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Colorectal cancer (CRC) is one of the most common cancers worldwide. The tumor microenvironment exerts crucial effects in driving CRC progression. Cancer-associated fibroblasts (CAFs) serve as one of the most important tumor microenvironment components promoting CRC progression. This study aimed to elucidate the novel molecular mechanisms of CAF-secreted insulin-like growth factor (IGF) 2 in colorectal carcinogenesis. Our results indicated that IGF2 was a prominent factor upregulated in CAFs compared with normal fibroblasts. CAF-derived conditioned media (CM) promoted tumor growth, migration, and invasion of HCT 116 and DLD-1 cells. IGF1R expression is significantly increased in CRC, serving as a potent receptor in response to IGF2 stimulation and predicting unfavorable outcomes for CRC patients. Apart from the PI3K-AKT pathway, RNA-seq analysis revealed that the YAP1-target signature serves as a prominent downstream effector to mediate the oncogenic signaling of IGF2-IGF1R. By single-cell RNA sequencing (scRNA-seq) and immunohistochemical validation, IGF2 was found to be predominantly secreted by CAFs, whereas IGF1R was expressed mainly by cancer cells. IGF2 triggers the nuclear accumulation of YAP1 and upregulates YAP1 target signatures; however, these effects were abolished by either IGF1R knockdown or inhibition with picropodophyllin (PPP), an IGF1R inhibitor. Using CRC organoid and in vivo studies, we found that cotargeting IGF1R and YAP1 with PPP and verteporfin (VP), a YAP1 inhibitor, enhanced antitumor effects compared with PPP treatment alone. In conclusion, this study revealed a novel molecular mechanism by which CAFs promote CRC progression. The findings highlight the translational potential of the IGF2-IGF1R-YAP1 axis as a prognostic biomarker and therapeutic target for CRC. © 2022 The Pathological Society of Great Britain and Ireland.

Supplementary Figures and Legends

Primers used for validation the gene expression level

The interplay between gut microbiota and the host immune system is emerging as a factor in the pathogenesis of colorectal cancer. Here, we set out to identify the effect of Akkermansia muciniphila (A. muciniphila) on colorectal cancer pathogenesis. A. muciniphila abundance was significantly reduced in patients with colorectal cancer from two independent clinical cohorts and the GMrepo dataset. Supplementation with A. muciniphila suppressed colonic tumorigenesis in ApcMin/+ mice and the growth of implanted HCT116 or CT26 tumors in nude mice. Mechanistically, A. muciniphila facilitated enrichment of M1-like macrophages in an NLRP3-dependent manner in vivo and in vitro. As a consequence, NLRP3 deficiency in macrophages attenuated the tumor-suppressive effect of A. muciniphila. In addition, we revealed that TLR2 was essential for the activation of the NF-κB/NLRP3 pathway and A. muciniphila induced M1-like macrophage response. We observed positive correlations between M1-like macrophages, NLRP3/TLR2 and A. muciniphila in patients with colorectal cancer, which corroborated these findings. In summary, A. muciniphila–induced M1-like macrophages provide a therapeutic target in the colorectal cancer tumor microenvironment.

Figure S1-S8

Gene amplification is a hallmark of cancer and is frequently observed in colorectal cancer. Previous whole-genome sequencing of colorectal cancer clinical specimens identified amplification of Ring finger protein 6 (RNF6), a RING-domain E3 ubiquitin ligase. In this study, we showed that RNF6 is upregulated in 73.5% (147/200) of patients with colorectal cancer and was positively associated with RNF6 gene amplification. Furthermore, RNF6 expression and its gene amplification were independent prognostic factors for poor outcome of patients with colorectal cancer. RNF6 promoted cell growth, cell-cycle progression, and epithelial-to-mesenchymal transition in colorectal cancer cells; RNF6 also promoted colorectal tumor growth and lung metastasis in mouse models. Mechanistic investigations revealed that RNF6 bound and ubiquitylated transducin-like enhancer of split 3 (TLE3), a transcriptional repressor of the β-catenin/TCF4 complex. RNF6-mediated degradation of TLE3 significantly suppressed the association of TLE3 with TCF4/LEF, which in turn led to recruitment of β-catenin to TCF4/LEF, triggering Wnt/β-catenin activation. Restoration of TLE3 expression abolished the oncogenic effects of RNF6. Taken together, these results demonstrate that RNF6 plays a pivotal oncogenic role in colorectal tumorigenesis.Significance: RNF6-mediated ubiquitination and degradation of TLE3 activates the Wnt/β-catenin pathway in colorectal carcinogenesis. Cancer Res; 78(8); 1958–71. ©2018 AACR.

