The Economic Value of Antimicrobial Use in Livestock Production.

(1) Introduction: Antimicrobial agents have played an important role in improving the productivity of worldwide livestock production by reducing the impact of livestock diseases. However, a major drawback of antimicrobial use is the emergence of antimicrobial-resistant pathogens in food-producing animals. To reduce the use of antimicrobials, it is important to know the economic value of the use of antimicrobials and factors that determine that economic value. (2) Results: A theoretical framework was developed to assess the economic value of antimicrobial use. Three situations were distinguished: firstly, a baseline model for a farm with a conventional production system; secondly, an extension of the baseline model that includes the impact of production system improvements; and thirdly, an extension of the baseline model that includes the impacts of risk and risk attitude. This framework shows that the economic value of antimicrobial use is negatively affected by the price of productive inputs and damage-abatement inputs, and positively affected by the output price, the input-output combination, the damage abatement effect, risk aversion and variance in profit. (3) Conclusions: The theoretical framework presented in this study shows that there are several factors that (can) affect the economic value of antimicrobial use. The knowledge about the effect of these factors can be utilized to affect the economic value of antimicrobials and, consequently, affect antimicrobial use.

Declining Resident Surgical Autonomy and Improving Surgical Outcomes: Correlation Does Not Equal Causality.

OBJECTIVE: The volume of cases that residents perform independently have decreased leaving graduating chief residents less prepared for independent practice. Outcomes are not worse when residents are given autonomy with appropriate supervision, however it is unknown if outcomes are worsening with decreasing operative autonomy experience. We hypothesize that resident autonomous cases parallel the improving outcomes in surgical care over time, however, are less complex and on lower acuity patients. DESIGN: Retrospective study utilizing the Veterans Affairs Surgical Quality Improvement Program (VASQIP) database. SETTING: Operative cases performed on teaching services within the VASQIP database from July 1, 2004 to September 30, 2019, were included. PARTICIPANTS: All adult patients who underwent a surgical procedure from July 1, 2004, to September 30, 2019, at a VA hospital on a service that included residents were initially included. After inclusions and exclusions, there were 1,346,461 cases. Cases were divided into 3 sequential 5 year eras (ERA 1: 2004-2008 n = 415,614, ERA 2: 2009-2013 n = 478,528, and ERA 3: 2014-2019 n = 452,319). The main exposure of interest was level of resident supervision, coded at the time of procedure as: attending primary surgeon (AP); attending and resident (AR), or resident primary with the attending supervising but not scrubbed (RP). We compared 30 day all-cause mortality, composite morbidity, work relative value unit (wRVU), hospital length of stay, and operative time between each ERA for RP cases, as well as within each ERA for RP cases compared to AR and AP cases. RESULTS: There was a progressive decline in the rate of RP cases in each successive ERA (ERA 1: 58,249 (14.0%) vs ERA 2: 47,891 (10.0%) vs ERA 3: 35,352 (7.8%), p < 0.001). For RP cases, patients were progressively getting older (60 yrs [53-71] vs 63 yrs [54-69] vs 66 yrs [57-72], p < 0.001) and sicker (ASA 3 58.7% vs 62.5% vs 66.2% and ASA 4/5 8.4% vs 9.6% vs10.0%, p < 0.001). Odds of mortality decreased in each ERA compared to the previous (aOR 0.71 [0.62-0.80] ERA 2 vs ERA 1 and 0.82 [0.70-0.97] ERA 3 vs ERA 2) as did morbidity (0.77 [0.73-0.82] ERA 2 vs ERA 1 and 0.72 [0.68-0.77] ERA 3 vs ERA 2). Operative and length of stay also decreased while wRVU stayed unchanged. When comparing RP cases to AP and AR within each ERA, RP cases tended to be on younger and healthier patients with a lower wRVU, particularly compared to AR cases. Mortality and morbidity were no different or better in RP compared to AR and AP. CONCLUSIONS: Despite resident autonomy decreasing, outcomes in cases where they are afforded autonomy are improving over time. This despite RP cases being on sicker and older patients and performing roughly the same complexity of cases. They also continue to perform no worse than cases with higher levels of supervision. Efforts to increase surgical resident operative autonomy are still needed to improve readiness for independent practice.

