Tamoxifen Response at Single-Cell Resolution in Estrogen Receptor-Positive Primary Human Breast Tumors

PURPOSE

In estrogen receptor-positive (ER+)/HER2- breast cancer, multiple measures of intratumor heterogeneity are associated with a worse response to endocrine therapy. We sought to develop a novel experimental model to measure heterogeneity in response to tamoxifen treatment in primary breast tumors.

EXPERIMENTAL DESIGN

To investigate heterogeneity in response to treatment, we developed an operating room-to-laboratory pipeline for the collection of live normal breast specimens and human tumors immediately after surgical resection for processing into single-cell workflows for experimentation and genomic analyses. Live primary cell suspensions were treated ex vivo with tamoxifen (10 μmol/L) or control media for 12 hours, and single-cell RNA libraries were generated using the 10X Genomics droplet-based kit.

RESULTS

In total, we obtained and processed normal breast tissue from two women undergoing reduction mammoplasty and tumor tissue from 10 women with ER+/HER2- invasive breast carcinoma. We demonstrate differences in tamoxifen response by cell type and identify distinctly responsive and resistant subpopulations within the malignant cell compartment of human tumors. Tamoxifen resistance signatures from resistant subpopulations predict poor outcomes in two large cohorts of ER+ breast cancer patients and are enriched in endocrine therapy-resistant tumors.

CONCLUSIONS

This novel ex vivo model system now provides the foundation to define responsive and resistant subpopulations within heterogeneous human tumors, which can be used to develop precise single cell-based predictors of response to therapy and to identify genes and pathways driving therapeutic resistance.

Aminobisphosphonates reactivate the latent reservoir in people living with HIV-1

Antiretroviral therapy (ART) is not curative due to the existence of cellular reservoirs of latent HIV-1 that persist during therapy. Current research efforts to cure HIV-1 infection include "shock and kill" strategies to disrupt latency using small molecules or latency-reversing agents (LRAs) to induce expression of HIV-1 enabling cytotoxic immune cells to eliminate infected cells. The modest success of current LRAs urges the field to identify novel drugs with increased clinical efficacy. Aminobisphosphonates (N-BPs) that include pamidronate, zoledronate, or alendronate, are the first-line treatment of bone-related diseases including osteoporosis and bone malignancies. Here, we show the use of N-BPs as a novel class of LRA: we found in ex vivo assays using primary cells from ART-suppressed people living with HIV-1 that N-BPs induce HIV-1 from latency to levels that are comparable to the T cell activator phytohemagglutinin (PHA). RNA sequencing and mechanistic data suggested that reactivation may occur through activation of the activator protein 1 signaling pathway. Stored samples from a prior clinical trial aimed at analyzing the effect of alendronate on bone mineral density, provided further evidence of alendronate-mediated latency reversal and activation of immune effector cells. Decay of the reservoir measured by IPDA was however not detected. Our results demonstrate the novel use of N-BPs to reverse HIV-1 latency while inducing immune effector functions. This preliminary evidence merits further investigation in a controlled clinical setting possibly in combination with therapeutic vaccination.

Tamoxifen Response at Single Cell Resolution in Estrogen Receptor-Positive Primary Human Breast Tumors

In ER+/HER2- breast cancer, multiple measures of intra-tumor heterogeneity are associated with worse response to endocrine therapy. To investigate heterogeneity in response to treatment, we developed an operating room-to-laboratory pipeline for the collection of live human tumors and normal breast specimens immediately after surgical resection for processing into single-cell workflows for experimentation and genomic analyses. We demonstrate differences in tamoxifen response by cell type and identify distinctly responsive and resistant subpopulations within the malignant cell compartment of human tumors. Tamoxifen resistance signatures from 3 distinct resistant subpopulations are prognostic in large cohorts of ER+ breast cancer patients and enriched in endocrine therapy resistant tumors. This novel ex vivo model system now provides a foundation to define responsive and resistant sub-populations within heterogeneous tumors, to develop precise single cell-based predictors of response to therapy, and to identify genes and pathways driving resistance to therapy.

