Lighting Up the Fire in the Microenvironment of Cold Tumors: A Major Challenge to Improve Cancer Immunotherapy

Epigenetic regulation of cGAS and STING expression in cancer

Although cancer immunotherapy has become a successful therapeutic strategy in a certain range of solid cancer and hematological malignancies, this efficacy of immunotherapy is impeded by limited success rates due to an immunologically "cold" state. The cGAS-STING signaling pathway is an evolutionarily conserved system which can find cytoplasmic DNA to regulate the innate immune and adaptive immune response. Beyond the host defense and autoimmune disorders, recent advances have now expanded the roles of cGAS-STING that is precise activated and tight regulated to improve anticancer immunity. Mounting evidence now has shown the crucial role of epigenetic regulation in mediating the expression of key genes associated with the cGAS-STING signaling pathway. In this review, we highlight the structure and cellular localization of cGAS and STING as well as intracellular cascade reaction of cGAS-STING signal transduction. We further summarize recent findings of epigenetic regulatory mechanisms that control the expression of cGAS and STING in cancer. The review aims to offer theoretical basis and reference for targeting the epigenetic mechanisms that control cGAS and STING gene expression to promote the development of more effective combination therapeutic regimens to enhance the efficacy of cancer immunotherapy in clinical practice and cancer clinical and cancer research workers.

Integrative Analysis and Validation of a Cancer-associated Fibroblasts Senescence-related Signature for Risk Stratification and Therapeutic Prediction in Esophageal Squamous Cell Carcinoma

Cellular senescence is closely associated with cancer development and progression. There is ample evidence that tumor stromal cells, especially cancer-associated fibroblasts (CAFs) undergo senescence in response to various stimuli. However, the possible biological roles and prognostic significance of senescent CAFs in esophageal squamous cell carcinoma (ESCC) remain unexplored. In this study, we found that CAFs exhibited a significantly higher level of cellular senescence than other cell clusters at the single-cell level. Then, we constructed a CAFs senescence-associated risk model with 7 genes (GEM, SLC2A6, CXCL14, STX11, EFHD2, PTX3, and HCK) through Cox regression and LASSO analysis. Kaplan-Meier survival analysis revealed that the risk model was significantly correlated with worse prognosis in training and validation cohorts. Subsequent analysis indicated that the risk model was an independent prognostic factor. In addition, the signature showed a distinct negative correlation with immune cell infiltration and immunotherapy responses. In vitro experiments showed remarkably higher mRNA and protein levels of prognosis-related genes (STX11 and EFHD2) in senescent CAFs than control group, consistent with the bioinformatics analysis results. Moreover, senescent CAFs significantly promoted ESCC cell proliferation and migration as shown by CCK-8 and scratch assays. In conclusion, our study identified a novel CAFs senescence-based classifier that may help predict prognosis of ESCC, and a thorough characterization of the signature could also be helpful in evaluating the response of ESCC to anti-tumor therapies and provide meaningful clinical options for cancer treatment.

NDR1 mediates PD-L1 deubiquitination to promote prostate cancer immune escape via USP10

Prostate cancer (PCa) is one of the most common male genitourinary system malignancies. Despite the significant benefits of anti-PD-L1 immune checkpoint inhibitor therapy in other cancers, the reasons for its poor therapeutic efficacy in prostate cancer (PCa) remain unclear.NDR1 plays an important role in innate immunity, but its role in tumor immunity and immunotherapy has not been investigated. The role of NDR1 in the immune microenvironment of PCa and the related mechanisms are unknown. Here, we found a positive correlation between NDR1 and PD-L1 expression in PCa. NDR1 significantly inhibits CD8 + T cell infiltration and function, thereby promoting immune escape in prostate cancer.More importantly, NDR1 inhibition significantly enhanced CD8 + T cell activation, which enhanced the therapeutic effect of anti-PD-L1. Mechanistic studies revealed that NDR1 inhibits ubiquitination-mediated PD-L1 degradation via the deubiquitinase USP10, upregulates PD-L1, and promotes PCa immune escape. Thus, our study suggests a unique PD-L1 regulatory mechanism underlying PCa immunotherapy failure. The significance of NDR1 in PCa immune escape and its mechanism of action were clarified, and combined NDR1/PD-L1 inhibition was suggested as an approach to boost PCa immunotherapy effectiveness.

