Bevacizumab: a review of its use in metastatic colorectal cancer

Role of bevacizumab in colorectal cancer growth and its adverse effects: a review

Angiogenesis affects both wound healing and malignant cell growth through nutrients and oxygen. Vascular endothelial growth factor (VEGF) is the most important element involved in this complex process. Inhibition of VEGF influences angiogenesis and may restrict tumor growth and metastatic ability. Modern anti-angiogenic therapy is based on this theory. Bevacizumab is a recombinant humanized monoclonal antibody (immunoglobulin G1) which binds with VEGF-A forming a large molecule. It can not be bound with VEGF tyrosine kinase receptors preventing VEGF-A incorporation; thus its activity is inhibited inducing blockage of VEGF-mediated angiogenesis. Bevacizumab, in combination with chemotherapy or other novel targeted therapeutic agents, is currently used more frequently in clinical practice, mainly for managing advanced colorectal cancer. It is also used for managing other malignancies, such as breast cancer, pancreatic cancer, prostate cancer, non small-cell lung cancer, metastatic renal carcinoma and ovarian tumors. Although it is generally considered a safe treatment, there are reports of some rare side effects which should be taken into account. Recent experiments in rats and mice show promising results with a wider therapeutic range.

Metastatic colorectal cancer-prolonging overall survival with targeted therapies

This review provides an updated overview of the management of metastatic colorectal cancer (CRC). With widespread application of personalized therapy based on specific patient and tumor characteristics, this will enable the oncologists to optimize overall survival while maintaining quality of life. The role of k-ras and braf testing in helping select systemic therapy that includes cetuximab or bevacizumab is clarified. Current management of metastatic CRC is based on careful attention to these finer points, explained in this article.

Modeling efficacy of bevacizumab treatment for metastatic colon cancer

Purpose: Bevacizumab, an FDA-approved adjuvant treatment for metastatic colon cancer, has extended survival for many patients. However, factors predicting response to treatment remain undefined.

Patients and Methods: Relevant clinical and environmental data were abstracted from medical records of 149 evaluable patients treated with bevacizumab for metastatic colon cancer at a multi-specialty clinic. Tumor response was calculated from radiologic reports using Response Evaluation Criteria in Solid Tumors (RECIST) criteria and verified by oncologist review. Patients with at least one occurrence of complete or partial response or stable disease were classified as responders; those exhibiting progressive disease were classified as non-responders.

Results: Univariate analysis demonstrated that blood in stool (P<0.05), unexplained weight loss (P<0.05), primary colon cancer site (P<0.05), chemotherapy treatment of primary tumor site (P<0.05), and adenocarcinoma versus adenoma subtype (P<0.05) was associated with tumor responsiveness. Factors remaining statistically significant following multivariate modeling included adenocarcinoma as tumor cell type versus other adenocarcinoma subtypes

(OR=6.35, 95% CI: 1.08-37.18), chemotherapy treatment applied to primary tumor (OR= 0.07, 95% CI: 0.0-0.76,), tumor localization to cecal/ascending colon (OR=0.061, 95% CI: 0.006-0.588,), and unexplained weight loss (OR=0.1, 95% CI: 0.02-0.56,). Chemotherapy treatment of primary tumor, unexplained weight loss, and cecal/ascending localization of the tumor were associated with poorer outcomes. Adenocarcinoma as cell type compared to other adenocarcinoma subtypes was associated with better response to bevacizumab treatment.

Conclusion: Results suggest that response to bevacizumab therapy may be predicted by modeling clinical factors including symptomology on presentation, tumor location and type, and initial response to chemotherapy.

Intraperitoneal bevacizumab combined with cytoreductive surgery: a pre-clinical study of tolerance and pharmacokinetics in an animal model

INTRODUCTION

Cytoreductive Surgery (CRS) combined with Hyperthermic Intraperitoneal Chemotherapy (HIPEC) is currently the only potentially curative treatment for peritoneal carcinomatosis (PC). Systemic administration of bevacizumab improves survival in patients with metastatic colorectal or ovarian cancer. Intraperitoneal administration of bevacizumab has been shown to be safe and effective in treating malignant ascites. The combination of CRS with intraperitoneal (IP) bevacizumab could maximize local control and survival from PC, but the associated morbidity from this is unknown. The aim of this study was to evaluate the safety of the combination of CRS with IP bevacizumab and to determine the pharmacokinetics of the drug in a rabbit model.

