Anticancer Immunosurveillance Research Articles

Predictability of B cell clonal persistence and immunosurveillance in breast cancer

B cells and T cells are important components of the adaptive immune system and mediate anticancer immunity. The T cell landscape in cancer is well characterized, but the contribution of B cells to anticancer immunosurveillance is less well explored. Here we show an integrative analysis of the B cell and T cell receptor repertoire from individuals with metastatic breast cancer and individuals with early breast cancer during neoadjuvant therapy. Using immune receptor, RNA and whole-exome sequencing, we show that both B cell and T cell responses seem to coevolve with the metastatic cancer genomes and mirror tumor mutational and neoantigen architecture. B cell clones associated with metastatic immunosurveillance and temporal persistence were more expanded and distinct from site-specific clones. B cell clonal immunosurveillance and temporal persistence are predictable from the clonal structure, with higher-centrality B cell antigen receptors more likely to be detected across multiple metastases or across time. This predictability was generalizable across other immune-mediated disorders. This work lays a foundation for prioritizing antibody sequences for therapeutic targeting in cancer.

Inulin enriched diet reinforces cancer immunosurveillance via γδ T cell activation

Abstract Gut microbiota is now recognized as a key player impacting the host’s anti-cancer immunosurveillance and ability to respond to immunotherapy. Its optimal modulation for preventive and therapeutic purposes is very appealing. Since diet is one of the most powerful modulators of the microbiota, nutritional interventions could be leveraged to improve host immunity. The present study aims to analyze the anticancer properties of inulin, a fiber known to promote bacteria described as immunostimulatory. The effects of inulin complementation were tested in mice fed an inulin-enriched diet for 2 weeks before tumor implantation. In the three tumor models used (melanoma, fibrosarcoma, and colorectal cancer), inulin consumption inhibited tumor growth by 80% compared to controls. Tumor-infiltrated immunity analysis showed that inulin triggers an enhanced Th1-polarized CD4 +CD8 +and γδ T cell-mediated antitumor response. In the gut, inulin consumption favored Bifidobacterium relative abundance, and strengthened gut immunity, by increasing the proportion of colonic IFNγ-producing γδ intra-epithelial T lymphocytes as well as the expression of genes involved in inflammation. In addition, we showed that the inulin-mediated anti-tumor effect is gut microbiota- and γδ T cell-dependent, as both antibiotic treatment and in vivo blocking of γδ TcR abrogate inulin efficacy. Overall, our data identified γδ T cells as a critical immune subset, mandatory for inulin-mediated antitumor immunity in vivo. This supports and rationalizes the use of a prebiotic approache as well as the development of immunotherapies targeting γδ T cells in cancer prevention and treatment. This work is supported by GEFLUC Dauphiné-Savoie, Ligue contre le Cancer Comité Isère, Ligue contre le Cancer Comité Savoie, Université Grenoble Alpes IDEX Initiatives de Recherche Stratégiques. Emilie Boucher is supported by a grant salary from the French Ministry of Higher Education, Research and Innovation.

1261 ER stress facilitates anti-cancer immunosurveillance and improves immunotherapy efficacy in melanoma

1261 ER stress facilitates anti-cancer immunosurveillance and improves immunotherapy efficacy in melanoma

Spermidine as a promising anticancer agent: Recent advances and newer insights on its molecular mechanisms.

Spermidine is a naturally occurring polyamine compound found in semen. It is also found in several plant sources and boasts a remarkable biological profile, particularly with regards to its anticancer properties. Spermidine specifically interferes with the tumour cell cycle, resulting in the inhibition of tumor cell proliferation and suppression of tumor growth. Moreover, it also triggers autophagy by regulating key oncologic pathways. The increased intake of polyamines, such as spermidine, can suppress oncogenesis and slow the growth of tumors due to its role in anticancer immunosurveillance and regulation of polyamine metabolism. Spermidine/spermine N-1-acetyltransferase (SSAT) plays a critical role in polyamine homeostasis and serves as a diagnostic marker in human cancers. Chemically modified derivatives of spermidine hold great potential for prognostic, diagnostic, and therapeutic applications against various malignancies. This review discusses in detail the recent findings that support the anticancer mechanisms of spermidine and its molecular physiology.

