positive cells

Increasing evidence suggests that myeloid bone marrow-derived cells (BMDCs) play a critical role in lung metastasis. Blockade of VEGF receptor 1 (VEGFR1) has been proposed as a potential strategy to limit myeloid BMDC recruitment to tumors. However, preclinical evidence indicates that this strategy may not be effective in all tumors. Thus, establishing which molecular mechanisms are responsible for the "escape" of these BMDCs from VEGFR1 inhibition would facilitate development of strategies to control metastasis. Here, we report the complementary role of the chemokine (C-X-C motif) ligand 12/C-X-C chemokine receptor 4 (CXCR4) and VEGF/VEGFR1 pathways in promoting lung metastasis in mice via BMDC recruitment using chimeric mice with deficiency in CXCR4 and VEGFR1-tyrosine kinase in the BMDCs. We first demonstrate that CXCR4 activity is essential for recruitment of myeloid differentiation antigen (Gr-1)-positive BMDCs, whereas VEGFR1 activity is responsible for macrophage recruitment in established tumors. Inhibition of both VEGFR1 and CXCR4 signaling in myeloid BMDCs exerted greater effects on tumor vascular density, growth, and lung metastasis than inhibition of VEGFR1 alone. These effects were reproduced after pharmacologic inhibition of CXCR4 with AMD3100. VEGFR1 and CXCR4 independently exerted a promigratory effect in myeloid BMDCs by activating p38 mitogen-activating protein kinase. Thus, combining CXCR4 blockade with inhibition of VEGFR1 may induce greater tumor growth delay and prevent or inhibit metastasis.

VEGF-PET imaging is a noninvasive biomarker showing differential changes in the tumor during sunitinib treatment

Non-invasive imaging of angiogenesis could ease the optimization of antiangiogenesis treatments for cancer. In this study, we evaluated the role of VEGF-PET as a biomarker of dynamic angiogenic changes in tumors following treatment with the kinase inhibitor sunitinib. The effects of sunitinib treatment and withdrawal on the tumor was investigated using the new VEGF-PET tracer (89)Zr-ranibizumab as well as (18)F-FDG PET, and (15)O-water PET in mouse xenograft models of human cancer. The obtained imaging results were compared with tumor growth, VEGF plasma levels and immunohistologic analyzes. In contrast to (18)F-FDG and (15)O-water PET, VEGF-PET demonstrated dynamic changes during sunitinib treatment within the tumor with a strong decline in signal in the tumor center and only minimal reduction in tumor rim, with a pronounced rebound after sunitinib discontinuation. VEGF-PET results corresponded with tumor growth and immunohistochemical vascular- and tumor- markers. Our findings highlight the strengths of VEGF-PET imaging to allow serial analysis of angiogenic changes in different areas within a tumor.

Progression of intramedullary metastasis during perioperative cessation of sunitinib

BACKGROUND

A 57-year-old woman presented with metastatic renal cell carcinoma (RCC). She was enrolled in a clinical study, in which she received two cycles of neoadjuvant sunitinib therapy followed by cytoreductive nephrectomy. Her primary tumor and rib metastasis showed a good response to neoadjuvant therapy; however, after surgery, the patient developed neurologic symptoms, including flaccid paraparesis with paresthesia and hypoesthesia. MRI of the brain and spine revealed a leptomeningeal lesion at the T12-L1 space, which was presumed to have progressed during the 3-week treatment-free perioperative period. The patient underwent radiation therapy for the intramedullary lesion 1 month later, and sunitinib therapy was subsequently reinstated. After 6 months, her extracranial lesions remained stable and the intramedullary lesion was undetectable on MRI.

INVESTIGATIONS

CT of the chest and abdomen, bone scan, kidney and liver function tests, measurement of serum levels of calcium, electrolytes and lactate dehydrogenase, CBC, MRI of the brain and spine.

DIAGNOSIS

Progression of a central nervous system metastasis linked to the interruption of neoadjuvant sunitinib therapy.

