Post-translational modifications (PTMs) of proteins is an important mode of protein function regulation, which is essential for the structure and function of proteins under physiological and pathological conditions, and the types of modifications is wide. Cancer immunotherapy refers to an effective method for cancer treatment by activating or normalizing disabled immune cells. In recent years, researchers have found that many types of PTM are involved in the process of proliferation, activation and metabolic reprogramming of immune cells in cancer microenvironment, and may affect the efficacy of cancer immunotherapy. Therefore, this article reviews the effects of several different PTMs on immune cells in cancer microenvironment, and aims to provide new ideas for cancer immunotherapy.

Calcium-binding protein S100A9 is closely related to inflammation and tumor invasion, and is one of the specific markers of myeloid-derived suppressor cells (MDSC). In this study, a recombinant polypeptide vaccine CTB-S100A9 targeting mouse calcium-binding protein S100A9 was constructed by fusion cholera toxin B subunit (CTB) with S100A9 gene. The CTB-S100A9 fusion protein was expressed in E coli. and purified by Ni⁺ affinity chromatography. Vaccinate the purified recombinant CTB-S100A9 protein supplemented with aluminum hydroxide adjuvant can break the autoimmune tolerance and produce high titer of S100A9 antibody in mice. Moreover, the S100A9 antibody produced by CTB-S100A9 vaccination is more specific and does not cross-react with S100A8. In the mouse 4T1 breast cancer model, CTB-S100A9 vaccination not only has significant tumor prevention effects, but also has significant tumor therapeutic effects. In addition, CTB-S100A9 significantly inhibited lung metastasis in 4T1 mice breast cancer model. Further analysis by flow cytometry showed that CTB-S100A9 vaccination can significantly reduce the tumor induced Treg cells and granulocyte-derived MDSC in 4T1 mice model, and reverse the tumor immunosuppressive environment, thereby promote the anti-tumor efficacy. The animal experiments in this study were carried out under the animal care guidelines approved by the Animal Ethics Committee of the Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine. This study shows that CTB-S100A9 is a good recombinant vaccine that targets the tumor immune-suppression environment and has great potential for the future clinical application.

In recent years, the role of ketone body metabolism in tumor growth, invasion and metastasis has attracted much attention. Succinyl-CoA transferase (SCOT) is a key enzyme in the metabolism of ketone bodies. Its function is to transfer the coenzyme A group of succinyl-CoA to acetoacetate and catalyze the formation of acetoacetyl-CoA, which is the first rate-limiting step in ketone metabolism. Then acetoacetyl-CoA further breaks into two molecules of acetyl-CoA and enters the tricarboxylic acid cycle. Studies have shown that SCOT is highly expressed in a variety of tumors, and is closely related to tumor progression and prognosis of patients, which makes SCOT a potential marker for clinical diagnosis and prognosis evaluation; in addition, inhibition of SCOT activity can hinder the metabolism of ketone bodies in tumor cells, that is, reduce the production of ATP, thereby inhibiting tumor growth, proliferation, invasion and metastasis. This review aims to explore the important role of SCOT in metabolic pathways and its relationship with tumorigenesis and development, and to provide new ideas for exploring tumor metabolism and targeting molecular drugs.

Glioma is the most common primary intracranial tumor, among which glioblastoma (GBM) is the most malignant subtype. Because of its high heterogeneity and invasiveness, GBM can't be completely removed by surgical resection and is also resistance to chemotherapy and radiotherapy. Even after a standard therapy, the median survival time is only 14.6 months, the five-year survival rate is less than 10%, and the relapse of GBM is common. Immunotherapy, a new treatment paradigm, treats cancer through regulating the autologous immune system and the tumor microenvironment. As a promising method to improve the prognosis of GBM, immunotherapy has attracted more and more attention. This paper gives a review to the difficulty, the mainly existing strategies and the bottlenecks in GBM immunotherapy, aiming at providing new direction to improve the prognosis of GBM patients.

Programmed cell death protein 1 (PD-1) is an important immunosuppressive molecule, which combines with programmed cell death 1 ligand 1 (PD-L1) to initiate programmed T-cell death, leading to immune escape of tumor cells. Immune checkpoint inhibitors kill tumor cells by blocking the binding of PD-1 to PD-L1 and reactivating the patient's own immune system. With the approval of anti-PD-1 monoclonal antibodies nivolumab, pembrolizumab and anti-PD-L1 monoclonal antibody atezolizumab by FDA for the treatment of melanoma, advanced non-small cell lung cancer and other cancers, cancer treatment has ushered in a new dawn. However, only 20% of patients achieved long-term efficacy after treatment, and most patients relapsed later. Therefore, it is significant to identify effective biomarkers and develop new targets to improve the response of patients to immuno-therapy. This article reviews on the mechanism of action of anti-PD-1/PD-L1 drugs in tumors, potential biomarkers and the mechanism of acquired drug resistance, as well as combination therapy under research.

