Enhancement of macrophage invasion of tumors by administration of chemotactic factor-antitumor antibody conjugates

Selective Display of a Chemoattractant Agonist on Cancer Cells Activates the Formyl Peptide Receptor 1 on Immune Cells

Current immunotherapeutics often work by directing components of the immune system to recognize biomarkers on the surface of cancer cells to generate an immune response. However, variable changes in biomarker distribution and expression can result in inconsistent patient response. The development of a more universal tumor-homing strategy has the potential to improve selectivity and extend therapy to cancers with decreased expression or absence of specific biomarkers. Here, we designed a bifunctional agent that exploits the inherent acidic microenvironment of most solid tumors to selectively graft the surface of cancer cells with a formyl peptide receptor ligand (FPRL). Our approach is based on the pH(Low) insertion peptide (pHLIP), a unique peptide that selectively targets tumors in vivo by anchoring to cancer cells in a pH-dependent manner. We establish that selectively remodeling cancer cells with a pHLIP-based FPRL activates formyl peptide receptors on recruited immune cells, potentially initiating an immune response towards tumors.

A nano-innate immune system activator for cancer therapy in a 4T1 tumor-bearing mouse model

Background

Harnessing the immune system to fight cancer has led to prominent clinical successes. Strategies to stimulate innate immune effectors are attracting considerable interest in cancer therapy. Here, through conjugating multivalent Fc fragments onto the surface of mesoporous silica nanoparticles (MSN), we developed a nanoparticle-based innate immune system activator (NISA) for breast cancer immunotherapy.

Methods

NISA was prepared through conjugating mouse IgG3 Fc to MSN surface. Then, long-chain PEG₅₀₀₀, which was used to shield Fc to confer nanoparticle colloidal stability, was linked to the MSN surface via matrix metalloprotease-2 (MMP-2)-cleavable peptide (GPLGIAGQC). The activation of multiple components of innate immune system, including complement and the innate cells (macrophages and dendritic cells) and the associated anticancer effect were investigated.

Results

Fc fragments of NISA can be exposed through hydrolysis of long-chain PEG₅₀₀₀ by highly expressed MMP-2 in tumor microenvironment. Then, effective stimulation and activation of multiple components of innate immune system, including complement, macrophages, and dendritic cells were obtained, leading to efficient antitumor effect in 4T1 breast cancer cells and orthotopic breast tumor model in mice.

Conclusions

The antitumor potency conferred by NISA highlights the significance of stimulating multiple innate immune elements in cancer immunotherapy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01265-4.

Synthetic integrin-binding immune stimulators target cancer cells and prevent tumor formation

Immuno-oncology approaches mainly utilize monoclonal antibodies or protein-based scaffolds that bind with high affinity to cancer cells and can generate an immune response. Peptides can also bind with high affinity to cancer cells and are intermediate in size between antibodies and small molecules. They are also synthetically accessible and therefore easily modified to optimize their stability, binding affinity and selectivity. Here we describe the design of immune system engagers (ISErs), a novel class of synthetic peptide-based compounds that bind specifically to cancer cells and stimulate the immune system. A prototype, Y9, targets integrin α₃, which is overexpressed on several cancer cells, and activates the immune system via a formyl methionine-containing effector peptide. Injection of Y9 leads to immune cell infiltration into tissue and prevents tumor formation in a guinea pig model. The anti-tumor activity and synthetic accessibility of Y9 illustrate that ISErs could be applied to a wide variety of targets and diseases.

Acute and subacute toxicity of chemotactic conjugates between monoclonal antibody and fMet-Leu-Phe in humans: a phase I clinical trial

Conjugates of the chemotactic peptide fMet-Leu-Phe (fMLP) to IgG retain chemotactic and antigen recognition function in vitro and enhance intra-tumour macrophage numbers in a guinea pig model. We report a study approved by the ethics committee on the acute toxicity of fMLP conjugates in ten consenting cancer patients with metastasizing melanoma and colon cancer. They were given increasing single doses (1-2500 micrograms) IgG-fMLP made with the anti-melanoma monoclonal antibody (mAb) 9.2.27. Clinical examinations and blood cell counts, urinalysis, electrolytes, and liver and kidney function tests before and after the infusion and weekly thereafter revealed no relevant toxicities. One patient had a herpes zooster exacerbation on day 1, which was judged to be coincidental. Peak post-infusion conjugate serum concentrations fell to unmeasurable levels within a few days. In no case was a human humoral anti-(mouse Ig) immune response detected.

Chemotactic monoclonal antibody conjugates: a comparison of four different f-Met-peptide-conjugates

Intratumor macrophage numbers are enhanced by the administration of chemotactic f-MET-LEU-PHE - antitumor antibody - conjugates. The four f-MET-peptides f-MET-LEU-PHE, f-MET-LEU-PHE-o-methylester, formyl-norleucyl-phenylalanine and formyl-methionyl-phenylalanine, all chemotactic for human monocytes, where evaluated alone and conjugated to the melanoma directed monoclonal antibody ZME 018. f-MET-LEU-PHE-o-methyl-ester is the most active peptide, whereas f-MET-LEU-PHE - ZME 018 is the most active conjugate, not only inducing a response at the lowest concentration, but also the highest migrating cell numbers.

Conjugation behaviour of different monoclonal antibodies to f-methionyl-leucyl-phenylalanine

Monoclonal antibodies (moab) are potentially useful carriers for the targeting of effector substances into tumors. Conjugation of the chemotactic peptide f-Met-Leu-Phe (fMLP) to tumor-directed antibodies yields compounds active in vitro and in vivo. The present experiments examine the conjugation of fMLP to four different moab iso- and idiotypes. Molar coupling rations and chemotactic activity are not dependent on the moab species used for conjugation.