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MicroRNA-122 overexpression suppresses the colon cancer cell proliferation by downregulating the astrocyte elevated gene-1/metadherin oncoprotein.

BACKGROUND: MicroRNAs (miRNAs) are small non-coding RNAs that regulate essential cellular functions, such as cell adhesion, proliferation, migration, invasion, and programmed cell death, and therefore, alterations in miRNAs can contribute to carcinogenesis. Previous studies have shown that miRNA-122 is abundant in the liver and regulates cell proliferation, migration, and apoptosis. However, the expression pattern and mechanism of actions of miR-122 remain primarily unknown in colon cancer. METHODS: In this study, we analyzed The Cancer Genome Atlas Colon Adenocarcinoma (TCGA-COAD) database to assess the clinical significance of astrocyte elevated gene-1 (AEG-1)/metadherin (MTDH) and miR-122 in colon cancer. MiR-122 overexpression studies were performed in HCT116, SW480, and SW620 cell lines. Dual-luciferase assay was carried out to confirm the interaction between AEG-1 and miR-122. In vivo-JetPEI-transfection reagent was used for in-vivo transient transfection of miR-122 in the AOM/DSS-induced colon tumor mouse model. RESULTS: Our results demonstrate that miR-122 was downregulated in colon cancer cells, and it influences the expressions of apoptotic factors and inflammatory cytokines. MiR-122 overexpression in HCT116, SW480, and SW620 cells showed upregulation of Caspase 3, Caspase 9, and BAX and decreased expression of BCL2, which are pro-apoptotic and anti-apoptotic members that maintain a ratio between cellular survival and cell death. In vivo transient transfection of miR-122 mimic in AOM/DSS induced colon tumor mouse model showed less inflammation and disease activity. The TCGA-COAD data indicated that AEG-1 expression was higher in patients with low expression of miR-122 and lower AEG-1 expression in patients with higher expression miR-122. CONCLUSION: Our findings highlight the key role of miR-122 in the high grade of colonic inflammation, and possibly in colon cancer, and the use of miR-122 mimic might be a therapeutic option.

MicroRNAs

Tumors hijack macrophages for iron supply to promote bone metastasis and anemia.

Bone marrow is both a primary site for hematopoiesis and a fertile niche for metastasis. The mechanism of the common occurrence of anemia among patients with bone metastasis remains poorly understood. Here, we show that a specialized population of VCAM1+CD163+CCR3+ macrophages, normally essential for erythropoiesis by transporting iron to erythroblasts, are highly enriched in the bone metastatic niche in mouse models. Tumor cells hijack these macrophages for iron supply, reducing iron availability for erythroblasts, impairing erythropoiesis, and contributing to anemia. Increased iron supply enables tumor cells to produce hemoglobin in response to hypoxia, mimicking erythroblasts. We identify macrophages with similar iron-transporting features in human bone metastases and show that elevated HBB expression correlates with increased risk of bone metastasis. These findings establish iron-transporting macrophages as an essential component of the metastatic bone niche, revealing a critical interplay between immune cells, metal metabolism, and tumor cell plasticity in driving metastasis and anemia.

Animals

Genetic and biochemical screens identify MGAT1 as a druggable glycosyltransferase target in STK11-mutant lung cancer.

Checkpoint inhibitors are standard-of-care therapies for non-small cell lung cancer (NSCLC), but their efficacy is limited in tumors with STK11 mutations, highlighting the need for new therapeutic strategies. Here, we performed complementary in vivo and in vitro CRISPR-Cas9 functional genomic screens to identify genes whose loss restores sensitivity to anti-PD-1 therapy. We found that loss of MGAT1, a Golgi glycosyltransferase critical for the maturation of high-mannose N-glycans into hybrid and complex glycan structures, reversed resistance to anti-PD-1 treatment in syngeneic mouse tumor models harboring STK11 mutations. Parallel co-culture screens with antigen-matched CD8+ T cells further showed that disruption of N-glycosylation strongly sensitized tumor cells to T cell-mediated killing. Genetic rescue studies demonstrated that this immune-evasion phenotype depends on MGAT1 catalytic activity, supporting direct biochemical interrogation of the enzyme. Using purified human MGAT1 and a UDP-Glo™ glycosyltransferase assay, we established a tractable screening platform and performed a 500,000-compound biochemical high-throughput screen, identifying an initial hit (compound 1; IC50 = 197 μM). Subsequent medicinal chemistry optimization delivered progressively more potent analogs, including TNG-9333 (0.814 μM) and TNG-2673 (0.043 μM) and represented a >1000-fold improvement in biochemical potency from the starting hit. Crystal structures of human MGAT1 in apo, UDP-bound, UDP-GlcNAc-bound, and inhibitor-bound states, together with SPR and DSF analyses, revealed that this chemical series engages a previously unrecognized allosteric pocket and inhibits MGAT1 through a UDP-noncompetitive mechanism. Collectively, our work implicates N-glycosylation as a key mediator of immune evasion and establishes MGAT1 as a ligandable, structurally tractable target for small-molecule drug discovery.

