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Resistance to radiotherapy is a major obstacle for effective cancer treatment. Both cancer-associated fibroblasts (CAF) within the tumor microenvironment (TME) and Notch signaling are implicated in radioresistance, but their potential interrelationship is unclear. Here, we report that irradiated samples obtained from luminal breast cancer patient tumors express higher levels of the Notch ligand Dll1 and have a greater number of αSMA- and FAP-expressing activated CAFs. Single cell transcriptomic profiles further revealed enrichment of an αSMA+ myofibroblastic subpopulation of CAF in Dll1+ tumors. In murine and human patient-derived xenograft models, Dll1+ tumor cells were more radioresistant than Dll1– tumor cells, and genetic and pharmacologic blocking of Dll1-mediated Notch signaling decreased the number of Dll1+ cancer stem cells (CSC) and CAFs and increased Dll1+ tumor cell radiosensitivity. Dll1+ cells recruited CAFs in an IL6-dependent fashion and promoted Wnt ligand secretion by Notch2/3-expressing CAFs, thereby driving Wnt/β-catenin–dependent increases in Dll1+ CSC function to promote metastasis. Treatment with the porcupine inhibitor LGK-974 that inhibits Wnt ligand secretion or pharmacologic blockade of IL6 or Dll1 suppressed CAF-dependent enhancement of Dll1+ CSC function and metastasis in radioresistant tumors. Together, these findings reveal an essential cross-talk between Dll1+ cancer cells and CAFs, which promotes metastasis and radioresistance, which could be therapeutically exploited to improve the outcome of patients with breast cancer. Significance: Dll1+ breast cancer cells activate Notch signaling in cancer-associated fibroblasts that increases Wnt ligand secretion and leads to β-catenin–driven radioresistance and metastasis, opening new therapeutic avenues for breast cancer.

Genomic analysis has recently identified multiple ESR1 gene translocations in estrogen receptor alpha–positive (ERα+) metastatic breast cancer (MBC) that encode chimeric proteins whereby the ESR1 ligand binding domain (LBD) is replaced by C-terminal sequences from many different gene partners. Here we functionally screened 15 ESR1 fusions and identified 10 that promoted estradiol-independent cell growth, motility, invasion, epithelial-to-mesenchymal transition, and resistance to fulvestrant. RNA sequencing identified a gene expression pattern specific to functionally active ESR1 gene fusions that was subsequently reduced to a diagnostic 24-gene signature. This signature was further examined in 20 ERα+ patient-derived xenografts and in 55 ERα+ MBC samples. The 24-gene signature successfully identified cases harboring ESR1 gene fusions and also accurately diagnosed the presence of activating ESR1 LBD point mutations. Therefore, the 24-gene signature represents an efficient approach to screening samples for the presence of diverse somatic ESR1 mutations and translocations that drive endocrine treatment failure in MBC.Significance:This study identifies a gene signature diagnostic for functional ESR1 fusions that drive poor outcome in advanced breast cancer, which could also help guide precision medicine approaches in patients harboring ESR1 mutations.

It includes Supplementary Methods, Supplementary Figures, Supplementary Tables, and Supplementary References

Supplementary Figures

Table S2 - Genes in immune cell clusters

Immunotherapy has potential to prevent and treat metastatic breast cancer, but strategies to enhance immune-mediated killing of metastatic tumors are urgently needed. We report that a ligand-independent isoform of Ron kinase (SF-Ron) is a key target to enhance immune infiltration and eradicate metastatic tumors. Host-specific deletion of SF-Ron caused recruitment of lymphocytes to micrometastases, augmented tumor-specific T-cell responses, and nearly eliminated breast cancer metastasis in mice. Lack of host SF-Ron caused stem-like TCF1+ CD4+ T cells with type I differentiation potential to accumulate in metastases and prevent metastatic outgrowth. There was a corresponding increase in tumor-specific CD8+ T cells, which were also required to eliminate lung metastases. Treatment of mice with a Ron kinase inhibitor increased tumor-specific CD8+ T cells and protected from metastatic outgrowth. These data provide a strong preclinical rationale to pursue small-molecule Ron kinase inhibitors for the prevention and treatment of metastatic breast cancer.Significance:The discovery that SF-Ron promotes antitumor immune responses has significant clinical implications. Therapeutic antibodies targeting full-length Ron may not be effective for immunotherapy; poor efficacy of such antibodies in trials may be due to their inability to block SF-Ron. Our data warrant trials with inhibitors targeting SF-Ron in combination with immunotherapy.This article is highlighted in the In This Issue feature, p. 2945