Abstract 1840: Methylmalonic acid accumulation suppresses CD8+ T cell activation and contributes to age-induced immunosuppression

Abstract Deregulation of cytotoxic CD8+ T cells is a feature of the aging process with important consequences for anti-tumor immunity and consequently affects tumor initiation, progression, and response to immunotherapies. However, our understanding of how the aging process affects CD8+ T cells remains incomplete. Vitamin B12 deficiency is also a feature of old age caused by a well-recognized decrease in vitamin absorption. Interestingly, clinical studies have reported a significant decline in CD8+ T cells in individuals with vitamin B12 deficiency, suggesting that vitamin B12 levels might be a mechanistic link between aging and deregulation of CD8+ T cells. An important and often overlooked consequence of vitamin B12 deficiency is an elevation of methylmalonic acid (MMA) in circulation. Our laboratory has previously established a critical role for age-induced MMA in promoting progression into metastatic disease of breast and lung cancers, which coincided with a robust immunosuppressive signature. Here, we demonstrate that exposure of CD8+ T cells to MMA or culture of CD8+ T cells in the absence of vitamin B12 reduces T cell activation, thereby decreasing T cell numbers and effector function. Conversely, supplementation of vitamin B12 on CD8+ T cells isolated from old mice enhances their ability to activate and increases T cell numbers. Evaluation of the effects of MMA on the CD8+ T cells metabolome revealed a decrease in antioxidant levels, including a pronounced reduction in vitamin C and reduced glutathione, which were accompanied by an increase in both superoxide and hydrogen peroxide, suggesting that an increase in reactive oxygen species might be the link between MMA and CD8+ T cell dysfunction. Together, these results put forward the idea that MMA is an important regulator of immune cell function and that supplementation of vitamin B12 in older people and individuals diagnosed with vitamin B12 deficiency may function as an important strategy to improve immune cytotoxic responses and thereby increase anti-cancer immunosurveillance and the effectiveness of certain immunotherapies. Citation Format: Joanne D. Tejero, Stanislav Drapela, Juan Fernandez-Garcia, Sarah-Maria Fendt, Didem Ilter, Ana P. Gomes. Methylmalonic acid accumulation suppresses CD8+ T cell activation and contributes to age-induced immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1840.

Oleic Acid Dissolves cGAS-DNA Phase Separation to Inhibit Immune Surveillance.

Phase separation (PS) is a fundamental principle in diverse life processes including immunosurveillance. Despite numerous studies on PS, little is known about its dissolution. Here, it is shown that oleic acid (OA) dissolves the cyclic GMP-AMP synthase (cGAS)-deoxyribonucleic acid (DNA) PS and inhibits immune surveillance of DNA. As solvent components control PS and metabolites are abundant cellular components, it is speculated that some metabolite(s) may dissolve PS. Metabolite-screening reveals that the cGAS-DNA condensates formed via PS are markedly dissolved by long-chain fatty acids, including OA. OA revokes intracellular cGAS-PS and DNA-induced activation. OA attenuates cGAS-mediated antiviral and anticancer immunosurveillance. These results link metabolism and immunity by dissolving PS, which may be targeted for therapeutic interventions.

Abstract F3-2: Fasting and caloric restriction mimetics stimulate anticancer immunosurveillance

Abstract Fasting and caloric restriction induce metabolic and neuroendocrine changes that have major anti-inflammatory and immunostimulatory effects. Some of these effects are mediated by a raise of ketone bodies (such as 3-hydroxybutyrate) and a decrease in circulating insulin-like growth factor-1 (IGF1), meaning that administration of 3-hydroxybutyrate and pharmacological inhibition of IGF1 receptor can mimic some of the beneficial effects of fasting on anticancer immunosurveillance. "Caloric restriction mimetics" (CRMs) are small molecules that induce autophagy through the same pathways that are activated by fasting, including the reduction of cytoplasmic protein acetylation. We have accumulated evidence that CRMs can stimulate anticancer immunosurveillance either as single agents (for the prevention of malignant disease) or in combination with chemotherapy and/or immune checkpoint blockade (for the treatment of established cancers). In preclinical experiments, fasting and CRMs have also been used for the prevention or treatment of hormone-induced breast cancer, and these effects are coupled to an increase in the T lymphocyte-mediated anticancer immune response. We have developed an in vitro screening assay to identify novel pharmacological agents that act as CRMs. Such neo-CRMs can be successfully employed to improve anticancer immunosurveillance in preclinical experiments. Citation Format: Guido Kroemer. Fasting and caloric restriction mimetics stimulate anticancer immunosurveillance [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr F3-2.

