Breast Cancer Dormancy Research Articles

Mediator Subunit Med4 Enforces Metastatic Dormancy in Breast Cancer.

Long term survival of breast cancer patients is limited due to recurrence from metastatic dormant cancer cells. However, the mechanisms by which these dormant breast cancer cells survive and awaken remain poorly understood. Our unbiased genome-scale genetic screen in mice identified Med4 as a novel cancer-cell intrinsic gatekeeper in metastatic reactivation. MED4 haploinsufficiency is prevalent in metastatic breast cancer patients and correlates with poorer prognosis. Syngeneic xenograft models revealed that Med4 enforces breast cancer dormancy. Contrary to the canonical function of the Mediator complex in activating gene expression, Med4 maintains 3D chromatin compaction and enhancer landscape, by preventing enhancer priming or activation through the suppression of H3K4me1 deposition. Med4 haploinsufficiency disrupts enhancer poise and reprograms the enhancer dynamics to facilitate extracellular matrix (ECM) gene expression and integrin-mediated mechano-transduction, driving metastatic growth. Our findings establish Med4 as a key regulator of cellular dormancy and a potential biomarker for high-risk metastatic relapse.

Apolipoproteins have a major role in cellular tumor dormancy in triple negative breast cancer: In-silico study

Triple-negative breast cancer (TNBC) lacks estrogen, progesterone, and human epidermal growth factor receptors and has a poor prognosis as it is resistant to chemotherapy. A new treatment option for this type of cancer may be by putting these malignant cells into dormancy. The oocyte’s embryonic milieu presents a unique tumor reversion microenvironment by inducing growth arrest and changing cells’ phenotypes. We conducted an in-silico study to determine the most likely oocyte extract (OE) proteins involved in inducing dormancy using HDock, CluPro, and molecular dynamic (MD) simulation. Results showed low energy scores for complexes between OE proteins and four surface markers: K1C14, CLD3, CLD4, and ITA6. Apolipoprotein A1 (APOA1) and Apolipoprotein C3 (APOC3) showed the highest stability and affinity with these four surface markers: K1C14, CLD3, CLD4, and ITA6. These proteins are involved in key tumor-related pathways such as angiogenesis, proliferation, apoptosis, and migration. This will pave the way for exploring novel therapeutic options to induce dormancy in TNBC cells.

Inertial effect of cell state velocity on the quiescence-proliferation fate decision

Energy landscapes can provide intuitive depictions of population heterogeneity and dynamics. However, it is unclear whether individual cell behavior, hypothesized to be determined by initial position and noise, is faithfully recapitulated. Using the p21-/Cdk2-dependent quiescence-proliferation decision in breast cancer dormancy as a testbed, we examined single-cell dynamics on the landscape when perturbed by hypoxia, a dormancy-inducing stress. Combining trajectory-based energy landscape generation with single-cell time-lapse microscopy, we found that a combination of initial position and velocity on a p21/Cdk2 landscape, but not position alone, was required to explain the observed cell fate heterogeneity under hypoxia. This is likely due to additional cell state information such as epigenetic features and/or other species encoded in velocity but missing in instantaneous position determined by p21 and Cdk2 levels alone. Here, velocity dependence manifested as inertia: cells with higher cell cycle velocities prior to hypoxia continued progressing along the cell cycle under hypoxia, resisting the change in landscape towards cell cycle exit. Such inertial effects may markedly influence cell fate trajectories in tumors and other dynamically changing microenvironments where cell state transitions are governed by coordination across several biochemical species.