METHODS

Twenty healthy rabbits underwent a standardized procedure of debulking surgery, including peritonectomy and gastrointestinal anastomosis and were randomized to receive IP bevacizumab (25 mg/kg) or placebo. Another group of three rabbits underwent an instillation of IP bevacizumab (25 mg/kg) without surgery.

RESULTS

One rabbit that received IP bevacizumab died with no complication associated with the use of bevacizumab at autopsy. There was no significant difference between IP bevacizumab and placebo in weight loss, length of surgery or morbidity. The plasma concentration of bevacizumab increased to a peak at 24 h post IP administration. Bevacizumab was not detected in the plasma of animals without surgery.

CONCLUSION

This study suggests that IP bevacizumab does not increase morbidity and mortality of debulking surgery in an animal model. When surgery is performed, the pharmacokinetics of IP bevacizumab are modified in plasma.

An update on the current and emerging targeted agents in metastatic colorectal cancer

Over the past 8 to 10 years, significant advances have been made in the treatment of metastatic colorectal cancer (mCRC). In particular, the development of the targeted biologic agents bevacizumab, cetuximab, and panitumumab, and their integration with cytotoxic chemotherapy regimens has led to improvements in clinical efficacy. Despite these gains, the overall impact of current targeted agents in the treatment of mCRC has been relatively modest, and while 2-year survival has improved, no gains have been made, as of yet, in 5-year survival. Intense efforts continue to be focused on developing novel targeted agents with a different spectrum of activity. Presently, five novel targeted molecules are in phase III trials, including the antiangiogenesis agents aflibercept and ramucirumab, two novel receptor tyrosine kinase inhibitors, regorafenib and brivanib, and the Akt inhibitor perifosine. There are an additional 52 phase II trials investigating a wide range of other candidate molecules. The potential list of approved targeted agents in mCRC seems likely to increase over the next 5 to 10 years. To maximize their potential clinical impact, however, it will be critically important to introduce efficient molecular diagnostic methodologies into the drug development process for the identification and validation of predictive biomarkers for chemosensitivity. This article reviews the development of targeted agents for the treatment of mCRC, including the three molecules currently approved by the US Food and Drug Administration (FDA), as well as the main non-FDA-approved therapeutics currently undergoing phase II and III clinical testing.

The effect of bevacizumab on colon anastomotic healing in rats

PURPOSE

The aim of the study was to investigate the effect of angiogenesis inhibition by bevacizumab, a monoclonal anti-vascular endothelial growth factor (VEGF) antibody, on the healing process of colonic anastomoses in rats, assessing some specific involved factors. This new agent is used mainly in metastatic colorectal cancer. The angiogenesis plays an important role in both wound healing and metastatic invasion and spread of malignant cells. There has not been any evidence assessing the optimal time for its safe use in operated patients.

MATERIALS AND METHODS

Forty Wistar rats were randomly allocated into four equal groups. A colonic anastomosis was performed in all rats. Half of them received intraoperatively a single dose of bevacizumab 5 mg/body weight and the rest received placebo. The animals were sacrificed on the 7th (Avastin 7th, placebo 7th) and 14th (Avastin 14th, placebo 14th) postoperative day. The anastomosis was resected and sent for histological study and for tissue biochemical assays (VEGF, endothelin-1 (ET-1), C-reactive protein (CRP), pro-oxidant-antioxidant balance (PAB), carbonylated proteins, hydroxyproline) using specific enzyme-linked immunosorbent assay kits. For statistical analysis, the Mann-Whitney U test was used (of statistical significance when P < 0.05).

RESULTS

No complication or anastomotic dehiscence was observed. Histology did not reveal statistically significant differences between groups concerning degree of inflammation, fibroblasts, collagen, and fibrosis. Likewise, hydroxyproline levels did not differ. However, some statistically significant differences were found in VEGF, CRP and carbonyl proteins (Avastin 7th vs placebo 7th, placebo 14th vs placebo 7th), ET-1, and PAB (Avastin 14th vs Avastin 7th), which did not finally affect the collagen synthesis marker hydroxyproline, nor did the anastomotic strength.

CONCLUSIONS

Bevacizumab, when administered intraoperatively, has no significant effect on colon anastomotic healing in rats despite a transient mild ischemia.