Inulin prebiotic reinforces host cancer immunosurveillance via ɣδ T cell activation.

The gut microbiota is now recognized as a key parameter affecting the host's anti-cancer immunosurveillance and ability to respond to immunotherapy. Therefore, optimal modulation for preventive and therapeutic purposes is very appealing. Diet is one of the most potent modulators of microbiota, and thus nutritional intervention could be exploited to improve host anti-cancer immunity. Here, we show that an inulin-enriched diet, a prebiotic known to promote immunostimulatory bacteria, triggers an enhanced Th1-polarized CD4+ and CD8+ αβ T cell-mediated anti-tumor response and attenuates tumor growth in three preclinical tumor-bearing mouse models. We highlighted that the inulin-mediated anti-tumor effect relies on the activation of both intestinal and tumor-infiltrating ɣδ T cells that are indispensable for αβ T cell activation and subsequent tumor growth control, in a microbiota-dependent manner. Overall, our data identified these cells as a critical immune subset, mandatory for inulin-mediated anti-tumor immunity in vivo, further supporting and rationalizing the use of such prebiotic approaches, as well as the development of immunotherapies targeting ɣδ T cells in cancer prevention and immunotherapy.

The Role of Nutritional Modulation of Immune Function in Cancer – What About It?

In recent years there has been an increase in the number of new cases of cancer. Malnutrition in cancer patients is a consequence of the increase in inflammatory cytokines associated with cancer, metabolic alterations, and concomitant inadequate availability of nutrients, due to anorexia caused by the disease and systemic treatments. Nutrition can guide both the growth and progress of inflammatory disorders and their prevention and treatment. Irrevocably, it is indispensable to pair the diet with physical activity, balance nutritional status and prime a healthy lifestyle. An increased understanding of the instruments linked to nutrients and the immune system is a breathtaking and exceptional field for the future. The gut microbiota is now known as a fundamental factor disturbing the host´s anti-cancer immunosurveillance and capacity to respond to immunotherapy. Diet is one of the most powerful modulators of microbiota, and therefore nutritional intervention could be used to increase host anti-cancer immunity. A rising body of data has also highlighted that the gut microbiota may have a constructive impact on cancer prevention or treatment, particularly via improved host immunosurveillance of cancer as well as patients ‘capacity to respond to chemotherapy or immunotherapy. The sway of nutrition on the immune system is a territory that remains under investigation. Nutrition and immunity are closely related. An expanded understanding of the mechanisms connected to nutrients and the immune system is a breathtaking and gifted field for the future.

Cellular senescence enhances adaptive anticancer immunosurveillance

ABSTRACT Cancer therapy often induces senescence in some cancer cells. Senescent cells, due to their profoundly altered biology, may conceivably interact with the adaptive immune system in novel ways that may boost cancer immunosurveillance, triggering the clearance of both senescent and non-senescent neoplastic cells. In this regard, we have recently reported that senescent cancer cells exhibit potent antigenicity and adjuvanticity and can elicit strong CD8+ T cell-dependent anticancer effects when used as vaccination agents.

Interferon-gamma signaling promotes melanoma progression and metastasis.

