Hyperglycemia-Induced Thioredoxin-Interacting Protein Expression Differs in Breast Cancer–Derived Cells and Regulates Paclitaxel IC50

Abstract

Purpose: We studied the hyperglycemia-induced expression of thioredoxin-interacting protein (TXNIP) expression and its relevance on the cytotoxic activity of paclitaxel in mammary epithelial^derived cell lines. Experimental Design: Nontumorigenic cells (MCF10A); tumorigenic, nonmetastatic cells (MCF-7/T47D); and tumorigenic, metastatic cells (MDA-MB-231/MDA-MB-435s) were grown either in 5 or 20 mmol/L glucose chronically. Semiquantitative reverse transcription-PCR was used to assess TXNIP RNA expression in response to glucose. Reactive oxygen species were detected by CM-H2DCFDA (5-6-chloromethyl-2 ¶,7 ¶-dichlorodihydrofluorescein diacetate) and measured for mean fluorescence intensity with flow cytometry. Thioredoxin activity was assayed by the insulin disulfide-reducing assay. Proliferation was evaluated using CellTiter96 reagent with 490-nm absorption. Obtained absorbance values were used to calculate the paclitaxel IC 50 in 5 or 20 mmol/L glucose using the Chou's dose-effect equation. Results: We show that hyperglycemia by itself affects the level of TXNIP RNA in breast cancerd erived cells. TXNIP RNA level differs between nontumorigenic/nonmetastatic, tumorigenic cells (low TXNIP level), and metastatic cells (highTXNIP level). The differences inTXNIP RNA level, in reactive oxygen species level, and in thioredoxin activity are all related. We further show that hyperglycemia is a favorable condition in increasing the paclitaxel cytotoxicity by causing IC 50 3-fold decrease in metastatic breast cancer^derived MDA-MB-231cells.The increased paclitaxel cytotoxicity is associated with an additive effect on the hyperglycemia-mediated TXNIP expression more evident in conditions of hyperglycemia than normoglycemia. Conclusions: Our study opens a new perspective on the relevance of metabolic conditions of hyperglycemia in the biology and treatment of cancer, particularly in view of the epidemic of diabetes.We have recently shown that the level of thioredoxininteracting protein (TXNIP) RNA, also known as vitamin D 3 up-regulated protein-1, statistically significantly increased in response to levels of glucose shifted from 5 mmol/L (equivalent to metabolic condition of normoglycemia) to 20 mmol/L (equivalent to conditions of diabetes or postprandial hyperglycemia) in the highly metastatic breast cancer -derived MDA-MD-231 cells grown in vitro tissue culture (1). We also showed that TXNIP RNA level corresponded to persistent elevation of TXNIP protein (e.g., ref. 1). 3 Although increased TXNIP RNA level induced by hyperglycemia (20 mmol/L glucose) was associated with unchanged thioredoxin RNA level, thioredoxin measurable activity was notably reduced (1.6-fold than the control), and the level of reactive oxygen species (ROS) increased (2.3-fold than control), in MDA-MD-231 cells (1). We further showed that glucose-induced TXNIP/thioredoxin/ ROS axis regulation was mediated by p38 mitogen-activated protein kinase (MAPK) signaling pathway because the use of SB203580-specific kinase inhibitor eliminated the glucosei...

Hyperglycemia regulates MDR-1, drug accumulation and ROS levels causing increased toxicity of carboplatin and 5-fluorouracil in MCF-7 cells

“…By utilizing this cellular model we investigated relatively unexplored interface of the effect of hyperglycemia on cancer chemotherapy. Our observation that hyperglycemia decreases the IC50 value of carboplatin and 5-FU falls in line with reports which showed increased efficacy of certain anticancer drugs in high glucose conditions [Kung et al, 1963;Sadoff, 1998;Turturro et al, 2007b]. Interestingly, present study for the first time demonstrates that high glucose reduces P-gp level in MCF-7 cells that is preceded by reduction in P-gp mRNA implying regulation of P-gp by hyperglycemia.…”

“…Therefore, it is particularly difficult to discriminate the effects of glucose on gene transcription from these two hormones [LefrancoisMartinez et al, 1995]. However, establishment of cell lines has overridden this barrier and in several studies these have been successfully used to study the direct effect of glucose on proliferation of mammalian cells [Lefrancois-Martinez et al, 1995;Turturro et al, 2007a;Turturro et al, 2007b]. Only limited literature is available on the effect of diabetes related complications towards the outcome of cancer chemotherapy.…”

“…This observation was supported by the report from Kung et al [1963], demonstrating potentiation of antitumor effect of 5-fluorouracil (5-FU) by glucose in rats with Flexner jobling carcinoma. Recently, it has also been reported that hyperglycemia enhances the cytotoxicity of paclitaxel in MDA-MB 231 cells [Turturro et al, 2007b]. Sadoff [1998] proposed that patients whose diabetes is poorly controlled are at increased risk for severe 5-FU cytotoxicity.…”

A Crossroad of microRNAs and Immediate Early Genes (IEGs) Encoding Oncogenic Transcription Factors in Breast Cancer

“…TXNIP miR-373 [138] Metastatic breast cell lines express high levels of TXNIP compared to non-metastatic cells [140].…”

Thioredoxin and Jab1 Control Estrogen- and Antiestrogen-Mediated Progression of the Cell Cycle Through p27 Interactions

“…Hyperglycemia was found to increase paclitaxel cytotoxicity, and this was also associated with Txnip expression. 225 In MDA-MB-231 breast cancer cells, hyperglycemia increases Txnip RNA within 6 hours of exposure. 226 When Txnip was explored for its metabolic effects in type 2 diabetes, patients with one particular variant, TXNIP-T, had both higher diastolic blood pressure (5.5 mmHg) and higher trigliceride concentrations (1.6 fold).…”