Early Tumor Cell Dissemination Research Articles

HERC5 downregulation in non-small cell lung cancer is associated with altered energy metabolism and metastasis

BackgroundMetastasis is the leading cause of cancer-related death in non-small cell lung cancer (NSCLC) patients. We previously showed that low HERC5 expression predicts early tumor dissemination and a dismal prognosis in NSCLC patients. Here, we performed functional studies to unravel the mechanism underlying the “metastasis-suppressor” effect of HERC5, with a focus on mitochondrial metabolism pathways.MethodsWe assessed cell proliferation, colony formation potential, anchorage-independent growth, migration, and wound healing in NSCLC cell line models with HERC5 overexpression (OE) or knockout (KO). To study early tumor cell dissemination, we used these cell line models in zebrafish experiments and performed intracardial injections in nude mice. Mass spectrometry (MS) was used to analyze protein changes in whole-cell extracts. Furthermore, electron microscopy (EM) imaging, cellular respiration, glycolytic activity, and lactate production were used to investigate the relationships with mitochondrial energy metabolism pathways.ResultsUsing different in vitro NSCLC cell line models, we showed that NSCLC cells with low HERC5 expression had increased malignant and invasive properties. Furthermore, two different in vivo models in zebrafish and a xenograft mouse model showed increased dissemination and metastasis formation (in particular in the brain). Functional enrichment clustering of MS data revealed an increase in mitochondrial proteins in vitro when HERC5 levels were high. Loss of HERC5 leads to an increased Warburg effect, leading to improved adaptation and survival under prolonged inhibition of oxidative phosphorylation.ConclusionsTaken together, these results indicate that low HERC5 expression increases the metastatic potential of NSCLC in vitro and in vivo. Furthermore, HERC5-induced proteomic changes influence mitochondrial pathways, ultimately leading to alterations in energy metabolism and demonstrating its role as a new potential metastasis suppressor gene.

Abstract 2304: Detection of early-disseminated cancer cells with deep learning-enabled holographic imaging

Abstract Recent research increasingly validates the early dissemination of tumor cells in peripheral blood during the nascent stages of cancer, often preceding clinical identification of the primary tumor. This emerging evidence emphasizes the potential of Circulating Tumor Cells (CTCs) as early indicators for cancer. Despite their significance, CTCs are exceptionally rare compared to normal blood cells, which presents a considerable challenge in detection, particularly during early stages of cancer. Traditional detection methods, such as those based on nucleated cell enrichment, antibody labeling and fluorescence imaging, encounter notable limitations when applied in the context of early detection. These limitations arise from the inherent heterogeneity of CTCs, and the multistep process involved in labeling and manual enumeration, compromising cell viability and resulting in cell loss. This loss becomes particularly problematic in the context of early cancer detection scenarios where the tumor burden is extremely low, and any cell loss can significantly impact assay sensitivity. To overcome these challenges, we propose an innovative CTC detection approach employing a deep learning framework combined with holographic imaging. This technique utilizes coherent light to generate holograms from cell samples, capturing detailed 3D morphological and optical properties of individual cells. We developed a custom convolutional neural network designed to facilitate high-throughput cell sorting in real-time. Trained on healthy blood samples and diverse cancer cell lines, the dataset consists of more than 50 million cellular holograms enhanced by proprietary Gaussian annotation and image augmentation strategies. Moreover, by combining the morphological signatures from holography with antigen signatures (e.g. HER2/ER/PR) in real-time, our model demonstrates the ability to detect less than 1 false positive per 1 million nucleated cells, highlighting its potential as a robust tool for targeted early-stage breast cancer detection. Our technology represents highly sensitive alternative to traditional screening methods, with the promise of enhancing patient outcomes. Citation Format: Nicholas Heller, Kevin Mallery, Nathaniel Bristow, Yash Travadi, Eng Hock Lee, Jiarong Hong. Detection of early-disseminated cancer cells with deep learning-enabled holographic imaging [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 2304.

Gut colonization with an obesity-associated enteropathogenic microbe modulates the premetastatic niches to promote breast cancer lung and liver metastasis.

