Dormant Tumor Cells Research Articles

Abstract MS2-2: Extra cellular matrix and dormancy

Abstract Breast cancer metastasis develops from disseminated cancer cells (DCCs) that leave the primary tumor and seed in distant organs. In those organs, DCCs undergo a period of dormancy during which cancer cells remain occult, in a non-proliferative state, before metastases become detectable. In this seminar I will discuss how disseminated cancer cells enter in dormancy at metastatic sites and the importance of the ECM in this process. We have found that dormant cancer cells express a specific set of ECM genes, "the matrisome", that is lost upon break from dormancy. ECM proteomics identify tumor-derived COL3A1 as a key ECM component required for tumor cell dormancy at metastatic organs. Intravital imaging and SHG microscopy reveals that the dormancy-to-reactivation transition is accompanied by changes in collagen three-dimensional architecture. Our data reveal a novel barrier to metastasis through a mechanism by which DCCs depend on the assembly of a pro-quiescence ECM to establish a niche that sustains dormancy. Citation Format: Jose Javier Bravo-Cordero. Extra cellular matrix and dormancy [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 MS2-2.

Regulation of dormancy during tumor dissemination: the role of the ECM.

The study of the metastatic cascade has revealed the complexity of the process and the multiple cellular states that disseminated cancer cells must go through. The tumor microenvironment and in particular the extracellular matrix (ECM) plays an important role in regulating the transition from invasion, dormancy to ultimately proliferation during the metastatic cascade. The time delay from primary tumor detection to metastatic growth is regulated by a molecular program that maintains disseminated tumor cells in a non-proliferative, quiescence state known as tumor cell dormancy. Identifying dormant cells and their niches in vivo and how they transition to the proliferative state is an active area of investigation, and novel approaches have been developed to track dormant cells during dissemination. In this review, we highlight the latest research on the invasive nature of disseminated tumor cells and their link to dormancy programs. We also discuss the role of the ECM in sustaining dormant niches at distant sites.

A timeline of tumour-associated macrophage biology.

Tumour progression is modulated by the local microenvironment. This environment is populated by many immune cells, of which macrophages are among the most abundant. Clinical correlative data and a plethora of preclinical studies in mouse models of cancers have shown that tumour-associated macrophages (TAMs) play a cancer-promoting role. Within the primary tumour, TAMs promote tumour cell invasion and intravasation and tumour stem cell viability and induce angiogenesis. At the metastatic site, metastasis-associated macrophages promote extravasation, tumour cell survival and persistent growth, as well as maintain tumour cell dormancy in some contexts. In both the primary and metastatic sites, TAMs are suppressive to the activities of cytotoxic T and natural killer cells that have the potential to eradicate tumours. Such activities suggest that TAMs will be a major target for therapeutic intervention. In this Perspective article, we chronologically explore the evolution of our understanding of TAM biology put into the context of major enabling advances in macrophage biology.

Could senescence phenotypes strike the balance to promote tumor dormancy?

After treatment and surgery, patient tumors can initially respond followed by a rapid relapse, or respond well and seemingly be cured, but then recur years or decades later. The state of surviving cancer cells during the long, undetected period is termed dormancy. By definition, the dormant tumor cells do not proliferate to create a mass that is detectable or symptomatic, but also never die. An intrinsic state and microenvironment that are inhospitable to the tumor would bias toward cell death and complete eradication, while conditions that favor the tumor would enable growth and relapse. In neither case would clinical dormancy be observed. Normal cells and tumor cells can enter a state of cellular senescence after stress such as that caused by cancer therapy. Senescence is characterized by a stable cell cycle arrest mediated by chromatin modifications that cause gene expression changes and a secretory phenotype involving many cytokines and chemokines. Senescent cell phenotypes have been shown to be both tumor promoting and tumor suppressive. The balance of these opposing forces presents an attractive model to explain tumor dormancy: phenotypes of stable arrest and immune suppression could promote survival, while reversible epigenetic programs combined with cytokines and growth factors that promote angiogenesis, survival, and proliferation could initiate the emergence from dormancy. In this review, we examine the phenotypes that have been characterized in different normal and cancer cells made senescent by various stresses and how these might explain the characteristics of tumor dormancy.