MANAGEMENT

Neoadjuvant sunitinib therapy followed by cytoreductive nephrectomy for the primary RCC; radiation therapy for the intramedullary lesion, followed by reinstatement of sunitinib therapy owing to a good clinical response observed in the extracranial lesions.

Vascular endothelial growth factor as an anti-angiogenic target for cancer therapy

New blood vessel formation (angiogenesis) is fundamental to tumor growth, invasion, and metastatic dissemination. The vascular endothelial growth factor (VEGF) signaling pathway plays pivotal roles in regulating tumor angiogenesis. VEGF as a therapeutic target has been validated in various types of human cancers. Different agents including antibodies, aptamers, peptides, and small molecules have been extensively investigated to block VEGF and its pro-angiogenic functions. Some of these agents have been approved by FDA and some are currently in clinical trials. Combination therapies are also being pursued for better tumor control. By providing comprehensive real-time information, molecular imaging of VEGF pathway may accelerate the drug development process. Moreover, the imaging will be of great help for patient stratification and therapeutic effect monitoring, which will promote effective personalized molecular cancer therapy. This review summarizes the current status of tumor therapeutic agents targeting to VEGF and the applications of VEGF related molecular imaging.

Phase II study of metronomic chemotherapy with bevacizumab for recurrent glioblastoma after progression on bevacizumab therapy

We evaluated the efficacy of metronomic etoposide or temozolomide administered with bevacizumab among recurrent glioblastoma (GBM) patients who progressed on prior bevacizumab therapy in a phase 2, open-label, two-arm trial. Twenty-three patients received bevacizumab (10 mg/kg) every 2 weeks with either oral etoposide (50 mg/m2) daily for 21 consecutive days each month or daily temozolomide (50 mg/m2). The primary endpoint was 6-month progression-free survival (PFS-6) and secondary endpoints included safety and overall survival. Both the etoposide and temozolomide arms of the study closed at the interim analysis due to lack of adequate anti-tumor activity. No radiographic responses were observed. Although 12 patients (52%) achieved stable disease, PFS-6 was 4.4% and the median PFS was 7.3 weeks. The only grade 4 adverse event was reversible neutropenia. Grade 3 toxicities included fatigue (n = 2) and infection (n = 1). Metronomic etoposide or temozolomide is ineffective when administered with bevacizumab among recurrent GBM patients who have progressed on prior bevacizumab therapy. Alternative treatment strategies remain critically needed for this indication.

Investigational EGFR-targeted therapy in head and neck squamous cell carcinoma

IMPORTANCE OF THE FIELD

EGFR is an established therapeutic target in head and neck squamous cell carcinoma (HNSCC). The EGFR-targeting monoclonal antibody cetuximab (Erbitux, Imclone Systems, Inc., Branchburg, USA) was FDA-approved for use in HNSCC in 2006. The molecular basis for the efficacy of an antibody approach compared with inhibition of EGFR tyrosine kinase function using small-molecule inhibitors, or downregulation of protein expression via antisense strategies, remains incompletely understood.

AREAS COVERED IN THIS REVIEW

A literature search was performed to identify studies elucidating mechanisms of action of several approaches to targeting EGFR in HNSCC (monoclonal antibodies, tyrosine kinase inhibitors, antisense approaches, and ligand-toxin conjugates).

WHAT THE READER WILL GAIN

Monoclonal antibodies decrease tumor growth via receptor endocytosis and recruitment of host immune defenses. Tyrosine kinase inhibitors bind to the ATP binding pocket of the tyrosine kinase domain, inhibiting signaling. Antisense approaches decrease EGFR expression with high specificity, though drug delivery remains problematic. Ligand-toxin conjugates facilitate the entry of toxin and the ADP-ribosylation of the ribosome, thereby inhibiting translation.

TAKE HOME MESSAGE

Elucidation mechanisms by which these different strategies inhibit EGFR function may enhance the development of more effective treatments for HNSCC and enable prospective identification of individuals who will benefit from EGFR inhibition.