Interferon-gamma (IFNG) has long been regarded as the flag-bearer for the anti-cancer immunosurveillance mechanisms. However, relatively recent studies have suggested a dual role of IFNG, albeit there is no direct experimental evidence for its potential pro-tumor functions. Here we provide in vivo evidence that treatment of mouse melanoma cell lines with Ifng enhances their tumorigenicity and metastasis in lung colonization allograft assays performed in immunocompetent syngeneic host mice, but not in immunocompromised host mice. We also show that this enhancement is dependent on downstream signaling via Stat1 but not Stat3, suggesting an oncogenic function of Stat1 in melanoma. The experimental results suggest that melanoma cell-specific Ifng signaling modulates the tumor microenvironment and its pro-tumorigenic effects are partially dependent on the γδ T cells, as Ifng-enhanced tumorigenesis was inhibited in the TCR-δ knockout mice. Overall, these results show that Ifng signaling may have tumor-promoting effects in melanoma by modulating the immune cell composition of the tumor microenvironment.

IRE1α overexpression in malignant cells limits tumor progression by inducing an anti-cancer immune response

ABSTRACT IRE1α is one of the three ER transmembrane transducers of the Unfolded Protein Response (UPR) activated under endoplasmic reticulum (ER) stress. IRE1α activation has a dual role in cancer as it may be either pro- or anti-tumoral depending on the studied models. Here, we describe the discovery that exogenous expression of IRE1α, resulting in IRE1α auto-activation, did not affect cancer cell proliferation in vitro but resulted in a tumor-suppressive phenotype in syngeneic immunocompetent mice. We found that exogenous expression of IRE1α in murine colorectal and Lewis lung carcinoma cells impaired tumor growth when syngeneic tumor cells were subcutaneously implanted in immunocompetent mice but not in immunodeficient mice. Mechanistically, the in vivo tumor-suppressive effect of overexpressing IRE1α in tumor cells was associated with IRE1α RNAse activity driving both XBP1 mRNA splicing and regulated IRE1-dependent decay of RNA (RIDD). We showed that the tumor-suppressive phenotype upon IRE1α overexpression was characterized by the induction of apoptosis in tumor cells along with an enhanced adaptive anti-cancer immunosurveillance. Hence, our work indicates that IRE1α overexpression and/or activation in tumor cells can limit tumor growth in immunocompetent mice. This finding might point toward the need of adjusting the use of IRE1α inhibitors in cancer treatments based on the predominant outcome of the RNAse activity of IRE1α.

Eliciting pyroptosis to fuel cancer immunotherapy: mechanisms and strategies.

Immune checkpoint blockade (ICB) therapy has recently shown promise in treating several malignancies. However, only a limited number of patients respond to this treatment, partially because of the “immune cold” condition of the tumor immune microenvironment. Pyroptosis is a type of gasdermin-mediated programmed cell death that often leads to inflammation and immune responses. Many studies on the mechanism and function of pyroptosis have led to increasing recognition of the role of pyroptosis in malignant progression and immune therapy. Pyroptosis has the potential to alter the tumor immune microenvironment by releasing tumor-associated antigens, damage-associated molecular patterns, and proinflammatory cytokines, thus leading to intratumoral inflammatory responses, stimulation of tumor-specific cytotoxic T cell infiltration, conversion of “cold” to “hot” tumors, and ultimately improving the efficacy of ICB therapy. Some cancer treatments have been shown to restore anticancer immunosurveillance through the induction of pyroptosis. Therapy promoting pyroptosis and ICB therapy may have synergistic effects in cancer treatment. This review summarizes the mechanisms and roles of pyroptosis in the tumor microenvironment and combination treatment strategies. An improved understanding of the roles of pyroptosis in tumorigenesis, immune evasion, and treatment would aid in the development of therapeutic strategies for malignancies.

Prognostic significance of the expression levels of T-cell immunoglobulin mucin-3 and its ligand galectin-9 for relapse-free survival in triple-negative breast cancer.

