Upregulation of glycolytic enzymes in proteins secreted from human colon cancer cells with 5‐fluorouracil resistance

Abstract

5-Fluorouracil (5-FU) is the most commonly used chemotherapeutic agent for colorectal cancer (CRC). However, resistance to this drug is a major obstacle in CRC chemotherapy. Accurate prediction of response to 5-FU would avoid unnecessary chemotherapy and allow the selection of other effective drugs. To identify a candidate predictor of 5-FU resistance, we isolated secreted proteins that were up- or downregulated in a 5-FU-resistant cancer cell line, compared with the parent cell line (SNU-C4), using a stable isotope-coded labeling protocol. For validating the clinical applicability of this method, levels of the identified proteins were determined in the sera of 46 patients treated with 5-FU. In total, 238 proteins with molecular weights ranging from 50 to 75 kDa were identified. Among these, 45 and 35 secreted proteins were up- and downregulated in the 5-FU-resistant cell line, respectively. We observed significant upregulation of glycolytic enzymes, including glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase M2 (PK-M2), transketolase, and NADP(+)-dependent malic enzyme 1. In particular, the level of PK-M2, a key enzyme in the glycolytic pathway, showed an increasing tendency in both sera and tissues from CRC patients displaying no response to 5-FU-based chemotherapy (progressive and stable disease cases), compared with that in complete or partial responders to 5-FU-based chemotherapy; however, it did not reach the statistical significance. In conclusion, increasing pattern of PK-M2 observed with 5-FU resistance induced in vitro and in sera and tissues from CRC patients displaying poor response to 5-FU-based chemotherapy suggest the relevance of dysregulated glycolysis and 5-FU-resistant CRC.

Dichloroacetate induces apoptosis and cell-cycle arrest in colorectal cancer cells

“…This could have clinical implications for the treatment of metastatic colorectal cancer, as it is usually the highly invasive metastatic cancers that are most resistant to conventional chemotherapy, and which may be most sensitive to PDK inhibition. In support of this, a recent study reported that the colorectal tumours resistant to 5-fluorouracil are more likely to have upregulated glycolysis, and hence more amenable to therapy targeting cancer metabolism (Shin et al, 2009). In this regard, our results contrast the findings of Wong et al (2008), who found highly invasive endometrial cancer cells to be most resistant to DCA treatment.…”

The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action

“…Alterations in the activity of human TKT have been reported to cause and/or accompany different pathological disorders, including the Wernicke-Korsakoff syndrome, Alzheimer disease, or diabetes (14 -16). Furthermore, TKT was suggested to be a critical determinant for impaired hippocampal neurogenesis, lymphatic metastasis of hepatocarcinoma, fibromyalgia, tumor cell growth, resistance of colon cancer toward 5-fluoruracil, and female fertility (17)(18)(19)(20)(21).…”

Mass spectrometry of peptides and proteins from human blood

“…Given the challenges associated with the direct examination of blood fluids there have been attempts to model cancer and other cells in culture byexamining the secreted proteins, where the media represents the circulating blood. However, many of the proteins observed may result from the rapid growth and secretion, but also death and release, of proteins to the culture (Sardana, Marshall, & Diamandis, 2007;Chenau et al, 2009;Shin et al, 2009), and has resulted in the discovery of clusterin as a serological marker of cancer (Gunawardana et al, 2009). A review of the literature shows that many results have been obtained by a wide spectrum of biologists, biochemists, geneticists and analytical scientists thereby demonstrating that protein and peptide MS technologies have advanced to the point that they no longer strictly require specialized knowledge of MS to utilize.…”