Proteasome Inhibition Reprograms Chromatin Landscape in Breast Cancer.

The 26S proteasome is the major protein degradation machinery in cells. Cancer cells use the proteasome to modulate gene expression networks that promote tumor growth. Proteasome inhibitors have emerged as effective cancer therapeutics, but how they work mechanistically remains unclear. Here, using integrative genomic analysis, we discovered unexpected reprogramming of the chromatin landscape and RNA polymerase II (RNAPII) transcription initiation in breast cancer cells treated with the proteasome inhibitor MG132. The cells acquired dynamic changes in chromatin accessibility at specific genomic loci termed differentially open chromatin regions (DOCR). DOCRs with decreased accessibility were promoter proximal and exhibited unique chromatin architecture associated with divergent RNAPII transcription. Conversely, DOCRs with increased accessibility were primarily distal to transcription start sites and enriched in oncogenic superenhancers predominantly accessible in non-basal breast tumor subtypes. These findings describe the mechanisms by which the proteasome modulates the expression of gene networks intrinsic to breast cancer biology. SIGNIFICANCE: Our study provides a strong basis for understanding the mechanisms by which proteasome inhibitors exert anticancer effects. We find open chromatin regions that change during proteasome inhibition, are typically accessible in non-basal breast cancers.

Genomic insights into the population history and adaptive traits of Latin American Criollo cattle.

Criollo cattle, the descendants of animals brought by Iberian colonists to the Americas, have been the subject of natural and human-mediated selection in novel tropical agroecological zones for centuries. Consequently, these breeds have evolved distinct characteristics such as resistance to diseases and exceptional heat tolerance. In addition to European taurine (Bos taurus) ancestry, it has been proposed that gene flow from African taurine and Asian indicine (Bos indicus) cattle has shaped the ancestry of Criollo cattle. In this study, we analysed Criollo breeds from Colombia and Venezuela using whole-genome sequencing (WGS) and single-nucleotide polymorphism (SNP) array data to examine population structure and admixture at high resolution. Analysis of genetic structure and ancestry components provided evidence for African taurine and Asian indicine admixture in Criollo cattle. In addition, using WGS data, we detected selection signatures associated with a myriad of adaptive traits, revealing genes linked to thermotolerance, reproduction, fertility, immunity and distinct coat and skin coloration traits. This study underscores the remarkable adaptability of Criollo cattle and highlights the genetic richness and potential of these breeds in the face of climate change, habitat flux and disease challenges. Further research is warranted to leverage these findings for more effective and sustainable cattle breeding programmes.

Preconception Health of Indigenous Peoples in Australia, Canada, New Zealand, and the United States: A Scoping Review.

BACKGROUND: There is increasing recognition of the importance of the preconception period for addressing reproductive and intergenerational health inequities and supporting improved maternal and child health outcomes. This study aimed to understand the extent and type of evidence that exists in relation to preconception health for Indigenous peoples living in high-income countries with similar experiences of colonisation, namely, Australia, New Zealand, Canada, and the United States. METHODS: This review was conducted as per the JBI methodology and PRISMA Extension for Scoping Reviews. A comprehensive search of PubMed, CINAHL [EBSCO], Ovid Embase, Scopus, and the Wiley Cochrane Library was conducted using keywords and index terms. We included research in English published between January 2010 and June 2023 on quantitative and qualitative primary studies. Data were extracted using a standardised tool, and the analysis included quantitative descriptions and qualitative content analysis. RESULTS: We identified 360 potential studies and included 57 articles in the review. Most studies were from the United States (n = 36, 63.2%) and Australia (n = 13, 22.8%), and they commonly reported associations between preconception health risk factors and maternal or child health outcomes (n = 27, 48.2%) or described the development, implementation, or evaluation of preconception health interventions (n = 26, 46.4%). Common preconception health areas were pre-pregnancy body mass index or weight (n = 34), alcohol (n = 16), diet (n = 14), physical activity (n = 12), and diabetes (n = 11). Most studies focused exclusively on women (n = 46, 80.7%), and very few included men (n = 3, 5.3%). The study populations were mostly urban and rural (n = 25, 43.9%) or rural only (n = 14, 24.6%); however, the geographical remoteness was often unclear (n = 14, 24.6%). CONCLUSIONS: While there was some research relating to the preconception health of Indigenous peoples, this review identified considerable research gaps. There is a need for dedicated research into preconception health risk factors and reproductive health outcomes, attitudes and awareness of preconception health, and preconception health interventions for Indigenous peoples.

