Oncogenic KRAS creates an aspartate metabolism signature in colorectal cancer cells

Oncogenic KRAS Induces Arginine Auxotrophy and Confers a Therapeutic Vulnerability to SLC7A1 Inhibition in Non-Small Cell Lung Cancer

The urea cycle is frequently rewired in cancer cells to meet the metabolic demands of cancer. Elucidation of the underlying mechanism by which oncogenic signaling mediates urea cycle reprogramming could help identify targetable metabolic vulnerabilities. In this study, we discovered that oncogenic activation of KRAS in non-small cell lung cancer (NSCLC) silenced the expression of argininosuccinate synthase 1 (ASS1), a urea cycle enzyme that catalyzes the production of arginine from aspartate and citrulline, and thereby diverted the utilization of aspartate to pyrimidine synthesis to meet the high demand for DNA replication. Specifically, KRAS signaling facilitated a hypoacetylated state in the promoter region of the ASS1 gene in a histone deacetylase 3-dependent manner, which in turn impeded the recruitment of c-MYC for ASS1 transcription. ASS1 suppression in KRAS-mutant NSCLC cells impaired the biosynthesis of arginine and rendered a dependency on the arginine transmembrane transporter SLC7A1 to import extracellular arginine. Depletion of SLC7A1 in both patient-derived organoid and xenograft models inhibited KRAS-driven NSCLC growth. Together, these findings uncover the role of oncogenic KRAS in rewiring urea cycle metabolism and identify SLC7A1-mediated arginine uptake as a therapeutic vulnerability for treating KRAS-mutant NSCLC.

SIGNIFICANCE

ASS1 deficiency is induced by mutant KRAS in NSCLC to facilitate DNA synthesis and creates a dependency on SLC7A1, revealing dietary arginine restriction and SLC7A1 inhibition as potential therapeutic strategies.

Characteristics of amino acid metabolism in colorectal cancer

In recent years, metabolomics research has become a hot spot in the screening and treatment of cancer. It is a popular technique for the quantitative characterization of small molecular compounds in biological cells, tissues, organs or organisms. Further study of the tumor revealed that amino acid changes may occur early in the tumor. The rapid growth and metabolism required for survival result in tumors exhibiting an increased demand for amino acids. An abundant supply of amino acids is important for cancer to maintain its proliferative driving force. Changes in amino acid metabolism can be used to screen malignant tumors and improve therapeutic outcomes. Therefore, it is particularly important to study the characteristics of amino acid metabolism in colorectal cancer. This article reviews several specific amino acid metabolism characteristics in colorectal cancer.

Prognosis-related metabolic genes in the development of colorectal cancer progress and perspective

Colorectal cancer (CRC) is one of the most commonplace malignant tumors in the world. The occurrence and development of CRC are involved in numerous events. Metabolic reprogramming is one of the hallmarks of cancer and is convoluted and associated with carcinogenesis. Lots of metabolic genes are involved in the occurrence and progression of CRC. Study methods combining tumor genomics and metabolomics are more likely to explore this field in depth. In this mini-review, we make the latest progress and future prospects into the different molecular mechanisms of seven prognosis-related metabolic genes, we screened out in previous research, involved in the occurrence and development of CRC.

A novel prognostic model based on urea cycle-related gene signature for colorectal cancer

Background

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the world. This study aimed to develop a urea cycle (UC)-related gene signature that provides a theoretical foundation for the prognosis and treatment of patients with CRC.

Methods

Differentially expressed UC-related genes in CRC were confirmed using differential analysis and Venn diagrams. Univariate Cox and least absolute shrinkage and selection operator regression analyses were performed to identify UC-related prognostic genes. A UC-related signature was created and confirmed using distinct datasets. Independent prognostic predictors were authenticated using Cox analysis. The Cell-type Identification by Estimating Relative Subsets of RNA Transcripts algorithm and Spearman method were applied to probe the linkage between UC-related prognostic genes and tumor immune-infiltrating cells. The Human Protein Atlas database was used to determine the protein expression levels of prognostic genes in CRC and normal tissues. Verification of the expression levels of UC-related prognostic genes in clinical tissue samples was performed using real-time quantitative polymerase chain reaction (qPCR).

Results

A total of 49 DEUCRGs in CRC were mined. Eight prognostic genes (TIMP1, FABP4, MMP3, MMP1, CD177, CA2, S100P, and SPP1) were identified to construct a UC-related gene signature. The signature was then affirmed using an external validation set. The risk score was demonstrated to be a credible independent prognostic predictor using Cox regression analysis. Functional enrichment analysis revealed that focal adhesion, ECM-receptor interaction, IL-17 signaling pathway, and nitrogen metabolism were associated with the UC-related gene signature. Immune infiltration and correlation analyses revealed a significant correlation between UC-related prognostic genes and differential immune cells between the two risk subgroups. Finally, the qPCR results of clinical samples further confirmed the results of the public database.

