Generation and functional characterization of a single-chain variable fragment (scFv) of the anti-FGF2 3F12E7 monoclonal antibody.

Single-chain variable fragments (scFvs) are small-sized artificial constructs composed of the immunoglobulin heavy and light chain variable regions connected by a peptide linker. We have previously described an anti-fibroblast growth factor 2 (FGF2) immunoglobulin G (IgG) monoclonal antibody (mAb), named 3F12E7, with notable antitumor potential revealed by preclinical assays. FGF2 is a known angiogenesis-associated molecule implicated in tumor progression. In this report, we describe a recombinant scFv format for the 3F12E7 mAb. The results demonstrate that the generated 3F12E7 scFv, although prone to aggregation, comprises an active anti-FGF2 product that contains monomers and small oligomers. Functionally, the 3F12E7 scFv preparations specifically recognize FGF2 and inhibit tumor growth similar to the corresponding full-length IgG counterpart in an experimental model. In silico molecular analysis provided insights into the aggregation propensity and the antigen-recognition by scFv units. Antigen-binding determinants were predicted outside the most aggregation-prone hotspots. Overall, our experimental and prediction dataset describes an scFv scaffold for the 3F12E7 mAb and also provides insights to further engineer non-aggregated anti-FGF2 scFv-based tools for therapeutic and research purposes.

Exploring the Immunological Mechanisms Underlying the Anti-vascular Endothelial Growth Factor Activity in Tumors.

Several studies report the key role of the vascular endothelial growth factor (VEGF) signaling on angiogenesis and on tumor growth. This has led to the development of a number of VEGF-targeted agents to treat cancer patients by disrupting the tumor blood vessel supply. Of them, bevacizumab, an FDA-approved humanized monoclonal antibody against VEGF, is the most promising. Although the use of antibodies targeting the VEGF pathway has shown clinical benefits associated with a reduction in the tumor blood vessel density, the inhibition of VEGF-driven vascular effects is only part of the functional mechanism of these therapeutic agents in the tumor ecosystem. Compelling reports have demonstrated that VEGF confers, in addition to the activation of angiogenesis-related processes, immunosuppressive properties in tumors. It is also known that structural remodeling of the tumor blood vessel bed by anti-VEGF approaches affect the influx and activation of immune cells into tumors, which might influence the therapeutic results. Besides that, part of the therapeutic effects of antiangiogenic antibodies, including their role in the tumor vascular network, might be triggered by Fc receptors in an antigen-independent manner. In this mini-review, we explore the role of VEGF inhibitors in the tumor microenvironment with focus on the immune system, discussing around the functional contribution of both bevacizumab's Fab and Fc domains to the therapeutic results and the combination of bevacizumab therapy with other immune-stimulatory settings, including adjuvant-based vaccine approaches.

Crataeva tapia bark lectin (CrataBL) is a chemoattractant for endothelial cells that targets heparan sulfate and promotes in vitro angiogenesis.

Formation of new blood vessels from preexisting ones, a process known as angiogenesis, is one of the limiting steps for success in treatment of ischemic disorders. Therefore, efforts to understanding and characterize new agents capable to stimulate neovascularization are a worldwide need. Crataeva tapia bark lectin (CrataBL) has been shown to have chemoattractant properties for endothelial cells through the stimulation of migration and invasiveness of human umbilical vein endothelial cells (HUVEC) because it is a positively charged protein with high affinity to glycosaminoglycan. In addition, CrataBL increased the production of chondroitin and heparan sulfate in endothelial cells. These findings orchestrated specific adhesion on collagen I and phosphorylation of tyrosine kinase receptors, represented by vascular endothelial growth factor receptor-2 (VEGFR-2) and fibroblast growth factor receptor (FGFR), whose downstream pathways trigger the angiogenic cascade increasing cell viability, cytoskeleton rearrangement, cell motility, and tube formation. Moreover, CrataBL inhibited the activity of matrix metalloproteases type 2 (MMP-2), a protein related to tissue remodeling. Likewise, CrataBL improved wound healing and increased the number of follicular structures in lesioned areas produced in the dorsum-cervical region of C57BL/6 mice. These outcomes altogether indicate that CrataBL is a pro-angiogenic and healing agent.

Impact of human cytomegalovirus on glioblastoma cell viability and chemotherapy treatment.

