NR4A1 regulates expression of immediate early genes, suppressing replication stress in cancer.

Deregulation of oncogenic signals in cancer triggers replication stress. Immediate early genes (IEGs) are rapidly and transiently expressed following stressful signals, contributing to an integrated response. Here, we find that the orphan nuclear receptor NR4A1 localizes across the gene body and 3' UTR of IEGs, where it inhibits transcriptional elongation by RNA Pol II, generating R-loops and accessible chromatin domains. Acute replication stress causes immediate dissociation of NR4A1 and a burst of transcriptionally poised IEG expression. Ectopic expression of NR4A1 enhances tumorigenesis by breast cancer cells, while its deletion leads to massive chromosomal instability and proliferative failure, driven by deregulated expression of its IEG target, FOS. Approximately half of breast and other primary cancers exhibit accessible chromatin domains at IEG gene bodies, consistent with this stress-regulatory pathway. Cancers that have retained this mechanism in adapting to oncogenic replication stress may be dependent on NR4A1 for their proliferation.

Creation of an asynchronous faculty development curriculum on well-written narrative assessments that avoid bias.

BACKGROUND: The COVID-19 pandemic in parallel with concerns about bias in grading resulted in many medical schools adopting pass/fail clinical grading and relying solely on narrative assessments. However, narratives often contain bias and lack specificity. The purpose of this project was to develop asynchronous faculty development to rapidly educate/re-educate > 2000 clinical faculty spread across geographic sites and clinical disciplines on components of a well-written narrative and methods to minimize bias in the assessment of students. METHODS: We describe creation, implementation, and pilot data outcomes for an asynchronous faculty development curriculum created by a committee of volunteer learners and faculty. After reviewing the literature on the presence and impact of bias in clinical rotations and ways to mitigate bias in written narrative assessments, the committee developed a web-based curriculum using multimedia learning theory and principles of adult learning. Just-in-time supplemental materials accompanied the curriculum. The Dean added completion of the module by 90% of clinical faculty to the department chairperson's annual education metric. Module completion was tracked in a learning management system, including time spent in the module and the answer to a single text entry question about intended changes in behavior. Thematic analysis of the text entry question with grounded theory and inductive processing was used to define themes of how faculty anticipate future teaching and assessment as a result of this curricula. OUTCOMES: Between January 1, 2021, and December 1, 2021, 2166 individuals completed the online module; 1820 spent between 5 and 90 min on the module, with a median time of 17 min and an average time of 20.2 min. 15/16 clinical departments achieved completion by 90% or more faculty. Major themes included: changing the wording of future narratives, changing content in future narratives, and focusing on efforts to change how faculty teach and lead teams, including efforts to minimize bias. CONCLUSIONS: We developed a faculty development curriculum on mitigating bias in written narratives with high rates of faculty participation. Inclusion of this module as part of the chair's education performance metric likely impacted participation. Nevertheless, time spent in the module suggests that faculty engaged with the material. Other institutions could easily adapt this curriculum with provided materials.

Differential Kinase Activity Across Prostate Tumor Compartments Defines Sensitivity to Target Inhibition.

Cancer therapy often results in heterogeneous responses in different metastatic lesions in the same patient. Inter- and intratumor heterogeneity in signaling within various tumor compartments and its impact on therapy are not well characterized due to the limited sensitivity of single-cell proteomic approaches. To overcome this barrier, we applied single-cell mass cytometry with a customized 26-antibody panel to PTEN-deleted orthotopic prostate cancer xenograft models to measure the evolution of kinase activities in different tumor compartments during metastasis or drug treatment. Compared with primary tumors and circulating tumor cells (CTC), bone metastases, but not lung and liver metastases, exhibited elevated PI3K/mTOR signaling and overexpressed receptor tyrosine kinases (RTK) including c-MET protein. Suppression of c-MET impaired tumor growth in the bone. Intratumoral heterogeneity within tumor compartments also arose from highly proliferative EpCAM-high epithelial cells with increased PI3K and mTOR kinase activities coexisting with poorly proliferating EpCAM-low mesenchymal populations with reduced kinase activities; these findings were recapitulated in epithelial and mesenchymal CTC populations in patients with metastatic prostate and breast cancer. Increased kinase activity in EpCAM-high cells rendered them more sensitive to PI3K/mTOR inhibition, and drug-resistant EpCAM-low populations with reduced kinase activity emerged over time. Taken together, single-cell proteomics indicate that microenvironment- and cell state-dependent activation of kinase networks create heterogeneity and differential drug sensitivity among and within tumor populations across different sites, defining a new paradigm of drug responses to kinase inhibitors. SIGNIFICANCE: Single-cell mass cytometry analyses provide insights into the differences in kinase activities across tumor compartments and cell states, which contribute to heterogeneous responses to targeted therapies.

