Transketolase protein TKTL1 overexpression: A potential biomarker and therapeutic target in breast cancer

Malignant tumors degrade glucose to lactate even in the presence of oxygen via the pentose phosphate pathway (ppp). The non-oxidative part of the ppp is controlled by thiamine-dependant transketolase enzyme reactions. Overexpression of the transketolase-like-1-gene (TKTL1) in urothelial and colorectal cancer is associated with poor patient outcome. We analyzed the expression of the TKTL1 protein in a retrospective institution-based patient cohort with invasive breast cancer by immunohistochemical analysis of 124 paraffin-embedded breast cancer tissues. Our study revealed TKTL1 expression in 86% of breast cancer specimens with 45% showing high expression levels. In contrast, only 29% of corresponding non-neoplastic breast tissues were TKTL1 immunopositive, including 9% with high expression levels. High expression levels of TKTL1 correlated significantly to Her2/neu overexpression (p=0.015). However, TKTL1 expression failed to reach statistical significance for other common prognostic parameters. In contrast to recent data for e.g. colorectal cancer TKTL1 overexpression did not correlate to patient outcome and survival. However, in the context of novel insights into TKTL1-related tumor metabolism and the high proportion of TKTL1 overexpressing breast cancers, this enzyme represents a potential candidate for targeted inhibition of tumor growth in this tumor entity.     

Overexpression of transketolase protein TKTL1 is associated with occurrence and progression in nasopharyngeal carcinoma: a potential therapeutic target in nasopharyngeal carcinoma

Over 80 years ago, Warburg identified a particular metabolic pathway in carcinomas characterised by the anaerobic degradation of glucose even in the presence of oxygen that leads to the production of large amounts of lactate (known as the Warburg effect). Now, widespread clinical use of positron-emission tomography (PET) has confirmed that there exists enhanced glucose degradation in tumors. Recent research demonstrated that pentose phosphate pathway (PPP) was augmented in some tumors, especially non-oxidative part of PPP. The non-oxidative part of PPP is controlled by transketolase enzyme reactions. The present study designed to evaluate the effect of transketolase activity on nasopharyngeal carcinoma. It was found that the transketolase activity was significantly stronger in human nasopharyngeal carcinoma tissues than those in human chronic nasopharyngitis tissues. There is a strong upregulation of the transketolase-like-1 (TKTL1) in human nasopharyngeal carcinoma tissues and cell line (CNE), whereas transketolase (TKT) and transketolase-like-2 (TKTL2) were not upregulated. After inhibited the expression of (TKTL1) by RNAi, we found that total transketolase activity was dramatically downregulated and the proliferation of cancer cells was significantly inhibited in CNE cells. These results indicate that TKTL1 gene influences total transketolase activity and cell proliferation in human nasopharyngeal carcinoma cells, suggesting that TKTL1 gene plays an important role on glycometabolism in tumors and it might become a novel target for tumor gene therapy.     

Transketolase‐like protein 1 (TKTL1) is required for rapid cell growth and full viability of human tumor cells

Cancer cells display high rates of aerobic glycolysis, a phenomenon known as the Warburg effect. Lactate and pyruvate, the end products of glycolysis, are overproduced by cancer cells even in the presence of oxygen. The pentose phosphate pathway (PPP) allows glucose conversion to ribose for nucleic acid synthesis, glucose degradation to lactate, and regeneration of redox equivalents. The nonoxidative part of the PPP is controlled by transketolase (TKT) enzymes. One TKT isoform, the transketolase‐like protein 1 (TKTL1) is specifically upregulated in different human cancers and its overexpression predicts a poor patient's survival. This finding implicates that an increased TKTL1 expression may activate the PPP leading to enhanced cancer cell growth and survival. To analyze the functional role of TKTL1 in malignant progression, we inhibited TKTL1 by RNAi technologies in human HCT116 colon carcinoma cells. TKTL1 suppression resulted in a significantly slowed cell growth, glucose consumption and lactate production. In TKTL1 knockdown‐cells, the intracellular reactive oxygen species levels were not significantly increased, whereas the sensitivity towards oxidative stress‐induced apoptosis was clearly enhanced. These data provide new clues on the importance of TKTL1 dys‐regulation in tumor cells and indicate that TKTL1 overexpression may be considered not only as a new tumor marker but also as a good target for anticancer therapy. © 2008 Wiley‐Liss, Inc.     

