Multifaceted modes of action of the anticancer probiotic Enterococcus hirae

A deviated repertoire of the gut microbiome predicts resistance to cancer immunotherapy. Enterococcus hirae compensated cancer-associated dysbiosis in various tumor models. However, the mechanisms by which E. hirae restored the efficacy of cyclophosphamide administered with concomitant antibiotics remain ill defined. Here, we analyzed the multifaceted modes of action of this anticancer probiotic. Firstly, E. hirae elicited emigration of thymocytes and triggered systemic and intratumoral IFNγ-producing and CD137-expressing effector memory T cell responses. Secondly, E. hirae activated the autophagy machinery in enterocytes and mediated ATG4B-dependent anticancer effects, likely as a consequence of its ability to increase local delivery of polyamines. Thirdly, E. hirae shifted the host microbiome toward a Bifidobacteria-enriched ecosystem. In contrast to the live bacterium, its pasteurized cells or membrane vesicles were devoid of anticancer properties. These pleiotropic functions allow the design of optimal immunotherapies combining E. hirae with CD137 agonistic antibodies, spermidine, or Bifidobacterium animalis. We surmise that immunological, metabolic, epithelial, and microbial modes of action of the live E. hirae cooperate to circumvent primary resistance to therapy.

Oral administration of Akkermansia muciniphila elevates systemic antiaging and anticancer metabolites

The presence of Akkermansia muciniphila (Akk) in the human gut is associated with good health, leanness and fitness. Mouse experimentation has demonstrated positive effects for Akk, which counteracts aging, mediates antiobesity and antidiabetic effects, dampens inflammation and improves anticancer immunosurveillance. Clinical trials have confirmed antidiabetic effects for Akk. Here, we investigated the time-dependent effects of oral administration of Akk (which was live or pasteurized) and other bacteria to mice on the metabolome of the ileum, colon, liver and blood plasma. Metabolomics was performed by a combination of chromatographic and mass spectrometric methods, yielding a total of 1.637.227 measurements. Akk had major effects on metabolism, causing an increase in spermidine and other polyamines in the gut and in the liver. Pasteurized Akk (Akk-past) was more efficient than live Akk in elevating the intestinal concentrations of polyamines, short-chain fatty acids, 2-hydroxybutyrate, as well multiple bile acids, which also increased in the circulation. All these metabolites have previously been associated with human health, providing a biochemical basis for the beneficial effects of Akk.

Immunoprophylactic and immunotherapeutic control of hormone receptor-positive breast cancer

Hormone receptor (HR)+ breast cancer (BC) causes most BC-related deaths, calling for improved therapeutic approaches. Despite expectations, immune checkpoint blockers (ICBs) are poorly active in patients with HR+ BC, in part reflecting the lack of preclinical models that recapitulate disease progression in immunocompetent hosts. We demonstrate that mammary tumors driven by medroxyprogesterone acetate (M) and 7,12-dimethylbenz[a]anthracene (D) recapitulate several key features of human luminal B HR+HER2- BC, including limited immune infiltration and poor sensitivity to ICBs. M/D-driven oncogenesis is accelerated by immune defects, demonstrating that M/D-driven tumors are under immunosurveillance. Safe nutritional measures including nicotinamide (NAM) supplementation efficiently delay M/D-driven oncogenesis by reactivating immunosurveillance. NAM also mediates immunotherapeutic effects against established M/D-driven and transplantable BC, largely reflecting increased type I interferon secretion by malignant cells and direct stimulation of immune effector cells. Our findings identify NAM as a potential strategy for the prevention and treatment of HR+ BC.

Gut Bacteria Composition Drives Primary Resistance to Cancer Immunotherapy in Renal Cell Carcinoma Patients

BACKGROUND

The development of immune checkpoint blockade (ICB) has revolutionized the clinical outcome of renal cell carcinoma (RCC). Nevertheless, improvement of durability and prediction of responses remain unmet medical needs. While it has been recognized that antibiotics (ATBs) decrease the clinical activity of ICB across various malignancies, little is known about the direct impact of distinct intestinal nonpathogenic bacteria (commensals) on therapeutic outcomes of ICB in RCC.