The potential role of collagen type VII in breast cancer proliferation

BackgroundBreast cancer is the most common cancer in women. Cancer cells can persist in a prolonged dormant state for years without any clinical evidence of disease creating an urgent need to better understand the molecular mechanisms leading to relapse. This study aimed to identify extracellular matrix (ECM) components associated with hypoxia-induced breast cancer dormancy. The effects of selected ECM proteins on breast cancer cell proliferation were analyzed, along with their correlation with established prognostic markers in human breast cancer tissue.Materials and methodsScreening of extracellular matrix proteins was performed in hypoxia-induced dormant MCF-7 breast cancer cells. Proliferation of MCF-7 cells in vitro was subsequently determined in the presence of recombinant ColVII. Adipose tissue-derived mesenchymal stem cells (AdMSCs) subpopulation overexpressing ColVII were indirectly isolated by ColVII receptor integrin-α6 specific antibodies. AdMSCs- MCF-7 3D spheroid cultures were generated to model solid tumour conditions. In addition, the association between ColVII and various prognostic markers was evaluated in clinical samples of human breast cancer tissue.ResultsDormant MCF-7 cells showed an elevated expression of ColVII while MCF-7 cells cultured on ColVII exhibited reduced proliferation in vitro. In AdMSCs-MCF-7 3D spheroids, a reduced proliferation of MCF-7 cells was observed in Int-α6+/ ColVIIhigh compared with Int-α6-/ ColVIIlow AdMSCs spheroids. In human tissue, high ColVII expression correlated to several positive prognostic markers. Staining for Cytokeratin-5 revealed that ColVIIhigh-expressing cells were predominantly myoepithelial cells.ConclusionColVII is associated with reduced proliferation of breast cancer cells in vitro. ColVII is strongly expressed in myoepithelial cells and in breast cancer tissue the high ColVII expression correlates with several well-known positive prognostic markers, highlighting its potential as a prognostic marker in breast cancer.

Abstract 6632: Adipocyte death drives dormant breast cancer cell reactivation

Abstract Despite significant responses to initial treatments, upwards of 30% of breast cancer patients will experience a recurrence of their disease. Unfortunately, there are few clinical features that predict which patients will recur, relegating patients and their doctors to a wait-and-see approach where they must remain vigilant. Recent studies have reported that the presence of disseminated tumor cells (DTCs) in the bone marrow of early-stage breast cancer patients predicts a higher chance of recurrence and that obese patients experience 35%-40% higher rates of recurrence than lean patients. Interestingly, in addition to increased adipocyte size, obese patients experience higher rates of adipocyte apoptosis, macrophage recruitment to adipocyte tissue, and increased inflammation, shown as the formation of crown-like structures (CLSs). Given the rising prevalence of obesity, the need for mechanistic studies to elucidate its contribution to breast cancer dormancy and recurrence is urgent. To investigate how microenvironmental changes associated with obesity affect breast cancer dormancy, we utilized a well-established syngeneic mouse model of ER+ breast cancer dormancy (D2.0R). We found that D2.0R cells remained dormant in the visceral fat of wildtype mice but were reactivated upon adipocyte death due to obesity or genetic manipulation, and this reactivation required the recruitment of macrophages. To understand why macrophages were recruited to the adipose tissue and how they led to dormant tumor cell reactivation, we profiled the microenvironmental changes in visceral fat using single-cell RNA-sequencing and found that the infiltrating macrophages exhibited unique pro-inflammatory and lipid regulatory phenotypes. Further investigation revealed that macrophages activated the integrin-focal adhesion kinase (FAK) pathway in dormant D2.0R cells and the inhibition of integrin and FAK inhibited this activation. Given tumor cells can metastasize to visceral fat depots in breast cancer patients, our findings provide an important model to determine what drives dormant tumor cell growth in adipose tissue. Our study provides novel insights into how tumor microenvironment (TME) impacts breast cancer dormancy and also highlights the importance of adipose tissue as a unique reservoir that potentiates cancer relapse. Citation Format: Xiaoyu Yuan, Qihao Ren, Sheila A. Stewart. Adipocyte death drives dormant breast cancer cell reactivation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6632.

Outlook and opportunities for engineered environments of breast cancer dormancy.

Dormant, disseminated breast cancer cells resist treatment and may relapse into malignant metastases after decades of quiescence. Identifying how and why these dormant breast cancer cells are triggered into outgrowth is a key unsolved step in treating latent, metastatic breast cancer. However, our understanding of breast cancer dormancy in vivo is limited by technical challenges and ethical concerns with triggering the activation of dormant breast cancer. In vitro models avoid many of these challenges by simulating breast cancer dormancy and activation in well-controlled, bench-top conditions, creating opportunities for fundamental insights into breast cancer biology that complement what can be achieved through animal and clinical studies. In this review, we address clinical and preclinical approaches to treating breast cancer dormancy, how precisely controlled artificial environments reveal key interactions that regulate breast cancer dormancy, and how future generations of biomaterials could answer further questions about breast cancer dormancy.