Obesity, an independent risk factor for breast cancer growth and metastatic progression, is also closely intertwined with gut dysbiosis; and both obese state and dysbiosis promote each other. Enteric abundance of Bacteroides fragilis is strongly linked with obesity, and we recently discovered the presence of B. fragilis in malignant breast cancer. Given that enterotoxigenic B. fragilis or ETBF, which secretes B. fragilis toxin (BFT), has been identified as a procarcinogenic microbe in breast cancer, it is necessary to examine its impact on distant metastasis and underlying systemic and localized alterations promoting metastatic progression of breast cancer. We used syngeneic mammary intraductal (MIND) model harboring gut colonization with ETBF to query distant metastasis of breast cancer cells. Alterations in the immune network and cytokines/chemokines in the tumor microenvironment and distant metastatic sites were examined using flow cytometry, immunohistochemistry, and multiplex arrays. ETBF infection initiates a systemic inflammation aiding in the establishment of the premetastatic niche formation in vital organs via increased proinflammatory and protumorigenic cytokines like IL17A, IL17E, IL27p28, IL17A/F, IL6, and IL10 in addition to creating a prometastatic immunosuppressive environment in the liver and lungs rich in myeloid cells, macrophages, and T regulatory cells. It induces remodeling of the tumor microenvironment via immune cell and stroma infiltration, increased vasculogenesis, and an EMT-like response, thereby encouraging early metastatic dissemination ready to colonize the conducive environment in liver and lungs of the breast tumor-bearing mice. In this study, we show that enteric ETBF infection concomitantly induces systemic inflammation, reshapes the tumor immune microenvironment, and creates conducive metastatic niches to potentiate early dissemination and seeding of metastases to liver and lung tissues in agreement with the "seed and soil hypothesis." Our results also support the ETBF-induced "parallel model" of metastasis that advocates for an early dissemination of tumor cells that form metastatic lesions independent of the primary tumor load.

Abstract PR011: The glutathione S-transferase, Gstt1 is a robust driver of survival and dissemination in metastases

Abstract Identifying adaptive mechanisms of metastatic cancer cells remains an elusive question in the treatment of metastatic disease, particularly in pancreatic cancer (PDA), where the majority of patients present with metastatic lesions at the time of diagnosis. A loss-of-function shRNA targeted screen in metastatic-derived cells identified Gstt1, a member of the glutathione S-transferase superfamily, as uniquely required for metastasis and dissemination however dispensable for primary tumor growth. Gstt1 is expressed in early disseminated tumor cells (DTCs), is retained within a subpopulation of slow-cycling cells within established metastases and its inhibition completely abolished macrometastatic lesions. This distinct Gstt1high population is highly metastatic and retains slow-cycling phenotypes, EMT features, and DTC characteristics compared to the Gstt1low population. Mechanistic studies indicate that in this subset of cells, Gstt1 maintains metastases by binding to and modifying intracellular fibronectin, regulating fibronectin secretion from cancer cells and deposition into the metastatic microenvironment. We identified Gstt1 as a novel mediator of metastasis, highlighting the importance of metastatic heterogeneity and its influence on the metastatic tumor microenvironment. Citation Format: Christina M. Ferrer. The glutathione S-transferase, Gstt1 is a robust driver of survival and dissemination in metastases [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 PR011.

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 3643: The role of HBP1 in controlling breast cancer dormancy reawakening

Abstract At least 22% of breast cancer (BrCa) cases recur after 3 to 15 years, typically at metastatic sites such as the bone. Bone metastases derive from early disseminated tumor cells that become dormant because of interaction with specific cells that define the endosteal niche (EN) microenvironment. However, outside knowing that dormancy is driven by a p38MAPKhi, ERK1/2lo activation profile, our understanding of what factors regulate dormancy maintenance and reawakening is poor. We used a genomic shRNA screen to identify HBP1 as a suppressor of BrCa dormancy reawakening in a 3D-EN culture system. Our data indicate that under 3D-EN conditions, HBP1 is upregulated by p38MAPK, interacts with the metastasis suppressors, BRMS1 and BRMS1L, and with the histone modifiers, SIN3A and HDAC1-3. We hypothesize that HBP1 suppresses p38MAPK-mediated dormancy reawakening by complexing with BRMS1/BRMS1L/SIN3A to alter cell cycle gene expression through histone landscape remodeling. HBP1 suppresses the expression of cell cycle progression genes, such as MYC and CCND1, and concomitantly upregulates cyclin kinase inhibitors, p16 and p21. HBP1 RNA and protein levels are decreased in BrCa metastases relative to primary tumors, and this downregulation correlates with poorer overall survival. We are investigating whether the anti-histiminic drug, cyproheptadine, which upregulates HBP1 expression through the activation of p38MAPK, can suppress dormancy reawakening of BrCa cells in 3D-EN cultures and in in vivo models of bone dormancy using mouse mammary carcinoma D2A1 cell lines with varying abilities to form active or dormant metastatic bone colonization. Data will be shown addressing how cell-cell interactions and secretory factors between BrCa and bone EN cells facilitates dormancy signaling through a p38MAPK/HBP1/BRMS1 axis, and how drugs such as cyproheptadine agonize that pathway in order to prevent the reawakening that drives the growth of BrCa metastases in the bone, thereby increasing overall survival. Citation Format: Irwin H. Gelman, Seamus Degan, Henry G. Withers, Subrahmanya Anirudh Kaligotla Venkata. The role of HBP1 in controlling breast cancer dormancy reawakening [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 3643.

