Rapamycin Impairs Antitumor CD8+ T-cell Responses and Vaccine-Induced Tumor Eradication

Regulation of CD19 CAR-T cell activation based on an engineered downstream transcription factor

CAR-T cells present a highly effective therapeutic option for several malignant diseases, based on their ability to recognize the selected tumor surface marker in an MHC-independent manner. This triggers cell activation and cytokine production, resulting in the killing of the cancerous cell presenting markers recognized by the chimeric antigen receptor. CAR-T cells are highly potent serial killers that may cause serious side effects, so their activity needs to be carefully controlled. Here we designed a system to control the proliferation and activation state of CARs based on downstream NFAT transcription factors, whose activity can be regulated via chemically induced heterodimerization systems. Chemical regulators were used to either transiently trigger engineered T cell proliferation or suppress CAR-mediated activation when desired or to enhance activation of CAR-T cells upon engagement of cancer cells, shown also in vivo. Additionally, an efficient sensor to monitor activated CD19 CAR-T cells in vivo was introduced. This implementation in CAR-T cell regulation offers an efficient way for on-demand external control of CAR-T cell activity to improve their safety.

Nanoscale metal-organic framework delivers rapamycin to induce tissue immunogenic cell death and potentiates cancer immunotherapy

Rapamycin has great potential in the antitumor application, but its therapeutic effect is seriously affected by poor water solubility, targeting ability, and low bioavailability. Here, we constructed a novel composite nanomaterial with PCN-224 as a drug carrier and loaded rapamycin, named R@BP@HA. The nanoplate not only improves targeting, but also synergizes rapamycin with PCN-224 to effectively promote tumor cell apoptosis, which subsequently causes immunogenic cell death (ICD), and shows strong therapeutic effect in 4T1 breast cancer model. The treatment effect depends on three main points:(i)Proapoptotic effect of rapamycin on tumor cells;(ii)ROS production by PCN-224-mediated photodynamic therapy;(iii)ICD induced DC maturation, increased immune response and promoted T cell proliferation and differentiation. This nanoplate offers potential antitumor efficacy in combination with chemotherapy, photodynamic therapy, and immunotherapy.

High-throughput in situ perturbation of metabolite levels in the tumor micro-environment reveals favorable metabolic condition for increased fitness of infiltrated T-cells

Tumor-infiltrating immune cells experience significant metabolic reprogramming in the tumor microenvironment (TME), and they share similar metabolic pathways and nutrient needs with malignant cells. This positions these cell types in direct nutrient competition in the TME. We currently lack a complete understanding of the similarities, differences, and functional consequences of the metabolic pathways utilized by activated immune cells from different lineages versus neoplastic cells. This study applies a novel in situ approach using implantable microdevices to expose the tumor to 27 controlled and localized metabolic perturbations in order to perform a systematic investigation into the metabolic regulation of the cellular fitness and persistence between immune and tumor cells directly within the native TME. Our findings identify the most potent metabolites, notably glutamine and arginine, that induce a favorable metabolic immune response in a mammary carcinoma model, and reveal novel insights on less characterized pathways, such as cysteine and glutathione. We then examine clinical samples from cancer patients to confirm the elevation of these pathways in tumor regions that are enriched in activated T cells. Overall, this work provides the first instance of a highly multiplexed in situ competition assay between malignant and immune cells within tumors using a range of localized microdose metabolic perturbations. The approach and findings may be used to potentiate the effects of T cell stimulating immunotherapies on a tumor-specific or personalized basis through targeted enrichment or depletion of specific metabolites.

Sirolimus-exuding core-shell nanofibers as an implantable carrier for breast cancer therapy: preparation, characterization, in vitro cell studies, and in vivo anti-tumor activity

OBJECTIVE

Breast cancer accounts for significant mortality worldwide. Here, we develop a localized, sustained-release delivery system for breast cancer therapy.

METHODS

Sirolimus (SIR) core-shell nanofibers (NFs) are fabricated by coaxial electrospinning with poly(ε-caprolactone) (PCL) for the core and chitosan and PCL for the shell. The NFs were characterized by SEM, AFM, TEM, XRD, FTIR, water uptake, water contact angle, mechanical properties, drug content, and in vitro release. In vitro and in vivo anticancer effects were investigated.

RESULTS

A sustained release behavior is observed during 480 h that is more extended compared to monoaxial NFs. In vitro cytotoxicity and Annexin V/propidium iodide assays indicate that SIR-loaded coaxial NFs are effective in inhibiting proliferation of 4T1 and MCF-7 cells. Implantation of SIR NFs in 4T1 breast tumor-bearing mice inhibits tumor growth significantly compared to free drug. Histopathological examination shows that suppression of tumor growth by SIR NFs is associated with apoptotic cell death. Furthermore, anti-cancer effects are also confirmed by decreased expression levels of Ki-67, MMP-2, and MMP-9. Histological observation of organs, serological analyses, and the lack of body weight changes indicate in vivo safety of SIR NFs.

CONCLUSIONS

Altogether, we show here that incorporation of SIR into core-shell NFs could act as an effective drug release depot and induce a sustained antitumor response.

Targeting mTOR as a Cancer Therapy: Recent Advances in Natural Bioactive Compounds and Immunotherapy

The mammalian target of rapamycin (mTOR) is a highly conserved serine/threonine-protein kinase, which regulates many biological processes related to metabolism, cancer, immune function, and aging. It is an essential protein kinase that belongs to the phosphoinositide-3-kinase (PI3K) family and has two known signaling complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Even though mTOR signaling plays a critical role in promoting mitochondria-related protein synthesis, suppressing the catabolic process of autophagy, contributing to lipid metabolism, engaging in ribosome formation, and acting as a critical regulator of mRNA translation, it remains one of the significant signaling systems involved in the tumor process, particularly in apoptosis, cell cycle, and cancer cell proliferation. Therefore, the mTOR signaling system could be suggested as a cancer biomarker, and its targeting is important in anti-tumor therapy research. Indeed, its dysregulation is involved in different types of cancers such as colon, neck, cervical, head, lung, breast, reproductive, and bone cancers, as well as nasopharyngeal carcinoma. Moreover, recent investigations showed that targeting mTOR could be considered as cancer therapy. Accordingly, this review presents an overview of recent developments associated with the mTOR signaling pathway and its molecular involvement in various human cancer types. It also summarizes the research progress of different mTOR inhibitors, including natural and synthetised compounds and their main mechanisms, as well as the rational combinations with immunotherapies.

A novel strategy to fuel cancer immunotherapy: targeting glucose metabolism to remodel the tumor microenvironment

The promising results of immunotherapy in tumors have changed the current treatment modality for cancer. However, the remarkable responses are limited to a minority of patients, which is due to immune suppression in the tumor microenvironment (TME). These include the pre-exists of suppressive immune cells, physical barriers to immune infiltration, antigen and antigen presentation deficiency, and expression of inhibitory immune checkpoint molecules. Recently, increasing evidence reveal that tumor metabolism, especially abnormal glucose metabolism of tumors, plays an essential role in tumor immune escape and is a potential target to combine with immunotherapy. By glucose uptake, tumor cells alter their metabolism to facilitate unregulated cellular proliferation and survival and regulate the expression of inhibitory immune checkpoint molecules. Meanwhile, glucose metabolism also regulates the activation, differentiation, and functions of immunocytes. In addition, tumor mainly utilizes glycolysis for energy generation and cellular proliferation, which cause the TME to deplete nutrients for infiltrating immune cells such as T cells and produce immunosuppressive metabolites. Thus, therapeutics that target glucose metabolism, such as inhibiting glycolytic activity, alleviating hypoxia, and targeting lactate, have shown promise as combination therapies for different types of cancer. In this review, we summarized the functions of glucose metabolism in the tumor cells, immune cells, and tumor microenvironment, as well as strategies to target glucose metabolism in combination with immune checkpoint blockade for tumor therapy.

