Characterization of 7A7, an anti-mouse EGFR monoclonal antibody proposed to be the mouse equivalent of cetuximab

Establishment of head and neck squamous cell carcinoma mouse models for cetuximab resistance and sensitivity

Aim: Acquired resistance to the targeted agent cetuximab poses a significant challenge in finding effective anti-cancer treatments for head and neck squamous cell carcinoma (HNSCC). To accurately study novel combination treatments, suitable preclinical mouse models for cetuximab resistance are key yet currently limited. This study aimed to optimize an acquired cetuximab-resistant mouse model, with preservation of the innate immunity, ensuring intact antibody-dependent cellular cytotoxicity (ADCC) functionality. Methods: Cetuximab-sensitive and acquired-resistant HNSCC cell lines, generated in vitro, were subcutaneously engrafted in Rag2 knock-out (KO), BALB/c Nude and CB17 Scid mice with/without Matrigel or Geltrex. Once tumor growth was established, mice were intraperitoneally injected twice a week with cetuximab for a maximum of 3 weeks. In addition, immunohistochemistry was used to evaluate the tumor and its microenvironment. Results: Despite several adjustments in cell number, cell lines and the addition of Matrigel, Rag2 KO and BALB/C Nude mice proved to be unsuitable for xenografting our HNSCC cell lines. Durable tumor growth of resistant SC263-R cells could be induced in CB17 Scid mice. However, these cells had lost their resistance phenotype in vivo. Immunohistochemistry revealed a high infiltration of macrophages in cetuximab-treated SC263-R tumors. FaDu-S and FaDu-R cells successfully engrafted into CB17 Scid mice and maintained their sensitivity/resistance to cetuximab. Conclusion: We have established in vivo HNSCC mouse models with intact ADCC functionality for cetuximab resistance and sensitivity using the FaDu-R and FaDu-S cell lines, respectively. These models serve as valuable tools for investigating cetuximab resistance mechanisms and exploring novel drug combination strategies.

A fluorescent photoimmunoconjugate for imaging of cholesteatoma

Cholesteatoma is a potentially serious complication of chronic ear infections and requires surgical intervention for definitive management. Long-term complications include a frequent need for repeat surgical intervention for disease recurrence, and techniques to improve efficacy of single-stage surgery are an important area of continued research. This study investigates a novel application of the photosensitizer immune conjugate (PIC) cetuximab-benzoporphyrin derivative (Cet-BPD) for in vitro localization of human cholesteatoma tissue, coupled with an in vivo safety study for middle ear application of Cet-BPD in a murine model. In fresh human cholesteatoma tissues, Cet-BPD demonstrates selective localization to the hyperplastic squamous cell tissue associated with cholesteatoma, without localizing to other tissues such as middle ear mucosa. Applied to the murine middle ear, Cet-BPD does not demonstrate any deleterious effect on murine hearing when assessed by any of auditory brainstem response (ABR) thresholds, distortion product otoacoustic emission thresholds, or ABR wave I amplitudes. These findings demonstrate the technical promise and encouraging safety profile for the use of PICs for intraoperative localization and treatment of cholesteatoma.

Restoring the Immunity in the Tumor Microenvironment: Insights into Immunogenic Cell Death in Onco-Therapies

Immunogenic cell death (ICD) elicited by cancer therapy reshapes the tumor immune microenvironment. A long-term adaptative immune response can be initiated by modulating cell death by therapeutic approaches. Here, the major hallmarks of ICD, endoplasmic reticulum (ER) stress, and damage-associated molecular patterns (DAMPs) are correlated with ICD inducers used in clinical practice to enhance antitumoral activity by suppressing tumor immune evasion. Approaches to monitoring the ICD triggered by antitumoral therapeutics in the tumor microenvironment (TME) and novel perspective in this immune system strategy are also reviewed to give an overview of the relevance of ICD in cancer treatment.