KISS1 metastasis suppressor in tumor dormancy: a potential therapeutic target for metastatic cancers?

Present therapeutic approaches do not effectively target metastatic cancers, often limited by their inability to eliminate already-seeded non-proliferative, growth-arrested, or therapy-resistant tumor cells. Devising effective approaches targeting dormant tumor cells has been a focus of cancer clinicians for decades. However, progress has been limited due to limited understanding of the tumor dormancy process. Studies on tumor dormancy have picked up pace and have resulted in the identification of several regulators. This review focuses on KISS1, a metastasis suppressor gene that suppresses metastasis by keeping tumor cells in a state of dormancy at ectopic sites. The review explores mechanistic insights of KISS1 and discusses its potential application as a therapeutic against metastatic cancers by eliminating quiescent cells or inducing long-term dormancy in tumor cells.

Live Cell Lineage Tracing of Dormant Cancer Cells.

Breast cancer is a leading cause of global cancer-related deaths, and metastasis is the overwhelming culprit of poor patient prognosis. The most nefarious aspect of metastasis is dormancy, a prolonged period between primary tumor resection and relapse. Current therapies are insufficient at killing dormant cells; thus, they can remain quiescent in the body for decades until eventually undergoing a phenotypic switch, resulting in metastases that are more adaptable and drug resistant. Unfortunately, dormancy has few in vitro models, largely because lab-derived cell lines are highly proliferative. Existing models address tumor dormancy, not cellular dormancy, because tracking individual cells is technically challenging. To combat this problem, a live cell lineage approach to find and track individual dormant cells, distinguishing them from proliferative and dying cells over multiple days, is adapted. This approach is applied across a range of different in vitro microenvironments. This approach reveals that the proportion of cells that exhibit long-term quiescence is regulated by both cell intrinsic and extrinsic factors, with the most dormant cells found in 3D collagen gels. This paper envisions that this approach will prove useful to biologists and bioengineers in the dormancy community to identify, quantify, and study dormant tumor cells.

Abstract IA023: Age against the machine: How the aging microenvironment drives tumor progression

Abstract Patients 65 and older account for 69% of all new cancer diagnoses. Melanoma is a deadly disease, with chances of survival for patients with stage IV disease totaling only 27%. Age-related changes- both secreted and biophysical- drive metastasis, immune cell recruitment, and changes in the vasculature. Age-related changes also impact the ability of tumor cells to respond to targeted therapy, and new data from our lab indicate this may be sex specific. Our recent studies also show that age-related changes in the lung microenvironment facilitate a permissive niche for efficient outgrowth of disseminated dormant tumor cells, in contrast to the aged skin, where age-related changes suppress melanoma growth but drive dissemination. We now show that age-induced changes in distal metastatic microenvironments promote efficient reactivation of dormant melanoma cells in the lung due to changes in Wnt signaling pathways. Overall, our studies argue for placing mechanistic studies of cancer biology into the context of aging. Citation Format: Ashani Weeraratna. Age against the machine: How the aging microenvironment drives tumor progression [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr IA023.

Abstract PR015: Dormant mammary tumors persist long-term despite adaptive immunity by establishing a Treg-dominated niche via DKK3

