Markers of Response to Antiangiogenic Therapies in Colorectal Cancer: Where Are We Now and What Should Be Next?

Current and emerging anti-angiogenic therapies in gastrointestinal and hepatobiliary cancers

Gastrointestinal tumours are a heterogeneous group of neoplasms that arise in the gastrointestinal tract and hepatobiliary system. Their incidence is rising globally and they currently represent the leading cause of cancer-related mortality worldwide. Anti-angiogenic agents have been incorporated into the treatment armamentarium of most of these malignancies and have improved survival outcomes, most notably in colorectal cancer and hepatocellular carcinoma. New treatment combinations with immunotherapies and other agents have led to unprecedented benefits and are revolutionising patient care. In this review, we detail the mechanisms of action of anti-angiogenic agents and the preclinical rationale underlying their combinations with immunotherapies. We review the clinical evidence supporting their use across all gastrointestinal tumours, with a particular emphasis on colorectal cancer and hepatocellular carcinoma. We discuss available biomarkers of response to these therapies and their utility in routine clinical practice. Finally, we summarise ongoing clinical trials in distinct settings and highlight the preclinical rationale supporting novel combinations.

Clinical Relevance of Viable Circulating Tumor Cells in Patients with Metastatic Colorectal Cancer: The COLOSPOT Prospective Study

Simple Summary

The analysis of circulating tumor cells (CTCs) as a “real-time liquid biopsy” in epithelial tumors for personalized medicine has received tremendous attention over the past years, with important clinical implications. In metastatic colorectal cancer (mCRC), the CellSearch^® system has already demonstrated its prognostic value and interest in monitoring treatment response, but the number of recovered CTCs remains low. In this article, we evaluate the early prognostic and predictive value of viable CTCs in patients with mCRC treated with FOLFIRI–bevacizumab with an alternative approach, the functional EPISPOT assay. This study shows that viable CTCs can be detected in patients with mCRC before and during FOLFIRI–bevacizumab treatment and that CTC detection at D₂₈ and the D₀–D₂₈ CTC kinetics evaluated with the EPISPOT assay are associated with response to treatment.

Abstract

Background: Circulating tumor cells (CTCs) allow the real-time monitoring of tumor course and treatment response. This prospective multicenter study evaluates and compares the early predictive value of CTC enumeration with EPISPOT, a functional assay that detects only viable CTCs, and with the CellSearch^® system in patients with metastatic colorectal cancer (mCRC). Methods: Treatment-naive patients with mCRC and measurable disease (RECIST criteria 1.1) received FOLFIRI–bevacizumab until progression or unacceptable toxicity. CTCs in peripheral blood were enumerated at D₀, D₁₄, D₂₈, D₄₂, and D₅₆ (EPISPOT assay) and at D₀ and D₂₈ (CellSearch^® system). Progression-free survival (PFS) and overall survival (OS) were assessed with the Kaplan–Meier method and log-rank test. Results: With the EPISPOT assay, at least 1 viable CTC was detected in 21% (D₀), 15% (D₁₄), 12% (D₂₈), 10% (D₄₂), and 12% (D₅₆) of 155 patients. PFS and OS were shorter in patients who remained positive, with viable CTCs between D₀ and D₂₈ compared with the other patients (PFS = 7.36 vs. 9.43 months, p = 0.0161 and OS = 25.99 vs. 13.83 months, p = 0.0178). The prognostic and predictive values of ≥3 CTCs (CellSearch^® system) were confirmed. Conclusions: CTC detection at D₂₈ and the D₀–D₂₈ CTC dynamics evaluated with the EPISPOT assay were associated with outcomes and may predict response to treatment.

Expressing of Recombinant VEGFR2-specific Nanobody in Baculovirus Expression System

Background

Baculovirus expression system, introduced more than 20 years ago, is considered as a useful tool for large and complex eukaryotic recombinant protein production. A baculovirus expression vector is a recombinant virus which desired foreign protein coding sequences is under control of the virus gene promoter. Baculovirus only infects insect cells and do not normally infect vertebrates therefore, they possess no risk of biological risks for human.

