Exemestane plus everolimus and palbociclib in metastatic breast cancer: clinical response and genomic/transcriptomic determinants of resistance in a phase I/II trial

The landscape of cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) resistance is still being elucidated and the optimal subsequent therapy to overcome resistance remains uncertain. Here we present the final results of a phase Ib/IIa, open-label trial (NCT02871791) of exemestane plus everolimus and palbociclib for CDK4/6i-resistant metastatic breast cancer. The primary objective of phase Ib was to evaluate safety and tolerability and determine the maximum tolerated dose/recommended phase II dose (100 mg palbociclib, 5 mg everolimus, 25 mg exemestane). The primary objective of phase IIa was to determine the clinical benefit rate (18.8%, n = 6/32), which did not meet the predefined endpoint (65%). Secondary objectives included pharmacokinetic profiling (phase Ib), objective response rate, disease control rate, duration of response, and progression free survival (phase IIa), and correlative multi-omics analysis to investigate biomarkers of resistance to CDK4/6i. All participants were female. Multi-omics data from the phase IIa patients (n = 24 tumor/17 blood biopsy exomes; n = 27 tumor transcriptomes) showed potential mechanisms of resistance (convergent evolution of HER2 activation, BRAFV600E), identified joint genomic/transcriptomic resistance features (ESR1 mutations, high estrogen receptor pathway activity, and a Luminal A/B subtype; ERBB2/BRAF mutations, high RTK/MAPK pathway activity, and a HER2-E subtype), and provided hypothesis-generating results suggesting that mTOR pathway activation correlates with response to the trial's therapy. Our results illustrate how genome and transcriptome sequencing may help better identify patients likely to respond to CDK4/6i therapies.

A spatial cell atlas of neuroblastoma reveals developmental, epigenetic and spatial axis of tumor heterogeneity

Neuroblastoma is a pediatric cancer arising from the developing sympathoadrenal lineage with complex inter- and intra-tumoral heterogeneity. To chart this complexity, we generated a comprehensive cell atlas of 55 neuroblastoma patient tumors, collected from two pediatric cancer institutions, spanning a range of clinical, genetic, and histologic features. Our atlas combines single-cell/nucleus RNA-seq (sc/scRNA-seq), bulk RNA-seq, whole exome sequencing, DNA methylation profiling, spatial transcriptomics, and two spatial proteomic methods. Sc/snRNA-seq revealed three malignant cell states with features of sympathoadrenal lineage development. All of the neuroblastomas had malignant cells that resembled sympathoblasts and the more differentiated adrenergic cells. A subset of tumors had malignant cells in a mesenchymal cell state with molecular features of Schwann cell precursors. DNA methylation profiles defined four groupings of patients, which differ in the degree of malignant cell heterogeneity and clinical outcomes. Using spatial proteomics, we found that neuroblastomas are spatially compartmentalized, with malignant tumor cells sequestered away from immune cells. Finally, we identify spatially restricted signaling patterns in immune cells from spatial transcriptomics. To facilitate the visualization and analysis of our atlas as a resource for further research in neuroblastoma, single cell, and spatial-omics, all data are shared through the Human Tumor Atlas Network Data Commons at www.humantumoratlas.org.

Abstract P4-01-06: Genomic and transcriptomic analysis reveals known and novel resistance mechanisms to CDK4/6 inhibitors and sensitivity factors for the response to triplet therapy (palbociclib + everolimus + exemestane) in a phase I/IIb study in hormone-receptor positive (HR+)/HER2- metastatic breast cancer (MBC) after progression on a CDK4/6 inhibitor (CDK4/6i)

Background: Multiple studies in HR+/HER2- MBC have identified a variety of genomic resistance mechanisms to CDK4/6 inhibitors, but the complete landscape of resistance mechanisms is still being elucidated. A clinical trial evaluating the benefit of continued CDK4/6 blockade after disease progression on a prior CDK4/6i provides a unique setting to study the landscape of resistance to CDK4/6 inhibitors. Methods: We analyzed genomic data from a Phase I/II trial (NCT02871791) of triplet therapy: palbociclib (CDK4/6i) + everolimus (mTOR inhibitor) + exemestane (endocrine therapy) in patients (pts) with HR+/HER2− MBC who had progressed on prior CDK4/6i. For the phase IIa pts, a research tumor biopsy at baseline and serial research blood collection for circulating tumor DNA (ctDNA) analysis were mandatory. Additionally, when possible, we acquired tumor biopsies that preceded the patient's prior exposure to a CDK4/6i, which would allow us to identify acquired genomic resistance mechanisms to the prior CDK4/6i. The genomic data consisted of whole exome sequencing (WES) data from 23 tumor biopsies (19 pts) and 17 ctDNA samples (12 pts), and RNA sequencing (RNA-seq) from 27 tumors (22 pts). 4 pts had a biopsy or ctDNA sample at baseline and a biopsy that preceded their prior exposure to a CDK4/6i. WES data was used to identify mutations and copy number alterations, which was used to perform evolutionary analysis on the pts with multiple biopsies or ctDNA samples. RNA-seq data was used to make research-grade PAM50 calls and calculate gene expression signature scores. Results: For the baseline biopsy or ctDNA sample of most pts, we found genomic alterations in previously identified pathways and genes that could explain the tumor’s resistance to the prior CDK4/6i (16/19 pts) or to the prior endocrine therapies (17/19 pts). These pathways and genes include the PI3K/AKT/MTOR pathway (e.g. PTEN, AKT), the RAS/MAPK pathway (e.g. NF1), receptor tyrosine kinases (RTKs) (e.g. ERBB2, FGFR1), cell-cycle genes (e.g. RB1), and estrogen receptor signaling (e.g. ESR1, FOXA1). Two novel potential genomic resistance mechanisms in these pathways were identified: an activating MTOR T1977R mutation (PI3K/AKT/MTOR pathway) and an activating BRAF V600E mutation (RAS/MAPK pathway). Notably, the patient with the activating MTOR mutation responded to the triplet therapy (progression free survival of 8 months), consistent with prior work linking these mutations to sensitivity to everolimus. Evolutionary analysis revealed metastatic tumors with distinct lineages but derived from the same primary tumor (e.g. two lineages, one with activating ESR1 mutations and one with an activating MTOR mutation), some of which converged to activating the same pathway (e.g. two lineages with distinct activating ERBB2 mutations). Transcriptomic analysis found that activating mutations in ERBB2 and BRAF were correlated with the HER2-E PAM50 and that the expression signatures for MTOR and RTKs were correlated with clinical benefit to triplet therapy. Conclusions: Analysis of the genomic and transcriptomic data of baseline biopsies and ctDNA samples from NCT02871791 not only recapitulates genes and pathways previously implicated in resistance to endocrine therapy and CDK4/6i but also identified novel potential mechanisms of resistance including activating mutations in BRAF and MTOR. Evolutionary analysis demonstrates the complexity of resistance including both convergent and divergent paths to resistance. Integration of genomic and transcriptomic data may better identify pts likely to respond to CDK4/6i combinations.

