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Oxytocin (OT) inhibits the proliferation of breast-cancer cells in vitro via a specific G-coupled receptor. To elucidate the intracellular mechanism involved in this biological effect, different G-coupled receptor mediators have been investigated in untreated and OT-treated MDA-MB231 breast-carcinoma cells. In these cells, after OT treatment, a significant cAMP increase was observed using a radioimmunoassay procedure, whereas the Ca2+ (determined with the fluorescent probe fura-2) and the inositol phosphate (determined after cell labeling with myo(2-(3)H)-inositol) concentrations were not modified, contrary to what has been observed in myometrial and myo-epithelial cells. The PKA inhibitor PKI (6-22) amide reverted the effect of OT, indicating that the anti-proliferative effect of the peptide is strictly related to the cAMP-PKA pathway. OT treatment did not modify tyrosine phosphorylation either. Our results indicate that in breast epithelial cells devoid of contractile activity, cAMP is the intracellular mediator of OT action, whereas the Ca2+-phosphoinositide system is not involved.

Oxytocin (OT) inhibits the proliferation of MCF7 estrogen-dependent human breast cancer cells, via specific OT receptors (OTR). Besides this effect, we report that OT modulates the expression of estrogen receptor alpha (ERalpha) in MCF7 cells, both at mRNA and protein level. Since the first 24 h of OT treatment the ERalpha mRNA levels are down-regulated; in contrast, ERalpha protein expression decreases at a later time. The reduced number of ERalpha goes in parallel to a temporary increase in the binding affinity of these receptors as well as to a significant increase in their estradiol (E2)-induced transcription activity. The increase in both binding affinity and transcriptional activity of ERalpha likely balances the reduction in the number of ERalpha binding sites, ruling out the hypothesis that part of the OT contrasting effect on E2-induced cell proliferation could depend on the reduced E2 binding to MCF7 cells and supporting the hypothesis of an exclusively direct OT-antimitogenic effect. This is the first evidence that OT modulates the expression of ERalpha receptors in human neoplastic cells.

Anaplastic thyroid carcinoma (ATC) has a rapidly fatal clinical course, being resistant to multimodal treatments. Microtubules, alpha/beta tubulin heterodimers, are crucial in cell signaling, division and mitosis and are among the most successful targets for anticancer therapy. Panobinostat (LBH589) is a potent deacetylase inhibitor acting both on histones and nonhistonic proteins, including alpha-tubulin. In vitro LBH589, evaluated in three ATC cell lines (BHT-101, CAL-62 and 8305C), resulted in impairment of cell viability, inhibition of colony formation, cell cycle arrest and apoptosis induction. Mechanistically, we showed that LBH589 not only affected the expression of p21 and cyclin D1, but markedly determined microtubule stabilization as evidenced by tubulin acetylation and increased tubulin polymerization. In a SCID xenograft model implanted with CAL-62 cells, the cytotoxic properties of LBH589 were confirmed. The drug at the dose of 20 mg/kg significantly impaired tumor growth (final tumor volume 2.5-fold smaller than in untreated animals); at this dose, no relevant side effects were observed. In tumors of treated animals, a significant reduction of Ki67, which was negatively correlated with tubulin acetylation, was observed. Moreover, acetyl-tubulin levels negatively correlated with tumor volume at sacrifice, reinforcing the opinion that tubulin acetylation has a role in the inhibition of tumor growth. In conclusion, LBH589, acting on both histones and nonhistonic proteins in anaplastic thyroid cancer, appears to be a promising therapeutic agent for the treatment of this kind of cancer which is known not to respond to conventional therapy

Context: Anaplastic thyroid cancer cells are characterized by a mesenchymal phenotype, as revealed by spindle-shaped cells and absent or reduced levels of E-cadherin. Epigenetic silencing is considered one of the leading mechanisms of E-cadherin impairment, which causes the acquisition of the invasive and metastatic phenotype of anaplastic thyroid cancer. Objectives: In this studyweinvestigated the effects of histone deacetylase inhibition on E-cadherin expression, cell motility, and invasion in anaplastic thyroid cancer cell cultures. Design: Three stabilized cell lines and primary cultures of anaplastic thyroid cancer were treated with various histone deacetylase inhibitors. After treatment, we evaluated histone acetylation by Western blotting and E-cadherin expression by RT-real time PCR. The proper localization of E-cadherin/β- catenin complex was assessed by immunofluorescence and Western blot. Transcription activity of β-catenin was measured by luciferase reporter gene and cyclin D1 expression. The effect on cell motility and invasion was studied both in vitro using scratch-wound and transwell invasion assays and in anaplastic thyroid carcinomas tumor xenografts in mice in vivo. Results: Histone deacetylase inhibition induced the E-cadherin expression and the proper membrane localization of the E-cadherin/β-catenin complex, leading to reduced cancer cell migration and invasion. Conclusions: We here demonstrate an additional molecular mechanism for the anticancer effect of histone deacetylase inhibition. The antiinvasive effect in addition to the cytotoxic activity of histone deacetylase inhibitors opens up therapeutic perspectives for the anaplastic thyroid tumor that does not respond to conventional therapy.