Objectives

The aim of this study was to recombinant expression of vascular endothelial growth factor (VEGF) reseptor-2 specific Nanobody in the baculovirus expression system.

Materials and Methods

Gene of specific Nanobody against the VEGF reseptor-2 that called 3VGR19 was cloned and expressed in baculovirus system.

Results

3VGR19 Nanobody gene was amplified by Polymerase Chain Reaction (PCR) using the specific primers, and was cloned in pFastBac HTA plasmid. DH10Bac bacteria was transformed with resulted donor plasmid. The cultured Sf9 insect cell line was transfected with recombinant bacmid, and finally, the expression and purification of 3VGR19 was confirmed in insect cells.

Conclusions

In conclusion, Transient infection of insect cells with baculovirus can be a promising technology for expression of antibody fragments.

Up-and-Coming Experimental Drug Options for Metastatic Colorectal Cancer

Colorectal cancer is one of the top causes of cancer and cancer-related deaths worldwide. The prognosis of metastatic colorectal cancer is poor and treatment options are limited. Many patients will run out of treatment options before they become medically unfit for therapy. As such, there is a need to expand upon the current understanding of disease biology as well as drug resistance mechanisms in order to create new approaches for therapy. In this review article, we will discuss the mechanistic rationale and clinical data for new drugs and therapeutic combinations under development for metastatic colorectal cancer.

Instability of Non-Standard Microsatellites in Relation to Prognosis in Metastatic Colorectal Cancer Patients

Very few data are reported in the literature on the association between elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) and prognosis in advanced colorectal cancer. Moreover, there is no information available in relation to the response to antiangiogenic treatment. We analyzed EMAST and vascular endothelial growth factor-B (VEGF-B) microsatellite status, together with standard microsatellite instability (MSI), in relation to prognosis in 141 patients with metastatic colorectal cancer (mCRC) treated with chemotherapy (CT) alone (n = 51) or chemotherapy with bevacizumab (B) (CT + B; n = 90). High MSI (MSI-H) was detected in 3% of patients and was associated with progression-free survival (PFS; p = 0.005) and overall survival (OS; p < 0.0001). A total of 8% of cases showed EMAST instability, which was associated with worse PFS (p = 0.0006) and OS (p < 0.0001) in patients treated with CT + B. A total of 24.2% of patients showed VEGF-B instability associated with poorer outcome in (p = 0.005) in the CT arm. In conclusion, our analysis indicated that EMAST instability is associated with worse prognosis, particularly evident in patients receiving CT + B.

Expression of pro-angiogenic factors as potential biomarkers in experimental models of colon cancer

PURPOSE

RAS mutational status in colorectal cancer (CRC) represents a predictive biomarker of response to anti-EGFR therapy, but to date it cannot be considered an appropriate biomarker of response to anti-VEGF therapy. To elucidate the function of K-Ras in promoting angiogenesis, the effect of conditioned media from KRAS mutated and wild type colon cancer cell lines on HUVECs tubule formation ability and the correspondent production of pro-angiogenic factors have been evaluated by a specific ELISA assay.

METHODS

Ras-activated signaling pathways were compared by western blot analysis and RTq-PCR. In addition, VEGF, IL-8, bFGF and HIF-1α expression was determined in K-RAS silenced cells. Furthermore, we conducted an observational study in a cohort of RAS mutated metastatic CRC patients, treated with first-line bevacizumab-based regimens, evaluating VEGF-A and IL-8 plasma levels at baseline, and during treatment.

RESULTS

K-RAS promotes VEGF production by cancer cell lines. At the transcriptional level, this is reflected to a K-RAS dependent HIF-1α over-expression. Moreover, the HIF-1α, VEGF and FGF expression inhibition in KRAS knocked cells confirmed these results. Within the clinical part, no statistically significant correlation has been found between progression-free survival (PFS) and VEGF-A/IL-8 levels, but we cannot exclude that these biomarkers could be further investigated as predictive or prognostic biomarkers in this setting.