Citation Format: Jorge Gomez Tejeda Zanudo, Romualdo Barroso-Sousa, Esha Jain, Jorge Buendia-Buendia, Tianyu Li, Nabihah Tayob, Rebecca Rees, Alyssa Pereslete, Arlindo R. Ferreira, Daniel L. Abravanel, Karla Helvie, Ann H. Partridge, Beth Overmoyer, Eric P. Winer, Nikhil Wagle, Sara M. Tolaney. Genomic and transcriptomic analysis reveals known and novel resistance mechanisms to CDK4/6 inhibitors and sensitivity factors for the response to triplet therapy (palbociclib + everolimus + exemestane) in a phase I/IIb study in hormone-receptor positive (HR+)/HER2- metastatic breast cancer (MBC) after progression on a CDK4/6 inhibitor (CDK4/6i) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-01-06.

Abstract PD6-03: Spatio-molecular dissection of the breast cancer metastatic microenvironment

Metastatic breast cancer (MBC) remains incurable due to inevitable development of therapeutic resistance. Although tumor cell intrinsic mechanisms of resistance in MBC are beginning to be elucidated by bulk sequencing studies, the roles of the tumor microenvironment and intratumor heterogeneity in therapeutic resistance remain underexplored due to both technological barriers and limited availability of samples. To comprehensively capture these characteristics we have adapted a research biopsy protocol to collect tissue for an array of single-cell and spatio-molecular assays whose performance we have optimized for MBC, including single-cell and single-nucleus RNA sequencing, Slide-Seq, Multiplexed Error-Robust FISH (MERFISH), Expansion Sequencing (ExSEQ), Co-detection by Indexing (CODEX) and Multiplexed Ion Beam Imaging (MIBI). To date, we have successfully performed single-cell or single-nucleus RNAseq in 67 MBC biopsies and generated detailed accompanying clinical annotations for each. These samples provide a representation of the clinicopathological diversity of MBC including different breast cancer subtypes (44 HR+/HER2-, 3 HR-/HER2+, 3 HR+/HER2+, 16 TNBC, 1 unknown), common anatomic sites of metastasis (37 liver, 9 axilla, 7 breast, 5 bone, 3 chest wall, 3 neck, 1 brain, 1 lung, 1 skin), metastatic presentations (53 recurrent, 14 de novo) and histologic subtypes in the breast (45 IDC, 7 ILC, 6 mixed, 3 DCIS, 1 mucinous, 5 unknown/NA). Following optimization, both single-cell and single-nucleus RNA seq perform well in these MBC biopsies recovering all expected cell types including the malignant, stromal (e.g. fibroblasts, endothelial cells), myeloid (e.g. monocytes, macrophages) and lymphoid compartments (e.g. T cells, B cells, NK cells) as well as relevant oncogenic programs (e.g. cell cycle programs in all compartments; EMT-like and ER signaling programs in the malignant compartment, immune checkpoint programs in the lymphoid compartment; and fibroblast activation and vascular homeostasis programs in the stromal compartment). In addition to differences between the two techniques, these data demonstrate substantial intratumor heterogeneity in cell type composition. For example in liver biopsies the average number of cells per sample compartment by single nucleus RNA-seq was 6745 malignant (56%, SD 4216), 4637 stromal (41%, SD 3727), 1196 lymphoid (8%, SD 1617) and 874 myeloid (6%, SD 852); in breast biopsies the average number of cells per compartment by single nucleus RNA-seq was 6421 malignant (70%, SD 3497), 1628 stromal (24%, SD 117), 333 lymphoid (4%, SD 170) and 213 myeloid (3%, SD 117). Additionally, we find both inter- and intra-tumor heterogeneity in expression patterns and programs including, for example, expression of ER, PR and HER2 within clinical receptor subtypes (log normalized counts for ER expression in tumor cells by single cell RNA-seq: HR+/HER2- 0.921 (SD 0.714); HR+/HER2+ 0.768 (SD 0.624); HR-/HER2+ 0.018 (SD 0.122); and HR-/HER2- 0.005 (SD 0.066). For a subset of 13 biopsies we are also completing the spatiomolecular characterization methods on serial sections of a single adjacent biopsy. This unique experimental setup was designed to enable efficient comparison and integration of these assays. In spite of differences between experimental techniques and readouts, cell typing can be approached by annotation transfer from matching single cell or single nucleus RNAseq data, enabling exploratory analyses including evaluation of spatial phenotypes and cell type colocalization. Overall, these single cell and spatial data afford a comprehensive atlas including cell types, cell states/programs, cell interactions and spatial organization in MBC lesions. Future analyses will include serial biopsies over time and integration of clinicopathologic data including therapeutic response and resistance.

