Current perspective: Bevacizumab in colorectal cancer – A time for reappraisal?

Smart pH-responsive polyhydralazine/bortezomib nanoparticles for remodeling tumor microenvironment and enhancing chemotherapy

The clinical translation of nanomedicines has been impeded by the unfavorable tumor microenvironment (TME), particularly the tortuous vasculature networks, which significantly influence the transport and distribution of nanomedicines into tumors. In this work, a smart pH-responsive bortezomib (BTZ)-loaded polyhydralazine nanoparticle (PHDZ/BTZ) is presented, which has a great capacity to augment the accumulation of BTZ in tumors by dilating tumor blood vessels via specific release of vasodilator hydralazine (HDZ). The Lewis acid-base coordination effect between the boronic bond of BTZ and amino of HDZ empowered PHDZ/BTZ nanoparticles with great stability and high drug loading contents. Once triggered by the acidic tumor environment, HDZ could be released quickly to remodel TME through tumor vessel dilation, hypoxia attenuation, and lead to an increased intratumoral BTZ accumulation. Additionally, our investigation revealed that this pH-responsive nanoparticle dramatically suppressed tumor growth, inhibited the occurrence of lung metastasis with fewer side effects and induced immunogenic cell death (ICD), thereby eliciting immune activation including massive cytotoxic T lymphocytes (CTLs) infiltration in tumors and efficient serum proinflammatory cytokine secretion compared with free BTZ treatment. Thus, with efficient drug loading capacity and potent immune activation, PHDZ nanoparticles exhibit great potential in the delivery of boronic acid-containing drugs aimed at a wide range of diseases.

Hypoxic tumor microenvironment: Implications for cancer therapy

IMPACT STATEMENT

Hypoxia contributes to tumor aggressiveness and promotes growth of many solid tumors that are often resistant to conventional therapies. In order to achieve successful therapeutic strategies targeting different cancer types, it is necessary to understand the molecular mechanisms and signaling pathways that are induced by hypoxia. Aberrant tumor vasculature and alterations in cellular metabolism and drug resistance due to hypoxia further confound this problem. This review focuses on the implications of hypoxia in an inflammatory TME and its impact on the signaling and metabolic pathways regulating growth and progression of cancer, along with changes in lymphangiogenic and angiogenic mechanisms. Finally, the overarching role of hypoxia in mediating therapeutic resistance in cancers is discussed.

Antitumor effects of Endostar(rh-endostatin) combined with gemcitabine in different administration sequences to treat Lewis lung carcinoma

Background: Endostatin therapy is known to efficiently inhibit angiogenesis and growth of endothelial cells. Nonetheless, the antitumor mechanisms of endostatin combined with chemotherapy remain to be elucidated. Methods: In our study, a Lewis lung carcinoma transplant mouse model was established and treated with the recombinant human [rh]-endostatin, Endostar, combined with gemcitabine at different sequences. 18F-FDG PET/CT imaging was performed to monitor tumor growth, and hypoxia was examined using an oxygen microelectrode. Vascular endothelial growth factor (VEGF) and alpha smooth muscle actin (α-SMA) levels were detected via immunohistochemistry analysis and cell cycle distributions were analyzed by flow cytometry. Results: Endostar decreased VEGF expression, improved hypoxia, and influenced cell cycle distributions. Simultaneous treatment of Endostar and gemcitabine displayed significantly tumor inhibition, possessed the lowest uptake of FDG, improved oxygen partial pressure, decreased expression of VEGF, and increased pericyte coverage. Cell cycle analysis demonstrated that cells accumulated in the S phase following gemcitabine treatment and G0/G1 arrest occurred following Endostar treatment. An increase of cells in G0/G1 phase was observed following treatment with Endostar and gemcitabine. Conclusions: Our study suggests that the combination therapy of Endostar with gemcitabine simutaneously may optimally enhance their individual antitumor effects.