Supplementary Video S4

RNF6 up-regulates in CRC and indicates a poor outcome of CRC patients.

Supplementary Materials and Methods, Figures, Tables

Purpose:Chromosomal instability (CIN) is a common phenomenon in colorectal cancer, but its role and underlying cause remain unknown. We have identified that mitotic regulator microtubule-associated protein 9 (MAP9) is a critical regulator of CIN in colorectal cancer. We thus studied the effect of MAP9 loss on colorectal cancer in Map9-knockout mice and in cell lines.Experimental Design:We generated colon epithelial–specific Map9-knockout mice and evaluated colorectal cancer development. Effect of Map9 knockout on colorectal cancer progression was determined in chemical or ApcMin/+-induced colorectal cancer. Molecular mechanism of MAP9 was determined using spectral karyotyping, microtubule assays, and whole-genome sequencing (WGS). Clinical significance of MAP9 was examined in 141 patients with CRC.Results:Spontaneous colonic tumors (9.1%) were developed in colon epithelium–specific Map9-knockout mice at 17 months, but none was observed in wild-type littermates. Map9 deletion accelerated colorectal cancer formation both in ApcMin/+ mice and azoxymethane-treated mice, and reduced survival in ApcMin/+ mice. Mechanistically, MAP9 stabilized microtubules and mediated mitotic spindle assembly. MAP9 also maintained the spindle pole integrity and protected K-fiber from depolymerization at spindle poles. MAP9 loss induced severe mitosis failure, chromosome segregation errors, and aneuploidy, leading to transformation of normal colon epithelial cells. WGS confirmed enhanced CIN in intestinal tumors from Map9 knockout ApcMin/+ mice. In patients with colorectal cancer, MAP9 was frequently silenced and its downregulation was associated with poor survival.Conclusions:MAP9 is a microtubule stabilizer that contributes to spindle stability and inhibits colorectal tumorigenesis, supporting the role of MAP9 as a tumor suppressor for preventing CIN in colorectal cancer.

Supplementary Table S6

There remains a paucity of functional biomarkers in gastric cancer. Here, we report the identification of the sodium channel subunit SCNN1B as a candidate biomarker in gastric cancer. SCNN1B mRNA expression was silenced commonly by promoter hypermethylation in gastric cancer cell lines and primary tumor tissues. Tissue microarray analysis revealed that high expression of SCNN1B was an independent prognostic factor for longer survival in gastric cancer patients, especially those with late-stage disease. Functional studies demonstrated that SCNN1B overexpression was sufficient to suppress multiple features of cancer cell pathophysiology in vitro and in vivo. Mechanistic investigations revealed that SCNN1B interacted with the endoplasmic reticulum chaperone, GRP78, and induced its degradation via polyubiquitination, triggering the unfolded protein response (UPR) via activation of PERK, ATF4, XBP1s, and C/EBP homologous protein and leading in turn to caspase-dependent apoptosis. Accordingly, SCNN1B sensitized gastric cancer cells to the UPR-inducing drug tunicamycin. GRP78 overexpression abolished the inhibitory effect of SCNN1B on cell growth and migration, whereas GRP78 silencing aggravated growth inhibition by SCNN1B. In summary, our results identify SCNN1B as a tumor-suppressive function that triggers UPR in gastric cancer cells, with implications for its potential clinical applications as a survival biomarker in gastric cancer patients. Cancer Res; 77(8); 1968–82. ©2017 AACR.

