Dynamic increase of M2 macrophages is associated with disease progression of colorectal cancers following cetuximab-based treatment

DNMT1-mediated NR3C1 DNA methylation enables transcription activation of connexin40 and augments angiogenesis during colorectal cancer progression

Colorectal cancer (CRC) continues to be a major contributor to cancer-related mortality. Connexin 40 (CX40) is one of the major gap junction proteins with the capacity in regulating cell-to-cell communication and angiogenesis. This study investigates its role in angiogenesis in CRC and explores the regulatory mechanism. Aberrant high CX40 expression was detected in tumor tissues, which was associated with a poor prognosis in CRC patients. Elevated CX40 expression was detected in CRC cell lines as well. Conditioned medium of SW620 and HT29 cell lines was used to induce angiogenesis of human umbilical vein endothelial cells (HUVECs). CX40 knockdown in CRC cells reduced angiogenesis and mobility of HUVECs and blocked CRC cell proliferation, mobility, and survival. Following bioinformatics predictions, we validated by chromatin immunoprecipitation and luciferase assays that nuclear receptor subfamily 3 group C member 1 (NR3C1), which was poorly expressed in CRC samples, suppressed CX40 transcription. The poor NR3C1 expression was attributive to DNA hypermethylation induced by DNA methyltransferase 1 (DNMT1). Restoration of NR3C1 suppressed the pro-angiogenic effect, proliferation and survival, and tumorigenic activity of CRC cells, which were, however, rescued by CX40 upregulation. Collectively, this study demonstrates that transcription activation of CX40 upon DNMT1-mediated NR3C1 DNA methylation potentiates angiogenesis in CRC.

Small extracellular vesicle TGF-β in cancer progression and immune evasion

Transforming growth factor-β (TGF-β) is a well-known cytokine that controls various processes in normal physiology and disease context. Strong preclinical and clinical literature supports the crucial roles of the TGF-β in several aspects of cancer biology. Recently emerging evidence reveals that the release of TGF-β from tumor/immune/stromal cells in small extracellular vesicles (sEVs) plays an important part in tumor development and immune evasion. Hence, this review aims to address the packaging, release, and signaling pathways of TGF-β carried in sEVs (sEV-TGF-β) in cancer, and to explore its underpinning roles in tumor development, growth, progression, metastasis, etc. We also highlight key progresses in deciphering the roles of sEV-TGF-β in subverting anti-tumor immune responses. The paper ends with a focus on the clinical significance of TGF-β carried in sEVs and draws attention to its diagnostic, therapeutic, and prognostic importance.

Two tripartite classification systems of CD86+ and CD206+ macrophages are significantly associated with tumor recurrence in stage II-III colorectal cancer

Introduction

The prognostic value of tumor-associated macrophages remains unclear in colorectal cancer (CRC). Two tripartite classification systems, namely, ratio and quantity subgroups, were investigated as the prognostic stratification tools for stage II-III CRC.

Methods

We assessed the infiltration intensity of CD86⁺ and CD206⁺ macrophages in 449 cases with stage II-III disease by immunohistochemical staining. Ratio subgroups were defined by the lower- and upper-quartile points of CD206⁺/(CD86⁺+CD206⁺) macrophage ratio, including the low-, moderate-, and high-ratio subgroups. Quantity subgroups were defined by the median points of CD86⁺ and CD206⁺ macrophages and included the low-, moderate-, and high-risk subgroups. The main analysis was recurrence-free survival (RFS) and overall survival (OS).

Results

Ratio subgroups (RFS/OS: HR=2.677/2.708, all p<0.001) and quantity subgroups (RFS/OS: HR=3.137/3.250, all p<0.001) could serve as independent prognostic indicators that effectively predicted survival outcomes. More importantly, log-rank test revealed that patients in the high-ratio (RFS/OS: HR=2.950/3.151, all p<0.001) or high-risk (RFS/OS: HR=3.453/3.711, all p<0.001) subgroup exhibited decreased survival outcomes after adjuvant chemotherapy. The predictive accuracy of the quantity subgroups within 48 months was higher than that of the ratio subgroups and tumor stage (all p<0.05).

Conclusions

Ratio and quantity subgroups could serve as independent prognostic indicators that could potentially be incorporated into the tumor staging algorithm to improve prognostic stratification and provide better predictions of survival outcomes in stage II-III CRC after adjuvant chemotherapy.

Training vs. Tolerance: The Yin/Yang of the Innate Immune System

For almost nearly a century, memory functions have been attributed only to acquired immune cells. Lately, this paradigm has been challenged by an increasing number of studies revealing that innate immune cells are capable of exhibiting memory-like features resulting in increased responsiveness to subsequent challenges, a process known as trained immunity (known also as innate memory). In contrast, the refractory state of endotoxin tolerance has been defined as an immunosuppressive state of myeloid cells portrayed by a significant reduction in the inflammatory capacity. Both training as well tolerance as adaptive features are reported to be accompanied by epigenetic and metabolic alterations occurring in cells. While training conveys proper protection against secondary infections, the induction of endotoxin tolerance promotes repairing mechanisms in the cells. Consequently, the inappropriate induction of these adaptive cues may trigger maladaptive effects, promoting an increased susceptibility to secondary infections—tolerance, or contribute to the progression of the inflammatory disorder—trained immunity. This review aims at the discussion of these opposing manners of innate immune and non-immune cells, describing the molecular, metabolic and epigenetic mechanisms involved and interpreting the clinical implications in various inflammatory pathologies.

Major pathways involved in macrophage polarization in cancer

Macrophages play an important role in tissue homeostasis, tissue remodeling, immune response, and progression of cancer. Consequently, macrophages exhibit significant plasticity and change their transcriptional profile and function in response to environmental, tissue, and inflammatory stimuli resulting in pro- and anti-tumor effects. Furthermore, the categorization of tissue macrophages in inflammatory situations remains difficult; however, there is an agreement that macrophages are predominantly polarized into two different subtypes with pro- and anti-inflammatory properties, the so-called M1-like and M2-like macrophages, respectively. These two macrophage classes can be considered as the extreme borders of a continuum of many intermediate subsets. On one end, M1 are pro-inflammatory macrophages that initiate an immunological response, damage tissue integrity, and dampen tumor progression by fostering robust T and natural killer (NK) cell anti-tumoral responses. On the other end, M2 are anti-inflammatory macrophages involved in tissue remodeling and tumor growth, that promote cancer cell proliferation, invasion, tumor metastasis, angiogenesis and that participate to immune suppression. These decisive roles in tumor progression occur through the secretion of cytokines, chemokines, growth factors, and matrix metalloproteases, as well as by the expression of immune checkpoint receptors in the case of M2 macrophages. Moreover, macrophage plasticity is supported by stimuli from the Tumor Microenvironment (TME) that are relayed to the nucleus through membrane receptors and signaling pathways that result in gene expression reprogramming in macrophages, thus giving rise to different macrophage polarization outcomes. In this review, we will focus on the main signaling pathways involved in macrophage polarization that are activated upon ligand-receptor recognition and in the presence of other immunomodulatory molecules in cancer.