CRISPR/Cas9 target discovery

Local gene editing of fibroblasts in tumors reveals a new cancer-associated fibroblast state.

Fibroblasts play critical roles in regulating cellular relationships during tissue homeostasis, immunity, and tumor biology at multiple sites. However, tools to perturb fibroblasts at just one site in vivo are limited, restricting our understanding of how these cellular relationships act locally. We optimized local gene editing of fibroblasts in mouse tumor models to investigate how fibroblast perturbations affect the tumor microenvironment (TME). By knocking out receptors Osmr, Tgfbr2, or Il1r1 on cancer-associated fibroblasts (CAFs), we uncover that TGFBR2 signaling loss induces the emergence of a new Col18a1hi CAF cell state that is associated with worse survival in pancreatic cancer patients. Combinatorial gene KOs in CAFs reveals a circuit where these Col18a1hi CAFs reshape the TME by recruiting Siglec-Fhi neutrophils via Cxcl5 expression, and where this Col18a1hi CAF cell state is dependent on TNFR1 and canonical Wnt signaling. Together, a fast, affordable, and modular engineering method is demonstrated, allowing discovery of modified fibroblast identities and local intercellular relationships in the TME.

Animals

Discovery of a Linked Constellation of Gene Expression Revealed by Local Editing of Fibroblasts in Tumors.

Fibroblasts play critical roles in regulating cellular relationships during tissue homeostasis, immunity, and tumor biology at multiple sites. However, tools to perturb fibroblasts at just one site in vivo are limited, restricting our understanding of how these cellular relationships develop on a local level. We optimized local gene editing of fibroblasts in multiple mouse tumor models to investigate how locally restricted fibroblast perturbations affect the cellular tumor microenvironment (TME). By knocking out surface receptors Osmr, Tgfbr2, or Il1r1 on cancer-associated fibroblasts (CAFs), we uncover that TGFBR2 signaling loss uniquely induces the emergence of a Col18a1 hi CAF cell state that is distinct from previously described fibroblast states and is associated with worse survival in human PDAC patients. Further application of a local as well as combinatorial gene knockout technology in CAFs reveals a circuit in which these Col18a1 hi CAFs reshape the TME by recruiting Siglec-Fhi neutrophils via Cxcl5 expression; and that the Col18a1 hi CAF cell state is further dependent on TNFR1 and canonical Wnt signaling. Together, a fast, affordable, and modular engineering method is demonstrated, allowing discovery of a modified fibroblast identify, as well as the network details of a local inter-cellular circuitry in a tumor.

Journal Article

Kinetic models of C3H mouse mammary tumor growth: implications regarding tumor cell loss.

Three models of tumor cell loss are described. The effects of cell loss on other cellular kinetic parameters are evaluated, and experiments which may distinguish among the models are discussed. Each model is based on a different cell-loss mechanism, and equations for the cell-cycle, cell-frequency distribution, the growth of both the proliferating and non-proliferating cell population, the growth fraction (GF), and the relative rate of volumetric growth, (dV/dt)/V, are derived. The following types of data are simulated for each model: the pulse labelling index, the mitotic index, and the labeling index as a function of time after a single or a series of 3H-TdR injections. The relative volumetric growth rate has the same mathematical form for each model. The PLM curves predicted by each model for the tumor lines studied (S102F and Slow) are not appreciably different. The predicted initial labeling index and mitotic index may differ significantly among the models depending upon the tumor line. The most striking difference among the models lies in the predictions regarding the labeling index as a function of time after a single or after a series of 3H-TdR injections. These types of labeling experiments should be valuable for distinguishing the different cell-loss mechanisms in solid tumors.

Animals

Estrogen-induced Leydig cell tumor in the mouse: a model system for the study of carcinogenesis and hormone dependency.

