Building a vertically integrated genomic learning health system: The biobank at the Colorado Center for Personalized Medicine.

Precision medicine initiatives across the globe have led to a revolution of repositories linking large-scale genomic data with electronic health records, enabling genomic analyses across the entire phenome. Many of these initiatives focus solely on research insights, leading to limited direct benefit to patients. We describe the biobank at the Colorado Center for Personalized Medicine (CCPM Biobank) that was jointly developed by the University of Colorado Anschutz Medical Campus and UCHealth to serve as a unique, dual-purpose research and clinical resource accelerating personalized medicine. This living resource currently has more than 200,000 participants with ongoing recruitment. We highlight the clinical, laboratory, regulatory, and HIPAA-compliant informatics infrastructure along with our stakeholder engagement, consent, recontact, and participant engagement strategies. We characterize aspects of genetic and geographic diversity unique to the Rocky Mountain region, the primary catchment area for CCPM Biobank participants. We leverage linked health and demographic information of the CCPM Biobank participant population to demonstrate the utility of the CCPM Biobank to replicate complex trait associations in the first 33,674 genotyped individuals across multiple disease domains. Finally, we describe our current efforts toward return of clinical genetic test results, including high-impact pathogenic variants and pharmacogenetic information, and our broader goals as the CCPM Biobank continues to grow. Bringing clinical and research interests together fosters unique clinical and translational questions that can be addressed from the large EHR-linked CCPM Biobank resource within a HIPAA- and CLIA-certified environment.

Factors influencing customers' dine out intention during COVID-19 reopening period: The moderating role of country-of-origin effect.

COVID-19 pandemic negatively affected the restaurant industry and reopening provides restaurants an opportunity to survive this crisis. This study examined the interplay of perceived importance of preventive measures, dining involvement, brand trust, and customers' intention to dine out at American Chinese restaurants during the reopening period. Additionally, the study investigated the moderating role of country-of-origin (COO) effect on these relationships. 296 U.S. restaurant customers recruited via a market research company completed the online survey. Structural equation modeling was used for data analyses. The results indicated that dining involvement had a direct positive effect on customers' intention to dine out. Moreover, both perceived importance of preventive measures and dining involvement could enhance customers' intention to dine out indirectly via brand trust. Positive COO effect moderated the relationship between perceived importance of preventive measures and brand trust. The study provided significant implications for restaurant operators in the U.S during the reopening period.

National survey of physicians' perspectives on pharmacogenetic testing in solid organ transplantation.

INTRODUCTION: Our objective was to evaluate physicians' perspectives on the clinical utility of pharmacogenetic (PGx) testing in kidney, liver, heart, and lung transplantation (KLHL-Tx). METHODS: A 36-question web-based survey was developed and administered to medical and surgical directors of US KLHL-Tx centers. RESULTS: There were 82 respondents (10% response rate). The majority were men (78%), non-Hispanic whites (70%), medical directors (72%), and kidney transplant physicians (35%). Although 78% of respondents reported having some PGx education, most reported lack of confidence in their PGx knowledge and ability to apply a PGx test. Participants reported mixed views about the clinical utility of PGx testing-most agreed with the efficacy of PGx testing, but not the benefits relative to the risks or standard of care. While 55% reported that testing was available at their institution, only 38% ordered a PGx test in the past year, most commonly thiopurine-S-methyltransferase. Physician-reported barriers to PGx implementation included uncertainty about the clinical value of PGx testing and patient financial burden. CONCLUSION: Together, our findings suggest prospective PGx research and pilot implementation programs are needed to elucidate the clinical utility and value of PGx in KLHL-Tx. These initiatives should include educational efforts to inform the use of PGx testing.

Patients' Perspectives on Psychiatric Pharmacogenetic Testing.

INTRODUCTION: There is growing interest to adopt pharmacogenetic (PGx) testing in psychiatric medicine, despite mixed views regarding its clinical utility. Nevertheless, providers are utilizing PGx testing among patients with mental health disorders. This study sought to assess genotyped patients' perspectives and experiences with psychiatric PGx testing. METHODS: Individual semi-structured interviews were conducted among patients with depression who had undergone psychiatric PGx testing. The audio-recorded interviews were transcribed and analyzed inductively and deductively for salient themes. RESULTS: Twenty patients (100% Caucasian, 60% female, mean age 39±18 years) were interviewed. The majority of the PGx tests were provider-initiated for patients who failed multiple pharmacotherapies (50%) and/or had medication intolerances (45%). Patients' pre-testing expectations ranged from hopefulness to indifference to skepticism. Their post-testing experiences varied from optimism to disappointment, with the perceived value of the test influenced by the results and cost of the test. DISCUSSION: Genotyped patients had mixed perspectives, expectations, and experiences with psychiatric PGx testing. Their perceived value of the test was influenced by the test outcomes and its cost.