CONCLUSION

Our study confirmed the direct involvement of K-Ras in promoting angiogenesis into colon cancer cell lines.

Pretreatment risk management of a novel nomogram model for prediction of thoracoabdominal extrahepatic metastasis in primary hepatic carcinoma

BACKGROUND

Extrahepatic metastasis is the independent risk factor of poor survival of primary hepatic carcinoma (PHC), and most occurs in the chest and abdomen. Currently, there is still no available method to predict thoracoabdominal extrahepatic metastasis in PHC. In this study, a novel nomogram model was developed and validated for prediction of thoracoabdominal extrahepatic metastasis in PHC, thereby conducted individualized risk management for pretreatment different risk population.

METHODS

The nomogram model was developed in a primary study that consisted of 330 consecutive pretreatment patients with PHC. Large-scale datasets were extracted from clinical practice. The nomogram was based on the predictors optimized by data dimension reduction through Lasso regression. The prediction performance was measured by the area under the receiver operating characteristic (AUROC), and calibrated to decrease the overfit bias. Individualized risk management was conducted by weighing the net benefit of different risk population via decision curve analysis. The prediction performance was internally and independently validated, respectively. An independent-validation study using a separate set of 107 consecutive patients.

RESULTS

Four predictors from 55 high-dimensional clinical datasets, including size, portal vein tumor thrombus, infection, and carbohydrate antigen 125, were incorporated to develop a nomogram model. The nomogram demonstrated valuable prediction performance with AUROC of 0.830 (0.803 in internal-validation, and 0.773 in independent-validation, respectively), and fine calibration. Individual risk probability was visually scored. Weighing the net benefit, threshold probability was classified for three-independent risk population, which was < 19.9%, 19.9-71.8% and > 71.8%, respectively. According to this classification, pretreatment risk management was based on a treatment-flowchart for individualized clinical decision-making.

CONCLUSIONS

The proposed nomogram is a useful tool for pretreatment risk management of thoracoabdominal extrahepatic metastasis in PHC for the first time, and may handily facilitate timely individualized clinical decision-making for different risk population.

Phase 1 trial of ontuxizumab (MORAb-004) in children with relapsed or refractory solid tumors: A report from the Children's Oncology Group Phase 1 Pilot Consortium (ADVL1213)

BACKGROUND

Ontuxizumab is a humanized IgG monoclonal antibody that targets the cell-surface glycoprotein endosialin (tumor endothelial marker-1[TEM-1]/CD248) found on activated mesenchymal cells and certain tumors. Ontuxizumab binding to endosialin may interfere with platelet-derived growth factor signaling, prevent tumor stroma organization, and prevent new vessel formation.

METHODS

Ontuxizumab was administered intravenously on days 1, 8, 15, and 22 of a 28-day cycle at three dose levels (4, 8, and 12 mg/kg). Further dose escalation to 16 mg/kg was planned if the maximum tolerated dose (MTD) was not reached and the ontuxizumab systemic clearance was ≥30% higher in children compared to adults. Following determination of the MTD/recommended phase 2 dose, an additional cohort of six patients (<12 years) was enrolled for further pharmacokinetics (PK) evaluation.

RESULTS

Twenty-seven eligible patients (17 male, median age 15 years, range 3-21 years) were enrolled. Twenty-two patients (neuroblastoma [5], Ewing sarcoma [4], rhabdomyosarcoma [4], and other tumors [9]) were fully evaluable for toxicity. Five patients did not complete cycle 1 due to tumor progression. Two of 10 patients experienced dose-limiting toxicity of bacteremia (n = 1) and hyponatremia (n = 1) at 12 mg/kg. Grade ≤2 fever or infusion-related reactions occurred in 10 patients. Clearance was dose dependent and within 30% of adult value at 12 mg/kg.

CONCLUSION

Ontuxizumab administered weekly at 12 mg/kg appears to be well tolerated in children with relapsed or refractory solid tumors. The PK of ontuxizumab does not appear to be significantly different in children compared to adults.

