Therapeutic targeting with DABIL‐4 depletes myeloid suppressor cells in 4T1 triple‐negative breast cancer model

Abstract

In many solid tumors including triple‐negative breast cancer (TNBC), upregulation of the interleukin‐4 receptor (IL‐4R) has been shown to promote cancer cell proliferation, apoptotic resistance, metastatic potential, and a Th2 response in the tumor microenvironment (TME). Since immunosuppressive cells in the TME and spleen including myeloid‐derived suppressor cells (MDSCs) and tumor‐associated macrophages (TAMs) also express the IL‐4R, we hypothesized that selective depletion of IL‐4R‐bearing cells in TNBC would result in the direct killing of tumor cells and the depletion of immunosuppressive cells and lead to an enhanced antitumor response. To selectively target IL‐4R + cells, we employed DABIL‐4, a fusion protein toxin consisting of the catalytic and translocation domains of diphtheria toxin fused to murine IL‐4. As anticipated, DABIL‐4 has potent cytotoxic activity against TNBC cells both in vitro and in vivo . We demonstrate in the murine 4T1 TNBC model that DABIL‐4 significantly reduces tumor growth, splenomegaly, and lung metastases. Importantly, we also show that the administration of DABIL‐4 results in the selective depletion of MDSCs, TAMs, and regulatory T cells in treated mice, with a concomitant increase in IFN‐γ + CD8 effector T cells in the TME. Since the 4T1 antitumor activity of DABIL‐4 was largely diminished in IL‐4R knockout mice, we postulate that DABIL‐4 functions primarily as an immunotherapeutic by the depletion of MDSCs, TAMs, and regulatory T cells. NanoString analysis of control and treated tumors confirmed and extended these observations by showing a marked decline of mRNA transcripts that are associated with tumorigenesis and metastasis. In conclusion, we demonstrate that DABIL‐4 targeting of both tumor and immunosuppressive host cells likely represents a novel and effective treatment strategy for 4T1 TNBC and warrants further study.

Preclinical PET Imaging of Granzyme B Shows Promotion of Immunological Response Following Combination Paclitaxel and Immune Checkpoint Inhibition in Triple Negative Breast Cancer

“…This observation was opposite of our initial hypothesis because C57/Bl6 mice have been reported as having a genetically programmed bias toward Th1 immunity, mainly regulated by IFN-γ [54]. Th2 cytokines are associated with the presence of immunosuppressive cells in the TME, specifically myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) [55]. Additionally, Th2 cytokines, particularly IL-4, are associated with a humoral response and have been shown to promote tumor cell proliferation and resistance to apoptosis [55].…”

“…Th2 cytokines are associated with the presence of immunosuppressive cells in the TME, specifically myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) [55]. Additionally, Th2 cytokines, particularly IL-4, are associated with a humoral response and have been shown to promote tumor cell proliferation and resistance to apoptosis [55]. Therefore, Th1 stimulation by combination IMT/PTX treatment may be tampered by simultaneous Th2 stimulation.…”

Magnetic resonance imaging of tumor-associated-macrophages (TAMs) with a nanoparticle contrast agent

“…36–38 In breast cancers, high macrophage content has been associated with poor prognosis, 39,40 so we expected to find higher density of TAMs of tumor-permissive, M2-like function. Since breast cancer development activates multiple pathways that correlate to macrophage polarization and behavior, 41,42 it is likely that a mixed effect will occur during the process, which meets our model needs. Fig.…”

Tumor-Associated Macrophages: Key Players in Triple-Negative Breast Cancer

“…TAMs can secrete a variety of cytokines in the TNBC environment, which mediate their immunosuppressive and tumor-promoting activities (71)(72)(73). Studies have found that TAMs can secrete IFN-g through JAK/ STAT3 and PI3K/AKT signaling pathways, thereby inducing the expression of PD-L1 (74,75). IL-6 is related to growth of TNBC and prognosis of patients.…”