Biodegradable nanoparticles inhibit tumor growth by altering tumor-associated macrophages and cancer-associated fibroblasts

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Background: The tumor microenvironment (TME) plays a crucial role in tumor growth and progression and has a significant influence on response to therapy. The TME consists of myeloid-derived cells, stroma (e.g. fibroblasts and extracellular matrix (ECM)), and the vasculature that together support tumor growth and progression. Studies in animal models and in humans show that myeloid- derived cells such as myeloid derived suppressor cells (MDSCs) and tumor associated macrophages (TAMs) engage in activities that support tumor growth and progression. These cells also promote immune suppression in the TME that blunts the efficacy of the anti-cancer drugs and immune-targeted therapies such as immune checkpoint inhibitors. In addition to MDSCs, cancer-associated fibroblasts (CAFs) in the TME support tumor progression via production of pro-tumor and pro-angiogenic growth-factors, remodeling of the ECM via production of proteases, and suppression of anti-tumor immune function. CAF abundance in the TME is a negative prognostic factor for several solid tumors and is associated with negative outcomes and poor response to immune-targeted therapies like immune checkpoint inhibitors. ONP-302 nanoparticles fabricated from biodegradable poly (lactic-co-glycolic acid)(PLGA) polymer have been previously described in the literature for the treatment of acute inflammatory conditions via immuno-modulatory effects on myeloid derived cells. Here, we evaluated the efficacy of ONP-302 nanoparticles at inhibiting tumor growth via targeted inhibition of myeloid-derived cells and reshaping of the TME. Methods: ONP-302 anti-tumor efficacy was evaluated in syngeneic mouse tumor models using both immunocompetent and immunodeficient mice. We examined the effect of ONP-302 treatment tumor growth kinetics and effects on the major cellular constituents of the TME such as myeloid-derived cells and CAFs. Results: Therapeutic treatment with ONP-302 in vivo resulted in a marked delay in tumor growth in three different syngeneic tumor models in immunocompetent mice. ONP- 302 efficacy persisted with depletion of CD8+ T cells in immunocompetent mice and also was effective in immune deficient mice. We found ONP-302 treatment caused a gene expression shift in TAMs toward the pro-inflammatory M1 type and substantially inhibited the expression of genes associated with the pro-tumorigenic function of CAFs. ONP-302 also induced apoptosis in CAFs in the TME. Conclusions: Our data indicate that the slowing of tumor growth after ONP-302 treatment is due to disruptions in known signaling pathways involving TAMs and CAFs, pathways typically supporting tumor growth. These data taken in concert indicate the activity of ONP-302 is pleotropic and affects multiple pathways.

ONP-302 Nanoparticles Inhibit Tumor Growth By Altering Tumor-Associated Macrophages And Cancer-Associated Fibroblasts

In this study, we evaluated the ability of negatively charged bio-degradable nanoparticles, ONP- 302, to inhibit tumor growth. Therapeutic treatment with ONP-302 in vivo resulted in a marked delay in tumor growth in three different syngeneic tumor models in immunocompetent mice. ONP- 302 efficacy persisted with depletion of CD8+ T cells in immunocompetent mice and also was effective in immune deficient mice. Examination of ONP-302 effects on components of the tumor microenvironment (TME) were explored. ONP-302 treatment caused a gene expression shift in TAMs toward the pro-inflammatory M1 type and substantially inhibited the expression of genes associated with the pro-tumorigenic function of CAFs. ONP-302 also induced apoptosis in CAFs in the TME. Together, these data support further development of ONP-302 as a novel first-in- class anti-cancer therapeutic that can be used as a single-agent as well as in combination therapies for the treatment of solid tumors due to its ability to modulate the TME.

Negatively charged nanoparticles inhibit tumor growth by altering tumor-associated macrophages and cancer-associated fibroblasts

In this study, we show that a negatively charged biodegradable nanoparticles, CNP-301, have strong anti-tumor activity in several tumor models. This effect appears to be driven by shifting polarization of tumor associated macrophages (TAMs) to an anti-tumor M1 type and by downregulation of pro-tumorigenic cancer associated fibroblasts. Moreover, we show that CNP-301 treatment induces apoptosis of cancer associated fibroblasts (CAFs) in the tumor supporting a mechanism where perturbations of the TME and the associated stroma results in anti-tumor effects.

