The modulation of PD-L1 induced by the oncogenic HBXIP for breast cancer growth

Research progress on oncoprotein hepatitis B X‑interacting protein (Review)

Hepatitis B X‑interacting protein (HBXIP) is a membrane protein located on the lysosomal surface and encoded by the Lamtor gene. It is expressed by a wide range of tumor types, including breast cancer, esophageal squamous cell carcinoma and hepatocellular carcinoma, and its expression is associated with certain clinicopathological characteristics. In the past decade, research on the oncogenic mechanisms of HBXIP has increased and the function of HBXIP in normal cells has been gradually elucidated. In the present review, the following was discussed: The normal physiological role of the HBXIP carcinogenic mechanism; the clinical significance of high levels of HBXIP expression in different tumors; HBXIP regulation of transcription, post‑transcription and post‑translation processes in tumors; the role of HBXIP in improving the antioxidant capacity of tumor cells; the inhibition of ferroptosis of tumor cells and regulating the metabolic reprogramming of tumor cells; and the role of HBXIP in promoting the malignant progression of tumors. In conclusion, the present review summarized the existing knowledge of HBXIP, established its carcinogenic mechanism and discussed future related research on HBXIP.

PTMs of PD-1/PD-L1 and PROTACs application for improving cancer immunotherapy

Immunotherapy has been developed, which harnesses and enhances the innate powers of the immune system to fight disease, particularly cancer. PD-1 (programmed death-1) and PD-L1 (programmed death ligand-1) are key components in the regulation of the immune system, particularly in the context of cancer immunotherapy. PD-1 and PD-L1 are regulated by PTMs, including phosphorylation, ubiquitination, deubiquitination, acetylation, palmitoylation and glycosylation. PROTACs (Proteolysis Targeting Chimeras) are a type of new drug design technology. They are specifically engineered molecules that target specific proteins within a cell for degradation. PROTACs have been designed and demonstrated their inhibitory activity against the PD-1/PD-L1 pathway, and showed their ability to degrade PD-1/PD-L1 proteins. In this review, we describe how PROTACs target PD-1 and PD-L1 proteins to improve the efficacy of immunotherapy. PROTACs could be a novel strategy to combine with radiotherapy, chemotherapy and immunotherapy for cancer patients.

Challenges Coexist with Opportunities: Spatial Heterogeneity Expression of PD-L1 in Cancer Therapy

Cancer immunotherapy using anti-programmed death-ligand 1 (PD-L1) antibodies has been used in various clinical applications and achieved certain results. However, such limitations as autoimmunity, tumor hyperprogression, and overall low patient response rate impede its further clinical application. Mounting evidence has revealed that PD-L1 is not only present in tumor cell membrane but also in cytoplasm, exosome, or even nucleus. Among these, the dynamic and spatial heterogeneous expression of PD-L1 in tumors is mainly responsible for the unsatisfactory efficacy of PD-L1 antibodies. Hence, numerous studies focus on inhibiting or degrading PD-L1 to improve immune response, while a comprehensive understanding of the molecular mechanisms underlying spatial heterogeneity of PD-L1 can fundamentally transform the current status of PD-L1 antibodies in clinical development. Herein, the concept of spatial heterogeneous expression of PD-L1 is creatively introduced, encompassing the structure and biological functions of various kinds of PD-L1 (including mPD-L1, cPD-L1, nPD-L1, and exoPD-L1). Then an in-depth analysis of the regulatory mechanisms and potential therapeutic targets of PD-L1 is provided, seeking to offer a solid basis for future investigation. Moreover, the current status of agents is summarized, especially small molecular modulators development directed at these new targets, offering a novel perspective on potential PD-L1 therapeutics strategies.

Integrins and Actions of Androgen in Breast Cancer

Androgen has been shown to regulate male physiological activities and cancer proliferation. It is used to antagonize estrogen-induced proliferative effects in breast cancer cells. However, evidence indicates that androgen can stimulate cancer cell growth in estrogen receptor (ER)-positive and ER-negative breast cancer cells via different types of receptors and different mechanisms. Androgen-induced cancer growth and metastasis link with different types of integrins. Integrin αvβ3 is predominantly expressed and activated in cancer cells and rapidly dividing endothelial cells. Programmed death-ligand 1 (PD-L1) also plays a vital role in cancer growth. The part of integrins in action with androgen in cancer cells is not fully mechanically understood. To clarify the interactions between androgen and integrin αvβ3, we carried out molecular modeling to explain the potential interactions of androgen with integrin αvβ3. The androgen-regulated mechanisms on PD-L1 and its effects were also addressed.

Regulation of post-translational modification of PD-L1 and advances in tumor immunotherapy

The immune checkpoint molecules programmed cell death receptor 1 (PD-1) and programmed death ligand 1 (PD-L1) are one of the most promising targets for tumor immunotherapy. PD-L1 is overexpressed on the surface of tumor cells and inhibits T cell activation upon binding to PD⁃1 on the surface of T cells, resulting in tumor immune escape. The therapeutic strategy of targeting PD-1/PD-L1 involves blocking this binding and restoring the tumor-killing effect of immune cells. However, in clinical settings, a relatively low proportion of cancer patients have responded well to PD-1/PD-L1 blockade, and clinical outcomes have reached a bottleneck and no substantial progress has been made. In recent years, PD-L1 post-translation modifications (PTMs) have gradually become a hot topic in the field of PD-L1 research, which will provide new insights to improve the efficacy of current anti-PD-1/PD-L1 therapies. Here, we summarized and discussed multiple PTMs of PD-L1, including glycosylation, ubiquitination, phosphorylation, acetylation and palmitoylation, with a major emphasis on mechanism-based therapeutic strategies (including relevant enzymes and targets that are already in clinical use and that may become drugs in the future). We also summarized the latest research progress of PTMs of PD-L1/PD-1 in regulating immunotherapy. The review provided novel strategies and directions for tumor immunotherapy research based on the PTMs of PD-L1/PD-1.

Antitumor potential of PD-L1/PD-1 post-translational modifications

The immune checkpoint programmed death receptor 1 (PD-1) and programmed death ligand 1 (PD-L1) are biologically important immunosuppressive molecules, and the PD-L1/PD-1-mediated signaling pathway is currently considered one of the main mechanisms of tumor escape immune surveillance. PD-L1 is highly expressed on the cytomembrane of tumor cell and binds to PD-1 receptor of activated T cells. This interaction activates PD-L1/PD-1 downstream signal transduction, inhibiting T cells anti-tumor activity. Therefore, inhibitors of PD-L1/PD-1 activation, showing significant efficacy in some types of tumors, have been widely approved in clinical tumor therapy. Recent research on PD-L1/PD-1 signaling pathway regulation has shown post-translational modifications (PTMs) form of PD-L1 or PD-1, including glycosylation, ubiquitination, phosphorylation, and acetylation, which may play an important role in PD-L1/PD-1 signaling pathway regulation and anti-tumor function of T cells. In this review, we focused on PTMs of PD-L1/PD-1 research and potential applications in tumor immunotherapy. This article is protected by copyright. All rights reserved.