Ai Shih

Integrin αVβ3 contains a receptor site for resveratrol

Resveratrol is a naturally occurring polyphenol, which causes apoptosis in cultured cancer cells. We describe a cell surface resveratrol receptor on the extracellular domain of hetero‐dimeric αVβ3 integrin in MCF‐7 human breast cancer cells. This receptor is linked to induction by resveratrol of extracellular‐regulated kinases 1 and 2 (ERK1/2)‐ and serine‐15‐p53‐dependent phosphorylation leading to apoptosis. The integrin receptor is near the Arg‐Gly‐Asp (RGD) recognition site on the integrin; an integrin‐binding RGD peptide inhibits induction by resveratrol of ERK1/2‐and p53‐dependent apoptosis. Antibody (Ab) to integrin αVβ3, but not to αVβ5, inhibits activation by resveratrol of ERK1/2 and p53 and consequent apoptosis in estrogen receptor‐α (ERα) positive MCF‐7, and ERα‐negative MDA‐MB231 cells. Resveratrol is displaced from the purified integrin by an RGD, but not RGE, peptide, and by αVβ3 integrin‐specific Ab. Resveratrol action is blocked by siRNAβ3, but not by siRNAαV. [14C]‐Resveratrol binds to commercially purified integrin αVβ3 and to αVβ3 prepared from MCF‐7 cells;binding of [14C]‐resveratrol to the β3, but not to the αV monomer, is displaced by unlabeled resveratrol. In conclusion, binding of resveratrol to integrin αVβ3, principally to the β3 monomer, is essential for transduction of the stilbene signal into p53‐dependent apoptosis of breast cancer cells.—Lin, H.‐Y., Lansing, L., Merillon, J.‐M., Davis, F. B., Tang, H.‐Y., Shih, A., Vitrac, X., Krisa, S., Keating, T., Cao, H. J., Bergh, J., Quackenbush, S., Davis, P. J. Integrin αVβ3 contains a receptor site for resveratrol. FASEB J. 20, E1133–E1138 (2006)

Resveratrol-induced cyclooxygenase-2 facilitates p53-dependent apoptosis in human breast cancer cells.

Cyclooxygenase-2 (COX-2) is antiapoptotic and is implicated in tumorigenesis. Recent reports, however, have also ascribed a proapoptotic action to inducible COX-2. We show here for the first time that a stilbene, resveratrol, induces nuclear accumulation of COX-2 protein in human breast cancer MCF-7 and MDA-MB-231 cell cultures. The induction of COX-2 accumulation by resveratrol is mitogen-activated protein kinase (MAPK; extracellular signal–regulated kinase 1/2)- and activator protein 1- dependent. Nuclear COX-2 in resveratrol-treated cells colocalizes with Ser15-phosphorylated p53 and with p300, a coactivator for p53-dependent gene expression. The interaction of COX-2, p53, and p300, as well as resveratrol-induced apoptosis, was inhibited by a MAPK activation inhibitor, PD98059. A specific inhibitor of COX-2, NS398, and small interfering RNA knockdown of COX-2 were associated with reduced p53 phosphorylation and consequent decrease in p53-dependent apoptosis in resveratrol-treated cells. We conclude that nuclear accumulation of COX-2 can be induced by resveratrol and that the COX has a novel intranuclear colocalization with Ser15-phosphorylated p53 and p300, which facilitates apoptosis in resveratrol-treated breast cancer cells. [Mol Cancer Ther 2006;5(8):2034–42]

Thyroid hormone promotes the phosphorylation of STAT3 and potentiates the action of epidermal growth factor in cultured cells

We have examined the effects of l-thyroxine (T4) on the activation of signal transducer and activator of transcription 3 (STAT3) and on the STAT3-dependent induction of c-Fos expression by epidermal growth factor (EGF). T4, at a physiological concentration of 100 nM, caused tyrosine phosphorylation and nuclear translocation (i.e. activation) of STAT3 in HeLa cells in as little as 10-20 min. Activation by T4 of STAT3 was maximal at 30 min (15+/-4-fold enhancement; mean+/-S.E.M.) in 18 experiments. This effect was reproduced by T4-agarose (100 nM) and blocked by CGP 41251, genistein, PD 98059 and geldanamycin, inhibitors of protein kinase C (PKC), protein tyrosine kinase (PTK), mitogen-activated protein kinase (MAPK) kinase and Raf-1 respectively. Tyrosine-phosphorylated MAPK also appeared in nuclear fractions within 10 min of treatment with T4. In the nuclear fraction of T4-treated cells, MAPK immunoprecipitate also contained STAT3. The actions of T4 were similar in HeLa and CV-1 cells, which lack thyroid hormone receptor (TR), and in TR-replete skin fibroblasts (BG-9). T4 also potentiated the EGF-induced nuclear translocation of activated STAT1alpha and STAT3 and enhanced the EGF-stimulated expression of c-Fos. Hormone potentiation of EGF-induced signal transduction and c-Fos expression was inhibited by CGP 41251, geldanamycin and PD 98059. Therefore the non-genomically induced activation by T4 of STAT3, and the potentiation of EGF by T4, require activities of PKC, PTK and an intact MAPK pathway.