Indigenous data governance approaches applied in research using routinely collected health data: a scoping review.

Globally, there is a growing acknowledgment of Indigenous Peoples' rights to control data related to their communities. This is seen in the development of Indigenous Data Governance standards. As health data collection increases, it's crucial to apply these standards in research involving Indigenous communities. Our study, therefore, aims to systematically review research using routinely collected health data of Indigenous Peoples, understanding the Indigenous Data Governance approaches and the associated advantages and challenges. We searched electronic databases for studies from 2013 to 2022, resulting in 85 selected articles. Of these, 65 (77%) involved Indigenous Peoples in the research, and 60 (71%) were authored by Indigenous individuals or organisations. While most studies (93%) provided ethical approval details, only 18 (21%) described Indigenous guiding principles, 35 (41%) reported on data sovereignty, and 28 (33%) addressed consent. This highlights the increasing focus on Indigenous Data Governance in utilising health data. Leveraging existing data sources in line with Indigenous data governance principles is vital for better understanding Indigenous health outcomes.

BRG1 establishes the neuroectodermal chromatin landscape to restrict dorsal cell fates.

Cell fate decisions are achieved with gene expression changes driven by lineage-specific transcription factors (TFs). These TFs depend on chromatin remodelers including the Brahma-related gene 1 (BRG1)-associated factor (BAF) complex to activate target genes. BAF complex subunits are essential for development and frequently mutated in cancer. Thus, interrogating how BAF complexes contribute to cell fate decisions is critical for human health. We examined the requirement for the catalytic BAF subunit BRG1 in neural progenitor cell (NPC) specification from human embryonic stem cells. During the earliest stages of differentiation, BRG1 was required to establish chromatin accessibility at neuroectoderm-specific enhancers. Depletion of BRG1 dorsalized NPCs and promoted precocious neural crest specification and enhanced neuronal differentiation. These findings demonstrate that BRG1 mediates NPC specification by ensuring proper expression of lineage-specific TFs and appropriate activation of their transcriptional programs.

Patient and healthcare provider perceptions of acceptability of fingerstick point-of-care hepatitis C testing at Aboriginal Community Controlled Health Services in Australia.

BACKGROUND: Hepatitis C (HCV) is highly prevalent in First Nations communities globally. Barriers in the uptake of testing and treatment create challenges to realise elimination of HCV in these communities. In efforts to reduce barriers to testing and treatment, the SCALE-C study implemented an HCV test-and-treat intervention integrating point-of-care HCV testing and FibroScan®. SCALE-C was carried out at four Aboriginal Community Controlled Health Services (ACCHS; renowned for providing culturally safe care) in four regional towns in Australia. This qualitative analysis sought to understand healthcare provider and patient perceptions of acceptability of a community-based HCV test-and-treat intervention within ACCHS. METHODS: Semi-structured interviews were undertaken with 23 patient participants and 14 healthcare personnel (including Aboriginal Health Workers/Practitioners, nurses, general practitioners, and practice managers) from across the four ACCHS involved in SCALE-C. A coding framework was developed among study authors and informed by Sekhon's Theoretical Framework of Acceptability. RESULTS: The SCALE-C intervention enabled opportunities for healthcare providers to listen to patients, and for patients to feel heard (affective attitude). HCV testing was opportunistic and often occurred outside of the allocated SCALE-C clinical hours (burden). For patients, HCV testing within SCALE-C was viewed as a moral responsibility and ensured protection of self and others (ethicality). For personnel, SCALE-C (including following up visits) was regarded as an opportunity to engage with patients especially those with complex health needs which may be unrelated to HCV risk factors (ethicality). Patients and personnel widely regarded the SCALE-C intervention to be effective, and the test-and-treat model was preferable for both patients and personnel. CONCLUSION: The SCALE-C intervention was broadly perceived to be acceptable among both healthcare providers and patients within ACCHS. Whilst the prioritisation of HCV was viewed as increasing patient engagement, it was also regarded as an opportunity for addressing other healthcare needs within Aboriginal communities. HCV test-and-treat models of care delivered by ACCHS simplify the HCV care pathway and ensure all HCV care is provided in a culturally safe setting (e.g., patients did not need to attend external services such as pathology).