Off-tumor target--beneficial site for antiangiogenic cancer therapy?

Antiangiogenic cancer therapy is based on agents that target blood vessels of the tumor to inhibit its growth. However, experience from the clinic demonstrates that survival benefits following antiangiogenic therapy do not always correlate with tumor size and growth inhibition. Emerging evidence shows that delivery of antiangiogenic drugs might induce systemic alterations of the vasculature that modulate the function of various tissues and organs. Normalization of tissues and organs by antiangiogenic therapy may be an important mechanism underlying the survival benefits seen in patients with cancer who suffer cancer-associated systemic syndromes. This new concept has been validated in preclinical tumor models, and responses in patients have positively correlated with clinical benefits.

Biomarkers predicting outcome in patients with advanced renal cell carcinoma: Results from sorafenib phase III Treatment Approaches in Renal Cancer Global Evaluation Trial

PURPOSE

Plasma proteins [vascular endothelial growth factor (VEGF), soluble VEGF receptor 2 (sVEGFR-2), carbonic anhydrase IX (CAIX), tissue inhibitor of metalloproteinase 1 (TIMP-1), and Ras p21] and one tumor gene (VHL) were analyzed to identify prognostic biomarkers or indicators of response to sorafenib in a subset of patients enrolled in the Treatment Approaches in Renal Cancer Global Evaluation Trial.

EXPERIMENTAL DESIGN

Nine hundred three patients with advanced renal cell carcinoma (RCC) were randomized to 400 mg sorafenib twice a day or placebo. Samples collected at baseline and after 3 and 12 weeks were subjected to enzyme-linked immunosorbent assays. VHL exons were sequenced from tumor biopsies.

RESULTS

Baseline biomarker data were available for VEGF (n = 712), sVEGFR-2 (n = 713), CAIX (n = 128), TIMP-1 (n = 123), Ras p21 (n = 125), and VHL mutational status (n = 134). Higher Eastern Cooperative Oncology Group performance status (ECOG PS) score correlated with elevated baseline VEGF (P < 0.0001) and a higher incidence of VHL mutations (P = 0.008), whereas higher Memorial Sloan-Kettering Cancer Center (MSKCC) score correlated with elevated VEGF (P < 0.0001), CAIX (P = 0.027), and TIMP-1 (P = 0.0001). Univariable analyses of baseline levels in the placebo cohort identified VEGF (P = 0.0024), CAIX (P = 0.034), TIMP-1 (P = 0.001), and Ras p21 (P = 0.016) as prognostic biomarkers for survival. TIMP-1 remained prognostic for survival in a multivariable analysis model (P = 0.002) that also included ECOG PS, MSKCC score, and the other biomarkers assayed. In the placebo cohort, TIMP-1 (P < 0.001) and Ras p21 (P = 0.048) levels increased at 12 weeks. In the sorafenib cohort, VEGF levels increased at 3 and 12 weeks of treatment (both weeks P < 0.0001), whereas sVEGFR-2 (both weeks P < 0.0001) and TIMP-1 levels (P = 0.002, week 3; P = 0.006, week 12) decreased.

CONCLUSIONS

VEGF, CAIX, TIMP-1, and Ras p21 levels were prognostic for survival in RCC patients. Of these, TIMP-1 has emerged as being independently prognostic.

Vascular endothelial growth factor polymorphisms: role in response and toxicity of tyrosine kinase inhibitors

Angiogenesis is central to the growth of normal tissues and tumors. Inhibiting this pathway has been a strategy for drug development for tumors not responsive to most agents used in chemotherapy. Notably, signaling mediated by vascular endothelial growth factor (VEGF) is a key target because aberrant signaling via this pathway is frequently associated with neoangiogenesis in tumors. The drug-discovery effort to blunt VEGF signaling has led to the approval of bevacizumab and several receptor tyrosine kinase inhibitors (TKIs) that have shown efficacy in the clinical management of breast, colorectal, lung, and kidney cancer. Understanding the genetic variability in VEGF and VEGF receptor has led to identifying genotypic variations (single nucleotide polymorphisms [SNPs]) associated with treatment outcome and toxicity. Notably, identification of SNPs in VEGF associated with angiogenesis inhibitor treatment-induced hypertension and outcome provides exciting opportunities for personalized medicine to improve outcome and reduced toxicity with these novel TKIs.