Citation Format: Daniel L Abravanel, Johanna Klughammer, Timothy Blosser, Yury Goltsev, Sizun Jiang, Yunjao Bai, Evan Murray, Shahar Alon, Yi Cui, Daniel R Goodwin, Anubhav Sinha, Ofir Cohen, Michal Slyper, Orr Ashenberg, Danielle Dionne, Judit Jané-Valbuena, Caroline BM Porter, Asa Segerstolpe, Julia Waldman, Sébastien Vigneau, Karla Helvie, Allison Frangieh, Laura DelloStritto, Miraj Patel, Jingyi We, Kathleen Pfaff, Nicole Cullen, Ana Lako, Madison Turner, Isaac Wakiro, Sara Napolitano, Abhay Kanodia, Rebecca Ortiz, Colin MacKichan, Stephanie Inga, Judy Chen, Aaron R Thorner, Asaf Rotem, Scott Rodig, Fei Chen, Edward S Boyden, Garry P Nolan, Xiaowei Zhuang, Orit Rozenblatt-Rosen, Bruce E Johnson, Aviv Regev, Nikhil Wagle. Spatio-molecular dissection of the breast cancer metastatic microenvironment [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD6-03.

A phase II study of efficacy, toxicity, and the potential impact of genomic alterations on response to eribulin mesylate in combination with trastuzumab and pertuzumab in women with human epidermal growth factor receptor 2 (HER2)+ metastatic breast cancer

PURPOSE

There are limited data on trastuzumab-pertuzumab (HP)-based treatments beyond the first-line, HER2+ metastatic breast cancer (MBC) setting. We conducted a phase II study of eribulin mesylate, which extends survival in MBC, with HP in patients with previously treated HER2+ MBC to evaluate efficacy, toxicity, and genomic alterations driving therapeutic response.

METHODS

After a run-in phase for eribulin dosing, two cohorts were enrolled (Cohort A-no prior pertuzumab; Cohort B-prior pertuzumab). All patients received eribulin 1.4 mg/m² on days 1, 8 with standard-dose HP on day 1 (21-day cycles). The primary endpoint was objective response rate (ORR). Genomic characterization via whole exome sequencing (WES) was completed on tumor DNA and matched germline DNA from 19 patients.

RESULTS

The six-patient run-in established a dose of eribulin 1.4 mg/m² with HP. Cohorts A and B enrolled 17 and 7 patients, respectively. Accrual stopped early due to an evolving treatment landscape and slow enrollment. The ORR was 26.3% (95% Confidence Interval [CI] 9.2-51.2%) in Cohort A and 0% in Cohort B (95% CI 0-41.0%). WES revealed more frequent alterations in TP53 (p < 0.05, q > 0.05) in patients without clinical benefit (disease control for < 24 weeks) which was not significant after multiple hypothesis correction.

CONCLUSION

Eribulin-HP had manageable toxicity and modest clinical activity in patients without prior pertuzumab exposure. This study provides a preliminary landscape of somatic alterations in this patient cohort. Our data add to the literature on how genomic alterations may predict for therapy response/resistance, as we work to individualize choices in a quickly evolving HER2+ MBC treatment landscape.

TRIAL REGISTRATION

www.clinicaltrials.gov , NCT01912963. Registered 24 July 2013.

Newly Diagnosed Patients with Inflammatory Bowel Disease: The Relationship Between Perceived Psychological Support, Health-Related Quality of Life, and Disease Activity

Background: Newly diagnosed patients with inflammatory bowel disease (IBD) encounter many physical, mental, and social uncertainties. In other chronic diseases, patients having access to disease-specific information and psychological support adhere better to medical regimens. Currently, there is a paucity of data on how newly diagnosed patients with IBD interact with their medical providers. Methods: Patients diagnosed with IBD within 5 years completed a series of questionnaires related to heath-related quality of life (HRQoL), disease activity, health education resources, medical provider relationship, and psychological support. Results: A total of 89 patients were included in the study. IBD activity correlated with disease-specific quality of life (r=-0.69, p<0.0001). Patient satisfaction with gastroenterologist interaction correlated with HRQoL (r=0.33, p=0.04) and disease activity for Crohn's disease (CD) patients (Harvey Bradshaw Index, r=-0.52, p<0.001). Eleven percent of recently diagnosed patients reported receiving educational or psychological support as part of their treatment program, whereas 42% of patients believed that they would benefit from having these types of support incorporated in their treatment protocol. Discussion: In patients with newly diagnosed CD, the patients' perceived relationship with their medical provider was closely related to both HRQoL and disease activity. More attention to education, support, and the doctor-patient relationship at diagnosis could result in better patient outcomes.