Enteroendocrine cells-sensory sentinels of the intestinal environment and orchestrators of mucosal immunity

The intestinal epithelium must balance efficient absorption of nutrients with partitioning commensals and pathogens from the bodies' largest immune system. If this crucial barrier fails, inappropriate immune responses can result in inflammatory bowel disease or chronic infection. Enteroendocrine cells represent 1% of this epithelium and have classically been studied for their detection of nutrients and release of peptide hormones to mediate digestion. Intriguingly, enteroendocrine cells are the key sensors of microbial metabolites, can release cytokines in response to pathogen associated molecules and peptide hormone receptors are expressed on numerous intestinal immune cells; thus enteroendocrine cells are uniquely equipped to be crucial and novel orchestrators of intestinal inflammation. In this review, we introduce enteroendocrine chemosensory roles, summarize studies correlating enteroendocrine perturbations with intestinal inflammation and describe the mechanistic interactions by which enteroendocrine and mucosal immune cells interact during disease; highlighting this immunoendocrine axis as a key aspect of innate immunity.

MULTIMERIN2 binds VEGF-A primarily via the carbohydrate chains exerting an angiostatic function and impairing tumor growth

Angiogenesis is a key process occurring under both physiological and pathological conditions and is a hallmark of cancer. We have recently demonstrated that the extracellular matrix (ECM) molecule MULTIMERIN2 exerts an angiostatic function through the binding to VEGF-A. In this study we identify the region of the molecule responsible for the binding and demonstrate that the interaction involves the carbohydrate chains. MULTIMERIN2 interacts with other VEGF-A isoforms and VEGF family members such as VEGF-B, -C, -D and PlGF-1 suggesting that the molecule may function as a reservoir for different cytokines. In response to VEGF-A₁₆₅, we show that MULTIMERIN2 impairs the phosphorylation of VEGFR2 at both Y1175 and Y1214 residues, halts SAPK2/p38 activation and negatively affects endothelial cell motility. In addition, MULTIMERIN2 and its active deletion mutant decrease the availability of the VEGFR2 receptor at the EC plasma membrane. The ectopic expression of MULTIMERIN2 or its active deletion mutant led to a striking reduction of tumor-associated angiogenesis and tumor growth. In conclusion, these data pinpoint MULTIMERIN2 as a key angiostatic molecule and disclose the possibility to develop new prognostic tools and improve the management of cancer patients.

Exploring Novel Methods for Modulating Tumor Blood Vessels in Cancer Treatment

Several studies have explored the potential of targeting tumor angiogenesis in cancer treatment. Anti-angiogenesis monotherapy, which reduces blood vessel numbers, may still hold some promise in cancer treatment, but thus far it has only provided a modest effect on overall survival benefits. When combined with standard chemotherapies, some significant improvements in cancer therapy have been reported. However, anti-angiogenesis therapies can have undesirable effects, including the induction of tumor hypoxia and reduction of delivery of chemotherapeutic drugs. Interestingly, anti-angiogenic drugs, such as bevacizumab, when used at lower doses, can actually induce vascular normalization (that is, they improve blood vessel function and flow) and potentially enhance co-administrated chemotherapeutic drug delivery. Unfortunately, vascular normalization is a difficult approach to apply in clinical settings. Thus, there is an urgent need to explore new approaches for modulating the tumor vasculature. Here, we explore how vascular promotion strategies (which enhance blood vessel numbers and leakiness) may be optimized for combination therapies as an alternative option for cancer treatment.

Antiangiogenic therapy in colorectal cancer: where are we 5 years later?