Abstract 5754: Determining the regulatory logic of breast cancer cells using single-cell multi-omics

Cancer cells rewire regulatory elements scattered throughout the genome (such as enhancers) to drive aberrant gene expression. Thus, deconvoluting the regulatory mechanisms that contribute to oncogenic gene expression in cancer cells is key to understanding tumor biology. To this end, we have charted the transcriptional and epigenetic landscape of breast cancer at single-cell resolution to quantitatively link variation in chromatin accessibility to gene expression across malignant and non-malignant cell types. Our comprehensive dataset profiles the chromatin landscape (scATAC-seq) in concert with the transcriptional profiles (scRNA-seq) of 4 breast cancer cell lines, 12 primary breast tumors, and 4 normal mammary reduction tissue specimens collected and processed immediately after surgical resection. This dataset, encompassing over 250,000 individual cells, allowed us to define the regulatory logic of cancer cells by 1) revealing how the epigenome underlies cellular heterogeneity of these tumors in comparison to normal mammary tissue, 2) defining how malignant cells hijack enhancer elements to drive key transcriptional programs in a subtype-specific manner, and 3) annotating which cancer-specific enhancer-to-gene connections portend a worse outcome in patients. Notably, we discovered that cancer cells acquire de novo non-coding enhancer elements to modulate hallmark cancer pathways that were previously hidden using bulk genomics approaches. This highlights the potential for cancer-specific enhancers to serve as markers with diagnostic and prognostic potential, or even serve as tractable targets for therapeutic intervention. Together these data enable the annotation of the cellular composition, transcriptional, and epigenetic landscape of breast tumors to help pinpoint clinically relevant mechanisms of tumorigenesis.

Citation Format: Matthew J. Regner, Aatish Thennavan, Susana Garcia-Recio, Kamila Wisniewska, Philip M. Spanheimer, Joel S. Parker, Charles M. Perou, Hector L. Franco. Determining the regulatory logic of breast cancer cells using single-cell multi-omics. [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 5754.

Abstract PD4-08: PD4-08 A Novel Single Cell Model of Tamoxifen Response in Primary Human Breast Tumors