CDH2-microRNA Axis Provides Insights into Sustained Breast Cancer Dormancy in the Bone Marrow Niche

Despite long-term remission of breast cancer (BC), cancer resurgence remains a clinical issue. This issue is mostly due to BC cells (BCCs) being able to survive in dormancy for decades. This is particularly relevant to the bone marrow (BM) where the dormant BCCs survive as cancer stem cells (CSCs). The BM niche maintains BCCs in dormancy, and also mediates dedifferentiation of BCCs to CSCs. Since dormancy can occur at any time during the disease, including decades before clinical diagnosis, it is important to understand how these cells survive to allow for the development of safe treatments. Dormant BCCs establish gap junctional intercellular communication (GJIC) with BM niche such as fibroblasts and mesenchymal stem cells (MSCs). GJIC requires connexin 43 (Cx43) but cannot be a safe target since this connexin is also important for hematopoietic function. This study focused on N-cadherin (CDH2) because it facilitates Cx43-mediated GJIC between BCCs and BM niche cells. We found Cx43 and CDH2 mutually regulated their gene expression. Cloning of the 5′ regulatory regions of CDH2 unraveled DNA sequences as possible elements of repressor and activator transcription. We identified potential transcription factors (TFs) that could regulate CDH2 and showed how miRNAs that could cross GJIC might be responsible for regulating the TFs. The axis developed by CDH2 and miRNAs provide insights into how CDH2 is maintained at low level to sustain BC dormancy. The findings, together with previous findings, provide avenues for therapeutic intervention to safely reverse and target dormant BCCs in the BM niche.

Bone Marrow Stroma Co-cultivation Model of Breast Cancer Dormancy.

Breast cancer cells metastasize to the bone marrow before a primary tumor is detected. Most micrometastases die in this hostile microenvironment, but some survive and enter a state of dormancy and chemoresistance due to their close interaction with cells in the bone marrow hematopoietic niche. Over many years, some of the cells reawaken and result in metastatic disease that cannot be cured. Analyzing the cellular and molecular interactions between cancer and bone marrow niche cells requires relevant models that can be manipulated and studied. Generation of bone marrow stromacultures in vitro permits the formation of cellular monolayers upon which breast cancer cells can be co-cultivated and their behavior interrogated using a variety of techniques. This manuscript describes the basic techniques for generating bone marrow stromal monolayers, co-incubating cancer cells and determining the effects on cancer cell proliferation and molecular signaling.

THU485 The Impact Of Cured, Fried Bacon On The Reemergence From Breast Cancer Dormancy

Abstract Disclosure: C.P. Schane: None. A. Nelczyk: None. C. Chen: None. H. Vidana Gamage: None. M. Kadiri: None. M.T. McHenry: None. S. Bendre: None. N. Krawczynska: None. M.A. Henn: None. D.C. Castro: None. J. Chen: None. R.I. Tejeda: None. S. Hsiao: None. N.J. Engeseth: None. J.V. Sweedler: None. M.K. Wendt: None. T. Fan: None. W.G. Helferich: None. E.R. Nelson: None. One in eight women will develop breast cancer in her lifetime, with metastasis being the leading cause of mortality. Once the cells colonize the metastatic site, they do not always immediately begin to proliferate, but remain dormant. These dormant cells reside in the tissue, until mechanisms, which remain unknown, awaken the dormant cells and they resume malignant proliferation. Due to the large and growing population of breast cancer survivors at risk of metastatic recurrence, there is an urgent need to elucidate the mechanisms of dormancy and develop therapeutics to prevent reemergence. Elevated levels of circulating cholesterol are a risk factor for breast cancer recurrence. Preclinical work has demonstrated that oxysterol cholesterol metabolites such as 27-hydroxycholesterol (27HC) can promote tumor metastasis. Here, we show that exogenous 27HC lead to a more rapid reemergence from dormancy, using the syngeneic mouse D2.0R model of mammary cancer dormancy. Since it would be expected that cooking high cholesterol foods, such as bacon, under oxidative conditions, such as pan-frying, would produce fat containing cancer-promoting cholesterol metabolites, we hypothesized that consumption of such cooked foods would also promote reemergence from dormancy. Interestingly, consumption of cured, fried bacon fat (cfBF), but not uncured fried bacon fat (ufBF) resulted in reemergence. When metastatic tissues were assessed, it was found that consumption of cfBF dramatically reduced mast cell numbers. Since mast cells (MC) are major contributors to local histamine production, we next tested whether various anti-histamines could alter dormancy. This led to the striking finding that H2 antagonists promoted the breaking of dormancy. Our ongoing work is aimed at further elucidating this novel metastatic axis: Diet - MC - H2 - Dormancy, with the ultimate goal of leveraging it to develop novel therapeutic targets or lifestyle interventions. Therefore, our results are expected to provide the foundation for dietary and medical approaches to reduce the risk of recurrence among breast cancer survivors. This work was supported by the American Institute for Cancer Research grant (713063), the National Cancer Institute (R01CA234025) and Department of Defense Breast Cancer Research Program Era of Hope Scholar Award (BC200206). Further support awarded to ATN from a National Institutes of Environment Health Sciences and Research Training in Toxicology and Environmental Health (T32) Fellowship (ES007326). Presentation: Thursday, June 15, 2023

