Fluorescent nanodiamonds as innovative delivery systems for MiR-34a replacement in breast cancer

Nanodiamonds are innovative nanocrystalline carbon particles able to deliver chemically conjugated miRNAs. In oncology, the use of miRNA-based therapies may represent an advantage, based on their ability to simultaneously target multiple intracellular oncogenic targets. Here, nanodiamonds were tested and optimized to deliver miR-34a, a miRNA playing a key role in inhibiting tumor development and progression in many cancers. The physical-chemical properties of nanodiamonds were investigated suggesting electrical stability and uniformity of structure and size. Moreover, we evaluated nanodiamond cytotoxicity on two breast cancer cell models and confirmed their excellent biocompatibility. Subsequently, nanodiamonds were conjugated with miR-34a, using the chemical crosslinker polyethyleneimine; real-time PCR analysis revealed a higher level of miR-34a in cancer cells treated with the different formulations of nanodiamonds than with commercial transfectant. A significant and early nanodiamond-miR-34a uptake was recorded by FACS and fluorescence microscopy analysis in MCF7 and MDA-MB-231 cells. Moreover, nanodiamond-miR-34a significantly inhibited both cell proliferation and migration. Finally, a remarkable anti-tumor effect of miR-34a-conjugated nanodiamonds was observed in both heterotopic and orthotopic murine xenograft models. In conclusion, this study provides a rationale for the development of new therapeutic strategies based on use of miR-34a delivered by nanodiamonds to improve the clinical treatment of neoplasms.

Antitumor activity of novel POLA1-HDAC11 dual inhibitors

Hybrid molecules targeting simultaneously DNA polymerase α (POLA1) and histone deacetylases (HDACs) were designed and synthesized to exploit a potential synergy of action. Among a library of screened molecules, MIR002 and GEM144 showed antiproliferative activity at nanomolar concentrations on a panel of human solid and haematological cancer cell lines. In vitro functional assays confirmed that these molecules inhibited POLA1 primer extension activity, as well as HDAC11. Molecular docking studies also supported these findings. Mechanistically, MIR002 and GEM144 induced acetylation of p53, activation of p21, G1/S cell cycle arrest, and apoptosis. Oral administration of these inhibitors confirmed their antitumor activity in in vivo models. In human non-small cancer cell (H460) xenografted in nude mice MIR002 at 50 mg/kg, Bid (qd × 5 × 3w) inhibited tumor growth (TGI = 61%). More interestingly, in POLA1 inhibitor resistant cells (H460-R9A), the in vivo combination of MIR002 with cisplatin showed an additive antitumor effect with complete disappearance of tumor masses in two animals at the end of the treatment. Moreover, in two human orthotopic malignant pleural mesothelioma xenografts (MM473 and MM487), oral treatments with MIR002 and GEM144 confirmed their significant antitumor activity (TGI = 72-77%). Consistently with recent results that have shown an inverse correlation between POLA1 expression and type I interferon levels, MIR002 significantly upregulated interferon-α in immunocompetent mice.

Novel adamantyl retinoid-related molecules with POLA1 inhibitory activity

Atypical retinoids (AR) or retinoid-related molecules (RRMs) represent a promising class of antitumor compounds. Among AR, E-3-(3'-adamantan-1-yl-4'-hydroxybiphenyl-4-yl)acrylic acid (adarotene), has been extensively investigated. In the present work we report the results of our efforts to develop new adarotene-related atypical retinoids endowed also with POLA1 inhibitory activity. The effects of the synthesized compounds on cell growth were determined on a panel of human and hematological cancer cell lines. The most promising compounds showed antitumor activity against several tumor histotypes and increased cytotoxic activity against an adarotene-resistant cell line, compared to the parent molecule. The antitumor activity of a selected compound was evaluated on HT-29 human colon carcinoma and human mesothelioma (MM487) xenografts. Particularly significant was the in vivo activity of the compound as a single agent compared to adarotene and cisplatin, against pleural mesothelioma MM487. No reduction of mice body weight was observed, thus suggesting a higher tolerability with respect to the parent compound adarotene.