Tumor-host interactions: a far-reaching relationship

Carcinomas are composed of neoplastic epithelial cells, which form the heart of the tumor, as well as a variety of mesenchymal cell types and extracellular matrix components that comprise the tumor stroma, often termed its microenvironment. The normal counterparts of some stromal cells are thought to limit tumor growth, while tumor-associated stromal cells have been convincingly shown to actively promote tumor progression via complex heterotypic interactions with the nearby carcinoma cells. More recent advances have revealed that tumor-host interactions extend well beyond the local tissue microenvironment (ie, interactions between the neoplastic cells and the nearby stroma) and that tumors not only respond to, but actively perturb host organs at distant anatomic sites. This indicates that many aspects of tumor biology can only be explained by a detailed understanding of both local and systemic interactions, yet we currently have only a fragmentary understanding of both processes. In this review, we address the recent advances in our understanding of the contributions of local and systemic environments to cancer progression, the ability of tumors to actively perturb the host environment, and current therapeutic approaches that are designed to disrupt tumor-host relationships.

Optimizing the delivery of cancer drugs that block angiogenesis

Drugs that block angiogenesis are important components of first-line therapies for a number of human cancers. However, some of these agents have undesirable effects on the patient. Optimal delivery systems must be developed to maximize clinical benefits and minimize adverse effects in cancer patients. In this Perspective, we discuss these drug-related issues and propose ways to optimize antiangiogenic therapy by the development of new drug delivery systems.

A decrease in maternal plasma concentrations of sVEGFR-2 precedes the clinical diagnosis of preeclampsia

OBJECTIVE

The aim of this study was to examine if maternal plasma concentrations of soluble vascular endothelial growth factor receptor (sVEGFR)-2 change prior to the diagnosis of preeclampsia.

STUDY DESIGN

A longitudinal study was conducted in normal pregnant women (n = 160) and patients with preeclampsia (n = 40). Blood samples were collected at 7 gestational age intervals from 6 weeks to term. Plasma concentrations of sVEGFR-2 were determined by enzyme-linked immunosorbent assay. Analysis was performed with cross-sectional and longitudinal (mixed effects model) approaches.

RESULTS

Mothers destined to develop preeclampsia have lower plasma sVEGFR-2 concentrations than those who will have a normal pregnancy (longitudinal approach; P < .05). Cross-sectional analysis suggested that the median plasma sVEGFR-2 concentration in women destined to develop preeclampsia was significantly lower than that in normal pregnant women from 28-31 weeks of gestation (P = .001) or 6-10 weeks prior to the diagnosis (P < .001).

CONCLUSION

A lower maternal plasma sVEGFR-2 concentration precedes the development of preeclampsia, both term and preterm.

SABRE-B: an evaluation of paclitaxel and bevacizumab with or without sunitinib as first-line treatment of metastatic breast cancer

BACKGROUND

The vascular endothelial growth factor (VEGF) pathway can be targeted through VEGF neutralization or VEGF receptor (VEGFR) blockade using tyrosine kinase inhibition. Because laboratory models suggest that combining these approaches might be synergistic, we sought to evaluate the feasibility and efficacy of combining sunitinib with paclitaxel + bevacizumab (PB).

METHODS

Patients with human epidermal growth factor receptor 2 (HER2)-negative, metastatic breast cancer receiving first-line chemotherapy were randomized to PB or PB with sunitinib (PBS), with planned escalation of the sunitinib dose.