Targeting the mTOR Pathway for the Prevention of ER-Negative Breast Cancer.

PREVENTION RELEVANCE: Our results show that everolimus delays mammary tumor formation in multiple mouse models, suggesting that mTOR inhibitors will be useful for the prevention of ER-negative and triple-negative breast cancer in humans. See related Spotlight, p. 787.

Navigating Pandemic Moral Distress at Home and at Work: Frontline Workers' Experiences.

Background: During the COVID-19 pandemic, frontline workers faced a series of challenges balancing family and work responsibilities. These challenges included making decisions about how to reduce COVID-19 exposure to their families while still carrying out their employment duties and caring for their children. We sought to understand how frontline workers made these decisions and how these decisions impacted their experiences.Methods: Between October 2020 and May 2021, we conducted 61 semi-structured interviews in English or Spanish, with individuals who continued to work outside of the home during the pandemic and had children living at home. Interviews were recorded, transcribed verbatim, and analyzed using abductive methods.Results: Frontline workers experienced moral distress, the inability to act in accordance with their values and obligations because of internal or external constraints. Their moral distress was a result of the tensions they felt as workers and parents, which sometimes led them to feel like they had to compromise on either or both responsibilities. Individuals felt morally conflicted because 1) their COVID-19 work exposures presented risk that often jeopardized their family's health; 2) their work hours often conflicted with their increased childcare responsibilities; and 3) they felt a duty to their colleagues, patients/customers, and communities to continue to show-up to work.Conclusions: Our findings point to a need to expand the concept of moral distress to include the perspectives of frontline workers outside of the healthcare professions and the fraught decisions that workers make outside of work that may impact their moral distress. Expanding the concept of moral distress also allows for a justice-based framing that can focus attention on the disparities inherent in much frontline work and can justify programmatic recommendations, like increasing paid childcare opportunities, to alleviate moral distress.

COVID-19 and HIV/AIDS in a cohort study in Sao Paulo, Brazil: outcomes and disparities by race and schooling.

Studies describing characteristics and outcomes of COVID-19 among people living with HIV are currently limited, lacking detailed evaluation of the interplay among demographics, HIV-related variables, and comorbidities on COVID-19 outcomes. This retrospective cohort study describes mortality rates overall and according to demographic characteristics and explores predictors of admission to intensive care unit and death among 255 persons living with HIV with severe acute respiratory syndrome and confirmed SARS-CoV-2 infection in the State of Sao Paulo, Brazil. We found that the overall mortality rate was 4.1/1,000 person-days, with a case-fatality of 34%. Higher rates occurred among older adults, Black/Mixed skin color/race patients, and those with lower schooling. In a multivariable analysis adjusted for age, sex, CD4 count, viral load and number of comorbidities, skin color/race, and schooling remained significantly associated with higher mortality. Although tenofovir use was more frequent among survivors in the univariable analysis, we failed to find a statistically significant association between tenofovir use and survival in the multivariable analysis. Our findings suggest that social vulnerabilities related to both HIV and COVID-19 significantly impact the risk of death, overtaking traditional risk factors such as age, sex, CD4 count, and comorbidities.

Association Between Operative Autonomy of Surgical Residents and Patient Outcomes.

