HER2 is overexpressed in 25–30% of breast cancers, and approximately 30% of HER2-positive breast cancers metastasize to the brain. Although the incidence of brain metastasis in HER2-positive breast cancer is high, previous studies have been mainly based on cell lines of the triple-negative subtype, and the molecular mechanisms of brain metastasis in HER2-positive breast cancer are unclear. In the present study, we performed intracranial injection using nine HER2-positive breast cancer cell lines to evaluate their proliferative activity in brain tissue. Our results show that UACC-893 and MDA-MB-453 cells rapidly proliferated in the brain parenchyma, while the other seven cell lines moderately or slowly proliferated. Among these nine cell lines, the proliferative activity in brain tissue was not correlated with either the HER2 level or the HER2 phosphorylation status. To extract signature genes associated with brain colonization, we conducted microarray analysis and found that these two cell lines shared 138 gene expression patterns. Moreover, some of these genes were correlated with poor prognosis in HER2-positive breast cancer patients. Our findings might be helpful for further studying brain metastasis in HER2-positive breast cancer.

Edited by Roger J. Colbran Sonic hedgehog (SHH) is important for organogenesis during development. Recent studies have indicated that SHH is also involved in the proliferation and transformation of astrocytes to the reactive phenotype. However, the mechanisms underlying these are unknown. Involvement of SHH signaling in calcium (Ca) signaling has not been extensively studied. Here, we report that SHH and Smoothened agonist (SAG), an activator of the signaling receptor Smoothened (SMO) in the SHH pathway, activate Ca oscillations in cultured murine hippocampal astrocytes. The response was rapid, on a minute time scale, indicating a noncanonical pathway activity. Pertussis toxin blocked the SAG effect, indicating an involvement of a G i coupled to SMO. Depletion of extracellular ATP by apyrase, an ATP-degrading enzyme, inhibited the SAG-mediated activation of Ca oscillations. These results indicate that SAG increases extracellular ATP levels by activating ATP release from astrocytes, resulting in Ca oscillation activation. We hypothesize that SHH activates SMO-coupled Gi in astrocytes, causing ATP release and activation of G q/11 -coupled P2 receptors on the same cell or surrounding astrocytes. Transcription factor activities are often modulated by Ca patterns; therefore, SHH signaling may trigger changes in astrocytes by activating Ca oscillations. This enhancement of Ca oscillations by SHH signaling may occur in astrocytes in the brain in vivo because we also observed it in hippocampal brain slices. In summary, SHH and SAG enhance Ca oscillations in hippocampal astrocytes, G i mediates SAG-induced Ca oscillations downstream of SMO, and ATP-permeable channels may promote the ATP release that activates Ca oscillations in astrocytes.

No abstract

Cholesterol is one of the most abundant molecules that constitutes the plasma membrane. The total cholesterol content in the brain is over 20%, and 50% of myelin is made up of cholesterol. In several neurodegenerative diseases, accumulation of free cholesterol in the extracellular space due to demyelination and neuronal death is suggested. However, the effect of free cholesterol in the brain parenchyma have not been focused. We found that cholesterol induces calcium oscillation in cultured astrocytes but not in neurons. The calcium oscillation lasted at least 4 hours. Removal of extracellular calcium decreased the oscillation frequency, but not totally blocked, while inhibitors against IP 3 receptor, calcium -ATPase and PLC blocked the calcium oscillation. Therefore, cholesterol induces calcium oscillation in astrocytes through the PLC-IP 3 pathway. Cholesterol treatment for 24 hours led cell death in neurons but not in astrocytes. The survival rate of astrocytes under cholesterol decreased when the calcium oscillation was suppressed. These results suggest that the calcium oscillation induced by cholesterol helps astrocytes to survive in high extracellular cholesterol condition, which may imply an astrocytic behavior under pathological conditions where extracellular cholesterol concentration is raised.

No abstract

Two observational surveys on the behavior of convenience store shoppers in Sapporo were conducted to investigate the effects of a charging system for plastic bags provided at registers implemented in July 2020. Specifically, Survey 1 aimed to examine: S1 -1) How did behaviors change after the implementation of the charging system? and S1 -2) Was there a difference in the refusal rates for plastic bags between the shops with the charging system and those without? Meanwhile, Survey 2 focused on S2). Could characteristics of those buying plastic bags after the charging system was implemented be identified? Study 1 was conducted from June through August 2020 and 554 samples were obtained, revealing a substantial difference in the refusal rates for plastic bags between the shops implementing a charging system and those without one. Study 2 was conducted in September 2020. The 4289 samples obtained revealed purchasing pattern characteristics related to plastic bag refusal rates: a) The number of people who brought reusable shopping bags was low overall; b) The refusal rate was lower for shoppers who bought bento (box lunch) or packed bowls/ dishes than for those who bought other products; and c) The refusal rate was lower when the clerks asked whether a plastic bag was required or not.