Abstract A significant portion of breast cancer survivors eventually experience locoregional or metastatic recurrence. It is clear that the adaptive immune system controls proliferative tumor outgrowth, but how dormant tumor cells escape to eventually form new lesions remains unclear. Previous studies showed that proliferative D2A1 or D2.OR tumors are restricted by adaptive immunity in Balb/c versus SCID mice whereas dormant D2.1 tumors are largely unaffected. Further, D2.1 tumors are highly infiltrated with T cells, particularly CD4+ cells and Tregs. Thus, the aim of the present study was to determine the extent to which dormant D2.1 tumors evade antigen-specific immunity and how these tumors shape the T cell niche. Experiments were performed using Balb/c syngeneic D2 mammary tumor cells – D2A1 cells grow rapidly upon orthotopic injection, D2.OR cells proliferate but to a lesser degree than D2A1, and D2.1 cells remain dormant long term. Cells were also modified to express enhanced green fluorescent protein (eGFP) for use with Just eGFP Death Inducing (JeDI) T cells containing a T cell receptor (TCR) targeted to eGFP200-208. Transfer of JeDI T cells caused complete rejection of D2A1-eGFP tumors in the mammary fat pad (MFP) while no difference was observed in D2.1-eGFP tumors. In contrast, treatment with anti-CTLA4 alone, anti-PD-1 alone, or combined anti-CTLA4/PD-1 reduced D2.1 tumor progression compared to isotype control. Whole JeDI splenocytes were also stimulated in vitro with eGFP200-208 peptide in the presence of D2A1 or D2.1 conditioned medium (CM). Surprisingly, while CD8 cells proliferated in both D2A1 and D2.1 CM, CD4+ T cells also proliferated in D2.1 CM and the Treg fraction of CD4+ cells was significantly elevated in D2.1 CM compared to D2A1 CM or control medium. RNA-sequencing confirmed substantial immune activity in D2.1 tumors compared to D2A1. D2.1 tumors also displayed a hybrid epithelial/mesenchymal (E/M) phenotype and expressed genes associated with both mammary epithelium (Krt8, Krt14, Cdh1) and mesenchymal cells (Itga5, Snai2, Notch1, Zeb1). Moreover, Gene Set Enrichment Analysis (GSEA) showed an enrichment of mammary stem and luminal progenitor cell signatures in D2.1 tumors. Of the top upregulated genes, Dickkopf WNT Signaling Pathway Inhibitor 3 (DKK3) was chosen for further investigation. Interestingly, increased CD8 proliferation and IFNγ production, but decreased CD4 and Treg abundance, was observed in DKK3 shRNA knockdown (k/d) D2.1 CM compared to shScramble control. In vivo, overexpressing DKK3 in D2A1 cells significantly increased MFP tumor growth in Balb/c but not SCID mice, altered T cell activation locally and systemically, and decreased eGFP-specific antibodies. Similar results were observed in DKK3-overexpressing D2.OR tumors. Conversely, DKK3 k/d in D2.1 cells resulted in ~60% complete tumor rejection. Together, these data indicate that CD4 cells, particularly Tregs, are crucial in establishing a protective niche for long-term tumor dormancy with tumor-derived DKK3 emerging as a mediator of the Treg niche. Citation Format: Timothy N. Trotter, Delila Serra, Carina Dagotto, Tao Wang, Xiao Yang, Junping Wei, Gangjun Lei, H. Kim Lyerly, Zachary C. Hartman. Dormant mammary tumors persist long-term despite adaptive immunity by establishing a Treg-dominated niche via DKK3 [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 PR015.

Autophagy Inhibition Contributes to Apoptosis of PLK4 Downregulation-induced Dormant Cells in Colorectal Cancer.

Dormant cancer cells account for cancer recurrence, distant metastasis and drug resistance which lead to poor prognosis in colorectal cancer (CRC). However, little is known about the molecular mechanisms regulating tumor cell dormancy and how to eliminate dormant cancer cells. Recent studies indicate autophagy affects dormant tumor cell survival. Here, we found that polo-like kinases 4 (PLK4), a central regulator of the cell cycle and proliferation, plays a crucial role in regulating CRC cells dormancy both in vitro and in vivo. Downregulation of PLK4 induced dormancy and inhibited migration and invasion in different CRC cell lines. Clinically, PLK4 expression was correlated with the dormancy markers (Ki67, p-ERK, p-p38) and late recurrence in CRC tissues. Mechanistically, downregulation of PLK4 induced autophagy contributed to restoring phenotypically aggressive tumor cells to a dormant state through the MAPK signaling pathway, and inhibition of autophagy would trigger apoptosis of dormant cells. Our findings reveal that downregulation of PLK4-induced autophagy contributes to tumor dormancy and autophagy inhibition leads to apoptosis of CRC dormant cells. Our study is the first to report that downregulation PLK4 induced autophagy is an early event in CRC dormancy and highlights autophagy inhibitor as a potential therapeutic target for dormant cell elimination.