Importance of T, NK, CAR T and CAR NK Cell Metabolic Fitness for Effective Anti-Cancer Therapy: A Continuous Learning Process Allowing the Optimization of T, NK and CAR-Based Anti-Cancer Therapies

Simple Summary

Cancer treatments are evolving at a very rapid pace. Some of the most novel anti-cancer medicines under development rely on the modification of immune cells in order to transform them into potent tumor-killing cells. However, the tumor microenvironment (TME) is competing for nutrients with these harnessed immune cells and therefore paralyzes their metabolic effective and active anti-cancer activities. Here we describe strategies to overcome these hurdles imposed on immune cell activity, which lead to therapeutic approaches to enhance metabolic fitness of the patient’s immune system with the objective to improve their anti-cancer capacity.

Abstract

Chimeric antigen receptor (CAR) T and CAR NK cell therapies opened new avenues for cancer treatment. Although original successes of CAR T and CAR NK cells for the treatment of hematological malignancies were extraordinary, several obstacles have since been revealed, in particular their use for the treatment of solid cancers. The tumor microenvironment (TME) is competing for nutrients with T and NK cells and their CAR-expressing counterparts, paralyzing their metabolic effective and active states. Consequently, this can lead to alterations in their anti-tumoral capacity and persistence in vivo. High glucose uptake and the depletion of key amino acids by the TME can deprive T and NK cells of energy and building blocks, which turns them into a state of anergy, where they are unable to exert cytotoxic activity against cancer cells. This is especially true in the context of an immune-suppressive TME. In order to re-invigorate the T, NK, CAR T and CAR NK cell-mediated antitumor response, the field is now attempting to understand how metabolic pathways might change T and NK responses and functions, as well as those from their CAR-expressing partners. This revealed ways to metabolically rewire these cells by using metabolic enhancers or optimizing pre-infusion in vitro cultures of these cells. Importantly, next-generation CAR T and CAR NK products might include in the future the necessary metabolic requirements by improving their design, manufacturing process and other parameters. This will allow the overcoming of current limitations due to their interaction with the suppressive TME. In a clinical setting, this might improve their anti-cancer effector activity in synergy with immunotherapies. In this review, we discuss how the tumor cells and TME interfere with T and NK cell metabolic requirements. This may potentially lead to therapeutic approaches that enhance the metabolic fitness of CAR T and CAR NK cells, with the objective to improve their anti-cancer capacity.

Directing T-Cell Immune Responses for Cancer Vaccination and Immunotherapy

Cancer vaccination and immunotherapy revolutionised the treatment of cancer, a result of decades of research into the immune system in health and disease. However, despite recent breakthroughs in treating otherwise terminal cancer, only a minority of patients respond to cancer immunotherapy and some cancers are largely refractive to immunotherapy treatment. This is due to numerous issues intrinsic to the tumour, its microenvironment, or the immune system. CD4+ and CD8+ αβ T-cells emerged as the primary effector cells of the anti-tumour immune response but their function in cancer patients is often compromised. This review details the mechanisms by which T-cell responses are hindered in the setting of cancer and refractive to immunotherapy, and details many of the approaches under investigation to direct T-cell function and improve the efficacy of cancer vaccination and immunotherapy.

The Role of mRNA Translational Control in Tumor Immune Escape and Immunotherapy Resistance

Tremendous advances have been made in cancer immunotherapy over the last decade. Among the different steps of gene expression, translation of mRNA is emerging as an essential player in both cancer and immunity. Changes in mRNA translation are both rapid and adaptive, and translational reprogramming is known to be necessary for sustaining cancer cell proliferation. However, the role of mRNA translation in shaping an immune microenvironment permissive to tumors has not been extensively studied. Recent studies on immunotherapy approaches have indicated critical roles of mRNA translation in regulating the expression of immune checkpoint proteins, tuning the secretion of inflammation-associated factors, modulating the differentiation of immune cells in the tumor microenvironment, and promoting cancer resistance to immunotherapies. Careful consideration of the role of mRNA translation in the tumor-immune ecosystem could suggest more effective therapeutic strategies and may eventually change the current paradigm of cancer immunotherapy. In this review, we discuss recent advances in understanding the relationship between mRNA translation and tumor-associated immunity, the potential mechanisms of immunotherapy resistance in cancers linked to translational reprogramming, and therapeutic perspectives and potential challenges of modulating translational regulation in cancer immunotherapy.

Compromised DNA Repair Promotes the Accumulation of Regulatory T Cells With an Aging-Related Phenotype and Responsiveness

Decline of immune function during aging has in part been ascribed to the accumulation of regulatory T cells (Tregs) and decreased T-cell responses with age. Aside from changes to T cells that occur over a lifetime, the impact of intracellular aging processes such as compromised DNA repair on T cells remains incompletely defined. Here we aimed to define the impact of compromised DNA repair on T-cell phenotype and responsiveness by studying T cells from mice with a deficiency in their DNA excision-repair gene Ercc1. These Ercc1 mutant (Ercc1^−/Δ7) mice show accumulation of nuclear DNA damage resulting in accelerated aging. Similarly to wild-type aged mice, Ercc1^−/Δ7 mice accumulated Tregs with reduced CD25 and increased PD-1 expression among their naive T cells. Ercc1-deficiency limited the capacity of Tregs, helper T cells, and cytotoxic T cells to proliferate and upregulate CD25 in response to T-cell receptor- and IL-2-mediated stimulation. The recent demonstration that the mammalian target of rapamycin (mTOR) may impair DNA repair lead us to hypothesize that changes induced in the T-cell population by compromised DNA repair may be slowed down or reversed by blocking mTOR with rapamycin. In vivo dietary treatment of Ercc1^−/Δ7 mice with rapamycin did not reduce Treg levels, but highly increased the proportion of CD25⁺ and PD-1⁺ memory Tregs instead. Our study elucidates that compromised DNA repair promotes the accumulation of Tregs with an aging-related phenotype and causes reduced T-cell responsiveness, which may be independent of mTOR activation.

