Voltage-gated Na+ channels (VGSCs) are membrane proteins which are normally expressed in excitable cells but have also been detected in cancer cells, where they are thought to be involved in malignancy progression. In this study we examined the ion current and expression profile of VGSC (Nav1.5) in estrogen receptor (ER)-positive (MCF-7) and silenced (pII) breast cancer cells and its possible influence on their proliferation, motility and invasion. VGSC currents were analysed by whole cell patch clamp recording. Nav1.5 expression and localization, in response to EGF stimulation, was examined by western blotting and immunofluorescence respectively. Cell invasion (under-agarose and Matrigel assays), motility (wound healing assay) and proliferation (MTT assay) were assessed in pII cells in response to VGSC blockers, phenytoin (PHT) and tetrodotoxin (TTX), or by siRNA knockdown of Nav1.5. The effect of PHT and TTX on modulating EGF-induced phosphorylation of Akt and ERK1/2 was determined by western blotting. Total matrix metalloproteinase (MMP) was determined using a fluorometric-based activity assay. The level of various human proteases was detected by using proteome profiler array kit. VGSC currents were detected in pII cells, but were absent in MCF-7. Nav1.5 showed cytoplasmic and perinuclear expression in both MCF-7 and pII cells, with enhanced expression upon EGF stimulation. Treatment of pII cells with PHT, TTX or siRNA significantly reduced invasion towards serum components and EGF, in part through reduction of P-ERK1/2 and proteases such as cathepsin E, kallikrein-10 and MMP-7, as well as total MMP activity. At high concentrations, PHT inhibited motility while TTX reduced cell proliferation. Pharmacological or genetic blockade of Nav1.5 may serve as a potential anti-metastatic therapy for breast cancer.

Curcumin displays anticancer properties; however, some issues with the drug delivery mode limit its therapeutic use. Although reformulation and derivatization of curcumin have improved its bioavailability, curcumin derivatives may not retain the same anticancer properties as the parent compound. The present study investigated the anticancer properties of two curcumin complexes, the iron-curcumin [Fe(Cur) 3 ] and boron-curcumin [B(Cur) 2 ] complexes, in the MDA-MB-231 breast cancer cell line. The cellular localization of curcumin, B(Cur) 2 and Fe(Cur) 3 was determined by fluorescence microscopy. Cell proliferation, migration and invasion were also analysed. Furthermore, apoptosis-associated proteins were detected by using a proteome profiler array, and ion channel gene expression was analysed by reverse transcription-quantitative PCR. The results demonstrated that the three compounds were localized in the perinuclear and cytoplasmic regions of the cell, and displayed cytotoxicity with IC 50 values of 25, 35 and 8 µM for curcumin, B(Cur) 2 and Fe(Cur) 3 , respectively. In addition, the three compounds inhibited cell invasion, whereas only curcumin and B(Cur) 2 inhibited cell migration. Furthermore, cell exposure to curcumin resulted in an increase in the relative expression of the two key proapoptotic proteins, cytochrome c and cleaved caspase-3, as well as the antiapoptotic protein haem oxygenase-1. In addition, curcumin increased the expression levels of the voltage-gated potassium channels Kv2.1 and Kv3.2. Similarly, the expression levels of the chloride channel bestrophin-1 and the calcium channel coding gene calcium voltage-gated channel auxiliary subunit γ4 were increased following exposure to curcumin. Taken together, these results indicated that Fe(Cur) 3 and B(Cur) 2 may display similar anticancer properties as curcumin, suggesting that chemical complexation may be considered as a strategy for improving the potency of curcumin in the treatment of breast cancer.

Breast cancer is the most common cancer diagnosed among females worldwide. Although breast cancer survival has largely improved in the past 30 years, it remains highly heterogeneous in its response to treatment. Triple-negative breast cancer (TNBC) is a subtype of breast cancer that lacks the expression of the estrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor-2 (Her2). While TNBC may initially be responsive to chemotherapy, recurrence and subsequent high mortality rates are frequently reported. Studies have shown curcumin and its derivatives to be effective against TNBC cell lines in vitro. To improve its anti-cancer effects, we have synthesized Fe3+–curcumin (Fe–Cur3) and Cu2+–curcumin (CD) complexes and investigated them experimentally. Further, CD was encapsulated into a poly(styrene)-co-maleic acid (SMA) micelle to enhance its stability. We assessed the cytotoxicity of these formulations both in vitro and in vivo. SMA–CD demonstrated dose-dependent cytotoxicity and abolished TNBC tumor growth in vivo. The encapsulation of the curcumin–copper complex improved its anti-cancer activity without overt adverse effects in a murine model of TNBC. These results provide evidence and insights into the value of nanoformulations in enhancing drug-delivery and increasing the potential therapeutic efficacy of curcumin derivatives.

No abstract

Cryoablation is an emerging type of treatment for cancer. The sensitization of tumors using cryosensitizing agents prior to treatment enhances ablation efficiency and may improve clinical outcomes. Water efflux, which is regulated by aquaporin channels, contributes to cancer cell damage achieved through cryoablation. An increase in aquaporin (AQP) 3 is cryoprotective, whereas its inhibition augments cryodamage. The present study aimed to investigate aquaporin (AQP1, AQP3 and AQP5) gene expression and cellular localization in response to cryoinjury. Cultured breast cancer cells (MDA-MB-231 and MCF-7) were exposed to freezing to induce cryoinjury. RNA and protein extracts were then analyzed using reverse transcription-quantitative PCR and western blotting, respectively. Localization of aquaporins was studied using immunocytochemistry. Additionally, cells were transfected with small interfering RNA to silence aquaporin gene expression and cell viability was assessed using the Sulforhodamine B assay. Cryoinjury did not influence gene expression of AQPs, except for a 4-fold increase of AQP1 expression in MDA-MD-231 cells. There were no clear differences in AQP protein expression for either cell lines upon exposure to frozen and non-frozen temperatures, with the exception of fainter AQP5 bands for non-frozen MCF-7 cells. The exposure of cancer cells to freezing temperatures altered the localization of AQP1 and AQP3 proteins in both MCF-7 and MDA-MD-231 cells. The silencing of AQP1, AQP3 and AQP5 exacerbated MDA-MD-231 cell damage associated with freezing compared with control siRNA. This was also observed with AQP3 and AQP5 silencing in MCF-7 cells. Inhibition of aquaporins may potentially enhance cryoinjury. This cryosensitizing process may be used as an adjunct to breast cancer cryotherapy, especially in the border area targeted by cryoablation where freezing temperatures are not cold enough to induce cellular damage.