Malignant neoplasms of endocrine tissues represent almost half of the cancers diagnosed clinically in the United States, and many of these respond to hormonal therapies. Estrogen-induced testicular Leydig cell tumors in the mouse would seem to represent a realistic model for the laboratory investigation of this significant group of cancers. Data accumulated over the past few years clearly show that the Leydig cell is a target tissue for estrogens. Administering large doses of estrogen results in a reduction of enzymes converting progesterone to testosterone and induces a transient, but quantitatively very significant, synthesis of DNA in the Leydig cells of tumor-susceptible strains of mice. Neither of these actions of estrogen is mediated via the hypophysis. It has been demonstrated that the Leydig cells have specific protein receptors in their cytoplasm that bind estrogens and transport them to the nucleus where they are also bound. The genetic composition of the Leydig cells themselves is extremely important for the development of tumors. An adequately functioning pituitary gland is also essential for tumor formation. Confining the testes to the abdomen results in enzyme changes similar to those produced by estrogen administration and significantly augments the development of Leydig cell tumors. Once tumors form they frequently are dependent for their continued growth on estrogenic stimulation and/or on a functioning hypothysis. Regressed tumors may remain dormant for many months only to resume progressive growth when placed in and adequate hormone environment.

Animals

Plasma levels of a viral protein as a diagnostic signal for the presence of tumor : the murine mammary tumor model.

We used the mouse mammary tumor and its associated virus (murine mammary tumor virus) to examine the possibility of using plasma levels of a viral protein (gp52, the glycoprotein of 52,000 molecular weight) as a diagnostic indicator of the presence of a solid tumor. The following features have emerged from our studies: (a) tumor-bearing animals show markedly elevated (100-1000 ng/ml) plasma levels of gp52 and the mean concentration increases with tumor size; (b) mammary tumor tissues located outside the mammary gland are also detected by the elevated plasma gp52; (c) low (2-10 ng/ml) plasma levels of gp52 are found in tumor-free mice, whether they are derived from strains characterized by high or low frequencies of spontaneous mammary tumors; (d) tumor-free lactating females exhibit the normally low levels of plasma gp52 despite the fact that their milk contains an average of 20,000 ng/ml of this antigen; (e) thus, high levels of plasma gp52 are found only in the presence of tumor and are not induced by either predisposition for the disease or by normal production of the antigen during lactation; (f) the circulatory clearance time of gp52 is sufficiently rapid to require continued replenishment to maintain the high levels observed in tumor-bearing animals, a feature implying that the gp52 concentration can be a responsive parameter of disease status. The information obtained suggests that plasma gp52 is a potentially useful and specific systemic indicator of the presence and extent of murine mammary neoplasia.

Animals

A tumorigenesis threshold for endogenous Myc revealed by dosage-compensation for Myc-haploinsufficiency in the absence of p53.

The MYC proto-oncogene is crucial for neoplasia in most tumors. Overexpressed, oncogenic MYC amplifies the flux through most major processes but does not specify a unique carcinogenic pathway. This "amplifier" model suggests that MYC must exceed an expression threshold to become oncogenic. We designed a genetic test of this model, using the mouse Trp53 null mutant (p53KO) as a highly robust tumor generator to examine the effect of a modest change in the endogenous Myc level (Myc +/-). Strikingly, tumor-free survival is greatly extended in p53KO mice with haploid Myc gene-dosage, yet in the tumors that do develop (mainly hemangiosarcomas and thymic lymphomas), their Myc deficit has been invariably compensated either by increasing Myc genomic dosage (hemangiosarcomas) or expression (lymphomas). Furthermore, acutely halving the endogenous Myc gene-dosage in established tumor allografts curtails growth rates. These results indicate that even an incremental reduction of MYC activity can be salutary in cancer and that one of the major tumor suppressor functions of p53 derives from its ability to prevent MYC overexpression. Myc generates acute DNA damage by several mechanisms and accordingly, p53's anti-Myc function may be inextricably linked to its role in genome integrity surveillance.

Myc haplo-insufficiency

Brain tumor-scanning agents compared in an animal model.

Sixteen radiopharmaceuticals for brain tumor localization have been compared in a mouse brain tumor model. A rating system is presented for such intercomparison. The rusults indicate that 111-in-chloride injected at pH 1.5 has the most favorable biologic characterisTICS FOR BRAIN TUMOR IMAGING.

Animals

Mouse mammary tumor virus as a model for viral carcinogenesis.

Evidence is presented suggesting that genetic control may be the limiting factor in mammary tumor virus (MTV) positive mammary oncogenesis. Studies with hybrid mice involving high and low MTV-expressing murine strains suggest that expression of MTV in milk may not be as important in tumorigenesis as previously thought. The usefulness of the murine MTV model in the study of mammary malignancy is discussed.

Animals

Patrolling monocytes control tumor metastasis to the lung.