Taxane chemotherapy induces stromal injury that leads to breast cancer dormancy escape.

A major cause of cancer recurrence following chemotherapy is cancer dormancy escape. Taxane-based chemotherapy is standard of care in breast cancer treatment aimed at killing proliferating cancer cells. Here, we demonstrate that docetaxel injures stromal cells, which release protumor cytokines, IL-6 and granulocyte colony stimulating factor (G-CSF), that in turn invoke dormant cancer outgrowth both in vitro and in vivo. Single-cell transcriptomics shows a reprogramming of awakened cancer cells including several survival cues such as stemness, chemoresistance in a tumor stromal organoid (TSO) model, as well as an altered tumor microenvironment (TME) with augmented protumor immune signaling in a syngeneic mouse breast cancer model. IL-6 plays a role in cancer cell proliferation, whereas G-CSF mediates tumor immunosuppression. Pathways and differential expression analyses confirmed MEK as the key regulatory molecule in cancer cell outgrowth and survival. Antibody targeting of protumor cytokines (IL-6, G-CSF) or inhibition of cytokine signaling via MEK/ERK pathway using selumetinib prior to docetaxel treatment prevented cancer dormancy outgrowth suggesting a novel therapeutic strategy to prevent cancer recurrence.

Targeting myeloid-derived suppressor cells in combination with tumor cell vaccination predicts anti-tumor immunity and breast cancer dormancy: an in silico experiment

Among the different breast cancer subsets, triple-negative breast cancer (TNBC) has the worst prognosis and limited options for targeted therapies. Immunotherapies are emerging as novel treatment opportunities for TNBC. However, the surging immune response elicited by immunotherapies to eradicate cancer cells can select resistant cancer cells, which may result in immune escape and tumor evolution and progression. Alternatively, maintaining the equilibrium phase of the immune response may be advantageous for keeping a long-term immune response in the presence of a small-size residual tumor. Myeloid-derived suppressor cells (MDSCs) are activated, expanded, and recruited to the tumor microenvironment by tumor-derived signals and can shape a pro-tumorigenic micro-environment by suppressing the innate and adaptive anti-tumor immune responses. We recently proposed a model describing immune-mediated breast cancer dormancy instigated by a vaccine consisting of dormant, immunogenic breast cancer cells derived from the murine 4T1 TNBC-like cell line. Strikingly, these 4T1-derived dormant cells recruited fewer MDSCs compared to aggressive 4T1 cells. Recent experimental studies demonstrated that inactivating MDSCs has a profound impact on reconstituting immune surveillance against the tumor. Here, we developed a deterministic mathematical model for simulating MDSCs depletion from mice bearing aggressive 4T1 tumors resulting in immunomodulation. Our computational simulations indicate that a vaccination strategy with a small number of tumor cells in combination with MDSC depletion can elicit an effective immune response suppressing the growth of a subsequent challenge with aggressive tumor cells, resulting in sustained tumor dormancy. The results predict a novel therapeutic opportunity based on the induction of effective anti-tumor immunity and tumor dormancy.

