ENOX2 Abstracts 1

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tNOX is both necessary and sufficient as a cellular target for the anticancer actions of capsaicin and the green tea catechin (-)-epigallocatechin-3-gallate

         (Chueh, Wu et al. 2004) Download

Capsaicin and the principal green tea catechin, (-)-epigallocatechin-3-gallate (EGCg), target tNOX, a tumor (cancer)-specific surface hydroquinone (NADH) oxidase with protein disulfide-thiol interchange activity (ECTO-NOX protein). Accordingly vector-forced over expression of tNOX in MCF-10A mammary epithelia or COS cells that lack tNOX or in COS cells that underexpress tNOX enhanced the susceptibility of growth and apoptosis to both EGCg and capsaicin. Additionally, the tNOX-transfected MCF-10A cells proliferated in Matrigel, a measure of invasiveness. In contrast, oligomeric antisense tNOX DNA abrogated growth inhibition by EGCg and capsaicin and reduced anchorage-dependent growth of HeLa (human cervical carcinoma) cells that naturally overexpress tNOX. The findings show cell surface expression of tNOX as both necessary and sufficient for the cellular anticancer activities attributed to both EGCg and capsaicin.

Inhibition of plasma membrane NADH oxidase activity and growth of HeLa cells by natural and synthetic retinoids

         (Dai, Morre et al. 1997) Download

Several retinoids, both natural and synthetic, were evaluated for their ability to modulate NADH oxidase activity of plasma membranes of cultured HeLa cells and the growth of HeLa cells in culture. Both NADH oxidase activity and the growth of cells were inhibited by the naturally-occurring retinoids all trans-retinoic acid (tretinoin) and retinol as well as by the synthetic retinoids, trans-acitretin, 13-cis-acitretin, etretinate and arotonoid ethylester (Ro 13-6298). For all retinoids tested, inhibition of NADH oxidase activity and inhibition of growth were correlated closely. With tretinoin, etretinate and arotonoid ethylester, NADH oxidase activity and cell growth were inhibited in parallel in proportion to the logarithm of retinoid concentration over the range of concentrations 10(-8) to 10(-5) M. Approximately 70% inhibition of both NADH oxidase activity and growth was reached at 10 microM. With retinol, trans-acitretin and 13-cis-acitretin, inhibition of NADH oxidase activity and growth also were correlated but maximum inhibition of both was about 40% at 10 microM. The possibility is suggested that inhibition of the plasma membrane NADH oxidase activity by retinoids may be related to their mechanism of inhibition of growth of HeLa cells in culture.

Capsaicin-mediated tNOX (ENOX2) up-regulation enhances cell proliferation and migration in vitro and in vivo

         (Liu, Hsieh et al. 2012) Download

Cancer chemoprevention is employed to block or reverse the progression of malignancies. To date, several thousands of agents have been found to possess chemopreventative activity, one of which is capsaicin, a component of chili peppers that exhibits antigrowth activity against various cancer cell lines. However, the role of capsaicin in tumorigenesis remains controversial because both cancer prevention and promotion have been proposed. Here, we made the unexpected discovery that treatment with low concentrations of capsaicin up-regulates tNOX (tumor-associated NADH oxidase) expression in HCT116 human colon carcinoma cells in association with enhanced cell proliferation and migration, as evidenced by down-regulation of epithelial markers and up-regulation of mesenchymal markers. Importantly, tNOX-knockdown in HCT116 cells by RNA interference reversed capsaicin-induced cell proliferation and migration in vitro and decreased tumor growth in vivo. Collectively, these findings provide a basis for explaining the tumor-promoting effect of capsaicin and might imply that caution should be taken when using capsaicin as a chemopreventive agent.

Cell surface NADH oxidases (ECTO-NOX proteins) with roles in cancer, cellular time-keeping, growth, aging and neurodegenerative diseases

         (Morre and Morre 2003) Download

ECTO-NOX (because of their cell surface location) proteins comprise a family of NAD(P)H oxidases of plants and animals that exhibit both oxidative and protein disulfide isomerase-like activities. The two biochemical activities, hydroquinone [NAD(P)H] oxidation and protein disulfide--thiol interchange alternate, a property unprecedented in the biochemical literature. A tumor-associated ECTO-NOX (tNOX) is cancer-specific and drug-responsive. The constitutive ECTO-NOX (CNOX) is ubiquitous and refractory to drugs. The physiological substrate for the oxidative activity appears to be hydroquinones of the plasma membrane such as reduced coenzyme Q10. ECTO-NOX proteins are growth-related and drive cell enlargement. Also indicated are roles in aging and in neurodegenerative diseases. The regular pattern of oscillations appears to be related to alpha-helix-beta-structure transitions and serves biochemical core oscillator of the cellular biological clock. Period length is independent of temperature (temperature compensated) and synchrony is achieved through entrainment.