A Local and Low-Dose Chemotherapy/Autophagy-Enhancing Regimen Treatment Markedly Inhibited the Growth of Established Solid Tumors Through a Systemic Antitumor Immune Response

Chemotherapy is one of the main options for the treatment of a variety of malignant tumors. However, the severe side effects resulting from the killing of normal proliferating cells limit the application of cancer-targeting chemotherapeutic drugs. To improve the efficacy of classic systemic chemotherapy, the local delivery of high-dose chemotherapeutic drugs was developed as a method to enhance local drug concentrations and minimize systemic toxicity. Studies have demonstrated that chemotherapy is often accompanied by cancer-associated immunogenic cell death (ICD) and that autophagy is involved in the induction of ICD. To improve the efficacy of local cancer chemotherapy, we hypothesized that the local delivery of chemotherapeutic plus autophagy-enhancing agents would enhance the promotive effects of ICD on the antitumor immune response. Here, we report that a low-dose chemotherapy/autophagy enhancing regimen (CAER) not only resulted in the increased death of B16F10 and 4T1 tumor cells, but also induced higher levels of autophagy in vitro. Importantly, the local delivery of the CARE drugs significantly inhibited tumor growth in B16F10 and 4T1 tumor-bearing mice. Systemic antitumor T-cell immunity was observed in vivo, including neoantigen-specific T-cell responses. Furthermore, bioinformatic analysis of human breast cancer and melanoma tissues showed that autophagy-associated gene expression was upregulated in tumor samples. Increased autophagy and immune cell infiltration in tumor tissues were positively correlated with good prognosis of tumor patients. This work highlights a new approach to improve the effects of local chemotherapy and enhance systemic antitumor immunity.

Combining mTOR Inhibitors and T Cell-Based Immunotherapies in Cancer Treatment

mTOR regulates several processes that control tumor development, including cancer cell growth, angiogenesis and the immune response to tumor. Accordingly, mTOR inhibitors have been thoroughly explored in cancer therapy but have failed to provide long-lasting anticancer benefits. Several resistance mechanisms that counteract the antitumor effect of mTOR inhibitors have been identified and have highlighted the need to use mTOR inhibitors in combination therapies. In this context, emerging evidence has demonstrated that mTOR inhibitors, despite their immunosuppressive properties, provide anticancer benefits to immunotherapies. In fact, mTOR inhibitors also display immunostimulatory effects, in particular by promoting memory CD8+ T cell generation. Hence, mTOR inhibitors represent a therapeutic opportunity to promote antitumor CD8 responses and to boost the efficacy of different modalities of cancer immunotherapy. In this context, strategies to reduce the immunosuppressive activity of mTOR inhibitors and therefore to shift the immune response toward antitumor immunity will be useful. In this review, we present the different classes of mTOR inhibitors and discuss their effect on immune cells by focusing mainly on CD8+ T cells. We further provide an overview of the different preclinical studies that investigated the anticancer effects of mTOR inhibitors combined to immunotherapies.

Bioengineering of Bordetella pertussis Adenylate Cyclase Toxin for Vaccine Development and Other Biotechnological Purposes

The adenylate cyclase toxin, CyaA, is one of the key virulent factors produced by Bordetella pertussis, the causative agent of whooping cough. This toxin primarily targets innate immunity to facilitate bacterial colonization of the respiratory tract. CyaA exhibits several remarkable characteristics that have been exploited for various applications in vaccinology and other biotechnological purposes. CyaA has been engineered as a potent vaccine vehicle to deliver antigens into antigen-presenting cells, while the adenylate cyclase catalytic domain has been used to design a robust genetic assay for monitoring protein-protein interactions in bacteria. These two biotechnological applications are briefly summarized in this chapter.

The immunomodulatory effects of endocrine therapy in breast cancer

Endocrine therapies with SERMs (selective estrogen receptor modulators) or SERDs (selective estrogen receptor downregulators) are standard therapies for patients with estrogen receptor (ER)-positive breast cancer. Multiple small molecule inhibitors targeting the PI3K-AKT-mTOR pathway or CDK4/6 have been developed to be used in combination with anti-estrogen drugs to overcome endocrine resistance. In addition to their direct antitumor effects, accumulating evidence has revealed the tumor immune microenvironment (TIM)-modulating effects of these therapeutic strategies, which have not been properly acknowledged previously. The immune microenvironment of breast tumors plays a crucial role in tumor development, metastasis and treatment response to endocrine therapy and immunotherapy. Therefore, in our current work, we comprehensively review the immunomodulatory effect of endocrine therapy and discuss its potential applications in combination with immune checkpoint inhibitors in breast cancer treatment.

Antigen-Specific In Vivo Killing Assay

The in vivo killing assay allows the quantification of the antigen-specific killing capacity of Cytotoxic CD8⁺ T Lymphocytes (CTLs) in mice. CTLs are indeed known for the lysis of cells expressing foreign or modified antigen peptides on their MHC class I molecules. Here we describe the detailed protocol used for the in vivo specific lysis of cells expressing the H-2 K^b immunodominant CD8⁺ T-cell epitope of the OVA protein: an 8 amino acid peptide corresponding to the 257-264 region of OVA (SIINFEKL).

The effects of age and systemic metabolism on anti-tumor T cell responses

Average age and obesity prevalence are increasing globally. Both aging and obesity are characterized by profound systemic metabolic and immunologic changes and are cancer risk factors. The mechanisms linking age and body weight to cancer are incompletely understood, but recent studies have provided evidence that the anti-tumor immune response is reduced in both conditions, while responsiveness to immune checkpoint blockade, a form of cancer immunotherapy, is paradoxically intact. Dietary restriction, which promotes health and lifespan, may enhance cancer immunity. These findings illustrate that the systemic context can impact anti-tumor immunity and immunotherapy responsiveness. Here, we review the current knowledge of how age and systemic metabolic state affect the anti-tumor immune response, with an emphasis on CD8+ T cells, which are key players in anti-tumor immunity. A better understanding of the underlying mechanisms may lead to novel therapies enhancing anti-tumor immunity in the context of aging or metabolic dysfunction.

Low-Dose Interleukin-2 Combined With Rapamycin Led to an Expansion of CD4+CD25+FOXP3+ Regulatory T Cells and Prolonged Human Islet Allograft Survival in Humanized Mice

Islet transplantation is an emerging therapy for type 1 diabetes and hypoglycemic unawareness. However, a key challenge for islet transplantation is cellular rejection and the requirement for long-term immunosuppression. In this study, we established a diabetic humanized NOD-scidIL2Rγ^null (NSG) mouse model of T-cell-mediated human islet allograft rejection and developed a therapeutic regimen of low-dose recombinant human interleukin-2 (IL-2) combined with low-dose rapamycin to prolong graft survival. NSG mice that had received renal subcapsular human islet allografts and were transfused with 1 × 10⁷ of human spleen mononuclear cells reconstituted human CD45⁺ cells that were predominantly CD3⁺ T cells and rejected their grafts with a median survival time of 27 days. IL-2 alone (0.3 × 10⁶ IU/m² or 1 × 10⁶ IU/m²) or rapamycin alone (0.5-1 mg/kg) for 3 weeks did not prolong survival. However, the combination of rapamycin with IL-2 for 3 weeks significantly prolonged human islet allograft survival. Graft survival was associated with expansion of CD4⁺CD25⁺FOXP3⁺ regulatory T cells (Tregs) and enhanced transforming growth factor-β production by CD4⁺ T cells. CD8⁺ T cells showed reduced interferon-γ production and reduced expression of perforin-1. The combination of IL-2 and rapamycin has the potential to inhibit human islet allograft rejection by expanding CD4⁺FOXP3⁺ Tregs in vivo and suppressing effector cell function and could be the basis of effective tolerance-based regimens.