Transketolase-like protein 1 confers resistance to serum withdrawal in vitro

Transketolase-like protein 1 (TKTL1) is a member of the family of transketolase enzymes of which the founder member transketolase (TKT) is known to play a central role in the non-oxidative part of the pentose phosphate pathway. According to several publications TKTL1 is the only family member, whose expression is substantially de-regulated in a variety of solid tumours. Over-expression of TKTL1 correlates with poor prognosis of cancer patients and TKTL1 itself represents a potential therapeutic target owing to its possible involvement in the regulation of the proliferation and metabolism of cancer cells. We show that exogenously expressed TKTL1 provides HEK293 cells with moderate growth advantages under standard culture conditions, while protecting cells from growth factor withdrawal-induced apoptosis. Importantly, we identified TKTL1 with the JFC12T10 antibody as a 65kDa protein, which was however absent in most tumour cell lines tested. Primary head and neck squamous cell carcinomas of various localisations were characterised by a focal pattern with single cells strongly expressing TKTL1, rather than by a homogeneous expression pattern within the tumour mass.     

Metastasis is promoted by a bioenergetic switch: new targets for progressive renal cell cancer

Targeted therapies have demonstrated clinical benefit with limited impact on long-term disease specific survival in the treatment of renal cell cancer (RCC). New opportunities for the treatment of tumors that are resistant or have relapsed, are needed. Increased anaerobic glucose fermentation to lactate (aerobic glycolysis), leading to oxygen- and mitochondria-independent ATP generation is a hallmark of aggressive cancer growth. This metabolic shift results in increased lactate production via cycling through the pentose phosphate pathway (PPP), and plays an important role in tumor immune escape, progression and resistance to immune-, radiation- and chemo-therapy. This study explored the activity and impact of the oxidative and nonoxidative branches of the PPP on RCC to evaluate new therapeutic options. Activity was determined in the oxidative branch by glucose-6-phosphate-dehydrogenase (G6PD) activity, and in the nonoxidative branch by the total transketolase activity and the specific expression of the transketolase-like-1 (TKTL1) protein. Transketolase and G6PD activity were intensely elevated in tumor tissues. Transketolase, but not G6PD activity, was more elevated in metastasizing tumors and TKTL1 protein was significantly overexpressed in progressing tumors (p = 0.03). Lethal tumors, where surrogate parameters such as grading and staging had failed to predict progression, showed intensive TKTL1 protein expression. RCC was found to have activated oxidative and nonoxidative glucose metabolism through the PPP, displaying a bioenergetic shift toward nonoxidative glucose fermentation in progressing tumors. The coexistence of cancer cells with differentially regulated energy supplies provides new insights in carcinogenesis and novel anticancer targets.     

Transketolase-like protein 1 expression predicts poor prognosis in colorectal cancer

Background: Transketolase-like protein 1 (TKTL1) is an isoform of tranketolase, a key protein in a cancer cell's glucose metabolism that causes rapid cell growth and controls the non-oxidative part of the pentose phosphate pathway (PPP). Its overexpression occurs in several human cancer types. Our purpose was to study whether TKTL1 expression in colorectal cancer tissue associates with these patients’ prognosis. Methods: We collected retrospectively patient data and tissue samples from 840 colorectal cancer patients treated at Helsinki University Hospital, then stained tumor tissue microarrays for TKTL1 by immunohistochemistry, and compared immunohistochemical tissue expression with clinico-pathological parameters and survival. Results: High expression of TKTL1 associated with high Dukes stage, non-mucinous adenocarcinoma, and left-sided disease. Patients with high TKTL1 expression had poorer prognosis than those with low expression, with a 5-year disease-specific survival of 55.7% vs. 62.7%. Conclusion: We show that high TKTL1 in tumor tissue can lead to poor survival in colorectal cancer. TKTL1 thus can serve as a candidate marker for identifying patients at risk of recurrent disease.     

