Belinda Sánchez

Induction of Immunogenic Apoptosis by Blockade of Epidermal Growth Factor Receptor Activation with a Specific Antibody

Despite promising results in the use of anti-epidermal growth factor receptor (EGFR) Abs for cancer therapy, several issues remain to be addressed. An increasing emphasis is being placed on immune effector mechanisms. It has become clear for other Abs directed to tumor targets that their effects involve the adaptive immunity, mainly by the contribution of Fc region-mediated mechanisms. Given the relevance of EGFR signaling for tumor biology, we wonder whether the oncogene inhibition could contribute to Ab-induced vaccine effect. In a mouse model in which 7A7 (an anti-murine EGFR Ab) and AG1478 (an EGFR-tyrosine kinase inhibitor) displayed potent antimetastatic activities, depletion experiments revealed that only in the case of the Ab, the effect was dependent on CD4+ and CD8+ T cells. Correspondingly, 7A7 administration elicited a remarkable tumor-specific CTL response in hosts. Importantly, experiments using 7A7 F(ab′)2 suggested that in vivo Ab-mediated EGFR blockade may play an important role in the linkage with adaptive immunity. Addressing the possible mechanism involved in this effect, we found quantitative and qualitative differences between 7A7 and AG1478-induced apoptosis. EGFR blocking by 7A7 not only prompted a higher proapoptotic effect on tumor metastases compared with AG1478, but also was able to induce apoptosis with immunogenic potential in an Fc-independent manner. As expected, 7A7 but not AG1478 stimulated exposure of danger signals on tumor cells. Subcutaneous injection of 7A7-treated tumor cells induced an antitumor immune response. This is the first report, to our knowledge, of a tumor-specific CTL response generated by Ab-mediated EGFR inhibition, suggesting an important contribution of immunogenic apoptosis to this effect.

7A7 MAb: A New Tool for the Pre-Clinical Evaluation of EGFR-Based Therapies

The epidermal growth factor receptor (EGFR) is highly expressed in many types of epithelial tumors. EGFR overexpression has been associated with an advanced stage of the disease, with resistance to standard therapies, and, for certain tumors, with poor patient prognosis. As a result, EGFR has been considered a meaningful target in anti-tumor strategies. Active and passive immunotherapies blocking EGFR and its ligands have been explored. But for successful pre-clinical evaluation of these approaches, well-established murine tumor models are not available and highly desirable. We described, for the first time, the generation and characterization of an anti-murine EGFR extracellular domain monoclonal antibody (7A7 MAb) (IgG1). 7A7 was generated by immunization of Balb/c mice with the recombinant extracellular domain of murine EGFR (rECD-mEGFR). 7A7 recognized an epitope present in the amino acidic core of the antigen and is cross-reactive with the human EGFR. Interestingly, this MAb was able to specifically bind EGFR at the cell surface, allowing the assessment of its differential expression in a panel of murine cells. Noteworthy, in a preliminary immunohistochemical study with 7A7 MAb, recognition of Balb/c mice skin sections and EGFR-positive tumors were observed. We concluded that 7A7 MAb is a valuable tool for EGFR-based therapeutic pre-clinical studies.

Metastatic Lymphangiosarcoma in a Horse

A lymphangiosarcoma with metastases was found in a horse that presented with respiratory distress and edema in the ventral thorax and abdomen. The necropsy revealed diffuse edema in the subcutaneous connective tissue. Mediastinal, mesenteric, iliac, and renal lymph nodes were enlarged and white with soft, yellowish necrotic areas. Histologic examination revealed numerous channels and disorganized vessels lined by large polyhedral, polymorphic cells. Tumor metastases were observed in the spleen, lungs, and kidneys. Immunohistochemical evaluation of the tumor cells demonstrated positive staining for factor VIII, vimentin, and keratin. Laminin was scarce, and collagen IV staining was negative, consistent with a discontinuous or absent basement membrane.

Comparative in vitro and experimental in vivo studies of the anti-epidermal growth factor receptor antibody nimotuzumab and its aglycosylated form produced in transgenic tobacco plants.