IMPORTANCE: Resident operative autonomy has been steadily decreasing. Whether this reduction in autonomy has been associated with changes in patient outcomes is unclear. OBJECTIVE: To assess whether surgical procedures performed by residents without an attending surgeon scrubbed are associated with differences in patient outcomes compared with procedures performed by attending surgeons alone or by residents with the assistance of attending surgeons. DESIGN, SETTING, AND PARTICIPANTS: This retrospective propensity score-matched cohort study analyzed 30-day outcomes among patients who received operations at US Veterans Affairs (VA) medical centers and were recorded within the VA Surgical Quality Improvement Program (VASQIP) database from July 1, 2004, to September 30, 2019. Among 1 797 056 operations recorded in the VASQIP during that period, 1 319 020 were eligible for inclusion. Operations performed by a surgical resident without an attending surgeon scrubbed (resident primary) were propensity score matched on a 1:1 ratio (based on year of procedure and patient age, race, sex, American Society of Anesthesiologists physical status classification, functional status, emergency status, inpatient status, presence of multiple comorbidities, and Current Procedural Terminology code) to operations performed by an attending surgeon only (surgeon primary) and operations performed by a resident with assistance from an attending surgeon (resident plus surgeon). EXPOSURES: Level of resident involvement. MAIN OUTCOMES AND MEASURES: Thirty-day adjusted all-cause mortality. RESULTS: Among 1 319 020 surgical procedures included, 138 750 were performed by residents only, 308 724 were performed by surgeons only, and 871 546 were performed by residents and surgeons. For the 1 319 020 total cases, patients' mean (SD) age was 61.6 (12.9) years; 1 223 051 patients (92.7%) were male; and 212 315 (16.1%) were Black or African American, 63 817 (4.9%) were Hispanic, 830 704 (63.0%) were White, and 212 814 (16.1%) were of other or unknown race and ethnicity. Propensity score matching produced 101 130 pairs of resident-primary and surgeon-primary procedures and 137 749 pairs of resident-primary and resident plus surgeon procedures. Patient all-cause mortality and morbidity were no different among those who received surgeon-primary procedures (mortality: odds ratio [OR], 1.03 [95% CI, 0.95-1.12]; morbidity: OR, 1.01 [95% CI, 0.97-1.05]) vs resident plus surgeon procedures (mortality: OR, 1.03 [95% CI, 0.97-1.11]; all-cause morbidity: OR, 0.97 [95% CI, 0.95-1.00]). Resident-primary procedures had longer operative times than surgeon-primary procedures (median, 80 minutes [IQR, 50-123 minutes] vs 70 minutes [IQR, 41-114 minutes], respectively; P < .001) but shorter operative times than resident plus surgeon procedures (median, 71 minutes [IQR, 43-113 minutes] vs 73 minutes [IQR, 45-115 minutes]; P < .001). Hospital length of stay was unchanged among resident-primary vs surgeon-primary procedures (median, 4 days [IQR, 2-10 days] vs 4 days [IQR, 2-9 days]; P = .08) and statistically significantly shorter than resident plus surgeon procedures (median, 4 days [IQR, 1-9 days] vs 4 days [IQR, 2-10 days]; P < .001). CONCLUSIONS AND RELEVANCE: In this cohort study, surgical procedures performed by residents alone were not associated with any changes in all-cause mortality or composite morbidity compared with those performed by attending surgeons alone or by residents with the assistance of attending surgeons. Given these findings and the importance of operative autonomy to prepare surgical residents for independent practice, efforts to increase autonomy are both safe and needed.

Insight Into Host-Microbe Interactions Using Microbial Flow Cytometry Coupled to Next-Generation Sequencing.

Antibody-based assays have been a cornerstone of infectious disease diagnostics for over 100 years [1]. These assays rely on the exquisite sensitivity and specificity of humoral response to almost all infections. While next-generation sequencing (NGS) has tremendous potential to improve diagnostics and uncover host-microbial relationships by directly identifying nucleic acids from infectious microbes, challenges and opportunities for new approaches remain. Here, we review a group of cutting-edge techniques that couple antibody responses with flow cytometry of antibody tagged microbes and NGS. These studies are bringing into focus the dynamic relationship between our immune systems and endogenous microbial communities, which are an important source of pathogens. For simplicity, we use the umbrella term mFLOW-Seq (microbial flow cytometry coupled to NGS) to describe these approaches.

General Surgical Resident Operative Autonomy vs Patient Outcomes: Are we Compromising Training without Net Benefit to Hospitals or Patients?

