Comparison of tumor-associated YAP1 fusions identifies a recurrent set of functions critical for oncogenesis.

YAP1 is a transcriptional coactivator and the principal effector of the Hippo signaling pathway, which is causally implicated in human cancer. Several YAP1 gene fusions have been identified in various human cancers and identifying the essential components of this family of gene fusions has significant therapeutic value. Here, we show that the YAP1 gene fusions YAP1-MAMLD1, YAP1-FAM118B, YAP1-TFE3, and YAP1-SS18 are oncogenic in mice. Using reporter assays, RNA-seq, ChIP-seq, and loss-of-function mutations, we can show that all of these YAP1 fusion proteins exert TEAD-dependent YAP activity, while some also exert activity of the C'-terminal fusion partner. The YAP activity of the different YAP1 fusions is resistant to negative Hippo pathway regulation due to constitutive nuclear localization and resistance to degradation of the YAP1 fusion proteins. Genetic disruption of the TEAD-binding domain of these oncogenic YAP1 fusions is sufficient to inhibit tumor formation in vivo, while pharmacological inhibition of the YAP1-TEAD interaction inhibits the growth of YAP1 fusion-expressing cell lines in vitro. These results highlight TEAD-dependent YAP activity found in these gene fusions as critical for oncogenesis and implicate these YAP functions as potential therapeutic targets in YAP1 fusion-positive tumors.

Rates of pathologic nodal disease among cN0 and cN1 patients undergoing routine axillary ultrasound and neoadjuvant chemotherapy.

PURPOSE: Routine axillary ultrasound (AxUS) in patients receiving neoadjuvant chemotherapy (NAC) remains controversial. Here, we report rates of AxUS-detected nodal disease among patients with normal clinical exams, and rates of pathologic nodal disease after NAC based on method of nodal disease detection. METHODS: Clinicopathologic findings were prospectively collected for stage I-III breast cancer patients selected for NAC. All patients had pre-treatment AxUS, suspicious nodes were biopsied. The following four patient cohorts were examined: patients with suspicious exam or AxUS but negative biopsy (Suspicious cN0); those with normal exam and normal AxUS (Not Suspicious cN0); those with normal exam but suspicious AxUS and positive biopsy (AxUS-detected cN1); and those with abnormal exam and positive biopsy (exam-detected cN1). Sentinel (SLN) and non-sentinel lymph nodes (non-SLN) were evaluated by immunohistochemistry; nodal metastases of any size were considered positive. RESULTS: 500 patients were included. Of 310 patients with normal axillary exams, 160 had suspicious AxUS, 65 were biopsy-negative (Suspicious cN0) and 95/310 (30.6%) were biopsy-positive (AxUS-detected cN1). Of 190 with abnormal axillary exams, 166 were biopsy-proven node-positive (exam-detected cN1) and 24 were AxUS or biopsy-negative (Suspicious cN0). Rates of pathologic nodal disease were 20/150 (13.3%) among Not Suspicious cN0 patients, 12/89 (13.5%) among Suspicious cN0 (p = 0.97). Rates of residual nodal disease were 55/95 (57.9%) among AxUS-detected cN1 patients, 102/166 (61.4%) among exam-detected cN1 (p = 0.57). CONCLUSION: AxUS detected nodal disease in 30.6% of patients with normal clinical exams selected for NAC. Rates of pathologic nodal disease were similar among AxUS-detected and exam-detected cN1 patients.

Impact of the Histologic Pattern of Residual Tumor After Neoadjuvant Chemotherapy on Recurrence and Survival in Stage I-III Breast Cancer.

BACKGROUND: Additional risk-stratification measures are needed in breast cancer patients with residual disease after neoadjuvant chemotherapy (NAC). We aimed to describe oncologic outcomes in a modern cohort treated with NAC, and evaluate the prognostic value of histologic pattern of residual tumor. PATIENTS AND METHODS: We included patients with stage I-III breast cancer treated with NAC and surgery from 2004 to 2014. Histologic pattern of residual tumor was evaluated by central pathology review when slides were available. Multivariable Cox regression was performed to evaluate factors associated with locoregional recurrence (LRR), recurrence-free survival (RFS), and overall survival (OS). RESULTS: Among 975 patients, median follow-up was 74.0 months and 10-year rates of LRR, RFS, and OS were 9.8%, 67.6% and 74.4%, respectively. Biologic subtype, pathologic node-positive disease, and pathologic complete response (pCR) were associated with outcomes. Among 666 (68.3%) patients with central pathology review, pattern of residual disease was not significantly associated with LRR. However, both scattered residual tumor and no/minimal response relative to a concentric pattern of response were significantly associated with inferior RFS (scattered: hazard ratio 2.0, p = 0.015; no/minimal response: hazard ratio 2.2, p = 0.021) and OS (scattered: hazard ratio 2.2, p = 0.026; no/minimal response: hazard ratio 2.5, p = 0.023). This finding was most prominent in patients with triple-negative breast cancer. CONCLUSIONS: Patients with a scattered relative to concentric pattern of residual tumor after NAC had inferior RFS and OS, nearly as poor as those with no/minimal response. Histologic pattern of residual tumor may represent a novel prognostic measure, particularly in the triple-negative breast cancer population.