Expansion sequencing: Spatially precise in situ transcriptomics in intact biological systems

Methods for highly multiplexed RNA imaging are limited in spatial resolution and thus in their ability to localize transcripts to nanoscale and subcellular compartments. We adapt expansion microscopy, which physically expands biological specimens, for long-read untargeted and targeted in situ RNA sequencing. We applied untargeted expansion sequencing (ExSeq) to the mouse brain, which yielded the readout of thousands of genes, including splice variants. Targeted ExSeq yielded nanoscale-resolution maps of RNAs throughout dendrites and spines in the neurons of the mouse hippocampus, revealing patterns across multiple cell types, layer-specific cell types across the mouse visual cortex, and the organization and position-dependent states of tumor and immune cells in a human metastatic breast cancer biopsy. Thus, ExSeq enables highly multiplexed mapping of RNAs from nanoscale to system scale.

The Genomic Landscape of Intrinsic and Acquired Resistance to Cyclin-Dependent Kinase 4/6 Inhibitors in Patients with Hormone Receptor-Positive Metastatic Breast Cancer

Mechanisms driving resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in hormone receptor-positive (HR⁺) breast cancer have not been clearly defined. Whole-exome sequencing of 59 tumors with CDK4/6i exposure revealed multiple candidate resistance mechanisms including RB1 loss, activating alterations in AKT1, RAS, AURKA, CCNE2, ERBB2, and FGFR2, and loss of estrogen receptor expression. In vitro experiments confirmed that these alterations conferred CDK4/6i resistance. Cancer cells cultured to resistance with CDK4/6i also acquired RB1, KRAS, AURKA, or CCNE2 alterations, which conferred sensitivity to AURKA, ERK, or CHEK1 inhibition. Three of these activating alterations-in AKT1, RAS, and AURKA-have not, to our knowledge, been previously demonstrated as mechanisms of resistance to CDK4/6i in breast cancer preclinically or in patient samples. Together, these eight mechanisms were present in 66% of resistant tumors profiled and may define therapeutic opportunities in patients. SIGNIFICANCE: We identified eight distinct mechanisms of resistance to CDK4/6i present in 66% of resistant tumors profiled. Most of these have a therapeutic strategy to overcome or prevent resistance in these tumors. Taken together, these findings have critical implications related to the potential utility of precision-based approaches to overcome resistance in many patients with HR⁺ metastatic breast cancer.This article is highlighted in the In This Issue feature, p. 1079.

Reversion and non-reversion mechanisms of resistance to PARP inhibitor or platinum chemotherapy in BRCA1/2-mutant metastatic breast cancer

BACKGROUND

Little is known about mechanisms of resistance to poly(adenosine diphosphate-ribose) polymerase inhibitors (PARPi) and platinum chemotherapy in patients with metastatic breast cancer and BRCA1/2 mutations. Further investigation of resistance in clinical cohorts may point to strategies to prevent or overcome treatment failure.

PATIENTS AND METHODS

We obtained tumor biopsies from metastatic breast cancer patients with BRCA1/2 deficiency before and after acquired resistance to PARPi or platinum chemotherapy. Whole exome sequencing was carried out on each tumor, germline DNA, and circulating tumor DNA. Tumors underwent RNA sequencing, and immunohistochemical staining for RAD51 foci on tumor sections was carried out for functional assessment of intact homologous recombination (HR).

RESULTS

Pre- and post-resistance tumor samples were sequenced from eight patients (four with BRCA1 and four with BRCA2 mutation; four treated with PARPi and four with platinum). Following disease progression on DNA-damaging therapy, four patients (50%) acquired at least one somatic reversion alteration likely to result in functional BRCA1/2 protein detected by tumor or circulating tumor DNA sequencing. Two patients with germline BRCA1 deficiency acquired genomic alterations anticipated to restore HR through increased DNA end resection: loss of TP53BP1 in one patient and amplification of MRE11A in another. RAD51 foci were acquired post-resistance in all patients with genomic reversion, consistent with reconstitution of HR. All patients whose tumors demonstrated RAD51 foci post-resistance were intrinsically resistant to subsequent lines of DNA-damaging therapy.

CONCLUSIONS

Genomic reversion in BRCA1/2 was the most commonly observed mechanism of resistance, occurring in four of eight patients. Novel sequence alterations leading to increased DNA end resection were seen in two patients, and may be targetable for therapeutic benefit. The presence of RAD51 foci by immunohistochemistry was consistent with BRCA1/2 protein functional status from genomic data and predicted response to later DNA-damaging therapy, supporting RAD51 focus formation as a clinically useful biomarker.

Abstract GS6-05: A joint atlas of single-cell and bulk RNA-seq in metastatic breast cancer allows inference of oncogenic and drug-resistant transcriptional programs in malignant cells and the tumor microenvironment

While recent studies have begun to elucidate the genomics of metastatic breast cancer (MBC), the transcriptional programs (progs) that drive the drug-resistant phenotype remain poorly understood.

We prospectively collected biopsies from patients with MBC with detailed clinicopathologic features, including treatment and response characteristics. We profiled 29 biopsies by single-cell RNA seq, as well as bulk RNA-seq and whole exome sequencing on an additional 207 biopsies (analyzed snapshot, ongoing study). We analyzed these data to generate an atlas, delineating the cell-types, cell-states, and transcriptional progs.

