Angiogenesis as a strategic target for ovarian cancer therapy

Phase I clinical trials in 85 patients with gynecologic cancer: the M. D. Anderson Cancer Center experience

OBJECTIVE

Disseminated gynecologic cancers are usually fatal due to chemoresistance. Recently, rationally developed, targeted agents are entering the early clinical trials setting. We assessed patients with metastatic gynecologic cancers in a dedicated phase I clinical trials clinic in order to determine their outcome.

METHODS

We reviewed records for 89 consecutive patients with gynecologic cancers referred to the Phase I Clinical Trials Program, 85 (96%) of whom were treated on > or = 1 trial.

RESULTS

Cancer diagnoses were ovarian (N=43), uterine (N=19), cervix (N=17), and other. Median age was 58 years; median number of prior cytotoxic regimens, five. Two patients (2.4%) achieved a CR; four (4.7%), a PR; and eight (9.4%), SD > or = 6 months (total CR/PR/SD > or = 6 months=16.5%) for the first phase I trial. Twenty-five patients enrolled on a second trial and three, on a third (N=113 trials total). Combining response data for all trials, of the 85 patients, two achieved CR (2.4%), nine achieved PR (10.6%), and 12 (14%) had SD for > or = 6 months. One-year survival was 30% (95% CI, 21% to 44%). There was no difference in time-to-treatment failure (TTF) on phase I versus the patient's last standard treatment.

CONCLUSION

Twenty-three of 85 patients (27%) with advanced, heavily pretreated, gynecologic cancers achieved CR/PR/SD > or = 6 months on a phase I trial, and overall TTF on phase I was comparable to that of last conventional therapy, suggesting that participation in a phase I trial is a reasonable option for these patients.

Quantity and clinical relevance of circulating endothelial progenitor cells in human ovarian cancer

Background

Circulating bone marrow-derived endothelial progenitor cells (EPCs) have been reported to participate in tumor angiogenesis and growth; however, the role of circulating EPCs in tumor progression is controversial. The role of circulating EPCs in ovarian cancer progression and angiogenesis has not yet been investigated.

Methods

The number of circulating EPCs in the peripheral blood in 25 healthy volunteers and 42 patients with ovarian cancer was determined by flow cytometry. EPCs were defined by co-expression of CD34 and vascular endothelial growth factor receptor 2 (VEGFR2). In addition, we determined CD34 and VEGFR2 mRNA levels by real-time reverse transcription-polymerase chain reaction. Plasma levels of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) were determined by enzyme-linked immunosorbent assay.

Results

Circulating levels of EPCs were significantly increased in ovarian cancer patients, correlating with tumor stage and residual tumor size. Higher levels of EPCs were detected in patients with stage III and IV ovarian cancer than in patients with stage I and II disease. After excision of the tumor, EPCs levels rapidly declined. Residual tumor size greater than 2 cm was associated with significantly higher levels of EPCs. In addition, high circulating EPCs correlated with poor overall survival. Pretreatment CD34 mRNA levels were not significantly increased in ovarian cancer patients compared with healthy controls; however, VEGFR2 expression was increased, and plasma levels of VEGF and MMP-9 were also elevated.

Conclusions

Our results demonstrate the clinical relevance of circulating EPCs in ovarian cancer. EPCs may be a potential biomarker to monitor ovarian cancer progression and angiogenesis and treatment response.

Targeted therapies in epithelial ovarian cancer

Molecularly targeted therapy is relatively new to ovarian cancer despite the unquestionable success with these agents in other solid tumours such as breast and colorectal cancer. Advanced ovarian cancer is chemosensitive and patients can survive several years on treatment. However chemotherapy diminishes in efficacy over time whilst toxicities persist. Newer biological agents that target explicit molecular pathways and lack specific chemotherapy toxicities such as myelosuppression offer the advantage of long-term therapy with a manageable toxicity profile enabling patients to enjoy a good quality of life. In this review we appraise the emerging data on novel targeted therapies in ovarian cancer. We discuss the role of these compounds in the front-line treatment of ovarian cancer and in relapsed disease; and describe how the development of predictive clinical, molecular and imaging biomarkers will define the role of biological agents in the treatment of ovarian cancer.

Targeting pericytes with a PDGF-B aptamer in human ovarian carcinoma models

PURPOSE

On the basis of the known role of platelet-derived growth factor (PDGF)-BB/PDGF receptor (PDGFR) beta in pericyte regulation, highly specific inhibitors of this target are needed. We tested the efficacy of a highly selective aptamer against PDGF-B with or without anti-VEGF therapy in ovarian cancer models.