How Often Does Retrieval of a Clipped Lymph Node Change Adjuvant Therapy Recommendations? A Prospective, Consecutive, Patient Cohort Study.

BACKGROUND: Prior studies examining sentinel lymph node biopsy (SLNB) after neoadjuvant chemotherapy (NAC) for cN1 patients have demonstrated that 20% of biopsied, clipped lymph nodes (cLNs) are nonsentinel lymph nodes (non-SLNs). Our goal was to determine how often the cLN was a non-SLN among both cN0 and cN1 patients and how often cLN pathology impacted management. METHODS: Overall, 238 patients treated with NAC and surgery January 2019 to June 2020 were prospectively examined. Patients underwent routine axillary ultrasound, biopsy of suspicious nodes, and clip placement. Radioactive iodine-125 seed localization of the cLN was performed in cN1 patients only. Isolated tumor cells (ITCs) were considered node positive (ypN+) for both cN0 and cN1 cohorts. Chart review was performed to determine if cLNs were non-SLN and their ypN status. RESULTS: Of 118 cN0 patients, 115 of 118 (97%) underwent successful SLNB, 33 of whom had a cLN present; 21 of 33 (64%) cLNs were non-SLNs. Overall, 9 of 118 (8%) were ypN+; no cLN was ypN+ without additional +SLNs. Of 120 cN1 patients, 104 of 120 (87%) converted to cN0, 98 of 104 (94%) of which had attempted SLNB, and 95 of 98 (97%) successfully mapped. The cLN was a non-SLN in 18 of 95 (19%). Overall, 58 of 104 (56%) cN1 patients were ypN+. One patient had a positive cLN in the absence of +SLNs. This patient underwent axillary lymph node dissection (ALND); adjuvant treatment recommendations were unchanged. CONCLUSIONS: The cLN was a non-SLN in 19% of cN1 patients. cLN pathology did not impact adjuvant therapy recommendations, calling into question the utility of routinely clipping biopsied lymph nodes.

Clinico-pathologic predictors of patterns of residual disease following neoadjuvant chemotherapy for breast cancer.

Among breast cancer patients treated with neoadjuvant chemotherapy (NAC) who do not experience a pathologic complete response (pCR), the pattern of residual disease in the breast varies. Pre-treatment clinico-pathologic features that predict the pattern of residual tumor are not well established. To investigate this issue, we performed a detailed review of histologic sections of the post-treatment surgical specimens for 665 patients with stage I-III breast cancer treated with NAC followed by surgery from 2004 to 2014 and for whom slides of the post-NAC surgical specimen were available for review. This included 242 (36.4%) patients with hormone receptor (HR)+/HER2- cancers, 216 (32.5%) with HER2+ tumors, and 207 (31.1%) with triple negative breast cancer (TNBC). Slide review was blinded to pre-treatment clinico-pathologic features. pCR was achieved in 7.9%, 37.0%, and 37.7%, of HR+/HER2- cancers, HER2+ cancers, and TNBC respectively (p < 0.001). Among 389 patients with residual invasive cancer in whom the pattern of residual disease could be assessed, 287 (73.8%) had a scattered pattern and 102 (26.2%) had a circumscribed pattern. In both univariate and multivariate analyses, there was a significant association between tumor subtype and pattern of response. Among patients with HR+/HER2- tumors, 89.4% had a scattered pattern and only 10.6% had a circumscribed pattern. In contrast, among those with TNBC 52.8% had a circumscribed pattern and 47.2% had a scattered pattern (p < 0.001). In addition to subtype, histologic grade and tumor size at presentation were also significantly related to the pattern of residual disease in multivariate analysis, with lower grade and larger size each associated with a scattered response pattern (p = 0.002 and p = 0.01, respectively). A better understanding of the relationship between pre-treatment clinico-pathologic features of the tumor and pattern of residual disease may be of value for helping to guide post-chemotherapy surgical management.