An Intelligent System to Enhance the Performance of Brain Tumor Diagnosis from MR Images.

In the human body, cancer is caused by aberrant cell proliferation. Brain tumors are created when cells in the human brain proliferate out of control. Brain tumors consist of two types: benign and malignant. The aberrant parts of benign tumors, which contain dormant tumor cells, can be cured with the appropriate medication. On the other hand, malignant tumors are tumors that contain abnormal cells and an unorganized area of these abnormal cells that cannot be treated with medication. Therefore, surgery is required to remove these brain tumors. Brain cancers are manually identified and diagnosed by a skilled radiologist using traditional procedures. It's a lengthy and error-prone procedure. As a result, it is unsuitable for emerging countries with large populations. So computer-assisted automatic identification and diagnosis of brain tumors are recommended. This work proposes and implements a CAD system for the diagnosis of brain cancers using magnetic resonance imaging (MRI). Preprocessing, segmentation, feature extraction, and classification are the stages of automatic brain MRI processing that necessitate software based on a sophisticated algorithm. Image normalization with contourlet transform (INCT) is used in the preprocessing step to remove undesirable or noisy data. The performance metrics such as PSNR, MSE, and RMSE are computed. Then, the modified hierarchical k-means with firefly clustering (MHKFC) technique is used in the segmentation step to precisely recover the afflicted (tumor) area from the preprocessed image. The enhanced monarch butterfly optimization (EMBO) is used to select and then extract the most important gray-level co-occurrence matrix feature from the segmented image. The classification task was finally completed using the adaptive neuro-fuzzy inference system (ANFIS). The overall classification accuracy is 95.4% ( BRATS 2015), 96.6% ( BRATS 2021), and 93.7% (clinical data) is obtained.

Regulation of Metastatic Tumor Dormancy and Emerging Opportunities for Therapeutic Intervention.

Cancer recurrence and metastasis, following successful treatment, constitutes a critical threat in clinical oncology and are the leading causes of death amongst cancer patients. This phenomenon is largely attributed to metastatic tumor dormancy, a rate-limiting stage during cancer progression, in which disseminated cancer cells remain in a viable, yet not proliferating state for a prolonged period. Dormant cancer cells are characterized by their entry into cell cycle arrest and survival in a quiescence state to adapt to their new microenvironment through the acquisition of mutations and epigenetic modifications, rendering them resistant to anti-cancer treatment and immune surveillance. Under favorable conditions, disseminated dormant tumor cells 're-awake', resume their proliferation and thus colonize distant sites. Due to their rarity, detection of dormant cells using current diagnostic tools is challenging and, thus, therapeutic targets are hard to be identified. Therefore, unraveling the underlying mechanisms required for keeping disseminating tumor cells dormant, along with signals that stimulate their "re-awakening" are crucial for the discovery of novel pharmacological treatments. In this review, we shed light into the main mechanisms that control dormancy induction and escape as well as emerging therapeutic strategies for the eradication of metastatic dormant cells, including dormancy maintenance, direct targeting of dormant cells and re-awakening dormant cells. Studies on the ability of the metastatic cancer cells to cease proliferation and survive in a quiescent state before re-initiating proliferation and colonization years after successful treatment, will pave the way toward developing innovative therapeutic strategies against dormancy-mediated metastatic outgrowth.

Asymmetric Cell Division and Tumor Heterogeneity.