T-cell immunoglobulin mucin-3 (TIM-3) expressed at the T-cell surface acts as an immune checkpoint when bound by its ligand galectin-9. Blockade of immunosuppression by the TIM3/galectin-9 signalling pathway may offer novel therapeutic approaches for cancer immunotherapy. Consistent with this, TIM-3 expression is associated with poorer prognosis in several different types of cancer, possibly as a result of suppression of anticancer immunosurveillance. A number of studies have now documented some effectiveness of immune checkpoint blockade even in triple-negative breast cancer (TNBC), which is highly aggressive. However, clinical responses are relatively weak, suggesting that several different pathways may be involved. In this context, the role of the TIM-3/galectin-9 checkpoint in TNBC is not clear. The present study aimed to determine the clinicopathological significance of TIM-3 and galectin-9 expression in this cancer. To this end, 62 patients with TNBC undergoing surgery at Kansai Medical University Hospital (Hirakata, Japan), but not given neoadjuvant chemotherapy, were examined. Tissue microarrays were employed for immunohistochemistry to analyse associations of TIM-3 and galectin-9 expression and their impact on relapse-free survival relative to other poor prognostic risk factors. Galectin-9 expression was detected in 49 of 62 patient samples (79%), and TIM-3 in 30 of them (48.4%). Tumour cell galectin-9 expression was associated with a more favourable prognosis (P=0.027) as was TIM-3 expression on tumour-infiltrating lymphocytes (P=0.007). Multivariate analysis indicated that galectin-9- and TIM-3-double-positivity was significantly associated with a more favourable prognosis compared with galectin-9 and/or TIM-3 negativity (P=0.044). Thus, the TIM-3/galectin-9 signalling pathway may impact anticancer immune reactions in the tumour microenvironment of patients with TNBC. Further investigation will be necessary to determine the molecular mechanisms underlying these relationships.

PD-1 and PD-L1 expression predict regression and prognosis following neoadjuvant radiochemotherapy of oesophageal adenocarcinoma

Background and purposePD-1 and PD-L1 are involved in anticancer immunosurveillance, and their expression may be predictive for therapeutic effectiveness of specific antibodies. Their influence on response to neoadjuvant radiochemotherapy (RCT) and prognosis in patients with oesophageal adenocarcinoma (OAC) remains to be defined. Materials and methodsBetween 10/2004 and 06/2018, complete pre-RCT biopsy-specimens were available from 76 patients with locally advanced, non-metastatic OAC scheduled for trimodality therapy. We evaluated intra- and peritumoural expression of CD8, PD-1 and PD-L1 in pre-treatment specimens to determine their influence on tumour regression grade and survival. PD-1 and PD-L1 expression were considered positive (+) if ≥1% of all cells were stained positive, otherwise negative (-); densities of CD8+ cells were categorized as being high (Hi) or low (Lo) according to the median. ResultsA negative PD-L1 expression in peritumoural cells predicted a poor tumour regression (RD 0.24 [95% CI 0.03–0.44], p = 0.023). A positive PD-1 expression in intra- as well as peritumoural cells was identified as an unfavourable prognostic factor (HR 0.52 [95% CI 0.29–0.93], p = 0.028; HR 0.50 [0.25–0.99], p = 0.047, respectively). With respect to CD8+ infiltration, positive PD-1 and PD-L1 expressions attenuated its favourable prognostic effect in intratumoural area (LoCD8/PD1 + vs. HiCD8/PD1-: HR 0.25 [0.09–0.69], p = 0.007; LoCD8/PDL1+ vs. HiCD8/PDL1-: HR 0.32 [0.12–0.89], p = 0.028) and were associated with negative outcome when seen in peritumoural area (HiCD8/PD1+ vs. LoCD8/PD1-: HR 0.29 [0.11–0.74], p = 0.010); HiCD8/PDL1+ vs. LoCD8/PDL1-: HR 0.33 [0.12–0.90], p = 0.031). ConclusionsPD-1 and PD-L1 expression were identified to be of predictive and prognostic value in patients with OAC, particularly when considering CD8+ infiltration. Further validation by a large size dataset is required.

Cross-reactivity between microbial and tumor antigens.

The composition of the gut microbiota has a major impact on anticancer immunosurveillance. This effect is in part determined by systemic effects of bacterial or fungal metabolites, as well as by microbial ligands of pattern recognition receptors that modulate adjuvant signals and hence determine the general immune tonus. In addition, microbial antigens can elicit specific T lymphocyte responses that are cross-reactive with respect to tumor-associated antigens, hence inducing specific antitumor immune responses. Here, we discuss current evidence in favor of such cross-reactive anticancer/antimicrobial T cell response and delineate a methodology to demonstrate their actual importance for the immune control of malignant cells.

