Cancer metastasis is the major cause of cancer morbidity and mortality, and accounts for about 90% of cancer deaths. Although cancer survival rate has been significantly improved over the years, the improvement is primarily due to early diagnosis and cancer growth inhibition. Limited progress has been made in the treatment of cancer metastasis due to various factors. Current treatments for cancer metastasis are mainly chemotherapy and radiotherapy, though the new generation anti-cancer drugs (predominantly neutralizing antibodies for growth factors and small molecule kinase inhibitors) do have the effects on cancer metastasis in addition to their effects on cancer growth. Cancer metastasis begins with detachment of metastatic cells from the primary tumor, travel of the cells to different sites through blood/lymphatic vessels, settlement and growth of the cells at a distal site. During the process, metastatic cells go through detachment, migration, invasion and adhesion. These four essential, metastatic steps are inter-related and affected by multi-biochemical events and parameters. Additionally, it is known that tumor microenvironment (such as extracellular matrix structure, growth factors, chemokines, matrix metalloproteinases) plays a significant role in cancer metastasis. The biochemical events and parameters involved in the metastatic process and tumor microenvironment have been targeted or can be potential targets for metastasis prevention and inhibition. This review provides an overview of these metastasis essential steps, related biochemical factors, and targets for intervention.

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This work presents an assay for total thiols and total disulfides in biological samples via HPLC quantification of 5-thio-2-nitrobenzoic acid (TNB) derived from the reaction of thiols with 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB, Ellman’s reagent). This method also provides simultaneous quantification of glutathione (GSH) via the measurement of the GSH DTNB adduct (GSH-TNB). By using 326 nm as the detecting wavelength, the HPLC detection limit for TNB and the GSH-TNB adduct was determined to be 15 pmol and 7.5 pmol respectively. A recovery study with OVCAR-3 cells revealed that the recovery yields for TNB in the procedures for determining non-protein thiols, protein thiols, non-protein disulfides, and protein disulfides were 99.4±1.2% (n = 3), 98.1±5.0% (n = 3), 95.6±0.9% (n = 3), and 96.6±2.3% (n = 3) respectively. The recovery yield for GSH-TNB in the procedures for determining non-protein thiols, protein thiols, non-protein disulfides, and protein disulfides were 99.0±0.3% (n = 3), 95.1±4.9% (n = 3), 96.8±0.6% (n = 3), and 95.1±2.9% (n = 3) respectively. The reproducibility, expressed as the relative standard deviation for the analyte, for TNB was determined to be 2.8% (n = 6) for non-protein thiols, 3.9% (n = 6) for protein thiols, 3.6% (n = 6) for non-protein disulfides and 4.6% (n = 6) for protein disulfides. The reproducibility for GSH-TNB was determined to be 1.6% (n= 6) for non-protein thiols and 2.6% (n = 6) for non-protein disulfides. By comparing the amount of GSH determined in a biological sample before NaBH4 reduction with that after the reduction, this method can provide information associated with thiol glutathionylation which would be useful for protein glutathionylation study. This method should be applicable to cellular, subcellular, protein, or other biomatrix samples for thiol and disulfide quantification and will be a useful analytical method in the study of thiol redox state and thiol glutathionylation.

We revisit the time-resolved photoemission in neon atoms as probed by attosecond streaking. We calculate streaking time shifts for the emission of 2p and 2s electrons and compare the relative delay as measured in a recent experiment by Schultze et al. [Science 328, 1658[Science 328, (2010]. The B-spline R-matrix method is employed to calculate accurate Eisenbud-Wigner-Smith time delays from multielectron dipole transition matrix elements for photoionization. The additional laser field-induced time shifts in the exit channel are obtained from separate, time-dependent simulations of a full streaking process by solving the time-dependent Schrödinger equation on the single-active-electron level. The resulting accurate total relative streaking time shifts between 2s and 2p emission lie well below the experimental data. We identify the presence of unresolved shake-up satellites in the experiment as a potential source of error in the determination of streaking time shifts.