Conclusion

Taken together, this study authenticated UC-related prognostic genes and developed a gene signature for the prognosis of CRC, which will be of great significance in the identification of prognostic molecular biomarkers, clinical prognosis prediction, and development of treatment strategies for patients with CRC.

Hepatocyte-Specific Knock-Out of Nfib Aggravates Hepatocellular Tumorigenesis via Enhancing Urea Cycle

Nuclear Factor I B (NFIB) has been reported to promote tumor growth, metastasis, and liver regeneration, but its mechanism in liver cancer is not fully elucidated. The present study aims to reveal the role of NFIB in hepatocellular carcinogenesis. In our study, we constructed hepatocyte-specific NFIB gene knockout mice with CRISPR/Cas9 technology (Nfib^-/-; Alb-cre), and induced liver cancer mouse model by intraperitoneal injection of DEN/CCl₄. First, we found that Nfib^-/- mice developed more tumor nodules and had heavier livers than wild-type mice. H&E staining indicated that the liver histological severity of Nfib^-/- group was more serious than that of WT group. Then we found that the differentially expressed genes in the tumor tissue between Nfib^-/- mice and wild type mice were enriched in urea cycle. Furthermore, ASS1 and CPS1, the core enzymes of the urea cycle, were significantly upregulated in Nfib^-/- tumors. Subsequently, we validated that the expression of ASS1 and CPS1 increased after knockdown of NFIB by lentivirus in normal hepatocytes and also promoted cell proliferation in vitro. In addition, ChIP assay confirmed that NFIB can bind with promoter region of both ASS1 and CPS1 gene. Our study reveals for the first time that hepatocyte-specific knock-out of Nfib aggravates hepatocellular tumor development by enhancing the urea cycle.

Biglycan as a potential regulator of tumorgenicity and immunogenicity in K-RAS-transformed cells

The extracellular matrix component biglycan (BGN) plays an essential role in various physiological and pathophysiological processes. A deficient BGN expression associated with reduced immunogenicity was found in HER-2/neu-overexpressing cells. To determine whether BGN is suppressed by oncogene-driven regulatory networks, the expression and function of BGN was analyzed in murine and human BGNlow/BGNhigh K-RASG12V-transformed model systems as well as in different patients' datasets of colorectal carcinoma (CRC) lesions. K-RAS-mutated CRC tissues expressed low BGN mRNA and protein levels when compared to normal colon epithelial cells, which was associated with a reduced patients' survival. Transfection of BGN in murine and human BGNlow K-RAS-expressing cells resulted in a reduced growth and migration of BGNhigh vs BGNlow K-RAS cells. In addition, increased MHC class I surface antigens as a consequence of an enhanced antigen processing machinery component expression was found upon restoration of BGN, which was confirmed by RNA-sequencing of BGNlow vs. BGNhigh K-RAS models. Furthermore, a reduced tumor formation of BGNhigh versus BGNlow K-RAS-transformed fibroblasts associated with an enhanced MHC class I expression and an increased frequency of tumor-infiltrating lymphocytes in tumor lesions was found. Our data provide for the first time an inverse link between BGN and K-RAS expression in murine and human K-RAS-overexpressing models and CRC lesions associated with altered growth properties, reduced immunogenicity and worse patients' outcome. Therefore, reversion of BGN might be a novel therapeutic option for K-RAS-associated malignancies.

PCK1 dysregulation in cancer: Metabolic reprogramming, oncogenic activation, and therapeutic opportunities

The last few decades have witnessed an advancement in our understanding of multiple cancer cell pathways related to metabolic reprogramming. One of the most important cancer hallmarks, including aerobic glycolysis (the Warburg effect), the central carbon pathway, and multiple-branch metabolic pathway remodeling, enables tumor growth, progression, and metastasis. Phosphoenolpyruvate carboxykinase 1 (PCK1), a key rate-limiting enzyme in gluconeogenesis, catalyzes the conversion of oxaloacetate to phosphoenolpyruvate. PCK1 expression in gluconeogenic tissues is tightly regulated during fasting. In tumor cells, PCK1 is regulated in a cell-autonomous manner rather than by hormones or nutrients in the extracellular environment. Interestingly, PCK1 has an anti-oncogenic role in gluconeogenic organs (the liver and kidneys), but a tumor-promoting role in cancers arising from non-gluconeogenic organs. Recent studies have revealed that PCK1 has metabolic and non-metabolic roles in multiple signaling networks linking metabolic and oncogenic pathways. Aberrant PCK1 expression results in the activation of oncogenic pathways, accompanied by metabolic reprogramming, to maintain tumorigenesis. In this review, we summarize the mechanisms underlying PCK1 expression and regulation, and clarify the crosstalk between aberrant PCK1 expression, metabolic rewiring, and signaling pathway activation. In addition, we highlight the clinical relevance of PCK1 and its value as a putative cancer therapeutic target.