Fasting and cancer responses to therapy.

The therapeutic outcome of multiple anticancer regimens relies upon a fine balance between tumor intrinsic and host-related factors. In this context, qualitative changes in dietary composition as well as alterations in total calorie supply influence essential aspects of cancer biology, spanning from tumor initiation to metastatic spreading. On the one hand, circumstances of nutritional imbalance or excessive calorie intake promote oncogenesis, accelerate tumor progression, and hamper the efficacy of anticancer treatments. On the other hand, approaches based on bulk (e.g., fasting, fasting mimicking diets) or selective (e.g., amino acids) shortage of nutrients are currently in the spotlight for their ability to potentiate the effect of anticancer drugs. While the chemosensitizing effect of fasting has long been attributed to the overdemanding metabolic requirements of neoplastic cells, recent findings suggest that caloric restriction improves the efficacy of chemotherapy and immunotherapy by boosting anticancer immunosurveillance. Here, we provide a critical overview of current preclinical and clinical studies that address the impact of nutritional interventions on the response to cancer therapy, laying particular emphasis on fasting-related interventions.

Autophagy-inducing nutritional interventions in experimental and clinical oncology.

Numerous pro-autophagic dietary interventions are being investigated for their potential cancer-preventive or therapeutic effects. This applies to different fasting regimens, methionine restriction and ketogenic diets. In addition, the supplementation of specific micronutrients such as nicotinamide (vitamin B3) or spermidine induces autophagy. In humans, leanness, plant-based diets (that may lead to partial methionine restriction) and high dietary uptake of spermidine are associated with a low incidence of cancers. Moreover, clinical trials have demonstrated the capacity of nicotinamide to prevent non-melanoma skin carcinogenesis. Multiple interventional trials are evaluating the capacity of autophagy-inducing regimens to improve the outcome of chemotherapy and immunotherapy. Here, we discuss the mechanistic underpinnings of autophagy induction by nutritional interventions, as well as the mechanisms through which autophagy induction in malignant or immune cells improves anticancer immunosurveillance.

Concomitant High Apoptosis Inhibitor of Macrophage (AIM) and Low Prostate-Specific Antigen (PSA) Indicates Activated T Cell-Mediated Anticancer Immunity, Enhance Sensitivity to Pembrolizumab, and Elicit Good Prognosis in Prostate Cancer.

Background: Despite its widespread use, the use of prostate-specific antigen (PSA) alone as a screening biomarker for prostate cancer (PCa) leads often to unwarranted prostate biopsy, over-diagnosis, and consequently, over-treatment, because of its limited specificity. There are reports that the apoptosis inhibitor of macrophage (AIM), secreted mainly by macrophages and epithelial cells, is upregulated during inflammation and facilitates immune recognition of cancerous cells by blocking human regulator of complement activation. Objective: These controversies around the PSA utility necessitate a reexamination of its use as a screening tool. More so, despite the suggested implication of AIM in anticancer immunosurveillance, there is a dearth of information on its role in therapy response, disease progression, and clinical outcomes of patients with PCa. These inform the present study to probe the nature and role of AIM/PSA signaling in anticancer immunity and prognosis in PCa. Methods: A combination of bioinformatics-aided statistical analyses, gene function annotation, and immune infiltrate analyses, coupled with tissue staining, and function assays, namely migration, invasion, and clonogenicity assays, we employed. Results: We demonstrated that AIM and PSA expression levels are inversely correlated in PCa clinical samples and cell lines, with AIMlowPSAhigh defining PCa, compared to AIMhighPSAlow in normal samples. Concomitant aberrant PSA and significantly suppressed AIM expression levels positively correlated with high-grade disease and characterized by advanced stage prostate cancer, regardless of mutation status. We found that a high PSA/AIM ratio is associated with disease recurrence in patients with prostate cancer but is equivocal for overall survival. In addition, PSA-associated AIM suppression is implicated in the enhanced ‘metastability’ of PCa and a high AIM/PSA ratio is associated with strong castration-induced regression. CRISPR-mediated AIM knockout was associated with higher PSA expression while ectopic expression of AIM significantly attenuated the migration and invasive capability of PC3 and DU145 cells. Interestingly, compared to normal samples, we observed that AIM, biomarkers of T-cell activation and M1 phenotype markers are co-suppressed in PCa samples. Conclusion: Herein, we demonstrate that AIM/CD5L binds to PSA and that a high PSA/AIM ratio defines advanced stage PCa (regardless of mutation status), is implicated in enhanced metastability, and associated with disease recurrence, while a high AIM/PSA ratio is associated with strong castration-induced regression. More so, the ectopic expression of AIM significantly enhances the anticancer effect of Pembrolizumab and elicits an increased CD8+ T-cell count in AIMhiPSAloPDL1+ PCa cases that are respondent to Pembrolizumab treatment.