结肠癌及癌旁组织中TKTL1 的表达

 目的　探讨转酮酶样基因TKTL1 在人类结肠癌发生发展中的作用。方法　用实时定量PCR 检测结肠癌及癌旁组织中转酮酶样基因TKTL1 mRNA 表达水平,连续监测法检测各组织中总转酮酶 活性。结果　TKTL1 mRNA 在结肠癌组织中比癌旁组织中的表达明显增强,且侵袭性结肠癌比非侵 袭性结肠癌表达增强。同样,结肠癌组织中总转酮酶活性比癌旁组织中高( P < 0. 01) ,侵袭性结肠癌较 非侵袭性结肠癌中转酮酶活性增高( P < 0. 01) 。结论　TKTL1 mRNA 表达与人类结肠癌的发生发展 密切相关。     

Cationic amino acid transporter PQLC2 is a potential therapeutic target in gastric cancer

Tumor cells overexpress amino acid transporters to meet the increased demand for amino acids. PQ loop repeat‐containing (PQLC)2 is a cationic amino acid transporter that might be involved in cancer progression. Here, we show that upregulation of PQLC2 is critical to gastric cancer (GC) development in vitro and in vivo. Both PQLC2 mRNA and protein were overexpressed in GC tissues, especially of the diffuse type. Overexpression of PQLC2 promoted cell growth, anchorage independence, and tumor formation in nude mice. This was due to activation of MEK/ERK1/2 and PI3K/AKT signaling. Conversely, PQLC2 knockdown caused growth arrest and cell death of cancer cells and suppressed tumor growth in a mouse xenograft model. These results suggest that targeting PQLC2 is an effective strategy for GC treatment.     

Targeted therapies in gastroesophageal cancer

Gastroesophageal cancers comprising gastric cancer (GC), and cancers of the distal oesophagus and gastroesophageal junction (GEJ) are a global health threat. In Western populations the incidence of GC is declining which has been attributed to effective strategies of eradicating Helicobacter pylori infection. To the contrary, GEJ cancers are on the rise, with obesity and reflux disease being viewed as major risk factors. During the past decade perioperative chemotherapy, pre- or postoperative radio-chemotherapy, and, in Asian populations, adjuvant chemotherapy have been shown to improve the outcome of patients with advanced GC and GEJ cancers suited for surgery. Less progress has been made in the treatment of metastatic disease. The introduction of trastuzumab in combination with platinum/fluoropyrimidine-based chemotherapy for patients with HER2-positive disease has marked a turning point. Recently, several novel agents targeting growth factor receptors, angiogenic pathways, adhesion molecules and mediators of intracellular signal transduction have been clinically explored. Here we summarise the current status and future developments of molecularly targeted therapies in GC and GEJ cancer.     

Downregulation of leucine‐rich repeats and immunoglobulin‐like domains 1 by microRNA‐20a modulates gastric cancer multidrug resistance