A Novel Single Cell Model of Tamoxifen Response in Primary Human Breast Tumors Austin Whitman, Hyunsoo Kim, Kamila Wisniewska, Rasha Kakati, Susana Garcia Recio, Hector Franco, Charles Perou, Philip Spanheimer Background: Resistance to endocrine therapy is a primary cause of treatment failure and death in patients with estrogen receptor (ER)-positive breast cancer. Intratumor heterogeneity is associated with resistance to therapy across tumors, and specifically in ER+/HER2- breast cancer, heterogeneity in ER and PR expression is associated with a worse response to endocrine therapy. We hypothesize that subpopulations within and across ER+/HER2- human breast tumors have distinct responses to tamoxifen and that discerning heterogeneity in response will improve understanding of inherent and emerging resistance to endocrine therapy. Methods: We developed an operating room-to-laboratory pipeline immediately after surgical resection for studies using alive tissue. Tissue samples were obtained and single cell suspensions created using physical and enzymatic dissociation. Cells were treated with tamoxifen (10 M) or control media for 12 hours in suspension and single cell RNA libraries generated using the 10X Genomics droplet-based kit and sequenced using the Illumina NextSeq2000. Results: We obtained normal breast tissue from 2 women undergoing reduction mammoplasty and tumor tissue from 10 women with ER+/HER2- invasive breast carcinoma. In tamoxifen treated and control matched pairs, a total of 22,195 cells from normal breast and 94,558 cells from tumor samples were sequenced. Computational analysis using consensus clustering was performed and cell types assigned using canonical correlation. Both tumor and normal samples identified clustering by cell type and not by patient revealing significant variability in cell type abundance between samples. In the normal breast samples, we performed differentially expressed genes (DEG) analysis comparing tamoxifen treatment to control for each cell type (Immune cells, fibroblasts, basal epithelial cells, luminal progenitor cells, and mature luminal cells) and enrichment analysis of up- and down-regulated genes performed. Strong depletion of estrogen induced genes was observed in tamoxifen-treated normal luminal progenitor and mature luminal cells, but not in basal epithelial cells or fibroblasts, demonstrating distinct, subpopulation-specific response to tamoxifen. In the 10 tumor matched pairs, 4 had a high epithelial proportion and tumor cells identified using inferred copy number variation. Tumor cells in 3 of these 4 samples showed significant down regulation of estrogen response genes with tamoxifen treatment. Using scBCSubtype to assign PAM50 subtype to individual tumor cells, the 3 responsive tumors were comprised primarily of LumA cells while the unresponsive tumor was predominantly LumB. Finally, we developed a novel score to quantify responsiveness at the single cell level based on downregulation of estrogen response genes with tamoxifen treatment relative to matched cluster-specific untreated expression. This analysis demonstrated heterogeneity in response to tamoxifen in tumor cells and identified distinct subpopulations of responsive and unresponsive tumor cells to tamoxifen treatment. Conclusion: We developed a novel ex vivo model to determine heterogeneity in therapeutic response to tamoxifen in normal human breast tissue and primary human breast tumors. We demonstrate differences in tamoxifen response by cell type and identify distinctly responsive and resistant subpopulations within human tumors. This provides a foundation to define features of responsive and resistant populations on the individual cell and specimen basis, and should allow us to develop precise, single cell-based predictors of response to endocrine therapy, and to identify genes and pathways driving resistance to therapy.

Citation Format: Hyunsoo Kim, Austin Whitman, Kamila Wisniewska, Susana Garcia-Recio, Rasha Kakati, Hector L. Franco, Charles M. Perou, Philip Spanheimer. PD4-08 A Novel Single Cell Model of Tamoxifen Response in Primary Human Breast Tumors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD4-08.

Abstract P5-14-02: Identifying oncogenic enhancer elements in TNBC of the Basal-like subtype using single-cell ATAC-seq and RNA-seq

Identification of the cis-regulatory elements controlling oncogenic transcriptional programs is critical to understanding tumor biology. To find cis-regulatory elements (i.e. gene enhancers) of oncogenic dependencies in Triple-Negative Breast Cancers (TNBC) of the Basal-like gene expression subtype, we generated matched single-cell transcriptome (scRNA-seq) and chromatin accessibility (scATAC-seq) profiles for two human Basal-like tumors and four normal mammary reduction samples. This unique dataset enabled us to correlate variations in chromatin structure with variations in gene expression revealing putative enhancers that are specifically active within cancer cells, but not within normal mammary ductal epithelial cells. We then leveraged the Cancer Dependency Map (DepMap) portal at the BROAD Institute to infer gene expression dependencies in breast cancer cell lines of the Basal-like molecular subtype. Putative cancer-specific enhancers were prioritized based on the transcriptional dependency of their target gene(s) in Basal-like cell lines as reported by the DepMap portal. Based on our preliminary analyses, we report several cancer-specific enhancers that drive the expression of important transcription factors such as EN1 and SOX4. These transcription factors are known to have profound effects on tumor biology, especially considering that high expression of EN1 is associated with brain metastasis and SOX4 is known to regulate immune evasion and PI3K/Akt signaling. Moreover, both of these transcription factors portend a worse outcome in TNBC patients. Thus, our analysis suggests that high levels of expression of these transcription factors is sustained specifically within the malignant cell types of these tumors, by the activity of these cancer-specific enhancers that are not typically active in normal epithelial cells. We are now performing CRISPR dCas9-KRAB experiments to epigenetically silence these cancer-specific enhancers and measure the consequences on expression of their predicted target genes. Additionally, we are investigating the trans-acting transcription factors that may physically bind to these enhancers to further regulate oncogenic transcription. By defining the regulatory logic of cancer cells at single-cell resolution, our work highlights the importance of cancer-specific and clinically relevant oncogenic regulatory elements in TNBC of the Basal-like subtype.