The immune system plays an important role in regulating tumor growth and metastasis. Classical monocytes promote tumorigenesis and cancer metastasis, but how nonclassical "patrolling" monocytes (PMo) interact with tumors is unknown. Here we show that PMo are enriched in the microvasculature of the lung and reduce tumor metastasis to lung in multiple mouse metastatic tumor models. Nr4a1-deficient mice, which specifically lack PMo, showed increased lung metastasis in vivo. Transfer of Nr4a1-proficient PMo into Nr4a1-deficient mice prevented tumor invasion in the lung. PMo established early interactions with metastasizing tumor cells, scavenged tumor material from the lung vasculature, and promoted natural killer cell recruitment and activation. Thus, PMo contribute to cancer immunosurveillance and may be targets for cancer immunotherapy.

Animals

LARS promotes hepatocellular carcinoma progression via the PI3K/AKT/mTOR pathway and interaction with RPS5, and serves as a prognostic biomarker.

BACKGROUND: Hepatocellular carcinoma (HCC) caused many cancer deaths around the world. Its progression involves complex mechanisms, creating an urgent need to identify new therapeutic targets. Leucine-tRNA synthetase (LARS) is a key enzyme for protein synthesis, but its specific role and mechanism in HCC are not well understood. PURPOSE: This research aims to investigate the biological function, molecular mechanism, and clinical relevance of the LARS gene in HCC progression, to assess its potential as a treatment target. METHODS: LARS expression was assessed in HCC cell lines (PLC-PRF-5, HCC-LM3) and in mouse subcutaneous tumor models using siRNA and adeno-associated virus (AAV). Techniques including Cell Counting Kit-8(CCK-8), colony formation, EdU, Transwell, wound healing, and flow cytometry were used to measure cell proliferation, migration, invasion, and apoptosis. RNA-seq, proteomics (TMT), western blot, co-immunoprecipitation (Co-IP) with mass spectrometry, molecular docking, and molecular dynamics simulation were employed to study the affected signaling pathway (PI3K/AKT/mTOR) and interacting protein (RPS5). The TCGA (The Cancer Genome Atlas) database and UALCAN platform were used to analyze links between LARS expression and clinicopathological features or prognosis in HCC patients. RESULTS: Reducing LARS expression significantly inhibited the proliferation, colony formation, migration, and invasion of HCC cells, while promoting apoptosis. In mice, LARS knockdown markedly slowed tumor growth. Mechanistic studies showed that reducing LARS expression levels affected the PI3K/AKT/mTOR signaling pathway and led to decreased levels of the key interacting protein RPS5. Overexpressing RPS5 partly reversed the proliferation inhibition caused by LARS depletion. Molecular docking and dynamics simulations suggested that the environmental contaminant triphenyl phosphate (TPP) might bind to the LARS protein. Clinical data analysis revealed that LARS expression is higher in HCC tissues. High LARS expression was significantly associated with shorter overall survival (OS) in patients and correlated positively with various clinical features like tumor stage, grade, and TP53 mutation status. CONCLUSION: LARS helped HCC become worse by affecting the PI3K/AKT/mTOR pathway and working with RPS5. High LARS meant a worse outcome for patients. This suggested LARS could be used to predict disease or as a treatment target in HCC.

Carcinoma, Hepatocellular

Evaluation of a "nude" mouse-human tumor panel as a predictive secondary screen for cancer chemotherapeutic agents.

Nine established human melanoma tissue-cultured cell lines heterotransplanted in C57BL/6 "nude" mice were exposed to each of 4 chemotherapeutic agents of known clinical activity against human melanoma. Two of the therapeutic agents, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 5-(3,3-dimethyl-1-triazino) imidazole-4-carboxamide (DTIC), are known to be active against human melanoma; the other two, adriamycin and 5-azacytidine, are known to be inactive. Sterile saline served as a control agent. In 2 cell line heterotransplants, the control tumor spontaneously regressed. Of the 7 cell lines that remained for evaluation, 4 were sensitive to DTIC, 1 was sensitive to BCNU, and none was sensitive to adriamycin or 5-azacytidine. These data indicate that the nude mouse-human tumor model may be a predictive secondary screen for cancer chemotherapeutic agents.

Animals

Propionyl-CoA carboxylase subunit B regulates anti-tumor T cells in a pancreatic cancer mouse model.