Analysis of comprehensive pharmacogenomic profiling to impact in-hospital prescribing.

INTRODUCTION: In-hospital adverse medication events result in increased morbidity and mortality. Many implicated drugs carry pharmacogenomic information. We hypothesized that comprehensive pre-emptive pharmacogenomic profiling could have high relevance for in-hospital prescribing. PATIENTS AND METHODS: We retrospectively analyzed the in-hospital medications of a genotyped outpatient cohort admitted at our institution from 2012 to 2015. The endpoints were medication changes (new medications initiated, dose adjustments, or medications discontinued) involving drugs with pharmacogenomic annotations from three sources: Clinical Pharmacogenetics Implementation Consortium guidance, Food and Drug Administration label information, and drugs with clinical decision supports in our institutional pharmacogenomic Genomic Prescribing System. RESULTS: Of 867 genotyped outpatients, 20 were hospitalized (mean: 78.2 years, 65% male). This hospitalized cohort was significantly older (78.2 vs. 61.3 years, P<0.0001) and took more medications (8.9 vs. 5.0 medications, P<0.0001). Out of 159 medication changes made, most (67.9%) were new medications (average: 2.5/hospitalization) with one-third of these having clinically annotated pharmacogenomic information. Half of all hospitalizations involved at least one pharmacogenomic medication. Over half (55%) of the hospitalized cohort was newly prescribed at least one of eight key pharmacogenomic medications, including high-risk drugs such as clopidogrel, codeine, and warfarin. CONCLUSION: Our study suggested that older patients and those with polypharmacy were at increased risk for hospitalizations, where many new prescriptions included frequently used pharmacogenomic drugs. Targeting this group for pre-emptive genotyping would facilitate the delivery of highly relevant information to inform inpatient prescribing.

Circulating MicroRNA-125b Predicts the Presence and Progression of Uremic Vascular Calcification.

OBJECTIVE: Vascular calcification (VC) is a major cause of mortality in patients with end-stage renal diseases. Biomarkers to predict the progression of VC early are in urgent demand. APPROACH AND RESULTS: We identified circulating, cell-free microRNAs as potential biomarkers using in vitro VC models in which both rat and human aortic vascular smooth muscle cells were treated with high levels of phosphate to mimic uremic hyperphosphatemia. Using an Affymetrix microRNA array, we found that miR-125b and miR-382 expression levels declined significantly as biomineralization progressed, but this decline was only observed for miR-125b in the culture medium. A time-dependent decrease in aortic tissue and serum miR-125b levels was also found in both ex vivo and in vivo renal failure models. We examined the levels of circulating, cell-free miR-125b in sera from patients with end-stage renal diseases (n=88) and found an inverse association between the severity of VC and the circulating miR-125b level, irrespective of age or mineral-related hormones (odds ratio, 0.71; P=0.03). Furthermore, serum miR-125b levels on enrollment can predict VC progression years later (for high versus low, odds ratio, 0.14; P<0.01; for the highest versus lowest tertile and middle versus lowest tertile, odds ratio, 0.55 and 0.13; P=0.3 and <0.01, respectively). The uremic VC prediction efficacy using circulating miR-125b levels was also observed in an independent cohort (n=135). CONCLUSIONS: The results suggest that serum miR-125b levels are associated with VC severity and serve as a novel predictive marker for the risk of uremia-associated calcification progression.

Assessment of patient perceptions of genomic testing to inform pharmacogenomic implementation.