Clinicopathological features of CRC patients

Table S1-S6

Background & Aims Hepatic immune microenvironment plays a pivotal role in the development of nonalcoholic steatohepatitis (NASH). However, the role of natural killer (NK) cells, accounting for 10%–20% of liver lymphocytes, in NASH is still unclear. In this study, we aim to investigate the functional significance of NK cells in NASH evolution. Methods NASH was induced in mice fed methionine- and choline-deficient diet (MCD), choline-deficient high-fat diet (CD-HFD), or high-fat diet with streptozotocin injection (STAM model). NK cell deficient mice (Nfil3-/-) and neutralization antibody (PK136) were used in this study. Results Activated liver NK cells were identified with increased expression of NKG2D, CD107a, and interferon-γ but decreased inhibitory NKG2A. With NK cell deficiency Nfil3-/- mice, the absence of NK cells ameliorated both MCD- and CDHF- induced NASH development with significantly decreased hepatic triglycerides, peroxides, alanine aminotransferase, and aspartate aminotransferase compared with Nfil3+/+ mice. Further molecular analysis unveiled suppressed pro-inflammatory cytokines and associated signaling. Mechanistically, NK cells isolated from NASH liver secreted higher levels of pro-inflammatory cytokines (interferon-γ, interleukin 1β, interleukin 12, CCL4, CCL5, and granulocyte-macrophage colony-stimulating factor), which could activate hepatic JAK-STAT1/3 and nuclear factor kappa B signaling and induce hepatocyte damage evidenced by elevated reactive oxygen species and apoptosis rate. Moreover, neutralization antibody PK136-dependent NK cell depletion can significantly alleviate MCD-induced steatohepatitis with suppressed cytokine levels and JAK-STAT1/3 activity. Conclusions NK cells in NASH liver are activated with a more pro-inflammatory cytokine milieu and promote NASH development via cytokine-JAK-STAT1/3 axis. Modulation of NK cells provides a potential therapeutic strategy for NASH., Graphical abstract

Backgroud: Cancer-associated fibroblasts (CAFs), a component of the tumor microenvironment, play a critical role in cancer progression, either pro- or anti-tumorigenic functions. Due to the original, phenotypic, and functional heterogeneity, CAFs can be subgrouped into several subpopulations. So far, no molecular classifications of CAFs based on a single-cell pan-cancer scale have been provided. Methods: This study employs a pan-cancer single-cell transcriptional atlas on 9 types of solid tumors (breast cancer, cholangiocarcinoma, colon adenocarcinoma, hepatocellular carcinoma, lung adenocarcinoma, neuroendocrine prostate cancer, pancreatic adenocarcinoma, prostate adenocarcinoma, and stomach adenocarcinoma) to provide a novel molecular classification, elucidate the CAF evolution. The function of each CAF subtype was analyzed by single-cell regulatory network inference and clustering (SCENIC) and single-cell GSEA, and the clinical significance was assessed using survival curves. Furthermore, we used molecular docking to screen small molecules targeting matCAF and conducted in vivo experiments to verify. Results: We distinguished CAFs in the solid tumor as 4 molecular clusters: progenitor CAF (proCAF), inflammatory CAF (iCAF), myofibroblastic CAF (myCAF), and matrix-producing CAF (matCAF) based on the prominent molecular features. The classification is universally applied in all the 9 solid tumors. The 4 CAF subtypes exhibit distinct evolutionary trajectories, functional roles, and clinical significance in different solid tumors. Besides, the matCAF signatures were found to have poor prognoses among multiple cancer types. Targeting matCAF by a screened small molecule, Procyanidin C1, exerted anti-tumor effects in suppressing tumor growth. Conclusions: Together, CAF subtypes play essential roles in cancer initiation and progression, especially mat CAF. Targeting matAF in solid tumors has tumor therapeutic potential.

Gut microorganisms can modulate response to cancer therapies. In this issue of Cancer Cell, Teng et al. trace the gut bacteria and metabolites in rectal cancer patients over the course of neoadjuvant chemoradiotherapy and identify Bacteroides vulgatus as a driver bacterium of therapeutic resistance by supplying tumors with nucleotides.

