Wnt signaling directs a metabolic program of glycolysis and angiogenesis in colon cancer

Much of the mechanism by which Wnt signaling drives proliferation during oncogenesis is attributed to its regulation of the cell cycle. Here, we show how Wnt/β‐catenin signaling directs another hallmark of tumorigenesis, namely Warburg metabolism. Using biochemical assays and fluorescence lifetime imaging microscopy (FLIM) to probe metabolism in vitro and in living tumors, we observe that interference with Wnt signaling in colon cancer cells reduces glycolytic metabolism and results in small, poorly perfused tumors. We identify pyruvate dehydrogenase kinase 1 (PDK1) as an important direct target within a larger gene program for metabolism. PDK1 inhibits pyruvate flux to mitochondrial respiration and a rescue of its expression in Wnt‐inhibited cancer cells rescues glycolysis as well as vessel growth in the tumor microenvironment. Thus, we identify an important mechanism by which Wnt‐driven Warburg metabolism directs the use of glucose for cancer cell proliferation and links it to vessel delivery of oxygen and nutrients.     

Metabolic pattern formation in the tumor microenvironment

Metabolic alterations including increased glycolysis are a common feature of many cancers. In their recent study, Lowengrub, Waterman, and colleagues (Lee et al, 2017 ) report a spatial pattern of glycolysis in solid tumors that occurs within the tumor microenvironment. This spatial organization is linked to gradients derived from Wnt signaling and nutrient availability that mediate a reaction‐diffusion mechanism and is consistent with a Turing‐type model of spatial localization.     

Mitophagy protein PINK1 suppresses colon tumor growth by metabolic reprogramming via p53 activation and reducing acetyl-CoA production

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths in the US. Understanding the mechanisms of CRC progression is essential to improve treatment. Mitochondria is the powerhouse for healthy cells. However, in tumor cells, less energy is produced by the mitochondria and metabolic reprogramming is an early hallmark of cancer. The metabolic differences between normal and cancer cells are being interrogated to uncover new therapeutic approaches. Mitochondria targeting PTEN-induced kinase 1 (PINK1) is a key regulator of mitophagy, the selective elimination of damaged mitochondria by autophagy. Defective mitophagy is increasingly associated with various diseases including CRC. However, a significant gap exists in our understanding of how PINK1-dependent mitophagy participates in the metabolic regulation of CRC. By mining Oncomine, we found that PINK1 expression was downregulated in human CRC tissues compared to normal colons. Moreover, disruption of PINK1 increased colon tumorigenesis in two colitis-associated CRC mouse models, suggesting that PINK1 functions as a tumor suppressor in CRC. PINK1 overexpression in murine colon tumor cells promoted mitophagy, decreased glycolysis and increased mitochondrial respiration potentially via activation of p53 signaling pathways. In contrast, PINK1 deletion decreased apoptosis, increased glycolysis, and reduced mitochondrial respiration and p53 signaling. Interestingly, PINK1 overexpression in vivo increased apoptotic cell death and suppressed colon tumor xenograft growth. Metabolomic analysis revealed that acetyl-CoA was significantly reduced in tumors with PINK1 overexpression, which was partly due to activation of the HIF-1α-pyruvate dehydrogenase (PDH) kinase 1 (PDHK1)-PDHE1α axis. Strikingly, treating mice with acetate increased acetyl-CoA levels and rescued PINK1-suppressed tumor growth. Importantly, PINK1 disruption simultaneously increased xenografted tumor growth and acetyl-CoA production. In conclusion, mitophagy protein PINK1 suppresses colon tumor growth by metabolic reprogramming and reducing acetyl-CoA production.Subject terms: Tumour-suppressor proteins, Cancer metabolism     

LINC00261 suppresses human colon cancer progression via sponging miR-324-3p and inactivating the Wnt/β-catenin pathway