With the advancement of personalized cancer immunotherapies, new tools are needed to identify tumor antigens and evaluate T-cell responses in model systems, specifically those that exhibit clinically relevant tumor progression. Key transgenic mouse models of breast cancer are generated and maintained on the FVB genetic background, and one such model is the mouse mammary tumor virus-polyomavirus middle T antigen (MMTV-PyMT) mouse—an immunocompetent transgenic mouse that exhibits spontaneous mammary tumor development and metastasis with high penetrance. Backcrossing the MMTV-PyMT mouse from the FVB strain onto a C57BL/6 genetic background, in order to leverage well-developed C57BL/6 immunologic tools, results in delayed tumor development and variable metastatic phenotypes. Therefore, we initiated characterization of the FVB MHC class I H-2q haplotype to establish useful immunologic tools for evaluating antigen specificity in the murine FVB strain. Our study provides the first detailed molecular and immunoproteomic characterization of the FVB H-2q MHC class I alleles, including >8,500 unique peptide ligands, a multiallele murine MHC peptide prediction tool, and in vivo validation of these data using MMTV-PyMT primary tumors. This work allows researchers to rapidly predict H-2 peptide ligands for immune testing, including, but not limited to, the MMTV-PyMT model for metastatic breast cancer. Cancer Immunol Res; 6(6); 636–44. ©2018 AACR.

Table S1 - List of antibodies and reagents

Supplemental Table S1: AUC and PPV for NetH2pan network ensemble Supplemental Table S2: AUC and PPV for prediction of ligands by NetH2pan, trained with or without sequence context of five residues flanking the peptide. Supplemental Table S3. Yield (# of peptides) from soluble MHC transfectants and MMTV-PyMT tumors. Supplemental Table S4. Cancer-associated peptides eluted from MMTV-PyMT tumors. Supplemental Figure S1. MHC Class I peptide tissue extraction approach. Supplemental Figure S2. Peptide overlap with soluble MHC peptide elution and primary tumor cell elution. Supplemental Figure S3. MMTV-PyMT tumors express Class I MHC.

(A) 231 and 231DXR and (B) HCC and HCCDXR cells were treated with increasing concentrations of doxorubicin (50 - 350 nM) for 48h. Experiments were performed three times in triplicate. Results shown are mean {plus minus} SEM. *(p < 0.05), **(p < 0.01) and ***(p < 0.001) indicate levels of statistically significance.

cells (A) 231 and 231DXR and (B) HCC and HCCDXR cells were treated with increasing concentrations of cetuximab (0,5 - 4 µM), C75 (20 - 60 µM) or EGCG ( 25 - 150 µM) for 4 days. Results are expressed as mean {plus minus} SEM. Experiments were performed at least three times in triplicate. *(p < 0.05), **(p < 0.01) and ***(p < 0.001) indicate levels of statistically significance.