Effective treatment of refractory acquired pure red blood cell aplasia with eltrombopag and sirolimus: a case report

Acquired pure red cell aplasia (aPRCA) is a kind of anemia characterized by severe reticulocytopenia and reduced bone marrow erythroblastic cells. For patients who are refractory to the first-line therapy (cyclosporin A with/without glucocorticoids), second-line therapy is considered less effective. We report on a patient with primary aPRCA who was refractory to cyclosporin A, glucocorticoids, and several second-line regimens. The patient was treated with sirolimus for 10 months with no improvement in hemoglobin but complete response was achieved after adding eltrombopag at a dosage of 25 mg/day. Eltrombopag was well tolerated with no evidence of clonal evolution at the end of follow up. This case provided a new attempt at treating patients with refractory/relapse aPRCA with eltrombopag, probably in combination with sirolimus.

Rapamycin and dexamethasone during pregnancy prevent tuberous sclerosis complex-associated cystic kidney disease

Chronic kidney disease is the main cause of mortality in patients with tuberous sclerosis complex (TSC) disease. The mechanisms underlying TSC cystic kidney disease remain unclear, with no available interventions to prevent cyst formation. Using targeted deletion of TSC1 in nephron progenitor cells, we showed that cysts in TSC1-null embryonic kidneys originate from injured proximal tubular cells with high mTOR complex 1 activity. Injection of rapamycin to pregnant mice inhibited the mTOR pathway and tubular cell proliferation in kidneys of TSC1-null offspring. Rapamycin also prevented renal cystogenesis and prolonged the life span of TSC newborns. Gene expression analysis of proximal tubule cells identified sets of genes and pathways that were modified secondary to TSC1 deletion and rescued by rapamycin administration during nephrogenesis. Inflammation with mononuclear infiltration was observed in the cystic areas of TSC1-null kidneys. Dexamethasone administration during pregnancy decreased cyst formation by not only inhibiting the inflammatory response, but also interfering with the mTORC1 pathway. These results reveal mechanisms of cystogenesis in TSC disease and suggest interventions before birth to ameliorate cystic disease in offspring.

Targeting Metabolism to Improve the Tumor Microenvironment for Cancer Immunotherapy

The growing field of immune metabolism has revealed promising indications for metabolic targets to modulate anti-cancer immunity. Combination therapies involving metabolic inhibitors with immune checkpoint blockade (ICB), chemotherapy, radiation, and/or diet now offer new approaches for cancer therapy. However, it remains uncertain how to best utilize these strategies in the context of the complex tumor microenvironment (TME). Oncogene-driven changes in tumor cell metabolism can impact the TME to limit immune responses and present barriers to cancer therapy. These changes also reveal opportunities to reshape the TME by targeting metabolic pathways to favor immunity. Here we explore current strategies that shift immune cell metabolism to pro-inflammatory states in the TME and highlight a need to better replicate physiologic conditions to select targets, clarify mechanisms, and optimize metabolic inhibitors. Unifying our understanding of these pathways and interactions within the heterogenous TME will be instrumental to advance this promising field and enhance immunotherapy.

Mechanistic target of rapamycin in the tumor microenvironment and its potential as a therapeutic target for pancreatic cancer

Pancreatic cancer(PC) is a devastating disease with a poor prognosis; however, few treatment options are available and the search continues for feasible molecular therapeutic targets, both in the tumor itself and in the tumor microenvironment. The mechanistic target of rapamycin (mTOR) signaling pathway has emerged as an attractive target due to its regulatory role in multiple cellular processes, including metabolism, proliferation, survival, and differentiation, under physiological and pathological conditions. Although mTOR-regulated events in tumor cells and the tumor microenvironment are known to restrict the development and growth of tumor cells, monotherapy with mTOR inhibitors has shown limited efficacy against PC to date, suggesting the need for alternative approaches. In this review, we describe the mechanisms by which mTOR modulates the PC microenvironment and suggest ways its function in immune cells might be exploited for the treatment of PC. We also discuss preclinical and clinical studies with mTOR inhibitors in combination with other therapeutic strategies, most notably immunotherapy. Finally, we highlight the promise that mTOR combinatorial therapy may hold for the treatment of PC in the near future.

Hypoxia-Driven Immune Escape in the Tumor Microenvironment

The tumor microenvironment is a complex ecosystem comprised of many different cell types, abnormal vasculature and immunosuppressive cytokines. The irregular growth kinetics with which tumors grow leads to increased oxygen consumption and, in turn, hypoxic conditions. Hypoxia has been associated with poor clinical outcome, increased tumor heterogeneity, emergence of resistant clones and evasion of immune detection. Additionally, hypoxia-driven cell death pathways have traditionally been thought of as tolerogenic processes. However, as researchers working in the field of immunotherapy continue to investigate and unveil new types of immunogenic cell death (ICD), it has become clear that, in some instances, hypoxia may actually induce ICD within a tumor. In this review, we will discuss hypoxia-driven immune escape that drives poor prognostic outcomes, the ability of hypoxia to induce ICD and potential therapeutic targets amongst hypoxia pathways.

Response of metastatic mouse invasive lobular carcinoma to mTOR inhibition is partly mediated by the adaptive immune system

Effective treatment of invasive lobular carcinoma (ILC) of the breast is hampered by late detection, invasive growth, distant metastasis, and poor response to chemotherapy. Phosphoinositide 3-kinase (PI3K) signaling, one of the major druggable oncogenic signaling networks, is frequently activated in ILC. We investigated treatment response and resistance to AZD8055, an inhibitor of mammalian target of rapamycin (mTOR), in the K14-cre;Cdh1^Flox/Flox;Trp53^Flox/Flox (KEP) mouse model of metastatic ILC. Inhibition of mTOR signaling blocked the growth of primary KEP tumors as well as the progression of metastatic disease. However, primary tumors and distant metastases eventually acquired resistance after long-term AZD8055 treatment, despite continued effective suppression of mTOR signaling in cancer cells. Interestingly, therapeutic responses were associated with increased expression of genes related to antigen presentation. Consistent with this observation, increased numbers of tumor-infiltrating major histocompatibility complex class II-positive (MHCII+) immune cells were observed in treatment-responsive KEP tumors. Acquisition of treatment resistance was associated with loss of MHCII+ cells and reduced expression of genes related to the adaptive immune system. The therapeutic efficacy of mTOR inhibition was reduced in Rag1^−/- mice lacking mature T and B lymphocytes, compared to immunocompetent mice. Furthermore, therapy responsiveness could be partially rescued by transplanting AZD8055-resistant KEP tumors into treatment-naïve immunocompetent hosts. Collectively, these data indicate that the PI3K signaling pathway is an attractive therapeutic target in invasive lobular carcinoma, and that part of the therapeutic effect of mTOR inhibition is mediated by the adaptive immune system.