Comparison of Breast Cancer Staging Systems After Neoadjuvant Chemotherapy.

BACKGROUND: No consensus exists for optimal staging following neoadjuvant chemotherapy (NAC). We compared the performance of the American Joint Committee on Cancer (AJCC) pathologic prognostic staging system, Residual Cancer Burden (RCB) Index, and the Neo-Bioscore in breast cancer patients after NAC. METHODS: Patients with stage I-III breast cancer who received NAC at Dana-Farber Cancer Institute from 2004 to 2014 were identified. Kaplan-Meier curves were used to estimate disease-free survival (DFS) and overall survival (OS), and model fits were compared by receiver operator characteristic (ROC) curve using the c-statistic and DeLong's test. RESULTS: Overall, 802 patients with a median age of 48 years received NAC. Most patients presented with cT2 (n = 470, 58.6%) and cN1 (n = 422, 52.6%) disease. The subtype was estrogen receptor (ER)- and/or progesterone receptor (PR)-positive/human epidermal growth factor receptor 2 (HER2)-negative in 296 (36.9%) patients, HER2-positive in 261 (32.5%) patients, and triple-negative in 245 (30.5%) patients. Median follow-up was 79.5 months. There were 174 recurrences (30 local, 25 regional, 145 distant), with 676 (76.8%) patients alive at last follow-up. AJCC pathologic prognostic staging and RCB had better discrimination for estimated 7-year DFS and OS compared with the Neo-Bioscore. The ROC c-statistics for DFS model fit were similar for AJCC pathologic prognostic stage (0.72) and RCB (0.71, p = non-significant); both had improved model fit versus the Neo-Bioscore (0.65, p < 0.01). The c-statistics for OS were 0.74, 0.71, and 0.70 for AJCC pathologic prognostic stage, RCB, and Neo-Bioscore, respectively (p = non-significant). CONCLUSIONS: These results validate the ability of these staging systems to stratify survival outcomes in NAC patients, with best discrimination achieved using AJCC pathologic prognostic stage or RCB.

Pharmaceutical procurement among public sector procurers in CARICOM.

OBJECTIVE: To examine multiple aspects of the medicines in CARICOM procurement markets, including manufacturer headquarters location, regulatory history, and type (innovator versus generic); the proportion of World Health Organization (WHO) essential medicines; and the most expensive medicines procured. METHODS: An analysis of procurement information from selected CARICOM procurers. Four public sector procurement lists were obtained based on public availability or sharing of data from public sector procurers. Analyses were based on parameters available or deduced from these data. RESULTS: The majority of products come from manufacturers headquartered in North America and Europe (63%-67%). The percentage of medicines procured from generic companies is 60%-87%; and 25%-50% of medicines procured are on the WHO Essential Medicines List. Wide price variations exist in the most expensive medicines purchased. CONCLUSIONS: The analysis identifies vulnerabilities and opportunities in the procurement situation of CARICOM states, particularly related to quality and rational use of medicines. This analysis represents a baseline that governments and other stakeholders can use in the future.

Models of endometriosis and their utility in studying progression to ovarian clear cell carcinoma.

Endometriosis is a common benign gynaecological condition affecting at least 10% of women of childbearing age and is characterized by pain--frequently debilitating. Although the exact prevalence is unknown, the economic burden is substantial (∼$50 billion a year in the USA alone) and it is associated with considerable morbidity. The development of endometriosis is inextricably linked to the process of menstruation and thus the models that best recapitulate the human disease are in menstruating non-human primates. However, the use of these animals is ethically challenging and very expensive. A variety of models in laboratory animals have been developed and the most recent are based on generating menstrual-like endometrial tissue that can be transferred to a recipient animal. These models are genetically manipulable and facilitate precise mechanistic studies. In addition, these models can be used to study malignant transformation in epithelial ovarian carcinoma. Epidemiological and molecular evidence indicates that endometriosis is the most plausible precursor of both clear cell and endometrioid ovarian cancer (OCCA and OEA, respectively). While this progression is rare, understanding the underlying mechanisms of transformation may offer new strategies for prevention and therapy. Our ability to pursue this is highly dependent on improved animal models but the current transgenic models, which genetically modify the ovarian surface epithelium and oviduct, are poor models of ectopic endometrial tissue. In this review we describe the various models of endometriosis and discuss how they may be applicable to developing our mechanistic understanding of OCCA and OEA.