Summary of in vivo studies

Purpose: The frequently elevated activities of the c-src and c-yes products in human epithelial tumors suggest that these activated tyrosine kinases have tumorigenic functions analogous to the v-src and v-yes oncogene products. Studies of v-src–transformed fibroblasts have identified many of the effectors of this potent oncogene; however, because c-src and c-yes lack the mutational and promiscuous activities of their retroviral oncogene homologues, their presumptive tumorigenic functions in human epithelial tumors are more subtle, less well-defined, and await identification of possible effectors more directly relevant to epithelial cells.Experimental Design: We recently identified a transmembrane glycoprotein named Trask that is expressed in epithelial tissues but not fibroblasts and is phosphorylated by SRC kinases in mitotic epithelial cells. In this study, we have surveyed the expression and phosphorylation of Trask in many human epithelial cancer cell lines and surgical tissues and tumors.Results: Trask is widely expressed in human epithelial tissues, but its phosphorylation is tightly regulated and restricted to detached mitotic cells or cells undergoing physiologic shedding. However, abberant Trask phosphorylation is seen in many epithelial tumors from all stages including preinvasive, invasive, and metastatic tumors. Trask phosphorylation requires SRC kinases, and is also aberrantly hyperphosphorylated in the SRC-activated PyMT mouse epithelial tumors and dephosphorylated by the SRC inhibitor treatment of these tumors.Conclusions: The widespread phosphorylation of Trask in many human epithlelial cancers identifies a new potential effector of SRC kinases in human epithelial tumorigenesis.

(A) 231 and 231DXR and (B) HCC and HCCDXR cells were treated with doxorubicin (50-100-150nM) and C75 (20µM for HCC, HCCDXR; 40µM for 231, 231DXR) or the combination for 48h. (C) 231 and 231DXR and (D) HCC and HCCDXR cells were treated with doxorubicin (50-100-150nM), EGCG (100µM for 231, 231DXR; 120µM for HCC, HCCDXR) or the combination of both for 48h. Results shown are mean {plus minus} SEM. *(p < 0.05), **(p < 0.01) and ***(p < 0.001) indicate levels of statistically significance.

Supplementary Data from Phosphorylation of the src Epithelial Substrate Trask Is Tightly Regulated in Normal Epithelia but Widespread in Many Human Epithelial Cancers

Summary of RNA sequencing (RNA seq) data of the Met superfamily kinases in 4 breast PDX models.

Purpose: Triple-negative breast cancer (TNBC) lacks an approved targeted therapy. Despite initial good response to chemotherapy, 30% of the patients relapse within 5 years after treatment. EGFR overexpression is a common marker in TNBC, and its expression has been correlated with poor outcome. Inhibition of fatty acid synthase (FASN) activity leads to apoptosis of human carcinoma cells overexpressing FASN. We tested the hypothesis that blocking FASN in combination with anti-EGFR signaling agents would be an effective antitumor strategy in sensitive and chemoresistant TNBC.Experimental Design: Several TNBC cell lines and 29 primary tumors were included to determine whether FASN is a potential target in TNBC. Doxorubicin-resistant TNBC cell lines (231DXR and HCCDXR) have been developed and characterized in our laboratory. Cellular and molecular interactions of anti-FASN compounds (EGCG and C75) with cetuximab were analyzed. In vivo tumor growth inhibition was evaluated after cetuximab, EGCG, or the combination in TNBC orthoxenograft models.Results: TNBC cell lines showed overexpression of FASN enzyme and its inhibition correlated to FASN levels. FASN staining was observed in all of the 29 TNBC tumor samples. In vitro, EGCG and C75 plus cetuximab showed strong synergism in sensitive and chemoresistant cells. In vivo, the combination of EGCG with cetuximab displayed strong antitumor activity against the sensitive and chemoresistant TNBC orthoxenografts, without signs of toxicity.Conclusions: Our results show that the simultaneous blockade of FASN and EGFR is effective in preclinical models of sensitive and chemoresistant TNBC. Clin Cancer Res; 22(18); 4687–97. ©2016 AACR.