RESULTS

Forty-six patients were randomized to PB or PBS with sunitinib dosed at 25 mg p.o. daily. Patients receiving PBS encountered substantial toxicity that precluded adequate treatment. The percentage of patients with grade ≥3 adverse events was greater in the PBS arm than the PB arm (83% versus 57%), and sunitinib dosing was modified in 78% of patients, most often due to neutropenia, febrile neutropenia, and fatigue. In addition, 44% of patients had sunitinib dose reduction to 12.5 mg, and 39% required discontinuation. Patients receiving PBS had more bevacizumab treatment interruptions and discontinuations because of toxicity. Median treatment duration was longer in the PB arm compared with the PBS arm (14.1 versus 11.1 weeks), reflecting early treatment discontinuation of PBS. Because of poor tolerability of the addition of sunitinib to PB, the planned sunitinib dose escalation was halted and the study accrual was terminated.

CONCLUSION

Adding sunitinib to standard doses of bevacizumab plus paclitaxel for metastatic breast cancer is not feasible. Different strategies will be required to evaluate whether there is additional clinical benefit to combining VEGF/VEGFR-targeted agents.

mTOR inhibition by everolimus counteracts VEGF induction by sunitinib and improves anti-tumor activity against gastric cancer in vivo

VEGF receptor blockage has been reported to increase serum VEGF. We hypothesized that mTOR inhibition by everolimus counteracts VEGF induction by sunitinib resulting in an improved anti-tumor activity of sunitinib. In vitro, sunitinib in combination with everolimus did not outperform the respective monotherapies. In vivo, monotherapies reduced tumor growth by 60%, whereas the combination of sunitinib and everolimus led to an almost complete tumor growth inhibition. This superior anti-tumor activity coincided with attenuation of VEGF peaks. In conclusion mTOR inhibition by everolimus counteracts VEGF induction by sunitinib and results in significant reduction of tumor burden and long-lasting tumor growth control.

Mechanisms of resistance to antiangiogenesis therapy

Angiogenesis, the formation of new blood vessels from existing vasculature, plays an essential role in tumour growth, invasion and metastasis. Vascular endothelial growth factor (VEGF) is one of the key factors responsible for its regulation. High expression of VEGF has been observed in many cancers, and is associated with worse survival. When antiangiogenic agents are used alone they typically initially cause reduction in blood flow or vascular permeability, in many types of cancer. In some cases tumour regression occurs, mainly in renal cancer. In combination with chemotherapy, progression-free survival is often prolonged, but overall survival is not. Many tumours fail to respond initially - de novo resistance. Others develop resistance over time, with progression after a few months of treatment. The mechanisms of resistance are not well understood. The theoretical benefits of VEGF inhibitors are more likely to be realised by understanding these mechanisms and modifying therapy accordingly. This article reviews current knowledge on resistance mechanisms and the therapeutic implications.

Direct and differential suppression of myeloid-derived suppressor cell subsets by sunitinib is compartmentally constrained

The antiangiogenic drug sunitinib is a receptor tyrosine kinase inhibitor with significant, yet not curative, therapeutic effects in metastatic renal cell carcinoma (RCC). Sunitinib is also an immunomodulator, potently reversing myeloid-derived suppressor cell (MDSC) accumulation and T-cell inhibition in the blood even of nonresponder RCC patients. We observed that sunitinib similarly prevented MDSC accumulation and restored normal T-cell function to the spleens of tumor-bearing mice, independent of the capacity of sunitinib to inhibit tumor progression (RENCA>CT26>4T1). Both monocytic and neutrophilic splenic MDSC were highly repressible by sunitinib. In contrast, MDSC within the microenvironment of 4T1 tumors or human RCC tumors proved highly resistant to sunitinib and ambient T-cell function remained suppressed. Proteomic analyses comparing tumor to peripheral compartments showed that granulocyte macrophage colony-stimulating factor (GM-CSF) predicted sunitinib resistance and recombinant GM-CSF conferred sunitinib resistance to MDSC in vivo and in vitro. MDSC conditioning with GM-CSF uniquely inhibited signal transducers and activators of transcription (STAT3) and promoted STAT5 activation. STAT5ab(null/null) MDSC were rendered sensitive to sunitinib in the presence of GM-CSF in vitro. We conclude that compartment-dependent GM-CSF exposure in resistant tumors may account for the regionalized effect of sunitinib upon host MDSC modulation and hypothesize that ancillary strategies to decrease such regionalized escape will enhance the potency of sunitinib as an immunomodulator and a cancer therapy.

