CHEK2 represses breast stromal fibroblasts and their paracrine tumor-promoting effects through suppressing SDF-1 and IL-6

ATM Regulates Differentiation of Myofibroblastic Cancer-Associated Fibroblasts and Can Be Targeted to Overcome Immunotherapy Resistance

Myofibroblastic cancer-associated fibroblast (myoCAF)-rich tumors generally contain few T cells and respond poorly to immune-checkpoint blockade. Although myoCAFs are associated with poor outcome in most solid tumors, the molecular mechanisms regulating myoCAF accumulation remain unclear, limiting the potential for therapeutic intervention. Here, we identify ataxia-telangiectasia mutated (ATM) as a central regulator of the myoCAF phenotype. Differentiating myofibroblasts in vitro and myoCAFs cultured ex vivo display activated ATM signaling, and targeting ATM genetically or pharmacologically could suppress and reverse differentiation. ATM activation was regulated by the reactive oxygen species-producing enzyme NOX4, both through DNA damage and increased oxidative stress. Targeting fibroblast ATM in vivo suppressed myoCAF-rich tumor growth, promoted intratumoral CD8 T-cell infiltration, and potentiated the response to anti-PD-1 blockade and antitumor vaccination. This work identifies a novel pathway regulating myoCAF differentiation and provides a rationale for using ATM inhibitors to overcome CAF-mediated immunotherapy resistance.

SIGNIFICANCE

ATM signaling supports the differentiation of myoCAFs to suppress T-cell infiltration and antitumor immunity, supporting the potential clinical use of ATM inhibitors in combination with checkpoint inhibition in myoCAF-rich, immune-cold tumors.

Origin, activation and heterogeneity of fibroblasts associated with pancreas and breast cancers

Pancreas and breast cancers both contain abundant stromal components within the tumor tissues. A prominent cell type within the stroma is cancer-associated fibroblasts (CAFs). CAFs play critical and complex roles establishing the tumor microenvironment to either promote or prevent tumor progression. Recently, complex genetic models and single cell-based techniques have provided emerging insights on the precise functions and cellular heterogeneity of CAFs. The transformation of normal fibroblasts into CAFs is a key event during tumor initiation and progression. Such coordination between tumor cells and fibroblasts plays an important role in cancer development. Reprograming fibroblasts is currently being explored for therapeutic benefits. In this review, we will discuss recent literature shedding light on the tissues of origin, activation mechanisms, and heterogeneity of CAFs comparing pancreas and breast cancers.

Status of CHEK2 and p53 in patients with early-onset and conventional gastric cancer

Gastric cancer (GC) is the fourth most common cause of cancer-associated death. Based on the age at diagnosis, GC is divided into early-onset GC (EOGC; ≤45 years) and conventional GC (CGC; >45 years). Mutations in the cell cycle checkpoint kinase 2 (CHEK2) and TP53 genes are associated with several types of cancer; however, their genetic defects in GC remain poorly understood. The aim of the present study was to determine the subcellular distribution of the CHEK2 protein and its redistribution following DNA damage, to improve the understanding of the DNA damage response. Genetic alterations and patterns of expression of CHEK2 and p53 proteins were investigated to identify potential biological markers and indicators of GC development. Additionally, the affected signaling pathways and their clinical importance in GC development and associated syndromes were investigated. A total of 196 GC samples (89 CGC and 107 EOGC samples) were used in the present study. DNA from 53 samples (18 CGC and 35 EOGC samples) was sequenced using targeted next-generation sequencing technology to identify and compare common and rare mutations associated with GC. Subsequently, the cytoplasmic and nuclear expression levels of CHEK2, phosphorylated (p)-CHEK2 at threonine 68 and p53 in GC tissues were determined via immunohistochemistry. Sequencing resulted in the identification of 63 single nucleotide polymorphisms (SNPs) in the CHEK2 gene amongst 5 different variants, and the intron variant c.319+379A>G was the most common SNP. In the TP53 gene, 57 different alterations were detected amongst 9 variant types, and the missense variant c.215C>G was the most common. Nuclear CHEK2 expression was high in both the EOGC and CGC subtypes. However, the prevalence of cytoplasmic CHEK2 expression (P<0.001) and nuclear p-CHEK2 expression (P=0.011) was significantly higher in CGC compared with in EOGC tissues. There was a statistically significant difference between high and low cytoplasmic CHEK2 expression in patients with p53-positive EOGC compared with in patients with p53-positive CGC (P=0.002). The present study was designed to determine the association between CHEK2 and p53 expression patterns in patients with EOGC and CGC, as well as genetic alterations in the CHEK2 and TP53 genes.