Tea catechin synergies in inhibition of cancer cell proliferation and of a cancer specific cell surface oxidase (ECTO-NOX)

         (Morre, Morre et al. 2003) Download

The anticancer properties of tea catechins are most frequently attributed to the principal catechin (-)-epigallocatechin-3-gallate (EGCg). Efficacy was evaluated using growth of cultured HeLa cells and inhibition of the enzymatic activity of a putative cell surface tea target enzyme, a cancer-associated cell surface-located NADH oxidase (ECTO-NOX) designated tNOX. The amounts of EGCg required to inhibit by both criteria was reduced 10 times by combination with inactive catechins such as (-)-epicatechin (EC), (-)-epigallocatechin (EGC) or (-)-epicatechin-3-gallate (ECG). Various synthetic mixtures based on purified catechins and decaffeinated tea extracts treated enzymatically to reduce the ester bond-containing catechins varying in EGCg content from 0.065 to 40% were of comparable efficacy to decaffeinated green tea extracts as long as EGCg was present and the ratio of total catechins to EGCg + EGC was about 1.5. Such mixtures appear to offer potential cancer protection and therapeutic advantages over those of EGCg alone through lowered toxicity of the mixture to normal cells and for more efficient blood delivery of orally-administered catechins to a tumour site.

Early Detection: An Opportunity For Cancer Prevention Through Early Intervention

(Morre and Morre 2013) Download

Cancer is the second leading disease cause of death in the United States. A group of more than l00 different and distinctive diseases, cancer may involve any tissue of the body. Estimates are that there were over l.5 million cases in 2010 in the United States alone. Only a small fraction (less than 20%) of cancers are diagnosed at a localized stage where curative therapy is effective. Most cancers are diagnosed only after the primary tumor has already metastasized so that chemotherapy is required for treatment. Hence, early detection is a favored opportunity to reduce cancer mortality. By detecting cancer in its very earliest stages when perhaps only a small number of cells are present, it is possible that early intervention will be effective in preventing further development of the incipient cancer thereby resulting in what might be viewed as curative prevention.

Phosphorylation of serine-504 of tNOX (ENOX2) modulates cell proliferation and migration in cancer cells

         (Zeng, Chuang et al. 2012) Download

Tumor-associated NADH oxidase (tNOX; ENOX2) is a growth-related protein expressed in transformed cells. Consistent with this function, tNOX knockdown by RNA interference leads to a significant reduction in cell proliferation and migration in HeLa cells, whereas tNOX overexpression confers an aggressive phenotype. Here, for the first time, we report that tNOX is phosphorylated by protein kinase Cdelta (PKCdelta) both in vitro and in vivo. Replacement of serine-504 with alanine significantly reduces phosphorylation by PKCdelta. Co-immunoprecipitation experiments reveal an interaction between tNOX and PKCdelta. Moreover, whereas overexpression of wild-type tNOX in NIH3T3 cells increases cell proliferation and migration, overexpression of the S504A tNOX mutant leads to diminished cell proliferation and migration, reflecting reduced stability of the unphosphorylatable tNOX mutant protein. Collectively, these results suggest that phosphorylation of serine-504 by PKCdelta modulates the biological function of tNOX.


References

Chueh, P. J., L. Y. Wu, et al. (2004). "tNOX is both necessary and sufficient as a cellular target for the anticancer actions of capsaicin and the green tea catechin (-)-epigallocatechin-3-gallate." Biofactors 20(4): 235-49. [PMID: 15706060]

Dai, S., D. J. Morre, et al. (1997). "Inhibition of plasma membrane NADH oxidase activity and growth of HeLa cells by natural and synthetic retinoids." Mol Cell Biochem 166(1-2): 101-9. [PMID: 9046026]

Liu, N. C., P. F. Hsieh, et al. (2012). "Capsaicin-mediated tNOX (ENOX2) up-regulation enhances cell proliferation and migration in vitro and in vivo." J Agric Food Chem 60(10): 2758-65. [PMID: 22353011]

Morre, D. J. and D. M. Morre (2003). "Cell surface NADH oxidases (ECTO-NOX proteins) with roles in cancer, cellular time-keeping, growth, aging and neurodegenerative diseases." Free Radic Res 37(8): 795-808. [PMID: 14567438]

Morre, D. J. and D. M. Morre (2013). Early Detection: An Opportunity For Cancer Prevention Through Early Intervention.

Morre, D. J., D. M. Morre, et al. (2003). "Tea catechin synergies in inhibition of cancer cell proliferation and of a cancer specific cell surface oxidase (ECTO-NOX)." Pharmacol Toxicol 92(5): 234-41. [PMID: 12753411]

Zeng, Z. M., S. M. Chuang, et al. (2012). "Phosphorylation of serine-504 of tNOX (ENOX2) modulates cell proliferation and migration in cancer cells." Exp Cell Res 318(14): 1759-66. [PMID: 22659163]