Comprehensive evaluation of smoking exposures and their interactions on DNA methylation.

BACKGROUND: Smoking impacts DNA methylation, but data are lacking on smoking-related differential methylation by sex or dietary intake, recent smoking cessation (<1 year), persistence of differential methylation from in utero smoking exposure, and effects of environmental tobacco smoke (ETS). METHODS: We meta-analysed data from up to 15,014 adults across 5 cohorts with DNA methylation measured in blood using Illumina's EPIC array for current smoking (2560 exposed), quit < 1 year (500 exposed), in utero (286 exposed), and ETS exposure (676 exposed). We also evaluated the interaction of current smoking with sex or diet (fibre, folate, and vitamin C). FINDINGS: Using false discovery rate (FDR < 0.05), 65,857 CpGs were differentially methylated in relation to current smoking, 4025 with recent quitting, 594 with in utero exposure, and 6 with ETS. Most current smoking CpGs attenuated within a year of quitting. CpGs related to in utero exposure in adults were enriched for those previously observed in newborns. Differential methylation by current smoking at 4-71 CpGs may be modified by sex or dietary intake. Nearly half (35-50%) of differentially methylated CpGs on the 450 K array were associated with blood gene expression. Current smoking and in utero smoking CpGs implicated 3049 and 1067 druggable targets, including chemotherapy drugs. INTERPRETATION: Many smoking-related methylation sites were identified with Illumina's EPIC array. Most signals revert to levels observed in never smokers within a year of cessation. Many in utero smoking CpGs persist into adulthood. Smoking-related druggable targets may provide insights into cancer treatment response and shared mechanisms across smoking-related diseases. FUNDING: Intramural Research Program of the National Institutes of Health, Norwegian Ministry of Health and Care Services and the Ministry of Education and Research, Chief Scientist Office of the Scottish Government Health Directorates and the Scottish Funding Council, Medical Research Council UK and the Wellcome Trust.

Rashba Metamaterials and Metasurfaces with Zero Reflectivity and Effect of Surface States in Ultrathin Metal Films.

Metals, renowned for their high reflectivity, find extensive use in various technological applications, from mirrors to optical coatings in radars, telescopes, and mobile communications. However, their potential in antireflective coatings has remained largely untapped. In this study, we demonstrate that by applying an ultrathin metallic film onto an oxide layer, we can achieve a flawless optical surface with zero reflectivity. This phenomenon has been successfully observed across various metals, including Sn, Ag, Au, Pt, Bi, and Nb, showcasing its broad applicability. The underlying principle lies in the emergence of surface states, where the Rashba effect is strong, which give rise to the formation of Rashba metamaterial and metasurface (RMM) structures. Remarkably, these RMMs can be fine-tuned to act as high-resolution Veselago lenses. To illustrate, we achieved zero reflectivity with an RMM consisting of a 1 nm thick Sn metal film on a 1 nm Ge buffer, situated on a 60 nm Al2O3/Si substrate. Similar results were observed for other metals (Pt, Au, Ag, and Nb) and semimetals (Bi) by adjusting the film thickness to 2, 3, 5, 10, and 6 nm, respectively. The revelation of RMMs with zero reflectivity (R = 0) has tremendous potential to revolutionize optical device technologies, covering renewable energy, optoelectronics, and the telecommunications industry.