(A) Mice bearing 231 and (B) 231DXR xenografts were treated with saline (Control), EGCG (30mg/Kg, 3 days a week), cetuximab (0.5mg/mice 1 day a week) or the combination (EGCG plus cetuximab) for 12 days. (C) Mice bearing HCC and (D) HCCDXR xenografts were treated with saline (Control), EGCG (30mg/Kg, 3 days a week), cetuximab (100uL/mice 1 day a week) or the combination (EGCG plus cetuximab) for 10 days. Total volume is shown as (Final Volume - Initial Volume). Dots are mean of each experimental group and bars, SEM. *(p < 0.05), **(p < 0.01) and ***(p < 0.001) indicate levels of statistically significance.

A. MCF7 tumor growth rate in NOD/SCID mice implanted with beeswax E2 pellets, commercial 0.72 mg/60 days E2 pellets (Innovative Research of America) and control mice. Both, 0.72 mg/60 days E2 and beeswax E2 pellets equally supported estrogen dependent tumor growth. In contrast, control mice not supplemented with E2 pellets failed to grow tumors. B. Quantification of E2 plasma levels 10 days post implantation of E2 pellets in NOD/SCID mice. The beeswax pellets yielded mean E2 plasma levels of 84 pg/ml with very little variation, which are comparable plasma estrogen levels released from commercially available E2 pellets.

Supplementary Data from Dll1-Mediated Notch Signaling Drives Tumor Cell Cross-talk with Cancer-Associated Fibroblasts to Promote Radioresistance in Breast Cancer

(A) 231 and 231DXR and (B) HCC and HCCDXR. mRNA levels were obtained by Real-Time PCR and normalized against the β-actin gene. Results shown are mean {plus minus} SEM from 3 independent experiments.

TNBC Patients demographics and clinical characteristics (n=26).

(A) 231 and 231DXR cells were treated with increasing concentrations of EGCG ( 100 - 200 µM) or C75 (30 - 90 µM) for 48h. (B) HCC and HCCDXR cells were treated with increasing concentrations of EGCG ( 100 - 250 µM) or C75 (20 - 60 µM) for 48h. Results are expressed as mean {plus minus} SEM. Experiments were performed at least three times in triplicate.

Purpose: Recent studies have demonstrated that short-form Ron (sfRon) kinase drives breast tumor progression and metastasis through robust activation of the PI3K pathway. We reasoned that upfront, concurrent inhibition of sfRon and PI3K might enhance the antitumor effects of Ron kinase inhibitor therapy while also preventing potential therapeutic resistance to tyrosine kinase inhibitors (TKI).Experimental Design: We used patient-derived breast tumor xenografts (PDX) as high-fidelity preclinical models to determine the efficacy of single-agent or dual Ron/PI3K inhibition. We tested the Ron kinase inhibitor ASLAN002 with and without coadministration of the PI3K inhibitor NVP-BKM120 in hormone receptor–positive [estrogen receptor (ER)+/progesterone receptor (PR)+] breast PDXs with and without PIK3CA gene mutation.Results: Breast PDX tumors harboring wild-type PIK3CA showed a robust response to ASLAN002 as a single agent. In contrast, PDX tumors harboring mutated PIK3CA demonstrated partial resistance to ASLAN002, which was overcome with addition of NVP-BKM120 to the treatment regimen. We further demonstrated that concurrent inhibition of sfRon and PI3K in breast PDX tumors with wild-type PIK3CA provided durable tumor stasis after therapy cessation, whereas discontinuation of either monotherapy facilitated tumor recurrence.Conclusions: Our work provides preclinical rationale for targeting sfRon in patients with breast cancer, with the important stipulation that tumors harboring PIK3CA mutations may be partially resistant to Ron inhibitor therapy. Our data also indicate that tumors with wild-type PIK3CA are most effectively treated with an upfront combination of Ron and PI3K inhibitors for the most durable response. Clin Cancer Res; 21(24); 5588–600. ©2015 AACR.