OBJECTIVE: Resident operative autonomy has been steadily declining. The reasons are multifactorial and include concerns related to patient safety and operating room efficiency. Simultaneously, faculty have expressed that residents are less prepared for independent practice. We sought to understand the effect of decreasing resident autonomy on patient outcomes and operative duration. DESIGN: Retrospective study utilizing the Veterans Affairs Surgical Quality Improvement Program (VASQIP) database. SETTING: Operative cases within the VASQIP database from July 1, 2004-September 30, 2019 were analyzed. PARTICIPANTS: All adult patients who underwent a surgical procedure from July 1, 2004 to September 30, 2019 were analyzed. The subpopulation of patients that underwent a surgical procedure in General Surgery or Peripheral Vascular Surgery were identified based on the code of the specialty surgeon. Within these subgroups, the most frequent cases by current procedural terminology (CPT) code were selected for study inclusion. The principle CPT code of all cases was further coded by level of supervision: attending primary surgeon (AP); attending and resident (AR), or resident primary with the attending supervising but not scrubbed (RP). Baseline demographics, operative variables, and outcomes were compared between groups. RESULTS: The VASQIP database included 698,391 total general/vascular surgery cases. 38,483 (6%) of them were RP cases. Analysis revealed that the top 5 RP cases account for 73% of total RP volume-these include: 1) Hernias (55% total; 33% open inguinal, 13% umbilical, 5% open ventral/incisional, and 4% laparoscopic) 2) cholecystectomy (18%), 3) Amputations (17% total; 10% above knee, 7% below knee), 4) Appendectomy (7%) and 5) Open colectomy (3%). The percentage of cases at teaching hospitals that were RP cases significantly decreased from 15% in 2004 to 5% in 2019 (p < 0.001). RP cases were generally sicker as demonstrated by higher ASA classifications and more likely to be emergent cases. Operative times were also increased with resident involvement, but RP cases were faster than AR cases on average. After adjusting for baseline demographics, case type, and year of procedure, mortality was no different between groups. Complications were higher in the AR group but not in the RP group. CONCLUSIONS: The rate of resident autonomy in routine general surgery cases has decreased by two-thirds over the 15-year study period. Cases performed by residents without an attending surgeon scrubbed were performed faster than cases performed by a resident and attending together and there was no increase in patient morbidity or mortality when residents performed cases independently. The erosion of resident autonomy is not justified based upon operative time or patient outcomes. Efforts to increase surgical resident operative autonomy are needed.

PI4KIIIß is a therapeutic target in chromosome 1q-amplified lung adenocarcinoma.

Heightened secretion of protumorigenic effector proteins is a feature of malignant cells. Yet, the molecular underpinnings and therapeutic implications of this feature remain unclear. Here, we identify a chromosome 1q region that is frequently amplified in diverse cancer types and encodes multiple regulators of secretory vesicle biogenesis and trafficking, including the Golgi-dedicated enzyme phosphatidylinositol (PI)-4-kinase IIIß (PI4KIIIß). Molecular, biochemical, and cell biological studies show that PI4KIIIß-derived PI-4-phosphate (PI4P) synthesis enhances secretion and accelerates lung adenocarcinoma progression by activating Golgi phosphoprotein 3 (GOLPH3)-dependent vesicular release from the Golgi. PI4KIIIß-dependent secreted factors maintain 1q-amplified cancer cell survival and influence prometastatic processes in the tumor microenvironment. Disruption of this functional circuitry in 1q-amplified cancer cells with selective PI4KIIIß antagonists induces apoptosis and suppresses tumor growth and metastasis. These results support a model in which chromosome 1q amplifications create a dependency on PI4KIIIß-dependent secretion for cancer cell survival and tumor progression.

Defining personal utility in genomics: A Delphi study.