The current study determined if depletion of glutathione (GSH) and inhibition of thioredoxin reductase (TR) activity could enhance radiation responses in human breast cancer stem cells by a mechanism involving thiol dependent oxidative stress. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor; sulfasalazine (SSZ), an inhibitor of xc- cysteine/glutamate antiporter; auranofin (Au), a thioredoxin reductase inhibitor; or 2AAPA, a GSH-reductase inhibitor, were used to inhibit GSH- and thioredoxin (Trx)-metabolism. Clonogenic survival, Matrigel assays, flow cytometry cancer stem cell assays (CD44+CD24-ESA+ or ALDH1), and human tumor xenograft models were used to determine the antitumor activity of drug and radiation combinations. Combined inhibition of GSH and Trx-metabolism enhanced cancer cell clonogenic killing and radiation responses in human breast and pancreatic cancer cells via a mechanism that could be inhibited by N-acetylcysteine (NAC). Au, BSO, and radiation also significantly decreased breast cancer cell migration and invasion in a thiol dependent fashion that could be inhibited by NAC. In addition pre-treating cells with Au sensitized breast cancer stem cell populations to radiation in vitro as determined by CD44+CD24-ESA+ or ALDH1. Combined administration of Au and BSO, given prior to radiation significantly increased the survival of mice with human breast cancer xenografts as well as decreasing the number of ALDH1 positive cancer stem cells. These results indicate that combined inhibition of GSH- and Trx-dependent thiol metabolism using pharmacologically relevant agents can enhance responses of human breast cancer stem cells to radiation both in vitro and in vivo.

Thiol redox state (TRS) is an important parameter to reflect intracellular oxidative stress and is associated with various normal and abnormal biochemical processes. Agents that can be used to increase intracellular TRS will be valuable tools in TRS-related research. Glutathione reductase (GR) is a critical enzyme in the homeostasis of TRS. The enzyme catalyzes the reduction of GSSG to GSH to maintain a high GSH:GSSG ratio. Inhibition of the enzyme can be used to increase TRS. Despite the reports of various GR inhibitors, N,N-bis(2-chloroethyl)-N-nitrosourea, an anticancer drug with IC 50 ‫؍‬ 647 M against yeast GR, remains the most commonly used GR inhibitor in the literature. However, the toxicity caused by nonspecific interactions, as well as inhibition of DNA synthesis, complicates the use of N,N-bis(2-chloroethyl)-N-nitrosourea as a GR inhibitor. We report 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA) as a novel irreversible GR inhibitor. 2-AAPA was prepared by one-step synthesis from commercially available reagents. The K i and k inact of 2-AAPA against yeast GR were determined to be 56 M and 0.1 min ؊1 , respectively. At the concentration that produced >80% yeast GR inhibition, 2-AAPA showed no inhibition against glutamylcysteine synthetase, glutathione synthetase, catalase, and superoxide dismutase, but minimal inhibition against glutathione S-transferase and glutathione peroxidase. In CV-1 cells, 2-AAPA (0.1 mM) produced 97% GR inhibition, 25% GSH reduction, and a 5-fold increase in GSSG in 20 min. The compound can be a useful tool in TRS-related research.

We consider the ionization of the hydrogen molecular ion after one-, two-, and three-photon absorption over a large range of photon energies between 9 and 40 eV in the fixed-nuclei approximation. The temporal development of the system is obtained in a fully ab initio time-dependent grid-based approach in prolate spheroidal coordinates. The alignment dependence of the one-photon ionization amplitude is highlighted in the framework of time-dependent perturbation theory. For one-photon ionization as a function of the nuclear separation, the calculations reveal a significant minimum in the ionization probability. The suppressed ionization is attributed to a Cooper-type minimum, which is similar, but not identical, to the cancellation effect observed in photoionization cross sections of some noble-gas atoms. The effect of the nonspherical two-center Coulomb potential is analyzed. For two-and three-photon ionization, the angle-integrated cross sections clearly map out intermediate-state resonance, and the predictions of the current computations agree very well with those from time-independent calculations. The dominant emission modes for two-photon ionization are found to be very similar in both resonance and off-resonance regions.