Androgen-induced human breast cancer cell proliferation is mediated by discrete mechanisms in estrogen receptor-α-positive and -negative breast cancer cells

Androgens have important physiological effects in women. Not only are they the precursor hormones for estrogen biosynthesis in the ovaries and extragonadal tissues, but also act directly via androgen receptors (ARs) throughout the body. Studies of the role of androgens on breast cancer development are controversial and the mechanisms involved are not fully understood. In this report we demonstrate that a non-aromatizable androgen metabolite, dihydrotestosterone (DHT), stimulated cell proliferation in vitro of both estrogen receptor-alpha (ER-alpha)-positive MCF-7 cells and ER-alpha-negative MDA-MB-231 human breast cancer cells. A contribution of ER to the proliferative effect of DHT in MCF-7 cells was supported by actions of small interfering RNA (siRNA) ER-alpha transfection and of the specific inhibitor of ER, ICI 182,780 to block DHT-induced proliferation. A contribution of the possible conversion of DHT to androstane-3alpha, 17beta-diol was not excluded in these MCF-7 cell studies. In MDA-MB-231 cells, a novel mechanism was implicated, in that anti-integrin alphavbeta3 or an Arg-Gly-Asp (RGD) peptide targeted at a small molecule binding domain of the integrin eliminated the DHT effect on cell proliferation. Anti-integrin alphavbeta3 did not affect DHT action on MCF-7 cells. A contribution from classical androgen receptor to the DHT effect in each cell line was excluded. A proliferative DHT signal is transduced in both ER-alpha-positive and ER-alpha-negative breast cancer cells, but by discrete mechanisms.

The combination of tetraiodothyroacetic acid and cetuximab inhibits cell proliferation in colorectal cancers with different K-ras status

Thyroid hormone induces cancer cell proliferation through its cell surface receptor integrin αvβ3. Acting via integrin αvβ3, the deaminated T4 analog tetraiodothyroacetic acid (tetrac), and its nanoparticle formulation nano-diamino-tetrac (NDAT) could inhibit cell proliferation and xenograft growth. In this study, we investigated the T4 effects on proliferation in colorectal cancer cell lines based on the proliferation marker expressions at both mRNA and protein levels. The effects of tetrac/NDAT, the monoclonal anti-EGFR antibody cetuximab, and their combinations on colorectal cancer cell proliferation were examined according to the relevant gene expression profiles and cell count analysis. The results showed that T4 significantly enhanced PCNA, Cyclin D1 and c-Myc levels in both K-ras wild type HT-29 and mutant HCT 116 cells. In HCT 116 cells, the combination of NDAT and cetuximab significantly suppressed the mRNA expressions of proliferative genes PCNA, Cyclin D1, c-Myc and RRM2 raised by T4 compared to cetuximab alone. In addition, T4-suppressed mRNA expressions of pro-apoptotic genes p53 and RRM2B could be significantly elevated by the combination of NDAT and cetuximab compared to cetuximab alone. In the K-ras mutant HCT 116 cells, but not in the K-ras wild type COLO 205 cells, the combinations of tetrac/NDAT and cetuximab significantly reduced cell proliferation compared to cetuximab alone. In conclusion, T4 promoted colorectal cancer cell proliferation which could be repressed by tetrac and NDAT. The combinations of tetrac/NDAT and cetuximab potentiated cetuximab actions in K-ras mutant colorectal cancer cells.

Biological Mechanisms by Which Antiproliferative Actions of Resveratrol Are Minimized

Preclinical and clinical studies have offered evidence for protective effects of various polyphenol-rich foods against cardiovascular diseases, neurodegenerative diseases, and cancers. Resveratrol is among the most widely studied polyphenols. However, the preventive and treatment effectiveness of resveratrol in cancer remain controversial because of certain limitations in existing studies. For example, studies of the activity of resveratrol against cancer cell lines in vitro have often been conducted at concentrations in the low μM to mM range, whereas dietary resveratrol or resveratrol-containing wine rarely achieve nM concentrations in the clinic. While the mechanisms underlying the failure of resveratrol to inhibit cancer growth in the intact organism are not fully understood, the interference by thyroid hormones with the anticancer activity of resveratrol have been well documented in both in vitro and xenograft studies. Thus, endogenous thyroid hormones may explain the failure of anticancer actions of resveratrol in intact animals, or in the clinic. In this review, mechanisms involved in resveratrol-induced antiproliferation and effects of thyroid hormones on these mechanisms are discussed.

Enhancement by Nano-Diamino-Tetrac of Antiproliferative Action of Gefitinib on Colorectal Cancer Cells: Mediation by EGFR Sialylation and PI3K Activation

Drug resistance complicates the clinical use of gefitinib. Tetraiodothyroacetic acid (tetrac) and nano-diamino-tetrac (NDAT) have been shown in vitro and in xenografts to have antiproliferative/angiogenic properties and to potentiate antiproliferative activity of other anticancer agents. In the current study, we investigated the effects of NDAT on the anticancer activities of gefitinib in human colorectal cancer cells. β-Galactoside α-2,6-sialyltransferase 1 (ST6Gal1) catalyzes EGFR sialylation that is associated with gefitinib resistance in colorectal cancers, and this was also investigated. Gefitinib inhibited cell proliferation of HT-29 cells (K-ras wild-type), and NDAT significantly enhanced the antiproliferative action of gefitinib. Gefitinib inhibited cell proliferation of HCT116 cells (K-ras mutant) only in high concentration, and this was further enhanced by NDAT. NDAT enhancedd gefitinib-induced antiproliferation in gefitinib-resistant colorectal cancer cells by inhibiting ST6Gal1 activity and PI3K activation. Furthermore, NDAT enhanced gefitinib-induced anticancer activity additively in colorectal cancer HCT116 cell xenograft-bearing nude mice. Results suggest that NDAT may have an application with gefitinib as combination colorectal cancer therapy.