Growing evidence indicates long noncoding RNAs (lncRNAs) are significant regulators in the progression of various malignant tumors including colon cancer. Dysregulation of lncRNA LINC00261 has been identified in many cancers. Investigations on LINC00261 function have revealed that LINC00261 could act as a crucial tumor suppressor in various cancers. But, the biological involvement of LINC00261 in colon cancer is still barely known. Here, we found LINC00261 was reduced in colon cancer cells. Meanwhile, overexpressed LINC00261 repressed colon cancer cell viability and proliferation capacity. In addition, colony cancer cell colony formation was inhibited and apoptosis was enhanced by upregulation of LINC00261. Also, colon cancer cell migration and invasion both were restrained by LINC00261. miR-324-3p can exert important functions in several carcinomas, but its role in colon cancer is uninvestigated. In the current study, miR-324-3p was examined and miR-324-3p was greatly increased in colon cancer cells. Moreover, the association between miR-324-3p and LINC00261 was confirmed via performing RNA immunoprecipitation and RNA-pull-down experiments. In cancer biology, aberrant modulation of the Wnt signaling pathway remains a prevalent theme. Overexpression of LINC00261 obviously impaired colon cancer progression via inactivating the Wnt pathway. Furthermore, in the xenograft model assay, an increase of LINC00261 could suppress colon tumor growth via sponging miR-324-3p and inactivating the Wnt pathway. Overall, our results showed that LINC00261 repressed colon cancer progression via regulating miR-324-3p and the Wnt pathway. LINC00261 could be established as a novel therapeutic target for colon cancer.     

Cancer: leaping the E‐cadherin hurdle

Aberrant activation of the Wnt signaling pathway is a common cause of colon cancer and other tumor types, accomplishing many of the hallmarks of cancer including sustained proliferative signaling, replicative immortality, reprogrammed metabolism, angiogenesis, and invasion. Yet, the dominant mutation that leads to chronic Wnt signaling in colon cancer is quite different from the spectrum of mutations that activate Wnt signaling in other tumor types. In this issue of The EMBO Journal, Huels et al ( 2015 ) focus on the influential role E‐cadherin plays in shaping these differences.     

Pyruvate kinase type M2 is upregulated in colorectal cancer and promotes proliferation and migration of colon cancer cells

Pyruvate kinase type M2 (PKM2) has been reported to be involved in aerobic glycolysis and cell growth in various tumors. However, the expression pattern of PKM2 in colorectal cancer (CRC) and the correlation between PKM2 expression and CRC remains unclear. The aim of this study is to investigate PKM2 expression and its possible role in CRC. We found that expression of PKM2 was increased in CRC and the increased PKM2 expression was associated with later stage and lymph metastasis of the tumors. Knockdown of PKM2 suppressed the aerobic glycolysis and decreased lactate production of colon cancer RKO cells. Knockdown of PKM2 repressed proliferation and migration of the cells. Inhibition of PKM2 suppressed xenograft tumor growth of RKO cells in vivo. These results suggest that the expression of PKM2 plays a critical role in development of CRC, and it may provide a growth advantage for colon cancer cells. Thus, PKM2 might be a potential therapeutic target for CRC. ? 2012 IUBMB Life, 64(9): 775-782, 2012.     

Metabolic reprogramming in colon cancer reversed by DHTS through regulating PTEN/AKT/HIF1α mediated signal pathway

Background

Metabolic reprogramming and hypoxia contribute to the resistance of conventional chemotherapeutic drugs in kinds of cancers. In this study, we investigated the effect of dihydrotanshinone I (DHTS) on reversing dysregulated metabolism of glucose and fatty acid in colon cancer and elucidated its mechanism of action.

The Wnt connection to tumorigenesis

Wnt signaling has been identified as one of the key signaling pathways in cancer, regulating cell growth, motility and differentiation. Because of its widespread activation in diverse human tumor diseases, the Wnt pathway has gained considerable and growing interest in tumor research over recent years. Evidence that altered Wnt signaling is important for human tumor development came from three major findings: (i) the tumor suppressor adenomatous polyposis coli (APC) binds to the Wnt pathway component beta-catenin and is involved in its degradation, (ii) mutations of APC in colon tumors lead to stabilization of the beta-catenin protein and (iii) tumor-associated mutations of beta-catenin in colorectal cancer as well as in other tumor types lead to its stabilisation, qualifying beta-catenin as a proto-oncogene. Here we will describe the biochemical interactions which shape the Wnt pathway and focus on its role in tumorigenesis.     