Issues regarding improving the impact of antiangiogenic drugs for the treatment of breast cancer

One of the major recent clinical advances in cancer treatment is the use of antiangiogenic drugs such as bevacizumab, sorafenib, and sunitinib. Bevacizumab, the monoclonal anti-VEGF antibody, has been approved for the first line treatment of metastatic breast cancer (MBC) when combined with taxane. However, the clinical benefits are modest; despite a doubling of response rates and significant prolongation of progression free survival times, no increase in overall survival is attained. This review summarizes some of the possibilities to account for this discrepant result. These include rapid development of acquired drug resistance due to the redundancy of proangiogenic growth factors, acceleration of tumor growth after antiangiogenic drug treatments are stopped, and increases in tumor cell malignant aggressiveness driven by mechanisms such as increased tumor hypoxia. Some possible strategies to improve the benefits of antiangiogenic drug therapy are discussed such as prolonging the treatment beyond tumor progression, combination with other therapeutic modalities, e.g. long term ('maintenance') low-dose metronomic chemotherapy or additional targeted/biologic drugs, e.g. trastuzumab.

Pharmacokinetic/pharmacodynamic modeling of biomarker response to sunitinib in healthy volunteers

A pharmacokinetic/pharmacodynamic (PK/PD) study of the tyrosine kinase inhibitor sunitinib was conducted in 12 healthy volunteers using blood pressure and circulating biomarker levels as PD markers. Blood pressure was measured, and plasma concentration-time courses of sunitinib, its major metabolite SU12662, vascular endothelial growth factors VEGF-A and VEGF-C, and soluble VEGF receptor-2 (sVEGFR-2) were studied in healthy subjects receiving 50 mg of sunitinib orally for 3-5 consecutive days. Using NONMEM, PK/PD models were established that predicted changes (expressed as multiples relative to baseline values) in systolic blood pressure, diastolic blood pressure, VEGF-A level, and sVEGFR-2 level, of 1.10, 1.18, 2.24, and 0.76, respectively, for a typical subject after 4 weeks of treatment with 50 mg/day. Simulated blood pressure-time courses compare excellently with published data in patients, whereas changes in circulating biomarkers were greater in patients than simulations suggest for healthy subjects. In conclusion, the tumor-independent pharmacological response to sunitinib could be described by PK/PD models, thereby facilitating model-based investigations with antiangiogenic drugs, using blood pressure and circulating proteins as biomarkers.

Compensatory activation of Akt in response to mTOR and Raf inhibitors - a rationale for dual-targeted therapy approaches in neuroendocrine tumor disease

Several studies have established a link between aberrant PI(3)K-Akt-mTOR- and Ras-Raf-MEK-Erk1/2 signaling and neuroendocrine tumor disease. In this study, we comparatively investigate the antitumor potential of novel small-molecule inhibitors targeting mTOR (RAD001), mTOR/PI(3)K (NVP-BEZ235) and Raf (Raf265) on human NET cell lines of heterogeneous origin. All inhibitors induced potent antitumor effects which involved the induction of apoptosis and G0/G1 arrest. However, the dual mTOR/PI(3)K inhibitor NVP-BEZ235 was more efficient compared to the single mTOR inhibitor RAD001. Consistently, NVP-BEZ235 prevented the negative feedback activation of Akt as observed after treatment with RAD001. Raf265 inhibited Erk1/2 phosphorylation but strongly induced Akt phosphorylation and VEGF secretion, suggesting the existence of a compensatory feedback loop on PI3K-Akt signaling. Finally, combined treatment with RAD001 or NVP-BEZ235 and Raf265 was more efficient than single treatment with either kinase inhibitor. Together, our data provide a rationale for dual targeting of PI(3)K-Akt-mTOR- and Ras-Raf-MEK-Erk1/2 signaling in NET disease.