Identification of serum angiopoietin-2 as a biomarker for clinical outcome of colorectal cancer patients treated with bevacizumab-containing therapy

Background:

The combination of chemotherapy with the vascular endothelial growth factor (VEGF) antibody bevacizumab is a standard of care in advanced colorectal cancer (CRC). However, biomarkers predicting outcome of bevacizumab-containing treatment are lacking. As angiopoietin-2 (Ang-2) is a key regulator of vascular remodelling in concert with VEGF, we investigated its role as a biomarker in metastatic CRC.

Methods:

Serum Ang-2 levels were measured in 33 healthy volunteers and 90 patients with CRC. Of these, 34 had metastatic disease and received bevacizumab-containing therapy. To determine the tissue of origin of Ang-2, quantitative real-time PCR was performed on microdissected cryosections of human CRC and in a murine xenograft model of CRC using species-specific amplification.

Results:

Ang-2 originated from the stromal compartment of CRC tissues. Serum Ang-2 levels were significantly elevated in patients with metastatic CRC compared with healthy controls. Amongst patients receiving bevacizumab-containing treatment, low pre-therapeutic serum Ang-2 levels were associated with a significant better response rate (82 vs 31% P<0.01), a prolonged median progression-free survival (14.1 vs 8.5 months; P<0.01) and a reduction of 91% in the hazard of death (P<0.05).

Conclusion:

Serum Ang-2 is a candidate biomarker for outcome of patients with metastatic CRC treated with bevacizumab-containing therapy, and it should be further validated to customise combined chemotherapeutic and anti-angiogenic treatment.

Targeting solid tumors with non-pathogenic obligate anaerobic bacteria

Molecular-targeting drugs with fewer severe adverse effects are attracting great attention as the next wave of cancer treatment. There exist, however, populations of cancer cells resistant to these drugs that stem from the instability of tumor cells and/or the existence of cancer stem cells, and thus specific toxicity is required to destroy them. If such selectivity is not available, these targets may be sought out not by the cancer cell types themselves, but rather in their adjacent cancer microenvironments by means of hypoxia, low pH, and so on. The anaerobic conditions present in malignant tumor tissues have previously been regarded as a source of resistance in cancer cells against conventional therapy. However, there now appears to be a way to make use of these limiting factors as a selective target. In this review, we will refer to several trials, including our own, to direct attention to the utilizable anaerobic conditions present in malignant tumor tissues and the use of bacteria as carriers to target them. Specifically, we have been developing a method to attack solid cancers using the non-pathogenic obligate anaerobic bacterium Bifidobacterium longum as a vehicle to selectively recognize and target the anaerobic conditions in solid cancer tissues. We will also discuss the existence of low oxygen pressure in tumor masses in spite of generally enhanced angiogenesis, overview current cancer therapies, especially the history and present situation of bacterial utility to treat solid tumors, and discuss the rationality and future possibilities of this novel mode of cancer treatment.

Moxifloxacin increases anti-tumor and anti-angiogenic activity of irinotecan in human xenograft tumors

Camptothecins (CPTs) are topoisomerase I inhibitors chemotherapeutic agents used in combination chemotherapy. We showed previously that combination of moxifloxacin (MXF) and CPT induced inhibitory effects on topoisomerase I activity, on proliferation of HT-29 cells in vitro and enhanced apoptosis, compared to CPT alone. Analysis of secretion of the pro-angiogenic factors IL-8 and VEGF showed significant reduction by MXF. Using a murine model of human colon carcinoma xenograft, we compared the effects of MXF/CPT in vitro to MXF/irinotecan combination in vivo. We show that the MXF/CPT inhibitory effects observed in vitro are reflected in the inhibition of the progressive growth of HT-29 cells implanted in SCID mice. Using caliper measurements, Doppler ultrasonography, image analyses and immunohistochemistry of nuclear proteins (Ki-67) and vascular endothelial cells (CD-31) we show that addition of MXF (45mg/kg) to a relatively ineffective dose of irinotecan (20mg/kg), results in a 50% and 30% decrease, respectively, in tumor size and a decrease in Ki-67 staining. Power Doppler Ultrasound showed a significant, pronounced decrease in the number of blood vessels, as did CD-31 staining, indicating decreased blood flow in tumors in mice treated with MXF alone or MXF/irinotecan compared to irinotecan. These results suggest that the combination of MXF/irinotecan may result in enhanced anti-neoplastic/anti-angiogenic activity.