A Herbal Mixture from Propolis, Pomegranate, and Grape Pomace Endowed with Anti-Inflammatory Activity in an In Vivo Rheumatoid Arthritis Model

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by the production of inflammatory factors. In order to overcome the side effects of currently used anti-inflammatory drugs, several attempts have been made to identify natural products capable of relieving RA symptoms. In this work, a herbal preparation consisting of propolis, pomegranate peel, and Aglianico grape pomace (PPP) extracts (4:1:1) was designed and evaluated for its effect on a murine collagen-induced arthritis (CIA) model. Firstly, the chemical contents of four different Italian propolis collected in the Campania region (Italy) were here reported for the first time. LC-MS analyses showed the presence of 38 constituents, identified in all propolis extracts, belonging to flavonoids and phenolic acids classes. The Pietradefusi extract was the richest one and thus was selected to design the PPP preparation for the in vivo assay. Our results highlight the impact of PPP on RA onset and progression. By using in vivo CIA models, the treatment with PPP resulted in a delayed onset of the disease and alleviated the severity of the clinical symptoms. Furthermore, we demonstrated that early PPP treatment was associated with a reduction in serum levels of IL-17, IL-1b, and IL-17–triggering cytokines.

Abstract 2994: In vivo targeting of mesothelioma’s molecular signature with nanoparticle functionalized with nucleolin-binding peptide

Mesothelioma is a malignant tumor of the mesothelium, often associated with asbestos exposure, with an overall survival of only 8.8 months. A combination of cisplatin and pemetrexed has been used as an adjuvant treatment to surgical resection or in patients who have inoperable disease. This combination remains as the current standard of care, regardless the sub-type of mesothelioma, with only a 9% 5-year survival rate. Herein, it is hypothesized that a novel targeted treatment, based on a doxorubicin (DXR)-containing nanoparticle functionalized with the nucleolin-binding F3 peptide (named PEGASEMP), will have significant a therapeutic impact against the most aggressive subtype of mesothelioma (biphasic). The hypothesis relies on nucleolin deregulated overexpression in cancer and endothelial cells from tumor blood vessels. Human biphasic mesothelioma cells were stably transduced with luciferase-reporter gene, and orthotopically injected intrapleurally into female immunocompromised mice. Three weeks (Early Stage) and 4 weeks (Advanced Stage) after cell injection, animals were randomly allocated to different treatment groups: vehicle, PEGASEMP at 5.6 or 7 mg of DXR/kg alone (q7dx5w); cisplatin at 4.0 mg/kg alone or combined with PEGASEMP at 5.6 mg of DXR/kg (q7dx5w); and the standard of care, a combination of cisplatin at 4.0 mg/kg (q7dx5w) plus pemetrexed at 100.0 mg/kg (q2dx3x5w). Bioluminescence was monitored weekly with IVIS Spectrum In Vivo Imaging system. Differential gene expression upon PEGASEMP treatment of advanced stage tumors was also performed in comparison with non-treated animals using the GeneChip Human Transcriptome Array 2.0. In the early stage of development, PEGASEMP, at 7.0 mg/kg, inhibited tumor growth by 2,713-fold relative to standard of care, which translated into a 1223-fold decrease in tumor burden. At an advanced stage of tumor development, the combination of PEGASEMP and cisplatin enabled 107-fold tumor growth inhibition, enabling a 55-fold reduction in tumor burden, relative to standard of care. In both cases, no decrease of the body weight was observed. Furthermore, 75% (146) gene transcripts were found to be deregulated (while the remaining 25% were upregulated), involving the downregulation of cell division, including ontologies such as cell cycle or chromatin organization and assembly. Specifically, downregulation of topoisomerase 2, cyclin B1 or Ki67 transcripts, part of the described molecular signature of mesothelioma, was observed and was consistent with the mechanism of action of doxorubicin. Overall, the novel mechanism of action associated with PEGASEMP, enables a significant benefit in terms of efficacy and safety in the treatment of biphasic mesothelioma, as compared with the current standard of care, affecting the molecular signature of the disease and thus supporting future clinical evaluation.