Immune-mediated anti-tumor effects of metformin; targeting metabolic reprogramming of T cells as a new possible mechanism for anti-cancer effects of metformin

Immunotherapy-based cancer treatment has revolutionized the era of cancer patients recuperation and it has brought a strong hope to treatment of some types of cancers. Metformin, a widely used antidiabetic drug, which has intensely been studied for its anticancer effects, is believed to have positive influences on immune responses against tumor cells. Metformin can affect metabolic pathways within cells mainly through activation of AMPK. Metabolic restriction of tumor microenvironment on effector immune cells is one of the important strategies favoring tumor cells to escape from immunogenic cell death. The metabolism of T cells has an axial role in shaping and supporting immune responses and may have an important role in anticancer immunity, suggesting that the functionality and durability of tumor-specific T cells need sufficient energy and nutrients. Energy biogenesis of tumor-specific cytotoxic T cells has become an interesting field of study and it is suggested that activation and maintenance of effector T cell responses in tumor microenvironment may occur by metabolic reprogramming of T cells. AMPK has been noticed as the main intracellular energy sensor and mitochondrial biogenesis key regulator which can control and regulate metabolic reprogramming in immune cells and increase antitumor immunity. Metabolic reprogramming of T cells to overcome metabolic restriction in tumor microenvironment, maiming effector T cell responses against tumor cells, has been noticed by several studies. Here we represent metformin, an AMPK activator, as a new candidate drug for metabolic reprogramming of tumor-specific T cells to increase the efficacy and accountability of cancer immunotherapy.

The Induction of a Permissive Environment to Promote T Cell Immune Evasion in Acute Myeloid Leukemia: The Metabolic Perspective

Acute myeloid leukemia (AML) is the acute leukemia with highest incidence amongst adults. Despite significant improvements in understanding the genomic landscape and the introduction of novel drugs, long-term outcome remains unsatisfactory. Recently, immunotherapeutic approaches have heralded a new era in cancer treatment. The success of allogeneic hematopoietic stem cell transplantation in AML highlights the disease's immunoresponsiveness. Several immunotherapeutic applications are currently under clinical evaluation and include immune checkpoint blockades, T cell-engaging antibodies, and genetically engineered T cells. However, immunoevasive mechanisms employed by AML blasts severely hamper our endeavors. A better understanding of the underlying mechanisms remains a prerequisite for improving treatment efficacy. One of the hallmarks of the cancer cells is metabolic reprogramming, introduced by Otto Warburg's seminal studies during the beginnings of the last century. Nowadays, it is well established that metabolic adaptation is not just an epiphenomenon during oncogenesis but rather a necessity for tumor development and progression. Furthermore, accumulating data suggest an important role of aberrant tumor cell metabolism for immune escape. AML blasts display a number of metabolic alterations that could be linked to immunoregulation, and these include competition over substrates, abundant release of bioactive metabolites, and an overall microenvironmental metabolic re-modeling that favors the induction or survival of immunoregulatory cell subsets such as regulatory T cells. In this review, we outline the immunoevasive character of the AML blasts' bioenergetics, set it into context with oncogenic mutations, and discuss potentially suitable countermeasures and their limitations.

Rapalog combined with CCR4 antagonist improves anticancer vaccines efficacy

mTOR pathway inhibitors such as rapalogs represent a promising tool to induce functional memory CD8 T cells. In our study, we investigated the combination of temsirolimus with anticancer vaccines. Using various designs of cancer vaccines (short and long peptides or the B subunit of Shiga toxin as an antigen delivery vector) and tumor models (melanoma, lung and colon cancer), we showed that the administration of temsirolimus efficiently decreased tumor growth and enhanced tumor-specific CD8 T-cell responses induced by vaccination. Furthermore, tumor-specific CD8 T cells induced by the bi-therapy (vaccine + temsirolimus) exhibit phenotypic characteristics of central memory (CD127⁺ CD62L⁺ ) CD8 T cells compared to vaccination alone. We demonstrated that regulatory CD4 T cells (T_regs ) expansion in vivo limits the efficacy of the bi-therapy by altering the antitumor CD8 T-cell responses. Finally, the use of a small molecule CCR4 antagonist to prevent T_regs induction considerably improved the efficacy of the bi-therapy by enhancing CD8 T cells-mediated antitumor immunity. Taken together, our study highlights the potential interest of combining cancer vaccines with drugs that promote memory CD8 T cells and inhibit T_regs .

Metabolism of T Lymphocytes in Health and Disease

Adaptive immune responses that occur in infection, cancer, and autoimmune as well as allergic diseases involve the participation of T cells. T cells travel throughout the body searching for antigens, which are recognized via the major histocompatibility complexes. In the healthy organism, these T cells maintain metabolic quiescence until they encounter a potentially cognate antigen. Once activated, e.g., during an infection or tissue damage, T cells switch their metabolic program to gain energy and building blocks to maintain cellular homeostasis and to fulfill their specific immune functions involving clonal expansion and/or differentiation into effector and memory T cells to ultimately ensure host survival. Thus, differences in metabolism in healthy and pathogenic T cells provide an explanation for dysfunctionality of T-cell responses in metabolic disorders, autoimmunity, and cancer. Here, we summarize current knowledge on T-cell metabolism during the maintenance of homeostasis, activation, and differentiation as well as over the course of time that memory is generated in health and in diseased states such as autoimmunity and cancer.

Synthetic vaccine particles for durable cytolytic T lymphocyte responses and anti-tumor immunotherapy

We previously reported that synthetic vaccine particles (SVP) encapsulating antigens and TLR agonists resulted in augmentation of immune responses with minimal production of systemic inflammatory cytokines. Here we evaluated two different polymer formulations of SVP-encapsulated antigens and tested their ability to induce cytolytic T lymphocytes (CTL) in combination with SVP-encapsulated adjuvants. One formulation led to efficient antigen processing and cross-presentation, rapid and sustained CTL activity, and expansion of CD8⁺ T cell effector memory cells locally and centrally, which persisted for at least 1–2 years after a single immunization. SVP therapeutic dosing resulted in suppression of tumor growth and a substantial delay in mortality in several syngeneic mouse cancer models. Treatment with checkpoint inhibitors and/or cytotoxic drugs, while suboptimal on their own, showed considerable synergy with SVP immunization. SVP encapsulation of endosomal TLR agonists provided superior CTL induction, therapeutic benefit and/or improved safety profile compared to free adjuvants. SVP vaccines encapsulating mutated HPV-16 E7 and E6/E7 recombinant proteins led to induction of broad CTL activity and strong inhibition of TC-1 tumor growth, even when administered therapeutically 13–14 days after tumor inoculation in animals bearing palpable tumors. A pilot study in non-human primates showed that SVP-encapsulated E7/E6 adjuvanted with SVP-encapsulated poly(I:C) led to robust induction of antigen-specific T and B cell responses.

Combination of dual mTORC1/2 inhibition and immune-checkpoint blockade potentiates anti-tumour immunity

mTOR inhibition can promote or inhibit immune responses in a context dependent manner, but whether this will represent a net benefit or be contraindicated in the context of immunooncology therapies is less understood. Here, we report that the mTORC1/2 dual kinase inhibitor vistusertib (AZD2014) potentiates anti-tumour immunity in combination with anti-CTLA-4 (αCTLA-4), αPD-1 or αPD-L1 immune checkpoint blockade. Combination of vistusertib and immune checkpoint blocking antibodies led to tumour growth inhibition and improved survival of MC-38 or CT-26 pre-clinical syngeneic tumour models, whereas monotherapies were less effective. Underlying these combinatorial effects, vistusertib/immune checkpoint combinations reduced the occurrence of exhausted phenotype tumour infiltrating lymphocytes (TILs), whilst increasing frequencies of activated Th1 polarized T-cells in tumours. Vistusertib alone was shown to promote a Th1 polarizing proinflammatory cytokine profile by innate primary immune cells. Moreover, vistusertib directly enhanced activation of effector T-cell and survival, an effect that was critically dependent on inhibitor dose. Therefore, these data highlight direct, tumour-relevant immune potentiating benefits of mTOR inhibition that complement immune checkpoint blockade. Together, these data provide a clear rationale to investigate such combinations in the clinic.