Multidrug resistance (MDR) significantly restricts the clinical efficacy of gastric cancer (GC) chemotherapy, and it is critical to search novel targets to predict and overcome MDR. Leucine‐rich repeats and immunoglobulin‐like domains 1 (LRIG1) has been proved to be correlated with drug resistance in several cancers. The present study revealed that LRIG1 was overexpressed in chemosensitive GC tissues and decreased expression of LRIG1 predicted poor survival in GC patients. We observed that upregulation of LRIG1 enhanced chemosensitivity in GC cells. Interestingly, miR‐20a, which was overexpressed in GC MDR cell lines and tissues, was identified to regulate LRIG1 expression by directly targeting its 3′ untranslated region. We also found that inhibition of miR‐20a suppressed GC MDR, and upregulation showed opposite effects. Moreover, we demonstrated that the miR‐20a/LRIG1 axis regulated GC cell MDR through epidermal growth factor receptor (EGFR)‐mediated PI3K/AKT and MAPK/ERK signaling pathways. Finally, LRIG1 expression in human GC tissues is inversely correlated with miR‐20a and EGFR. Taken together, the newly identified miR‐20a/LRIG1/EGFR link provides insight into the MDR process of GC, and targeting this axis represents a novel potential therapeutic strategy to block GC chemoresistance.     

Survey of Her2-neu Expression and its Correlation with Histology of Gastric Carcinoma and Gastroesophageal Junction Adenocarcinoma

Background: There is increasing evidence that HER2-neu is an important biomarker in gastric carcinomas (GC) and gastroesophageal junction (GEJ) adenocarcinomas. The aim of this study was to evaluate HER2-neu expression and also some clinicopathological features of these neoplasms. Materials and Methods: We selected 211 paraffin-embedded blocks, 193 GC and 18 GEJ. Then 4 micron sections were prepared for staining with hematoxylin and eosin and also for IHC (Her2-neu). The Chi-square test was used for significance between expression of HER2-neu and clinicopathological parameters. Results: In patients with advanced cancer of GC and GEJ, HER2-neu overexpression was more associated with the intestinal cancer subtype. Conclusions: This could be a guide to new complementary therapy for affected patients.     

Metastasis-associated in colon cancer-1 promotes vasculogenic mimicry in gastric cancer by upregulating TWIST1/2

Vasculogenic mimicry (VM) is a blood supply modality that is strongly associated with the epithelial-mesenchymal transition (EMT), TWIST1 activation and tumor progression. We previously reported that metastasis-associated in colon cancer-1 (MACC1) induced the EMT and was associated with a poor prognosis of patients with gastric cancer (GC), but it remains unknown whether MACC1 promotes VM and regulates the TWIST signaling pathway in GC. In this study, we investigated MACC1 expression and VM by immunohistochemistry in 88 patients with stage IV GC, and also investigated the role of TWIST1 and TWIST2 in MACC1-induced VM by using nude mice with GC xenografts and GC cell lines. We found that the VM density was significantly increased in the tumors of patients who died of GC and was positively correlated with MACC1 immunoreactivity (p < 0.05). The 3-year survival rate was only 8.6% in patients whose tumors showed double positive staining for MACC1 and VM, whereas it was 41.7% in patients whose tumors were negative for both MACC1 and VM. Moreover, nuclear expression of MACC1, TWIST1, and TWIST2 was upregulated in GC tissues compared with matched adjacent non-tumorous tissues (p < 0.05). Overexpression of MACC1 increased TWIST1/2 expression and induced typical VM in the GC xenografts of nude mice and in GC cell lines. MACC1 enhanced TWIST1/2 promoter activity and facilitated VM, while silencing of TWIST1 or TWIST2 inhibited VM. Hepatocyte growth factor (HGF) increased the nuclear translocation of MACC1, TWIST1, and TWIST2, while a c-Met inhibitor reduced these effects. These findings indicate that MACC1 promotes VM in GC by regulating the HGF/c-Met-TWIST1/2 signaling pathway, which means that MACC1 and this pathway are potential new therapeutic targets for GC.     