Cancer associated fibroblasts: role in breast cancer and potential as therapeutic targets

Introduction: Cancer associated fibroblasts (CAFs) are the largest population of stromal cells in breast tumors. Emerging evidence has suggested that CAFs are important players not only in fostering tumor growth and spread but also in altering the tumor response to therapeutic agents. On the basis of these observations, huge efforts have been made to exploit CAFs as potential targets for breast cancer therapy.Areas covered: The current understanding of the hallmarks and biology of CAFs, their multilayered interplay with various cell populations of breast tumor microenvironment toward cancer initiation, progression, metastasis and resistance to anticancer therapies are discussed. In addition, a comprehensive overview of the CAFs-based molecular druggable targets in breast tumors is provided. The most relevant literature, in particular the studies retrieved in Medline in the last 10 years, served for this purpose.Expert opinion: The interest on CAFs as a target to fight breast cancer has becoming a hot topic for drug discovery. Indeed, several CAFs-targeted approaches are emerging as appealing therapeutic strategies in breast cancer. At pre-clinical level, this research field is speedily advancing toward the assessment of successful tactics targeting CAFs in breast cancer. Therefore, anti-CAFs therapies may display an intriguing potential to be exploited in clinical studies.

Exploration of the hub genes and miRNAs in lung adenocarcinoma

In order to investigate the oncogenic mechanisms of lung adenocarcinoma (LUAD), hub genes can be identified by constructing co-expression networks, and the potential linkages between hub genes, transcription factors (TFs) and microRNAs (miRNAs/miRs) can be visualized and identified. In the present study, a total of 12 co-expressed modules were constructed, and 9 of these were significantly correlated with clinical traits in LUAD. The differentially expressed genes and differentially expressed miRNAs were determined, and the targets of differentially expressed miRNA were identified from the hub genes or TFs. The results of the present study demonstrated that 10 hub genes and 12 TFs are the predicted targets for the 5 and 8 differentially expressed miRNAs, respectively. Genes in pink and red modules, which have a high correlation with the clinical trait of days to death, are significantly enriched in 'nucleosome assembly' and 'microtubule-based process', respectively. These results indicated that miR-206, miR-137, miR-153, hub genes and enriched TFs in the pink and red modules exert a potentially pivotal function in the development of LUAD.

Stress responses in stromal cells and tumor homeostasis

In most (if not all) solid tumors, malignant cells are outnumbered by their non-malignant counterparts, including immune, endothelial and stromal cells. However, while the mechanisms whereby cancer cells adapt to microenvironmental perturbations have been studied in great detail, relatively little is known on stress responses in non-malignant compartments of the tumor microenvironment. Here, we discuss the mechanisms whereby cancer-associated fibroblasts and other cellular components of the tumor stroma react to stress in the context of an intimate crosstalk with malignant, endothelial and immune cells, and how such crosstalk influences disease progression and response to treatment.

Germline Proliferation Is Regulated by Somatic Endocytic Genes via JNK and BMP Signaling in Drosophila

Signals derived from the microenvironment contribute greatly to tumorigenesis . The underlying mechanism requires thorough investigation. Here, we use Drosophila testis as a model system to address this question, taking the advantage of the ease to distinguish germline and somatic cells and to track the cell numbers. In an EMS mutagenesis screen, we identified Rab5, a key factor in endocytosis, for its nonautonomous role in germline proliferation. The disruption of Rab5 in somatic cyst cells, which escort the development of germline lineage, induced the overproliferation of underdifferentiated but genetically wild-type germ cells. We demonstrated that this nonautonomous effect was mediated by the transcriptional activation of Dpp [the fly homolog of bone morphogenetic protein (BMP)] by examining the Dpp-reporter expression and knocking down Dpp to block germline overgrowth. Consistently, the protein levels of Bam, the germline prodifferentiation factor normally accumulated in the absence of BMP/Dpp signaling, decreased in the overproliferating germ cells. Further, we discovered that the JNK signaling pathway operated between Rab5 and Dpp, because simultaneously inhibiting the JNK pathway and Rab5 in cyst cells prevented both dpp transcription and germline tumor growth. Additionally, we found that multiple endocytic genes, such as avl, TSG101, Vps25, or Cdc42, were required in the somatic cyst cells to restrict germline amplification. These findings indicate that when the endocytic state of the surrounding cells is impaired, genetically wild-type germ cells overgrow. This nonautonomous model of tumorigenesis provides a simple system to dissect the relation between tumor and its niche.