Pharmacogenomics in colorectal cancer: current role in clinical practice and future perspectives

The treatment scenario of colorectal cancer (CRC) has been evolving in recent years with the introduction of novel targeted agents and new therapeutic strategies for the metastatic disease. An extensive effort has been directed to the identification of predictive biomarkers to aid patients selection and guide therapeutic choices. Pharmacogenomics represents an irreplaceable tool to individualize patients treatment based on germline and tumor acquired somatic genetic variations able to predict drugs response and risk of toxicities. The growing knowledge of CRC molecular characteristics and complex genomic makeup has played a crucial role in identifying predictive pharmacogenomic biomarkers, while supporting the rationale for the development of new drugs and treatment combinations. Clinical validation of promising biomarkers, however, is often an issue. More recently, a deeper understanding of resistance mechanisms and tumor escape dynamics under treatment pressure and the availability of novel technologies are opening new perspectives in this field. This review aims to present an overview of current pharmacogenomic biomarkers and future perspectives of pharmacogenomics in CRC, in an evolving scenario moving from a single drug-gene interactions approach to a more comprehensive genome-wide approach, comprising genomics and epigenetics.

The role of tumor angiogenesis as a therapeutic target in colorectal cancer

INTRODUCTION

Angiogenesis is a complex process regulated by several pro- and anti-angiogenic factors, thus the loss of its fine equilibrium plays a key role in colorectal cancer (CRC) development and progression. Therapeutic agents targeting VEGF/VEGFR signaling, the main regulator of this process, proved to be effective across different treatment lines in metastatic CRC (mCRC) and contributed greatly to improve patients' survival in recent years. Areas covered: This review aimed to summarize the actual body of knowledge available on the VEGF pathway in CRC, including currently available anti-angiogenic drugs and treatment challenges, mechanisms of resistance, promising predictive biomarkers and future perspectives. Expert commentary: Angiogenesis inhibition in subsequent lines of treatment is a valid strategy in the continuum of care of mCRC patients. In this scenario, the availability of multiple agents warrants to tailor therapy to an individualized approach. However, the validation of predictive biomarkers to aid therapeutic decisions remains an issue. Intrinsic and adaptive resistance to anti-angiogenic agents comprises distinct and intertwined processes, eventually leading to treatment failure and disease progression. The expanding knowledge on the mechanisms underlying the angiogenesis pathway, different potential treatment targets and mechanisms of tumor resistance, may lead to promising new perspectives in this field.

Dynamic Biomarkers of Response to Antiangiogenic Therapies in Colorectal Cancer: A Review

Background:

Identification of clinical and molecular biomarkers to predict dynamic response or monitor in real-time the efficacy of antiangiogenic therapy represents a major point in the treatment of patients with advanced colorectal cancer. Several stu-dies have been conduced to identify some predictive biomarkers to select patients who will benefit from bevacizumab, the most widely used antiangiogenic monoclonal anti-body.

Conclusion:

After a decade since the introduction of bevacizumab, no effective predictive biomarkers are available in routine clinical practice. In this review, we summarized the potential candidate dynamic biomarkers that may play a role in this setting.

Circulating Plasma Levels of miR-20b, miR-29b and miR-155 as Predictors of Bevacizumab Efficacy in Patients with Metastatic Colorectal Cancer