Asymmetric cell division (ACD) gives rise to two daughter cells with different fates after mitosis and is a fundamental process for generating cell diversity and for the maintenance of the stem cell population. The cancer stem cell (CSC) theory suggests that CSCs with dysregulated self-renewal and asymmetric cell division serve as a source of intra-tumoral heterogeneity. This heterogeneity complicates the diagnosis and treatment of cancer patients, because CSCs can give rise to aggressive clones that are metastatic and insensitive to multiple drugs, or to dormant tumor cells that are difficult to detect. Here, we review the regulatory mechanisms and biological significance of asymmetric division in tumor cells, with a focus on ACD-induced tumor heterogeneity in early tumorigenesis and cancer progression. We will also discuss how dissecting the relationship between ACD and cancer may help us find new approaches for combatting this heterogeneity.

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.

Abstract 2451: Dormant mammary tumors resist antigen-specific killing and regulate systemic immunity in association with PTN and DKK3

Abstract Little is known regarding why the immune system is ineffective at eliminating certain disseminated/dormant tumor cells before overt metastatic recurrence. Previous findings revealed that the adaptive immune system reduces growth of proliferative D2A1 tumors in Balb/c versus SCID mice while dormant D2.1 tumors are largely unaffected by adaptive immunity, despite being significantly infiltrated by T cells. Therefore, the aim of the present study was to determine the downstream effects and molecular underpinnings of dormancy-mediated alterations to the immune environment. Experiments were performed using two independent clones of a spontaneous mammary tumor from a female Balb/c mouse that display varying degrees of dormancy in vivo. D2A1 cells grow rapidly upon orthotopic or systemic injection while D2.1 cells remain dormant long term in local and metastatic sites. Both cell lines were modified to express enhanced green fluorescent protein (eGFP) for use with Just eGFP Death Inducing (JeDI) T cells which contain a T cell receptor (TCR) targeted to eGFP200-208. Adoptive transfer of JeDI T cells caused complete rejection of D2A1-eGFP tumors in the mammary fat pad (MFP), while no difference in growth was observed in D2.1-eGFP tumors. Interestingly, contralateral MFP implantation of D2.1-eGFP tumors resulted in a partial rescue of D2A1-eGFP rejection suggesting systemic immune suppression by distant, dormant tumor cells. Bulk RNA-sequencing of D2A1 and D2.1 tumors revealed significant upregulation of pathways associated with immune activation and extracellular matrix (ECM) remodeling in dormant tumors. Further, Gene Set Enrichment Analysis (GSEA) showed an enrichment for signatures of mammary stem cells and luminal progenitor cells, as well as exhausted vs memory CD8 cells and T cell anergy, in D2.1 tumors. Of the top upregulated genes in D2.1 tumors, pleiotrophin (PTN) and Dickkopf WNT Signaling Pathway Inhibitor 3 (DKK3) were chosen for further investigation. Overexpressing PTN or DKK3 in D2A1 cells significantly increased MFP tumor growth in Balb/c but not SCID mice. In addition, PTN or DKK3 overexpression altered both local and systemic T cell profiles, including decreased effector memory (CD62l-, CD44+) and increased naïve (CD62l+, CD44-) CD4 and CD8 cells. Humoral immunity was also affected, as indicated by decreased eGFP-specific antibodies in serum from mice bearing PTN or DKK3 overexpressing tumors. Conversely, knocking down PTN or DKK3 in D2.1 cells had the opposite effect on systemic immunity. Taken together, these data indicate that dormant tumors can resist antigen-specific killing by CD8 T cells despite high T cell infiltration, and possibly suppress antigen-specific immunity in distant tumor sites. Moreover, both PTN and DKK3 emerge as potential mediators of dormancy-induced immune evasion. Citation Format: Timothy N. Trotter, Delila Serra, Carina Dagotto, Tao Wang, Xiao Yang, Junping Wei, Gangjun Lei, H. Kim Lyerly, Zachary C. Hartman. Dormant mammary tumors resist antigen-specific killing and regulate systemic immunity in association with PTN and DKK3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2451.