A broad variety of foreign genes can be expressed in transgenic plants, which offer the opportunity for large-scale production of pharmaceutical proteins, such as therapeutic antibodies. Nimotuzumab is a humanized anti-epidermal growth factor receptor (EGFR) recombinant IgG1 antibody approved in different countries for the treatment of head and neck squamous cell carcinoma, paediatric and adult glioma, and nasopharyngeal and oesophageal cancers. Because the antitumour mechanism of nimotuzumab is mainly attributed to its ability to interrupt the signal transduction cascade triggered by EGF/EGFR interaction, we have hypothesized that an aglycosylated form of this antibody, produced by mutating the N(297) position in the IgG(1) Fc region gene, would have similar biochemical and biological properties as the mammalian-cell-produced glycosylated counterpart. In this paper, we report the production and characterization of an aglycosylated form of nimotuzumab in transgenic tobacco plants. The comparison of the plantibody and nimotuzumab in terms of recognition of human EGFR, effect on tyrosine phosphorylation and proliferation in cells in response to EGF, competition with radiolabelled EGF for EGFR, affinity measurements of Fab fragments, pharmacokinetic and biodistribution behaviours in rats and antitumour effects in nude mice bearing human A431 tumours showed that both antibody forms have very similar in vitro and in vivo properties. Our results support the idea that the production of aglycosylated forms of some therapeutic antibodies in transgenic plants is a feasible approach when facing scaling strategies for anticancer immunoglobulins.

Effects of an epidermal growth factor receptor-based cancer vaccine on wound healing and inflammation processes in murine experimental models.

Anti‐epidermal growth factor receptor (EGFR) therapies have been proven clinically effective for a variety of epithelial tumours. Vaccination of mice with the extracellular domain (ECD) of autologous EGFR overcomes the tolerance to self‐EGFR and has antimetastatic effect on EGFR+ tumour. Because EGF/EGFR‐signalling plays an important role in the inflammation stage of wound healing, the main objective of this study was to explore the possible role of murine (m) EGFR‐ECD vaccine in the croton‐oil‐induced ear oedema and wound healing process in mice as autologous experimental models, mimicking the possible post‐surgical wound complication in patients treated with human EGFR‐ECD/VSSP vaccine. Mice were intramuscularly immunised four times; biweekly with the mEGFR‐ECD/VSSP/Mont. Seven days later, an 8 mm diameter, full‐thickness skin wound was created on the back of each animal. Immunisation induced a strong specific humoral response against the mEGFR‐ECD protein and a DTH dose–response curve but interestingly, animals treated with mEGFR‐ECD/VSSP/Mont had similar inflammatory and healing speed responses compared to control ones. These data suggest that application of mEGFR‐ECD/VSSP vaccine as a therapeutic approach in cancer patients could not elicit a poor healing process after surgery.

Linking oncogenesis and immune system evasion in acquired resistance to EGFR-targeting antibodies Lessons from a preclinical model

Searching for biomarkers that associated with the acquired resistance of malignant cells to epidermal growth factor receptor (EGFR)-targeting monoclonal antibodies is crucial to improve the clinical benefits of these therapeutic agents. We have recently demonstrated that molecular alterations in both oncogenic and immunological pathways may be responsible for such an insensitivity. Our findings suggest that a combination of targeted anticancer agents and immunomodulatory drugs may be useful for overcoming the acquired resistance of cancer cells to EGFR-specific monoclonal antibodies.

Nimotuzumab: beyond the EGFR signaling cascade inhibition

One of the most known oncogenes is the epidermal growth factor receptor (EGFR) family. It activates multiple signaling cascades that promote carcinogenesis and immune evasion. Therefore, these molecules have been extensively targeted in cancer immunotherapy. Beyond EGFR signaling cascade inhibition, some of these agents are able to induce T-cell activation, transforming a passive therapy into a vaccine-like effect. Nimotuzumab is an IgG1 humanized monoclonal antibody directed against the extracellular domain of the EGFR blocking the binding to its ligands. It possesses unique pharmacodynamic properties, which allow treating patients for long-term periods and with very low toxicity. Based on its clinical effect, nimotuzumab has been approved in Cuba and abroad for the treatment of different epithelial tumors. Recently, new potential mechanisms of action of nimotuzumab involving the activation of the innate and adaptive immune response have been reported. This review summarizes the main properties of nimotuzumab in comparison with other EGFR-specific monoclonal antibodies, highlighting its capacity to activate an effective immune response. In addition, differential clinical effects of this antibody and ongoing clinical trials to deeply characterize the biomarkers of clinical benefit are shown.