Resistance to radiotherapy is a major obstacle for effective cancer treatment. Both cancer-associated fibroblasts (CAF) within the tumor microenvironment (TME) and Notch signaling are implicated in radioresistance, but their potential interrelationship is unclear. Here, we report that irradiated samples obtained from luminal breast cancer patient tumors express higher levels of the Notch ligand Dll1 and have a greater number of αSMA- and FAP-expressing activated CAFs. Single cell transcriptomic profiles further revealed enrichment of an αSMA+ myofibroblastic subpopulation of CAF in Dll1+ tumors. In murine and human patient-derived xenograft models, Dll1+ tumor cells were more radioresistant than Dll1– tumor cells, and genetic and pharmacologic blocking of Dll1-mediated Notch signaling decreased the number of Dll1+ cancer stem cells (CSC) and CAFs and increased Dll1+ tumor cell radiosensitivity. Dll1+ cells recruited CAFs in an IL6-dependent fashion and promoted Wnt ligand secretion by Notch2/3-expressing CAFs, thereby driving Wnt/β-catenin–dependent increases in Dll1+ CSC function to promote metastasis. Treatment with the porcupine inhibitor LGK-974 that inhibits Wnt ligand secretion or pharmacologic blockade of IL6 or Dll1 suppressed CAF-dependent enhancement of Dll1+ CSC function and metastasis in radioresistant tumors. Together, these findings reveal an essential cross-talk between Dll1+ cancer cells and CAFs, which promotes metastasis and radioresistance, which could be therapeutically exploited to improve the outcome of patients with breast cancer.Significance:Dll1+ breast cancer cells activate Notch signaling in cancer-associated fibroblasts that increases Wnt ligand secretion and leads to β-catenin–driven radioresistance and metastasis, opening new therapeutic avenues for breast cancer.

Representative co-IP Western blot showing interaction between sfRon and the p85a subunit of PI3K in MCF7-sfRon cells treated with DMSO or increasing amounts of ASALAN002, and in tumors harvested from NOD/SCID mice bearing HCI-011 (PIK3CAWT) PDX. Mice bearing PDXs received a single dose of ASLAN002 (50 mg/kg) or vehicle and tumors were harvested 3 h later. For co-immunprecipititation studies, whole-cell extracts were immunoprecipitated with anti-p85a antibody followed by Western blot with anti-Ron antibody. Results indicate that inhibition of sfRon in both MCF7 cells and PDX tumors leads to dissociation of p85a subunit of PI3K from sfRon. The mock IP represents the same conditions as the other IPs, but without inclusion of protein lysate.

XLSX file - 20K, Description and specifics regarding the ILC E2 geneset.

Supplementary Methods, Figures 1-7 from Protein Arginine Methyltransferase 5 Accelerates Tumor Growth by Arginine Methylation of the Tumor Suppressor Programmed Cell Death 4

PDF file - 89K, Expression of genes in the ILC E2 geneset in MCF-7 and MM134 cells following treatment with anti-estrogens.

PDF file - 53K, E2 regulation of ER target genes in ILC cells.

PDF file - 137K

PDF file - 165K, Cell viability assays following kinase inhibition.

Invasive lobular carcinoma (ILC) is a histologic subtype of breast cancer that is frequently associated with favorable outcomes, as approximately 90% of ILC express the estrogen receptor (ER). However, recent retrospective analyses suggest that patients with ILC receiving adjuvant endocrine therapy may not benefit as much as patients with invasive ductal carcinoma. On the basis of these observations, we characterized ER function and endocrine response in ILC models. The ER-positive ILC cell lines MDA MB 134VI (MM134) and SUM44PE were used to examine the ER-regulated transcriptome via gene expression microarray analyses and ER ChIP-Seq, and to examine response to endocrine therapy. In parallel, estrogen response was assessed in vivo in the patient-derived ILC xenograft HCI-013. We identified 915 genes that were uniquely E2 regulated in ILC cell lines versus other breast cancer cell lines, and a subset of these genes were also E2 regulated in vivo in HCI-013. MM134 cells were de novo tamoxifen resistant and were induced to grow by 4-hydroxytamoxifen, as well as other antiestrogens, as partial agonists. Growth was accompanied by agonist activity of tamoxifen on ER-mediated gene expression. Though tamoxifen induced cell growth, MM134 cells required fibroblast growth factor receptor (FGFR)-1 signaling to maintain viability and were sensitive to combined endocrine therapy and FGFR1 inhibition. Our observation that ER drives a unique program of gene expression in ILC cells correlates with the ability of tamoxifen to induce growth in these cells. Targeting growth factors using FGFR1 inhibitors may block survival pathways required by ILC and reverse tamoxifen resistance. Cancer Res; 74(5); 1463–74. ©2014 AACR.