Abstract LB025: Malat1-Serpinb6b signaling blocks T cells-mediated pyroptosis and governs cancer dormancy metastatic reactivation

Abstract Metastatic relapse is the major causes of mortality in patients with cancer and occur due to metastatic reactivation of dormant tumor cells. Early dissemination of tumor cells undergoing a protected period of dormancy in the target organs potentially explains this prevalent clinical behavior. Long non-coding RNAs (lncRNAs) are involved in various biological processes and diseases. Malat1 is one of the most abundant and highly conserved nuclear lncRNAs and have shown the associated with metastasis and serving as a predictive marker for various tumor progression. However, the correlation of tumor intrinsic lncRNAs in regulation of tumor dormancy and immune evasion are largely unknown. Using an in vivo screening platform for the isolation of genetic entities involved in either dormancy or reactivation of breast cancer tumor cells, we have identified Malat1 as a positive mediator of metastatic reactivation. To dissect the functional role of Malat1 in metastatic reactivation, we developed a clean Malat1 knockout (KO) model using paired gRNA CRISPR-Cas9 in metastatic murine syngeneic breast cancer. As a proof of concept, we also used inducible knockdown system under in vivo models. To delineate the immune microenvironment, we used single cell RNA-seq, ChIRP-seq, multicolor flowcytometry, RNA-FISH, and coculture experiments. Our data revealed that deletion of Malat1 induces dormancy and attenuated the metastatic colonization resulting in long-term survival of syngeneic mice model. In contrast, overexpression of Malat1 leads to metastatic reactivation of dormant breast cancer cells. Interestingly, 4T1-Malat1 KO dormant breast cancer cells exhibit metastatic outgrowth in T cells defective mice. Our single-cell RNA-seq and multicolor flowcytometry evaluation reveal enhanced T cells and reduced neutrophils proportions in mice with Malat1 KO cells. This indicates a critical role of immune microenvironment via Malat1-dependent immune evasion. Additionally, Malat1 KO inhibits cancer stemness properties. Similarly, RNA-seq and ChIRP-seq data suggest that KO of Malat1 hampers immune evasion and downregulates metastasis associated genes including Serpins and Wnts. Additionally, our data strongly suggests that Malat1 KO cells persists as non-proliferative dormant cells in lung due to CD8+ T cell-umpired immune activity. Our mechanistic studies showed that Malat1 regulated Sepinb6b blocks the CstG enzymatic activity and suppress cleavage of GsdmD and T cells induced pyroptosis. Interestingly, rescue experiments suggest that Malat1 or Serpinb6b protects T cell-induced cell death and induces dormancy re-awakening thereby rescue the metastatic potential of 4T1 Malat1 KO cells. Combination of Malat1 ASO with double immune checkpoint inhibitors greatly affects the metastatic outgrowth in breast cancer. Taken together, our studies demonstrate that tumor intrinsic Malat1 regulates Serpinb6b that suppresses CstG-GsdmD mediated pyroptosis which eventually promotes immune evasion and breast cancer dormancy metastatic reactivation. Citation Format: Dhiraj Kumar, Filippo Giancotti. Malat1-Serpinb6b signaling blocks T cells-mediated pyroptosis and governs cancer dormancy metastatic reactivation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB025.

Abstract 2450: Investigating the intrinsic and extrinsic factors regulating breast cancer dormancy