We profiled 100,470 single cell transcriptomes and generated a comprehensive MBC atlas of the tumor and tumor microenvironment (TME). We next inferred cell types and progs associated with clinicopathologic characteristics. For example, we found significant differences in the TME of liver metastases compared to other sites, consistent with immunosuppression in the hepatic space. In particular, liver metastases were depleted in activated B-cells (lower CD69, TCL1A, VPREB3, BCNP1, and several activation-related chemokines - CXCR4/5/6/7), and their infiltrating T-cells expressed lower levels of effector and cytotoxicity markers (table=T) including CD8, CD3, beta chemokines CCL4/CCL5, IFI16, PRF1, granzymes, and GNLY, and exceptionally low expression of antigen processing genes (T).

To increase our power to make clinically relevant associations, we performed a joint analysis of the single-cell and bulk RNA-Seq data, to identify malignant cell progs related to specific oncogenic mutations, with implications for metastatic and drug-resistance phenotypes. For example, we characterized the oncogenic prog associated with activating estrogen receptor mutation (ESR1-mut). As expected, ESR1-mut prog overlaps with many known ER and luminal B markers (T). ESR1-mut prog also included specific Interferon-stimulated genes (ISGs) - IFI6, ISG15, IFIT1, STAT1, which are associated with tamoxifen resistance (T) and ECM-mediated regulation of apoptosis (T). These ISGs are predictive of poor prognosis among endocrine-treated patients (HR=1.69. p=1e-04, n=929, kmplotter). The ESR1-mut prog also included genes associated with cell-migration (SOX9, AGR2, TXNIP and several S100 genes). This suggests a role for ESR1 mutation in pathogenicity, beyond ligand-independent activation of ER signaling. A second malignant cell prog was associated with RB-null. While most of these genes were highly correlated with cell-cycle (R=0.4), some do not (HINT1, RHOC, SNRPB, ANAPC11, TMEM208, POLR2J). In spite of decoupling from proliferation, these still predict of poor outcome across breast cancer (HR=1.41, p= 6.0e-10, n=3951, kmplotter). We characterized the prog of high-grade tumors in our cohort, and found a strong association with RB-null prog (T). Similarly, we recovered additional mutation-specific oncogenic progs, including for TP53, GATA3, FOXA1, HER2, and FGFR mutants, forming a compendium of in-vivo oncogenic signatures.

To the best of our knowledge these data represent the first integration of single cell and bulk RNA-seq data in MBC, resulting in a comprehensive single-cell-resolution transcriptional atlas, and a catalog of drug-resistance oncogenic progs with implications for immunotherapy and precision-oncology.

Single-cell In-vivo programComparison Gene setAssociationP-value(top genes)(MSigDB name, PubMed ID, when applicable)Odds-ratio(Fisher''''s Exact test, two-sided)Depleted in liver T-cellsEffectors-cells markers4.077.29E-07(compared to other metastatic site - Bone, Skin, Chest-wall, Lymph node, Breast-met)(PMID: 28052254)""Antigen processing markers32.17.26E-07(PMID: 28052254)ESR1-mutVANTVEER_BREAST_CANCER_ESR1_UP5.82.30E-11(Enriched in ESR1-mutatated)(PMID: 11823860)“SMID_BREAST_CANCER_LUMINAL_B_UP5.898.10E-12“”DOANE_BREAST_CANCER_ESR1_UP6.30812.10E-09""BOWIE_RESPONSE_TO_TAMOXIFEN10.360.00036(PMID 17016442)""BECKER_TAMOXIFEN_RESISTANCE_UP7.81.20E-06(PMID 15657362)""BOWIE_RESPONSE_TO_EXTRACELLULAR_MATRIX8.240.0028(PMID 17016442)Enriched in RB-nullEnriched in High-grade (from our study)23.97.50E-05

Citation Format: Ofir Cohen, Daniel Abravanel, Michal Slyper, Johanna Klughammer, Judit Jane-Valbuena, Karla Helvie, Laura Dellostritto, Allison Frangieh, Sebastien Vigneau, Jingyi Wu, Angie Mayorga, Julia Waldman, Lan Nguyen, Danielle Dionne, Orr Ashenberg, Matan Hofree, Mike Cuoco, Christopher Rodman, Eric P Winer, Nancy Lin, Bruce Johnson, Asaf Rotem, Orit Rozenblatt-Rosen, Aviv Regev, Nikhil Wagle. A joint atlas of single-cell and bulk RNA-seq in metastatic breast cancer allows inference of oncogenic and drug-resistant transcriptional programs in malignant cells and the tumor microenvironment [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr GS6-05.

Abstract PD2-09: The genomic landscape of intrinsic and acquired resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in patients with hormone receptor-positive (HR+)/HER2- metastatic breast cancer (MBC)

Background: The CDK4/6 inhibitors have emerged as standard first- or second-line regimens in combination with an antiestrogen for patients with HR+/HER2- MBC. While these agents convey significant clinical benefit in many patients, intrinsic resistance can occur and, in patients who respond, acquired resistance is unfortunately inevitable. Despite their widespread use, we have limited insight into the molecular mechanisms governing response and resistance to these agents.