Tumor and stromal pathways mediating refractoriness/resistance to anti-angiogenic therapies

Identification and characterization of VEGF as an important regulator of angiogenesis, and FDA approval of the first anti-angiogenic drugs, has enabled significant advances in the therapy of cancer and neovascular age-related macular degeneration. However, similar to other therapies, inherent/acquired resistance to anti-angiogenic drugs may occur in patients, leading to disease recurrence. Recent studies in several experimental models suggest that tumor and non-tumor (stromal) cell types may be involved in the reduced responsiveness to the treatments. The present review examines the role of tumor- as well as stromal cell-derived pathways involved in tumor growth and in refractoriness to anti-VEGF therapies.

Phase I evaluation of telatinib, a vascular endothelial growth factor receptor tyrosine kinase inhibitor, in combination with irinotecan and capecitabine in patients with advanced solid tumors

PURPOSE

We studied the safety and tolerability of telatinib, an orally available, small-molecule tyrosine kinase inhibitor of the vascular endothelial growth factor receptor (VEGFR-2/VEGFR-3), platelet-derived growth factor receptor beta, and c-Kit in combination with capecitabine and irinotecan.

EXPERIMENTAL DESIGN

Telatinib twice daily continuously, irinotecan once every 3 weeks, and capecitabine oral twice daily on day 1 to 14 were administered in cycles of 21 days in escalating doses in successive cohorts. Toxicity was evaluated to conform to the Common Terminology Criteria for Adverse Events version 3.0. Pharmacokinetic and (circulating) endothelial (progenitor) cell measurements were done. Tumor efficacy was evaluated using the Response Evaluation Criteria in Solid Tumors.

RESULTS

Twenty-three patients were included in this phase I trial. Most frequently (>25%) reported adverse events of any grade were vomiting, nausea, fatigue, diarrhea, alopecia, and hand-foot syndrome. A silent myocardial infarction and two cases of decreased left ventricular ejection fraction were reported; both were reversible. Cardiac monitoring of the subsequent patients did not reveal other abnormalities. The study was terminated when the recommended single agent phase II doses of telatinib (900 mg twice daily) and capecitabine/irinotecan was reached. Pharmacokinetic profiles showed no clinically relevant changes upon coadministration of the three drugs. (Circulating) endothelial (progenitor) cell levels stabilized during treatment. Five of 23 patients had partial remission and 9 of 23 patients showed stable disease.

CONCLUSIONS

Continuous administration of 900 mg telatinib twice daily can be safely combined with irinotecan (180 mg/m(2)) and capecitabine (1,000 mg/m(2) twice daily, day 1-14) and is the recommended schedule for further phase II studies. Tumor shrinkage and disease stabilization was observed. Cardiac toxicity needs further investigation in following studies.

Pharmacologic modulation of niche accessibility via tyrosine kinase inhibition enhances marrow and thymic engraftment after hematopoietic stem cell transplantation

Essential survival signals within hematopoietic stem cell (HSC) and thymic niches are mediated by receptor tyrosine kinases, which can be reversibly inhibited using clinically available drugs. We studied whether sunitinib, a multityrosine kinase inhibitor that inhibits KIT, enhances engraftment after bone marrow transplantation (BMT) in mice. Sunitinib diminished hematopoietic progenitor cell numbers, and sunitinib enhanced marrow, peripheral myeloid, and lymphoid engraftment after BMT in Rag1(-/-) mice. Sunitinib augmented HSC engraftment because recipients displayed increased myeloid and lymphoid engraftment and because sunitinib-treated recipients of purified HSCs showed enhanced engraftment of secondary hosts. However, sunitinib preferentially augmented T-cell engraftment with lesser effects on myeloid and HSC engraftment. Consistent with this, sunitinib preferentially depleted the early thymic progenitor subset in the thymus. Sunitinib did not increase engraftment in mice with deficient KIT signaling, and the pattern of more potent effects on T cell compared with HSC engraftment observed in sunitinib-treated hosts was also observed after BMT into KIT(W/Wv) mice. These results implicate KIT as a critical modulator of thymic niches. We conclude that transient, pharmacologic inhibition of KIT enhances accessibility of marrow and thymic niches, and provides a novel, noncytotoxic approach to accomplish engraftment after stem cell transplantation.