TSC2-deficient tumors have evidence of T cell exhaustion and respond to anti-PD-1/anti-CTLA-4 immunotherapy

Tuberous sclerosis complex (TSC) is an incurable multisystem disease characterized by mTORC1-hyperactive tumors. TSC1/2 mutations also occur in other neoplastic disorders, including lymphangioleiomyomatosis (LAM) and bladder cancer. Whether TSC-associated tumors will respond to immunotherapy is unknown. We report here that the programmed death 1 coinhibitory receptor (PD-1) is upregulated on T cells in renal angiomyolipomas (AML) and pulmonary lymphangioleiomyomatosis (LAM). In C57BL/6J mice injected with syngeneic TSC2-deficient cells, anti-PD-1 alone decreased 105K tumor growth by 67% (P < 0.0001); the combination of PD-1 and CTLA-4 blockade was even more effective in suppressing tumor growth. Anti-PD-1 induced complete rejection of TSC2-deficient 105K tumors in 37% of mice (P < 0.05). Double blockade of PD-1 and CTLA-4 induced rejection in 62% of mice (P < 0.01). TSC2 reexpression in TSC2-deficient TMKOC cells enhanced antitumor immunity by increasing T cell infiltration and production of IFN-γ/TNF-α by T cells, suggesting that TSC2 and mTORC1 play specific roles in the induction of antitumor immunity. Finally, 1 month of anti-PD-1 blockade reduced renal tumor burden by 53% (P < 0.01) in genetically engineered Tsc2+/- mice. Taken together, these data demonstrate for the first time to our knowledge that checkpoint blockade may have clinical efficacy for TSC and LAM, and possibly other benign tumor syndromes, potentially yielding complete and durable clinical responses.

Combined treatment with simvastatin and rapamycin attenuates cardiac allograft rejection through the regulation of T helper 17 and regulatory T cells

Allograft rejection is an important issue post cardiac transplantation. In order to investigate the effect of combined treatment with simvastatin and rapamycin on allograft rejection, a cardiac transplantation rat model was employed in the present study. The survival time of rats following cardiac transplantation was recorded, while histopathological alterations were assessed by hematoxylin and eosin staining. The levels of transcription factors were measured by reverse transcription-quantitative polymerase chain reaction. In addition, the levels of CD4⁺ interleukin (IL)-17⁺ cells and CD4⁺ forkhead box P3 (FOXP3)⁺ cells in the allografts and CD4⁺ T cells and CD8⁺ T cells in the spleens were detected by flow cytometry. The results of the current study demonstrated that, following treatment with simvastatin and rapamycin, the survival time of model rats was prolonged, and the histopathological damage was attenuated. Treatment with simvastatin and rapamycin also led to decreased retinoic acid receptor-related orphan receptor γt (RORγt) level, increased FOXP3 level, reduced levels of CD4⁺IL-17⁺, CD4⁺ T and CD8⁺ T cells, and increased level of CD4⁺FOXP3⁺ cells. In conclusion, the current study observed that simvastatin and rapamycin performed a synergistic effect to reduce cardiac transplantation rejection. Thus, combined therapy of simvastatin and rapamycin may be a promising adjuvant therapy to reduce rejection post cardiac transplantation.

Lack of MHC class II molecules favors CD8+ T-cell infiltration into tumors associated with an increased control of tumor growth

Regulatory T-cells (Tregs) are crucial for the maintenance of immune tolerance and homeostasis as well as for preventing autoimmune diseases, but their impact on the survival of cancer patients remains controversial. In the TC-1 mouse model of human papillomavirus (HPV)-related carcinoma, we have previously demonstrated that the therapeutic efficacy of the CyaA-E7-vaccine, targeting the HPV-E7 antigen, progressively declines with tumor growth, in correlation with increased intratumoral recruitment of Tregs. In the present study, we demonstrated that these TC-1 tumor-infiltrating Tregs were highly activated, with increased expression of immunosuppressive molecules. Both intratumoral effector CD4⁺ T-cells (Teffs) and Tregs expressed high levels of PD-1, but anti-PD-1 antibody treatment did not impact the growth of the TC-1 tumor nor restore the therapeutic effect of the CyaA-E7 vaccine. To analyze the mechanisms by which Tregs are recruited to the tumor site, we used MHC-II KO mice with drastically reduced numbers of CD4⁺ effector T-cells. We demonstrated that these mice still had significant numbers of Tregs in their lymphoid organs which were recruited to the tumor. In MHC-II KO mice, the growth of the TC-1 tumor was delayed in correlation with a strong increase in the intratumoral recruitment of CD8⁺ T-cells. In addition, in mice that spontaneously rejected their tumors, the infiltration of E7-specific CD8⁺ T-cells was significantly higher than in MHC-II KO mice with a growing tumor. These results demonstrate that tumor-specific CD8⁺ T-cells can be efficiently activated and recruited in the absence of MHC class II molecules and of CD4⁺ T-cell help.

The spectrum of T cell metabolism in health and disease

In healthy individuals, metabolically quiescent T cells survey lymph nodes and peripheral tissues in search of cognate antigens. During infection, T cells that encounter cognate antigens are activated and - in a context-specific manner - proliferate and/or differentiate to become effector T cells. This process is accompanied by important changes in cellular metabolism (known as metabolic reprogramming). The magnitude and spectrum of metabolic reprogramming as it occurs in T cells in the context of acute infection ensure host survival. By contrast, altered T cell metabolism, and hence function, is also observed in various disease states, in which T cells actively contribute to pathology. In this Review, we introduce the idea that the spectrum of immune cell metabolic states can provide a basis for categorizing human diseases. Specifically, we first summarize the metabolic and interlinked signalling requirements of T cells responding to acute infection. We then discuss how metabolic reprogramming of T cells is linked to disease.

Metabolic and Epigenetic Coordination of T Cell and Macrophage Immunity

Recognition of pathogens by innate and adaptive immune cells instructs rapid alterations of cellular processes to promote effective resolution of infection. To accommodate increased bioenergetic and biosynthetic demands, metabolic pathways are harnessed to maximize proliferation and effector molecule production. In parallel, activation initiates context-specific gene-expression programs that drive effector functions and cell fates that correlate with changes in epigenetic landscapes. Many chromatin- and DNA-modifying enzymes make use of substrates and cofactors that are intermediates of metabolic pathways, providing potential cross talk between metabolism and epigenetic regulation of gene expression. In this review, we discuss recent studies of T cells and macrophages supporting a role for metabolic activity in integrating environmental signals with activation-induced gene-expression programs through modulation of the epigenome and speculate as to how this may influence context-specific macrophage and T cell responses to infection.