OBJECTIVE

To evaluate the predictive value of stool bacteria composition for ICB efficacy in a cohort of advanced RCC patients.

DESIGN, SETTING, AND PARTICIPANTS

We prospectively collected fecal samples from 69 advanced RCC patients treated with nivolumab and enrolled in the GETUG-AFU 26 NIVOREN microbiota translational substudy phase 2 trial (NCT03013335) at Gustave Roussy. We recorded patient characteristics including ATB use, prior systemic therapies, and response criteria. We analyzed 2994 samples of feces from healthy volunteers (HVs). In parallel, preclinical studies performed in RCC-bearing mice that received fecal transplant (FMT) from RCC patients resistant to ICB (NR-FMT) allowed us to draw a cause-effect relationship between gut bacteria composition and clinical outcomes for ICB. The influence of tyrosine kinase inhibitors (TKIs) taken before starting nivolumab on the microbiota composition has also been assessed.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Metagenomic data (MG) from whole genome sequencing (WGS) were analyzed by multivariate and pairwise comparisons/fold ratio to identify bacterial fingerprints related to ATB or prior TKI exposure and patients' therapeutic response (overall response and progression-free survival), and compared with the data from cancer-free donors.

RESULTS AND LIMITATIONS

Recent ATB use (n = 11; 16%) reduced objective response rates (from 28% to 9%, p < 0.03) and markedly affected the composition of the microbiota, facilitating the dominance of distinct species such as Clostridium hathewayi, which were also preferentially over-represented in stools from RCC patients compared with HVs. Importantly, TKIs taken prior to nivolumab had implications in shifting the microbiota composition. To establish a cause-effect relationship between gut bacteria composition and ICB efficacy, NR-FMT mice were successfully compensated with either FMT from responding RCC patients or beneficial commensals identified by WGS-MG (Akkermansia muciniphila and Bacteroides salyersiae).

CONCLUSIONS

The composition of the microbiota is influenced by TKIs and ATBs, and impacts the success of immunotherapy. Future studies will help sharpen the role of these specific bacteria and their potential as new biomarkers.

PATIENT SUMMARY

We used quantitative shotgun DNA sequencing of fecal microbes as well as preclinical models of fecal or bacterial transfer to study the association between stool composition and (pre)clinical outcome to immune checkpoint blockade. Novel insights into the pathophysiological relevance of intestinal dysbiosis in the prognosis of kidney cancer may lead to innovative therapeutic solutions, such as supplementation with probiotics to prevent primary resistance to therapy.

Lurbinectedin synergizes with immune checkpoint blockade to generate anticancer immunity

Systemic treatment with the active transcription inhibitor lurbinectedin aims at inducing tumor cell death in hyperproliferative neoplasms. Here we show that cell death induced by lurbinectedin reinstates and enhances systemic anticancer immune responses. Lurbinectedin treatment showed traits of immunogenic cell death, including the exposure of calreticulin, the release of ATP, the exodus of high mobility group box 1 (HMGB1) and type 1 interferon responses in vitro. Lurbinectedin treated cells induced antitumor immunity when injected into immunocompetent animals and treatment of transplanted fibrosarcomas reduced tumor growth in immunocompetent yet not in immunodeficient hosts. Anticancer effects resulting from lurbinectedin treatment were boosted in combination with PD-1 and CTLA-4 double immune checkpoint blockade (ICB), and lurbinectedin combined with double ICB exhibited strong antineoplastic effects. Cured animals exhibited long term immune memory effects that rendered them resistant to rechallenge with syngeneic tumors underlining the potency of combination therapy with lurbinectedin.

