Vaccine-induced ErbB (EGFR/HER2)-specific immunity in spontaneous canine cancer

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Spontaneous dog cancers closely resemble human cancer.

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Dogs with EGFR associated tumors were immunized with an EGFR/HER2 peptide vaccine.

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EGFR peptide vaccinated dogs developed anti-EGFR/HER2 antibodies.

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Vaccinated dogs have anti-EGFR antibody and T cells infiltrating tumors.

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Vaccinated dogs with osteosarcoma had tumor regression and increased survival.

Epidermal Growth Factor Receptor (EGFR) is overexpressed on a number of human cancers, and often is indicative of a poor outcome. Treatment of EGFR/HER2 overexpressing cancers includes monoclonal antibody therapy (cetuximab/trastuzumab) either alone or in conjunction with other standard cancer therapies. While monoclonal antibody therapy has been proven to be efficacious in the treatment of EGFR/HER2 overexpressing tumors, drawbacks include the lack of long-lasting immunity and acquired resistance to monoclonal therapy. An alternative approach is to induce a polyclonal anti-EGFR/HER2 tumor antigen response by vaccine therapy. In this phase I/II open-label study, we examined anti-tumor immunity in companion dogs with spontaneous EGFR expressing tumors. Canine cancers represent an outbred population in which the initiation, progression of disease, mutations and growth factors closely resemble that of human cancers. Dogs with EGFR expressing tumors were immunized with a short peptide of the EGFR extracellular domain with sequence homology to HER2. Serial serum analyses demonstrated high titers of EGFR/HER2 binding antibodies with biological activity similar to that of cetuximab and trastuzumab. Canine antibodies bound both canine and human EGFR on tumor cell lines and tumor tissue. CD8 T cells and IgG deposition were evident in tumors from immunized dogs. The antibodies inhibited EGFR intracellular signaling and inhibited tumor growth in vitro. Additionally, we illustrate objective responses in reducing tumors at metastatic sites in host animals. The data support the approach of amplifying anti-tumor immunity that may be relevant in combination with other immune modifying therapies such as checkpoint inhibitors.

Recombinant canine basic fibroblast growth factor-induced differentiation of canine bone marrow mesenchymal stem cells into voltage- and glutamate-responsive neuron-like cells

Introduction

Basic fibroblast growth factor (bFGF) is a promising cytokine in regenerative therapy for spinal cord injury. In this study, recombinant canine bFGF (rc-bFGF) was synthesized for clinical use in dogs, and the ability of rc-bFGF to differentiate canine bone marrow mesenchymal stem cells (BMSCs) into functional neurons was investigated.

Methods

The rc-bFGF was synthesized using a wheat germ cell-free protein synthesis system. The expression of rc-bFGF mRNA in the purification process was confirmed using a reverse transcription-polymerase chain reaction (RT-PCR). Western blotting was performed to confirm the antigenic property of the purified protein. To verify function of the purified protein, phosphorylation of extracellular signal-regulated kinase (ERK) was examined by in vitro assay using HEK293 cells. To compare the neuronal differentiation capacity of canine BMSCs in response to treatment with rc-bFGF, the cells were divided into the following four groups: control, undifferentiated, rh-bFGF, and rc-bFGF groups. After neuronal induction, the percentage of cells that had changed to a neuron-like morphology and the mRNA expression of neuronal markers were evaluated. Furthermore, to assess the function of the canine BMSCs after neuronal induction, changes in the intracellular Ca²⁺ concentrations after stimulation with KCl and l-glutamate were examined.

Results

The protein synthesized in this study was rc-bFGF and functioned as bFGF, from the results of RT-PCR, western blotting, and the expression of pERK in HEK293 cells. Canine BMSCs acquired a neuron-like morphology and expressed mRNAs of neuronal markers after neuronal induction in the rh-bFGF and the rc-bFGF groups. These results were more marked in the rc-bFGF group than in the other groups. Furthermore, an increase in intracellular Ca²⁺ concentrations was observed after the stimulation of KCl and l-glutamate in the rc-bFGF group, same as in the rh-bFGF group.

Conclusions

A functional rc-bFGF was successfully synthesized, and rc-bFGF induced the differentiation of canine BMSCs into voltage- and glutamate-responsive neuron-like cells. Our purified rc-bFGF may contribute, on its own, or in combination with canine BMSCs, to regenerative therapy for spinal cord injury in dogs.

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Functional rc-bFGF was successfully synthesized.

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rc-bFGF induced the differentiation of canine BMSCs into neuron-like cells.

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rc-bFGF may aid in regenerative therapy of spinal cord injury in dogs.