Targeting angiogenesis in the treatment of colorectal cancer (CRC) is a common strategy, for which potential predictive biomarkers have been studied. miRNAs are small non-coding RNAs involved in several processes including the angiogenic pathway. They are very stable in biological fluids, which turns them into potential circulating biomarkers. In this study, we considered a case series of patients with metastatic (m) CRC treated with a bevacizumab (B)-based treatment, enrolled in the prospective multicentric Italian Trial in Advanced Colorectal Cancer (ITACa). We then analyzed a panel of circulating miRNAs in relation to the patient outcome. In multivariate analysis, circulating basal levels of hsa-miR-20b-5p, hsa-miR-29b-3p and hsa-miR-155-5p resulted in being significantly associated with progression-free survival (PFS) (p = 0.027, p = 0.034 and p = 0.039, respectively) and overall survival (OS) (p = 0.044, p = 0.024 and p = 0.032, respectively). We also observed that an increase in hsa-miR-155-5p at the first clinical evaluation was significantly associated with shorter PFS (HR 3.03 (95% CI 1.06-9.09), p = 0.040) and OS (HR 3.45 (95% CI 1.18-10.00), p = 0.024), with PFS and OS of 9.5 (95% CI 6.8-18.7) and 15.9 (95% CI 8.4-not reached), respectively, in patients with an increase ≥30% of hsa-miR-155-5p and 22.3 (95% CI 10.2-25.5) and 42.9 (24.8-not reached) months, respectively, in patients without such increase. In conclusion, our results highlight the potential usefulness of circulating basal levels of hsa-miR-20b-5p, hsa-miR-29b-3p and hsa-miR-155-5p in predicting the outcome of patients with mCRC treated with B. In addition, the variation of circulating hsa-miR-155-5p could also be indicative of the patient survival.

KRAS mutation and primary tumor location do not affect efficacy of bevacizumab-containing chemotherapy in stagae IV colorectal cancer patients

This study aims to investigate the efficacy of bevacizumab-combined chemotherapy (BCC) in Chinese stage IV colorectal cancer (CRC), and analyze the relationship between clinicopathological features with survival. Patients with stage IV CRC treated with BCC were analyzed retrospectively. 217 metastatic CRC (mCRC) patients were collected, out of which79 were right-sided CRCs and 138 were left-sided ones. Patients with Eastern Cooperative Oncology Group (ECOG) performance status ≤2, single agent chemotherapy, poor/mucous/signet ring cell component, second-and further-line of bevacizumab administration, multiple metastasis sites had comparatively worse survival. Among 141 patients with known KRAS status, 55 patients harbored KRAS mutation and 86 had wild type KRAS. The ORR and DCR were 41.9% and 78.9%, respectively, in patients with wild type KRAS, while ORR and DCR was 38.7% and 77.9%, respectively, in patients with KRAS mutation. The median PFS of patients with wild type and mutant KRAS were 8.38, and9.59 months, respectively; whereas the OS was 23.00 and 21.26 months, respectively for mCRC patients with wild-type and mutant KRAS. Cumulatively, our study indicated that BCC was effective and beneficial for Chinese stage IV CRC patients. KRAS mutation status and tumor location were not a prognostic factor for survival.

Circulating VEGF and eNOS variations as predictors of outcome in metastatic colorectal cancer patients receiving bevacizumab

Novel predictive biomarkers are needed to improve patient selection and optimize the use of bevacizumab (B) in metastatic colorectal cancer. We analyzed the potential of five circulating biomarkers to predict B efficacy and monitor response. Peripheral blood samples collected at baseline, at the first clinical evaluation and at progression were available for 129 patients enrolled in the prospective multicentric ITACa trial and randomized to receive FOLFOX4/FOLFIRI (CT) with (64 patients) or without B (65 patients). VEGF-A, eNOS, EPHB4, COX2 and HIF-1α mRNA levels were measured by qRT-PCR. Baseline marker expression levels and their modulation during therapy were analyzed in relation to objective response, progression-free survival and overall survival (OS). VEGF and eNOS expression was significantly correlated in both groups (Spearman’s correlation coefficient = 0.80; P < 0.0001 and 0.75; P < 0.0001, respectively). B-treated patients with >30% reduction in eNOS and VEGF levels from baseline to the first clinical evaluation showed better OS than the others (median OS 31.6 months, 95% CI 21.3–49.5 months and median OS 14.4 months, 95% CI 9.0–22.7 months, respectively, HR 0.38, 95% CI 0.19–0.78, P = 0.008). A reduction in eNOS and VEGF expression from baseline to the first clinical evaluation may indicate a response to B.