APOBEC3G Is a p53-Dependent Restriction Factor in Respiratory Syncytial Virus Infection of Human Cells Included in the p53/Immune Axis.

Identifying and understanding genetic factors that influence the propagation of the human respiratory syncytial virus (RSV) can lead to health benefits and possibly augment recent vaccine approaches. We previously identified a p53/immune axis in which the tumor suppressor p53 directly regulates the expression of immune system genes, including the seven members of the APOBEC3 family of DNA cytidine deaminases (A3), which are innate immune sentinels against viral infections. Here, we examined the potential p53 and A3 influence in RSV infection, as well as the overall p53-dependent cellular and p53/immune axis responses to infection. Using a paired p53 model system of p53+ and p53- human lung tumor cells, we found that RSV infection activates p53, leading to the altered p53-dependent expression of A3D, A3F, and A3G, along with p53 site-specific binding. Focusing on A3G because of its 10-fold-greater p53 responsiveness to RSV, the overexpression of A3G can reduce RSV viral replication and syncytial formation. We also observed that RSV-infected cells undergo p53-dependent apoptosis. The study was expanded to globally address at the transcriptional level the p53/immune axis response to RSV. Nearly 100 genes can be directly targeted by the p53/immune axis during RSV infection based on our p53BAER analysis (Binding And Expression Resource). Overall, we identify A3G as a potential p53-responsive restriction factor in RSV infection. These findings have significant implications for RSV clinical and therapeutic studies and other p53-influenced viral infections, including using p53 adjuvants to boost the response of A3 genes.

Integrative and comparative genomic analyses of mammalian macrophage responses to intracellular mycobacterial pathogens.

Mycobacterium tuberculosis, the causative agent of human tuberculosis (hTB), is a close evolutionary relative of Mycobacterium bovis, which causes bovine tuberculosis (bTB), one of the most damaging infectious diseases to livestock agriculture. Previous studies have shown that the pathogenesis of bTB disease is comparable to hTB disease, and that the bovine and human alveolar macrophage (bAM and hAM, respectively) transcriptomes are extensively reprogrammed in response to infection with these intracellular mycobacterial pathogens. In this study, a multi-omics integrative approach was applied with functional genomics and GWAS data sets across the two primary hosts (Bos taurus and Homo sapiens) and both pathogens (M. bovis and M. tuberculosis). Four different experimental infection groups were used: 1) bAM infected with M. bovis, 2) bAM infected with M. tuberculosis, 3) hAM infected with M. tuberculosis, and 4) human monocyte-derived macrophages (hMDM) infected with M. tuberculosis. RNA-seq data from these experiments 24 h post-infection (24 hpi) was analysed using three computational pipelines: 1) differentially expressed genes, 2) differential gene expression interaction networks, and 3) combined pathway analysis. The results were integrated with high-resolution bovine and human GWAS data sets to detect novel quantitative trait loci (QTLs) for resistance to mycobacterial infection and resilience to disease. This revealed common and unique response macrophage pathways for both pathogens and identified 32 genes (12 bovine and 20 human) significantly enriched for SNPs associated with disease resistance, the majority of which encode key components of the NF-κB signalling pathway and that also drive formation of the granuloma.

Proteasome inhibition reprograms chromatin landscape in breast cancer.