Caring for a dying spouse at the end of life: 'It's one of the things you volunteer for when you get married': a qualitative study of the oldest carers' experiences.

BACKGROUND: older people aged 80 and over are increasingly providing end-of-life care to spouses at home and often do so for long periods of time, while also trying to manage their own illnesses and disabilities. Little of the research on older spousal carers has focussed on the oldest carers; hence, the needs of this particular population are not fully known. OBJECTIVE: to explore the experiences of the 'oldest carers' in caring for a dying spouse at home. METHODS: secondary analysis was undertaken on a subset of data from a larger qualitative interview study; this dataset comprised 17 interviews from participants aged 80 or over. Framework analysis methods were used, with items derived from the thematic analysis of the main study. RESULTS: the oldest carers in this subset demonstrated high levels of resilience and the ability to adapt to their caring role. Caring until death was accepted as an integral part of the commitment made to their partner as part of the 'wedding contract'. Carers felt they benefitted from the support provided by family, friends and care services; however, their own care needs were not always recognised by health and social care services. CONCLUSIONS: these findings underscore the complexity of the oldest carers' experiences and challenges in times of illness and end of life. Healthcare professionals should be alerted to the myriad ways caregiving is enacted in serious illness and seek opportunities for developing supportive interventions specifically for older carers.

Family carers providing support to a person dying in the home setting: A narrative literature review.

BACKGROUND: This study is based on people dying at home relying on the care of unpaid family carers. There is growing recognition of the central role that family carers play and the burdens that they bear, but knowledge gaps remain around how to best support them. AIM: The aim of this study is to review the literature relating to the perspectives of family carers providing support to a person dying at home. DESIGN: A narrative literature review was chosen to provide an overview and synthesis of findings. The following search terms were used: caregiver, carer, 'terminal care', 'supportive care', 'end of life care', 'palliative care', 'domiciliary care' AND home AND death OR dying. DATA SOURCES: During April-May 2013, Cumulative Index to Nursing and Allied Health Literature (CINAHL), MEDLINE, PsycINFO, Pubmed, Cochrane Reviews and Citation Indexes were searched. Inclusion criteria were as follows: English language, empirical studies and literature reviews, adult carers, perspectives of family carers, articles focusing on family carers providing end-of-life care in the home and those published between 2000 and 2013. RESULTS: A total of 28 studies were included. The overarching themes were family carers' views on the impact of the home as a setting for end-of-life care, support that made a home death possible, family carer's views on deficits and gaps in support and transformations to the social and emotional space of the home. CONCLUSION: Many studies focus on the support needs of people caring for a dying family member at home, but few studies have considered how the home space is affected. Given the increasing tendency for home deaths, greater understanding of the interplay of factors affecting family carers may help improve community services.

Impact of Intensity of Vascular Care Preceding Major Amputation Among Patients With Chronic Limb-Threatening Ischemia.

BACKGROUND: Lower-limb amputation rates in patients with chronic limb-threatening ischemia vary across the United States, with marked disparities in amputation rates by gender, race, and income status. We evaluated the association of patient, hospital, and geographic characteristics with the intensity of vascular care received the year before a major lower-limb amputation and how intensity of care associates with outcomes after amputation. METHODS: Using Medicare claims data (2016-2019), beneficiaries diagnosed with chronic limb-threatening ischemia who underwent a major lower-limb amputation were identified. We examined patient, hospital, and geographic characteristics associated with the intensity of vascular care received the year before amputation. Secondary objectives evaluated all-cause mortality and adverse events following amputation. RESULTS: Of 33 036 total Medicare beneficiaries undergoing major amputation, 7885 (23.9%) were due to chronic limb-threatening ischemia; of these, 4988 (63.3%) received low-intensity and 2897 (36.7%) received high-intensity vascular care. Mean age, 76.6 years; women, 38.9%; Black adults, 24.5%; and of low income, 35.2%. After multivariable adjustment, those of low income (odds ratio, 0.65 [95% CI, 0.58-0.72]; P<0.001), and to a lesser extent, men (odds ratio, 0.89 [95% CI, 0.81-0.98]; P=0.019), and those who received care at a safety-net hospital (odds ratio, 0.87 [95% CI, 0.78-0.97]; P=0.012) were most likely to receive low intensity of care before amputation. High-intensity care was associated with a lower risk of all-cause mortality 2 years following amputation (hazard ratio, 0.79 [95% CI, 0.74-0.85]; P<0.001). CONCLUSIONS: Patients who were of low-income status, and to a lesser extent, men, or those cared for at safety-net hospitals were most likely to receive low-intensity vascular care. Low-intensity care was associated with worse long-term event-free survival. These data emphasize the continued disparities that exist in contemporary vascular practice.