Tumor-infiltrating mast cells are associated with resistance to anti-PD-1 therapy

Anti-PD-1 therapy is used as a front-line treatment for many cancers, but mechanistic insight into this therapy resistance is still lacking. Here we generate a humanized (Hu)-mouse melanoma model by injecting fetal liver-derived CD34⁺ cells and implanting autologous thymus in immune-deficient NOD-scid IL2Rγ^null (NSG) mice. Reconstituted Hu-mice are challenged with HLA-matched melanomas and treated with anti-PD-1, which results in restricted tumor growth but not complete regression. Tumor RNA-seq, multiplexed imaging and immunohistology staining show high expression of chemokines, as well as recruitment of FOXP3⁺ Treg and mast cells, in selective tumor regions. Reduced HLA-class I expression and CD8⁺/Granz B⁺ T cells homeostasis are observed in tumor regions where FOXP3⁺ Treg and mast cells co-localize, with such features associated with resistance to anti-PD-1 treatment. Combining anti-PD-1 with sunitinib or imatinib results in the depletion of mast cells and complete regression of tumors. Our results thus implicate mast cell depletion for improving the efficacy of anti-PD-1 therapy.

Immune checkpoint therapies (ICT) are promising for treating various cancers, but response rates vary. Here the authors show, in mouse models, that tumor-infiltrating mast cells colocalize with regulatory T cells, coincide with local reduction of MHC-I and CD8 T cells, and is associated with resistance to ICT, which can be reversed by c-kit inhibitor treatment.

RETRACTED ARTICLE: IspH inhibitors kill Gram-negative bacteria and mobilize immune clearance

Isoprenoids are vital to all organisms in supporting core functions of life, like respiration and membrane stability.¹ IspH, an enzyme in the methyl erythritol phosphate pathway of isoprenoid synthesis, is essential to gram-negative bacteria, mycobacteria and apicomplexans.^2,3 The IspH substrate, HMBPP, is not produced in humans and other metazoans and activates cytotoxic Vγ9Vδ2 T-cells in humans and primates at extremely low concentrations.^4-6 We describe novel IspH inhibitors and through structure-guided analog design, refine their potency to nanomolar levels. We have modified these into prodrugs for delivery into bacteria and report that they kill clinical isolates of several multidrug resistant bacterial species such as Acinetobacter, Pseudomonas, Klebsiella, Enterobacter, Vibrio, Shigella, Salmonella, Yersinia, Mycobacterium and Bacillus, while being relatively non-toxic to mammalian cells. Proteomic analysis reveals that bacteria treated with prodrugs resemble those with conditional IspH knockdown. Notably, these prodrugs also cause expansion and activation of human Vγ9Vδ2 T-cells in a humanized mouse model of bacterial infection. These IspH prodrugs synergize direct antibiotic killing with a simultaneous rapid immune response by cytotoxic γδ T-cells, which may limit the rise of antibiotic resistant bacterial populations.

African-centric TP53 variant increases iron accumulation and bacterial pathogenesis but improves response to malaria toxin

A variant at amino acid 47 in human TP53 exists predominantly in individuals of African descent. P47S human and mouse cells show increased cancer risk due to defective ferroptosis. Here, we show that this ferroptotic defect causes iron accumulation in P47S macrophages. This high iron content alters macrophage cytokine profiles, leads to higher arginase level and activity, and decreased nitric oxide synthase activity. This leads to more productive intracellular bacterial infections but is protective against malarial toxin hemozoin. Proteomics of macrophages reveal decreased liver X receptor (LXR) activation, inflammation and antibacterial defense in P47S macrophages. Both iron chelators and LXR agonists improve the response of P47S mice to bacterial infection. African Americans with elevated saturated transferrin and serum ferritin show higher prevalence of the P47S variant (OR = 1.68 (95%CI 1.07–2.65) p = 0.023), suggestive of its role in iron accumulation in humans. This altered macrophage phenotype may confer an advantage in malaria-endemic sub-Saharan Africa.

A polymorphism in human TP53 (P47S) that predominantly exists in individuals of African descent affects ferroptosis. Here, the authors show that this results in iron accumulation in macrophages leading to more productive infection by intracellular bacteria but improved anti-inflammatory response to the malarial toxin hemozoin.

Cancer-Associated Fibroblasts Neutralize the Anti-tumor Effect of CSF1 Receptor Blockade by Inducing PMN-MDSC Infiltration of Tumors

Tumor-associated macrophages (TAM) contribute to all aspects of tumor progression. Use of CSF1R inhibitors to target TAM is therapeutically appealing, but has had very limited anti-tumor effects. Here, we have identified the mechanism that limited the effect of CSF1R targeted therapy. We demonstrated that carcinoma-associated fibroblasts (CAF) are major sources of chemokines that recruit granulocytes to tumors. CSF1 produced by tumor cells caused HDAC2-mediated downregulation of granulocyte-specific chemokine expression in CAF, which limited migration of these cells to tumors. Treatment with CSF1R inhibitors disrupted this crosstalk and triggered a profound increase in granulocyte recruitment to tumors. Combining CSF1R inhibitor with a CXCR2 antagonist blocked granulocyte infiltration of tumors and showed strong anti-tumor effects.