Is Tumor Cell Specificity Distinct from Tumor Selectivity In Vivo?: A Quantitative NIR Molecular Imaging Analysis of Nanoliposome Targeting

The significance and ability for receptor targeted nanoliposomes (tNLs) to bind to their molecular targets in solid tumors in vivo has been questioned, particularly as the efficiency of their tumor accumulation and selectivity is not always predictive of their efficacy or molecular specificity. This study presents, for the first time, in situ NIR molecular imaging-based quantitation of the in vivo specificity of tNLs for their target receptors, as opposed to tumor selectivity, which includes influences of enhanced tumor permeability and retention. Results show that neither tumor delivery nor selectivity (tumor-to-normal ratio) of cetuximab and IRDye conjugated tNLs correlate with EGFR expression in U251, U87 and 9L tumors, and in fact underrepresent their imaging-derived molecular specificity by up to 94.2%. Conversely, their in vivo specificity, which we quantify as the concentration of tNL-reported tumor EGFR provided by NIR molecular imaging, correlates positively with EGFR expression levels in vitro and ex vivo (Pearson's r= 0.92 and 0.96, respectively). This study provides a unique opportunity to address the problematic disconnect between tNL synthesis and in vivo specificity. The findings encourage their continued adoption as platforms for precision medicine, and facilitates intelligent synthesis and patient customization in order to improve safety profiles and therapeutic outcomes.

IFN-γ Critically Enables the Intratumoural Infiltration of CXCR3+ CD8+ T Cells to Drive Squamous Cell Carcinoma Regression

Simple Summary

Cutaneous squamous cell carcinoma (SCC) is prevalent in aged individuals and individuals with compromised or weakened immune systems, indicating a close association between immune function and SCC control. The aim of our study was to uncover the identity of key immune subsets that mediate SCC control, and to elucidate the mechanistic role of the proinflammatory cytokine Interferon-gamma in this process. We established a SCC regressor model, which we used to determine that: (1) CD8⁺ T cells, not CD4⁺ T cells or NK cells, are essential for SCC regression; (2) the neutralisation of Interferon-gamma prevents CD8⁺ T cell infiltration and SCC regression; (3) CD8⁺ T cell migration into SCC critically depends upon Interferon-gamma-induced chemokine expression. Thus, our model can be used to understand the key immune mechanisms involved in SCC regression, which will support targeted investigations into the integrity of these mechanisms in patients with progressive disease.

Abstract

Ultraviolet (UV) radiation-induced tumours carry a high mutational load, are highly immunogenic, and often fail to grow when transplanted into normal, syngeneic mice. The aim of this study was to investigate factors critical for the immune-mediated rejection of cutaneous squamous cell carcinoma (SCC). In our rejection model, transplanted SCC establish and grow in mice immunosuppressed with tacrolimus. When tacrolimus is withdrawn, established SCC tumours subsequently undergo immune-mediated tumour rejection. Through the depletion of individual immune subsets at the time of tacrolimus withdrawal, we established a critical role for CD8⁺ T cells, but not CD4⁺ T cells, γδ T cells, or NK cells, in driving the regression of SCC. Regression was critically dependent on IFN-γ, although IFN-γ was not directly cytotoxic to SCC cells. IFN-γ-neutralisation abrogated SCC regression, significantly reduced CD8⁺ T cell-infiltration into SCC, and significantly impaired the secretion of CXCL9, CXCL10 and CCL5 within the tumour microenvironment. A strong positive correlation was revealed between CXCL10 expression and CD8⁺ T cell abundance in tumours. Indeed, blockade of the CXCL10 receptor CXCR3 at the time of tacrolimus withdrawal prevented CD8⁺ T cell infiltration and the regression of SCC. Chimeric models revealed an important role for immune cells as producers of IFN-γ, but not as recipients of IFN-γ signals via the IFN-γ receptor. Together, these findings suggest a key role for IFN-γ in driving the expression of chemokines within the tumour environment essential for the destruction of established SCC by CD8⁺ T cells.

Cetuximab Exhibits Sex Differences in Lymphatic Exposure after Intravenous Administration in Rats in the Absence of Differences in Plasma Exposure

PURPOSE

The aim of this work was to identify whether biochemical and physiological sources of mAb pharmacokinetic sex-effects could be identified in the rat model where target-mediated disposition is avoided.