Abstract 1805: ABTL0812, a Phase 2 clinical stage pro-autophagy anticancer drug exhibits immunomodulatory effects that modify tumor microenvironment in pancreatic cancer models

Abstract ABTL0812 induces cytotoxic autophagy in cancer cells through the combination of ER stress induction and Akt/mTOR blockade. ABTL0812 induces ER stress mediated activation of JNK-Jun pathway and inhibition of the STAT3-IL10 axis in cancer and immune cells in vitro and induces ER stress markers TRIB3 and CHOP in white blood cells of patients with no toxic effects and showing clinical efficacy in Phase 2 trial in combination with chemotherapy vs chemotherapy alone (historical data). In primary and immortalized monocytes-derived macrophages in vitro, ABTL0812 promoted M1 phenotypes potentiating IL-1β and TNFα expression and suppressed M2 phenotypes by decreasing IL-10 expression, as detected by RT-qPCR. Additionally, ABTL0812 inhibited the release of immunosuppressive chemokines (CXCL5, CCL5, CCL8) detected by protein array. In human primary T cells cultured in vitro, ABTL0812 decreased PD1 surface expression in non-activated and activated CD4 and CD8 cells detected by flow cytometry. In pancreatic cancer cells in vitro, ABTL0812 inhibited the release of immunosuppressive chemokines (CCL5, CXCL6, CXCL16), as detected by a protein array. ABTL0812 induced Immunogenic Cell Death (ICD) as indicated by a dose-dependent increase of ICD markers: extracellular Hmgb1 and ATP, surface calreticulin, and caspases 3 and 8 activation, as detected by ELISA, luciferase assay, flow cytometry and fluorescence based substrate assays, respectively. Cultured media from ABTL0812 treated pancreatic cancer cells transferred to differentiated macrophages potentiated the activation of immortalized THP1 macrophages (increased metabolic activity) and promoted M1 polarization potentiating IL-1β and TNFα expression measured by RT-qPCR. In a syngeneic murine model using MT5 murine pancreatic cancer cells (K-Ras and p53 mutated), ABTL0812 showed significant tumor volume reduction compared to vehicle treatment, and similar efficacy to anti-PD1 treatment. Flow cytometry analysis of tumors revealed that ABTL0812 increased intratumor myeloid and Natural Killer T-cells more efficiently than anti-PD1. Importantly, ABTL0812 also increased T helpers Th1/Th2 ratio in spleen. ABTL0812 shows immunomodulatory effects in vitro and in vivo in pancreatic cancer models through the inhibition of the secretion of immunosuppressive chemokines and the induction of ICD in cancer cells, while potentiates M1 phenotypes in macrophages and inhibits PD1 expression in T cells, ultimately promoting increased myeloid and NK cells within tumors and increased Th1/Th2 ratio. Overall, these multiple actions could potentially help to transform “cold” non-immunogenic tumors into “hot” immunogenic tumors and contribute to elicit anticancer immunosurveillance. These novel findings support further investigation of ABTL0812 in combination with immunotherapy to treat cancer Citation Format: Guillermo Yoldi, Pau Munoz-Guardiola, Elisabet Megias, Hector Perez-Montoyo, Marc Yeste-Velasco, Jose Alfon, Carles Domenech, Jose Miguel Lizcano. ABTL0812, a Phase 2 clinical stage pro-autophagy anticancer drug exhibits immunomodulatory effects that modify tumor microenvironment in pancreatic cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1805.