Artificial structures made of stacked two-dimensional crystals have recently been the focus of intense research activity. As in twisted or stacked graphene layers, these structures can show unusual behaviours and new phenomena. Among the various layered compounds that can be exfoliated, transition-metal dichalcogenides exhibit interesting properties governed by their structural symmetry and interlayer coupling, which are highly susceptible to stacking. Here, we obtain-by folding exfoliated MoS2 monolayers-MoS2 bilayers with different stacking orders, as monitored by second harmonic generation and photoluminescence. Appropriate folding can break the inversion symmetry and suppress interlayer hopping, evoking strong valley and spin polarizations that are not achieved in natural MoS2 bilayers of Bernal stacking. It can also enlarge the indirect bandgap by more than 100 meV through a decrease in the interlayer coupling. Our work provides an effective and versatile means to engineer transition-metal dichalcogenide materials with desirable electronic and optical properties.

BackgroundBreast cancer accounts for nearly a quarter of all cancers in women worldwide, and more than 90% of women diagnosed with breast cancer undergo mastectomy or breast-conserving surgery. Retrospective clinical studies have suggested that use of regional anesthesia leads to improved patient outcomes. Laboratory studies have reported that breast cancer cells are inhibited by some local anesthetics at millimolar concentration. Here, we present a comprehensive analysis of the effects of six common local anesthetics on two human breast cancer cell lines. We used concentrations ranging from those corresponding to plasma levels during regional block by local anesthetic (plasma concentration) to those corresponding to direct infiltration of local anesthetic.MethodsHuman breast cancer cell lines, MDA-MB-231 and MCF7, were incubated with each of six local anesthetics (lidocaine, mepivacaine, ropivacaine, bupivacaine, levobupivacaine, and chloroprocaine) (10 μM ~ 10 mM) for 6 to 72 h. Assays for cell viability, cytotoxicity, migration, and cell cycle were performed.ResultsHigh concentrations (> 1 mM) of local anesthetics applied to either MDA-MB-231 or MCF7 cells for 48 h significantly inhibited cell viability and induced cytotoxicity. At plasma concentrations (~ 10 μM) for 72 h, none of the local anesthetics affected cell viability or migration in either cell line. However, at 10 × plasma concentrations, 72-h exposure to bupivacaine, levobupivacaine or chloroprocaine inhibited the viability of MDA-MB-231 cells by > 40% (p < 0.001). Levobupivacaine also inhibited the viability of MCF7 cells by 50% (p < 0.001). None of the local anesthetics affected the viability of a non-cancerous breast cell line, MCF10A. MDA-MB-231 cell migration was inhibited by 10 × plasma concentrations of levobupivacaine, ropivacaine or chloroprocaine and MCF7 cell migration was inhibited by mepivacaine and levobupivacaine (p < 0.05). Cell cycle analysis showed that the local anesthetics arrest MDA-MB-231 cells in the S phase at both 1 × and 10 × plasma concentrations.ConclusionsLocal anesthetics at high concentrations significantly inhibited breast cancer cell survival. At 10 × plasma concentrations, the effect of local anesthetics on cancer cell viability and migration depended on the exposure time, specific local anesthetic, specific measurement endpoint and specific cell line.

Breast cancer is the second leading cause of cancer death in women. Surgery is the first line of treatment for breast cancer. Retrospective clinical studies suggest that the type of anesthesia administered during oncological surgery may influence patient outcome. Propofol, the widely used intravenous anesthetic agent, may lead to better outcomes compared to volatile anesthetics. Here we review the literature on the effect of propofol in breast cancer cells, the immune system, pain management, and patient outcomes. Evidence from the study of breast cancer cell lines suggests that high concentrations of propofol have both anti-tumor and pro-tumor effects. Propofol and volatile anesthetics have different effects on the immune system. Propofol has also been shown to reduce the development and severity of acute and chronic pain following surgery. Although a retrospective study that included many types of cancer indicated that propofol increases the long-term survival of patients following surgery, the evidence for this in breast cancer is weak. It has been shown that Propofol combined with paravertebral block led to change of serum composition that affects the breast cancer cell behaviors and natural killer cell activity. Prospective studies are in progress and will be finished within 5 years. The existing evidence is not sufficient to warrant changes to current anesthetic management. Further research is needed to clarify the mechanisms by which propofol affects cancer cells and the immune system.

The divalent cation-selective channel transient receptor potential melastatin 7 (TRPM7) channel was shown to affect the proliferation of some types of cancer cell. However, the function of TRPM7 in the viability of breast cancer cells remains unclear. Here we show that TRPM inhibitors suppressed the viability of TRPM7-expressing breast cancer cells. We first demonstrated that the TRPM7 inhibitors 2-aminoethyl diphenylborinate (2-APB), ginsenoside Rd (Gin Rd), and waixenicin A preferentially suppressed the viability of human embryonic kidney HEK293 overexpressing TRPM7 (HEK-M7) cells over wildtype HEK293 (WT-HEK). Next, we confirmed the effects of 2-APB on the TRPM7 channel functions by whole-cell currents and divalent cation influx. The inhibition of the viability of HEK-M7 cells by 2-APB was not mediated by the increase in cell death but by the interruption of the cell cycle. Similar to HEK-M7 cells, the viability of TRPM7-expressing human breast cancer MDA-MB-231, AU565, and T47D cells were also suppressed by 2-APB by arresting the cell cycle in the S phase. Furthermore, in a novel TRPM7 knock-out MDA-MB-231 (KO-231) cell line, decreased divalent influx and reduced proliferation were observed compared to the wildtype MDA-MB-231 cells. 2-APB and Gin Rd preferentially suppressed the viability of wildtype MDA-MB-231 cells over KO-231 by affecting the cell cycle in wildtype but not KO-231 cells. Our results suggest that TRPM7 regulates the cell cycle of breast cancers and is a potential therapeutic target.

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