Impact of age and cytomegalovirus on CD8+ T-cell compartment remodeling after solid organ transplantation: A one-year follow-up study

Cytomegalovirus (CMV), a member of the β-herpesvirus family, is a major complicating infection in transplant patients. CMV latency has a long-term impact on CD8⁺ T-cell differentiation. It is unclear, however, whether this effect can be detected in one-year period. To investigate this, we analyzed the remodeling of the CD8⁺ T-cell compartment during the first year after solid organ transplantation. A total of 55 kidney or lung transplant patients were recruited. CD8⁺ T-cell subsets were prospectively analyzed at pretransplant, at 3 or 6months and 12months after transplantation (mo post-Tx). A significant increase in the frequency of CD27^-CD28^-CD8⁺ T cells (from 32.8% to 42.3%; p=0.014) was observed from pretransplant to 12mo post-Tx. Further analysis, however, showed that the largest expansion was observed from 3/6 to 12mo post-Tx whereas small non-significant variations were observed from pretransplant to 3/6mo post-Tx. The adjusted analysis showed that age and CMV seropositivity were statistically associated with the baseline frequency of CD27^-CD28^-CD8⁺ T cells. Additionally, CMV replication was related to the posttransplant expansion of this subpopulation, since it was not observed in patients without CMV viremia (24% vs. 4.2%). The results indicate that the expanded frequency associated with late CMV replication is additive to the baseline frequency related to aging and CMV seropositivity. If the expanded frequency remains at this high level for a long period it might have clinical consequences related to the control of future reactivations of CMV or of other related viruses.

Single vs. combination immunotherapeutic strategies for glioma

INTRODUCTION

Malignant gliomas are highly invasive tumors, associated with a dismal survival rate despite standard of care, which includes surgical resection, radiotherapy and chemotherapy with temozolomide (TMZ). Precision immunotherapies or combinations of immunotherapies that target unique tumor-specific features may substantially improve upon existing treatments. Areas covered: Clinical trials of single immunotherapies have shown therapeutic potential in high-grade glioma patients, and emerging preclinical studies indicate that combinations of immunotherapies may be more effective than monotherapies. In this review, the authors discuss emerging combinations of immunotherapies and compare efficacy of single vs. combined therapies tested in preclinical brain tumor models. Expert opinion: Malignant gliomas are characterized by a number of factors which may limit the success of single immunotherapies including inter-tumor and intra-tumor heterogeneity, intrinsic resistance to traditional therapies, immunosuppression, and immune selection for tumor cells with low antigenicity. Combination of therapies which target multiple aspects of tumor physiology are likely to be more effective than single therapies. While a limited number of combination immunotherapies are described which are currently being tested in preclinical and clinical studies, the field is expanding at an astounding rate, and endless combinations remain open for exploration.

Low-dose controlled release of mTOR inhibitors maintains T cell plasticity and promotes central memory T cells

An important goal for improving vaccine and immunotherapy technologies is the ability to provide further control over the specific phenotypes of T cells arising from these agents. Along these lines, frequent administration of rapamycin (Rapa), a small molecule inhibitor of the mammalian target of rapamycin (mTOR), exhibits a striking ability to polarize T cells toward central memory phenotypes (T_CM), or to suppress immune function, depending on the concentrations and other signals present during administration. T_CM exhibit greater plasticity and proliferative capacity than effector memory T cells (T_EFF) and, therefore, polarizing vaccine-induced T cells toward T_CM is an intriguing strategy to enhance T cell expansion and function against pathogens or tumors. Here we combined biodegradable microparticles encapsulating Rapa (Rapa MPs) with vaccines composed of soluble peptide antigens and molecular adjuvants to test if this approach allows polarization of differentiating T cells toward T_CM. We show Rapa MPs modulate DC function, enhancing secretion of inflammatory cytokines at very low doses, and suppressing function at high doses. While Rapa MP treatment reduced - but did not stop - T cell proliferation in both CD4⁺ and CD8⁺ transgenic T cell co-cultures, the expanding CD8⁺ T cells differentiated to higher frequencies of T_CM at low doses of MP Rapa MPs. Lastly, we show in mice that local delivery of Rapa MPs to lymph nodes during vaccination either suppresses or enhances T cell function in response to melanoma antigens, depending on the dose of drug in the depots. In particular, at low Rapa MP doses, vaccines increased antigen-specific T_CM, resulting in enhanced T cell expansion measured during subsequent booster injections over at least 100days.

T cells conditioned with MDSC show an increased anti-tumor activity after adoptive T cell based immunotherapy

The success of adoptive T cell-based immunotherapy (ACT) in cancer is limited in part by the accumulation of myeloid-derived suppressor cells (MDSC), which block several T cell functions, including T cell proliferation and the expression of various cytotoxic mediators. Paradoxically, the inhibition of CD8+ T cell differentiation into cytotoxic populations increased their efficacy after ACT into tumor-bearing hosts. Therefore, we aimed to test the impact of conditioning CD8+ T cells with MDSC on their differentiation potential and ACT efficacy. Our results indicate that MDSC impaired the progression of CD8+ T cells into effector populations, without altering their activation status, production of IL-2, or signaling through the T cell receptor. In addition, culture of CD8+ T cells with MDSC resulted in an increased ACT anti-tumor efficacy, which correlated with a higher frequency of the transferred T cells and elevated IFNγ production. Interestingly, activated CD62L+ CD8+ T cells were responsible for the enhanced anti-tumor activity showed by MDSC-exposed T cells. Additional results showed a decreased protein synthesis rate and lower activity of the mammalian/mechanistic target of rapamycin (mTOR) in T cells conditioned with MDSC. Silencing of the negative mTOR regulator tuberous sclerosis complex-2 in T cells co-cultured with MDSC restored mTOR activity, but resulted in T cell apoptosis. These results indicate that conditioning of T cells with MDSC induces stress survival pathways mediated by a blunted mTOR signaling, which regulated T cell differentiation and ACT efficacy. Continuation of this research will enable the development of better strategies to increase ACT responses in cancer.

Constitutive Glycolytic Metabolism Supports CD8+ T Cell Effector Memory Differentiation during Viral Infection

Extensive metabolic changes accompany T cell activation, including a switch to glycolytic energy production and increased biosynthesis. Recent studies suggest that subsequent return to reliance on oxidative phosphorylation and increasing spare respiratory capacity are essential for the differentiation of memory CD8⁺ T cells. In contrast, we found that constitutive glycolytic metabolism and suppression of oxidative phosphorylation in CD8⁺ T cells, achieved by conditional deletion of hypoxia-inducible factor regulator Vhl, accelerated CD8⁺ memory cell differentiation during viral infection. Despite sustained glycolysis, CD8⁺ memory cells emerged that upregulated key memory-associated cytokine receptors and transcription factors and showed a heightened response to secondary challenge. In addition, increased glycolysis not only permitted memory formation, but it also favored the formation of long-lived effector-memory CD8⁺ T cells. These data redefine the role of cellular metabolism in memory cell differentiation, showing that reliance on glycolytic metabolism does not hinder formation of a protective memory population.

Emerging concepts of T cell metabolism as a target of immunotherapy

T cells have a pivotal protective role in defense against infection and cancer but also are instrumental in the development of many autoimmune diseases. The regulation of nutrient uptake and utilization in T cells is critically important for the control of their differentiation, and manipulating metabolic pathways in these cells can alter their function and longevity. While the importance of T cell metabolic remodeling in different physiological settings is not fully understood, there is a growing realization that inappropriate metabolic remodeling underlies many aberrant immune responses and that manipulating cellular metabolism can beneficially enhance or temper immunity. Here we comment on the basic metabolic pathways in T cells, followed by a discussion on up-to-date findings about the relationship between metabolism and T cell function and longevity. Furthermore, we expand on potential approaches and applications in which T cells might be manipulated by the reprogramming of metabolic pathways for therapeutic purposes.