METHODS

Plasma and lymphatic pharmacokinetics of the humanised anti-EGFR antibody cetuximab, along with potential physiological and biochemical drivers of pharmacokinetic sex differences, were examined in male and female rats. Cetuximab was used as a model mAb since plasma clearance is slower in female patients.

RESULTS

When plasma concentrations were normalised to dose, female rats displayed slower plasma clearance than males, but no significant differences were observed in liver and spleen biodistribution. Sex differences in apparent plasma clearance, however, were abolished after normalisation to body weight, surface area or fat-free mass. Significant sex differences were observed in plasma testosterone, endogenous IgG and fat free mass, but did not correlate with apparent clearance. Females did, however, show two-fold higher lymphatic exposure compared to males.

CONCLUSIONS

These data suggested that mAbs more efficiently access lymph in females, but this does not affect plasma pharmacokinetics or biodistribution. Further, the data suggest that sex differences observed in humans could be a function of antigen density.

Targeted Delivery of 111In Into the Nuclei of EGFR Overexpressing Cells via Modular Nanotransporters With Anti-EGFR Affibody

Since cell nucleus is one of the most vulnerable compartments, the maximum therapeutic effect from a variety of locally acting agents, such as photosensitizers, alfa-emitters, Auger electron emitters, will be expected when they get there. Therefore, the targeted delivery of these agents into the nuclei of target tumor cells is necessary for their anticancer effects and minimization of side effects. Modular nanotransporters (MNT) are artificial polypeptides comprising several predefined modules that recognize target cell, launching their subsequent internalization, escape from endosomes, and transport the drug load to the nucleus. This technology significantly enhances the cytotoxicity of locally acting drugs in vitro and in vivo. Epidermal growth factor receptors (EGFR) are useful molecular targets as they are overexpressed in glioblastoma, head-and-neck cancer, bladder cancer, and other malignancies. Here, we examined the possibility of using internalizable anti-EGFR affibody as an EGFR-targeting MNT module for drug transport into the cancer cell nuclei. It binds to both murine and human EGFR facilitating preclinical studies. We showed that MNT with affibody on the N-terminus (MNT_N-affibody) effectively delivered the Auger electron emitter ¹¹¹In to target cell nuclei and had pronounced cytotoxic efficacy against EGFR-overexpressing human A431 epidermoid carcinoma cells. Using EGFR-expressing human adenocarcinoma MCF-7 cells, we demonstrated that in contrast to MNT with N-terminal epidermal growth factor (EGF), MNT_N-affibody and MNT with EGF on the C-terminus did not stimulate cancer cell proliferation.

Bacillus anthracis Protective Antigen Shows High Specificity for a UV Induced Mouse Model of Cutaneous Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) accounts for the majority of non-melanoma skin cancer related deaths, particularly in immunosuppressed persons. Identification of biomarkers that could be used to identify or treat SCC would be of significant benefit. The anthrax toxin receptors, Tumor Endothelial Marker 8 (TEM8) and Capillary Morphogenesis Gene 2 (CMG2), are endothelial receptors involved in extracellular matrix homeostasis and angiogenesis that are selectively upregulated on numerous tumors. One method of targeting these receptors is Protective Antigen (PA), a protein produced by B. anthracis that mediates binding and translocation of anthrax toxins into cells. PA targeted toxins have been demonstrated to selectively inhibit tumor growth and angiogenesis, but tumor selectivity of PA is currently unknown. In this work fluorescently labeled PA was shown to maintain receptor dependent binding and internalization in vitro. Utilizing a human papillomavirus transgenic mouse model that develops cutaneous SCC in response to ultraviolet irradiation we identified tumor uptake of PA in vivo. The intravenously administered PA resulted in tumor specific localization, with exclusive tumor detection 24 h post injection. Ex vivo analysis identified significantly higher fluorescence in the tumor compared to adjacent healthy tissue and major clearance organs, demonstrating low non-specific uptake and rapid clearance. While both TEM8 and CMG2 were observed to be overexpressed in SCC tumor sections compared to control skin, the intravenously administered PA was primarily co-localized with TEM8. These results suggest that PA could be systemically administered for rapid identification of cutaneous SCC, with potential for further therapeutic development.