The 26S proteasome is the major protein degradation machinery in cells. Cancer cells use the proteasome to modulate gene expression networks that promote tumor growth. Proteasome inhibitors have emerged as effective cancer therapeutics, but how they work mechanistically remains unclear. Here, using integrative genomic analysis, we discovered unexpected reprogramming of the chromatin landscape and RNAPII transcription initiation in breast cancer cells treated with the proteasome inhibitor MG132. The cells acquired dynamic changes in chromatin accessibility at specific genomic loci termed Differentially Open Chromatin Regions (DOCRs). DOCRs with decreased accessibility were promoter proximal and exhibited unique chromatin architecture associated with divergent RNAPII transcription. Conversely, DOCRs with increased accessibility were primarily distal to transcription start sites and enriched in oncogenic super enhancers predominantly accessible in non-basal breast tumor subtypes. These findings describe the mechanisms by which the proteasome modulates the expression of gene networks intrinsic to breast cancer biology. Highlights: Proteasome inhibition uncovers de novo Differential Open Chromatin Regions (DOCRs) in breast cancer cells. Proteasome inhibitor sensitive promoters exhibit a distinctive chromatin architecture with discrete transcription initiation patterns.Proteasome inhibition reprograms accessibility of super enhancers.Proteasome inhibitor sensitive super enhancers distinguish basal from non-basal breast cancer subtypes.

Unlocking cellular plasticity: Enhancing human iPSC reprogramming through bromodomain inhibition and extracellular matrix gene expression regulation.

The transformation of fibroblasts into epithelial cells is critical for iPSC reprogramming. In this report, we describe studies with PFI-3, a small molecule inhibitor that specifically targets the bromodomains of SMARCA2/4 and PBRM1 subunit of SWI/SNF complex, as an enhancer of iPSC reprogramming efficiency. Our findings revealed that PFI-3 induces cellular plasticity in multiple human dermal fibroblasts, leading to a mesenchymal-epithelial transition (MET) during iPSC formation. This transition was characterized by the upregulation of E-cadherin expression, a key protein involved in epithelial cell adhesion. Additionally, we identified COL11A1 as a reprogramming barrier and demonstrated COL11A1 knockdown increased reprogramming efficiency. Notably, we found that PFI-3 significantly reduced the expression of numerous extracellular matrix (ECM) genes, particularly those involved in collagen assembly. Our research provides key insights into the early stages of iPSC reprogramming, highlighting the crucial role of ECM changes and cellular plasticity in this process.

Selective MCL-1 inhibitor ABBV-467 is efficacious in tumor models but is associated with cardiac troponin increases in patients.

BACKGROUND: MCL-1 is a prosurvival B-cell lymphoma 2 family protein that plays a critical role in tumor maintenance and survival and can act as a resistance factor to multiple anticancer therapies. Herein, we describe the generation and characterization of the highly potent and selective MCL-1 inhibitor ABBV-467 and present findings from a first-in-human trial that included patients with relapsed/refractory multiple myeloma (NCT04178902). METHODS: Binding of ABBV-467 to human MCL-1 was assessed in multiple cell lines. The ability of ABBV-467 to induce tumor growth inhibition was investigated in xenograft models of human multiple myeloma and acute myelogenous leukemia. The first-in-human study was a multicenter, open-label, dose-escalation study assessing safety, pharmacokinetics, and efficacy of ABBV-467 monotherapy. RESULTS: Here we show that administration of ABBV-467 to MCL-1-dependent tumor cell lines triggers rapid and mechanism-based apoptosis. In vivo, intermittent dosing of ABBV-467 as monotherapy or in combination with venetoclax inhibits the growth of xenografts from human hematologic cancers. Results from a clinical trial evaluating ABBV-467 in patients with multiple myeloma based on these preclinical data indicate that treatment with ABBV-467 can result in disease control (seen in 1 patient), but may also cause increases in cardiac troponin levels in the plasma in some patients (seen in 4 of 8 patients), without other corresponding cardiac findings. CONCLUSIONS: The selectivity of ABBV-467 suggests that treatment-induced troponin release is a consequence of MCL-1 inhibition and therefore may represent a class effect of MCL-1 inhibitors in human patients.

