Immune modulations of the tumor microenvironment in response to phototherapy

The tumor microenvironment(TME)promotes pro-tumor and anti-infammatory metabolismsand suppresses the host immune system.It prevents immune cells from fighting against cancereffectively,resulting in limited efficacy of many current cancer treatment modalities.Differenttherapies aim to overcome the immunosuppressive TME by combining various approaches tosynergize their effects for enhanced antitumor activity and augmented stimulation of the im-mune system.Immunotherapy has become a major therapeutic strategy because it unleashes thepower of the immune system by activating,enhancing,and directing immune responses to pre-vent,control,and eliminate cancer.Phototherapy uses light iradiation to induce tumor celldeath through photothermal,photochemical,and photo-immunological interactions.Photo-therapy induces tumor immunogenic cell death,which is a precursor and enhancer for anti-tumorimmunity.However,phototherapy alone has limited effects on long-term and systemic anti-tumor immune responses.Phototherapy can be combined with immunotherapy to improve thetumoricidal effect by killing target tumor cells,enhancing immune cell infiltration in tumors,andrewiring pathways in the TME from antinfammatory to pro-inflammatory.Phototherapy-enhanced immunotherapy triggers effective cooperation bet ween innate and adaptive immunities,specifically targeting the tumor cells,whether they are localized or distant.Herein,the successes and limitations of phototherapy combined with other cancer treatmentmodalities will be discussed.Specifically,we will review the symergistic effects of phototherapy combined with different cancer therapies on tumor elimination and remodeling of the immuno-suppressive TME.Overll,phototherapy,in combination with other therapeutic modalities,canestablish anti-tumor pro-infammatory phenotypes in activated tumor-infiltrating T cells andB cells and activate systemic anti-tumor immune responses.

Inducing immunogenic cell death in immuno-oncological therapies

Immunotherapy has revolutionized cancer treatment and substantially improved patient outcomes with respect to multiple types of tumors.However,most patients cannot benefit from such therapies,mainly due to the intrinsic low immunogenicity of cancer cells(CCs)that allows them to escape recognition by immune cells of the body.Immunogenic cell death(ICD),which is a form of regulated cell death,engages in a complex dialogue between dying CCs and immune cells in the tumor microenvironment(TME),ultimately evoking the damage-associated molecular pattern(DAMP)signals to activate tumor-specific immunity.The ICD inducers mediate the death of CCs and improve both antigenicity and adjuvanticity.At the same time,they reprogram TME with a“cold-warmhot”immune status,ultimately amplifying and sustaining dendritic cell-and T cell-dependent innate sensing as well as the antitumor immune responses.In this review,we discuss how to stimulate ICD based upon the biological properties of CCs that have evolved under diverse stress conditions.Additionally,we highlight how this dynamic interaction contributes to priming tumor immunogenicity,thereby boosting anticancer immune responses.We believe that a deep understanding of these ICD processes will provide a framework for evaluating its vital role in cancer immunotherapy.

A metabolic intervention strategy to break evolutionary adaptability of tumor for reinforced immunotherapy

The typical hallmark of tumor evolution is metabolic dysregulation.In addition to secreting immunoregulatory metabolites,tumor cells and various immune cells display different metabolic pathways and plasticity.Harnessing the metabolic differences to reduce the tumor and immunosuppressive cells while enhancing the activity of positive immunoregulatory cells is a promising strategy.We develop a nanoplatform(CLCeMOF)based on cerium metal-organic framework(CeMOF)by lactate oxidase(LOX)modification and glutaminase inhibitor(CB839)loading.The cascade catalytic reactions induced by CLCeMOF generate reactive oxygen species“storm”to elicit immune responses.Meanwhile,LOX-mediated metabolite lactate exhaustion relieves the immunosuppressive tumor microenvironment,preparing the ground for intracellular regulation.Most noticeably,the immunometabolic checkpoint blockade therapy,as a result of glutamine antagonism,is exploited for overall cell mobilization.It is found that CLCeMOF inhibited glutamine metabolism-dependent cells(tumor cells,immunosuppressive cells,etc.),increased infiltration of dendritic cells,and especially reprogrammed CD8^(+)T lymphocytes with considerable metabolic flexibility toward a highly activated,long-lived,and memory-like phenotype.Such an idea intervenes both metabolite(lactate)and cellular metabolic pathway,which essentially alters overall cell fates toward the desired situation.Collectively,the metabolic intervention strategy is bound to break the evolutionary adaptability of tumors for reinforced immunotherapy.