Citation Format: Matthew J. Regner, Aatish Thennavan, Kamila Wisniewska, Susana Garcia-Recio, Raul Mendez-Giraldez, Philip Spanheimer, Charles M. Perou, Hector L. Franco. Identifying oncogenic enhancer elements in TNBC of the Basal-like subtype using single-cell ATAC-seq and RNA-seq [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-14-02.

Aminobisphosphonates reactivate the latent reservoir in people living with HIV-1

Antiretroviral therapy (ART) is not curative due to the existence of cellular reservoirs of latent HIV-1 that persist during therapy. Current research efforts to cure HIV-1 infection include "shock and kill" strategies to disrupt latency using small molecules or latency-reversing agents (LRAs) to induce expression of HIV-1 enabling cytotoxic immune cells to eliminate infected cells. The modest success of current LRAs urges the field to identify novel drugs with increased clinical efficacy. Aminobisphosphonates (N-BPs) that include pamidronate, zoledronate, or alendronate, are the first-line treatment of bone-related diseases including osteoporosis and bone malignancies. Here, we show the use of N-BPs as a novel class of LRA: we found in ex vivo assays using primary cells from ART-suppressed people living with HIV-1 that N-BPs induce HIV-1 from latency to levels that are comparable to the T cell activator phytohemagglutinin (PHA). RNA sequencing and mechanistic data suggested that reactivation may occur through activation of the activator protein 1 signaling pathway. Stored samples from a prior clinical trial aimed at analyzing the effect of alendronate on bone mineral density, provided further evidence of alendronate-mediated latency reversal and activation of immune effector cells. Decay of the reservoir measured by IPDA was however not detected. Our results demonstrate the novel use of N-BPs to reverse HIV-1 latency while inducing immune effector functions. This preliminary evidence merits further investigation in a controlled clinical setting possibly in combination with therapeutic vaccination.

Multiomics in primary and metastatic breast tumors from the AURORA US network finds microenvironment and epigenetic drivers of metastasis

The AURORA US Metastasis Project was established with the goal to identify molecular features associated with metastasis. We assayed 55 females with metastatic breast cancer (51 primary cancers and 102 metastases) by RNA sequencing, tumor/germline DNA exome and low-pass whole-genome sequencing and global DNA methylation microarrays. Expression subtype changes were observed in ~30% of samples and were coincident with DNA clonality shifts, especially involving HER2. Downregulation of estrogen receptor (ER)-mediated cell-cell adhesion genes through DNA methylation mechanisms was observed in metastases. Microenvironment differences varied according to tumor subtype; the ER+/luminal subtype had lower fibroblast and endothelial content, while triple-negative breast cancer/basal metastases showed a decrease in B and T cells. In 17% of metastases, DNA hypermethylation and/or focal deletions were identified near HLA-A and were associated with reduced expression and lower immune cell infiltrates, especially in brain and liver metastases. These findings could have implications for treating individuals with metastatic breast cancer with immune- and HER2-targeting therapies.

Molecular signatures of in situ to invasive progression for basal-like breast cancers: An integrated mouse model and human DCIS study