Therapeutic Effect of Irreversible Electroporation in Combination with Poly-ICLC Adjuvant in Preclinical Models of Hepatocellular Carcinoma

PURPOSE

To evaluate the therapeutic efficacy of irreversible electroporation (IRE) combined with the intratumoral injection of the immunogenic adjuvant poly-ICLC (polyinosinic-polycytidylic acid and poly-L-lysine, a dsRNA analog mimicking viral RNA) inmediately before IRE.

MATERIALS AND METHODS

Mice and rabbits bearing hepatocellular carcinoma tumors (Hepa.129 and VX2 tumor models, respectively) were treated with IRE (2 pulses of 2500V), with poly-ICLC, or with IRE + poly-ICLC combination therapy. Tumor growth in mice was monitored using a digital caliper and by computed tomography in rabbits.

RESULTS

Intratumoral administration of poly-ICLC immediately before IRE elicited shrinkage of Hepa.129 cell-derived tumors in 70% of mice, compared to 30% and 26% by poly-ICLC or IRE alone, respectively (P = .0004). This combined therapy induced the shrinkage of VX-2-based hepatocellular carcinoma tumors in 40% of rabbits, whereas no response was achieved by either individual treatment (P = .045). The combined therapy activated a systemic antitumor response able to inhibit the growth of other untreated tumors.

CONCLUSIONS

IRE treatment, immediately preceded by the intratumoral administration of an immunogenic adjuvant such as poly-ICLC, might enhance the antitumor effect of the IRE procedure. This combination might facilitate the induction of a long-term systemic response to prevent tumor relapses and the appearance of metastases.

Crizotinib-induced immunogenic cell death in non-small cell lung cancer

Immunogenic cell death (ICD) converts dying cancer cells into a therapeutic vaccine and stimulates antitumor immune responses. Here we unravel the results of an unbiased screen identifying high-dose (10 µM) crizotinib as an ICD-inducing tyrosine kinase inhibitor that has exceptional antineoplastic activity when combined with non-ICD inducing chemotherapeutics like cisplatin. The combination of cisplatin and high-dose crizotinib induces ICD in non-small cell lung carcinoma (NSCLC) cells and effectively controls the growth of distinct (transplantable, carcinogen- or oncogene induced) orthotopic NSCLC models. These anticancer effects are linked to increased T lymphocyte infiltration and are abolished by T cell depletion or interferon-γ neutralization. Crizotinib plus cisplatin leads to an increase in the expression of PD-1 and PD-L1 in tumors, coupled to a strong sensitization of NSCLC to immunotherapy with PD-1 antibodies. Hence, a sequential combination treatment consisting in conventional chemotherapy together with crizotinib, followed by immune checkpoint blockade may be active against NSCLC.

Certain chemotherapeutic agents can exert their anticancer effect through indirect immune-dependent mechanism. Here, the authors screen a library of tyrosine kinase inhibitors and show that crizotinib is an effective stimulator of immunogenic cell death and can potentiate the efficacy of immune checkpoint blockade.

Anticancer effects of anti-CD47 immunotherapy in vivo

The treatment of breast cancer largely depends on the utilization of immunogenic chemotherapeutics, which, as a common leitmotif, stimulate the exposure of calreticulin (CALR) on the surface of cancer cells, thereby facilitating their recognition by dendritic cells for the uptake of tumor-associated antigens and subsequent antigen cross-presentation to cytotoxic T cells. Breast cancer cells also express the calreticulin antagonist CD47, which inhibits tumor cell phagocytosis and consequently subverts anticancer immune responses. Here, we treated carcinogen-induced or transplantable mouse models of cancer by a CD47 blocking antibody that was at least as efficient as chemotherapy and that could be favorably combined with the anthracycline mitoxantrone in the context of carcinogen-induced orthotopic breast cancers. Monotherapy by CD47 blockade led to a reduction in tumor growth and an increase in overall survival. Of note, this treatment lead to a moderate depletion of M2 macrophages as well as close-to-complete elimination of regulatory T cells from the tumor bed, suggesting a strong favorable impact of CD47 blockade on the tumor microenvironment.