Plasma cytokine and angiogenic factor profiling identifies markers associated with tumor shrinkage in early-stage non-small cell lung cancer patients treated with pazopanib

There is an unmet need for pharmacodynamic and predictive biomarkers for antiangiogenic agents. Recent studies have shown that soluble vascular endothelial growth factor receptor 2 (sVEGFR2), VEGF, and several other soluble factors may be modulated by VEGF pathway inhibitors. We conducted a broad profiling of cytokine and angiogenic factors (CAF) to investigate the relationship between baseline CAF levels, CAF changes during treatment, and tumor shrinkage in early-stage non-small cell lung cancer (NSCLC) patients treated with pazopanib, an oral angiogenesis inhibitor targeting VEGFR, platelet-derived growth factor receptor, and c-kit. Plasma samples were collected before treatment and on the last day of therapy from 33 patients with early-stage NSCLC participating in a single-arm phase II trial. Levels of 31 CAFs were measured by suspension bead multiplex assays or ELISA and correlated with change in tumor volume. Pazopanib therapy was associated with significant changes of eight CAFs; sVEGFR2 showed the largest decrease, whereas placental growth factor underwent the largest increase. Increases were also observed in stromal cell-derived factor-1alpha, IP-10, cutaneous T-cell-attracting chemokine, monokine induced by IFN-gamma, tumor necrosis factor-related apoptosis-inducing ligand, and IFN-alpha. Posttreatment changes in plasma sVEGFR2 and interleukin (IL)-4 significantly correlated with tumor shrinkage. Baseline levels of 11 CAFs significantly correlated with tumor shrinkage, with IL-12 showing the strongest association. Using multivariate classification, a baseline CAF signature consisting of hepatocyte growth factor and IL-12 was associated with tumor response to pazopanib and identified responding patients with 81% accuracy. These data suggest that CAF profiling may be useful for identifying patients likely to benefit from pazopanib, and merit further investigation in clinical trials.

Molecular mechanisms of resistance to tumour anti-angiogenic strategies

Tumour angiogenesis, described by Folkman in the early seventies, is an essential, complex, and dynamic process necessary for the growth of all solid tumours. Among the angiogenic factors secreted by the tumour cells, the Vascular Endothelial Growth Factor (VEGF) is one of the most important. Most types of human cancer cells express elevated levels of this proangiogenic factor and its receptors. New molecules, called anti-angiogenic, are developed to impair VEGF pathway and tumour vasculature. Despite important results, the clinical benefits of anti-VEGF therapy are relatively modest and usually measured in weeks or months. Why following anti-angiogenic therapy do some patients respond transiently and then why does tumour grow again and disease progress and which compensatory mechanisms could explain the anti-angiogenic treatment failure?

Angiogenesis: What can it offer for future medicine?

Modulation of angiogenesis for disease therapy was proposed nearly 40 years ago and today various protein and chemical molecules are available for the treatment of human malignant and ophthalmological disorders. Angiogenesis research has emerged, as one of the most comprehensive research areas, in biomedicine and development of novel drugs by targeting angiogenesis has become one of the main focuses among pharmaceutical giants. If 30% of annually 12 million new cancer cases worldwide receive antiangiogenic therapy, over 60 million cancer patients would be treated by the end of 2060. In this mini-review, I discuss current available antiangiogenic drugs and future therapeutic options based on the angiogenesis principle.