Most human pancreatic ductal adenocarcinoma (PDAC) are not infiltrated with cytotoxic T cells and are highly resistant to immunotherapy. Over 90% of PDAC have oncogenic KRAS mutations, and phosphoinositide 3-kinases (PI3Ks) are direct effectors of KRAS. Our previous study demonstrated that ablation of Pik3ca in KPC (KrasG12D; Trp53R172H; Pdx1-Cre) pancreatic cancer cells induced host T cells to infiltrate and completely eliminate the tumors in a syngeneic orthotopic implantation mouse model. Now, we show that implantation of Pik3ca-/- KPC (named αKO) cancer cells induces clonal enrichment of cytotoxic T cells infiltrating the pancreatic tumors. To identify potential molecules that can regulate the activity of these anti-tumor T cells, we conducted an in vivo genome-wide gene-deletion screen using αKO cells implanted in the mouse pancreas. The result shows that deletion of propionyl-CoA carboxylase subunit B gene (Pccb) in αKO cells (named p-αKO) leads to immune evasion, tumor progression, and death of host mice. Surprisingly, p-αKO tumors are still infiltrated with clonally enriched CD8+ T cells but they are inactive against tumor cells. However, blockade of PD-L1/PD1 interaction reactivated these clonally enriched T cells infiltrating p-αKO tumors, leading to slower tumor progression and improve survival of host mice. These results indicate that Pccb can modulate the activity of cytotoxic T cells infiltrating some pancreatic cancers and this understanding may lead to improvement in immunotherapy for this difficult-to-treat cancer.

Animals

Development of a new flippase-dependent mouse model for red fluorescence-based isolation of KRASG12D oncogene-expressing tumor cells.

Proto-oncogene KRAS, GTPase (KRAS) is one of the most intensively studied oncogenes in cancer research. Although several mouse models allow for regulated expression of mutant KRAS, selective isolation and analysis of transforming or tumor cells that produce the KRAS oncogene remains a challenge. In our study, we present a knock-in model of oncogenic variant KRASG12D that enables the "activation" of KRASG12D expression together with production of red fluorescent protein tdTomato. Both proteins are expressed from the endogenous Kras locus after recombination of a transcriptional stop box in the genomic DNA by the enzyme flippase (Flp). We have demonstrated the functionality of the allele termed RedRas (abbreviated KrasRR) under in vitro conditions with mouse embryonic fibroblasts and organoids and in vivo in the lung and colon epithelium. After recombination with adenoviral vectors carrying the Flp gene, the KrasRR allele itself triggers formation of lung adenomas. In the colon epithelium, it causes the progression of adenomas that are triggered by the loss of tumor suppressor adenomatous polyposis coli (APC). Importantly, cells in which recombination has successfully occurred can be visualized and isolated using the fluorescence emitted by tdTomato. Furthermore, we show that KRASG12D production enables intestinal organoid growth independent of epidermal growth factor (EGF) signaling and that the KRASG12D function is effectively suppressed by specific inhibitor MRTX1133.

Animals

Exogenous BMI1 expression aggravates oral squamous cell carcinomas in tongue epithelia.

Oral squamous cell carcinoma (OSCC) is characterized by aggressiveness and a poor prognosis, in part because most patients are diagnosed during the later stages of the disease. B cell-specific Moloney murine leukemia virus integration site 1 (BMI1), part of polycomb repressive complex 1 (PRC1), is a key transcription factor overexpressed in OSCC. Although increased BMI1 has been linked to tumor formation in mouse models of the disease, the molecular mechanisms have not been elucidated. Here we used a transgenic mouse line (KrTB) that selectively overexpresses BMI1 in the tongue basal epithelial stem cells (SCs) to delineate BMI1 actions during oral tumorigenesis. By tumor pathological classification after 4-nitroquinoline 1-oxide (4-NQO)-induced carcinogenesis we detected more severe tumors in mice with ectopic BMI1 expression. Genome-wide transcriptomics indicated that mRNAs associated with human OSCC, including SOX9, HIF1A, MMP9, INHBB, and MYOF, were further increased by ectopic BMI1 expression in murine tongue epithelia. mRNAs encoding multiple metabolic targets, such as SLC2A1 (GLUT1), PKM, LDHA, and HK2, were also increased upon BMI1 overexpression in 4-NQO-treated tongue epithelia. Furthermore, we detected BMI1, SOX9, and GLUT1 proteins in the infiltrating cells of invasion fronts identified by markers of invasive SCCs. Finally, metabolomic data show that BMI1 overexpression in tongue epithelia promotes glycolysis during 4-NQO-induced carcinogenesis. Thus, our data demonstrate that BMI1 causes OSCC cells to alter cell metabolism, as changes in many of these transcripts are linked to increased glycolysis and metabolic reprograming that occurs during carcinogenesis.

Animals