Translating preclinical findings of (endothelial) progenitor cell mobilization into the clinic; from bedside to bench and back

Chemotherapy-induced metastasis: mechanisms and translational opportunities

Tumors often overcome the cytotoxic effects of chemotherapy through either acquired or environment-mediated drug resistance. In addition, signals from the microenvironment obfuscate the beneficial effects of chemotherapy and may facilitate progression and metastatic dissemination. Seminal mediators in chemotherapy-induced metastasis appear to be a wide range of hematopoietic, mesenchymal and immune progenitor cells, originating from the bone marrow. The actual purpose of these cells is to orchestrate the repair response to the cytotoxic damage of chemotherapy. However, these repair responses are exploited by tumor cells at every step of the metastatic cascade, ranging from tumor cell invasion, intravasation and hematogenous dissemination to extravasation and effective colonization at the metastatic site. A better understanding of the mechanistic underpinnings of chemotherapy-induced metastasis will allow us to better predict which patients are more likely to exhibit pro-metastatic responses to chemotherapy and will help develop new therapeutic strategies to neutralize chemotherapy-driven prometastatic changes.

Preoperative therapy with pazopanib in high-risk soft tissue sarcoma: a phase II window-of-opportunity study by the German Interdisciplinary Sarcoma Group (GISG-04/NOPASS)

INTRODUCTION

For resectable soft tissue sarcoma (STS), radical surgery, usually combined with radiotherapy, is the mainstay of treatment and the only potentially curative modality. Since surgery is often complicated by large tumour size and extensive tumour vasculature, preoperative treatment strategies with the aim of devitalising the tumour are being explored. One option is treatment with antiangiogenic drugs. The multikinase inhibitor pazopanib, which possesses pronounced antiangiogenic effects, has shown activity in metastatic and unresectable STS, but has so far not been tested in the preoperative setting.

METHODS AND ANALYSIS

This open-label, multicentre phase II window-of-opportunity trial assesses pazopanib as preoperative treatment of resectable STS. Participants receive a 21-day course of pazopanib 800 mg daily during wait time for surgery. Major eligibility criteria are resectable, high-risk adult STS of any location, or metachronous solitary STS metastasis for which resection is planned, and adequate organ function and performance status. The trial uses an exact single-stage design. The primary end point is metabolic response rate (MRR), that is, the proportion of patients with >50% reduction of the mean standardised uptake value (SUVmean) in post-treatment compared to pre-treatment fluorodeoxyglucose positron emission tomography CT. The MRR below which the treatment is considered ineffective is 0.2. The MRR above which the treatment warrants further exploration is 0.4. With a type I error of 5% and a power of 80%, the sample size is 35 evaluable patients, with 12 or more responders as threshold. Main secondary end points are histopathological and MRI response, resectability, toxicity, recurrence-free and overall survival. In a translational substudy, endothelial progenitor cells and vascular epithelial growth factor receptor are analysed as potential prognostic and predictive markers.

ETHICS AND DISSEMINATION

Approval by the ethics committee II, University of Heidelberg, Germany (2012-019F-MA), German Federal Institute for Drugs and Medical Devices (61-3910-4038155) and German Federal Institute for Radiation Protection (Z5-22463/2-2012-007).

TRIAL REGISTRATION NUMBER

NCT01543802, EudraCT: 2011-003745-18; Pre-results.

Incremental increase in VEGFR1⁺ hematopoietic progenitor cells and VEGFR2⁺ endothelial progenitor cells predicts relapse and lack of tumor response in breast cancer patients

Animal models have demonstrated the critical role of bone marrow-derived VEGFR1(+) hematopoietic progenitor cells (HPCs) and VEGFR2(+) endothelial progenitor cells (EPCs) in metastatic progression. We explored whether these cells could predict relapse and response in breast cancer (BC) patients. One hundred and thirty-two patients with stages 1-4 BC were enrolled on 2 studies. Circulating CD45(+)/CD34(+)/VEGFR1(+) HPCs and CD45(dim)/CD133(+)/VEGFR2(+) EPCs were assessed from peripheral blood mononuclear cells using flow cytometry. Changes in HPCs and EPCs were analyzed in (1) patients without overt disease that relapsed and (2) metastatic patients according to response by RECIST. At study entry, 102 patients were without evidence of disease and 30 patients had metastatic BC. Seven patients without evidence of BC by exam, labs, and imaging developed recurrence while on study. Median HPC/ml (range) increased from 645.8 (23.5-1,914) to 2,899 (1,176-37,336), P = 0.016, followed by an increase in median EPC/ml from 21.3 (4.7-42.5) to 94.7 (28.2-201.3), P = 0.016, prior to clinical relapse. In metastatic patients with progressive disease, median HPC/ml increased from 1,696 (10-16,470) to 5,124 (374-77,605), P = 0.0009, and median EPC/ml increased from 26 (0-560) to 71 (0-615) prior to progression, P = 0.10. In patients with responding disease, median HPC/ml decreased from 6,147 (912-85,070) to 633 (47-18,065), P = 0.05, and EPC/ml decreased from 46 (0-197) to 23 (0-105), P = 0.41, at response. There were no significant changes in these cells over time in patients with stable disease. Circulating bone marrow-derived HPCs and EPCs predict relapse and disease progression in BC patients.

Low-dose metronomic cyclophosphamide combined with vascular disrupting therapy induces potent antitumor activity in preclinical human tumor xenograft models

Vascular disrupting agents preferentially target the established but abnormal tumor vasculature, resulting in extensive intratumoral hypoxia and cell death. However, a rim of viable tumor tissue remains from which angiogenesis-dependent regrowth can occur, in part through the mobilization and tumor colonization of circulating endothelial progenitor cells (CEP). Cotreatment with an agent that blocks CEPs, such as a vascular endothelial growth factor pathway-targeting biological antiangiogenic drug, results in enhanced antitumor efficacy. We asked whether an alternative therapeutic modality, low-dose metronomic chemotherapy, could achieve the same result given its CEP-targeting effects. We studied the combination of the vascular disrupting agent OXi4503 with daily administration of CEP-inhibiting, low-dose metronomic cyclophosphamide to treat primary orthotopic tumors with the use of the 231/LM2-4 breast cancer cell line and MeWo melanoma cell line. In addition, CEP mobilization and various tumor characteristics were assessed. We found that daily p.o. low-dose metronomic cyclophosphamide was capable of preventing the CEP spike and tumor colonization induced by OXi4503. This was associated with a decrease in the tumor rim and marked suppression of primary 231/LM2-4 growth in nude as well as severe combined immunodeficient mice. Similar results were found in MeWo-bearing nude mice. The delay in tumor growth was accompanied by significant decreases in microvessel density, perfusion, and proliferation, and a significant increase in tumor cell apoptosis. No overt toxicity was observed. The combination of OXi4503 and metronomic chemotherapy results in prolonged tumor control, thereby expanding the list of therapeutic agents that can be successfully integrated with metronomic low-dose chemotherapy.