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Updated: May 21, 2026
Profiling Thiol Redox Proteome Using Isotope Tagging Mass Spectrometry
Published on: March 24, 2012
Proteomic analysis of covalent modifications of tubulins by isothiocyanates
Zhen Xiao1, Lixin Mi, Fung-Lung Chung
1Laboratory of Proteomics and Analytical Technologies, Advanced Technology Program, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, MD, USA.
Abstract:
Although isothiocyanates (ITC), which are found in cruciferous vegetables, have been shown to inhibit carcinogenesis in animal models and induce apoptosis and cell cycle arrest in tumor cells, the biochemical mechanisms of cell growth inhibition by these compounds are not fully understood. Studies have reported that ITC binding to intracellular proteins may be an important event for initiating apoptosis. Specific protein target(s) and molecular mechanisms for ITC have been investigated in human lung cancer A549 cells using proteomic tools. Cells were treated with various amounts (1-100 micromol/L) of radiolabeled phenethyl-ITC (PEITC) and sulforaphane (SFN) and the extracted proteins resolved using 2-dimensional gel electrophoresis. The results of mass spectrometric analyses suggested that tubulin may be an in vivo binding target for ITC. The binding of ITC to tubulin was associated with growth arrest. The proliferation of A549 cells was significantly reduced by ITC, with benzyl-ITC (BITC) having a greater relative activity than PEITC or SFN. Mitotic arrest and apoptosis as well as disruption of microtubule polymerization were induced in the order: BITC > PEITC > SFN. An analysis of tubulins isolated from BITC-treated A549 cells showed that Cys(347), a conserved cysteine in all α-tubulin isoforms, was covalently modified by BITC. Taken together, these results suggest that tubulin is a binding target of ITC and that this interaction can lead to growth inhibition and apoptosis.
Insights
Isothiocyanates (ITC) from cruciferous vegetables inhibit cancer cell growth by targeting tubulin. This interaction disrupts microtubules, causing cell cycle arrest and apoptosis, with benzyl-ITC being most potent.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Isothiocyanates (ITC) found in cruciferous vegetables show anti-carcinogenic properties.
- Mechanisms of ITC-induced cell growth inhibition, particularly protein interactions, require further elucidation.
Purpose of the Study:
- To identify specific protein targets of ITC in human lung cancer cells.
- To investigate the molecular mechanisms underlying ITC-mediated cell growth inhibition and apoptosis.
Main Methods:
- Proteomic analysis of human lung cancer A549 cells treated with radiolabeled phenethyl-ITC (PEITC) and sulforaphane (SFN).
- 2-dimensional gel electrophoresis and mass spectrometry to identify protein targets.
- Analysis of tubulin modification and its effect on cell proliferation and microtubule polymerization.
Main Results:
- Tubulin identified as a direct in vivo binding target for ITC.
- ITC binding to tubulin correlated with cell growth arrest.
- Benzyl-ITC (BITC) demonstrated greater potency than PEITC or SFN in inhibiting proliferation, inducing mitotic arrest, apoptosis, and microtubule disruption.
- Covalent modification of Cys(347) in α-tubulin by BITC was observed.
Conclusions:
- Tubulin is a key molecular target for ITC-induced anti-cancer effects.
- Interaction between ITC and tubulin leads to significant cell growth inhibition and apoptosis.
- The findings provide insights into the biochemical mechanisms of ITC as anti-cancer agents.