Ductal carcinoma in situ (DCIS) of the breast is a non-obligate precursor of Invasive Ductal Carcinoma (IDC) and thus the identification of features that may predict DCIS progression would be of potential clinical value. Experimental mouse models can be used to address this challenge by studying DCIS-to-IDC biology. Here we utilize single cell RNA sequencing (scRNAseq) on the C3Tag genetically engineered mouse model that forms DCIS-like precursor lesions and for which many lesions progress into end-stage basal-like molecular subtype IDC. We also perform bulk RNAseq analysis on 10 human synchronous DCIS-IDC pairs comprised of estrogen receptor (ER) positive and ER-negative subsets and utilize 2 additional public human DCIS data sets for comparison to our mouse model. By identifying malignant cells using inferred DNA copy number changes from the murine C3Tag scRNAseq data, we show the existence of cancer cells within the C3Tag pre-DCIS, DCIS, and IDC-like tumor specimens. These cancer cells were further classified into proliferative, hypoxic, and inflammatory subpopulations, which change in frequency in DCIS versus IDC. The C3Tag tumor progression model was also associated with increase in Cancer-Associated Fibroblasts and decrease in activated T cells in IDC. Importantly, we translate the C3Tag murine genomic findings into human DCIS where we find common features only with human basal-like DCIS, suggesting there are intrinsic subtype unique DCIS features. This study identifies several tumor and microenvironmental features associated with DCIS progression and may also provide genomic signatures that can identify progression-prone DCIS within the context of human basal-like breast cancers.

A multi-omic single-cell landscape of human gynecologic malignancies

Deconvolution of regulatory mechanisms that drive transcriptional programs in cancer cells is key to understanding tumor biology. Herein, we present matched transcriptome (scRNA-seq) and chromatin accessibility (scATAC-seq) profiles at single-cell resolution from human ovarian and endometrial tumors processed immediately following surgical resection. This dataset reveals the complex cellular heterogeneity of these tumors and enabled us to quantitatively link variation in chromatin accessibility to gene expression. We show that malignant cells acquire previously unannotated regulatory elements to drive hallmark cancer pathways. Moreover, malignant cells from within the same patients show substantial variation in chromatin accessibility linked to transcriptional output, highlighting the importance of intratumoral heterogeneity. Finally, we infer the malignant cell type-specific activity of transcription factors. By defining the regulatory logic of cancer cells, this work reveals an important reliance on oncogenic regulatory elements and highlights the ability of matched scRNA-seq/scATAC-seq to uncover clinically relevant mechanisms of tumorigenesis in gynecologic cancers.

FGFR4 regulates tumor subtype differentiation in luminal breast cancer and metastatic disease

Mechanisms driving tumor progression from less aggressive subtypes to more aggressive states represent key targets for therapy. We identified a subset of luminal A primary breast tumors that give rise to HER2-enriched (HER2E) subtype metastases, but remain clinically HER2 negative (cHER2-). By testing the unique genetic and transcriptomic features of these cases, we developed the hypothesis that FGFR4 likely participates in this subtype switching. To evaluate this, we developed 2 FGFR4 genomic signatures using a patient-derived xenograft (PDX) model treated with an FGFR4 inhibitor, which inhibited PDX growth in vivo. Bulk tumor gene expression analysis and single-cell RNA sequencing demonstrated that the inhibition of FGFR4 signaling caused molecular switching. In the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) breast cancer cohort, FGFR4-induced and FGFR4-repressed signatures each predicted overall survival. Additionally, the FGFR4-induced signature was an independent prognostic factor beyond subtype and stage. Supervised analysis of 77 primary tumors with paired metastases revealed that the FGFR4-induced signature was significantly higher in luminal/ER+ tumor metastases compared with their primaries. Finally, multivariate analysis demonstrated that the FGFR4-induced signature also predicted site-specific metastasis for lung, liver, and brain, but not for bone or lymph nodes. These data identify a link between FGFR4-regulated genes and metastasis, suggesting treatment options for FGFR4-positive patients, whose high expression is not caused by mutation or amplification.