Abstract Unfortunately, breast cancer can recur in patients upwards of 25 years after an initial diagnosis and “cure”. It was once thought that recurrence occurred within patients that harbored dormant breast disseminated tumor cells (DTCs) in distant organs that were not present in patients that did not recur. Interestingly, a significant percent of patients harbor DTCs, yet many do not recur, raising the critical question, what differentiates patients that experience a recurrence versus those who live with dormant DTCs for the rest of their lives? It is likely the answer lies in both cell intrinsic as well as extrinsic factors. Nevertheless, the extreme rarity of dormant DTCs has been the major obstacle to their study. To overcome this challenge, we developed an efficient system to isolate and study rare dormant tumor cells from metastatic organs. Using this system and single cell RNA-sequencing (scRNA-seq), we identified a group of genes differentially expressed in dormant breast cancer cells present in both bone and lung. While modulation of these genes individually had no impact on the metastatic behavior of breast cancer cells, we found that as a group, these genes predicted the dormancy phenotype in murine breast cancer models. Importantly, expression of these genes in primary human breast cancer tumors correlated with disease-free survival, suggesting these genes have predictive value in determining which patients are likely to recur. Moreover, we explored extrinsic mechanisms that impact dormancy and found that the chemotherapy reagent doxorubicin (Doxo) drastically changed the microenvironment in vivo, which allowed dormant breast cancer cells to grow robustly within the visceral fat and this was further exacerbated by a high fat diet. Further, we found that Doxo treatment induces significant adipose tissue dystrophy and macrophage infiltration, which may contribute to dormant metastatic outgrowth. Our study provides novel insight into breast cancer dormancy, and also reveals microenvironmental changes that impact dormant breast cancer cell outgrowth. Citation Format: Qihao Ren, Weng Hua Khoo, Jiayu Ye, Douglas V. Faget, Peter I. Croucher, Sheila A. Stewart. Investigating the intrinsic and extrinsic factors regulating breast cancer dormancy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2450.

Abstract SY24-04: And by a sleep to say we end: Tumor dormancy, aging, and recurrent disease

Abstract Disseminated cancer cells (DCCs) that escape the primary site can seed in distal tissues, but may take several years, or even decades to grow out into overt metastases, a phenomenon termed tumor dormancy. Despite its importance in metastasis and residual disease, few studies have been able to successfully model or characterize dormancy within melanoma. Here, we show that age-related changes in the lung microenvironment facilitate a permissive niche for efficient outgrowth of disseminated dormant tumor cells, in contrast to the aged skin, where age-related changes suppress melanoma growth but drive dissemination. A model of melanoma progression that addresses these microenvironmental complexities is the phenotype switching model, which argues that melanoma cells switch between a proliferative cell state and a slower-cycling, invasive state. We have previously shown that dermal fibroblasts are key orchestrators of promoting phenotype switching in primary melanoma tumors via changes in the secretion of soluble factors during aging. Our new data identify Wnt5A as a master regulator of activating melanoma DCC dormancy within the lung, which initially enables efficient dissemination and seeding of melanoma cells in metastatic niches. Age-induced reprogramming of lung fibroblasts increases their secretion of soluble Wnt factors enabling efficient metastatic outgrowth. Overall, we find that age-induced changes in distal metastatic microenvironments promotes efficient reactivation of dormant melanoma cells in the lung. Further these changes are also reflected in the response of tumor cells to therapy, linking dormancy to recurrent disease. Citation Format: Ashani T. Weeraratna. And by a sleep to say we end: Tumor dormancy, aging, and recurrent disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr SY24-04.

AGE/RAGE axis regulates reversible transition to quiescent states of ALK-rearranged NSCLC and pancreatic cancer cells in monolayer cultures

Cancer recurrence due to tumor cell quiescence after therapy and long-term remission is associated with cancer-related death. Previous studies have used cell models that are unable to return to a proliferative state; thus, the transition between quiescent and proliferative states is not well understood. Here, we report monolayer cancer cell models wherein the human non-small cell lung carcinoma cell line H2228 and pancreatic cancer cell line AsPC-1 can be reversibly induced to a quiescent state under hypoxic and serum-starved (HSS) conditions. Transcriptome and metabolome dual-omics profiles of these cells were compared with those of the human lung adenocarcinoma cell line A549, which was unable to enter a quiescent state under HSS conditions. The quiescence-inducible cells had substantially lower intracellular pyruvate and ATP levels in the quiescent state than in the proliferative state, and their response to sudden demand for energy was dramatically reduced. Furthermore, in quiescence-inducible cells, the transition between quiescent and proliferative states of these cells was regulated by the balance between the proliferation-promoting Ras and Rap1 signaling and the suppressive AGE/RAGE signaling. These cell models elucidate the transition between quiescent and proliferative states, allowing the development of drug-screening systems for quiescent tumor cells.

