Tamoxifen inhibits growth, migration, and invasion of human follicular and papillary thyroid cancer cells in vitro and in vivo

Sex Bias in Differentiated Thyroid Cancer

Differentiated thyroid cancers are more frequent in women than in men. These different frequencies may depend on differences in patient's behavior and in thyroid investigations. However, an impact on sexual hormones is likely, although this has been insufficiently elucidated. Estrogens may increase the production of mutagenic molecules in the thyroid cell and favor the proliferation and invasion of tumoral cells by regulating both the thyrocyte enzymatic machinery and the inflammatory process associated with tumor growth. On the other hand, the worse prognosis of thyroid cancer associated with the male gender is poorly explained.

Tamoxifen and oxidative stress: an overlooked connection

Tamoxifen is the gold standard drug for the treatment of breast cancer in pre and post-menopausal women. Its journey from a failing contraceptive to a blockbuster is an example of pharmaceutical innovation challenges. Tamoxifen has a wide range of pharmacological activities; a drug that was initially thought to work via a simple Estrogen receptor (ER) mechanism was proven to mediate its activity through several non-ER mechanisms. Here in we review the previous literature describing ER and non-ER targets of tamoxifen, we highlighted the overlooked connection between tamoxifen, tamoxifen apoptotic effects and oxidative stress.

Notch1 Signaling Regulates the Aggressiveness of Differentiated Thyroid Cancer and Inhibits SERPINE1 Expression

PURPOSE

Notch1, a transmembrane receptor, has been recently shown to aid in the determination of thyroid cell fate associated with tumorigenesis. This study aimed to investigate the clinical relevance of Notch1 and its role in the regulation of differentiated thyroid cancer (DTC) behavior.

EXPERIMENTAL DESIGN

We examined Notch1 expression level and its relationship with clinicopathologic features and outcomes of DTC. Notch1 intracellular domain (NICD) was further characterized both in vitro and in vivo by gain-of-function assays using an inducible system.

RESULTS

Notch1 expression levels were downregulated in primary DTC tissue samples compared with contralateral nontumor and benign thyroid tissues. Decreased Notch1 expression in DTC was associated with advanced patient age (P = 0.032) and the presence of extrathyroidal invasion (P = 0.005). Patients with lower Notch1 expression had a significantly higher recurrence rate (P = 0.038). Restoration of NICD in a stably doxycycline-inducible metastatic DTC cell line reduced cell growth and migration profoundly. Using an orthotopic thyroid cancer model, NICD induction significantly reduced the growth of the primary thyroid tumor and inhibited the development of lung metastasis. Serpin peptidase inhibitor, clade E, member 1 (SERPINE1) was discovered by microarray as the most significant gene downregulated by NICD. Further validation showed that the induction of NICD reduced SERPINE1 expression in a dose-dependent manner, whereas restoration of a relative higher level of SERPINE1 was observed with NICD back to minimal level. In addition, SERPINE1 knock-down inhibited DTC cell migration.

CONCLUSIONS

Notch1 regulates the aggressive phenotypes of DTC, which could be mediated by SERPINE1 inhibition. Notch1/SERPINE1 axis warrants further investigation as a novel therapeutic target for advanced DTC. Clin Cancer Res; 22(14); 3582-92. ©2016 AACR.

Tamoxifen non-estrogen receptor mediated molecular targets

Recent experimental studies revealing new biological effects of tamoxifen on tumor cells both expressing and not expressing different types of estrogen receptors (ERα and ERβ) show new aspects of a seemingly well known agent. This review describes tamoxifen targets, the blocking of which leads to inhibition of tumor cell growth and angiogenesis, stimulation of programmed cell death (apoptosis, autophagia and necrosis), inhibition of multidrug resistance, invasion and metastasis. Since outcomes of tamoxifen action on cells are prognostically good from the point of view of both tumor growth/metastasis inhibition and tumor response to drug therapy, the authors believe this is an extremely important addition to tamoxifen antiestrogenic effect. Arguments are provided to consider the strategy of long-term tamoxifen treatment proposed by Professor Craig V. Jordan in the 1970s that is also applicable to the treatment of other tumors. This is, first of all, the fact that expression of estrogen receptor-beta that can also be targeted by tamoxifen therapy in solid tumors of practically all known sites and histologies. The authors believe that molecular biological screening of patients with respect to expression of tamoxifen cellular targets other than ERα and ERβ is needed to use to the full all tamoxifen biological activities other than modulation of estrogen receptors during long-term adjuvant therapy for cancers of various sites.

Innovative in vitro chemo-hormonal drug therapy for refractory thyroid carcinomas

More than 95% of the thyroid carcinomas are well differentiated types showing favorable prognosis. However, only a few therapeutic options are available to treat the patients with undifferentiated thyroid carcinomas, especially with refractory thyroid carcinomas that are not amenable to surgery or radioiodine ablation. We investigated the anticancer effects of 20 chemotherapy and hormonal therapy drugs on 8 thyroid carcinoma cell lines. In vitro chemosensitivity was tested using the adenosine-triphosphate-based chemotherapy response assay (ATP-CRA). The tumor inhibition rate (TIR; or cell death rate) or half maximal inhibitory concentration (IC(50)) was analyzed to interpret the results. Of the 12 chemotherapy drugs, etoposide (178.9 index value in follicular carcinoma cell line) and vincristine (211.7 in Hürthle cell carcinoma cell line) were the most active drugs showing the highest chemosensitivity, and of the 8 additional drugs, trichostatin A (0.03 µg/mL IC(50) in follicular carcinoma cell line) showed favorable outcome having the anticancer effect. In our study, the result of etoposide and vincristine show evidence as active anticancer drugs in thyroid carcinoma cell lines and trichostatin A seems be the next promising drug. These drugs may become an innovative therapy for refractory thyroid carcinomas in near future.