B Cells and T Follicular Helper Cells Mediate Response to Checkpoint Inhibitors in High Mutation Burden Mouse Models of Breast Cancer

This study identifies mechanisms mediating responses to immune checkpoint inhibitors using mouse models of triple-negative breast cancer. By creating new mammary tumor models, we find that tumor mutation burden and specific immune cells are associated with response. Further, we developed a rich resource of single-cell RNA-seq and bulk mRNA-seq data of immunotherapy-treated and non-treated tumors from sensitive and resistant murine models. Using this, we uncover that immune checkpoint therapy induces T follicular helper cell activation of B cells to facilitate the anti-tumor response in these models. We also show that B cell activation of T cells and the generation of antibody are key to immunotherapy response and propose a new biomarker for immune checkpoint therapy. In total, this work presents resources of new preclinical models of breast cancer with large mRNA-seq and single-cell RNA-seq datasets annotated for sensitivity to therapy and uncovers new components of response to immune checkpoint inhibitors.

Bimodal age distribution at diagnosis in breast cancer persists across molecular and genomic classifications

PURPOSE

Female breast cancer demonstrates bimodal age frequency distribution patterns at diagnosis, interpretable as two main etiologic subtypes or groupings of tumors with shared risk factors. While RNA-based methods including PAM50 have identified well-established clinical subtypes, age distribution patterns at diagnosis as a proxy for etiologic subtype are not established for molecular and genomic tumor classifications.

METHODS

We evaluated smoothed age frequency distributions at diagnosis for Carolina Breast Cancer Study cases within immunohistochemistry-based and RNA-based expression categories. Akaike information criterion (AIC) values compared the fit of single density versus two-component mixture models. Two-component mixture models estimated the proportion of early-onset and late-onset categories by immunohistochemistry-based ER (n = 2860), and by RNA-based ESR1 and PAM50 subtype (n = 1965). PAM50 findings were validated using pooled publicly available data (n = 8103).

RESULTS

Breast cancers were best characterized by bimodal age distribution at diagnosis with incidence peaks near 45 and 65 years, regardless of molecular characteristics. However, proportional composition of early-onset and late-onset age distributions varied by molecular and genomic characteristics. Higher ER-protein and ESR1-RNA categories showed a greater proportion of late age-at-onset. Similarly, PAM50 subtypes showed a shifting age-at-onset distribution, with most pronounced early-onset and late-onset peaks found in Basal-like and Luminal A, respectively.

CONCLUSIONS

Bimodal age distribution at diagnosis was detected in the Carolina Breast Cancer Study, similar to national cancer registry data. Our data support two fundamental age-defined etiologic breast cancer subtypes that persist across molecular and genomic characteristics. Better criteria to distinguish etiologic subtypes could improve understanding of breast cancer etiology and contribute to prevention efforts.

Alterations in Wnt- and/or STAT3 signaling pathways and the immune microenvironment during metastatic progression

Metastatic breast cancer is an extremely complex disease with limited treatment options due to the lack of information about the major characteristics of metastatic disease. There is an urgent need, therefore, to understand the changes in cellular complexity and dynamics that occur during metastatic progression. In the current study, we analyzed the cellular and molecular differences between primary tumors and paired lung metastases using a syngeneic p53-null mammary tumor model of basal-like breast cancer. Distinct subpopulations driven by the Wnt- and/or STAT3 signaling pathways were detected in vivo using a lentiviral Wnt- and STAT3 signaling reporter system. A significant increase in the overlapping populations driven by both the Wnt- and STAT3 signaling pathways was observed in the lung metastases as compared to the primary tumors. Furthermore, the overlapping populations showed a higher metastatic potential relative to the other populations and pharmacological inhibition of both signaling pathways was shown to markedly reduce the metastatic lesions in established lung metastases. An analysis of the unique molecular features of the lung metastases revealed a significant association with immune response signatures. Specifically, Foxp3 gene expression was markedly increased and elevated levels of Foxp3 + Treg cells were detected in close proximity to lung metastases. Collectively, these studies illustrate the importance of analyzing intratumoral heterogeneity, changes in population dynamics, and the immune microenvironment during metastatic progression.