OBJECTIVE: Pharmacogenomics seeks to improve prescribing by reducing drug inefficacy/toxicity. However, views of patients during pharmacogenomic-guided care are largely unknown. We sought to understand the attitudes and perceptions of patients in an institutional implementation project and hypothesized that views would differ on the basis of experience with pharmacogenomic-guided care. METHODS: Two focus groups were conducted - one group included patients who had previously been subjected to broad pharmacogenomic genotyping with results available to physicians (pharmacogenomic group), whereas the other had not been offered genotyping (traditional care). Five domains were explored: (i) experiences with medications/side effects, (ii) understanding of pharmacogenomics, (iii) impact of pharmacogenomics on relationships with healthcare professionals, (iv) scenarios involving pharmacogenomic-guided prescribing, and (v) responses to pharmacogenomic education materials. RESULTS: Nine pharmacogenomic and 13 traditional care participants were included. Participants in both groups agreed that pharmacogenomics could inform prescribing and help identify problem prescriptions, but expressed concerns over insurance coverage and employment discrimination. Both groups diverged on who should be permitted to access pharmacogenomic results, with some preferring access only for providers with a longstanding relationship, whereas others argued for open access. Notably, traditional care participants showed greater skepticism about how results might be used. Case scenarios and tested educational materials elicited strong desires on the part of patients for physicians to engage participants when considering pharmacogenomic-based prescribing and to utilize shared decision-making. CONCLUSION: Participants experiencing pharmacogenomic-guided care were more receptive toward pharmacogenomic information being used than traditional care participants. As key stakeholders in implementation, addressing patients' concerns will be important to successfully facilitate clinical dissemination.

Impact of Pharmacogenomics on Pediatric Psychotropic Medication Prescribing in an Ambulatory Care Setting.

Objective: Evidence for pharmacogenomic (PGx) guided treatment in child and adolescent psychiatry is growing. This study evaluated the impact of PGx testing on psychotropic medication prescribing in an ambulatory child and adolescent psychiatry and a developmental pediatrics clinic. Methods: This was a single-center, retrospective, descriptive analysis of patients who underwent PGx testing between January 2015 and October 2022 at a child and adolescent psychiatry clinic or developmental pediatrics clinic. The primary outcome was the proportion of patients with at least one psychotropic medication modification made 6-month posttesting that could be attributed to CYP2C19, CYP2D6, HLA-B*15:02, or HLA-A*31:01. Secondary outcomes included reason for testing, types of therapeutic modifications made, and whether the therapeutic modifications concorded with PGx guidelines. Results: A total of 193 patients were analyzed. The average age was 10 ± 4 years old, 60% were male, 78% were Caucasian. Sixty-eight percent had a primary diagnosis of a neurodevelopmental disorder, namely autism spectrum disorder (51%), and attention-deficit/hyperactivity disorder (14%). The reasons for PGx testing included medication inefficacy (34%), medication intolerance (20%), and family request (19%). At the time of PGx testing, 37% of patients were taking ≥1 psychotropic medication with PGx annotation. Overall, 35 PGx-related therapeutic modifications were made in 32 (17%) patients. These included continuing current PGx medication (6.2%) and starting PGx medication (5.2%). These modifications mainly involved antidepressants. Out of these 35 PGx-related therapeutic modifications, 94% were concordant with PGx guidelines. Among 29 patients who were prescribed at least one CYP2D6 inhibitor, 25 (86%) underwent CYP2D6 phenoconversion. Conclusions: It is critical to apply pediatric age-specific considerations when utilizing PGx testing in child and adolescent psychiatry. PGx testing stewardship could provide a framework to guide the clinical utility of PGx in a pediatric population with mental health conditions, including neurodevelopmental disorders.

Implementation of clopidogrel pharmacogenetic clinical decision support for a preemptive return of results program.

PURPOSE: To describe our experiences implementing and iterating CYP2C19 genotype-guided clopidogrel pharmacogenetic clinical decision support (CDS) tools over time in the setting of a large health system-wide, preemptive pharmacogenomics program. SUMMARY: Clopidogrel-treated patients who are genetically predicted cytochrome P450 isozyme 2C19 (CYP2C19) intermediate or poor metabolizers have an increased risk of atherothrombotic events, some of which can be life-threatening. The Clinical Pharmacogenetics Implementation Consortium provides guidance for the use of clopidogrel based on CYP2C19 genotype in patients with cardiovascular and cerebrovascular diseases. Our multidisciplinary team implemented an automated, interruptive alert that fires when clopidogrel is ordered or refilled for biobank participants with structured CYP2C19 intermediate or poor metabolizer genomic indicators in the electronic health record. The implementation began with a narrow cardiovascular indication and setting and was then scaled in 4 primary dimensions: (1) clinical indication; (2) availability across health-system locations; (3) care venue (e.g., inpatient vs outpatient); and (4) provider groups (eg, cardiology and neurology). We iterated our approach over time based on evolving clinical evidence and proactive strategies to optimize CDS maintenance and sustainability. A key facilitator of expansion was socialization of the broader pharmacogenomics initiative among our academic medical center community, accompanied by clinician acceptance of pharmacogenetic alerts in practice. CONCLUSION: A multidisciplinary collaboration is recommended to facilitate the use of CYP2C19 genotype-guided antiplatelet therapy in patients with cardiovascular and cerebrovascular diseases. Evolving clopidogrel pharmacogenetic evidence necessitates thoughtful iteration of implementation efforts and strategies to optimize long-term maintenance and sustainability.