Metabolic reprogramming of cancer-associated fibroblasts by TGF-β drives tumor growth: Connecting TGF-β signaling with “Warburg-like” cancer metabolism and L-lactate production

We have previously shown that a loss of stromal Cav-1 is a biomarker of poor prognosis in breast cancers. Mechanistically, a loss of Cav-1 induces the metabolic reprogramming of stromal cells, with increased autophagy/mitophagy, mitochondrial dysfunction and aerobic glycolysis. As a consequence, Cav-1-low CAFs generate nutrients (such as L-lactate) and chemical building blocks that fuel mitochondrial metabolism and the anabolic growth of adjacent breast cancer cells. It is also known that a loss of Cav-1 is associated with hyperactive TGF-β signaling. However, it remains unknown whether hyperactivation of the TGF-β signaling pathway contributes to the metabolic reprogramming of Cav-1-low CAFs. To address these issues, we overexpressed TGF-β ligands and the TGF-β receptor I (TGFβ-RI) in stromal fibroblasts and breast cancer cells. Here, we show that the role of TGF-β in tumorigenesis is compartment-specific, and that TGF-β promotes tumorigenesis by shifting cancer-associated fibroblasts toward catabolic metabolism. Importantly, the tumor-promoting effects of TGF-β are independent of the cell type generating TGF-β. Thus, stromal-derived TGF-β activates signaling in stromal cells in an autocrine fashion, leading to fibroblast activation, as judged by increased expression of myofibroblast markers, and metabolic reprogramming, with a shift toward catabolic metabolism and oxidative stress. We also show that TGF-β-activated fibroblasts promote the mitochondrial activity of adjacent cancer cells, and in a xenograft model, enhancing the growth of breast cancer cells, independently of angiogenesis. Conversely, activation of the TGF-β pathway in cancer cells does not influence tumor growth, but cancer cell-derived-TGF-β ligands affect stromal cells in a paracrine fashion, leading to fibroblast activation and enhanced tumor growth. In conclusion, ligand-dependent or cell-autonomous activation of the TGF-β pathway in stromal cells induces their metabolic reprogramming, with increased oxidative stress, autophagy/mitophagy and glycolysis, and downregulation of Cav-1. These metabolic alterations can spread among neighboring fibroblasts and greatly sustain the growth of breast cancer cells. Our data provide novel insights into the role of the TGF-β pathway in breast tumorigenesis, and establish a clear causative link between the tumor-promoting effects of TGF-β signaling and the metabolic reprogramming of the tumor microenvironment.     

Network quantification of EGFR signaling unveils potential for targeted combination therapy

The epidermal growth factor receptor (EGFR) signaling network is activated in most solid tumors, and small‐molecule drugs targeting this network are increasingly available. However, often only specific combinations of inhibitors are effective. Therefore, the prediction of potent combinatorial treatments is a major challenge in targeted cancer therapy. In this study, we demonstrate how a model‐based evaluation of signaling data can assist in finding the most suitable treatment combination. We generated a perturbation data set by monitoring the response of RAS/PI3K signaling to combined stimulations and inhibitions in a panel of colorectal cancer cell lines, which we analyzed using mathematical models. We detected that a negative feedback involving EGFR mediates strong cross talk from ERK to AKT. Consequently, when inhibiting MAPK, AKT activity is increased in an EGFR‐dependent manner. Using the model, we predict that in contrast to single inhibition, combined inactivation of MEK and EGFR could inactivate both endpoints of RAS, ERK and AKT. We further could demonstrate that this combination blocked cell growth in BRAF‐ as well as KRAS‐mutated tumor cells, which we confirmed using a xenograft model.     

Pyruvate dehydrogenase kinase 1 contributes to cisplatin resistance of ovarian cancer through EGFR activation

