Saturated fatty acids dampen the immunogenicity of cancer by suppressing STING

cGLRs Join Their Cousins of Pattern Recognition Receptor Family to Regulate Immune Homeostasis

Pattern recognition receptors (PRRs) recognize danger signals such as PAMPs/MAMPs and DAMPs to initiate a protective immune response. TLRs, NLRs, CLRs, and RLRs are well-characterized PRRs of the host immune system. cGLRs have been recently identified as PRRs. In humans, the cGAS/STING signaling pathway is a part of cGLRs. cGAS recognizes cytosolic dsDNA as a PAMP or DAMP to initiate the STING-dependent immune response comprising type 1 IFN release, NF-κB activation, autophagy, and cellular senescence. The present article discusses the emergence of cGLRs as critical PRRs and how they regulate immune responses. We examined the role of cGAS/STING signaling, a well-studied cGLR system, in the activation of the immune system. The following sections discuss the role of cGAS/STING dysregulation in disease and how immune cross-talk with other PRRs maintains immune homeostasis. This understanding will lead to the design of better vaccines and immunotherapeutics for various diseases, including infections, autoimmunity, and cancers.

Immune escape of head and neck cancer mediated by the impaired MHC-I antigen presentation pathway

Tumor immune evasion is a hallmark of Head and Neck Cancers. The advent of immune checkpoint inhibitors (ICIs) in the first-line setting has transformed the management of these tumors. Unfortunately, the response rate of Head and Neck Squamous Cell Carcinomas (HNSCC) to ICIs is below 15%, regardless of the human papillomavirus (HPV) status, which might be partially related with impaired antigen presentation machinery (APM). Mechanistically, HNSCC cells are usually defective in the expression of MHC-I associated APM, while this transcriptional pathway is critical for the activation of tumor-killing effector T-cells. To specifically illuminate the phenomenon and seek for therapeutic strategies, this review summarizes the most recently identified role of genetic and functional dysregulation of the MHC-I pathway, specifically through changes at the genetic, epigenetic, post-transcriptional, and post-translational levels, which substantially contributes to HNSCC immune escape and ICI resistance. Several treatment modalities can be potentially exploited to restore APM signaling in tumors, which improves anti-tumor immunity through the activation of interferons, vaccines or rimantadine against HPV and the inhibition of EGFR, SHP-2, PI3K and MEK. Additionally, the combinatorial use of radiotherapy or cytotoxic agents with ICIs can synergize to potentiate APM signaling. Future directions would include further dissection of MHC-I related APM signaling in HNSCC and whether reversing this inhibition in combination with ICIs would elicit a more robust immune response leading to improved response rates in HNSCC. Therapeutic approaches to restore the MHC-I antigen presentation machinery in Head and Neck Cancer. (Red color texts represent the according strategies and the outcomes).

Dietary fat and lipid metabolism in the tumor microenvironment

Metabolic reprogramming has been considered a core hallmark of cancer, in which excessive accumulation of lipids promote cancer initiation, progression and metastasis. Lipid metabolism often includes the digestion and absorption of dietary fat, and the ways in which cancer cells utilize lipids are often influenced by the complex interactions within the tumor microenvironment. Among multiple cancer risk factors, obesity has a positive association with multiple cancer types, while diets like calorie restriction and fasting improve health and delay cancer. Impact of these diets on tumorigenesis or cancer prevention are generally studied on cancer cells, despite heterogeneity of the tumor microenvironment. Cancer cells regularly interact with these heterogeneous microenvironmental components, including immune and stromal cells, to promote cancer progression and metastasis, and there is an intricate metabolic crosstalk between these compartments. Here, we focus on discussing fat metabolism and response to dietary fat in the tumor microenvironment, focusing on both immune and stromal components and shedding light on therapeutic strategies surrounding lipid metabolic and signaling pathways.

Role and clinical significance of immunogenic cell death biomarkers in chemoresistance and immunoregulation of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is one of the most common malignancies in the whole world, with little improvement in the 5-year survival rate due to the occurrence of chemoresistance. With the increasing interests in tumor immune microenvironment, immunogenic cell death (ICD)-induced chemotherapy has shown promising results in enhancing sensitivity to immune checkpoint inhibitors (ICI) and improving the efficiency of tumor immunotherapy. This review summarizes the role of key ICD biomarkers and their underlying molecular mechanisms in HNSCC chemoresistance. The results showed that ICD initiation could significantly improve the survival and prognosis of patients. ICD and its biomarker could also serve as molecular markers for tumor diagnosis and prognosis. Moreover, key components of DAMPs including CALR, HGMB1, and ATP are involved in the regulation of HNSCC chemo-sensitivity, confirming that the key biomarkers of ICD can also be developed into new targets for regulating HNSCC chemoresistance. This review clearly illustrates the theoretical basis for the hypothesis that ICD biomarkers are therapeutic targets involved in HNSCC progression, chemoresistance, and even immune microenvironment regulation. The compilation and investigation may provide new insights into the molecular therapy of HNSCC.

A metabolic clue for STING suppression

A recent report by Heath et al. reveals that obesity could impair cancer immunogenicity and foster a type I interferon (IFN-I)-deprived tumor microenvironment through saturated fatty acid-mediated stimulator of interferon genes (STING) inhibition.