Immunotherapy has emerged as one of the major modalities for clinical cancer therapy, along with surgery, chemotherapy, radiotherapy and targeted therapy. However, tumor-targeted delivery of immune therapeutics is challenged by a series of barriers including non-specific release, poor tumor penetration capacity, and insufficient cellular uptake of the therapeutic regimens, which seriously restricted the efficiency and efficacy of immunotherapy. To address above challenges, nanosized drug delivery systems (NDDS) have been extensively exploited to achieve tumor-targeted delivery of immunotherapy drugs. It has been well investigated that solid tumors are of unique characteristics including acidic, hypoxic and enzymatic extracellular microenvironment. Meanwhile, the tumor cells are of acidic, reductant and reactive oxygen species intracellular microenvironment. In recent years, a large variety of tumor microenvironment-activatable NDDS have been exploited to respond specifically to the stimulus of extracellular or intracellular tumor microenvironment for enhancing the accumulation, retention and penetration in the tumor tissue. These NDDS were also employed to promote intracellular uptake and tunable drug release inside the tumor cells. In this review article, we summarized the recent progress of our laboratory using the tumor microenvironment-activatable NDDS for immune efficient therapeutics delivery, and improved cancer immunotherapy. We also briefly discussed the challenges and provided perspective of NDDS-based cancer immunotherapy.

The occurrence and development of tumors are closely related to the tumor microenvironment. Among them, tumor immune microenvironment and tumor metabolic microenvironment play important roles in tumor. Tumor immunotherapy is a way to kill tumor cells by activating the body's immune system. Tumor immuno-therapy has shown good therapeutic effects in a variety of solid tumors. In recent years, significant progress has been made in tumor immunotherapy. The Warburg effect indicates that tumor cells use aerobic glycolysis to acquire energy. In the tumor, the energy metabolism pathway is abnormal, and the tumor microenvironment can induce the reprogramming of tumor cell metabolism. Therefore, targeting tumor metabolism is also of great signifi-cance for tumor treatment. In this paper, we reviewed the research progress of drug targets related to tumor immu-nology and tumor metabolism in recent years, as well as the progress of drug development.

Signal transducer and activator of transcription 3 (STAT3) was found in an abnormal constitutively active status in certain cancer tissues, and under these circumstances the interruption of STAT3 signaling pathway was proposed with the potential anti-cancer efficacy. In this study, our previous reported STAT3 inhibitor Bt354 can inhibit tumor growth in DU145 xenograft mice without affecting body weight. In groups treated with Bt354, the inhibition rate of tumor weight was 58.8%, 62.7% and 73.5% in 10, 20, 40 mg·kg^-1 group, respectively. Particularly, the number of Ki 67 positive cells in the tumor sections was significantly decreased in Bt354 groups. Furthermore, Bt354 inhibited the nuclear translocation of STAT3 and consequently induced cell growth inhibition, apoptosis in DU145 cells. These findings suggest that Bt354 may be a potent anticancer agent for STAT3 activated prostate cancer cells. Procedures for animal study were performed with approval of the Animal Care and Use Committee of the Chinese Academy of Medical Sciences and Peking Union Medical College.

In this study, we used the tumor immunotherapy protein indoleamine 2, 3-dioxygenase 1 (IDO1) as the target, and proposed an enzyme-cell-based tertiary IDO1 inhibitor high throughput screening platform. Firstly, the recombinant human IDO1 protein was expressed by genetic engineering and efficient IDO enzymatic screening system was established. Secondly, A172 cells stimulated with interferon-γ (IFNγ) or constructed plasmid which could highly express human IDO1 protein in HEK293 cells with transient transfection were used to construct the specific IDO1 cell based screening system. Finally, the effect of the compound on kynurenine and tryptophan in mouse plasma was determined by LC/MS/MS method on C57 mice, which could further verify the inhibitory effect of the selected compounds on IDO1 in vivo. The established and optimized enzyme-cell based screening model in this study can efficiently and effectively obtain IDO1 inhibitors in vitro, which lays a good foundation for the rapid development of clinical drugs. Procedures for animal study were performed with approval of the Animal Care and Use Committee of the Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College.

Carnitine palmitoyltransferase 1 (CPT1) is a fatty acid β-oxidative rate-limiting enzyme of fatty acid β-oxidation (FAO) present in the outer membrane of mitochondria, which is closely related to metabolic diseases and tumors. Numerous studies have shown that various subtypes of CPT1 are abnormally expressed in cancer cells and play an important role in resistance to metabolic stress. With the development of tumor immunotherapy, its role in immune cells and organs has also attracted attention. This article aims to review the biological functions of CPT1 and the role of different subtypes in tumor metabolism and immune regulation, and the research progress of its inhibitors, providing new ideas for cancer treatment.