Methods: Whole exome sequencing (WES) was performed on metastatic tumor biopsies from 58 patients (pts) with HR+/HER2- MBC who received a CDK4/6 inhibitor with or without an antiestrogen at the Dana-Farber Cancer Institute, including 7 pts with pre/post-exposure biopsy pairs. Among these biopsies, 69.5% were characterized as resistant (intrinsic or acquired) and 30.5% were characterized as sensitive. To validate putative resistance mediators identified in patient samples, HR+/HER2- breast cancer cells were modified via CRISPR knockout or lentiviral overexpression. Sensitivity of these cells to antiestrogens and CDK4/6i was interrogated via cell-titer-glo assay. In parallel, HR+/HER2- breast cancer cells were cultured to resistance in the presence of an escalating dose of CDK4/6i. Derivative cell lines were subjected to western blotting in an effort to interrogate the putative resistance mediators identified in pts. Novel dependencies were identified in these derivative cell lines via treatment with targeted therapeutic agents in vitro.

Results: WES of tumors with CDK4/6i exposure revealed candidate mechanisms of resistance including biallelic RB1 disruption (n=4, 10%) and activating events in AKT1 (n=5, 12.5%), RAS (n=4, 10%), aurora kinase A (AURKA, n=11, 27.5%), and cyclin E2 (CCNE2, n=6, 15%). Convergent evolution toward biallelic RB1 disruption was identified in a single patient with one pre- and two post-exposure biopsies, while acquisition of AKT1 mutation and amplification was identified in two separate instances. Knockout of RB1 and overexpression of AKT1, KRAS G12D, AURKA, and CCNE2 provoked CDK4/6i and antiestrogen resistance in vitro. Breast cancer cells cultured to resistance in CDK4/6i demonstrated concordant acquisition of RB1 downregulation, RAS/ERK activation, AURKA overexpression, and CCNE2 overexpression. Derivative resistant cell lines with RB1 loss or AURKA gain demonstrated enhanced sensitivity to a novel AURKA inhibitor (LY3295668), while cells with RAS activation were highly sensitive to ERK inhibition (via LY3214996). CCNE2-overexpressing cells were highly sensitive to prexasertib, a CHEK1 inhibitor.

Conclusions: The genomic landscape of resistance to CDK4/6i is heterogeneous with multiple potential mediators that play well-established roles in cell division and oncogenic signal transduction. We present novel mechanisms of clinical resistance including activation of AKT1 and RAS family oncogenes as well as amplification of AURKA and CCNE2. These drivers were able to provoke resistance to CDK4/6i in vitro. Finally, in each case, a novel dependency was identified which is readily translatable into the clinic. These results underscore the potential of next-generation sequencing as a critical tool to enable identification of resistance mediators, while also suggesting that the presence of specific genomic alterations may define new therapeutic opportunities in CDK4/6i-resistant HR+ MBC.

Citation Format: Seth A. Wander, Ofir Cohen, Xueqian Gong, Gabriela N. Johnson, Jorge Buendia-Buendia, Maxwell Lloyd, Dewey Kim, Flora Luo, Pingping Mao, Karla Helvie, Kailey Kowalski, Utthara Nayar, Stephen Parsons, Ricardo Martinez, Lacey Litchfield, Xiang Ye, Chun Ping Yu, Valerie Jansen, Levi A. Garraway, Eric P. Winer, Sara M. Tolaney, Nancy U. Lin, Sean Buchanan, Nikhil Wagle. The genomic landscape of intrinsic and acquired resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in patients with hormone receptor-positive (HR+)/HER2- metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD2-09.

Reversion and non-reversion mechanisms of resistance (MoR) to PARP inhibitor (PARPi) or platinum chemotherapy (chemotx) in patients (pts) with BRCA1/2-mutant metastatic breast cancer (MBC)

1085

Background: Little is known about MoR to PARPi and platinum chemotx in MBC pts with BRCA1/2 mutations. Biomarkers predictive of response/resistance have not been identified, but could have clinical utility. Methods: We obtained 8 BRCA-mutant metastatic tumor biopsies from MBC pts with acquired resistance to DNA-damaging tx (PARPi/platinum) on a prospective tissue collection protocol. In 7/8 patients, we also obtained pre-tx biopsies. Whole exome sequencing (WES) was performed on each tumor and on germline DNA from blood. We performed immunohistochemical (IHC) staining for RAD51 foci for functional assessment of intact homologous recombination (HR). Results: 4/7 pts with complete WES analysis acquired a somatic reversion mutation likely to result in functional BRCA1/2 protein in the post-tx tumor specimen after platinum (2 pts) or PARPi (2 pts; Table). 4/7 pts had plausible non-reversion MoR identified by WES, including alterations in genes involved in replication fork protection and DNA end resection. As expected, in all pts with genomic reversion, RAD51 foci were acquired in the post-resistance tumor, consistent with reconstitution of HR. In 2 pts without reversion, presence of RAD51 foci post-resistance was mixed. Reversion mutations occurred both with and without other alterations that could possibly lead to fork protection, suggesting > 1 MoR could occur in the same tumor. 3 pts whose tumors demonstrated RAD51 foci post-resistance were later re-exposed to DNA-damaging tx, to which all had intrinsic resistance. Conclusions: BRCA1/2 reversion was identified as a MoR in the majority of pts. WES identified potential novel MoR in fork protection and end resection genes. The presence of RAD51 foci by IHC was consistent with BRCA protein functional status from genomic data and predicted response to later DNA-damaging tx, suggesting RAD51 IHC may be a clinically useful biomarker. [Table: see text]

Abstract PD9-02: Evolutionary analysis of 462 serial metastatic biopsies from 208 patients with estrogen receptor-positive (ER+) metastatic breast cancer (MBC) using whole exome sequencing (WES)

Background: While great strides have been made in the treatment of ER+ MBC, therapeutic resistance is nearly universal. The genomic evolution of ER+ breast cancer in the metastatic setting under the selective pressure of multiple lines of therapies is not well understood. To address this, we analyzed the clonal dynamics of serial metastatic samples (mets) to evaluate how tumors evolve and to identify acquired resistance mechanisms.