Citation Format: Nuno A. Fonseca, Vera Moura, Fabiana Colelli, Daniela Pesce, Giacomo Signorino, Laura Focareta, Alessandra Fucci, Francesco Cardile, Claudio Pisano, Sérgio Simões, João Nuno Moreira. In vivo targeting of mesothelioma’s molecular signature with nanoparticle functionalized with nucleolin-binding peptide [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2994.

Abstract 3096: Host antitumor immune response activated by Dual POLA1-HDAC11 inhibitors endowed with a large spectrum of antitumor activity

Small molecule modulators of chromatin modifying enzymes became the focus of drug discovery efforts, because of their direct antitumor effects, such as apoptosis and cell-cycle arrest, in addition to their indirect immunomodulation properties (Peedicayil, 2012; West and Johnstone, 2014; Falkenberg and Johnstone, 2014). Recent studies have shown that inhibition of HDACs or POLA1 activity exerts anti-proliferative effects and also potentiates the immune response by activating type I Interferon (Medon et al., 2017; Starokadomskyy et al, 2016). To exploit a potential synergy, hybrid molecules targeting simultaneously POLA1 and HDACs, were designed. Here, we present in vitro and in vivo data concerning the antitumor activity of new dual POLA1-HDAC11 inhibitors. Among a library of screened molecules, MIR002 and MIR144 showed an antiproliferative activity at nanomolar concentrations on a panel of human tumor cell lines. In vitro functional assays revealed that these molecules potently inhibit POLA1 and specifically act on HDAC11 that recently emerged as regulator of several immune cells differentiation, pointing out its immunomodulatory role. Mechanistically, MIR002 and MIR144 induce acetylation of Histone H4 and alpha-Tubulin, canonical targets of HDACs, and p53-K382, as well. Activation of p53 leads to p21 increase and cell cycle arrest in the G1/S boundary. These compounds could be even more effective in treating human cancers when they are appropriately combined with other chemotherapeutics, such as Cisplatin. Indeed, the combination of MIR002 or MIR144 with Cisplatin, revealed a synergistic interaction (Combination Index < 1) on NCI-H460 and H460-R9A (ST1926-resistant sub-line) cell growth. The in vivo oral administration of MIR002 or MIR144 showed a potent antitumor activity, with a Tumor Growth Inhibition comprised between 60 and 100% in a series of human and murine solid and hematological tumors (human MM473 and MM432 Pleural Mesothelioma, H460 and H460R9A NSCLC, A2780-Dx and A2780-DDP ovarian carcinomas, NB-4 Acute Promyelocitic leukemia and Murine EL-4 Lymphoma) xenografted in nude and immunocompetent mice. The strongest antitumor effect of MIR144 was observed in immunocompetent mice rather than in nude mice suggesting that an immunomodulatory effect, along with the direct antiproliferative activity, contributes to tumor inhibition. Further analysis confirmed that MIR144 antitumor activity involves the induction/activation of several components of the host immune system, both at humoral and cellular levels. The large spectrum of antitumor activity, together with the high tolerability observed, open the possibility for their clinical investigation in different population of cancer patients.

Citation Format: Claudio Pisano, Lucio Merlini, Sergio Penco, Raffaella Cincinelli, Nadine Darwiche, Mario B. Guglielmi, Ilaria La Porta, Maddalena Pizzulo, Federica Prosperi, Giacomo Signorino, Fabiana Colelli, Francesco Cardile, Laura Focareta, Alessandra Fucci, Egildo L. D'Andrea, Assunta Riccio, Sabrina Dallavalle. Host antitumor immune response activated by Dual POLA1-HDAC11 inhibitors endowed with a large spectrum of antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3096.

Hybrid topoisomerase I and HDAC inhibitors as dual action anticancer agents

Recent studies have shown that HDAC inhibitors act synergistically with camptothecin derivatives in combination therapies. To exploit this synergy, new hybrid molecules targeting simultaneously topoisomerase I and HDAC were designed. In particular, a selected multivalent agent containing a camptothecin and a SAHA-like template showed a broad spectrum of antiproliferative activity, with IC₅₀ values in the nanomolar range. Preliminary in vivo results indicated a strong antitumor activity on human mesothelioma primary cell line MM473 orthotopically xenografted in CD-1 nude mice and very high tolerability.