HIF1A signaling selectively supports proliferation of breast cancer in the brain.

Blood-borne metastasis to the brain is a major complication of breast cancer, but cellular pathways that enable cancer cells to selectively grow in the brain microenvironment are poorly understood. We find that cultured circulating tumor cells (CTCs), derived from blood samples of women with advanced breast cancer and directly inoculated into the mouse frontal lobe, exhibit striking differences in proliferative potential in the brain. Derivative cell lines generated by serial intracranial injections acquire selectively increased proliferative competency in the brain, with reduced orthotopic tumor growth. Increased Hypoxia Inducible Factor 1A (HIF1A)-associated signaling correlates with enhanced proliferation in the brain, and shRNA-mediated suppression of HIF1A or drug inhibition of HIF-associated glycolytic pathways selectively impairs brain tumor growth while minimally impacting mammary tumor growth. In clinical specimens, brain metastases have elevated HIF1A protein expression, compared with matched primary breast tumors, and in patients with brain metastases, hypoxic signaling within CTCs predicts decreased overall survival. The selective activation of hypoxic signaling by metastatic breast cancer in the brain may have therapeutic implications.

Deregulation of ribosomal protein expression and translation promotes breast cancer metastasis.

Circulating tumor cells (CTCs) are shed into the bloodstream from primary tumors, but only a small subset of these cells generates metastases. We conducted an in vivo genome-wide CRISPR activation screen in CTCs from breast cancer patients to identify genes that promote distant metastasis in mice. Genes coding for ribosomal proteins and regulators of translation were enriched in this screen. Overexpression of RPL15, which encodes a component of the large ribosomal subunit, increased metastatic growth in multiple organs and selectively enhanced translation of other ribosomal proteins and cell cycle regulators. RNA sequencing of freshly isolated CTCs from breast cancer patients revealed a subset with strong ribosome and protein synthesis signatures; these CTCs expressed proliferation and epithelial markers and correlated with poor clinical outcome. Therapies targeting this aggressive subset of CTCs may merit exploration as potential suppressors of metastatic progression.

SETD1A protects from senescence through regulation of the mitotic gene expression program.

SETD1A, a Set1/COMPASS family member maintaining histone-H3-lysine-4 (H3K4) methylation on transcriptionally active promoters, is overexpressed in breast cancer. Here, we show that SETD1A supports mitotic processes and consequentially, its knockdown induces senescence. SETD1A, through promoter H3K4 methylation, regulates several genes orchestrating mitosis and DNA-damage responses, and its depletion causes chromosome misalignment and segregation defects. Cell cycle arrest in SETD1A knockdown senescent cells is independent of mutations in p53, RB and p16, known senescence mediators; instead, it is sustained through transcriptional suppression of SKP2, which degrades p27 and p21. Rare cells escaping senescence by restoring SKP2 expression display genomic instability. In > 200 cancer cell lines and in primary circulating tumor cells, SETD1A expression correlates with genes promoting mitosis and cell cycle suggesting a broad role in suppressing senescence induced by aberrant mitosis. Thus, SETD1A is essential to maintain mitosis and proliferation and its suppression unleashes the tumor suppressive effects of senescence.

AR Expression in Breast Cancer CTCs Associates with Bone Metastases.

Molecular drivers underlying bone metastases in human cancer are not well understood, in part due to constraints in bone tissue sampling. Here, RNA sequencing was performed of circulating tumor cells (CTC) isolated from blood samples of women with metastatic estrogen receptor (ER)+ breast cancer, comparing cases with progression in bone versus visceral organs. Among the activated cellular pathways in CTCs from bone-predominant breast cancer is androgen receptor (AR) signaling. AR gene expression is evident, as is its constitutively active splice variant AR-v7. AR expression within CTCs is correlated with the duration of treatment with aromatase inhibitors, suggesting that it contributes to acquired resistance to endocrine therapy. In an established breast cancer xenograft model, a bone-tropic derivative displays increased AR expression, whose genetic or pharmacologic suppression reduces metastases to bone but not to lungs. Together, these observations identify AR signaling in CTCs from women with bone-predominant ER+ breast cancer, and provide a rationale for testing androgen inhibitors in this subset of patients.Implications: This study highlights a role for the AR in breast cancer bone metastasis, and suggests that therapeutic targeting of the AR may benefit patients with metastatic breast cancer. Mol Cancer Res; 16(4); 720-7. ©2018 AACR.