Th1-like Treg cells are dressed to suppress anti-tumor immunity

Immunomodulatory Peptides for Tumor Treatment

Peptides exhibit various biological activities, including biorecognition, cell targeting, and tumor penetration, and can stimulate immune cells to elicit immune responses for tumor immunotherapy. Peptide self-assemblies and peptide-functionalized nanocarriers can reduce the effect of various biological barriers and the degradation by peptidases, enhancing the efficiency of peptide delivery and improving antitumor immune responses. To date, the design and development of peptides with various functionalities have been extensively reviewed for enhanced chemotherapy; however, peptide-mediated tumor immunotherapy using peptides acting on different immune cells, to the knowledge, has not yet been summarized. Thus, this work provides a review of this emerging subject of research, focusing on immunomodulatory anticancer peptides. This review introduces the role of peptides in the immunomodulation of innate and adaptive immune cells, followed by a link between peptides in the innate and adaptive immune systems. The peptides are discussed in detail, following a classification according to their effects on different innate and adaptive immune cells, as well as immune checkpoints. Subsequently, two delivery strategies for peptides as drugs are presented: peptide self-assemblies and peptide-functionalized nanocarriers. The concluding remarks regarding the challenges and potential solutions of peptides for tumor immunotherapy are presented.

Platelet factor 4-induced TH1-Treg polarization suppresses antitumor immunity

The tumor microenvironment (TME) contains a number of immune-suppressive cells such as T helper 1-polarized regulatory T cells (TH1-Treg cells). However, little is known about the mechanism behind the abundant presence of TH1-Treg cells in the TME. We demonstrate that selective depletion of arginase I (Arg1)-expressing tumor-associated macrophages (Arg1+ TAMs) inhibits tumor growth and concurrently reduces the ratio of TH1-Treg cells in the TME. Arg1+ TAMs secrete the chemokine platelet factor 4 (PF4), which reinforces interferon-γ (IFN-γ)-induced Treg cell polarization into TH1-Treg cells in a manner dependent on CXCR3 and the IFN-γ receptor. Both genetic PF4 inactivation and PF4 neutralization hinder TH1-Treg cell accumulation in the TME and reduce tumor growth. Collectively, our study highlights the importance of Arg1+ TAM-produced PF4 for high TH1-Treg cell levels in the TME to suppress antitumor immunity.

Lipid peroxidation of immune cells in cancer

Growing evidence indicates that cellular metabolism is a critical determinant of immune cell viability and function in antitumor immunity and lipid metabolism is important for immune cell activation and adaptation to the tumor microenvironment (TME). Lipid peroxidation is a process in which oxidants attack lipid-containing carbon-carbon double bonds and is an important part of lipid metabolism. In the past decades, studies have shown that lipid peroxidation participates in signal transduction to control cell proliferation, differentiation, and cell death, which is essential for cell function execution and human health. More importantly, recent studies have shown that lipid peroxidation affects immune cell function to modulate tumor immunity and antitumor ability. In this review, we briefly overview the effect of lipid peroxidation on the adaptive and innate immune cell activation and function in TME and discuss the effectiveness and sensitivity of the antitumor ability of immune cells by regulating lipid peroxidation.