Targeting the ubiquitin-proteasome pathway with the proteasome inhibitor bortezomib has emerged as a promising approach for the treatment of several malignancies. The cellular and molecular effects of this agent on colorectal cancer cells are poorly characterized. This study investigated the antiproliferative effect of bortezomib on colorectal cancer cell lines (Caco-2 and HRT-18). In order to define the proteins potentially involved in the mechanisms of action, proteome profiling was applied to detect the proteins altered by bortezomib. The in vitro efficacy of bortezomib as a single agent in colorectal cancer cell lines was confirmed. Proteome profiling with two-dimensional PAGE followed by mass spectrometry revealed the upregulation of the major inducible isoform of heat shock protein 70 (hsp72) and lactate dehydrogenase B in both cell lines, as well as the induction of aldo-keto reductase family 1 member B10 (AKR1B10) in HRT-18 cells. Both AKR1B10 and hsp72 exert cell-protective functions. This study shows for the first time a bortezomib-induced upregulation of AKR1B10. Small interfering RNA-mediated inhibition of this enzyme with known intracellular detoxification function sensitized HRT-18 cells to therapy with the proteasome inhibitor. To further characterize the relevance of AKR1B10 for colorectal tumors, immunohistochemical expression was shown in 23.2% of 125 tumor specimens. These findings indicate that AKR1B10 might be a target for combination therapy with bortezomib.
Cancer proteomics is a rapidly developing fi eld and promises to accelerate the discovery of new diagnostic, prognostic and therapy-related biomarkers. Increasingly, the mechanisms of action of cancer drugs are defi ned at the molecular level. Th e possibility of detecting hundreds and thousands of proteins at the same point of time is a tool to defi ne proteins associated with response or resistance to therapy. Th is strategy has been applied successfully in cell culture models and is implemented as translational research tool in early clinical trials of new anti-cancer agents. Th is review aims to summarize basic concepts and techniques of proteome analysis, its challenges and limitations, and discusses the opportunities for cancer therapy.
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