Methods: We performed WES on 462 clinically annotated samples from 208 patients (pts) with ER+ MBC, including 67 primary tumor biopsies, 229 metastatic biopsies and 160 blood samples (cfDNA). Pts with multiple mets included cases with temporally concordant metastatic tumor and blood samples (48 pts) and cases with serial mets obtained over the course of treatment in the metastatic setting (69 pts). Treatments given between the serial mets included CDK4/6 inhibitors (23 pts), and selective estrogen receptor degraders (19 pts), among others.

Results: In the temporally-concordant mets, we found that cfDNA mutations (muts) largely overlap with muts found in tumor biopsies, capturing &gt;85% of clonal tumor muts. However, we observed a higher level of heterogeneity in cfDNA compared to biopsies (p.value&lt; 1.05e-19, Welch test) and a subset of high-confidence muts that were only detected in cfDNA, including in clinically important genes such as ESR1, PIK3CA, KRAS, and ERBB2. Analysis of serial mets was used to elucidate the evolutionary dynamics within the metastatic setting under the selective pressure of treatment. The median duration between mets was 112 days and the median number of inter-biopsy unique treatments was two. Most tumors continued to evolve within the metastatic setting, with 50 out of 69 pts (72%) acquiring a meaningful sub-clone (50% increase in relative cancer cell fraction) and 31 out of 69 (45%) acquiring muts in known cancer genes, including a subset acquiring a plausible resistance alteration such as alterations that dysregulate ER (5 out of 69 pts, 7%; ESR1 mut, FOXA1 amplification (amp), NCOR1 bi-allelic deletion (del)), ERBB (4%; ERBB2 amp, ERBB3 mut), RAS (4%; KRAS mut, NRAS amp, NF1 del), FGF/FGFR (12%; FGFR2 mut, FGFR1/2 amp, FGF3 amp), and cell cycle (13%; RB1 del, CDK4 amp, AURKA amp, CDKN2A del). Finally, in pts who had multiple mets, we observed several cases of evolutionary convergence toward equivalent resistance mechanisms including convergent RB1 loss as a mechanism of resistance to a CDK4/6 inhibitor and convergent BRCA2 reversion following resistance to a PARP inhibitor.

Conclusions: This study demonstrates that ER+ MBC continues to evolve under the selective pressure of treatments in the metastatic setting. These findings elucidate the challenge of studying high complexity and heavily treated tumors, while also highlighting some commonalities in the evolutionary trajectories selected by these treatments. The multiplicity of clinically relevant genomic alterations acquired in these advanced stages highlights the need for serial biopsies and the potential to inform post-progression therapeutic choices through targeting the acquired dependencies in post-progression tumors.

Citation Format: Cohen O, Buendia-Buendia J, Wander S, Nayar U, Mao P, Waks A, Kim D, Freeman S, Adalsteinsson V, Helvie K, Livitz D, Rosebrock D, Leshchiner I, Dellostritto L, Garrido-Castro A, Jain E, Periyasamy S, Mackichan C, Lloyd M, Marini L, Krop I, Garraway L, Getz G, Winer E, Lin N, Wagle N. Evolutionary analysis of 462 serial metastatic biopsies from 208 patients with estrogen receptor-positive (ER+) metastatic breast cancer (MBC) using whole exome sequencing (WES) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD9-02.

Acquired HER2 mutations in ER+ metastatic breast cancer confer resistance to estrogen receptor-directed therapies

Seventy percent of breast cancers express the estrogen receptor (ER), and agents that target the ER are the mainstay of treatment. However, virtually all people with ER⁺ breast cancer develop resistance to ER-directed agents in the metastatic setting. Beyond mutations in the ER itself, which occur in 25-30% of people treated with aromatase inhibitors^1-4, knowledge about clinical resistance mechanisms remains incomplete. We identified activating HER2 mutations in metastatic biopsies from eight patients with ER⁺ metastatic breast cancer who had developed resistance to aromatase inhibitors, tamoxifen or fulvestrant. Examination of treatment-naive primary tumors in five patients showed no evidence of pre-existing mutations in four of five patients, suggesting that these mutations were acquired under the selective pressure of ER-directed therapy. The HER2 mutations and ER mutations were mutually exclusive, suggesting a distinct mechanism of acquired resistance to ER-directed therapies. In vitro analysis confirmed that the HER2 mutations conferred estrogen independence as well as-in contrast to ER mutations-resistance to tamoxifen, fulvestrant and the CDK4 and CDK6 inhibitor palbociclib. Resistance was overcome by combining ER-directed therapy with the irreversible HER2 kinase inhibitor neratinib.