Low RAI2 expression is a marker of poor prognosis in breast cancer.

Retinoic acid-induced 2 (RAI2) has been shown to be a putative suppressor of the early hematogenous dissemination of tumor cells to the bone marrow in breast cancer. Here, we investigated the associations of RAI2 mRNA and protein expression with clinicopathological factors and prognosis in breast cancer patients with long-term follow-up. Invasive breast cancer tissues (n = 604) were analyzed for RAI2 mRNA expression. We examined the associations of clinicopathological factors with the expression levels of RAI2 mRNA in these samples. We also analyzed RAI2 protein expression by immunohistochemistry in invasive breast cancer tissues (n = 422). We identified significant positive associations between low expression of RAI2 mRNA and shorter disease-free survival (DFS), breast-cancer-specific survival (BCSS), and overall survival (OS) in breast cancer patients. We also identified significant positive associations between negative for RAI2 protein expression and shorter DFS, BCSS, and OS in breast cancer patients. Low RAI2 mRNA and negative for RAI2 protein expression were positively associated with larger tumor size, higher tumor grade, and ERα-negativity. Multivariate analyses indicated that not only RAI2 mRNA but also RAI2 protein expression were independent risk factors for both DFS and BCSS in breast cancer patients. The median follow-up periods were 10.3 and 9.3years for the RAI2 mRNA and protein expression analyses, respectively. Our findings suggest that RAI2 has a role in the metastasis of breast cancer, and that RAI2 expression could be a promising candidate biomarker of prognosis in breast cancer patients.

Cofilin-1, LIMK1 and SSH1 are differentially expressed in locally advanced colorectal cancer and according to consensus molecular subtypes

BackgroundColorectal cancer (CRC) is among the deadliest cancers, wherein early dissemination of tumor cells, and consequently, metastasis formation, are the main causes of mortality and poor prognosis. Cofilin-1 (CFL-1) and its modulators, LIMK1/SSH1, play key roles in mediating the invasiveness by driving actin cytoskeleton reorganization in various cancer types. However, their clinical significance and prognostic value in CRC has not been fully explored. Here, we evaluated the clinical contribution of these actin regulators according to TNM and consensus molecular subtypes (CMSs) classification.MethodsCFL-1, LIMK1 and SSH1 mRNA/protein levels were assessed by real-time PCR and immunohistochemical analyses using normal adjacent and tumor tissues obtained from a clinical cohort of CRC patients. The expression levels of these proteins were associated with clinicopathological features by using the chi square test. In addition, using RNA-Seq data of CRC patients from The Cancer Genome Atlas (TCGA) database, we determine how these actin regulators are expressed and distributed according to TNM and CMSs classification. Based on gene expression profiling, Kaplan–Meier survival analysis was used to evaluated overall survival.ResultsBioinformatic analysis revealed that LIMK1 expression was upregulated in all tumor stages. Patients with high levels of LIMK1 demonstrated significantly lower overall survival rates and exhibited greater lymph node metastatic potential in a clinical cohort. In contrast, CFL-1 and SSH1 have expression downregulated in all tumor stages. However, immunohistochemical analyses showed that patients with high protein levels of CFL-1 and SSH1 exhibited greater lymph node metastatic potential and greater depth of local invasion. In addition, using the CMSs classification to evaluate different biological phenotypes of CRC, we observed that LIMK1 and SSH1 genes are upregulated in immune (CMS1) and mesenchymal (CMS4) subtypes. However, patients with high levels of LIMK1 also demonstrated significantly lower overall survival rates in canonical (CMS2), and metabolic (CMS3) subtypes.ConclusionsWe demonstrated that CFL-1 and its modulators, LIMK1/SSH1, are differentially expressed and associated with lymph node metastasis in CRC. Finally, this expression profile may be useful to predict patients with aggressive signatures, particularly, the immune and mesenchymal subtypes of CRC.