Differential regulation of somatostatin receptors 1 and 2 mRNA and protein expression by tamoxifen and estradiol in breast cancer cells

Somatostatin (SST) inhibition of hormone hypersecretion from tumors is mediated by somatostatin receptors (SSTRs). SSTRs also play an important role in controlling tumor growth through specific antiproliferative actions. These receptors are well expressed in numerous normal and tumor tissues and are susceptible to regulation by a variety of factors. Estradiol, a potent trophic and mitogenic hormone in its target tissues, is known to modulate the expression of SST and its receptors. Accordingly, in the present study, we determined the effects of tamoxifen, a selective estrogen receptor (ER) modulator (SERM), and estradiol on SSTR1 and SSTR2 expression at the mRNA and protein levels in ER-positive and -negative breast cancer cells. We found that SSTR1 was upregulated by tamoxifen in a dose-dependent manner but no effect was seen with estradiol. In contrast, SSTR2 was upregulated by both tamoxifen and estradiol. Combined treatment caused suppression of SSTR1 below control levels but had no significant effect on SSTR2. Treatment with SSTR1-specific agonist was significantly more effective in suppressing cell proliferation of cells pre-treated with tamoxifen. Taking these data into consideration, we suggest that tamoxifen and estradiol exert variable effects on SSTR1 and SSTR2 mRNA and protein expression and distributional pattern of the receptors. These changes are cell subtype-specific and affect the ability of SSTR agonists to inhibit cell proliferation.

Modulation of glioma cell migration and invasion using Cl(-) and K(+) ion channel blockers

Human malignant gliomas are highly invasive tumors. Mechanisms that allow glioma cells to disseminate, migrating through the narrow extracellular brain spaces are poorly understood. We recently demonstrated expression of large voltage-dependent chloride (Cl(-)) currents, selectively expressed by human glioma cells in vitro and in situ (Ullrich et al., 1998). Currents are sensitive to several Cl(-) channel blockers, including chlorotoxin (Ctx), (Ullrich and Sontheimer; 1996; Ullrich et al; 1996), tetraethylammonium chloride (TEA), and tamoxifen (Ransom and Sontheimer, 1998). Using Transwell migration assays, we show that blockade of glioma Cl(-) channels specifically inhibits tumor cell migration in a dose-dependent manner. Ctx (5 microM), tamoxifen (10 microM), and TEA (1 mM) also prevented invasion of human glioma cells into fetal rat brain aggregates, used as an in vitro model to assess tumor invasiveness. Anion replacement studies suggest that permeation of chloride ions through glioma chloride channel is obligatory for cell migration. Osmotically induced cell swelling and subsequent regulatory volume decrease (RVD) in cultured glioma cells were reversibly prevented by 1 mM TEA, 10 microM tamoxifen, and irreversibly blocked by 5 microM Ctx added to the hypotonic media. Cl(-) fluxes associated with adaptive shape changes elicited by cell swelling and RVD in glioma cells were inhibited by 5 microM Ctx, 10 microM tamoxifen, and 1 mM TEA, as determined using the Cl(-)-sensitive fluorescent dye 6-methoxy-N-ethylquinolinium iodide. Collectively, these data suggest that chloride channels in glioma cells may enable tumor invasiveness, presumably by facilitating cell shape and cell volume changes that are more conducive to migration and invasion.

Receptor-mediated stimulation of lipid signalling pathways in CHO cells elicits the rapid transient induction of the PDE1B isoform of Ca2+/calmodulin-stimulated cAMP phosphodiesterase

Chinese hamster ovary cells (CHO cells) do not exhibit any Ca2+/calmodulin-stimulated cAMP phosphodiesterase (PDE1) activity. Challenge of CHO cells with agonists for endogenous P2-purinoceptors, lysophosphatidic acid receptors and thrombin receptors caused a similar rapid transient induction of PDE1 activity in each instance. This was also evident on noradrenaline challenge of a cloned CHO cell line transfected so as to overexpress alpha 1B-adrenoceptors. This novel PDE1 activity appeared within about 15 min of exposure to ligands, rose to a maximum value within 30 min to 1 h and then rapidly decreased. In each case, the expression of novel PDE1 activity was blocked by the transcriptional inhibitor actinomycin D. Challenge with insulin of either native CHO cells or a CHO cell line transfected so as to overexpress the human insulin receptor failed to induce PDE1 activity. Reverse transcriptase-PCR analyses, using degenerate primers able to detect the PDE1C isoform, did not amplify any fragment from RNA preparations of CHO cells expressing PDE1 activity, although they did so from the human thyroid carcinoma FTC133 cell line. Reverse transcriptase-PCR analyses, using degenerate primers able to detect the PDE1A and PDE1B isoforms, successfully amplified a fragment of the predicted size from RNA preparations of both CHO cells expressing PDE1 activity and human Jurkat T-cells. Sequencing of the PCR products, generated using the PDE1A/B primers, yielded a novel sequence which, by analogy with sequences reported for bovine and murine PDE1B forms, suggests that the PDE1 species induced in CHO cells through protein kinase C activation and that expressed in Jurkat T-cells are PDE1B forms.