Oncolysis with DTT-205 and DTT-304 generates immunological memory in cured animals

Oncolytic peptides and peptidomimetics are being optimized for the treatment of cancer by selecting agents with high cytotoxic potential to kill a maximum of tumor cells as well as the capacity to trigger anticancer immune responses and hence to achieve long-term effects beyond therapeutic discontinuation. Here, we report on the characterization of two novel oncolytic peptides, DTT-205 and DTT-304 that both selectively enrich in the lysosomal compartment of cancer cells yet differ to some extent in their cytotoxic mode of action. While DTT-304 can trigger the aggregation of RIP3 in ripoptosomes, coupled to the phosphorylation of MLKL by RIP3, DTT-205 fails to activate RIP3. Accordingly, knockout of either RIP3 or MLKL caused partial resistance against cell killing by DTT-304 but not DTT-205. In contrast, both agents shared common features in other aspects of pro-death signaling in the sense that their cytotoxic effects were strongly inhibited by both serum and antioxidants, partially reduced by lysosomal inhibition with bafilomycin A1 or double knockout of Bax and Bak, yet totally refractory to caspase inhibition. Both DTT-304 and DTT-205 caused the exposure of calreticulin at the cell surface, as well as the release of HMGB1 from the cells. Mice bearing established subcutaneous cancers could be cured by local injection of DTT-205 or DTT-304, and this effect depended on T lymphocytes, as it led to the establishment of a long-term memory response against tumor-associated antigens. Thus, mice that had been cured from cancer by the administration of DTT compounds were refractory against rechallenge with the same cancer type several months after the disappearance of the primary lesion. In summary, DTT-205 and DTT-304 both have the capacity to induce immunotherapeutic oncolysis.

Toll like receptor 7 expressed by malignant cells promotes tumor progression and metastasis through the recruitment of myeloid derived suppressor cells

In non-small cell lung carcinoma (NSCLC), stimulation of toll-like receptor 7 (TLR7), a receptor for single stranded RNA, is linked to tumor progression and resistance to anticancer chemotherapy. However, the mechanism of this effect has been elusive. Here, using a murine model of lung adenocarcinoma, we demonstrate a key role for TLR7 expressed by malignant (rather than by stromal and immune) cells, in the recruitment of myeloid derived suppressor cells (MDSCs), induced after TLR7 stimulation, resulting in accelerated tumor growth and metastasis. In adenocarcinoma patients, high TLR7 expression on malignant cells was associated with poor clinical outcome, as well as with a gene expression signature linked to aggressiveness and metastastic dissemination with high abundance of mRNA encoding intercellular adhesion molecule 1 (ICAM-1), cytokeratins 7 and 19 (KRT-7 and 19), syndecan 4 (SDC4), and p53. In addition, lung tumors expressing high levels of TLR7 have a phenotype of epithelial mesenchymal transition with high expression of vimentin and low abundance of E-cadherin. These data reveal a crucial role for cancer cell-intrinsic TLR7 expression in lung adenocarcinoma progression.