Bacterial defense systems exhibit synergistic anti-phage activity.

Bacterial defense against phage predation involves diverse defense systems acting individually and concurrently, yet their interactions remain poorly understood. We investigated >100 defense systems in 42,925 bacterial genomes and identified numerous instances of their non-random co-occurrence and negative association. For several pairs of defense systems significantly co-occurring in Escherichia coli strains, we demonstrate synergistic anti-phage activity. Notably, Zorya II synergizes with Druantia III and ietAS defense systems, while tmn exhibits synergy with co-occurring systems Gabija, Septu I, and PrrC. For Gabija, tmn co-opts the sensory switch ATPase domain, enhancing anti-phage activity. Some defense system pairs that are negatively associated in E. coli show synergy and significantly co-occur in other taxa, demonstrating that bacterial immune repertoires are largely shaped by selection for resistance against host-specific phages rather than negative epistasis. Collectively, these findings demonstrate compatibility and synergy between defense systems, allowing bacteria to adopt flexible strategies for phage defense.

NMDA receptor activation: two targets for two co-agonists.

Neuronal N-methyl-D-aspartate receptors (NMDARs) play a critical role in synaptic plasticity. Their activation requires not only binding of their ligand glutamate and membrane depolarization but also the presence of a co-agonist, glycine or D-serine. An increasing body of experimental evidence suggests that different populations of NMDARs could be gated by different co-agonists. Here we discuss how the spatial distribution of co-agonist sources and uptake mechanisms, together with diffusional properties of the synaptic environment, could shape NMDAR co-agonist supply and therefore NMDAR-dependent plasticity.

Wearable-Triggered Ecological Momentary Assessments Are Feasible in People With Advanced Cancer and Their Family Caregivers: Feasibility Study from an Outpatient Palliative Care Clinic at a Cancer Center.

Background: Emerging digital health approaches could play a role in better personalized palliative care. Aim: We conducted a feasibility study testing wearable sensor (WS)-triggered ecological momentary assessments (EMAs) and electronic patient-reported outcomes in community palliative care with patient-caregiver dyads. Design: All wore consumer-grade WS for five weeks. Sensor-detected "stress" (heart rate variability algorithm) that passed individualized thresholds triggered a short smartphone survey. Daily sleep surveys, weekly symptom surveys (Integrated Palliative care Outcome Scale), and a poststudy experience survey were conducted. Setting/Participants: Fifteen dyads (n = 30) were recruited from an outpatient palliative care clinic for people with cancer. Results: Daytime sensor wear-time had 73% adherence. Participants perceived value in this support. Quantity and severity of "stress" events were higher in patients. Sleep disturbance was similar but for different reasons: patients (physical symptoms) and caregivers (worrying about the patient). Conclusions: EMAs are feasible and valued in community palliative care.

Inequities in referrals to a breast cancer risk assessment and prevention clinic: a mixed methods study.

BACKGROUND: Inequitable access to personalized breast cancer screening and prevention may compound racial and ethnic disparities in outcomes. The Breast Cancer Personalized Risk Assessment, Education and Prevention (B-PREP) program, located within the Brigham and Women's Hospital (BWH) Comprehensive Breast Health Center (BHC), provides care to patients at high risk for developing breast cancer. We sought to characterize the differences between BWH primary care patients referred specifically to B-PREP for risk evaluation and those referred to the BHC for benign breast conditions. Through interviews with primary care clinicians, we sought to explore contributors to potentially inequitable B-PREP referral patterns. METHODS: We used electronic health record data and the B-PREP clinical database to identify patients referred by primary care clinicians to the BHC or B-PREP between 2017 and 2020. We examined associations with likelihood of referral to B-PREP for risk assessment. Semi-structured interviews were conducted with nine primary care clinicians from six clinics to explore referral patterns. RESULTS: Of 1789 patients, 78.0% were referred for benign breast conditions, and 21.5% for risk assessment. In multivariable analyses, Black individuals were less likely to be referred for risk than for benign conditions (OR 0.38, 95% CI:0.23-0.63) as were those with Medicaid/Medicare (OR 0.72, 95% CI:0.53-0.98; OR 0.52, 95% CI:0.27-0.99) and those whose preferred language was not English (OR 0.26, 95% CI:0.12-0.57). Interviewed clinicians described inconsistent approaches to risk assessment and variable B-PREP awareness. CONCLUSIONS: In this single-site evaluation, among individuals referred by primary care clinicians for specialized breast care, Black, publicly-insured patients, and those whose preferred language was not English were less likely to be referred for risk assessment. Larger studies are needed to confirm these findings. Interventions to standardize breast cancer risk assessment in primary care may improve equity.