Apoptosis is a type of cell death that removes abnormal cells from the body. Cancer cells can have increased levels of MCL-1, a protein that helps cells survive and prevents apoptosis. ABBV-467 is a new drug that blocks the action of MCL-1 (an MCL-1 inhibitor) and could promote apoptosis. In animal models, ABBV-467 led to cancer cell death and delayed tumor growth. ABBV-467 was also studied in a clinical trial in 8 patients with multiple myeloma, a blood cancer. In 1 patient, ABBV-467 treatment prevented the cancer from getting any worse for 8 months. However, in 4 out of 8 patients ABBV-467 increased the levels of troponin, a protein associated with damage to the heart. This concerning side effect may impact the future development of MCL-1 inhibitors as anticancer drugs.

Mapping pandemic responses in urban Indigenous Australia: Reflections on systems thinking and pandemic preparedness.

OBJECTIVES: We investigate some of the strengths and challenges associated with Covid-19 responses in urban Indigenous communities in Brisbane, Australia. Our research reflects on the interconnected dynamics that impact health outcomes and mitigate or exacerbate the risk of Covid-19 spreading within urban Indigenous communities. METHODS: Three systems thinking workshops were held in 2021 with Indigenous and non-Indigenous stakeholders (N15/workshop) from State and Federal services, along with Aboriginal Community Controlled Health Organisations. All worked in the urban Indigenous health sector. Stakeholders produced a Causal Loop Diagram (CLD) incorporating the critical feedbacks determining the dynamics influencing health outcomes. The aim of the research was to help stakeholders' build awareness of how the structure of the system influences health outcomes. RESULTS: Stakeholders identified 6 key dynamics which have a negative or positive impact on mitigating risks of Covid-19 infection. By mapping these dynamics within a CLD, 7 intervention points were identified. CONCLUSIONS: Systems thinking provides a useful tool in identifying the complexities associated with navigating health challenges, but further research is needed to develop frameworks that work in conjunction with Indigenous Australian methodologies. IMPLICATIONS FOR PUBLIC HEALTH: Indigenous voices and communities must lie central to health responses/policies for Indigenous peoples. When systems thinking is done by or in collaboration with stakeholders it provides a visual language that can help design public health policy. What can be ascertained is that their effectiveness is predicated on systems thinking's integration with Indigenous methodologies that acknowledges Indigenous self-determination and challenges Eurocentric representations of health and Indigeneity.

Integrating testing for sexually transmissible infections into annual health assessments for Aboriginal and Torres Strait Islander young people: a cross-sectional analysis.

BACKGROUND: In the context of an expanding syphilis epidemic, we assessed the integration of sexually transmissible infection (STI) testing within annual health assessments for Aboriginal and Torres Strait Islander young people aged 16-29years in Aboriginal Community Controlled Health Services between 2018 and 2020. METHODS: Using routinely collected electronic medical record data from a national sentinel surveillance system (ATLAS), we performed a cross-sectional analysis to calculate the proportion of assessments that integrated any or all of the tests for chlamydia, gonorrhoea, syphilis, and HIV. We used logistic regression to identify correlates of integration of any STI test. RESULTS: Of the 13 892 assessments, 23.8% (95% CI 23.1, 24.6) integrated a test for any STI and 11.5% (95% CI 10.9, 12.0) included all four STIs. Of assessments that included a chlamydia/gonorrhoea test, 66.9% concurrently included a syphilis test. Integration of any STI test was associated with patients aged 20-24years (OR 1.2, 95% CI 1.1-1.4) and 25-29years (OR 1.1, 95% CI 1.0-1.2) compared to 16-19years and patients residing in very remote (OR 4.2, 95% CI 3.7-4.8), remote (OR 2.4, 95% CI 2.1-2.8), and regional areas (OR 2.5, 95% CI 2.2-2.8) compared to metropolitan areas. There was no association with patient sex. CONCLUSIONS: Integration of STI testing into annual health assessments for Aboriginal and Torres Strait Islander young people was higher in remote areas where disease burden is greatest. Integration is similar in men and women, which contrasts with most studies that have found higher testing in women.