The ex vivo Microenviroments in MLTC of Poorly Immunogenic Tumor Cells Facilitate Polarization of CD4^+CD25^+ Regulatory T Cells

CD4^＋CD25^＋ regulatory T （TR） cells play an important role in maintaining a balanced peripheral immune system. Recent studies have shown that TR cells may also play a key role in suppressing anti-tumor immune response. In order to investigate the tumor immune microenvironment and its influence on TR polarization, poorly immunogenic tumor cell line Ds （C57BL/6, H-2^b）, immunogenic tumor cell lines FBL3 （C57BL/6, H-2^b） and H22 BALB/c, H-2^d） were used to establish the syngeneic/allogeneic, poorly immunogenic/immunogenic mixed lymphocytes-tumor cell culture （MLTC）. Our results revealed that the proportion of CD4^＋CD25^＋ T cells in MLTC of syngeneic primed splenocytes stimulated with D5 tumor cells was higher than that with H22 cells （0.43% vs 0.044%, and the similar results appeared in allogeneic splenocytes stimulated with D5 tumor cells （0.39% vs 0.04%）. The splenocytes stimulated with supernatant from syngeneic MLTC of D5 tumor cells demonstrated higher proportion of CD4^＋CD25^＋ cells than that from allogeneic MLTC of D5 tumor cells, and the splenocytes stimulated with supernatant from syngeneic or allogeneic MLTC of H22 tumor cells generated lower proportion of CD4^＋CD25^＋ T cells than that of D5 tumor cells. The TGF-β1 and Th2-oriented cytokines （IL-4 and IL-10） were dominated in supernatants of syngeneic MLTC of poorly immunogenic tumor cells. Our results provided useful information for studying the mechanisms underlying tumor immune surveillance as well as for the tumor immunotherapy.

Cyclic Dinucleotide Self-Assembled Nanoparticles as a Carrier-Free Delivery Platform for STING-Mediated Cancer Immunotherapy

Cyclic dinucleotides(CDNs)are natural agonists of the stimulator of interferon genes(STING),which is an attractive immunotherapy target.Currently,CDNs and their derivatives are being investigated clinically.However,the poor bioavailability of exogenous CDNs has limited their application in immunotherapy.Although nanocarriers are widely used for cytosolic delivery of CDNs,their loading capacity is insufficient,and their complicated composition and purification process raises bio-compatibility concerns.Herein,we report a super-simplified CDN self-assembly strategy for carrier-free delivery of CDNs.In the presence of excess K^(+),CDNs form oligomers which further self-assemble with divalent metal ions(such as Mn^(2+))to form nanoparticles(NPs)in aqueous solution.We demonstrate that the self-assembled CDN NPs promote cellular uptake of CDNs and enhance tumor immunogenicity by remodeling the tumor microenvironment,inducing immunogenic tumor cell death and increasing tumorinfiltrating lymphocytes,which is conducive to the generation of tumor neoantigen-specific T-cell responses.We also demonstrate that the use of CDN NPs alone or in combination with immune checkpoint blockades inhibits tumor growth,highlighting the fact that CDN NPs are a potent platform for cancer immunotherapy.

HDAC inhibitors overcome immunotherapy resistance in B-cell lymphoma

Immunotherapy has been applied successully to treat B-cell lymphomas in preclinical models or clinical settings.However,immunotherapy resistance is a major challenge for B-cell lymphoma treatment.To overcome this issue,combinatorlal therapeutic strategies have been pursued to achieve a better efficacy for treating B-cell lymphomas.One of such strategies is to combine immunotherapy with histone deacetylase(HDAC)inhi-bitors.HDAC inhibitors can potentially increase tumor immunogenicity,promote antitumor immune respon-ses,or reverse immunosuppressive tumor environments.Thus,the combination of HDAC inhibitors and immunotherapy has drawn much attention in current cancer treatment.However,not all HDAC inhibitors are created equal and their net effects are highly dependent on the specific inhibitors used and the HDACs they target.Hence,we suggest that optimal treatment effh-cacy requires personalized design and rational combination based on prognostic biomarkers and unique profiles of HDAC inhibitors.Here,we discuss the possible mechanisms by which B-cell lymphomas acquire immunotherapy resistance and the effects of HDAC inhibitors on tumor cells and immune cells that could help overcome immunotherapy resistance.