The past 5 years mark a watershed period in the treatment of patients with colorectal cancer (CRC). During this time, results from several clinical trials proved that targeting tumor-mediated angiogenesis improves overall survival for patients with metastatic CRC (mCRC) when used in combination with first-line and second-line chemotherapy regimens, data that do not simply serve as "proof of principle" for antiangiogenic therapy but that will drive much of the research agenda in CRC for the coming years. Despite the demonstrated gains in survival when antiangiogenic therapy is used for patients with metastatic disease, however, results from the first trial to test the addition of bevacizumab to adjuvant chemotherapy have been disappointing. The expense of agents in the targeted therapy category has been the cause of much discussion on their appropriate use and puts particular emphasis on the need for suitable markers that will allow for the appropriate selection of patients. Although antiangiogenic therapy has demonstrated clear benefit in the treatment of patients with mCRC, limitations in efficacy, duration of therapy, role of maintenance therapy, potential toxicities, and predictive markers for optimal patient selection are subjects of ongoing research. Herein, we present a review of the recent advances in antiangiogenic therapy in CRC and provide insights into several promising upcoming studies.

Highly effective antiangiogenesis via magnetic mesoporous silica-based siRNA vehicle targeting the VEGF gene for orthotopic ovarian cancer therapy

Therapeutic antiangiogenesis strategies have demonstrated significant antitumor efficacy in ovarian cancer. Recently, RNA interference (RNAi) has come to be regarded as a promising technology for treatment of disease, especially cancer. In this study, vascular endothelial growth factor (VEGF)-small interfering RNA (siRNA) was encapsulated into a magnetic mesoporous silica nanoparticle (M-MSN)-based, polyethylenimine (PEI)-capped, polyethylene glycol (PEG)-grafted, fusogenic peptide (KALA)-functionalized siRNA delivery system, termed M-MSN_VEGF siRNA@PEI-PEG-KALA, which showed significant effectiveness with regard to VEGF gene silencing in vitro and in vivo. The prepared siRNA delivery system readily exhibited cellular internalization and ease of endosomal escape, resulting in excellent RNAi efficacy without associated cytotoxicity in SKOV3 cells. In in vivo experiments, notable retardation of tumor growth was observed in orthotopic ovarian tumor-bearing mice, which was attributed to significant inhibition of angiogenesis by systemic administration of this nanocarrier. No obvious toxic drug responses were detected in major organs. Further, the magnetic core of M-MSN_VEGF siRNA@PEI-PEG-KALA proved capable of probing the site and size of the ovarian cancer in mice on magnetic resonance imaging. Collectively, the results demonstrate that an M-MSN-based delivery system has potential to serve as a carrier of siRNA therapeutics in ovarian cancer.

Dual-action combination therapy enhances angiogenesis while reducing tumor growth and spread

Increasing chemotherapy delivery to tumors, while enhancing drug uptake and reducing side effects, is a primary goal of cancer research. In mouse and human cancer models in vivo, we show that coadministration of low-dose Cilengitide and Verapamil increases tumor angiogenesis, leakiness, blood flow, and Gemcitabine delivery. This approach reduces tumor growth, metastasis, and minimizes side effects while extending survival. At a molecular level, this strategy alters Gemcitabine transporter and metabolizing enzyme expression levels, enhancing the potency of Gemcitabine within tumor cells in vivo and in vitro. Thus, the dual action of low-dose Cilengitide, in vessels and tumor cells, improves chemotherapy efficacy. Overall, our data demonstrate that vascular promotion therapy is a means to improve cancer treatment.

Antiangiogenic Therapy with Human Apolipoprotein(a) Kringle V and Paclitaxel in a Human Ovarian Cancer Mouse Model