Psychosocial stress and methamphetamine use: A mixed-methods study of intersectional stigma and Aboriginal and Torres Strait Islander methamphetamine use.

BACKGROUND: Regular methamphetamine use can cause a range of physical, psychological and social harms. Stigma is one factor that impacts engagement and successful completion of treatment. In Australia, Aboriginal and Torres Strait Islander people who regularly use methamphetamine experience multiple stigmas, which further compounds access to treatment and quality of life. This paper explores the cumulative and compounding effects of participating in a stigmatised activity such as illicit drug use in relation to the stigma experienced by Aboriginal and Torres Strait Islander people as a population marginalised through colonisation. METHODS: Ten sites nationally participated in a cross-sectional survey measuring a range of factors including psychosocial stress in methamphetamine users. The survey sample size was 734, with 59% identifying as Aboriginal and Torres Strait Islander (n = 433). In addition, a total of 147 mainly Aboriginal and Torres Strait Islander people who use methamphetamine, community and family members, and service providers took part in a total of 19 focus groups and 7 interviews. RESULTS: Aboriginal and Torres Strait Islander participants experienced multiple psychosocial stressors at significantly higher rates than non-Indigenous participants. These stressors include diminished access to health care (33%), experiences of racism (34%), grief and sorrow (39%), worry for family (46%), and child welfare experiences (46%). The qualitative findings highlight the cumulative impact of historical, political and social stressors on an already stigmatised population. CONCLUSIONS: The findings of this unique analysis demonstrate the disruptive impact of methamphetamine use on the lives of those who use methamphetamines and their family members. They also illustrate challenges, such as stigma, that may confront those seeking assistance for drug-related issues. Aboriginal and Torres Strait Islander community involvement is necessary to provide support and education for the individual, the family, and the community as a whole. Stigma reduction is therefore a worthy target for intervention.

Impact of Anti-EGFR Therapies on HER2-Positive Metastatic Colorectal Cancer: A Systematic Literature Review and Meta-Analysis of Clinical Outcomes.

BACKGROUND: HER2 overexpression/amplification in patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC) may be associated with resistance to standard-of-care anti-EGFR therapies. Given the lack of comprehensive investigations into this association, we assessed the prognostic or predictive effect of HER2 amplification/overexpression on anti-EGFR treatment outcomes. METHODS: A systematic review of MEDLINE, Embase, and Cochrane Library (2001-2021) identified studies evaluating progression-free survival (PFS), overall response rate (ORR), and overall survival (OS) in HER2-positive vs. HER2-negative patients with RAS WT mCRC who received anti-EGFR treatments and whose HER2 status was known. Meta-analyses of proportions (ORR) and hazard ratios (PFS, OS) were performed using random-effect models with pre-specified sensitivity analyses. RESULTS: Five high-quality retrospective cohort studies were included in the meta-analyses representing 594 patients with mCRC. All patients received anti-EGFR treatment, either as monotherapy or in combination with chemotherapy. Meta-analysis of PFS demonstrated a 2.84-fold higher risk of death or progression (95% CI, 1.44-5.60) in patients with HER2-positive (vs. HER2-negative) RAS WT mCRC treated with anti-EGFR regimens. The odds of response to anti-EGFR treatment were 2-fold higher in HER2-negative vs. HER2-positive (odds ratio, 1.96 [95% CI, 1.10-3.48]). Differences in OS were not statistically significant. Sensitivity analyses confirmed the robustness of the base-case estimates. CONCLUSIONS: While this study could not account for all confounding factors, in patients with RAS WT mCRC who received anti-EGFR therapy, HER2 overexpression/amplification was associated with worse PFS and ORR and may therefore predict poorer outcomes. HER2 testing is important to inform treatment decisions and could optimize outcomes for patients.