Hypoxia Induces the Expression of Transketolase-Like 1 in Human Colorectal Cancer

Abstract

Background and Aims: Transketolase-like (TKTL) 1 is one of the key enzymes for anaerobic sugar degradation even in the presence of oxygen (aerobic glycolysis). Transketolase-dependent reactions supply malignant tumors with ribose and NADPH. Therefore, TKTL1 activity could be crucial for tumor proliferation and survival. The aim of the study was to evaluate the expression of TKTL1 in colorectal cancer (CRC) and its regulation under hypoxic conditions. Methods: We studied TKTL1 mRNA and protein expression in CRC cell lines and human CRC biopsies by quantitative real-time PCR, Western blotting and immunohistochemistry. Regulation of TKTL1 under oxygen depletion was analyzed by cultivating cells either in a three-dimensional spheroid model or in a hypoxia incubator chamber. Results: TKTL1 mRNA was heterogeneously expressed in monolayers of cells with high levels in HT-29 and SW480. TKTL1 protein was also clearly detectable in HT-29 and SW480. Hypoxia-inducible factor (HIF)-1 protein expression correlated with TKTL1 protein expression in SW480 spheroids over time. On the one hand, induction of hypoxia in T84 spheroids did not induce TKTL1; on the other hand, hypoxia by incubation at 1% O2 in a hypoxia incubator chamber clearly showed an upregulation of TKTL1. In 50% of CRC patients, TKTL1 protein expression was upregulated in tumor compared to non-tumor tissue. The immunohistochemical staining of TKTL1 in CRC patient samples resulted in 14 positive and 30 negative samples. Conclusions: TKTL1 expression correlated with HIF-1 protein expression and was induced upon hypoxic conditions which could facilitate energy supply to tumors under these circumstances. © 2013 S. Karger AG, Basel.

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

“…18 The latter figure is much lower than in our study where 87.5% of tumors stained for TKTL1. Both studies had similar protocols for producing TMA.…”

“…2 We show here high expression of transketolase-like protein 1 (TKTL1), one of the members of the transketolase family, to predict worse survival in colorectal cancer patients, To study glucose metabolism in cancer cells we used immunohistochemistry of the transketolase isoform TKTL1, upregulated in malignancies both at the mRNA and the protein level. [17][18][19] TKTL1 expression is not a direct measure of glucose metabolism, but mirrors the metabolic activity in cancer cells and works as a tool for estimating glucose metabolism in cancer cells at the time of surgery. TKTL1 tissue expression associates with poor patient survival in various types of cancer.…”

Short Term Hypoxia Synergizes with Interleukin 15 Priming in Driving Glycolytic Gene Transcription and Supports Human Natural Killer Cell Activities

“…PPP genes from the oxidative branch (NADPH production) were up-regulated by priming, whereas mixed responses were seen for the non-oxidative branch. Here, IL-15 unexpectedly down-regulated transketolase-like 1 (TKTL1) expression opposing its expected upregulation by hypoxia (29). We thus included TKTL1 in RT-PCR validation.…”

An efficient amperometric transketolase assay: Towards inhibitor screening

“…Indeed, some recent studies have shown that human TK is a target of neurodegenerative diseases (Zhao and Zhong, 2009), diabetes (Thornalley et al, 2001) and particularly cancer (Bentz et al, 2013;Du et al, 2004;Thomas et al, 2008aThomas et al, , 2008b suggesting new therapeutic approaches. Therefore, the development of rapid, sensitive and efficient in vitro assays for TK activity profiling is highly sought to enable the identification of suitable inhibitors.…”