Background Myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment are potential therapeutic targets in immune checkpoint cancer therapy, particularly for cancers that are unresponsive to anti-PD-1 therapy. It has previously been demonstrated that trefoil factor family 2 (TFF2), a secreted anti-inflammatory peptide, can partially suppress MDSC expansion and activate tumor immunity through agonism of the CXCR4 receptor.^1–3 We investigated whether a novel fusion protein, murine TFF2-murine serum albumin (mTFF2-MSA), has single agent activity and can improve on the therapeutic effects of anti-PD-1 in CT26.wt subcutaneous and CT26-Luciferase (CT26-Luc) orthotopic syngeneic mouse models of advanced colorectal cancer (CRC).

Methods Two syngeneic colon carcinoma mouse models were developed using the CT26.wt and CT26-Luc CRC cell lines grafted subcutaneously and orthotopically, respectively, into BALB/C mice. We generated a recombinant fusion protein, designated mTFF2-MSA, which contains murine TFF2 fused to murine serum albumin (MSA), for the purpose of increasing half-life and reducing the frequency of dosing. Mice subsequently received mTFF2-MSA, anti-PD-1 antibody (clone 29F.1A12 for subcutaneous study; clone RMP-1–14 for orthotopic study) or combination of mTFF2-MSA and anti-PD-1. Tumor volume, and survival were measured. At the endpoint, flow cytometry was performed on the blood, bone marrow, tumor, and lymph nodes, to examine treatment-induced effects on cellular immune profiles.

Results In the CT26.wt model, tumor growth was suppressed by mTFF2-MSA, anti-PD-1 and by the combination of mTFF2-MSA/anti-PD-1 by 16%, 40% and 60%, respectively. Survival in the CT26.wt model on Day 30 treated with vehicle, mTFF2-MSA, anti-PD1 and the combination of mTFF2-MSA and anti-PD-1 was 0%, 40%, 60% and 60%, respectively. In the CT26-Luc model, mTFF2-MSA, anti-PD-1, and the combination of mTFF2-MSA and anti-PD-1 suppressed tumor growth by 42%, 94%, and 94%, respectively. In the CT26-Luc model, neutrophils were significantly reduced in the blood in all treatment groups by flow cytometry. In the bone marrow, a significant reduction in total macrophages, M2 macrophages, and neutrophils was also observed but only in the group treated with anti-PD-1/mTFF2-MSA. In the axillary lymph node, there was a significant reduction in TOX+ cells in both CD4+ and CD8+ T-cells in all treatment groups. In the tumor, there was a significant reduction in total macrophages and M2 macrophages in all treatment groups, while NK cells were also increased, but only in the combination anti-PD-1/mTFF2-MSA treated group.

Conclusions mTFF2-MSA has single agent activity and is additive to anti-PD-1 antibody checkpoint inhibition in treating two syngeneic (subcutaneous and orthotopic) mouse models of advanced colorectal cancer.

References

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2. Dubeykovskaya Z, Si Y, Chen X, Worthley DL, Renz BW, Urbanska AM, Hayakawa Y, Xu T, Westphalen CB, Dubeykovskiy A, Chen D, Friedman RA, Asfaha S, Nagar K, Tailor Y, Muthupalani S, Fox JG, Kitajewski J, Wang TC. Neural innervation stimulates splenic TFF2 to arrest myeloid cell expansion and cancer. Nat Commun. 2016;7:1–11.

3. Dubeykovskaya Z, Duddempudi PK, Deng H, Valenti G, Cuti, KL, Nagar K, Tailor Y, Guha C, Kitajewski J, Wang TC. Therapeutic potential of adenovirus-mediated TFF2-CTP-Flag peptide for treatment of colorectal cancer. Cancer Gene Ther. 2019;26:48–57.