BACKGROUND: Individual genome sequencing results are valued by patients in ways distinct from clinical utility. Such outcomes have been described as components of "personal utility," a concept that broadly encompasses patient-endorsed benefits, that is operationally defined as non-clinical outcomes. No empirical delineation of these outcomes has been reported. AIM: To address this gap, we administered a Delphi survey to adult participants in a National Institute of Health (NIH) clinical exome study to extract the most highly endorsed outcomes constituting personal utility. MATERIALS AND METHODS: Forty research participants responded to a Delphi survey to rate 35 items identified by a systematic literature review of personal utility. RESULTS: Two rounds of ranking resulted in 24 items that represented 14 distinct elements of personal utility. Elements most highly endorsed by participants were: increased self-knowledge, knowledge of "the condition," altruism, and anticipated coping. DISCUSSION: Our findings represent the first systematic effort to delineate elements of personal utility that may be used to anticipate participant expectation and inform genetic counseling prior to sequencing. The 24 items reported need to be studied further in additional clinical genome sequencing studies to assess generalizability in other populations. Further research will help to understand motivations and to predict the meaning and use of results.

Are physicians prepared for whole genome sequencing? a qualitative analysis.

Although the integration of whole genome sequencing (WGS) into standard medical practice is rapidly becoming feasible, physicians may be unprepared to use it. Primary care physicians (PCPs) and cardiologists enrolled in a randomized clinical trial of WGS received genomics education before completing semi-structured interviews. Themes about preparedness were identified in transcripts through team-based consensus-coding. Data from 11 PCPs and 9 cardiologists suggested that physicians enrolled in the trial primarily to prepare themselves for widespread use of WGS in the future. PCPs were concerned about their general genomic knowledge, while cardiologists were concerned about how to interpret specific types of results and secondary findings. Both cohorts anticipated preparing extensively before disclosing results to patients by using educational resources with which they were already familiar, and both cohorts anticipated making referrals to genetics specialists as needed. A lack of laboratory guidance, time pressures, and a lack of standards contributed to feeling unprepared. Physicians had specialty-specific concerns about their preparedness to use WGS. Findings identify specific policy changes that could help physicians feel more prepared, and highlight how providers of all types will need to become familiar with interpreting WGS results.

Death-associated protein kinase 1 promotes growth of p53-mutant cancers.

Estrogen receptor-negative (ER-negative) breast cancers are extremely aggressive and associated with poor prognosis. In particular, effective treatment strategies are limited for patients diagnosed with triple receptor-negative breast cancer (TNBC), which also carries the worst prognosis of all forms of breast cancer; therefore, extensive studies have focused on the identification of molecularly targeted therapies for this tumor subtype. Here, we sought to identify molecular targets that are capable of suppressing tumorigenesis in TNBCs. Specifically, we found that death-associated protein kinase 1 (DAPK1) is essential for growth of p53-mutant cancers, which account for over 80% of TNBCs. Depletion or inhibition of DAPK1 suppressed growth of p53-mutant but not p53-WT breast cancer cells. Moreover, DAPK1 inhibition limited growth of other p53-mutant cancers, including pancreatic and ovarian cancers. DAPK1 mediated the disruption of the TSC1/TSC2 complex, resulting in activation of the mTOR pathway. Our studies demonstrated that high DAPK1 expression causes increased cancer cell growth and enhanced signaling through the mTOR/S6K pathway; evaluation of multiple breast cancer patient data sets revealed that high DAPK1 expression associates with worse outcomes in individuals with p53-mutant cancers. Together, our data support targeting DAPK1 as a potential therapeutic strategy for p53-mutant cancers.

Living laboratory: whole-genome sequencing as a learning healthcare enterprise.

With the proliferation of affordable large-scale human genomic data come profound and vexing questions about management of such data and their clinical uncertainty. These issues challenge the view that genomic research on human beings can (or should) be fully segregated from clinical genomics, either conceptually or practically. Here, we argue that the sharp distinction between clinical care and research is especially problematic in the context of large-scale genomic sequencing of people with suspected genetic conditions. Core goals of both enterprises (e.g. understanding genotype-phenotype relationships; generating an evidence base for genomic medicine) are more likely to be realized at a population scale if both those ordering and those undergoing sequencing for diagnostic reasons are routinely and longitudinally studied. Rather than relying on expensive and lengthy randomized clinical trials and meta-analyses, we propose leveraging nascent clinical-research hybrid frameworks into a broader, more permanent instantiation of exploratory medical sequencing. Such an investment could enlighten stakeholders about the real-life challenges posed by whole-genome sequencing, such as establishing the clinical actionability of genetic variants, returning 'off-target' results to families, developing effective service delivery models and monitoring long-term outcomes.