INTRODUCTION: The present study compared the effect of combination therapy using human apolipoprotein(a) kringle V (rhLK8) to conventional chemotherapy with paclitaxel for human ovarian carcinoma producing high or low levels of vascular endothelial growth factor (VEGF). MATERIALS AND METHODS: Human ovarian carcinoma cells producing high (SKOV3ip1) or low (HeyA8) levels of VEGF were implanted into the peritoneal cavity of female nude mice. Seven days later, mice were randomized into four groups: control (vehicle), paclitaxel [5 mg/kg, weekly intraperitoneal (i.p.) injection], rhLK8 (50 mg/kg, daily i.p. injection), or the combination of paclitaxel and rhLK8. Mice were treated for 4 weeks and examined by necropsy. RESULTS: In mice implanted with SKOV3ip1 cells, rhLK8 treatment had no significant effect on tumor incidence or the volume of ascites but induced a significant decrease in tumor weight compared with control mice. Paclitaxel significantly reduced tumor weight and ascites volume, and combination treatment with paclitaxel and rhLK8 had an additive therapeutic effect. Similarly, in HeyA8 mice, the effect of combination treatment on tumor weight and tumor incidence was statistically significantly greater than that of paclitaxel or rhLK8 alone. Immunohistochemical analysis showed a significant decrease in microvessel density and a marked increase of apoptosis in tumor and tumor-associated endothelial cells in response to combination treatment with paclitaxel and rhLK8. CONCLUSION: Collectively, these results suggest that antiangiogenic therapy with rhLK8 in combination with taxane-based conventional chemotherapy could be effective for the treatment of ovarian carcinomas, regardless of VEGF status.

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.

Individual fluorouracil dose adjustment in FOLFOX based on pharmacokinetic follow-up compared with conventional body-area-surface dosing: a phase II, proof-of-concept study

BACKGROUND

To compare the efficacy and safety of pharmacokinetically (PK) guided fluorouracil (5-FU) dose adjustment vs. standard body-surface-area (BSA) dosing in a FOLFOX (folinic acid, fluorouracil, oxaliplatin) regimen in metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

A total of 118 patients with mCRC were administered individually determined PK-adjusted 5-FU in first-line FOLFOX chemotherapy. The comparison arm consisted of 39 patients, and these patients were also treated with FOLFOX with 5-FU by BSA. For the PK-adjusted arm 5-FU was monitored during infusion, and the dose for the next cycle was based on a dose-adjustment chart to achieve a therapeutic area under curve range (5-FU(ODPM Protocol)).

RESULTS

The objective response rate was 69.7% in the PK-adjusted arm, and median overall survival and median progression-free survival were 28 and 16 months, respectively. In the traditional patients who received BSA dosage, objective response rate was 46%, and overall survival and progression-free survival were 22 and 10 months, respectively. Grade 3/4 toxicity was 1.7% for diarrhea, 0.8% for mucositis, and 18% for neutropenia in the dose-monitored group; they were 12%, 15%, and 25%, respectively, in the BSA group.

CONCLUSIONS

Efficacy and tolerability of PK-adjusted FOLFOX dosing was much higher than traditional BSA dosing in agreement with previous reports for 5-FU monotherapy PK-adjusted dosing. Analysis of these results suggests that PK-guided 5-FU therapy offers added value to combination therapy for mCRC.

Timing and perioperative risk factors for in-hospital and post-discharge venous thromboembolism after colorectal cancer resection

INTRODUCTION

We postulated that the risk of venous thromboembolic disease (VTE) may persist after discharge and tested this hypothesis in patients undergoing colorectal resection for cancer.

METHODS

The American College of Surgeons National Surgery Quality Improvement Program database was queried for patients undergoing colorectal resections for cancer from 2005 to 2009. The outcome analyzed was a 30-day deep vein thrombosis (DVT) and/or pulmonary embolism (PE). Multivariable forward stepwise regression was used to identify independent predictors of VTE.

RESULTS

The database contained 21 943 colorectal cancer resections. The 30-day DVT rate was 1.4% (306 of 21 943), 29% (89 of 306) were diagnosed post-discharge. The 30-day PE rate was 0.8% (180 of 21 943), 33% (60 of 180) was diagnosed post-discharge, the combined DVT/PE rate was 2.0% (446 of 21 943). The median time to diagnosis of VTE was 9 days (interquartile range 4-16) after surgery. Post-discharge VTE rates in patients with length of stay (LOS) less than 1 week (0.6%) were similar to patients with LOS greater than 1 week (0.7%, Fisher exact P not significant). Independent risk factors for post-discharge VTE were preoperative steroid use for chronic condition (odds ratio [OR] 2.90, 95% confidence interval [CI] 1.51-5.57, P = .001) and preoperative systemic inflammatory response syndrome (OR 2.26, 95% CI 1.24-4.10, P = .008).