Abstract 4848: Preclinical antitumor activity of novel DNA polymerase 1 (POLA1) inhibitors

The anti-proliferative and pro-apoptotic effects of Retinoid-Related Molecules (RRMs) are described as independent from Retinoids' receptors-mediated transcriptional activity. Prototypes of this class are CD437 and its more potent analogue ST1926, which have a strong antitumor activity by targeting DNA polymerase 1 alpha (POLA1) (Han et al. Nat Chem Biol. 2016; Abdel-Samad et al. AJCR, in press).

With aim to identify new RRMs with an improved pharmacological profile, we synthetized and screened a library of RRMs for their antitumor properties and inhibitory activity on POLA1. From this screening, four molecules, MIR002, MIR020, MIR072 and MIR075, were selected. All exert a potent anti-proliferative effect, with G1/S arrest and apoptosis, in more than 50 cancer cell lines derived from human hematological and solid tumors. From a mechanistic point of view, these RRMs modulate, at different extent, POLA1 activity and/or expression.

Notably, NSCLC cells harboring POLA1-L764F mutation (H460-R9A), are resistant to both CD437 and ST1926 (IC50>50 higher than the one of wild type H460 cells), while they are sensitive to MIR002, showing for this RRM-derivative an improved/different pharmacological profile with respect to CD437 and ST1926.

Hints on the possibility of these new RRMs to be orally absorbed were obtained using cancer cells overexpressing or not P-glycoprotein (Pgp), known as the major player limiting the oral absorption of several chemotherapeutic agents. Results from these experiments revealed that the Tested compounds are not Pgp substrate thus suggesting the possibility for their absorption via oral route

MIR002 in vivo activity was assessed in tumors from Malignant Mesothelioma derived cells (MM487), and lung cancer cells (H460 and H460-R9A). In all the evaluated models, MIR002 induced a strong Tumor Growth Inhibition either alone or in combination with cisplatin (TGI>61% and TGI>80-100%, respectively).

The treatment of orthotopic models of malignant mesothelioma (MM487) with MIR072 in combination with Cisplatin, resulted in a impressive synergic antitumor activity if compared to Cisplatin monotherapy (TGI 95% vs 55%).

Tests on orthotopic transplants of hepatocellular carcinoma cells (HepG2), showed that MIR020 has significant antitumor effects (TGI 72%).

Finally, the activity of MIR075 was evaluated on glioblastoma luciferase-expressing cells (U-87MG) intracranically injected. Also this compound displayed a significant tumor growth inhibition (TGI 72%), as measured by IVIS imaging system.

Taken together, the results from in vitro and in vivo experiments indicate that this new class of RRMs, including MIR002, MIR072, MIR020, and MIR075, modulate POLA1 functions and activate pro-apoptotic pathways. The large spectrum of antitumor activity, together with the high tolerability observed, opens the possibility for their clinical investigation in different population of cancer patients.

Citation Format: Claudio Pisano, Lucio Merlini, Sergio Penco, Raffaella Cincinelli, Nadine Darwiche, Mario B. Guglielmi, Ilaria La Porta, Giacomo Signorino, Gabriele De Rubis, Fabiana Colelli, Francesco Cardile, Alessandra Fucci, Egildo L. D'Andrea, Sabrina Dallavalle. Preclinical antitumor activity of novel DNA polymerase 1 (POLA1) inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4848.

Tumor response of temozolomide in combination with morphine in a xenograft model of human glioblastoma

Despite multimodal treatments comprising, radiation therapy (RT) and chemotherapy with temozolomide (TMZ), the prognosis of glioblastoma multiforme (GBM) remains dismal and consolidated therapy yields a median survival of 14.6 months.

Blood Brain Barrier (BBB) mediated chemoresistance and high dose related toxicity make necessary the development of new therapeutic approach to sensitize GBM to TMZ.

The aim of the present study was to investigate the potential of the treatment morphine plus TMZ metronmic doses (1,77 and 0,9 mg/kg) in GBM therapy.

The effect of morphine, on tumor cell growth and P-glycoprothein (P-gp) activity, was investigate in in vitro models.

The results demonstrated that GBM cells growth is not influenced by morphine treatment and, for the first time, we show that morphine is an inhibitor of the activity of P-gp efflux transporter who is markedly expressed on BBB.