RESULTS

Bevacizumab inhibited tumor growth by 45% and 48% in the HeyA8 and SKOV3ip1 models, respectively. AX102 had minimal effect on the HeyA8 model, but increased tumor growth in the SKOV3ip1 model. However, bevacizumab plus AX102 was more effective than bevacizumab alone, and resulted in 76-88% inhibition of tumor growth in both models. A longitudinal study in the HeyA8 model using bioluminescence imaging showed that combination of bevacizumab, AX102 and paclitaxel caused tumor reduction by 65% (based on bioluminescence imaging). In the HeyA8 model, MVD and PCNA counts were significantly reduced in the bevacizumab treatment groups, and pericyte coverage was significantly decreased in the AX102 treatment groups. In the SKOV3ip1 model, MVD and PCNA was significantly reduced in the bevacizumab treatment group, and even lower in the bevacizumab and AX102 combination treatment group.

EXPERIMENTAL DESIGN

The therapeutic efficacy of targeting endothelial cells (bevacizumab) and/or pericytes (PDGF-aptamer, AX102) was examined using HeyA8 and SKOV3ip1 orthotopic models of ovarian cancer metastasis. Following therapy, tumors were examined for microvessel density (MVD), proliferating cell nuclear antigen (PCNA) and vascular maturation (pericyte coverage).

CONCLUSIONS

Dual targeting of endothelial cells and pericytes holds potential as an anti-vascular therapeutic approach in ovarian carcinoma.

Pazopanib: an antiangiogenic drug in perspective

Pazopanib, a tyrosine kinase inhibitor targeted to angiogenesis, has been tested in preclinical and clinical trials and has shown promising activity against a variety of solid tumors, such as renal cancer, all of which are related to the angiogenic pathway. It has a safety profile related to this mechanism of action. Diarrhea, hypertension, hair depigmentation and nausea are the most common side effects. Pazopanib is currently under evaluation as monotherapy and in combination with some potentially synergistic agents of proven activity.

TrkB as a therapeutic target for ovarian cancer

BACKGROUND

In many countries, ovarian cancer is the most lethal gynecological malignancy. Its poor prognosis is mainly due to the late stage of disease with metastasis at presentation. The significant failure rate of chemotherapy in patients with advanced stage disease is also a main concern. As such, developing novel therapeutic targets is essential to improve long-term survival. Overexpression of Tropomyosin-related kinase B (TrkB), a tyrosine kinase receptor, has been documented in ovarian cancer and is found to be correlated with poor prognosis.

OBJECTIVE/METHODS

We discuss the functional roles and the related downstream signaling pathways of TrkB and its ligand brain-derived neurotrophic factor (BDNF) in ovarian cancer. The possible crosstalk between TrkB/BDNF and other putative molecular targets in ovarian cancer is also discussed.

RESULTS/CONCLUSIONS

All these latest findings shed light on the application of TrkB as a therapeutic target for ovarian cancer.

Sustained progression-free survival with weekly paclitaxel and bevacizumab in recurrent ovarian cancer

OBJECTIVE

To determine efficacy, toxicity, and survival in patients with recurrent epithelial ovarian cancer (EOC) receiving combination of weekly paclitaxel and biweekly bevacizumab (PB).

METHODS

We reviewed chemotherapy logs identifying all patients receiving combination PB. Toxicities were graded using CTCAEv3.0 criteria. Response rates (RR) were measured using RECIST criteria or by CA-125 levels per modified Rustin criteria. RR and progression-free survival (PFS) were determined and plotted using Kaplan-Meier survival analysis.

RESULTS

Fifty-one patients receiving at least two cycles of chemotherapy were evaluable for survival and 55 patients receiving one cycle of PB were evaluable in toxicity analysis. The mean number of previous regimens was four. The overall median PFS was 7 months and median OS was 12 months. The overall response rate (ORR) was 60% (CR 25% and PR 35%). Median PFS for complete and partial responders were 14 and 5 months respectively. Stable disease was seen in 26% with median PFS of 6 months. Thirteen experienced treatment delays for a variety of factors. The most G3/4 toxicities were fatigue (16%), hematologic (9%) and neurotoxicity (7%). Three patients (5%) experienced bowel perforations.

CONCLUSIONS

Combination of paclitaxel and bevacizumab is feasible and demonstrates an acceptable toxicity profile and a high response rate. These observations should be useful in planning future clinical trials with this combination therapy.

VEGFR-2 silencing by small interference RNA (siRNA) suppresses LPA-induced epithelial ovarian cancer (EOC) invasion

BACKGROUND

The VEGF-VEGF receptor (VEGFR) signaling axis has emerged as a promising target for cancer therapy, attributing to its vital role in tumor angiogenesis and growth. We have previously reported the regulation of epithelial ovarian cancer (EOC) invasion and migration by VEGF and the implication of VEGF-VEGFR-2 axis in lysophosphatidic acid (LPA)-induced EOC invasion. However, the expression profile of VEGF and VEGFRs in EOC, their association with tumor aggressiveness, and their regulation by LPA remain unclear.