The Transmodulation of HER2 and EGFR by Substance P in Breast Cancer Cells Requires c-Src and Metalloproteinase Activation

Background

Substance P (SP) is a pleiotropic cytokine/neuropeptide that enhances breast cancer (BC) aggressiveness by transactivating tyrosine kinase receptors like EGFR and HER2. We previously showed that SP and its cognate receptor NK-1 (SP/NK1-R) signaling modulates the basal phosphorylation of HER2 and EGFR in BC, increasing aggressiveness and drug resistance. In order to elucidate the mechanisms responsible for NK-1R-mediated HER2 and EGFR transactivation, we investigated the involvement of c-Src (a ligand-independent mediator) and of metalloproteinases (ligand-dependent mediators) in HER2/EGFR activation.

Results and Discussion

Overexpression of NK-1R in MDA-MB-231 and its chemical inhibition in SK-BR-3, BT-474 and MDA-MB-468 BC cells significantly modulated c-Src activation, suggesting that this protein is a mediator of NK-1R signaling. In addition, the c-Src inhibitor 4-(4’-phenoxyanilino)-6,7-dimethoxyquinazoline prevented SP-induced activation of HER2. On the other hand, SP-dependent phosphorylation of HER2 and EGFR decreased substantially in the presence of the MMP inhibitor 1–10, phenanthroline monohydrate, and the dual inhibition of both c-Src and MMP almost abolished the activation of HER2 and EGFR. Moreover, the use of these inhibitors demonstrated that this Src and MMP-dependent signaling is important to the cell viability and migration capacity of HER2+ and EGFR+ cell lines.

Conclusion

Our results indicate that the transactivation of HER2 and EGFR by the pro-inflammatory cytokine/neuropeptide SP in BC cells is a c-Src and MMP-dependent process.

The neurokinin-1 receptor antagonist aprepitant is a promising candidate for the treatment of breast cancer

The substance P (SP)/neurokinin (NK)-1 receptor system plays an important role in the development of cancer. No in-depth studies of the involvement of this system in breast cancer (BC) have been carried out, and the action exerted by the drug aprepitant on BC cells is currently unknown. We show the involvement of this system in human BC cell lines: i) these cells express mRNA for the NK-1 receptor; ii) they overexpress NK-1 receptors; iii) the NK-1 receptor is involved in their viability; iv) SP induces their proliferation; v) NK-1 receptor antagonists block SP-induced mitogen stimulation of these cells; vi) the specific antitumor action of such antagonists on these cells occurs through the NK-1 receptor; and vii) BC cell death is due to apoptosis. We also found NK-1 receptors and SP in all human BC samples studied. The NK-1 receptor may be a promising target in the treatment of BC and NK-1 receptor antagonists could be candidates as a new antitumor drug in the treatment of BC.

Substance P autocrine signaling contributes to persistent HER2 activation that drives malignant progression and drug resistance in breast cancer

ERBB receptor transmodulation by heterologous G-protein-coupled receptors (GPCR) generates functional diversity in signal transduction. Tachykinins are neuropeptides and proinflammatory cytokines that promote cell survival and cancer progression by activating several GPCRs. In this work, we found that the pain-associated tachykinin Substance P (SP) contributes to persistent transmodulation of the ERBB receptors, EGFR and HER2, in breast cancer, acting to enhance malignancy and therapeutic resistance. SP and its high-affinity receptor NK-1R were highly expressed in HER2(+) primary breast tumors (relative to the luminal and triple-negative subtypes) and were overall correlated with poor prognosis factors. In breast cancer cell lines and primary cultures derived from breast cancer samples, we found that SP could activate HER2. Conversely, RNA interference-mediated attenuation of NK-1R, or its chemical inhibition, or suppression of overall GPCR-mediated signaling, all strongly decreased steady-state expression of EGFR and HER2, establishing that their basal activity relied upon transdirectional activation by GPCR. Thus, SP exposure affected cellular responses to anti-ERBB therapies. Our work reveals an important oncogenic cooperation between NK-1R and HER2, thereby adding a novel link between inflammation and cancer progression that may be targetable by SP antagonists that have been clinically explored.