Immunologic tumor microenvironment modulators for turning cold tumors hot

Tumors can be classified into distinct immunophenotypes based on the presence and arrangement of cytotoxic immune cells within the tumor microenvironment (TME). Hot tumors, characterized by heightened immune activity and responsiveness to immune checkpoint inhibitors (ICIs), stand in stark contrast to cold tumors, which lack immune infiltration and remain resistant to therapy. To overcome immune evasion mechanisms employed by tumor cells, novel immunologic modulators have emerged, particularly ICIs targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1/programmed death-ligand 1(PD-1/PD-L1). These agents disrupt inhibitory signals and reactivate the immune system, transforming cold tumors into hot ones and promoting effective antitumor responses. However, challenges persist, including primary resistance to immunotherapy, autoimmune side effects, and tumor response heterogeneity. Addressing these challenges requires innovative strategies, deeper mechanistic insights, and a combination of immune interventions to enhance the effectiveness of immunotherapies. In the landscape of cancer medicine, where immune cold tumors represent a formidable hurdle, understanding the TME and harnessing its potential to reprogram the immune response is paramount. This review sheds light on current advancements and future directions in the quest for more effective and safer cancer treatment strategies, offering hope for patients with immune-resistant tumors.

Microphysiological systems as models for immunologically 'cold' tumors

The tumor microenvironment (TME) is a diverse milieu of cells including cancerous and non-cancerous cells such as fibroblasts, pericytes, endothelial cells and immune cells. The intricate cellular interactions within the TME hold a central role in shaping the dynamics of cancer progression, influencing pivotal aspects such as tumor initiation, growth, invasion, response to therapeutic interventions, and the emergence of drug resistance. In immunologically 'cold' tumors, the TME is marked by a scarcity of infiltrating immune cells, limited antigen presentation in the absence of potent immune-stimulating signals, and an abundance of immunosuppressive factors. While strategies targeting the TME as a therapeutic avenue in 'cold' tumors have emerged, there is a pressing need for novel approaches that faithfully replicate the complex cellular and non-cellular interactions in order to develop targeted therapies that can effectively stimulate immune responses and improve therapeutic outcomes in patients. Microfluidic devices offer distinct advantages over traditional in vitro 3D co-culture models and in vivo animal models, as they better recapitulate key characteristics of the TME and allow for precise, controlled insights into the dynamic interplay between various immune, stromal and cancerous cell types at any timepoint. This review aims to underscore the pivotal role of microfluidic systems in advancing our understanding of the TME and presents current microfluidic model systems that aim to dissect tumor-stromal, tumor-immune and immune-stromal cellular interactions in various 'cold' tumors. Understanding the intricacies of the TME in 'cold' tumors is crucial for devising effective targeted therapies to reinvigorate immune responses and overcome the challenges of current immunotherapy approaches.

Therapeutic Targeting of Hypoxia-Inducible Factors in Cancer

In the realm of cancer therapeutics, targeting the hypoxia-inducible factor (HIF) pathway has emerged as a promising strategy. This study delves into the intricate web of HIF-associated mechanisms, exploring avenues for future anticancer therapies. Framing the investigation within the broader context of cancer progression and hypoxia response, this article aims to decipher the pivotal role played by HIF in regulating genes influencing angiogenesis, cell proliferation, and glucose metabolism. Employing diverse approaches such as HIF inhibitors, anti-angiogenic therapies, and hypoxia-activated prodrugs, the research methodologically intervenes at different nodes of the HIF pathway. Findings showcase the efficacy of agents like EZN-2968, Minnelide, and Acriflavine in modulating HIF-1α protein synthesis and destabilizing HIF-1, providing preliminary proof of HIF-1α mRNA modulation and antitumor activity. However, challenges, including toxicity, necessitate continued exploration and development, as exemplified by ongoing clinical trials. This article concludes by emphasizing the potential of targeted HIF therapies in disrupting cancer-related signaling pathways.