The combination of tamoxifen and the rexinoid LG100268 prevents ER-positive and ER-negative mammary tumors in p53-null mammary gland mice.

In pursuit of effective therapeutic agents for the estrogen receptor (ER)-negative breast cancer, we previously showed that bexarotene reduced mammary tumor development by 75% in ErbB2 mice. To further improve the effectiveness of breast cancer prevention, we have now investigated the effects of a combinatorial therapy consisting of two cancer preventive drugs. On the basis of the hypothesis, rexinoid LG100268 plus tamoxifen would more effectively prevent the development of both ER-positive and ER-negative breast cancer. We treated p53-null mammary gland mice with tamoxifen and LG100268, individually and in combination. By 60 weeks of age, vehicle-treated mice developed tumors in 52% of transplanted mammary glands, whereas mice treated with tamoxifen and LG100268 developed tumors in only 13% of transplanted mammary glands. To further define the mechanistic effects of this combinatorial treatment, we investigated the effects of tamoxifen and LG100268 on mammary tissue biomarkers. In mammary tissue harvested before tumor development, the proliferation markers Ki67 and cyclin D1 were significantly reduced in mice treated with the combination therapy. In addition, the rexinoid target genes ABCA1 and ABCG1 were induced in both the rexinoid and combination treatment groups, whereas expression remained constant in tamoxifen group. These results show that tamoxifen-LG100268 combinatorial treatment is more effective in preventing mammary tumors than either agent alone. In addition, these studies have identified relevant tissue biomarkers that can be used to show the effect of these agents on mammary tissue. These results support the development of clinical trials of antiestrogen and rexinoid combinatorial therapy for the prevention of patients with high-risk breast cancer.

CD4+ T cells from HIV-1-infected patients recognize wild-type and mutant human immunodeficiency virus-1 protease epitopes.

Human immunodeficiency virus (HIV)-1 protease is a known target of CD8+ T cell responses, but it is the only HIV-1 protein in which no fully characterized HIV-1 protease CD4 epitopes have been identified to date. We investigated the recognition of HIV-1 protease by CD4+ T cells from 75 HIV-1-infected, protease inhibitor (PI)-treated patients, using the 5,6-carboxyfluorescein diacetate succinimidyl ester-based proliferation assay. In order to identify putative promiscuous CD4+ T cell epitopes, we used the TEPITOPE algorithm to scan the sequence of the HXB2 HIV-1 protease. Protease regions 4-23, 45-64 and 73-95 were identified; 32 sequence variants of the mentioned regions, encoding frequent PI-induced mutations and polymorphisms, were also tested. On average, each peptide bound to five of 15 tested common human leucocyte antigen D-related (HLA-DR) molecules. More than 80% of the patients displayed CD4+ as well as CD8+ T cell recognition of at least one of the protease peptides. All 35 peptides were recognized. The response was not associated with particular HLA-DR or -DQ alleles. Our results thus indicate that protease is a frequent target of CD4+ along with CD8+ proliferative T cell responses by the majority of HIV-1-infected patients under PI therapy. The frequent finding of matching CD4(+) and CD8+ T cell responses to the same peptides may indicate that CD4+ T cells provide cognate T cell help for the maintenance of long-living protease-specific functional CD8+ T cells.

The level and distribution of the GABA(B)R2 receptor subunit in the rat's central auditory system.