Fluorophore-quencher based activatable targeted optical probes for detecting in vivo cancer metastases

In vivo molecularly targeted fluorescence imaging of tumors has been proposed as a strategy for improving cancer detection and management. Activatable fluorophores, which increased their fluorescence by 10-fold after binding tumor cells, result in much higher target to background ratios than conventional fluorophores. We developed an in vivo targeted activatable optical imaging probe based on a fluorophore-quencher pair, bound to a targeting moiety. With this system, fluorescence is quenched by the fluorophore-quencher interaction outside cancer cells, but is activated within the target cells by dissociation of the fluorophore-quencher pair. We selected the TAMRA (fluorophore)-QSY7 (quencher) pair and conjugated it to either avidin (targeting the D-galactose receptor) or trastuzumab (a monoclonal antibody against the human epithelial growth factor receptor type2 (HER2/neu)) and evaluated their performance in mouse models of cancer. Two probes, TAMRA-QSY7 conjugated avidin (Av-TM-Q7) and trastuzumab (Traz-TM-Q7) were synthesized. Both demonstrated better than similar self-quenching probes. In vitro fluorescence microscopic studies of SHIN3 and NIH/3T3/HER2+ cells demonstrated that Av-TM-Q7 and Traz-TM-Q7 produced high intracellular fluorescent signal. In vivo imaging with Av-TM-Q7 and Traz-TM-Q7 in mice enabled the detection of small tumors. This molecular imaging probe, based on a fluorophore-quencher pair conjugated to a targeting ligand, successfully detected tumors in vivo due to its high activation ratio and low background signal. Thus, these activatable probes, based on the fluorophore-quencher system, hold promise clinically for "see and treat" strategies of cancer management.

ING proteins as potential anticancer drug targets

Recent emerging evidence suggests that ING family proteins play roles in carcinogenesis both as oncogenes and tumor suppressor genes depending on the family members and on cell status. Previous results from non-physiologic overexpression experiments showed that all five family members induce apoptosis or cell cycle arrest, thus it had been thought until very recently that all of the family members function as tumor suppressor genes. Therefore restoration of ING family proteins in cancer cells has been proposed as a treatment for cancers. However, ING2 knockdown experiments showed unexpected results: ING2 knockdown led to senescence in normal human fibroblast cells and suppressed cancer cell growth. ING2 is also overexpressed in colorectal cancer, and promotes cancer cell invasion through an MMP13 dependent pathway. Additionally, it was reported that ING2 has two isoforms, ING2a and ING2b. Although expression of ING2a predominates compared with ING2b, both isoforms confer resistance against cell cycle arrest or apoptosis to cancer cells, thus knockdown of both isoforms is critical to remove this resistance. Taken together, these results suggest that ING2 can function as an oncogene in some specific types of cancer cells, indicating restoration of this gene in cancer cells could cause cancer progression. Because knockdown of ING2 suppresses cancer cell invasion and induces apoptosis or cell cycle arrest, ING2 may be an anticancer drug target. In this brief review, we discuss possible clinical applications of ING2 with the latest knowledge of molecular targeted therapies.

Multidisciplinary approach to esophageal and gastric cancer

The incidence of esophageal and gastric malignancies has increased over the last decade. Historically, surgery has been considered the best treatment for these cancers. However, long-term survival after surgery is fair at best, because of the tendency of disease to recur locally and distantly. Presently, the management of these cancers involves surgery, chemotherapy, and radiation therapy. This article discusses various treatment strategies that employ these modalities either alone or in combination, in an attempt to improve survival rates for patients who have gastroesophageal malignancies.

Peritoneal minimal residual disease in colorectal cancer: mechanisms, prevention, and treatment

Roughly one in five patients with colorectal cancer develops peritoneal minimal residual disease after surgical resection, and about one in seven patients develops peritoneal carcinomatosis. By contrast with the vast body of research addressing haematogenous metastasis, little is known about the biology of peritoneal spread of colorectal cancer. The development of peritoneal carcinomatosis involves well-defined steps including cell shedding and transport, adhesion to the mesothelial layer, invasion of and proliferation into the submesothelial stroma, and potential access to the systemic circulation. In this Review, we summarise the molecular mechanisms and potential preventive measures associated with each step of the peritoneal metastatic cascade.

The use of bevacizumab in colorectal, lung, breast, renal and ovarian cancer: where does it fit?

Bevacizumab is approved for the treatment of colorectal cancer, breast cancer, non-small cell lung cancer and renal cell cancer. Before embracing this expensive agent for many other indications, it remains critical to be aware of the evidence upon which oncologists base their day-to-day clinical practice. In this review, we address the results of clinical studies upon which bevacizumab's current use is based and discuss some future perspectives.