Abstract 5752: Protumoral and pro-metastatic effects of TLR7 in lung cancer

TLR7 agonists are currently under investigations for their ability to enhance anti-tumor immune responses. However, in some tumor models, these agonists also stimulate tumor cells, which can express high levels of TLR7, a receptor for single-stranded RNA [1]. We have demonstrated that stimulation of lung tumor cell lines expressing TLR7 with synthetic TLR7 agonists led to upregulation of the antiapoptotic protein Bcl-2, tumor cell survival and chemoresistance [2]. In Non-Small-Cell Lung Carcinoma (NSCLC) cohorts of patients, we have observed high expression of TLR7 on tumor cells of 70% of patients, which conferred poor clinical outcome and was strongly associated with resistance to chemotherapy [3]. This pro-tumoral effect of TLR7 has been validated in murine models in which the injection of TLR7 agonists in NOD/SCID mice, in C57BL/6 wild-type or in TLR7-deficient mice grafted with lung adenocarcinoma tumor cells led to increased tumor progression, increased lung metastasis, and resistance to chemotherapy. On the contrary, we demonstrated that TLR7 antagonist injection led to antitumoral effect. Additionally, TLR7 stimulation resulted in a significant increase of Myeloid-Derived Suppressor Cells (MDSC) in the tumor microenvironment. Depletion experiments of MDSC indicated that these cells are involved in the pro-tumoral effect induced upon TLR7 stimulation. Finally, we have demonstrated that the pro-tumoral effect of TLR7 stimulation, mediated by the MDSC recruitment, was independent of TLR7 stimulation on immune cells. Our results reveal the mechanism by which TLR7 stimulation induce the pro-tumoral effect in mice, and open the way to the development of novel cancer therapeutics including TLR7 inhibitors, for NSCLC patients. This results demonstrate the important role of TLR7 in lung tumor progression. Knowing that natural ligands of TLR7 are ssRNA, we suppose that this effect could be linked to viral infections or RNA released in the tumor microenvironment. [1] Dajon, et al. Immunobiologie. 2016 [2] Cherfils-Vicini J, et al. J Clin Invest. 2010 [3] Chatterjee J, et al. Cancer Res. 2014

Citation Format: Marion Dajon, Kristina Iribarren, Marco Alifano, Diane Damotte, Isabelle Cremer. Protumoral and pro-metastatic effects of TLR7 in lung cancer [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 5752.

Epigenetic anticancer agents cause HMGB1 release in vivo

A systematic search for anticancer agents that may induce the release of high mobility group box 1 (HMGB1) protein from cells into the extracellular space has led to the identification of several drugs capable of elevating plasma HMGB1 levels in vivo, in mice. Such agents include bona-fide immunogenic cell death inducers such as oxaliplatin, as well as a series of epigenetic modifiers, namely azacitidine, decitabine, and suberoylanilide hydroxamic acid (SAHA).

Immunomodulatory Properties of Carvone Inhalation and Its Effects on Contextual Fear Memory in Mice

A complex network of interactions exists between the immune, the olfactory, and the central nervous system (CNS). Inhalation of different fragrances can affect immunological reactions in response to an antigen but also may have effects on the CNS and cognitive activity. We performed an exploratory study of the immunomodulatory ability of a series of compounds representing each of the 10 odor categories or clusters described previously. We evaluated the impact of each particular odor on the immune response after immunization with the model antigen ovalbumin in combination with the TLR3 agonist poly I:C. We found that some odors behave as immunostimulatory agents, whereas others might be considered as potential immunosuppressant odors. Interestingly, the immunomodulatory capacity was, in some cases, strain-specific. In particular, one of the fragrances, carvone, was found to be immunostimulatory in BALB/c mice and immunosuppressive in C57BL/6J mice, facilitating or impairing viral clearance, respectively, in a model of a viral infection with a recombinant adenovirus. Importantly, inhalation of the odor improved the memory capacity in BALB/c mice in a fear-conditioning test, while it impaired this same capacity in C57BL/6J mice. The improvement in memory capacity in BALB/c was associated with higher CD3⁺ T cell infiltration into the hippocampus and increased local expression of mRNA coding for IL-1β, TNF-α, and IL-6 cytokines. In contrast, the memory impairment in C57BL/6 was associated with a reduction in CD3 numbers and an increase in IFN-γ. These data suggest an association between the immunomodulatory capacity of smells and their impact on the cognitive functions of the animals. These results highlight the potential of studying odors as therapeutic agents for CNS-related diseases.