OBJECTIVES AND METHODS

In this study, we examined the expression of VEGFR-1, VEGFR-2, neuropilin-1 (NRP-1), NRP-2, VEGF(121), and VEGF(165) in established EOC cell lines and assessed their correlation with cell invasiveness. Moreover, using an ovarian cancer tissue qPCR array, we analyzed VEGFR-2 expression across a panel of 48 tissues with different disease stages and histological grades. We also tested the effect of LPA on VEGF and VEGFR-2 expression and examined whether blocking VEGFR-2 by RNA interference (RNAi) affects LPA-induced EOC invasion.

RESULTS

We show that VEGF and VEGFR-2 expression correlates with cell invasiveness and VEGFR-2 expression in ovarian cancer tissues correlate with tumor grade. In addition, LPA, at 20 muM, significantly induced the expression of VEGF(121), VEGF(165), and VEGFR-2 in SKOV3 and DOV13 cells (P<0.05). VEGFR-2 small interference RNA (siRNA) transfection remarkably decreased LPA's invasion-promoting effect (P<0.001) in SKOV3 cells without significantly decreasing SKOV3 cells' basal invasiveness. In DOV13 cells, VEGFR-2 silencing significantly decreases both the basal level cell invasion and LPA's invasion promoting effect (P<0.001).

CONCLUSION

These results suggest that decreasing VEGFR-2 expression by RNAi may prove to be an effective method to reduce the metastatic potential of EOC cells exposed to elevated levels of LPA.

Genistein induces G2/M cell cycle arrest and apoptosis of human ovarian cancer cells via activation of DNA damage checkpoint pathways

Genistein is a major isoflavonoid in dietary soybean, commonly consumed in Asia. Genistein exerts inhibitory effects on the proliferation of various cancer cells and plays an important role in cancer prevention. However, the molecular and cellular mechanisms of genistein on human ovarian cancer cells are still little known. We show that exposure of human ovarian cancer HO-8910 cells to genistein induces DNA damage, and triggers G2/M phase arrest and apoptosis. Furthermore, we also found that checkpoint proteins ATM and ATR are phosphorylated and activated in the cells treated with genistein. It is also shown that genistein increases the phosphorylation and activation of Chk1 and Chk2, which results in the phosphorylation and inactivation of phosphatases Cdc25C and Cdc25A, and thereby the phosphorylation and inactivation of Cdc2 which arrests cells in G2/M phase. Moreover, genistein enhances the phosphorylation and activation of p53, while decreases the ratio of Bcl-2/Bax and Bcl-xL/Bax and the level of phosphorylated Akt, which result in cells undergoing apoptosis. These results demonstrate that genistein-activated ATM-Chk2-Cdc25 and ATR-Chk1-Cdc25 DNA damage checkpoint pathways can arrest ovarian cancer cells in G2/M phase, and induce apoptosis while the cellular DNA damage is too serious to be repaired. Thus, the antiproliferative, DNA damage-inducing and pro-apoptotic activities of genistein are probably responsible for its genotoxic effects on human ovarian cancer HO-8910 cells.

'Fit-for-purpose' validation of SearchLight multiplex ELISAs of angiogenesis for clinical trial use

Validated assays of circulating biomarkers of angiogenesis to predict and determine the efficacy of vascular-targeted anticancer drugs would facilitate successful drug development. Multiple biomarker candidates exist and a multiplex approach was sought to minimise the requisite patient blood volume and to aid selection of those biomarkers with greatest potential clinical utility. Validation of the SearchLight multiplex ELISA platform comprising two multiplex assays of nine potential angiogenesis biomarkers was conducted (plex 1; VEGF R1 and R2, IL-8, KGF, PlGF; plex 2; PDGFbb, HGF, FGFb and VEGF). The study focused on instrument qualification, analyte specificity within the multiplex format, assay precision and reproducibility. No evidence was found within the multiplex that signals output from one analyte impinged on another or that antibody cross-reactivity occurred. Spike recovery for 5 between-experiment repeats was within +/-15% of input values for 7 of the 9 multiplexed analytes, with a coefficient of variation (CV) of <20% for 6 of the 9 analytes. Plasma samples from 8 ovarian cancer patients (who were not receiving therapy) were assessed using the two multiplexes on this platform to explore the likely baseline variability in this disease context. This study suggests that the platform and the multiplex approach will be useful to evaluate pharmacodynamic responses to vascular targeted therapy in early clinical trials.

Beyond chemotherapy: targeted therapies in ovarian cancer

Ovarian cancer is the leading cause of death from gynaecological malignancies in the Western world. Despite the evolution of surgical techniques and meticulously designed chemotherapy regimens, relapse remains almost inevitable in patients with advanced disease. In an age when great advances have been made in understanding the genetics and molecular biology of this heterogeneous disease, it is likely that the introduction of novel targeted therapies will have a major impact on the management of ovarian cancer. Importantly, such strategies might allow selection of treatments based on the molecular characteristics of tumours and bring us closer to an era of personalized medicine.