Patients with ovarian cancer frequently develop acquired drug resistance after the long-term chemotherapy, leading to disease progression. Enhanced epithelial–mesenchymal transition (EMT) has been implicated in chemoresistance of ovarian cancer cells; however, the molecular mechanisms involved are largely undefined. Pyruvate dehydrogenase kinase 1 (PDK1), a key regulatory enzyme in glucose metabolism, has been recognized as a gatekeeper of the Warburg effect, a hallmark of cancer. In this study, the function of PDK1 in cisplatin resistance of ovarian cancer in terms of growth and EMT was investigated. PDK1 was upregulated in cisplatin-resistant ovarian cancer cells. PDK1 knockdown in resistant cells led to increased sensitivity to cisplatin-induced cell death and apoptosis. PDK1 downregulation also reversed the EMT and cell motility in cisplatin-resistant cells. In a mouse xenograft model, tumors derived from PDK1-silenced ovarian cancer cells exhibited decreased tumor growth and EMT compared with control after the cisplatin treatment. Mechanistically, PDK1 overexpression led to increased phosphorylation of EGFR, and blocking EGFR kinase activity by erlotinib reversed cisplatin resistance induced by PDK1 overexpression. Furthermore, in patients with ovarian cancer, higher PDK1 and p-EGFR levels were associated with chemoresistance. These results supported that PDK1 contributes to chemoresistance of ovarian cancer by activating EGFR. Therefore, PDK1 may serve as a promising target to combat chemoresistance of ovarian cancer.     

Metabolic reprogramming of cancer-associated fibroblasts by TGF-β drives tumor growth: Connecting TGF-β signaling with “Warburg-like” cancer metabolism and L-lactate production

We have previously shown that a loss of stromal Cav-1 is a biomarker of poor prognosis in breast cancers. Mechanistically, a loss of Cav-1 induces the metabolic reprogramming of stromal cells, with increased autophagy/mitophagy, mitochondrial dysfunction and aerobic glycolysis. As a consequence, Cav-1-low CAFs generate nutrients (such as L-lactate) and chemical building blocks that fuel mitochondrial metabolism and the anabolic growth of adjacent breast cancer cells. It is also known that a loss of Cav-1 is associated with hyperactive TGF-β signaling. However, it remains unknown whether hyperactivation of the TGF-β signaling pathway contributes to the metabolic reprogramming of Cav-1-low CAFs. To address these issues, we overexpressed TGF-β ligands and the TGF-β receptor I (TGFβ-RI) in stromal fibroblasts and breast cancer cells. Here, we show that the role of TGF-β in tumorigenesis is compartment-specific, and that TGF-β promotes tumorigenesis by shifting cancer-associated fibroblasts toward catabolic metabolism. Importantly, the tumor-promoting effects of TGF-β are independent of the cell type generating TGF-β. Thus, stromal-derived TGF-β activates signaling in stromal cells in an autocrine fashion, leading to fibroblast activation, as judged by increased expression of myofibroblast markers, and metabolic reprogramming, with a shift toward catabolic metabolism and oxidative stress. We also show that TGF-β-activated fibroblasts promote the mitochondrial activity of adjacent cancer cells, and in a xenograft model, enhancing the growth of breast cancer cells, independently of angiogenesis. Conversely, activation of the TGF-β pathway in cancer cells does not influence tumor growth, but cancer cell-derived-TGF-β ligands affect stromal cells in a paracrine fashion, leading to fibroblast activation and enhanced tumor growth. In conclusion, ligand-dependent or cell-autonomous activation of the TGF-β pathway in stromal cells induces their metabolic reprogramming, with increased oxidative stress, autophagy/mitophagy and glycolysis, and downregulation of Cav-1. These metabolic alterations can spread among neighboring fibroblasts and greatly sustain the growth of breast cancer cells. Our data provide novel insights into the role of the TGF-β pathway in breast tumorigenesis, and establish a clear causative link between the tumor-promoting effects of TGF-β signaling and the metabolic reprogramming of the tumor microenvironment.     

飞燕草素通过Wnt/β-catenin信号通路抑制乳腺癌的机制研究

为研究飞燕草素对乳腺癌MDA-MB-231细胞Wnt/β-catenin信号通路的影响。免疫组化检测裸鼠乳腺肿瘤组织和肺组织转移瘤Ki-67及乳腺肿瘤组织蛋白水解酶超家族基质金属蛋白酶-7(matrix metallopeptidase 7,MMP-7)的表达水平;Western blot检测移植瘤Wnt/β-catenin通路β-联蛋白(β-catenin)、磷酸糖原合成酶激酶-3β(glycogen synthase kinase-3β,GSK-3β)及通路下游细胞周期相关蛋白cyclinD1、原癌基因c-myc和MMP-7的蛋白水平表达,体内外实验发现飞燕草素不仅能抑制裸鼠异种移植瘤生长及乳腺癌肿瘤组织和肺组织转移瘤Ki-67表达还可以明显降低乳腺癌MDA-MB-231细胞Wnt/β-catenin信号通路β-catenin和p-GSK-3β下游靶基因c-myc、cyclin D1和MMP-7蛋白的表达。本研究证实飞燕草素能通过抑制Wnt/β-catenin信号通路,发挥抑制乳腺癌的作用。     