The GABA(B) receptor is important for the function of auditory neurons. We used Western blotting and immunohistochemical methods to examine the level and localization of GABA(B)R2, a required subunit of a functional GABA(B) receptor, in the rat's central auditory system. Results revealed that this subunit was expressed throughout the auditory system with the level being high in the layers I-V of the auditory cortex, medial geniculate nucleus, dorsomedial and lateral parts of the inferior colliculus, and the molecular and fusiform cell layers of the dorsal cochlear nucleus. Labeled cell bodies were found in all the areas showing immunoreactivity. Neuropil labeling was strong in areas with high overall levels of immunoreactivity. Regional distributions of the receptor subunit revealed clear boundaries of some auditory subnuclei including the dorsal and ventral cochlear nuclei and the lateral superior olivary nucleus. Differences in immunoreactivity were found between the central nucleus and the dorsal cortex of the inferior colliculus and between the dorsal and ventral parts of the ventral nucleus of the lateral lemniscus, although no clear boundaries were observed. No differences in immunoreactivity were found between the core and the belt areas of the auditory cortex and among the subdivisions of the medial geniculate nucleus. The regional distribution of the receptor subunit in auditory structures is consistent with inputs to these structures and the cellular localization of the receptor in auditory neurons supports the contribution of the GABA(B) receptor to synaptic responses in these neurons.

Effect of lapatinib on the development of estrogen receptor-negative mammary tumors in mice.

Lapatinib, a selective orally available inhibitor of epidermal growth factor receptor (EGFR) and ErbB2 receptor tyrosine kinases, is a promising agent for the treatment of breast cancer. We examined the effect of lapatinib on the development of mammary tumors in MMTV-erbB2 transgenic mice, which express wild-type ErbB2 under the control of the mouse mammary tumor virus promoter and spontaneously develop estrogen receptor (ER)-negative and ErbB2-positive mammary tumors by 14 months of age. Mice were treated from age 3 months to age 15 months with vehicle (n = 17) or lapatinib (30 or 75 mg/kg body weight; n = 16 mice per group) by oral gavage twice daily (6 d/wk). All statistical tests were two-sided. By 328 days after the start of treatment, all 17 (100%) of the vehicle-treated mice vs five (31%) of the 16 mice treated with high-dose lapatinib developed mammary tumors (P < .001). Among MMTV-erbB2 mice treated for 5 months (n = 20 mice per group), those treated with lapatinib had fewer premalignant lesions and noninvasive cancers in their mammary glands than those treated with vehicle (P = .02). Lapatinib also effectively blocked epidermal growth factor-induced signaling through the EGFR and ErbB2 receptors, suppressed cyclin D1 and epiregulin mRNA expression, and stimulated p27 mRNA expression in human mammary epithelial cells and in mammary epithelial cells from mice treated for 5 months with high-dose lapatinib. Thus, cyclin D1, epiregulin, and p27 may represent useful biomarkers of lapatinib response in patients. These data suggest that lapatinib is a promising agent for the prevention of ER-negative breast cancer.

The AP-1 transcription factor regulates postnatal mammary gland development.

The AP-1 transcription factor is activated by multiple growth factors that are critical regulators of breast cell proliferation. We previously demonstrated that AP-1 blockade inhibits breast cancer cell growth in vitro. Yet a specific role of AP-1 in normal mammary gland development has not been studied. Using a bi-transgenic mouse expressing an inducible AP-1 inhibitor (Tam67), we found that the AP-1 factor regulates postnatal proliferation of mammary epithelial cells. Mammary epithelial proliferation was significantly reduced after AP-1 blockade in adult, prepubertal, pubertal, and hormone-stimulated mammary glands. In pubertal mice, mammary cell proliferation was greatly reduced, and the cells that did proliferate failed to express Tam67. We also observed structural changes such as suppressed branching and budding, reduced gland tree size, and less fat pad occupancy in developing mammary glands after AP-1 blockade. We further demonstrated that Tam67 suppressed the expression of AP-1-dependent genes (TIMP-1, vimentin, Fra-1, and fibronectin) and the AP-1-dependent growth regulatory genes (cyclin D1 and c-myc) in AP-1-blocked mammary glands. We therefore conclude that AP-1 factor is a pivotal regulator of postnatal mammary gland growth and development.