BACKGROUND AND AIM Protein O-GlcNAcylation is a critical post-translational modification regulating gene expression and fundamental cell functions. O-GlcNAc transferase (OGT) emerged as a key regulator of liver pathophysiology and disease. In this study, we aimed to evaluate the role of OGT in hepatic stellate cells (HSCs) and its consequent role in liver fibrosis. METHODS Primary HSCs were isolated from C57/B6 mice. Cell morphology and α-SMA immunofluorescence staining were observed under scanning confocal microscope. Transcriptomic profile was evaluated by RNAseq (Illumina). Promoter activity was examined by luciferase and β--Galactosidase reporter assays. Liver fibrosis mouse models were induced either by intraperitoneal injection of CCl4 at 3 times/week for 4 weeks or by feeding with methionine and choline deficient (MCD) diet for 4 weeks. RESULTS OGT protein expression and protein O-GlcNAcylation were significantly decreased in CCl4 - or MCD diet-induced liver fibrosis as compared with normal liver in mice. OGT expression and protein O-GlcNAcylation were also decreased in primary HSCs isolated from liver with CCl4 -induced fibrosis compared with those from normal liver. RNA-seq showed that OGT knockdown in HSCs modulated key signaling pathways involved in HSC activation. Promoter sequence analysis of the differentially expressed genes predicted serum response factor (SRF) as a key transcription factor regulated by OGT. Luciferase reporter assay confirmed that OGT repressed activity of SRF to induce α-SMA transcription. Mutations of specific O-GlcNAcylation sites on SRF increased its transcriptional activity, validating negative regulation of SRF by OGT-mediated O-GlcNAcylation. CONCLUSIONS Our results suggest that OGT functions as a negative regulator of HSC activation by promoting SRF O-GlcNAcylation to protect against liver fibrosis.

Ribosome biogenesis plays a pivotal role in tumorigenesis by supporting robust protein translation. We investigate the functional and molecular mechanism of Zinc finger protein 545 (ZNF545), a transcriptional repressor for ribosomal RNA (rRNA), in colorectal cancer (CRC). ZNF545 was silenced in CRC compared to adjacent normal tissues (P Znf545knockout in mice accelerated CRC inApcMin/+and azoxymethane/dextran sulfate sodium-induced CRC. Mechanistically, we demonstrated that ZNF545 uses its two zinc finger clusters to bind to minimal rDNA promoter, where it assembled transcriptional repressor complex by interacting with KAP1.Znf545deletion in mouse embryonic fibroblasts not only increased rRNA transcription rate and the nucleolar size and number but also altered the nucleolar composition and architecture with an increased number of fibrillar centers surrounded by net-like dense fibrillar components. Consequently,Znf545deletion promoted the gene expression of translation machinery, protein translation, and cell growth. Consistent with its tumor-suppressive role, ZNF545 overexpression in CRC cells induced growth arrest and apoptosis. Finally, administration of rRNA synthesis inhibitor, CX-5461, inhibited CRC development inZnf545Δ/ΔApcMin/+mice. In conclusion, ZNF545 suppresses CRC through repressing rRNA transcription and protein translation. Targeting rRNA biosynthesis in ZNF545-silenced tumors is a potential therapeutic strategy for CRC.

RNF6 is a RING finger protein with oncogenic potential. In this study, we established colon-specific RNF6 transgenic (tg) mice, and demonstrated that RNF6 overexpression accelerated colorectal carcinogenesis compared to wild-type littermates in a chemically induced colorectal cancer (CRC) model. To understand whether transcriptional activity of RNF6 underlies its oncogenic effect, we performed integrated chromatin immunoprecipitation (ChIP)-sequencing and RNA-sequencing analysis to identify splicing factor 3b subunit 2 (SF3B2) as a potential downstream target of RNF6. RNF6 binds to the SF3B2 promoter and the overexpression of RNF6 activates SF3B2 expression in CRC cells, primary CRC organoids, and RNF6 tg mice. SF3B2 knockout abrogated the tumor promoting effect of RNF6 overexpression, whereas the reexpression of SF3B2 recused cell growth and migration/invasion in RNF6 knockout cells, indicating that SF3B2 is a functional downstream target of RNF6 in CRC. Targeting of RNF6-SF3B2 axis with SF3B2 inhibitor with pladienolide B suppressed the growth of CRC cells with RNF6 overexpression in vitro and in vivo. Moreover, the combination of 5-fluorouracil (5-FU) plus pladienolide B exerted synergistic effects in CRC with high RNF6 expression, leading to tumor regression in xenograft models. These findings indicate that tumor promoting effect of RNF6 is achieved mainly via transcriptional upregulation of SF3B2, and that RNF6-SF3B2 axis is a promising target for CRC therapy.