Real-time Genomic Characterization of Advanced Pancreatic Cancer to Enable Precision Medicine

Clinically relevant subtypes exist for pancreatic ductal adenocarcinoma (PDAC), but molecular characterization is not yet standard in clinical care. We implemented a biopsy protocol to perform time-sensitive whole-exome sequencing and RNA sequencing for patients with advanced PDAC. Therapeutically relevant genomic alterations were identified in 48% (34/71) and pathogenic/likely pathogenic germline alterations in 18% (13/71) of patients. Overall, 30% (21/71) of enrolled patients experienced a change in clinical management as a result of genomic data. Twenty-six patients had germline and/or somatic alterations in DNA-damage repair genes, and 5 additional patients had mutational signatures of homologous recombination deficiency but no identified causal genomic alteration. Two patients had oncogenic in-frame BRAF deletions, and we report the first clinical evidence that this alteration confers sensitivity to MAPK pathway inhibition. Moreover, we identified tumor/stroma gene expression signatures with clinical relevance. Collectively, these data demonstrate the feasibility and value of real-time genomic characterization of advanced PDAC.Significance: Molecular analyses of metastatic PDAC tumors are challenging due to the heterogeneous cellular composition of biopsy specimens and rapid progression of the disease. Using an integrated multidisciplinary biopsy program, we demonstrate that real-time genomic characterization of advanced PDAC can identify clinically relevant alterations that inform management of this difficult disease. Cancer Discov; 8(9); 1096-111. ©2018 AACR.See related commentary by Collisson, p. 1062This article is highlighted in the In This Issue feature, p. 1047.

Abstract S1-01: Whole exome and transcriptome sequencing of resistant ER+ metastatic breast cancer

Background: While great strides have been made in the treatment of estrogen receptor-positive (ER+) metastatic breast cancer (MBC), therapeutic resistance invariably occurs. A better understanding of the underlying resistance mechanisms is critical to enable durable control of this disease.

Methods: We performed whole exome sequencing (WES) and transcriptome sequencing (RNA-seq) on metastatic tumor biopsies from 88 patients with ER+ MBC who had developed resistance to one or more ER-directed therapies. For 27 of these patients, we sequenced the treatment-naïve primary tumors for comparison to the resistant specimens. Tumors were analyzed for point mutations, insertions/deletions, copy number alterations, translocations, and gene expression. Detailed clinicopathologic data was collected for each patient and linked to the genomic information.

Results: WES of all metastatic samples demonstrated several recurrently altered genes whose incidence differed significantly from primary, treatment-naïve ER+ breast cancers sequenced in the TCGA study (TCGA). These include ESR1 mutations (n=17, 19.3%; 32.86 fold enrichment, q.value&lt;7.5e-12), CCND1 amplification (n=52, 59.1%; 2.3 fold enrichment, q.value&lt;0.0073), and MAP2K4 biallelic inactivation (n=14, 15.9%; 3.04 fold enrichment, q.value&lt; 0.054).

Comparing to matched primary samples from the same patient, many alterations were found to be acquired in several cases, including for ESR1, ERBB2, PIK3CA, PTEN, RB1, AKT1, and others. Initial analysis of RNA-seq data from metastatic samples (n=59) allowed classification of individual resistance mechanisms into broader resistance modes based on the observed transcriptional state.

Conclusions: We present a genomic landscape of resistant ER+ MBC using WES and RNA-seq. Multiple genes were recurrently altered in these tumors at significantly higher rates than in ER+ primary breast cancer. When compared with matched primary tumors from the same patient, alterations in these and other genes were often found to be acquired after treatment, suggesting a role in resistance to ER-directed therapies and/or metastasis. Potential resistance mechanisms appear to fall into several categories; integrating RNA-seq data may enhance the ability to identify these categories even when genomic alterations are not identified. Multiple clinically relevant genomic and molecular alterations are identified in metastatic biopsies– with implications for choice of next therapy, clinical trial eligibility, and novel drug targets.

Citation Format: Cohen O, Kim D, Oh C, Waks A, Oliver N, Helvie K, Marini L, Rotem A, Lloyd M, Stover D, Adalsteinsson V, Freeman S, Ha G, Cibulskis C, Anderka K, Tamayo P, Johannessen C, Krop I, Garraway L, Winer E, Lin N, Wagle N. Whole exome and transcriptome sequencing of resistant ER+ metastatic breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S1-01.

Effects of inflammatory bowel disease on students' adjustment to college

BACKGROUND & AIMS

Successful adjustment to college is required for academic success. We investigated whether inflammatory bowel disease (IBD) activity affects this adjustment process.

METHODS

We created an online survey that included a Student Adaptation to College Questionnaire (SACQ), a general quality of life survey (SF-12), a disease-specific short IBD quality of life survey (SIBDQ), and disease activity indices. Undergraduate students across the United States were recruited via social media.

RESULTS

Surveys were completed by 65 students with Crohn's disease (CD), 28 with ulcerative colitis, and 214 healthy students (controls). Disease-specific quality of life (SIBDQ results) correlated with IBD disease activity (rho = -0.79; P < .0001). High college adjustment scores (SACQ results) were associated with high SIBDQ scores. Students with IBD had lower mean SACQ scores than controls (307 vs 290; P < .0001). There was a modest inverse correlation between CD activity and SACQ (rho = -0.24; P < .04). Disease activity in students with CD was associated strongly with their self-reported ability to keep up with academic work (P < .0089) and confidence in their ability to meet future academic challenges (P < .0015). Students with active IBD reported feeling as if they were not academically successful (P < .018), and students with ulcerative colitis reported irregular class attendance (P < .043).

CONCLUSIONS

Students with IBD do not adjust to college as well as healthy students. Disease activity affects their adjustment and attitudes about academics-especially among students with CD. Successful adjustment is important for academic success, affecting graduation rates and future economic success. Strategies to increase disease control and provide social and emotional support during college could improve adjustment to college and academic performance, and increase patients' potential.