Poly(I:C) and CpG-ODN combined aerosolization to treat lung metastases and counter the immunosuppressive microenvironment

Abstract

The immunostimulatory ability of synthetic oligonucleotides containing CpG motifs (CpG-ODN), agonists of Toll-like receptor 9 (TLR9), can be harnessed to promote antitumor immunity by their application at the tumor site to stimulate local activation of innate immunity; however, particularly in the lung, tumor-associated immunosuppression can subvert such antitumor innate immune responses. To locally maintain continuous activation of innate subpopulations while inhibiting immunosuppressive cells, we evaluated aerosol delivery CpG-ODN combined with Poly(I:C), a TLR3 agonist able to convert tumor-supporting macrophages to tumoricidal effectors, in the treatment of B16 melanoma lung metastases in C57BL/6 mice. Aerosolization of CpG-ODN with Poly(I:C) into the bronchoalveolar space reduced the presence of M2-associated arginase-and IL-10-secreting macrophages in tumor-bearing lungs and increased the antitumor activity of aerosolized CpG-ODN alone against B16 lung metastases without apparent signs of toxicity or injury of the bronchial-bronchiolar structures and alveolar walls. Moreover, CpG-ODN/Poly(I:C) aerosol combined with dacarbazine, a therapeutic agent used in patients with inoperable metastatic melanoma able to exert immunostimulatory effects, led to a significant increase in antitumor activity as compared to treatments with aerosolized CpG-ODN/Poly(I:C) or dacarbazine alone. This effect was related to an enhanced recruitment and cytotoxic activity of tumor-infiltrating NK cells in the lung. Our results point to aerosol delivery as a convenient approach for repeated applications of immunostimulants in patients with lung metastases to maintain a continuous local activation of innate immune cells while suppressing polarization of tumor-infiltrating macrophages to an M2 phenotype.

The lung microbiota: role in maintaining pulmonary immune homeostasis and its implications in cancer development and therapy

“…We previously observed that the aerosol delivery of various agents, such as TLR agonists and cytokines, was able to favor the immune-mediated control of experimental lung metastases, indicating the feasibility of influencing local lung immunity through a non-invasive strategy [63][64][65][66][67].…”

Exploiting poly(I:C) to induce cancer cell apoptosis

“… 4 The antitumor responses that are induced by TLR3 agonists are attributed to their capability to stimulate antigen-presenting cells (APCs), such as DCs, which in turn activate tumor-specific T cell responses and to their capacity to switch the phenotype of myeloid suppressor cells and tumor-associated macrophages from immunosuppressive to immunosupportive. 5-7 …”

Reprogramming the lung microenvironment by inhaled immunotherapy fosters immune destruction of tumor

“…In a model of B16 murine melanoma lung metastases in which protection primarily requires activation of NK effector cells, we showed that aerosolized Poly(I:C), a TLR3 agonist able to convert tumor-associated macrophages (TAM) from tumor -supporting (M2) to tumor-counteracting (M1) function, combined with aerosolized CpG-ODN, a TLR9 agonist able to activate NK cells, significantly improved antitumor effects. 7 Our data suggested that aerosolization represents a non-invasive therapy to improve tissue concentration and exposure to immunotherapeutic agents, while limiting exposure and potential adverse effects in healthy organs.…”