CONCLUSIONS

Diagnosis of almost one third of postoperative VTE in this patient population occurred after discharge. The duration of the prothrombotic stimulus of surgery is not well defined, and patients with malignancy are at high risk of VTE; thromboprophylaxis after discharge should be considered for these patients.

Bevacizumab-associated fistula formation in postoperative colorectal cancer patients

BACKGROUND

Adjuvant chemotherapy regimens for metastatic colorectal cancer (CRC) routinely include bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor (VEGF). We have identified a correlation between bevacizumab and fistula formation after resection of advanced CRC.

STUDY DESIGN

Patients undergoing treatment with bevacizumab for metastatic CRC after 2005 were identified and reviewed. Of 222 consecutive patients, 9 patients treated with bevacizumab subsequently developed fistulas. These patients' charts were reviewed with attention to diagnosis, timing of operation relative to bevacizumab therapy, location of fistula, and fistula treatment.

RESULTS

Of the 9 identified patients (9 of 222, 4.1%), 6 had rectal cancer, 2 had colon cancer, and 1 had synchronous CRC. Fistulas were most commonly anal or perineal (6 of 9, 66.7%) and colovesicular (3 of 9, 33%). On average, bevacizumab was initiated 23.6 months after the initial operation; complications occurred 3.9 months after starting bevacizumab. Nearly uniformly, cessation of bevacizumab led to fistula healing; however, 3 patients (33%) required fecal diversion.

CONCLUSIONS

Bevacizumab is the most common antiangiogenesis agent used for treatment of metastatic CRC. Previous adverse events associated with bevacizumab treatment include venous thromboembolism, poor wound healing, and spontaneous bowel perforation. In this report, late postoperative development of fistulas occurred relatively soon after initiation of bevacizumab and usually spontaneously resolved with cessation of bevacizumab treatment. Based on the timing of fistula development relative to operation and initiation of bevacizumab, fistulas are likely secondary to bevacizumab therapy rather than postsurgical complications. Bevacizumab-induced fistulas occur in a small, but significant proportion of CRC patients and must be recognized early.

Breast cancer stem cells, cytokine networks, and the tumor microenvironment

Many tumors, including breast cancer, are maintained by a subpopulation of cells that display stem cell properties, mediate metastasis, and contribute to treatment resistance. These cancer stem cells (CSCs) are regulated by complex interactions with the components of the tumor microenvironment - including mesenchymal stem cells, adipocytes, tumor associated fibroblasts, endothelial cells, and immune cells - through networks of cytokines and growth factors. Since these components have a direct influence on CSC properties, they represent attractive targets for therapeutic development.

Intraperitoneal administration of bevacizumab intraoperatively does not affect abdominal wound healing in rats

BACKGROUND

Bevacizumab is a monoclonal antibody targeted at vascular endothelial growth factor (VEGF) to treat advanced colorectal cancer as well as other malignancies, but the ideal time point for its administration in patients scheduled for surgery is not well defined due to serious concerns regarding possible side effects on wound healing. Therefore, we conducted an experimental study in rats to clarify this issue.

METHODS

Four groups of 10 Wistar rats each underwent a 4-cm midline laparotomy and closure of the wound in 2 layers. In the treatment groups (A and B), bevacizumab (Avastin(®)) received a single dose of 5 mg/kg i.p., and an equal amount of saline was given to the control groups (C and D). Groups A and C were sacrificed on the 7th postoperative day, and groups B and D on the 14th postoperative day. Wounds were inspected by two independent observers upon sacrifice and results were recorded; wound tissues were sent for histology to assess the degree of fibrosis and measurement of tissue hydroxyproline levels. Serum levels of endothelin-1, C-reactive protein, pro-oxidant/antioxidant balance and carbonylated proteins were also determined. For statistical analysis, the Mann-Whitney U test was used.