The oncolytic compound LTX-401 targets the Golgi apparatus

This corrects the article DOI: 10.1038/cdd.2016.86.

Gut microbiome influences efficacy of PD-1-based immunotherapy against epithelial tumors

Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 axis induce sustained clinical responses in a sizable minority of cancer patients. We found that primary resistance to ICIs can be attributed to abnormal gut microbiome composition. Antibiotics inhibited the clinical benefit of ICIs in patients with advanced cancer. Fecal microbiota transplantation (FMT) from cancer patients who responded to ICIs into germ-free or antibiotic-treated mice ameliorated the antitumor effects of PD-1 blockade, whereas FMT from nonresponding patients failed to do so. Metagenomics of patient stool samples at diagnosis revealed correlations between clinical responses to ICIs and the relative abundance of Akkermansia muciniphila Oral supplementation with A. muciniphila after FMT with nonresponder feces restored the efficacy of PD-1 blockade in an interleukin-12-dependent manner by increasing the recruitment of CCR9⁺CXCR3⁺CD4⁺ T lymphocytes into mouse tumor beds.

TNFR2/BIRC3-TRAF1 signaling pathway as a novel NK cell immune checkpoint in cancer

Natural Killer (NK) cells control metastatic dissemination of murine tumors and are an important prognostic factor in several human malignancies. However, tumor cells hijack many of the NK cell functional features compromising their tumoricidal activity. Here, we show a deleterious role of the TNFα/TNFR2/BIRC3/TRAF1 signaling cascade in NK cells from the tumor microenvironment (TME). TNFα induces BIRC3/cIAP2 transcripts and reduces NKp46/NCR1 transcription and surface expression on NK cells, promoting metastases dissemination in mice and poor prognosis in GIST patients. NKp30 engagement, by promoting the release of TNFα, also contributes to BIRC3 upregulation, and more so in patients expressing predominantly NKp30C isoforms. These findings reveal that in the absence of IL-12 or a Th1-geared TME, TNFα can be considered as a negative regulatory cytokine for innate effectors.

Abstract 5128: Induction of immunogenic cell death and tumor regression in murine animal models by a novel cytolytic compound, LTX-401

LTX-401 is a de novo designed cytolytic compound that shares many chemical features with anticancer peptides, such as amphipathicity, hydrophobicity and overall net charge. In vitro cytotoxicity studies revealed that LTX-401 was highly active against a panel of malignant cells including murine and human cancer cell lines while displaying selectivity towards human red blood cells. Furthermore, LTX-401 was found to induce immunogenic cell death as demonstrated by the release of Damage-Associated Molecular Pattern molecules, or ‘danger signals’, such as High-Mobility Group Box-1 protein, ATP and cytochrome c. Flow cytometric and confocal microscopy studies also demonstrated reduced signal from lysosomal dye Lysotracker-DND-26, hence indicating loss of lysosomal integrity upon induction of cell death. The latter was supported using transmission electron microscopy, showing distinct morphological characteristics of necrosis. Moreover, at low concentrations, LTX-401 selectively enriched in the Golgi apparatus and initiated a lethal signaling event that in part could be inhibited by Brefeldin A. Complete tumor regression has been obtained in several rodent models, including the B16 mouse melanoma model and the JM1 rat hepatocellular carcinoma model by intratumoral injection with LTX-401. Additionally, previously cured animals showed protection against rechallenge with live tumor cells, indicating the induction of tumor-specific immune memory. The increased survival benefit of LTX-401-treated animals provides a rationale for further evaluation of the compound as an immunotherapeutic agent against solid malignancies.