Dormancy in Breast Cancer.

The pattern of delayed recurrence in a subset of breast cancer patients has long been explained by a model that incorporates a variable period of cellular or tumor mass dormancy prior to disease relapse. In this review, we critically evaluate existing data to develop a framework for inferring the existence of dormancy in clinical contexts of breast cancer. We integrate these clinical data with rapidly evolving mechanistic insights into breast cancer dormancy derived from a broad array of genetically engineered mouse models as well as experimental models of metastasis. Finally, we propose actionable interventions and discuss ongoing clinical trials that translate the wealth of knowledge gained in the laboratory to the long-term clinical management of patients at a high risk of developing recurrence.

Abstract 86: Chemotherapy-induced microenvironmental changes promote dormant breast cancer cell outgrowth in adipose tissue

Abstract Despite the high 5-year survival rate for early-stage breast cancer patients, late recurrence of the disease remains a major challenge. Breast cancer can recur in approximately 20-25% of patients months to decades after an initial diagnosis, and there are few biomarkers that predict which patients will suffer from the recurrent disease. Unfortunately, this means clinicians and their patients must take a frustrating wait-and-see approach. Notably, disseminated tumor cells (DTCs) are frequently detected in early-stage breast cancer patients, and their presence predicts a higher chance of recurrence. However, why some patients with DTCs recur while others do not remains a mystery. Previous work has suggested that changes in the tumor microenvironment (TME) play an important role in the maintenance of tumor cell dormancy. When assessing the impact of doxorubicin (DOXO), a chemotherapeutic agent often used to treat breast cancer patients, on the TME, we noted that DOXO treatment led to the activation of dormant breast cancer cells in the visceral adipose tissue. Moreover, in accordance with the clinical observation that obese patients suffer a higher risk of cancer recurrence, we found that diet-induced obesity further exacerbated DOXO ability to reactivate dormant breast cancer cells in adipose tissue and this reactivation was associated with robust macrophage infiltration. These findings were interesting in light of our observation that tumor cells can metastasize to visceral fat depots in breast cancer patients. To understand why macrophages were recruited to the adipose tissue and how they led to tumor cell reactivation, we profiled the microenvironmental changes in visceral fat from Veh- and Doxo- treated mice using single-cell RNA-sequencing and found that the infiltrating macrophages exhibited unique pro-inflammatory and lipid-regulatory phenotypes. Our study provides novel insights into how TME impacts breast cancer dormancy and also highlights the importance of adipose tissue as a unique reservoir that potentiates cancer relapse. Citation Format: Qihao Ren, Jiayu Ye, Xiaoyu Yuan, Sheila Stewart. Chemotherapy-induced microenvironmental changes promote dormant breast cancer cell outgrowth in adipose tissue [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 86.

Dynamic bioinspired coculture model for probing ER+ breast cancer dormancy in the bone marrow niche.

Late recurrences of breast cancer are hypothesized to arise from disseminated tumor cells (DTCs) that reactivate after dormancy and occur most frequently with estrogen receptor-positive (ER+) breast cancer cells (BCCs) in bone marrow (BM). Interactions between the BM niche and BCCs are thought to play a pivotal role in recurrence, and relevant model systems are needed for mechanistic insights and improved treatments. We examined dormant DTCs in vivo and observed DTCs near bone lining cells and exhibiting autophagy. To study underlying cell-cell interactions, we established a well-defined, bioinspired dynamic indirect coculture model of ER+ BCCs with BM niche cells, human mesenchymal stem cells (hMSCs) and fetal osteoblasts (hFOBs). hMSCs promoted BCC growth, whereas hFOBs promoted dormancy and autophagy, regulated in part by tumor necrosis factor-α and monocyte chemoattractant protein 1 receptor signaling. This dormancy was reversible by dynamically changing the microenvironment or inhibiting autophagy, presenting further opportunities for mechanistic and targeting studies to prevent late recurrence.

