Antiangiogenic Agents and Vascular Disrupting Agents for the Treatment of Lung Cancer: A Review

Vascular-immuno-phenotypic (VIP) model for locally advanced and oligo-metastatic cancer: A hypothesis

Primary Hypothesis: In cancer therapy, normalization of the vasculature, and not disruption, to facilitate the reversal of the immuno-phenotypic changes, is the sine-qua-non for cancer elimination. The triad of normalization of the vasculature, leading to the improved immunological tumour microenvironment and increased susceptibility of resistant phenotypic cancer cells (VIP model), forms the basis of this hypothesis. This article hypothesizes the absolute need for vascular normalization for the eradication of cancer. Locally advanced and oligometastatic cancers have the potential to be cured with aggressive therapy. The focus on vascular normalization its clinical relevance in this situation is essential. Most traditional approaches have focused on the elimination of cancer by targeting and disrupting vasculature. Initially, antiangiogenic drugs showed significant promise in animal experiments. However, this vascular disruption approach has not paid the expected long-term dividends in the clinical setup. However, antiangiogenics are playing a significant role when used concurrently with chemotherapy/immunotherapy. Antiangiogenics have dual temporal actions - an initial normalization effect with improved oxygenation followed by pruning of blood vessels, resulting in exaggerated hypoxia along with a rebound progression. The literature is replete with phenomena of initial vascular normalization with a paradigm shift in the immuno-phenotypic milieu of cancer as part of vascular targeting approaches. The hypothesis in this article stresses the need to have strategies to extend this normalization window or to have pre-clinical trials to optimize the dose scheduling of antiangiogenics cyclically along with chemo/targeted/immune therapy and other combination therapies. We can implement this hypothesis by a combinatorial harmonization of present-day cancer therapies in the setting of tumor vasculature integrity. In addition, based on the proposed hypothesis, the current normalization effect of antiangiogenics and newer therapy development should focus primarily on normalization of the vasculature as well as targeting hypoxia-Inducible-factor-1 alpha (HIF-1 α) in the presence of differential genetic modulation of vascular endothelial cell resistance enhancement along with cancer cell sensitization. Also, the article enumerates six supporting hypotheses supplementing the primary hypothesis.

Cell death-based treatment of lung adenocarcinoma

The most common type of lung cancer is adenocarcinoma (ADC), comprising around 40% of all lung cancer cases. In spite of achievements in understanding the pathogenesis of this disease and the development of new approaches in its treatment, unfortunately, lung ADC is still one of the most aggressive and rapidly fatal tumor types with overall survival less than 5 years. Lung ADC is often diagnosed at advanced stages involving disseminated metastatic tumors. This is particularly important for the successful development of new approaches in cancer therapy. The high resistance of lung ADC to conventional radiotherapies and chemotherapies represents a major challenge for treatment effectiveness. Here we discuss recent advances in understanding the molecular pathways driving tumor progression and related targeted therapies in lung ADCs. In addition, the cell death mechanisms induced by different treatment strategies and their contribution to therapy resistance are analyzed. The focus is on approaches to overcoming drug resistance in order to improve future treatment decisions.

Mechanisms of and strategies for overcoming resistance to anti-vascular endothelial growth factor therapy in non-small cell lung cancer

Sustained angiogenesis is a hallmark of cancer. Because of the primary role of vascular endothelial growth factors (VEGFs) and their receptors in angiogenesis, VEGF-targeted agents have been developed to inhibit these signaling processes in non-small cell lung cancer (NSCLC). However, the clinical benefits are transient and resistance often rapidly develops. Insights into the molecular mechanisms of resistance would help to develop novel strategies to improve the efficacy of antiangiogenic therapies. This review discusses the mechanisms of resistance to anti-VEGF therapy and the postulated strategies to optimize antiangiogenic therapy. A number of multitargeted tyrosine kinase inhibitors currently in phase III clinical development for NSCLC are summarized. The emerging combination of antiangiogenic therapy with tumor immunotherapy is also discussed.

Advances and Prospects in Cancer Immunotherapy

Cancer immunotherapy is a promising and effective treatment modality for patients with cancers. Cytokine, anticytokine, and antibody therapies appear to be effective in treating various forms of cancer. The human papillomavirus vaccine is protective for cervical cancer, and this discovery has paved the way to the development of cancer vaccines for other forms of virus-associated cancers such as liver cancer and Merkel cell carcinoma. Clinical trials have demonstrated that adoptive cell therapy using tumor-infiltrating lymphocytes can induce tumor regression in approximately 75% of metastatic melanoma patients, suggesting the possibility of using similar technique to effectively treat breast, lung, and renal cancers in the near future. Besides, genetically engineered T cells transduced with genes encoding specific T cell receptors and chimeric antigen receptors have been shown effective in the treatment of cancer patients. These studies suggest that combination therapies are superior choices in cancer immunotherapy for patients.