Citation Format: Brynjar Mauseth, Liv-Marie Eike, Ji-Hua Shi, Ketil Camilio, Heng Zhou, Allan Sauvat, Lígia C Gomes-da-Silva, Sylvèr Durand, Sabrina Forveille, Kristina Iribarren, Takahiro Yamazaki, Sylvie Souquere, Lucillia Bezu, Kevin Müller, Marion Leduc, Peng Liu, Liwei Zhao, Aurélien Marabelle, Laurence Zitvogel, Oliver Kepp, Guido Kroemer, Øystein Rekdal, Pål-Dag Line, Baldur Sveinbjørnsson. Induction of immunogenic cell death and tumor regression in murine animal models by a novel cytolytic compound, LTX-401 [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 5128. doi:10.1158/1538-7445.AM2017-5128

Abstract A124: Protumoral effects of TLR7 in lung tumors

TLR7 agonists are currently under investigations for their ability to enhance anti-tumor immune responses. However, in some tumor models, these agonists can also stimulate tumor cells, which express high levels of TLR7. In Non-Small-Cell Lung Carcinoma (NSCLC), we have demonstrated that high expression of TLR7 conferred poor clinical outcome and was strongly associated with resistance to chemotherapy. This protumorigenic effect of TLR7 has been validated in murine models in which the injection of TLR7 agonists in NOD/SCID mice, in C57BL/6 wild-type or in TLR7-deficient mice grafted with lung adenocarcinoma tumor cells led to increased tumor progression and chemotherapeutic resistance. TLR7 stimulation resulted in a significant increase of Myeloid-Derived Suppressor Cells (MDSC) in the tumor microenvironment. Depletion experiments of MDSC indicated that these cells appeared to be responsible to the in vivo pro-tumoral effect induced upon TLR7 stimulation. Finally, we have demonstrated that the pro-tumoral effect of TLR7 stimulation, mediated by the MDSC recruitment, was independent of stimulation of TLR7 of immune cells.

Our results reveal the mechanism by which TLR7 stimulation induce the pro-tumoral effect in mice, and open the way to the development of novel cancer therapeutics including TLR7 inhibitors, for NSCLC patients.

Citation Format: Marion Dajon, Kristina Iribarren, Isabelle Cremer. Protumoral effects of TLR7 in lung tumors [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A124.

The oncolytic compound LTX-401 targets the Golgi apparatus

LTX-401 is an oncolytic amino acid derivative with potential immunogenic properties. Here, we demonstrate that LTX-401 selectively destroys the structure of the Golgi apparatus, as determined by means of ultrastructural analyses and fluorescence microscopic observation of cells expressing Golgi-targeted GFP reporters. Subcellular fractionation followed by mass spectrometric detection revealed that LTX-401 selectively enriched in the Golgi rather than in mitochondria or in the cytosol. The Golgi-dissociating agent Brefeldin A (BFA) reduced cell killing by LTX-401 as it partially inhibited LTX-401-induced mitochondrial release of cytochrome c and the activation of BAX. The cytotoxic effect of LTX-401 was attenuated by the double knockout of BAX and BAK, as well as the mitophagy-enforced depletion of mitochondria, yet was refractory to caspase inhibition. LTX-401 induced all major hallmarks of immunogenic cell death detectable with biosensor cell lines including calreticulin exposure, ATP release, HMGB1 exodus and a type-1 interferon response. Moreover, LTX-401-treated tumors manifested a strong lymphoid infiltration. Altogether these results support the contention that LTX-401 can stimulate immunogenic cell death through a pathway in which Golgi-localized LTX-401 operates upstream of mitochondrial membrane permeabilization.

Toll-like receptor stimulation in cancer: A pro- and anti-tumor double-edged sword

Toll-like receptors (TLRs) are a family of transmembrane receptors that recognize various pathogen- and damage-associated molecular pattern molecules playing an important role in inflammation by activating NF-кB. TLRs, mainly expressed by innate immune cells, are involved in inducing and regulating adaptive immune responses. However, the expression of TLRs has also been observed in many tumors, and their stimulation results in tumor progression or regression, depending on the TLR and tumor type. Here we review the role of TLRs in conferring anti- or pro-tumoral effects. The anti-tumoral effects can result from direct induction of tumor cell death and/or activation of efficient anti-tumoral immune responses, and the pro-tumoral effects may be due to inducing tumor cell survival and proliferation or by acting on suppressive or inflammatory immune cells in the tumor microenvironment.