XLSX file - 2042K, Lists for genes regulated by E2 in MM134 and SUM44 cells, and for categories of genes based on cell type specificity.

PDF file - 52K, Motif analysis of ER binding sites identified in MM134 by ChIP-seq.

XLSX file - 17K, Expression data from estrogen deprivation studies using PDX HCI-013.

Recent studies reveal that lateral mitochondrial transfer, the movement of mitochondria from one cell to another, can affect cellular and tissue homeostasis. Most of what we know about mitochondrial transfer stems from bulk cell studies and have led to the paradigm that functional transferred mitochondria restore bioenergetics and revitalize cellular functions to recipient cells with damaged or non-functional mitochondrial networks. However, we show that mitochondrial transfer also occurs between cells with functioning endogenous mitochondrial networks, but the mechanisms underlying how transferred mitochondria can promote such sustained behavioral reprogramming remain unclear. We report that unexpectedly, transferred macrophage mitochondria are dysfunctional and accumulate reactive oxygen species in recipient cancer cells. We further discovered that reactive oxygen species accumulation activates ERK signaling, promoting cancer cell proliferation. Pro-tumorigenic macrophages exhibit fragmented mitochondrial networks, leading to higher rates of mitochondrial transfer to cancer cells. Finally, we observe that macrophage mitochondrial transfer promotes tumor cell proliferation in vivo. Collectively these results indicate that transferred macrophage mitochondria activate downstream signaling pathways in a ROS-dependent manner in cancer cells, and provide a model of how sustained behavioral reprogramming can be mediated by a relatively small amount of transferred mitochondria in vitro and in vivo.

Models that recapitulate the complexity of human tumors are urgently needed to develop more effective cancer therapies. We report a bank of human patient-derived xenografts (PDXs) and matched organoid cultures from tumors that represent the greatest unmet need: endocrine-resistant, treatment-refractory and metastatic breast cancers. We leverage matched PDXs and PDX-derived organoids (PDxO) for drug screening that is feasible and cost-effective with in vivo validation. Moreover, we demonstrate the feasibility of using these models for precision oncology in real time with clinical care in a case of triple-negative breast cancer (TNBC) with early metastatic recurrence. Our results uncovered a Food and Drug Administration (FDA)-approved drug with high efficacy against the models. Treatment with this therapy resulted in a complete response for the individual and a progression-free survival (PFS) period more than three times longer than their previous therapies. This work provides valuable methods and resources for functional precision medicine and drug development for human breast cancer.

Although dormancy is thought to play a key role in the metastasis of breast tumor cells to the brain, our knowledge of the molecular mechanisms regulating disseminated tumor cell (DTC) dormancy in this organ is limited. Here using serial intravital imaging of dormant and metastatic triple-negative breast cancer lines, we identify escape from the single-cell or micrometastatic state as the rate-limiting step towards brain metastasis. We show that every DTC occupies a vascular niche, with quiescent DTCs residing on astrocyte endfeet. At these sites, astrocyte-deposited laminin-211 drives DTC quiescence by inducing the dystroglycan receptor to associate with yes-associated protein, thereby sequestering it from the nucleus and preventing its prometastatic functions. These findings identify a brain-specific mechanism of DTC dormancy and highlight the need for a more thorough understanding of tumor dormancy to develop therapeutic approaches that prevent brain metastasis.

