Mutations in foregut SOX2+ cells induce efficient proliferation via CXCR2 pathway

CD8+ T cell exhaustion and cancer immunotherapy

Immunotherapy plays an increasingly important role in the treatment of most malignant tumors, and CD8⁺ T cells are the most important antitumor effector cells in the process of immunotherapy, and their number and functional status largely determine the antitumor effect. However, under continuous antigen exposure and the stimulation of inflammatory factors, CD8⁺ T cells gradually show a weakened proliferation and effector function, accompanied by the expression of a variety of inhibitory receptors. This state is known as CD8⁺ T cell "exhaustion" and often leads to the loss of control and progression of tumors. Recent studies provided us a better understanding of the mechanisms of T cell exhaustion, this review provides an overview of the activation, exhaustion mechanisms and exhaustion characteristics of CD8⁺ T cells. Although immunotherapy can reverse the exhaustion of CD8⁺ T cells and significantly improve the antitumor effects, single immunotherapy often has limitations, and it is difficult to achieve satisfactory antitumor effects, therefore, this review also summarizes up-to-date information related to cancer immunotherapy, and these emerging insights provide promising clues to the future management of malignant tumors.

Early development of esophageal squamous cell cancer: Stem cells, cellular origins and early clone evolution

Esophageal squamous cell carcinoma (ESCC), a highly malignant cancer with poor prognosis, is an example of the classical view of cancer development based on stem cell origin and multistep progression. In the past five years, the applications of large-scale sequencing and single-cell sequencing have expanded to human esophageal normal tissues and precancerous lesions, which, coupled with the application of transgenic lineage tracing technology in mouse models, has provided a more comprehensive and detailed understanding of esophageal stem cell heterogeneity and early clonal evolution of ESCC. In this review, we discuss the heterogeneity of esophageal basal-layer stem cells and their potential relationship with cells of ESCC origin. We present evidence that expansion of NOTCH1 mutants may call into play an evolutionarily conserved anti-cancer mechanism and mold the model of early clonal evolution in ESCCs. Finally, we discuss the potential avenues in this context. This review provides a focused understanding of the early development of ESCC, as a background for early tumor detection, intervention, and prevention strategies.

Role of mTOR through Autophagy in Esophageal Cancer Stemness

Esophageal cancer (EC) is a highly aggressive disease with a poor prognosis. Therapy resistance and early recurrences are major obstacles in reaching a better outcome. Esophageal cancer stem-like cells (CSCs) seem tightly related with chemoradiation resistance, initiating new tumors and metastases. Several oncogenic pathways seem to be involved in the regulation of esophageal CSCs and might harbor novel therapeutic targets to eliminate CSCs. Previously, we identified a subpopulation of EC cells that express high levels of CD44 and low levels of CD24 (CD44⁺/CD24^-), show CSC characteristics and reside in hypoxic niches. Here, we aim to clarify the role of the hypoxia-responding mammalian target of the rapamycin (mTOR) pathway in esophageal CSCs. We showed that under a low-oxygen culture condition and nutrient deprivation, the CD44⁺/CD24^- population is enriched. Since both low oxygen and nutrient deprivation may inhibit the mTOR pathway, we next chemically inhibited the mTOR pathway using Torin-1. Torin-1 upregulated SOX2 resulted in an enrichment of the CD44⁺/CD24^- population and increased sphere formation potential. In contrast, stimulation of the mTOR pathway using MHY1485 induced the opposite effects. In addition, Torin-1 increased autophagic activity, while MHY1485 suppressed autophagy. Torin-1-mediated CSCs upregulation was significantly reduced in cells treated with autophagy inhibitor, hydroxychloroquine (HCQ). Finally, a clearly defined CD44⁺/CD24^- CSC population was detected in EC patients-derived organoids (ec-PDOs) and here, MHY1485 also reduced this population. These data suggest that autophagy may play a crucial role in mTOR-mediated CSCs repression. Stimulation of the mTOR pathway might aid in the elimination of putative esophageal CSCs.

Myc Supports Self-Renewal of Basal Cells in the Esophageal Epithelium

It is widely believed that cellular senescence plays a critical role in both aging and cancer, and that senescence is a fundamental, permanent growth arrest that somatic cells cannot avoid. Here we show that Myc plays an important role in self-renewal of esophageal epithelial cells, contributing to their resistance to cellular senescence. Myc is homogeneously expressed in basal cells of the esophageal epithelium and Myc positively regulates their self-renewal by maintaining their undifferentiated state. Indeed, Myc knockout induced a loss of the undifferentiated state of esophageal epithelial cells resulting in cellular senescence while forced MYC expression promoted oncogenic cell proliferation. A superoxide scavenger counteracted Myc knockout-induced senescence, therefore suggesting that a mitochondrial superoxide takes part in inducing senescence. Taken together, these analyses reveal extremely low levels of cellular senescence and senescence-associated phenotypes in the esophageal epithelium, as well as a critical role for Myc in self-renewal of basal cells in this organ. This provides new avenues for studying and understanding the links between stemness and resistance to cellular senescence.