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

Abstract

Due to their constant exposure to inhaled antigens, lungs represent a particularly immunosuppressive environment that limits excessive immune responses; however, cancer cells can exploit this unique environment for their growth. We previously described the ability of aerosolized CpG-ODN combined with Poly(I:C) (TLR9 and TLR3 agonists, respectively) to promote antitumor immunity in a B16 melanoma lung metastasis model. Here, we explored the possibility of improving the therapeutic efficacy of TLR9/TLR3 agonist combinations by including in the inhalant either an antibody directed to both Ly6G and Ly6C markers to locally deplete myeloid-derived suppressive cells (MDSCs) or IFNa to directly activate the natural killer (NK) and macrophage innate immune cells in the lung. Addition of nebulized anti-MDSC antibody RB6-8C5 to aerosolized CpG-ODN/Poly(I:C) resulted in reduced mRNA levels of immunsuppressive molecules (IL10, Arg-1, and Nos2), increased activation of resident NK cells and improved treatment outcome, with a significant reduction in established B16 melanoma lung metastases compared to treatment with CpG-ODN/ Poly(I:C) alone. Likewise, addition of aerosolized IFNa led to increased mRNA levels of proinflammatory cytokines (IL15 and IFNg) in the lung and recruitment of highly activated NK cells, with no evident signs of toxicity and with a significantly improved antitumor effect as compared with aerosolized CpG-ODN/Poly(I:C). Combining both IFNa and RB6-8C5 with CpG-ODN/Poly(I:C) did not produce an additive effect compared to IFNa C CpG-ODN/Poly(I:C) or RB6-8C5 C CpG-ODN/Poly(I:C). Our results indicate that the inhalation therapy is a feasible and non-invasive strategy to deliver immunodulatory molecules, including antibodies and cytokines that reprogram the lung tumor microenvironment to foster immune destruction of tumors.

Inhaled TLR9 Agonist Renders Lung Tumors Permissive to PD-1 Blockade by Promoting Optimal CD4+ and CD8+ T-cell Interplay

“…A different CpG-ODN, delivered intratracheally, has been reported to have activity on lung tumors when formulated as a microparticle, but not as a solution (38). In a model of B16 melanoma lung metastasis, an inhaled formulation of poly (I:C) TLR3 agonist and CpG-ODN TLR9 agonist was shown to decrease lung metastasis restoring NK-cell effector function (39).…”

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].…”

Trial Watch: Toll-like receptor agonists in cancer immunotherapy

“…Since the submission of the latest Trial Watch dealing with this topic (September 2015), 88 no less than 66 clinical studies involving the administration of TLR agonists to cancer patients have been initiated (source http://clinicaltrials.gov/). The majority of these trials involve the FDA-approved molecules imiquimod (17 studies) and BCG (11 studies), as well as the hitherto experimental TLR3 agonist Hiltonol®, a particular formulation of polyI:C that includes carboxymethylcellulose and poly-L-lysine as stabilizing agents, 156,167,168 (20 studies), and the TLR9 agonist SD-101 (9 studies) ( Table 1).…”