Retrospective descriptive analysis of a managed care population with obesity.

OBJECTIVES: To reveal the extent of obesity in a single healthcare system and provide a blueprint for other health systems to perform similar analyses, this study describes characteristics and weight change patterns of patients classified with overweight and obesity at a large integrated delivery network (IDN) in the South-Central United States. METHODS: A descriptive, observational, retrospective study was conducted using electronic medical records and claims data. Patients were ≥18 years old, body mass index (BMI) ≥27 kg/m2, and continuously enrolled in the IDN plan for ≥6 months before and ≥12 months after the index date. Demographics, comorbidities, BMI, and weight were collected. Weight changes were assessed annually, and anti-obesity medications (AOM) use was also captured. RESULTS: A total of 36,430 eligible patients were identified. A subset of 22,712 patients was continuously enrolled for the entire study period (mean age: 57.2) and were primarily white (83.3%) and commercially insured (54.3%). Most patients were categorized as overweight (40.1%) or obesity class I (32.5%) at baseline. At years 1 and 4 post-index, patients who maintained index weight (±3%) was 56.2% and 37.0%, respectively, whereas weight gain (≥3% increase) was 23.7% and 33.3%, respectively. AOM use (1.1%) primarily consisted of phentermine-hydrochloride (n = 114, 0.5%) and orlistat (n = 115, 0.5%). CONCLUSIONS: An increasing proportion of patients gained weight over time, combined with low AOM use, emphasizing the need for weight-loss interventions in this population. Findings from this study provide a foundation for health systems to perform similar analyses.

Serial step sections at narrow intervals with immunohistochemistry are required for accurate histological assessment of sentinel lymph node biopsy in oral squamous cell carcinoma.

BACKGROUND: Sentinel lymph node (SLN) biopsy is an accurate staging modality in early oral squamous cell carcinoma (OSCC), but its accuracy relies on labor-intensive histopathology protocols. We sought to determine whether serial step sections with immunohistochemistry (SSSIHC) at narrow intervals of the entire SLN are required to accurately exclude metastasis. METHODS: Consecutive SLN biopsies over a 13-year period were retrospectively evaluated. If the index section was negative for carcinoma, the entire SLN was subjected to SSSIHC at 150 µm intervals. The first section level and total number of section levels to contain carcinoma were recorded. RESULTS: One hundred and eighteen SLN+ from 90 patients were included. SSSIHC upstaged the nodal status in 19.5% of patients. Metastasis was identified in 16.7% and 10.2% beyond section levels 4 and 6, respectively. Among SLNs requiring SSSIHC, 47.5% contained carcinoma in a single section level. CONCLUSION: SSSIHC of the entire SLN at 150 µm intervals are required to identify occult metastasis in OSCC.

Local Resting Ca2+ Controls the Scale of Astroglial Ca2+ Signals.

Astroglia regulate neurovascular coupling while engaging in signal exchange with neurons. The underlying cellular machinery is thought to rely on astrocytic Ca2+ signals, but what controls their amplitude and waveform is poorly understood. Here, we employ time-resolved two-photon excitation fluorescence imaging in acute hippocampal slices and in cortex in vivo to find that resting [Ca2+] predicts the scale (amplitude) and the maximum (peak) of astroglial Ca2+ elevations. We bidirectionally manipulate resting [Ca2+] by uncaging intracellular Ca2+ or Ca2+ buffers and use ratiometric imaging of a genetically encoded Ca2+ indicator to establish that alterations in resting [Ca2+] change co-directionally the peak level and anti-directionally the amplitude of local Ca2+ transients. This relationship holds for spontaneous and for induced (for instance by locomotion) Ca2+ signals. Our findings uncover a basic generic rule of Ca2+ signal formation in astrocytes, thus also associating the resting Ca2+ level with the physiological "excitability" state of astroglia.