Calreticulin expression: Interaction with the immune infiltrate and impact on survival in patients with ovarian and non-small cell lung cancer

Loss of expression of calreticulin (CALR) has been detected by immunohistochemistry in a fraction of non-small cell lung cancers (NSCLC) and has been demonstrated to have a major negative prognostic impact on overall patient survival. Here, we analyzed the impact of CALR expression levels detected by microarray finding a positive correlation between CALR and the expression of a metagene indicating the presence of cytotoxic T lymphocytes (CTL) in NSCLC and ovarian cancer. In addition, we detected a positive correlation with a metagene suggestive of activated dendritic cell (aDC) infiltration in ovarian cancer. Combination of two parameters (CALR + DC (dendritic cell) in NSCL and CALR + aDC in ovarian cancer) or three parameters (CALR + CTL + DC in NSCL and CALR + CTL + aDC in ovarian cancer) had a significant impact on overall patient survival in NSCL (Adenoconsortium) and ovarian cancer (TCGA collection), allowing the stratification of patients in high-risk and low-risk groups. In addition, CALR and aDC alone have a significant impact on overall survival in ovarian cancer. In contrast, in mammary, colorectal and prostate cancer, CALR had no impact on patient survival if analyzed alone or in combination with the immune infiltrate. In addition, CALR correlates with CTL infiltrate in three cancer types (colorectal, breast, ovarian). Altogether, these results support the contention that, at least in some cancers, loss of CALR expression may negatively affect immunosurveillance, thereby reducing patient survival.

Trial Watch: Immunostimulation with Toll-like receptor agonists in cancer therapy

Accumulating preclinical evidence indicates that Toll-like receptor (TLR) agonists efficiently boost tumor-targeting immune responses (re)initiated by most, if not all, paradigms of anticancer immunotherapy. Moreover, TLR agonists have been successfully employed to ameliorate the efficacy of various chemotherapeutics and targeted anticancer agents, at least in rodent tumor models. So far, only three TLR agonists have been approved by regulatory agencies for use in cancer patients. Moreover, over the past decade, the interest of scientists and clinicians in these immunostimulatory agents has been fluctuating. Here, we summarize recent advances in the preclinical and clinical development of TLR agonists for cancer therapy.

Dual roles of TLR7 in the lung cancer microenvironment

Toll-like receptor 7 (TLR7) agonists are under investigation for their ability to enhance antitumor immune responses. However, these agonists can also stimulate TLR7-expressing tumor cells. High TLR7 expression in the primary tumor confers poor clinical outcome and resistance to chemotherapy in lung cancer patients. This protumorigenic effect of TLR7 has been validated in murine models of lung carcinoma.

TLR7 promotes tumor progression, chemotherapy resistance, and poor clinical outcomes in non-small cell lung cancer

Toll-like receptors (TLR) recognize pathogen molecules and danger-associated signals that stimulate inflammatory processes. TLRs have been studied mainly in antigen-presenting cells, where they exert important immune regulatory functions, but they are also expressed by epithelial tumor cells, where they have been implicated in tumor progression. In this study, we demonstrate that the injection of TLR7 agonist in NOD/SCID mice, in C57BL/6 wild-type, and TLR7-deficient mice grafted with lung adenocarcinoma tumor cells leads to increased tumor progression and chemotherapeutic resistance. In patients with non-small cell lung cancer, expression analyses revealed that high TLR7 expression was strongly associated with resistance to neoadjuvant chemotherapy and poor clinical outcomes. Our findings delineate a crucial role for TLR7 in lung cancer physiopathology. Cancer Res; 74(18); 5008-18. ©2014 AACR.