RESULTS

Wound healing did not differ among groups both on the 7th and the 14th postoperative days, and there was also no significant difference regarding the degree of inflammation, fibroblast proliferation and collagen synthesis, as well as hydroxyproline and biochemical marker levels among the groups.

CONCLUSIONS

Intraperitoneal bevacizumab administered intraoperatively does not significantly affect abdominal wound healing in rats.

Novel chemosensitive single-nucleotide polymorphism markers to targeted regimens in metastatic colorectal cancer

PURPOSE

Methods for predicting individual responsiveness to targeted chemotherapy are urgently needed, considering the frequent resistance and extremely high cost.

EXPERIMENTAL DESIGN

A chemosensitive single-nucleotide polymorphism (SNP) discovery schema is presented that utilizes (i) genome-wide SNP screening with a human SNP array and an in vitro chemosensitivity assay in 118 colorectal cancers, (ii) clinical association analysis in the other 98 patients who had received chemotherapy for metastatic cancer, and (iii) biological utility assessment using cell viability assays of transfected colorectal cancer (CRC) cells.

RESULTS

Nine SNPs related to bevacizumab and cetuximab regimen sensitivity were chosen during screening. Overall responses for bevacizumab regimens revealed that patients carrying the TT genotype at ANXA11 rs1049550 or at least one G allele at LINS1 rs11247226 seemed greater chemosensitive than those carrying at least one C allele or the AA genotype, respectively (P < 0.05). For cetuximab regimens, patients carrying the GG genotype at DFNB31 rs2274159 or LIFR rs3729740 seemed greater chemosensitive than those carrying at least one A allele (P = 0.025 and P = 0.07). Cytotoxicity analyses showed that all RKO and HCT116 CRC clones transfected with the G allele at LIFR rs3729740 and the C allele at ISX rs361863 were more sensitive to cetuximab regimens than those with the A and T allele, respectively (P ≤ 0.001-0.024).

CONCLUSIONS

Chemosensitive SNP markers were identified using a novel three-step process. The candidate marker LIFR rs3729740 and possibly ISX rs361863 will hopefully predict responsive patients to cetuximab regimens, although further validation is needed in large cohorts.

The development of the tumor vascular-disrupting agent ASA404 (vadimezan, DMXAA): current status and future opportunities

IMPORTANCE OF THE FIELD

Targeting tumor vasculature with antiangiogenic agents improves outcomes achieved with chemotherapy in some cancers, but toxicity limits their applicability. Tumor vascular-disrupting agents (tumor-VDAs) induce an acute collapse in tumor vascular supply; ASA404 (vadimezan, 5,6-dimethylxanthenone-4-acetic acid [DMXAA]) is the tumor-VDA most advanced in clinical development. Recent randomized trials of ASA404 in combination with chemotherapy suggested a survival advantage in NSCLC comparable to that achieved with bevacizumab, but with little additional toxicity. Phase III trials in advanced NSCLC have completed accrual, and a review of this exciting agent is timely.

AREAS COVERED IN THIS REVIEW

This review focuses on the development of ASA404 to date, its mechanisms of action, the current body of clinical research and potential avenues for therapeutic use. It includes all completed clinical trials since it entered clinical testing in 1995 through to 2009.

WHAT THE READER WILL GAIN

This review will help the reader to understand why ASA404 is unique among tumor-VDAs; the clinical trial methodology required to evaluate such agents; and its remarkable potential clinical utility.

TAKE HOME MESSAGE

ASA404 is a tumor-VDA that offers considerable potential to improve outcomes in cancer patients in combination with existing treatments.