Using whole genome sequencing, PCI Domain Containing 2 (PCID2) was identified to be amplified in colorectal cancer (CRC). In this study, we investigated the expression, biological function, molecular mechanism, and clinical implication of PCID2 in CRC. PCID2 mRNA and protein expression were higher in CRC cells and tumor tissues compared to healthy colonic tissues. The copy number of PCID2 was positively correlated with its mRNA expression. Multivariate analysis revealed that PCID2 is an independent prognostic factor for CRC recurrence. Functional studies showed that PCID2 promoted cell growth, cell cycle progression, and cell migration/invasion, while apoptosis was suppressed. Moreover, PCID2 promoted xenograft growth and lung metastasis in nude mice. Using co-immunoprecipitation and mass spectroscopy, we showed that PCID2 binds to promyelocytic leukemia (PML), a tumor suppressor involved in non-canonical β-catenin signaling. PCID2 promoted the degradation of PML via poly-ubiquitination, which in turn, induced Wnt/β-catenin signaling while simultaneously repressing ARF-p53 pathway. Thus, these results demonstrated that PCID2 functions as an oncogene in CRC by enhancing canonical Wnt/β-catenin signaling and inhibition of CTNNB1-ARF-p53 axis. PCID2 promoted canonical Wnt/β-catenin signaling in CRC via degradation of PML. PCID2 may serve as an independent prediction marker for CRC recurrence.

Cancer stem cells (CSCs) are responsible for tumor progression, recurrence, and drug resistance. To identify genetic vulnerabilities of colon cancer, we performed targeted CRISPR dropout screens comprising 657 Drugbank targets and 317 epigenetic regulators on two patient-derived colon CSC-enriched spheroids. Next-generation sequencing of pooled genomic DNAs isolated from surviving cells yielded therapeutic candidates. We unraveled 44 essential genes for colon CSC-enriched spheroids propagation, including key cholesterol biosynthetic genes (HMGCR, FDPS, and GGPS1). Cholesterol biosynthesis was induced in colon cancer tissues, especially CSC-enriched spheroids. The genetic and pharmacological inhibition of HMGCR/FDPS impaired self-renewal capacity and tumorigenic potential of the spheroid models in vitro and in vivo. Mechanistically, HMGCR or FDPS depletion impaired cancer stemness characteristics by activating TGF-β signaling, which in turn downregulated expression of inhibitors of differentiation (ID) proteins, key regulators of cancer stemness. Cholesterol and geranylgeranyl diphosphate (GGPP) rescued the growth inhibitory and signaling effect of HMGCR/FDPS blockade, implying a direct role of these metabolites in modulating stemness. Finally, cholesterol biosynthesis inhibitors and 5-FU demonstrated antitumor synergy in colon CSC-enriched spheroids, tumor organoids, and xenografts. Taken together, our study unravels novel genetic vulnerabilities of colon CSC-enriched spheroids and suggests cholesterol biosynthesis as a potential target in conjunction with traditional chemotherapy for colon cancer treatment.

The interplay between gut microbiota and the host immune system is emerging as a factor in the pathogenesis of colorectal cancer. Here, we set out to identify the effect of Akkermansia muciniphila (A. muciniphila) on colorectal cancer pathogenesis. A. muciniphila abundance was significantly reduced in patients with colorectal cancer from two independent clinical cohorts and the GMrepo dataset. Supplementation with A. muciniphila suppressed colonic tumorigenesis in ApcMin/+ mice and the growth of implanted HCT116 or CT26 tumors in nude mice. Mechanistically, A. muciniphila facilitated enrichment of M1-like macrophages in an NLRP3-dependent manner in vivo and in vitro. As a consequence, NLRP3 deficiency in macrophages attenuated the tumor-suppressive effect of A. muciniphila. In addition, we revealed that TLR2 was essential for the activation of the NF-κB/NLRP3 pathway and A. muciniphila induced M1-like macrophage response. We observed positive correlations between M1-like macrophages, NLRP3/TLR2 and A. muciniphila in patients with colorectal cancer, which corroborated these findings. In summary, A. muciniphila–induced M1-like macrophages provide a therapeutic target in the colorectal cancer tumor microenvironment.