Food safety training needs at evacuation shelters operated by faith-based organizations.

The authors conducted a survey to identify food safety training needs at evacuation shelters operated by faith-based organizations (FBOs) in four hurricane-prone states. Five thousand randomly selected FBO leaders were asked questions about their food safety attitudes and food handling practices at evacuation shelters. Descriptive statistics and multivariate analysis of variance were calculated to summarize and prioritize the responses. Results from 138 leaders revealed that on average, 590 +/- 4,787 evacuees were served for 36 +/- 72 days at FBO-operated shelters. Only 19.6% felt they were well prepared for the shelter. Only 5.8% had professional food preparation staff and many accepted hot (47.8%) and cold (37%) prepared food donations. Some lacked adequate refrigerator (18.8%) or freezer (16.7%) spaces, but 40% kept hot food leftovers for later use. The majority did not provide food safety training before opening the shelters (73.2%), yet 76.9% said they will provide food to evacuation shelters again. The results show a need for food safety training and specific strategies for training at FBOs.

Primary care providers' preferences for the communication and management of actionable genomic findings from a research biobank.

Purpose: Little is known about non-genetics health care specialists' attitudes toward the return and utilization of actionable genomic results from a research biobank. We surveyed primary care providers (PCPs) to explore their perspectives on these results and their preferences for return. Methods: We administered a paper and web-based 27-question survey to PCPs residing locally and caring for adult patients. Recruitment was conducted in person and by email, focusing on PCPs likely to interact with results generated by our institution's biobank. Results: Of the ~482 PCPs contacted, 77 (16%) returned surveys. Although most respondents (90%) prefer that a genetics specialist be involved in communicating biobank-generated genomic results to patients, about 40% of respondents reported that a PCP shares the responsibility to discuss these results along with other specialists. A majority of respondents (74%) felt uncomfortable communicating these results to patients. However, respondents reported significantly greater comfort with this process when offered targeted educational resources (62% with vs 10% without resources; P < 10-5). Conclusion: PCPs recognize the need to engage with their patients' biobank-generated genomic results but feel uncomfortable in doing so. Relevant resources are needed to improve PCPs' confidence in the use of these types of results to affect patient care.

The Effects of Social Distance and Front-of-Package Claims on Healthy Food Selection: Moderating Role of Perceived Importance of Eating Healthily.

Applying construal level theory, this study examined how social distance (thinking of self/children), front-of-package (FOP) claim type (nutrient/health/control), and perceived importance of eating healthily (low/high) impact consumer responses (attitudes/purchase intent) to healthier food products through an online experiment with 171 U.S. parents from low-to-mid socio-economic households. Participants were randomly assigned to view controlled images of healthier foods with packaging that bore different claim types for real and fictitious brands. Results revealed that when choosing for themselves, consumer attitudes were more positive when the healthier food package carried a nutrient (vs. health) claim, however, control claims received the most positive evaluations. When choosing for children, attitudes were more positive when the package carried a health (vs. nutrient/control) claim. Attitudes toward healthier foods were higher for consumers with high (vs. low) perceived importance of eating healthily when the package bore a nutrient claim, however, their attitudes did not significantly differ when the package bore a health/control claim. Purchase intent for healthier foods was higher for consumers with high (vs. low) perceived importance of healthy eating when shopping for self; whereas, when shopping for children, purchase intent did not significantly differ between consumers who varied in perceived importance of eating healthily.

Advancing Pharmacogenomics-Based Care Through Interprofessional Education.