In vivo, response to the treatments TMZ plus morphine was investigated in an orthotopic nude mice model of GBM.

Animals treated with TMZ metronomic doses showed a significant tumor growth inhibition compared to untreated mice and association with morphine appears to improve TMZ efficacy.

Moreover, the combination of morphine with lower dose of TMZ result in a cytostatic effect on tumor growth over the period of the pharmacological treatments.

In conclusion this novel approach could be a successful strategy to overcome chemoresistance and side effects TMZ mediated, reducing drug dosage and improving long term response, in GBM therapy.

Abstract 5155: Targeting nucleolin with doxorubicin-containing nanoparticle induces a significant tumor growth inhibition in an orthotopic animal model of standard of care-resistant mesothelioma

Mesothelioma is a malignant tumor of the mesothelium, the thin lining of the surface of the body cavities and the organs within, and is often associated with asbestos exposure. It has a poor prognosis, with a mean overall survival of 8.8 months. Chemotherapy has been used for malignant pleural mesothelioma as an adjuvant treatment after surgical resection (often palliative) or in patients who have inoperable disease. A combination of cisplatin and pemetrexed remains as the current standard of care, with only a 9% 5-year survival rate. Herein, a novel targeted treatment for mesothelioma, based on a doxorubicin (DXR)-containing nanoparticle functionalized with the nucleolin-binding F3 peptide (named PEGASEMP), is proposed. It relies on nucleolin deregulated overexpression in cancer cells and the tumor microenvironment (endothelial cells from tumor blood vessels). Studies were performed in an orthotopic model of human mesothelioma. Mesothelioma cells harvested from a patient with disease progression who undergone chemotherapy, were stably transduced with luciferase-reporter gene, and orthotopically injected intrapleurally into female immunocompromised mice. Animals were randomly allocated to different treatment groups: vehicle, peptide-targeted DXR-containing nanoparticle (PEGASEMP) at 5.6 or 7 mg of DXR/kg alone (q7dx5w); cisplatin at 4.0 mg/kg alone or combined with PEGASEMP at 5.6 mg of DXR/kg (q7dx5w). A control group administered with the standard of care, a combination of cisplatin at 4.0 mg/kg (q7dx5w) plus pemetrexed at 100.0 mg/kg (q2dx3x5w) was also included. Bioluminescence was monitored weekly with live imaging using IVIS Spectrum In Vivo Imaging system. Peptide-targeted DXR-containing nanoparticle at 7.0 mg/kg enabled a tumor growth inhibition, by the end of the treatment, that was 183-fold higher than the standard of care. Moreover, treatment with DXR-containing nanoparticle targeting nucleolin, either at 5.6 or 7.0 mg/kg, enabled a 10- or 66-fold reduction of tumor burden, respectively, relative to non-treated mice. Conversely, treatment with the standard of care did not show any effect on tumor growth inhibition (being similar to the group injected with vehicle) nor on tumor burden. Importantly, DXR-containing nanoparticle targeting nucleolin, at the highest tested dose, enabled a marked decreased of the incidence of tumor infiltration into the chest cavity, as well as of the presence of severe lung lesions, as compared with the standard of care (57.1% versus 100% and 14.3% versus 50%, respectively). Overall, the novel mechanism of action associated with DXR-containing nanoparticle targeting nucleolin, enables a significant benefit in terms of efficacy (and safety) in the treatment of mesothelioma, as compared with the current standard of care, thus supporting future clinical evaluation.

Citation Format: Nuno André Fonseca, Vera Moura, Fabiana Colelli, Daniela Pesce, Francesco Cardile, Claudio Pisano, Sérgio Simões, João Nuno Moreira. Targeting nucleolin with doxorubicin-containing nanoparticle induces a significant tumor growth inhibition in an orthotopic animal model of standard of care-resistant mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5155. doi:10.1158/1538-7445.AM2017-5155

Morphine modulates doxorubicin uptake and improves efficacy of chemotherapy in an intracranial xenograft model of human glioblastoma