Sirolimus in Advanced Epithelioid Hemangioendothelioma: A Retrospective Case-Series Analysis from the Italian Rare Cancer Network Database

BACKGROUND

The aim of this study was to report on sirolimus activity in a series of patients with hemangioendothelioma (HE) treated at the National Cancer Institute, Milan (Istituto Nazionale Tumori; INT) and within the Italian Rare Cancer Network ("Rete Tumori Rari"; RTR).

METHODS

We retrospectively reviewed patients with advanced and progressing epithelioid hemangioendothelioma (EHE) treated with sirolimus at the INT and/or within the RTR. Pathologic review and molecular analysis for WWTR1 rearrangement were performed. Sirolimus was administered until unacceptable toxicity or progression, with the dose being adjusted to reach target plasma levels of 15-20 ng/dL. Responses were assessed using the Response Evaluation Criteria In Solid Tumors (RECIST) criteria.

RESULTS

Since 2005, 18 patients (17 EHE, 1 retiform HE; 1 locally advanced, 17 metastatic; WWTR1 rearrangement: 16) have been identified, with 17/18 patients being evaluable for response. Mean sirolimus daily dose was 4.5 mg. According to RECIST, best responses in EHE were 1 partial response (PR), 12 stable disease (SD), and 3 progressive disease (PD); the patient with retiform HE also achieved a PR, lasting >2 years. Four patients with a reversed interval progression on interruption were observed. Median overall survival was 16 months, and median progression-free survival was 12 months (range 1-45), with four patients progression-free at 24 months. The clinical benefit (complete response [CR] + PR + SD >6 months) was 56 %. Seven patients receiving sirolimus experienced an increase in pleural/peritoneal effusion plus worsening of tumor-related symptoms; six of these patients died within 1-8 months from evidence of effusion progression, while a RECIST PD was assessed in two of seven patients.

CONCLUSIONS

A clinical benefit was achieved in 56 % of patients receiving sirolimus, which lasted >24 months in four patients. Most patients with pleural effusion did not benefit from sirolimus and had a poor outcome.

Trehalose, sucrose and raffinose are novel activators of autophagy in human keratinocytes through an mTOR-independent pathway

Trehalose is a natural disaccharide that is found in a diverse range of organisms but not in mammals. Autophagy is a process which mediates the sequestration, lysosomal delivery and degradation of proteins and organelles. Studies have shown that trehalose exerts beneficial effects through inducing autophagy in mammalian cells. However, whether trehalose or other saccharides can activate autophagy in keratinocytes is unknown. Here, we found that trehalose treatment increased the LC3-I to LC3-II conversion, acridine orange-stained vacuoles and GFP-LC3B (LC3B protein tagged with green fluorescent protein) puncta in the HaCaT human keratinocyte cell line, indicating autophagy induction. Trehalose-induced autophagy was also observed in primary keratinocytes and the A431 epidermal cancer cell line. mTOR signalling was not affected by trehalose treatment, suggesting that trehalose induced autophagy through an mTOR-independent pathway. mTOR-independent autophagy induction was also observed in HaCaT and HeLa cells treated with sucrose or raffinose but not in glucose, maltose or sorbitol treated HaCaT cells, indicating that autophagy induction was not a general property of saccharides. Finally, although trehalose treatment had an inhibitory effect on cell proliferation, it had a cytoprotective effect on cells exposed to UVB radiation. Our study provides new insight into the saccharide-mediated regulation of autophagy in keratinocytes.

Enhanced Tumor Control with Combination mTOR and PD-L1 Inhibition in Syngeneic Oral Cavity Cancers

Significant subsets of patients with oral cancer fail to respond to single-agent programmed death (PD) blockade. Syngeneic models of oral cancer were used to determine if blocking oncogenic signaling improved in vivo responses to PD-L1 monoclonal antibody (mAb). Anti-PD-L1 enhanced durable primary tumor control and survival when combined with mTOR (rapamycin), but not in combination with MEK inhibition (PD901) in immunogenic MOC1 tumors. Conversely, PD-L1 mAb did not enhance tumor control in poorly immunogenic MOC2 tumors. Rapamycin enhanced expansion of peripheral antigen-specific CD8 T cells and IFNγ production following ex vivo antigen stimulation. More CD8 T cells infiltrated and were activated after PD-L1 mAb treatment in mice with immunogenic MOC1 tumors, which were stable or increased by the addition of rapamycin, but suppressed when PD901 was added. Rapamycin increased IFNγ production capacity in peripheral and tumor-infiltrating CD8 T cells. In vivo antibody depletion revealed a CD8 T-cell-dependent, and not NK cell-dependent mechanism of tumor growth inhibition after treatment with rapamycin and PD-L1 mAb, ruling out significant effects from NK cell-mediated antibody-dependent cellular cytotoxicity. Rapamycin also enhanced IFNγ or PD-L1 mAb treatment-associated induction of MHC class I expression on MOC1 tumor cells, an effect abrogated by depleting infiltrating CD8 T cells from the tumor microenvironment. These data conflict with traditional views of rapamycin as a universal immunosuppressant, and when combined with evidence of enhanced antitumor activity with the combination of rapamycin and PD-L1 mAb, suggest that this treatment combination deserves careful evaluation in the clinical setting. Cancer Immunol Res; 4(7); 611-20. ©2016 AACR.

Combination of mTOR and EGFR targeting in an orthotopic xenograft model of head and neck cancer

OBJECTIVES/HYPOTHESIS

Recent preclinical and clinical studies on head and neck squamous cell carcinoma (HNSCC) revealed synergistic effects when combining anti-EGFR agents with conventional chemotherapeutic drugs. Activation of the PI3-kinase/AKT/mTOR signaling pathway has been identified as an important mechanism implicated in tumor progression and resistance to EGFR inhibitors. The aim of this study was to investigate the effects of combining the mTOR inhibitor temsirolimus (Tem) with the anti-EGFR agent cetuximab (Cet) and conventional chemotherapeutic drugs (cisplatin and fluorouracil (C/F)) on an orthotopic model of HNSCC.

STUDY DESIGN

Preclinical in vivo study.

METHODS

We evaluated the anti-tumor efficacy (measured tumor volume) of Tem, Cet, and C/F, administered alone or in combination. Investigations were performed using a human HNSCC cell line, CAL33, injected into the mouth floor of nude mice.

RESULTS

As compared with the control, the combination of Tem and Cet led to the highest tumor inhibition and induced almost complete tumor growth arrest (P = 0.001). Tem significantly enhanced the impact of the Cet-C/F combination on tumor growth (P < 0.001). The highest inhibitory effects of treatments on cell proliferation (Ki67 labeling), MAPK (pP42/44 labeling), and PI3K/AKT/mTOR (pS6R labeling) signaling pathways were found with the Tem-Cet association.

CONCLUSION

In this orthotopic HNSCC model, the combination of Tem with Cet produced synergistic effects on tumor growth. These results were corroborated by a strong inhibition of both MAPK and PI3K-mTOR signaling pathways.

LEVEL OF EVIDENCE

N/A.