As genomic medicine becomes increasingly complex, pharmacists need to work collaboratively with other healthcare professionals to provide genomics-based care. The core pharmacist competencies in genomics were recently updated and mapped to the entrustable professional activities (EPAs). The new competency that is mapped to the "Interprofessional Team Member" EPA domain emphasizes the role of pharmacists as the pharmacogenomics experts in an interprofessional healthcare team. Interprofessional education (IPE) activities involving student pharmacists and students from other healthcare disciplines are crucial to prepare student pharmacists for a team-based approach to patient-centered care. This commentary discusses the pharmacogenomics-focused IPE activities implemented by 3 programs, the challenges faced, and the lessons learned. It also discusses strategies to develop pharmacogenomics-focused IPE activities based on existing resources. Developing pharmacogenomics-focused IPE activities will help prepare pharmacy graduates with the knowledge, skills, and attitudes to lead collaborative, interprofessional teams in the provision of pharmacogenomics-based care, consistent with the standards described in the genomics competencies for pharmacists.

Successful Management of Fetal Torsades de Pointes and Long QT Syndrome by a Cardio-Obstetrical Team.

A 32-week fetus with tachycardia and bradycardia, diagnosed with torsades de pointes, atrioventricular block, and sinus bradycardia due to a de novo KCNH2 mutation was successfully managed by a cardio-obstetrical team. Maternal/fetal pharmacogenomic testing resulted in appropriate drug dosing without toxicity and delivery of a term infant in sinus rhythm.

MicroRNA regulation via DNA methylation during the morula to blastocyst transition in mice.

Epigenetic regulation is responsible for transcriptional silencing of genes and parental imprinting. This study addresses the question whether microRNAs (miRNAs) could be affected by DNA methylation during morula-blastocyst transition. Mouse embryos were treated with/without a DNA methyltransferase inhibitor (5-aza-2'-deoxycytidine, 5-aza-dC, 10 nM-5 µM). Changes of miRNAs were analyzed by quantitative real-time (Q-PCR)-based megaplex pre-amp microRNA assays. Development from morula to blastocyst in mice was inhibited by 5-aza-dC in a dose-dependent manner (10 nM-5 µM), with half of the embryos arrested at morula stage when treated with levels of 5-aza-dC as low as 50 nM. In total, 48 down-regulated microRNAs and 17 up-regulated microRNAs (≥5-fold changes) were identified after 5-aza-dC treatment, including let-7e, mir-20a, mir-21, mir-34b, mir-128b and mir-452. Their predicted targets were selected based on software analysis, published databases and further confirmed by Q-PCR. At least eight targets, including dnmt3a, jagged 1, sp1, edg2, abcg4, numa1, tmsb10 and csf1r were confirmed. In conclusion, 5-aza-dC-modified microRNA profiles and identification of the microRNA's targets during the morula to blastocyst stage in mice provide information that helps us to explore the relationship between fertility, microRNA regulation and epigenetic intervention.

Patients' perspectives of a pharmacist-provided clinical pharmacogenomics service.

Aim: To assess the perspectives and experiences of patients who participated in a pharmacist-provided clinical pharmacogenomics (PGx) service. Methods: We conducted individual semistructured interviews with 16 patients who received a pharmacist-provided PGx service. Qualitative data were analyzed to identify pertinent themes. Results: The major themes identified were: heterogeneity of patient PGx experiences and preferences, pharmacists as appropriate providers of PGx services, considerations regarding the use of PGx results in routine healthcare and perceived applications of PGx testing. Theme-derived considerations included the need to establish appropriate pre-genotyping expectations, individualize patient education, facilitate collaboration with patients' providers and sustainably update patients' PGx information over time. Conclusion: Patient-specific perspectives such as these are important to consider when providing clinical PGx services, with intention of optimizing patient experiences.

Pharmacists Leading the Way to Precision Medicine: Updates to the Core Pharmacist Competencies in Genomics.

Genomics is becoming an increasingly important part of health care, and pharmacists are well-positioned to be practice-based leaders in pharmacogenomics and precision medicine. Competencies available through the Genetics/Genomics Competency Center provide a framework for pharmacogenomics instruction in both pharmacy school curricula and continuing education programs. Given the significant advancements in pharmacogenomics over the past decade, the 2019-2020 American Association of Colleges of Pharmacy Pharmacogenomics Special Interest Group updated the pharmacist competencies. The process used a systematic approach which included mapping pharmacogenomics-specific competencies to the entrustable professional activities for pharmacists and seeking consensus from key stakeholders. The result is an expansion to 30 competencies that reflect the contemporary roles pharmacists play in the application of pharmacogenomics in clinical practice. When implemented into curricula, these competencies will ensure that learners are "practice ready" to integrate pharmacogenomics into patient care. Additional postgraduate training is needed for advanced roles in pharmacogenomics implementation, education, and research.

Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2C19 Genotype and Clopidogrel Therapy: 2022 Update.

CYP2C19 catalyzes the bioactivation of the antiplatelet prodrug clopidogrel, and CYP2C19 genotype impacts clopidogrel active metabolite formation. CYP2C19 intermediate and poor metabolizers who receive clopidogrel experience reduced platelet inhibition and increased risk for major adverse cardiovascular and cerebrovascular events. This guideline is an update to the 2013 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for the use of clopidogrel based on CYP2C19 genotype and includes expanded indications for CYP2C19 genotype-guided antiplatelet therapy, increased strength of recommendation for CYP2C19 intermediate metabolizers, updated CYP2C19 genotype to phenotype translation, and evidence from an expanded literature review (updates at www.cpicpgx.org).

NOVEL-1st: an observational study to assess the safety and efficacy of nilotinib in newly diagnosed patients with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase in Taiwan.

Nilotinib has been approved for the treatment of Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase (Ph+ CML-CP). However, the real-world evidence of nilotinib in newly diagnosed untreated Ph+ CML-CP is limited in Taiwan. The NOVEL-1st study was a non-interventional, multi-center study collecting long-term safety and effectiveness data in patients with newly diagnosed and untreated Ph+ CML-CP receiving nilotinib. We enrolled 129 patients from 11 hospitals. Overall, 1,466 adverse events (AEs) were reported; among these, 151 were serious and 524 were nilotinib-related. Common hematological AEs were thrombocytopenia (31.0%), anemia (20.9%), and leukopenia (14.0%); common nilotinib-related AEs were thrombocytopenia (29.5%), anemia (14.7%), and leukopenia (12.4%). Early molecular response, defined as BCR-ABL ≤ 10% at Month 3, was seen in 87.6% of patients. By 36 months, the cumulative rates of complete hematologic response, complete cytogenetic response, major molecular response, molecular response 4.0-log reduction, and molecular response 4.5-log reduction were 98.5, 92.5, 85.8, 65.0, and 45.0%, respectively. Nilotinib is effective and well-tolerated in patients with newly diagnosed Ph+ CML-CP in the real-world setting. Long-term holistic care and a highly tolerable AE profile may contribute to good treatment outcomes in Ph+ CML-CP under first-line treatment with nilotinib.

miRNA-34b as a tumor suppressor in estrogen-dependent growth of breast cancer cells.

INTRODUCTION: Estrogen is involved in several physiological and pathological processes through estrogen receptor (ER)-mediated transcriptional gene regulation. miRNAs (miRs), which are noncoding RNA genes, may respond to estrogen and serve as posttranscriptional regulators in tumorigenic progression, especially in breast cancer; however, only limited information about this possibility is available. In the present study, we identified the estrogen-regulated miR-34b and investigated its functional role in breast cancer progression. METHODS: Estrogen-regulated miRNAs were identified by using a TaqMan low density array. Our in vivo Tet-On system orthotopic model revealed the tumor-suppressive ability of miR-34b. Luciferase reporter assays and chromatin immunoprecipitation assay demonstrated miR-34b were regulated by p53-ER interaction. RESULTS: In this study, we identified one such estrogen downregulated miRNA, miR-34b, as an oncosuppressor that targets cyclin D1 and Jagged-1 (JAG1) in an ER+/wild-type p53 breast cancer cell line (MCF-7), as well as in ovarian and endometrial cells, but not in ER-negative or mutant p53 breast cancer cell lines (T47D, MBA-MB-361 and MDA-MB-435). There is a negative association between ERα and miR-34b expression levels in ER+ breast cancer patients. Tet-On induction of miR-34b can cause inhibition of tumor growth and cell proliferation. Also, the overexpression of miR-34b inhibited ER+ breast tumor growth in an orthotopic mammary fat pad xenograft mouse model. Further validation indicated that estrogen's inhibition of miR-34b expression was mediated by interactions between ERα and p53, not by DNA methylation regulation. The xenoestrogens diethylstilbestrol and zeranol also showed similar estrogenic effects by inhibiting miR-34b expression and by restoring the protein levels of the miR-34b targets cyclin D1 and JAG1 in MCF-7 cells. CONCLUSIONS: These findings reveal that miR-34b is an oncosuppressor miRNA requiring both ER+ and wild-type p53 phenotypes in breast cancer cells. These results improve our ability to develop new therapeutic strategies to target the complex estrogenic pathway in human breast cancer progression through miRNA regulation.