Host-Related Factors in the Interplay among Inflammation, Immunity and Dormancy in Breast Cancer Recurrence and Prognosis: An Overview for Clinicians.

A significant proportion of patients treated for early breast cancer develop medium-term and late distant recurrence. The delayed manifestation of metastatic disease is defined as "dormancy". This model describes the aspects of the clinical latency of isolated metastatic cancer cells. Dormancy is regulated by extremely complex interactions between disseminated cancer cells and the microenvironment where they reside, the latter in turn influenced directly by the host. Among these entangled mechanisms, inflammation and immunity may play leading roles. This review is divided into two parts: the first describes the biological underpinnings of cancer dormancy and the role of the immune response, in particular, for breast cancer; the second provides an overview of the host-related factors that may influence systemic inflammation and immune response, subsequently impacting the dynamics of breast cancer dormancy. The aim of this review is to provide physicians and medical oncologists a useful tool to understand the clinical implications of this relevant topic.

Abstract A010: MYC as a master regulator of dormancy in triple negative breast cancer

Abstract Dormancy is a major clinical problem in breast cancer. Although the five-year survival rate is high, 15% of the patients will relapse. Cancer cells that disseminate from the tumor (DTCs) can enter a dormant state that allows survival in the face of standard-of-care therapies. These DTCs are the source of cancer recurrence. Currently little is known about the molecular drivers that initiate dormancy. MYC is a well-known oncogene that is aberrantly regulated in many cancers, including breast cancer. It is involved in proliferation, tumorigenesis, and diapause. We propose that MYC is also a master regulator of dormancy. To investigate its role in dormancy, we generated cell lines with regulatable levels of MYC expression. Using an in vitro dormancy assay, we have shown that reduced MYC levels induce dormancy in otherwise aggressive cell lines. In mice bearing human breast tumors, the loss of MYC activity following primary tumor removal greatly reduces the extent of metastasis. The DTCs in lungs, livers, spine, and femurs are maintained as small clusters with few cells, while control mice have many and large metastases. MYC reduction maintains the DTCs in this dormant-like state for at least 32 days after primary tumor removal. Importantly, when MYC levels are restored, the DTCs exit the dormant state, and overt metastasis ensues. Currently, we are comparing the transcriptomes of dormant DTCs to actively growing metastatic cells to generate a MYC-driven dormancy signature that will elucidate potential dormancy genes to target therapeutically in the clinic. To complement our genetic studies, we are investigating pharmacological suppression of MYC activity. The bromodomain inhibitor I-BET151 reduces MYC protein levels and induces dormancy in our in vitro assay. Mice treated with I-BET151 after primary tumor removal had significantly reduced levels of metastasis in lung, liver, and spine when compared to their non-treated counterparts. Testing of this compound in an immune-competent preclinical model is currently underway. Our data imply that MYC is an important regulator of dormancy in breast cancer. Our future experiments will elucidate dormancy genes as potential targets that could lead to life-saving therapies in the clinic. Citation Format: Charlotte Roelofs, Kellie A. Mouchemore, Anannya Chakrabarti, Richard P. Redvers, Robin L. Anderson. MYC as a master regulator of dormancy in triple negative breast cancer [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A010.

PAQR8 promotes breast cancer recurrence and confers resistance to multiple therapies