Morphine may alter the permeability of Blood-Brain Barrier (BBB), enhancing the access of molecules normally unable to cross it, as Doxorubicin (Dox). In addition, morphine seems to mediate the uptake of Dox into the brain by its reduced efflux mediated by P-glycoprotein (P-gp). We evaluated the antitumor efficacy of Dox plus morphine treatment by an orthotopic glioblastoma xenograft model. Foxn1 mice were injected with U87MG-luc cells in the left lobe of the brain and treated with Dox (5 mg/kg and 2.5 mg/kg, weekly) with or without morphine pretreatment (10 mg/kg, weekly). Bioluminescence imaging (BLI) was used to monitoring tumor growth and response to therapy. Additionally, we investigated the role of morphine on the uptake of Dox by MDCKII cells transfected with human MDR1 gene encoding for P-gp. The data demonstrate that only Dox 5 mg/kg determined a significant tumor regression while the lower dose (2.5 mg/kg) was not effective. However, if combined with morphine, the group treated with Dox 2.5 mg/kg showed a decreasing tumor growth. The average BLI for Dox 2.5 mg/kg plus morphine was 5 fold lower than Dox 2.5 mg/kg alone (P=0.0053) and 8 fold lower than vehicle (P=0.0004). Additionally, Dox increased in MDCKII-P-gp transfected cells only in the presence of morphine with a significantly higher level comparing control group (3.84) vs Dox plus morphine group (12.29, P<0.05). Our results indicate that Dox alone and in combination with morphine appear to be effective in controlling the growth of glioblastoma in a xenograft mouse model.

Recognition of fungal RNA by TLR7 has a nonredundant role in host defense against experimental candidiasis

Despite convincing evidence for involvement of members of the Toll-like receptor (TLR) family in fungal recognition, little is known of the functional role of individual TLRs in antifungal defenses. We found here that TLR7 was partially required for the induction of IL-12 (IL-12p70) by Candida albicans or Saccharomyces cerevisiae. Moreover, the IL-12p70 response was completely abrogated in cells from 3d mice, which are unable to mobilize TLRs to endosomal compartments, as well as in cells from mice lacking either the TLR adaptor MyD88 or the IRF1 transcription factor. Notably, purified fungal RNA recapitulated IL-12p70 induction by whole yeast. Although RNA could also induce moderate TLR7-dependent IL-23 and tumor necrosis factor-alpha (TNF-α) secretion, TLR7 and other endosomal TLRs were redundant for IL-23 or TNF-α induction by whole fungi. Importantly, mice lacking TLR7 or IRF1 were hypersusceptible to systemic C. albicans infection. Our data suggest that IRF1 is downstream of a novel, nonredundant fungal recognition pathway that has RNA as a major target and requires phagosomal recruitment of intracellular TLRs. This pathway differs from those involved in IL-23 or TNF-α responses, which we show here to be independent from translocation of intracellular TLRs, phagocytosis, or phagosomal acidification.

Activation of the NLRP3 inflammasome by group B streptococci

Group B Streptococcus (GBS) is a frequent agent of life-threatening sepsis and meningitis in neonates and adults with predisposing conditions. We tested the hypothesis that activation of the inflammasome, an inflammatory signaling complex, is involved in host defenses against this pathogen. We show in this study that murine bone marrow-derived conventional dendritic cells responded to GBS by secreting IL-1β and IL-18. IL-1β release required both pro-IL-1β transcription and caspase-1-dependent proteolytic cleavage of intracellular pro-IL-1β. Dendritic cells lacking the TLR adaptor MyD88, but not those lacking TLR2, were unable to produce pro-IL-1β mRNA in response to GBS. Pro-IL-1β cleavage and secretion of the mature IL-1β form depended on the NOD-like receptor family, pyrin domain containing 3 (NLRP3) sensor and the apoptosis-associated speck-like protein containing a caspase activation and recruitment domain adaptor. Moreover, activation of the NLRP3 inflammasome required GBS expression of β-hemolysin, an important virulence factor. We further found that mice lacking NLRP3, apoptosis-associated speck-like protein, or caspase-1 were considerably more susceptible to infection than wild-type mice. Our data link the production of a major virulence factor by GBS with the activation of a highly effective anti-GBS response triggered by the NLRP3 inflammasome.