Genomic analysis has recently identified multiple ESR1 gene translocations in estrogen receptor alpha–positive (ERα+) metastatic breast cancer (MBC) that encode chimeric proteins whereby the ESR1 ligand binding domain (LBD) is replaced by C-terminal sequences from many different gene partners. Here we functionally screened 15 ESR1 fusions and identified 10 that promoted estradiol-independent cell growth, motility, invasion, epithelial-to-mesenchymal transition, and resistance to fulvestrant. RNA sequencing identified a gene expression pattern specific to functionally active ESR1 gene fusions that was subsequently reduced to a diagnostic 24-gene signature. This signature was further examined in 20 ERα+ patient-derived xenografts and in 55 ERα+ MBC samples. The 24-gene signature successfully identified cases harboring ESR1 gene fusions and also accurately diagnosed the presence of activating ESR1 LBD point mutations. Therefore, the 24-gene signature represents an efficient approach to screening samples for the presence of diverse somatic ESR1 mutations and translocations that drive endocrine treatment failure in MBC. Significance: This study identifies a gene signature diagnostic for functional ESR1 fusions that drive poor outcome in advanced breast cancer, which could also help guide precision medicine approaches in patients harboring ESR1 mutations.

3D patient tumor avatars (3D-PTAs) hold promise for next-generation precision medicine. Here, we describe the benefits and challenges of 3D-PTA technologies and necessary future steps to realize their potential for clinical decision making. 3D-PTAs require standardization criteria and prospective trials to establish clinical benefits. Innovative trial designs that combine omics and 3D-PTA readouts may lead to more accurate clinical predictors, and an integrated platform that combines diagnostic and therapeutic development will accelerate new treatments for patients with refractory disease.

Estrogen receptor α (ER) mutations occur in up to 30% of metastatic ER-positive breast cancers. Recent data has shown that ER mutations impact the expression of thousands of genes not typically regulated by wildtype ER. While the majority of these altered genes can be explained by constant activity of mutant ER or genomic changes such as altered ER binding and chromatin accessibility, as much as 33% remain unexplained, indicating the potential for post-transcriptional effects. Here we explored the role of microRNAs in mutant ER-driven gene regulation and identified several microRNAs that are dysregulated in ER mutant cells. These differentially regulated microRNAs target a significant portion of mutant-specific genes involved in key cellular processes. When the activity of microRNAs is altered using mimics or inhibitors, significant changes are observed in gene expression and cellular proliferation related to mutant ER. An in-depth evaluation of miR-301b led us to discover an important role forPRKD3in the proliferation of ER mutant cells. Our findings show that microRNAs contribute to mutant ER gene regulation and cellular effects in breast cancer cells.

TNBC is a heterogeneous subtype of breast cancer, and only a subset of TNBC can be established as PDXs. Here, we show that there is an engraftment bias toward TNBC with low levels of immune cell infiltration. Additionally, TNBC that failed to engraft show gene expression consistent with a cancer-promoting immunological state, leading us to hypothesize that the immunological state of the tumor and possibly the state of the immune system of the host may be essential for engraftment.

Development of candidate cancer treatments is a resource-intensive process, with the research community continuing to investigate options beyond static genomic characterization. Toward this goal, we have established the genomic landscapes of 536 patient-derived xenograft (PDX) models across 25 cancer types, together with mutation, copy number, fusion, transcriptomic profiles, and NCI-MATCH arms. Compared with human tumors, PDXs typically have higher purity and fit to investigate dynamic driver events and molecular properties via multiple time points from same case PDXs. Here, we report on dynamic genomic landscapes and pharmacogenomic associations, including associations between activating oncogenic events and drugs, correlations between whole-genome duplications and subclone events, and the potential PDX models for NCI-MATCH trials. Lastly, we provide a web portal having comprehensive pan-cancer PDX genomic profiles and source code to facilitate identification of more druggable events and further insights into PDXs’ recapitulation of human tumors., Patient-derived xenograft models (PDX) have been extensively used to study the molecular and clinical features of cancers. Here the authors present a cohort of 536 PDX models from 25 cancers, as well as their genomic and evolutionary profiles and their suitability for clinical trials.

