Immune dysregulation drives the pathogenesis of chronic inflammatory, autoimmune and dysplastic disorders. While often intended to address localized pathology, most immune modulatory therapies are administered systemically and carry inherent risk of multi-organ toxicities. Here we demonstrate, in a murine model of spontaneous gastrointestinal polyposis, that site-specific uptake of orally-administered microparticles of the interleukin IL-10 ameliorates local and systemic disease to enhance survival. Mechanistic investigations showed that the therapeutic benefit of this treatment derived from neutralization of disease-promoting FoxP3+RoRγt+IL17+ pathogenic T-regulatory cells (pgTreg), with a concomitant restoration of FoxP3+RoRγt-IL17- conventional T regulatory cells (Treg). These findings provide a proof-of-principle for the ability of an oral biologic to restore immune homeostasis at the intestinal surface. Further, they implicate local manipulation of IL-10 as a tractable therapeutic strategy to address the inflammatory sequelae associated with mucosal premalignancy.
While ionizing radiation is a major form of cancer therapy, radioresistance remains a therapeutic obstacle. We have previously shown that the mandated housing temperature for laboratory mice (~22°C) induces mild, but chronic, cold stress resulting in increased circulating norepinephrine, which binds to, and triggers activation of, beta-adrenergic receptors (β-AR) on tumor and immune cells. This adrenergic signaling increases tumor cell intrinsic resistance to chemotherapy and suppression of the anti-tumor immune response. These findings led us to hypothesize that adrenergic stress signaling increases radioresistance in tumor cells in addition to suppressing Tcell-mediated anti-tumor immunity, thus suppressing the overall sensitivity of tumors to radiation. We used three strategies to test the effect of adrenergic signaling on responsiveness to radiation. For one strategy, mice implanted with CT26 murine colon adenocarcinoma were housed at either 22°C or at thermoneutrality (30°C), which reduces physiological adrenergic stress. For a second strategy, we used a β-AR antagonist ("beta blocker") to block adrenergic signaling in mice housed at 22°C. In either case, tumors were then irradiated with a single 6 Gy dose and the response was compared to mice whose adrenergic stress signaling was not reduced. For the third strategy, we used an in vitro approach in which several different tumor cell lines were treated with a β-AR agonist and irradiated, and cell survival was then assessed by clonogenic assay. Overall, we found that adrenergic stress significantly impaired the anti-tumor efficacy of radiation by inducing tumor cell resistance to radiation-induced cell killing and by suppression of anti-tumor immunity. Treatment using beta blockers is a promising strategy for increasing the anti-tumor efficacy of radiotherapy.
Purpose: Orthotopic tumors more closely recapitulate human cancers than do ectopic models; however, precision targeting of such internal tumors for radiation therapy (RT) without inducing systemic toxicity remains a barrier. We developed an innovative murine orthotopic rectal tumor model where the insertion of clinical grade titanium fiducial clips on opposing sides of the rectal tumor allowed for targeted administration of short-course radiation therapy (SCRT). With this novel approach, clinically relevant RT regimens can be administered to orthotopic tumors to explore the biology and efficacy of radiation alone or as a combination therapy in a murine model that closely recapitulates human disease. Methods and Materials: Murine Colon 38-luciferase tumor cells were injected into the rectal wall of syngeneic mice, and fiducial clips were applied to demarcate the tumor. An SCRT regimen consisting of 5 consecutive daily doses of 5 Gy delivered by an image-guided conformal small animal irradiator was administered 9 days after implantation. Tumor burden and survival were monitored along with histological and flow cytometric analyses on irradiated versus untreated tumors at various time points. Results: SCRT administered to orthotopic rectal tumors resulted in a reduction in tumor burden and enhanced overall survival with no apparent signs of systemic toxicity. This treatment paradigm resulted in significant reductions in tumor cellularity and increases in fibrosis and hyaluronic acid production, recapitulating the SCRT-induced effects observed in human cancers.
Radiotherapy (RT) is commonly employed to treat solid tumors. Immune checkpoint blockade of programmed cell death protein 1 (PD-1) and CTLA-4 improves survival in RT patients, yet many fail to respond to combination therapy. Natural killer group 2 (NKG2) family receptors, particularly inhibitory NKG2A and activating NKG2D, have emerged as promising therapeutic targets to improve antitumor T cell responses; thus, we examined how these receptors and their ligands (Qa-1b and retinoic acid early inducible 1 [Rae-1], respectively) regulate the RT response in C57BL/6 mice bearing syngeneic B16F10 melanoma and MC38 colorectal adenocarcinoma tumors. RT (15 Gy) transiently reduced B16F10 tumor burden, whereas MC38 tumors exhibited durable response to RT. Intratumoral NK and CD8 T cells expressed NKG2A and NKG2D in both models, which was unaltered by RT. In vitro/in vivo RT increased tumor/stromal cell Qa-1b and Rae-1 expression in both models, especially B16F10 tumors, but IFN-γ stimulation induced both Qa-1b and Rae-1 only in B16F10 tumors. NKG2A/Qa-1b inhibition alone did not improve RT response in either model, but combined RT and NKG2A/PD-1 blockade improved survival in the B16F10 model. Depletion experiments indicate that the triple therapy efficacy is CD8 T cell–dependent with negligible NK cell contribution. RNA sequencing of CD8 T cells from triple therapy–treated B16F10 tumors showed increased proliferative capacity compared with RT and PD-1 blockade alone. Our work demonstrates that RT modulates NKG2A ligand expression, which inhibits RT-induced T cell responses in tumors that fail to respond to combined RT and PD-1 blockade. These results provide a rationale for combining NKG2A blockade with immune checkpoint blockade therapies and RT to improve clinical response.
More than half of patients with solid tumor malignancies undergo treatment with radiotherapy (RT). In addition to causing direct tumor cell death, RT results in release of tumor antigen and damage associated molecular patterns that elicit a CD8 T cell and IFN-g dependent anti-tumor immune response. To further bolster this response, RT has been combined with immune checkpoint inhibitors such as anti-PD-1 and anti-CTLA-4. Despite a modest increase in survival when these therapies are used alone or together in conjunction with RT, many patients fail to respond to treatment, suggesting other mechanisms of immune suppression exist in the tumor microenvironment (TME). Using syngeneic B16 F10 melanoma and C38 colorectal adenocarcinoma models, we have studied the role of the inhibitory receptor NKG2A. We have observed that NKG2A is expressed only on tumor infiltrating lymphocytes (TILs) and expression of this receptor does not change with RT. Furthermore, RT increases intratumoral expression of the ligand for NKG2A, Qa-1b, as does IFN-g stimulation in vitro. Blockade of NKG2A alone through use of B16 F10 cells lacking Qa-1b expression or blocking antibodies did not significantly increase survival of mice treated with RT. Further analysis revealed that among CD8 TILs, only a minority of cells express NKG2A alone, with most TILs co-expressing NKG2A and PD-1 or PD-1 alone. Thus, we combined anti-NKG2A and anti-PD-1 blockade and observed increased survival in mice treated with RT, whereas either therapy alone was ineffective. These results suggest that NKG2A blockade could be combined with RT and existing immunotherapies clinically to improve patient response. Supported by awards T32AI007285 from the NIAID and R01CA028332 from the NCI.
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