SOX4-mediated FBW7 transcriptional upregulation confers Tamoxifen resistance in ER+ breast cancers via GATA3 downregulation

AimTamoxifen-mediated endocrine therapy has been standard treatment for ER+ breast cancers; however, majority of them acquire resistance leading to disease relapse. Although numerous substrates of E3 ligase FBW7 are known, only a handful of factors that regulate FBW7 expression and function are reported. In particular, there remains a lack of in-depth understanding of FBW7 transcriptional regulation. Materials and methodsLuciferase reporter assay was performed after cloning full length and truncated FBW7 promoters followed by Chromatin immunoprecipitation assay to validate binding of SOX4 on FBW7 promoter. Transcriptional regulation of FBW7 by SOX4 and their biological consequences with respect to ER+ breast cancer was then evaluated using immunoblotting and other cell based assays. Key findingsSOX4 positively regulates FBW7 at transcriptional level by binding to three putative SOX4 biding sites within 3.1 kb long FBW7 promoter. Analysis of publicly available RNAseq datasets also showed a positive correlation between SOX4 and FBW7 mRNA in cancer cell lines and patient samples. qPCR and Immunoblotting confirmed that transiently or stably expressed SOX4 induced both endogenous FBW7 mRNA and protein levels. Our findings further demonstrated that increased levels of SOX4 and FBW7 in MCF7 mammospheres promoted cancer stemness and tumor cell dormancy. We further showed that both MCF7 mammospheres and MCFTAMR cells had elevated SOX4 levels which apparently enhanced FBW7 to potentiate GATA3 degradation leading to enhanced stemness, tumor dormancy and Tamoxifen resistance in MCF7TAMR as well as patients with ER+ breast cancers. SignificanceTargeting SOX4-FBW7-GATA3 axis may overcome tamoxifen resistance in ER+ breast cancers.

Selected Articles from This Issue

Highlights| May 04 2022 Selected Articles from This Issue Author & Article Information Online Issn: 1557-3125 Print Issn: 1541-7786 ©2022 American Association for Cancer Research2022American Association for Cancer Research Mol Cancer Res (2022) 20 (5): 671. https://doi.org/10.1158/1541-7786.MCR-20-5-HI Related Content A commentary has been published: Modeling Androgen Deprivation Therapy–Induced Prostate Cancer Dormancy and Its Clinical Implications A commentary has been published: Targeted Rejuvenation of Exhausted Chimeric Antigen Receptor T Cells Regresses Refractory Solid Tumors A commentary has been published: Inactivation of p21-Activated Kinase 2 (Pak2) Inhibits the Development of Nf2-Deficient Tumors by Restricting Downstream Hedgehog and Wnt Signaling View more A commentary has been published: MOB3A Bypasses BRAF and RAS Oncogene-Induced Senescence by Engaging the Hippo Pathway View less Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Article Versions Icon Versions Version of Record May 4 2022 Citation Selected Articles from This Issue. Mol Cancer Res 1 May 2022; 20 (5): 671. https://doi.org/10.1158/1541-7786.MCR-20-5-HI Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest Search Advanced Search Androgen-deprivation therapy (ADT) is a frontline therapy for prostate cancer patients. However, many patients experience post-ADT disease recurrence owing to ADT-induced tumor cell dormancy and subsequent dormant tumor cell outgrowth. Elucidating mechanisms underlying ADT-induced tumor cell dormancy could facilitate improved prognostic and therapeutic options for prostate cancer patients, but dormant tumor cells are difficult to study given they are rare and difficult to isolate. To address these challenges, Dong and colleagues used prostate cancer patient-derived xenograft models to derive and study ADT-induced tumor cell dormancy. Immunohistochemical analysis revealed two subtypes of tumor dormancy: tumor mass dormancy and cellular dormancy. Transcriptomic analysis of samples from each subtype defined a corresponding signature of differentially expressed genes—termed the pre-disposed gene signature (PGS)—between the subtypes. Training and validation of the PGS using clinical samples demonstrated the ability of the PGS to predict ADT responsiveness, suggesting molecular characteristics underlying tumor dormancy subtypes discovered in this... You do not currently have access to this content.