Including patient advocates in basic cancer research ensures that breast cancer research is intentional, supports effective communication with broader audiences, and directly connects researchers with those who they are striving to help. Despite this utility, many cancer research scientists do not work with patient advocates. To understand barriers to engagement and build a framework for enhanced interactions in the future, we hosted a workshop with patient advocates and researchers who do engage, then discussed findings at an international metastatic breast cancer conference to solicit additional feedback and suggestions. Findings demonstrate that researchers are uncertain about how to initiate and maintain relationships with advocates. We offer actionable steps to support researchers working with patient advocates to improve cancer research and accomplish our collective goal of improving lives of those who have been diagnosed with breast cancer. We hope that this initiative will facilitate such collaborative efforts.

Patient-derived xenografts (PDXs) model human intra-tumoral heterogeneity in the context of the intact tissue of immunocompromised mice. Histological imaging via hematoxylin and eosin (H&E) staining is performed on PDX samples for routine assessment and, in principle, captures the complex interplay between tumor and stromal cells. Deep learning (DL)-based analysis of large human H&E image repositories has extracted inter-cellular and morphological signals correlated with disease phenotype and therapeutic response. Here, we present an extensive, pan-cancer repository of nearly 1,000 PDX and paired human progenitor H&E images. These images, curated from the PDXNet consortium, are associated with genomic and transcriptomic data, clinical metadata, pathological assessment of cell composition, and, in several cases, detailed pathological annotation of tumor, stroma, and necrotic regions. We demonstrate that DL can be applied to these images to classify tumor regions with an accuracy of 0.87. Further, we show that DL can predict xenograft-transplant lymphoproliferative disorder, the unintended outgrowth of human lymphocytes at the transplantation site, with an accuracy of 0.97. This repository enables PDX-specific investigations of cancer biology through histopathological analysis and contributes important model system data that expand on existing human histology repositories. We expect the PDXNet Image Repository to be valuable for controlled digital pathology analysis, both for the evaluation of technical issues such as stain normalization and for development of novel computational methods based on spatial behaviors within cancer tissues. Citation Format: Brian S. White, Xing Yi Woo, Soner Koc, Todd Sheridan, Steven B. Neuhauser, Shidan Wang, Yvonne A. Evrard, John David Landua, R Jay Mashl, Sherri R. Davies, Bingliang Fang, Maria Gabriela Raso, Kurt W. Evans, Matthew H. Bailey, Yeqing Chen, Min Xiao, Jill Rubinstein, Ali Foroughi pour, Lacey Elizabeth Dobrolecki, Maihi Fujita, Junya Fujimoto, Guanghua Xiao, Ryan C. Fields, Jacqueline L. Mudd, Xiaowei Xu, Melinda G. Hollingshead, Shahanawaz Jiwani, PDXNet consortium, Tiffany A. Wallace, Jeffrey A. Moscow, James H. Doroshow, Nicholas Mitsiades, Salma Kaochar, Chong-xian Pan, Moon S. Chen, Luis G. Carvajal-Carmona, Alana L. Welm, Bryan E. Welm, Ramaswamy Govindan, Shunqiang Li, Michael A. Davies, Jack A. Roth, Funda Meric-Bernstam, Yang Xie, Meenhard Herlyn, Li Ding, Michael T. Lewis, Carol J. Bolt, Dennis A. Dean, Jeffrey H. Chuang. A pan-cancer PDX histology image repository with genomic and pathological annotations for deep learning analysis. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5407.