[Antiangiogenic agents: current limits in thoracic oncology]

Antiangiogenic agents appear as major therapeutic options in renal, colorectal and breast cancer. Their part in thoracic oncology is still limited today except for bevacizumab. We review the current limits of antiangiogenic agents in terms of efficacy, activity, tolerance and therapeutic strategies. Problems about predictive biomarkers and cost-effectiveness of antiangiogenic agents in thoracic oncology are also mentioned.

[Anti-angiogenic agents in the treatment of lung cancer: indications and toxicities]

Lung cancer is the leading cause of cancer-related death. Targeting the vascular endothelial growth factor (VEGF) pathways in combination with standard chemotherapy can improve response rate and survival in non-small cell lung cancer. Since October 2006, a new class of drugs targeting angiogenesis has been introduced for the treatment of advanced lung cancer. Bevacizumab, an antibody directly targeting VEGF was the first agent to be approved. Other small molecule tyrosine kinase inhibitors targeting the VEGF receptor are also active in the treatment of advanced lung cancer and are currently under development. Most of these new drugs are well tolerated though potentially significant toxicities such as haemoptysis and hypertension have been observed. This article will review these new-targeted anti-angiogenic agents with a focus on their use in lung cancer and on their important side effects.

Prognostic impact of angiogenic markers in non-small-cell lung cancer is related to tumor size

BACKGROUND

It is thought that different families of angiogenic factors stimulate angiogenesis at different stages of tumor development. Our aim was to study whether the prognostic impact of vascular endothelial growth factors (VEGFs) and receptors (VEGFRs), platelet-derived growth factors (PDGFs) and receptors (PDGFRs) and fibroblast growth factor-2 (FGF-2) were associated with tumor size in non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Tumor tissue samples were obtained from 335 patients who had undergone resection for stage I-IIIA NSCLC, and tissue microarrays (TMAs) were constructed. Immunohistochemical techniques were used to evaluate the expression of VEGF-A, VEGF-C, VEGFR-2, VEGFR-3, PDGF-A, PDGF-B, PDGFR-α, PDGFR-β, and FGF-2. Tumor size was categorized using the same cutoffs as in the 7th TNM classification for lung cancer.

RESULTS

In multivariate analysis, high VEGFR-2 (HR, 1.87, [95% CI, 1.02-3.45]; P = .043), VEGFR-3 (HR, 2.18 [95% CI, 1.28-3.71]; P = .004) and the combination of high VEGF-A and high VEGFR-2 expression (low/low vs. high/high; HR, 3.28 [95% CI, 1.47-7.31]; P = .004) were independent negative prognostic factors in T2a tumors. High PDGF-B expression (HR, 11.72 [95% CI, 3.07-44.76]; P < .001) was an independent prognostic factor in T2b tumors.

CONCLUSION

The prognostic impact of angiogenic factors depend in part on tumor size. VEGF-A/VEGFR-2 and VEGFR-3 seem to have their main impact in T2a tumors, while PDGF-B is a strong and independent prognostic factor in T2b tumors.

Targeting angiogenesis from multiple pathways simultaneously: BIBF 1120, an investigational novel triple angiokinase inhibitor

Angiogenesis is considered one of the major components of tumor progression and metastasis. Interfering with the formation and stabilization of tumor blood vessels could increase tumor response rates and may translate into improved clinical outcomes in cancer patients. The clinical efficacy demonstrated in phase III trials with bevacizumab, a monoclonal antibody that targets vascular endothelial growth factor ligand, suggests that targeting angiogenesis is a rational approach to cancer management. Agents that target additional proangiogenic intracellular signaling pathways also have the potential to contribute to our anticancer armamentarium. Novel targeted agents that have antiangiogenic properties have been developed in recent years such as sorafenib, sunitinib, vandetanib, and others. Many of them inhibit additional pathways beyond vascular endothelial growth factor signaling. One of these investigational targeted agents is a triple angiokinase inhibitor known as BIBF 1120. This compound targets not only vascular endothelial growth factor receptors, but also fibroblast growth factor receptors, and platelet-derived growth factor receptors. The preliminary clinical efficacy of BIBF 1120 is discussed in the context of the most relevant clinical data in several malignancies including non-small cell lung cancer.