BackgroundBreast cancer mortality is principally due to recurrent disease that becomes resistant to therapy. We recently identified copy number (CN) gain of the putative membrane progesterone receptor PAQR8 as one of four focal CN alterations that preferentially occurred in recurrent metastatic tumors compared to primary tumors in breast cancer patients. Whether PAQR8 plays a functional role in cancer is unknown. Notably, PAQR8 CN gain in recurrent tumors was mutually exclusive with activating ESR1 mutations in patients treated with anti-estrogen therapies and occurred in > 50% of both patients treated with anti-estrogen therapies and those treated with chemotherapy or anti-Her2 agents.MethodsWe used orthotopic mouse models to determine whether PAQR8 overexpression or deletion alters breast cancer dormancy or recurrence following therapy. In vitro studies, including assays for colony formation, cell viability, and relative cell fitness, were employed to identify effects of PAQR8 in the context of therapy. Cell survival and proliferation were quantified by immunofluorescence staining for markers of apoptosis and proliferation. Sphingolipids were quantified by liquid chromatography-high resolution mass spectrometry.ResultsWe show that PAQR8 is necessary and sufficient for efficient mammary tumor recurrence in mice, spontaneously upregulated and CN gained in recurrent tumors that arise following therapy in multiple mouse models, and associated with poor survival following recurrence as well as poor overall survival in breast cancer patients. PAQR8 promoted resistance to therapy by enhancing tumor cell survival following estrogen receptor pathway inhibition by fulvestrant or estrogen deprivation, Her2 pathway blockade by lapatinib or Her2 downregulation, and treatment with chemotherapeutic agents. Pro-survival effects of PAQR8 were mediated by a Gi protein-dependent reduction in cAMP levels, did not require progesterone, and involved a PAQR8-dependent decrease in ceramide levels and increase in sphingosine-1-phosphate levels, suggesting that PAQR8 may possess ceramidase activity.ConclusionsOur data provide in vivo evidence that PAQR8 plays a functional role in cancer, implicate PAQR8, cAMP, and ceramide metabolism in breast cancer recurrence, and identify a novel mechanism that may commonly contribute to the acquisition of treatment resistance in breast cancer patients.

Modeling ER+ breast cancer dormancy in mice

Modeling ER+ breast cancer dormancy in mice

Stromal Co-Cultivation for Modeling Breast Cancer Dormancy in the Bone Marrow.

Simple SummaryCancer cells travel to far away parts of the body before the original cancer can be detected. Breast cancer cells travel mainly to the bone marrow, where they are kept in a quiet, non-dividing, dormant state for many years by cells and proteins in the bone marrow. These metastatic cancer cells wake up at a steady rate over the years and result in incurable disease. This paper outlines how to study the interactions of cells that live in the bone marrow with cancer cells in the laboratory. We describe how to grow mixtures of a variety of bone marrow-residing cells to generate cell layers upon which cancer cells can be grown. Using this system, we can study their effects on cancer cell growth or dormancy and the biology of the interactions. With this approach, we can study how to either eliminate the cancer cells or prevent them from waking up.Cancers metastasize to the bone marrow before primary tumors can be detected. Bone marrow micrometastases are resistant to therapy, and while they are able to remain dormant for decades, they recur steadily and result in incurable metastatic disease. The bone marrow microenvironment maintains the dormancy and chemoresistance of micrometastases through interactions with multiple cell types and through structural and soluble factors. Modeling dormancy in vitro can identify the mechanisms of these interactions. Modeling also identifies mechanisms able to disrupt these interactions or define novel interactions that promote the reawakening of dormant cells. The in vitro modeling of the interactions of cancer cells with various bone marrow elements can generate hypotheses on the mechanisms that control dormancy, treatment resistance and reawakening in vivo. These hypotheses can guide in vivo murine experiments that have high probabilities of succeeding in order to verify in vitro findings while minimizing the use of animals in experiments. This review outlines the existing data on predominant stromal cell types and their use in 2D co-cultures with cancer cells.

Clinical and Biological Aspects of Disseminated Tumor Cells and Dormancy in Breast Cancer.

Progress in detection and treatment have drastically improved survival for early breast cancer patients. However, distant recurrence causes high mortality and is typically considered incurable. Cancer dissemination occurs via circulating tumor cells (CTCs) and up to 75% of breast cancer patients could harbor micrometastatses at time of diagnosis, while metastatic recurrence often occurs years to decades after treatment. During clinical latency, disseminated tumor cells (DTCs) can enter a state of cell cycle arrest or dormancy at distant sites, and are likely shielded from immune detection and treatment. While this is a challenge, it can also be seen as an outstanding opportunity to target dormant DTCs on time, before their transformation into lethal macrometastatic lesions. Here, we review and discuss progress made in our understanding of DTC and dormancy biology in breast cancer. Strides in our mechanistic insights of these features has led to the identification of possible targeting strategies, yet, their integration into clinical trial design is still uncertain. Incorporating minimally invasive liquid biopsies and rationally designed adjuvant therapies, targeting both proliferating and dormant tumor cells, may help to address current challenges and improve precision cancer care.