The relationship between human cytomegalovirus (HCMV) and tumours has been extensively investigated, mainly in glioblastoma multiforme (GBM), a malignant tumour of the central nervous system with low overall survival rates. Several reports have demonstrated the presence of HCMV in GBM, although typically restricted to a low number of cells, and studies have indicated that viral proteins have the ability to dysregulate cellular processes and increase tumour malignancy. Treatment of GBM involves the use of the chemotherapeutic agents temozolomide (TMZ) and carmustine (bis-chloroethylnitrosourea, BCNU), which lead to the attachment of adducts to the DNA backbone, causing errors during replication and consequent cell death. It is known that HCMV infection can modulate DNA repair pathways, but what effects the virus may exhibit during chemotherapy are unknown. Here we approach this question by analysing HCMV infection and viral protein accumulation in GBM cell lines with different genotypes and their response to TMZ and BCNU in the presence of the virus. We demonstrate that A172, TP365MG and U251MG GBM cells are efficiently infected by both low-passage (TB40E) and high-passage (AD169) HCMV strains. However, the GBM cell lines vary widely in their permissiveness to viral gene expression and exhibit very different patterns of immediate early, early and late protein accumulation. HCMV reduces the viability of permissive GBM cells in a multiplicity-dependent manner in both the absence and presence of TMZ or BNCU. In sum, we demonstrate that GBM cell lines are equally susceptible but differentially permissive to infection by both low- and high-passage strains of HCMV. This observation not only indicates that viral replication is largely controlled by cellular factors in this system, but also provides a possible explanation for why viral gene products are only found in a subset of cells in GBM tumours. Furthermore, we conclude that the virus does not confer increased resistance to chemotherapeutic drugs in various GBM cell lines, but instead reduces tumour cell viability. These results highlight that the oncomodulatory potential of HCMV is not limited to cancer-promoting activities, but also includes adverse effects on tumour cell proliferation or survival.

Anti-bevacizumab idiotype antibody vaccination is effective in inducing vascular endothelial growth factor-binding response, impairing tumor outgrowth.

Tumors require blood supply and, to overcome this restriction, induce angiogenesis. Vascular endothelial growth factor (VEGF) plays an important role in this process, which explains the great number of antiangiogenic therapies targeting VEGF. The research and development of targeted therapy has led to the approval of bevacizumab, a humanized anti-VEGF monoclonal antibody (mAb), in clinical settings. However, side effects have been reported, usually as a consequence of bolus-dose administration of the antibody. This limitation could be circumvented through the use of anti-idiotype (Id) antibodies. In the present study, we evaluated the efficacy of an active VEGF-binding immune response generated by an anti-bevacizumab idiotype mAb, 10.D7. The 10.D7 anti-Id mAb vaccination led to detectable levels of VEGF-binding anti-anti-Id antibodies. In order to examine whether this humoral immune response could have implications for tumor development, 10.D7-immunized mice were challenged with B16-F10 tumor cells. Mice immunized with 10.D7 anti-Id mAb revealed reduced tumor growth when compared to control groups. Histological analyses of tumor sections from 10.D7-immunized mice showed increased necrotic areas, decreased CD31-positive vascular density and reduced CD68-positive cell infiltration. Our results encourage further therapeutic studies, particularly if one considers that the anti-Id therapeutic vaccination maintains stable levels of VEGF-binding antibodies, which might be useful in the control of tumor relapse.

Blocking FGF2 with a new specific monoclonal antibody impairs angiogenesis and experimental metastatic melanoma, suggesting a potential role in adjuvant settings.

Compelling evidence suggests that fibroblast growth factor 2 (FGF2), overexpressed in melanomas, plays an important role in tumor growth, angiogenesis and metastasis. In this study, we evaluated the therapeutic use of a new anti-FGF2 monoclonal antibody (mAb), 3F12E7, using for that the B16-F10 melanoma model. The FGF2 neutralizing effect of this antibody was certified by in vitro assays, which allowed the further track of its possible in vivo application. 3F12E7 mAb could be retained in B16-F10 tumors, as shown by antibody low-pH elution and nuclear medicine studies, and also led to reduction in number and size of metastatic foci in lungs, when treatment starts one day after intravenous injection of B16-F10 cells. Such data were accompanied by decreased CD34(+) tumor vascular density and impaired subcutaneous tumor outgrowth. Treatments starting one week after melanoma cell intravenous injection did not reduce tumor burden, remaining the therapeutic effectiveness restricted to early-adopted regimens. Altogether, the presented anti-FGF2 3F12E7 mAb stands as a promising agent to treat metastatic melanoma tumors in adjuvant settings.