New strategies for the management of triple-negative breast cancer

PURPOSE OF REVIEW

This review highlights important changes in our understanding of triple-negative breast cancer. It highlights important novel approaches in treatment and reviews predicts potential challenges facing the treatment of triple-negative breast cancer.

RECENT FINDINGS

There is a clear shift away from chemotherapy-centric approaches to the treatment of breast cancer, and instead, a move towards incorporating immune checkpoint inhibitors, antibody-drug conjugates, and other targeted therapies. There is a focus on understanding biomarkers and leveraging novel targets in drug development.

SUMMARY

It is now standard of care to use neoadjuvant combination immunotherapy-chemotherapy in patients with Stage 1 and 2 breast cancers. Chemo-immunotherapy combinations when appropriate biomarkers are present (PD-L1) are standard first-line therapy in metastatic triple-negative breast cancer. Antibody-drug conjugates are now a mainstay in the treatment of this disease. These findings have shifted the treatment paradigm of the treatment of triple-negative breast cancer.

Therapeutic In Situ Cancer Vaccine Using Pulsed Stereotactic Body Radiotherapy-A Translational Model

Both radiation and cancer therapeutic vaccine research are more than 100 years old, and their potential is likely underexplored. Antiangiogenics, nanoparticle targeting, and immune modulators are some other established anticancer therapies. In the meantime, immunotherapy usage is gaining momentum in clinical applications. This article proposes the concept of a pulsed/intermittent/cyclical endothelial-sparing single-dose in situ vaccination (ISVRT) schedule distinguishable from the standard therapeutic stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) plans. This ISVRT schedule can repeatedly generate tumor-specific neoantigens and epitopes for primary and immune modulation effects, augment supplementary immune enhancement techniques, activate long-term memory cells, avoid extracellular matrix fibrosis, and essentially synchronize with the vascular normalized immunity cycle. The core mechanisms of ISVRT impacting in situ vaccination would be optimizing cascading antigenicity and adjuvanticity. The present proposed hypothesis can be validated using the algorithm presented. The indications for the proposed concept are locally progressing/metastatic cancers that have failed standard therapies. Immunotherapy/targeted therapy, chemotherapy, antiangiogenics, and vascular-lymphatic normalization are integral to such an approach.

The future of affordable cancer immunotherapy

The treatment of cancer was revolutionized within the last two decades by utilizing the mechanism of the immune system against malignant tissue in so-called cancer immunotherapy. Two main developments boosted cancer immunotherapy: 1) the use of checkpoint inhibitors, which are characterized by a relatively high response rate mainly in solid tumors; however, at the cost of serious side effects, and 2) the use of chimeric antigen receptor (CAR)-T cells, which were shown to be very efficient in the treatment of hematologic malignancies, but failed to show high clinical effectiveness in solid tumors until now. In addition, active immunization against individual tumors is emerging, and the first products have reached clinical approval. These new treatment options are very cost-intensive and are not financially compensated by health insurance in many countries. Hence, strategies must be developed to make cancer immunotherapy affordable and to improve the cost-benefit ratio. In this review, we discuss the following strategies: 1) to leverage the antigenicity of "cold tumors" with affordable reagents, 2) to use microbiome-based products as markers or therapeutics, 3) to apply measures that make adoptive cell therapy (ACT) cheaper, e.g., the use of off-the-shelf products, 4) to use immunotherapies that offer cheaper platforms, such as RNA- or peptide-based vaccines and vaccines that use shared or common antigens instead of highly personal antigens, 5) to use a small set of predictive biomarkers instead of the "sequence everything" approach, and 6) to explore affordable immunohistochemistry markers that may direct individual therapies.