The role of microvessel density, lymph node metastasis, and tumor size as prognostic factors of distant metastasis in colorectal cancer

Angiogenesis is essential for tumor growth and metastasis. CD105 is reportedly a specific marker for tumor angiogenesis. It has been demonstrated that monoclonal antibodies to CD105 have high affinity for activated endothelial cells. A relationship between metastasis and microvessel density (MVD), as an indicator of neovascularization, has been identified in patients with colorectal cancer as shown by the presence of monoclonal antibodies to CD105. However, data on potentially confounding factors such as lymphatic and vascular infiltration and tumor size are lacking. We further investigated the relationship between MVD and distant metastasis, along with potentially confounding clinicopathological factors, to more precisely characterize this relationship. In this retrospective study, we analyzed colorectal cancer specimens surgically or endoscopically resected from January to September 2009. We defined MVD as the number of microvessels stained by monoclonal antibodies to CD105 per ×400 field. Selected clinicopathological factors were analyzed and stepwise multivariate logistic regression was performed to identify independent risk factors for distant metastasis. We analyzed 129 lesions. The median follow-up time was 34 months (range, 6-85 months) in patients with distant metastasis and 61 months (range, 60-86 months) in those without distant metastasis. At the time of resection or during subsequent follow-up, 32 patients had distant metastases. The MVD was significantly greater in patients with than without distant metastases (mean ± standard deviation: 10.4±4.9 vs. 7.6±3.3, P=0.008; Welch's t-test). Stepwise multivariate logistic regression indicated that MVD, regional lymph node metastasis, and tumor size were independent risk factors for distant metastases. Combining assessment of monoclonal antibodies to CD105-positive MVD with assessment of regional lymph node metastasis and tumor size may help to identify patients who need more intensive surveillance after surgery for colorectal cancer.

Unravelling the pharmacologic opportunities and future directions for targeted therapies in gastro-intestinal cancers Part 1: GI carcinomas

Until the 1990s, cytotoxic chemotherapy has been the cornerstone of medical therapy for gastrointestinal (GI) cancers. Better understanding of the molecular biology of cancer cell has led to the therapeutic revolution of targeted therapies, i.e. monoclonal antibodies or small molecule inhibitors directed against proteins that are specifically overexpressed or mutated in cancer cells. These agents being more specific to cancer cells were expected to be less toxic than cytotoxic agents. Targeted agents have provided clinical benefit in many GI cancer types. For example, antiangiogenics and anti-EGFR therapies have significantly improved survival of patients affected by metastatic colorectal cancer and have deeply changed the therapeutic strategy in this disease. However, their effects have sometimes been disappointing, due to intrinsic or acquired resistance mechanisms (e.g., RAS mutation for anti-EGFR therapies), or to an activity restricted to some tumour settings (e.g., lack of activity in other cancer types, or on the microscopic residual disease in adjuvant setting). Many studies are negative in overall population but positive in some specific patient subgroups (e.g., trastuzumab in HER2-positive gastric cancer), illustrating the importance of patient selection and early identification of predictive biomarkers of response to these therapies. We propose a comprehensive two-part review providing a panoramic approach of the successes and failures of targeted agents in GI cancers to unravel the pharmacologic opportunities and future directions for these agents in GI oncology. In this first part, we will focus on adenocarcinomas and squamous cell carcinomas, for which targeted therapies are mostly used in combination with chemotherapy.

Targeting angiogenesis in gastrointestinal tumors: current challenges

Colorectal cancer (CRC) is one of the few cancers where screening modalities are standardized, but it still remains the third leading cause of cancer related mortality. For more than a decade now, the approval of anti-angiogenic therapy has led to an increase in the rate of overall survival (OS) of patients with advanced colon cancer. The drawback of the anti-angiogenic therapy is that their effect is short-lived and many patients progress through these therapies. Various mechanisms of resistance have been hypothesized, but overcoming this has been challenging. Also, there are no standardized predictive biomarkers that could aid in selecting patients who responds to the therapy upfront. This review focuses on the basis of angiogenesis, describing the approved anti-angiogenic therapies, discusses the challenges in terms of resistance to anti-angiogenic therapy and also the role of biomarkers. In the future, hopefully newer targeted therapies, immunotherapy, combination therapies and the standardization of biomarkers may result in improved outcomes and cure rates.