LOX1在胃癌中的表达及其促肿瘤生长的机制探讨

目的:探讨血凝素样氧化型低密度脂蛋白受体1（lectin-like oxidized low density lipoprotein receptor-1,LOX1）在胃癌中的表达及与预后相关性,同时明确其促胃癌生长作用及潜在机制。方法:利用人类癌症基因组图谱(TCGA)、基因表达汇编(GEO)和癌症细胞系百科全书(CCLE)数据库分析LOX1在胃癌组织和细胞中的表达水平;利用多种统计方法分析LOX1表达水平与胃癌患者预后及临床特征的相关性;通过质粒转染敲低LOX1,进一步应用细胞功能实验（CCK-8、克隆形成、EdU实验）探究LOX1对胃癌细胞增殖能力的调控作用;通过Western blot、qPCR、免疫荧光分析LOX1对NF-κB信号通路激活的调控作用。结果:LOX1在胃癌组织和细胞中显著高表达;高水平LOX1提示胃癌患者预后较差且肿瘤较易发生转移;敲低LOX1显著抑制肿瘤细胞增殖;敲低LOX1显著抑制胃癌细胞中NF-κB信号通路的激活。结论:LOX1通过激活NF-κB信号通路对胃癌细胞增殖能力具有调控作用;LOX1可作为生物标记物提示患者预后;靶向LOX1可作为潜在胃癌治疗新方案。     

lncRNA SNHG1通过抑制p27kip1促进胃癌细胞的增殖作用

目的:确定长链非编码RNA SNHG1（lncRNA SNHG1）在胃癌中的表达，并探讨其在胃癌细胞增殖中的作用。方法:通过原位杂交及实时荧光定量PCR（RT-qPCR）检测26例胃癌患者肿瘤组织及相应癌旁组织中SNHG1的表达。同时通过RT-qPCR检测正常胃上皮细胞及胃癌细胞系中SNHG1的表达情况。为评估SNHG1对胃癌细胞增殖能力的影响，向胃癌细胞系中转染shRNA或pcDNA调控SNHG1表达，并通过CCK-8法、流式细胞术及克隆形成实验检测细胞活力、细胞周期与细胞形成集落的能力。通过相关性分析、免疫组化、RT-qPCR及Western blot等方法检测了胃癌组织及细胞中p27kip1的表达，并进一步研究其与SNHG1的关系。结果:lncRNA SNHG1在胃癌组织中的表达明显高于癌旁组织，尤其是在肿瘤中晚期。SNHG1可明显促进胃癌细胞的增殖，缩短细胞周期，增强肿瘤细胞的集落形成能力。同时胃癌组织及细胞系中p27kip1与SNHG1存在相关性，上调SNHG1可以抑制胃癌细胞中p27kip1的表达，反之亦然。上调p27kip1可以拮抗SNHG1对胃癌细胞增殖能力的促进作用。结论:lncRNA SNHG1通过抑制p27kip1促进胃癌细胞增殖，表明SNHG1可能成为胃癌的潜在治疗靶点。     

Modulation of pentose phosphate pathway during cell cycle progression in human colon adenocarcinoma cell line HT29

Cell cycle regulation is dependent on multiple cellular and molecular events. Cell proliferation requires metabolic sources for the duplication of DNA and cell size. However, nucleotide reservoirs are not sufficient to support cell duplication and, therefore, biosynthetic pathways should be upregulated during cell cycle. Here, we reveal that glucose‐6‐phosphate dehydrogenase (G6PDH) and transketolase (TKT), the 2 key enzymes of oxidative and nonoxidative branches of the pentose phosphate pathway (PPP), respectively, which is necessary for nucleotide synthesis, are enhanced during cell cycle progression of the human colon cancer cell line HT29. These enhanced enzyme activities coincide with an increased ratio of pentose monophosphate to hexose monophosphate pool during late G1 and S phase, suggesting a potential role for pentose phosphates in proliferating signaling. Isotopomeric analysis distribution of nucleotide ribose synthesized from 1,2‐¹³C₂‐glucose confirms the activation of the PPP during late G1 and S phase and reveals specific upregulation of the oxidative branch. Our data sustain the idea of a critical oxidative and nonoxidative balance in cancer cells, which is consistent with a late G1 metabolic check point. The distinctive modulation of these enzymes during cell cycle progression may represent a new strategy to inhibit proliferation in anticancer treatments. © 2009 UICC