Mitochondrial dysfunction induces radioresistance in colorectal cancer by activating [Ca2+]m-PDP1-PDH-histone acetylation retrograde signaling

Mitochondrial retrograde signaling (mito-RTG) triggered by mitochondrial dysfunction plays a potential role in regulating tumor metabolic reprogramming and cellular sensitivity to radiation. Our previous studies showed phos-pyruvate dehydrogenase (p-PDH) and PDK1, which involved in aerobic glycolysis, were positively correlated with radioresistance, but how they initiate and work in the mito-RTG pathway is still unknown. Our further genomics analysis revealed that complex I components were widely downregulated in mitochondrial dysfunction model. In the present study, high expression of p-PDH was found in the complex I deficient cells and induced radioresistance. Mechanistically, complex I defects led to a decreased PDH both in cytoplasm and nucleus through [Ca²⁺]_m-PDP1-PDH axis, and decreased PDH in nucleus promote DNA damage repair (DDR) response via reducing histone acetylation. Meanwhile, NDUFS1 (an important component of the complex I) overexpression could enhance the complex I activity, reverse glycolysis and resensitize cancer cells to radiation in vivo and in vitro. Furthermore, low NDUFS1 and PDH expression were validated to be correlated with poor tumor regression grading (TRG) in local advanced colorectal cancer (CRC) patients underwent neoadjuvant radiotherapy. Here, we propose that the [Ca²⁺]_m-PDP1-PDH-histone acetylation retrograde signaling activated by mitochondrial complex I defects contribute to cancer cell radioresistance, which provides new insight in the understanding of the mito-RTG. For the first time, we reveal that NDUFS1 could be served as a promising predictor of radiosensitivity and modification of complex I function may improve clinical benefits of radiotherapy in CRC.Subject terms: Cancer metabolism, Radiotherapy, Double-strand DNA breaks, Predictive markers     

Functional properties of a new Wnt11 isoform expressed in colon carcinoma cell line HT29

Colon carcinoma is a common type of neoplastic transformation. The mechanisms of its establishment and progression have been studied for several decades. Aberrant activation of canonical Wnt signaling is frequently observed in colon carcinoma cells. Moreover, expression of “noncanonical” Wnt ligands is also detected in this type of cancer. However, the role of noncanonical Wnt signaling in carcinogenesis and colorectal cancer (CRC) progression is still unclear. To study the characteristics of noncanonical Wnt signaling activation in CRC, expression of “noncanonical” ligand hWnt11 was examined in HT29 human colon carcinoma cells. For the first time it was shown that alternative splicing accompanies hWnt11 expression in CRC. A new hWnt11 isoform (hWnt11sp3) was identified. Unlike hWnt11, the isoform is not secreted and lacks the ability to inhibit canonical Wnt signaling. Different functional properties of the ligand hWnt11 and its isoform may reflect a special role of alternative splicing in carcinogenesis and tumor progression, since aberrant activity of canonical Wnt signaling is observed in many tumor cells. The existence of several Wnt isoforms and the difference in their functional properties should be taken into account when investigating the role of Wnt ligands.     

Methylation of cancer-stem-cell-associated Wnt target genes predicts poor prognosis in colorectal cancer patients

Gene signatures derived from cancer stem cells (CSCs) predict tumor recurrence for many forms of cancer. Here, we derived a gene signature for colorectal CSCs defined by high Wnt signaling activity, which in agreement with previous observations predicts poor prognosis. Surprisingly, however, we found that elevated expression of Wnt targets was actually associated with good prognosis, while patient tumors with low expression of Wnt target genes segregated with immature stem cell signatures. We discovered that several Wnt target genes, including ASCL2 and LGR5, become silenced by CpG island methylation during progression of tumorigenesis, and that their re-expression was associated with reduced tumor growth. Taken together, our data show that promoter methylation of Wnt target genes is a strong predictor for recurrence of colorectal cancer, and suggest that CSC gene signatures, rather than reflecting CSC numbers, may reflect differentiation status of the malignant tissue.