Abstract 1150: Targeting PI3K inhibits ER-mammary tumor initiation and early dissemination

Abstract Despite recent advances in cancer treatment, including targeted therapies and immunotherapies, many women still die of breast cancer. To ultimately reduce breast cancer death, it is of urgent need to develop more effective prevention and early intervention strategies. Although tamoxifen and aromatase inhibitors decrease incidences of estrogen receptor positive (ER+) breast cancer, there is no effective agent for prevention of ER negative (ER-) breast cancer. In this study, we identified that PI3K pathway is significantly activated in premalignant ER- breast lesions compared to paired normal tissue from breast cancer patients. We therefore tested whether blocking PI3K pathway by genetic knockdown or using a clinically applicable PI3K inhibitor (GDC0941) can inhibit ER- tumor initiation and progression. Indeed, both genetic knockdown of PI3K and low dose GDC0941 intervention reversed the disorganized three-dimensional growth of semi-transformed human ER- mammary epithelial cells in vitro. More importantly, low dose GDC0941 treatment significantly delayed the tumor initiation in MMTV-neu mouse model which develops ER-HER2+ mammary tumors. Notably, low dose GDC0941 treatment did not show discernable adverse effects, including no significant changes in body weight and liver functions, no immuno-toxicity. Since PI3K activation is crucial for early disseminated tumor cells, we collected bone marrow from treated mice versus vehicle control group, and examined the impact of GDC0941 treatment on early dissemination of tumor cells into the bone marrow. Excitingly, we found that administration of low dose GDC0941 significantly decreased CD45-ErBb2+/CK8/18+ early disseminated mammary tumor cells into the bone marrow, indicating that low dose PI3K inhibitor not only delayed primary tumor initiation but also prevented tumor cell early dissemination in the bone marrow. Taken together, these data support the notion that using low dose targeting drug to block PI3K pathway is safe and promising for ER- breast cancer prevention. Citation Format: Yuan Zhang, Jingyang Wang, Yi Xiao, Victoria Seewaldt, Dihua Yu. Targeting PI3K inhibits ER-mammary tumor initiation and early dissemination [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1150.

Abstract 1078: An immunosuppressive signature in bone marrow as a potential biomarker for recurrence of metastatic prostate cancer after prostatectomy

Abstract Background: Metastatic prostate cancer is the second leading cause of cancer-related deaths in US men. Nearly one-third of men develop recurrence after curative intent treatment. Bone metastases are common, and cause significant morbidity in addition to driving mortality rates. Early dissemination of tumor cells to the bone marrow has been hypothesized as a contributing factor to recurrence. However, the factors that promote early dissemination and survival in the bone microenvironment are not clearly elucidated. Key components of immune regulation such as cytotoxic T cells and regulatory T cells can regulate growth of cancer cell lines and in mouse models. We hypothesize that an immunosuppressive signature results in a permissive environment allowing the growth of disseminated prostate cancer cells. Therefore, the goal of our project is to evaluate mechanisms of immune evasion that promote the development of metastatic prostate cancer. Methods: Matched blood and bone marrow aspirates were collected from patients undergoing prostatectomy. Samples from five healthy donors were collected to establish a normal baseline. Using multicolor flow cytometry, samples were subjected to multi-parameter panels designed to assess the composition and function of lymphoid and myeloid immune compartments. These panels include markers of known immune subtypes, co-stimulatory signals, and activation signals. Results were analyzed with Prism software. Results: Preliminary results show variable T cell to B cell ratios ranging from as low as 1:1 to as high as 9:1. A high CD4 to CD8 T cell ratio was identified in 38% of samples, which corresponded with a higher occurrence of regulatory T cells. These data are consistent with an immunosuppressed bone marrow signature, which importantly was not present in the matched peripheral blood samples. Furthermore, our preliminary data demonstrates altered lymphoid and myeloid subsets in patients with prostate cancer as compared to healthy donors. Discussion: Overall, these results support the hypothesis that an immunosuppressive signature in bone marrow may promote survival of disseminated prostate cancer cells by protecting them from immune eradication. Furthermore, this immune signature within the microenvironment may exist at the time of prostatectomy and can be correlated with clinical biomarkers to identify factors that promote dissemination and metastatic recurrence. Future work involves using descriptive statistics to correlate the immune signatures identified in this project with patient outcomes, including PSA, Gleason grade, recurrence rates and time to recurrence. Ultimately, the goal is to identify an immune signature that accurately predicts risk of developing recurrent prostate cancer, potentially serving as a biomarker for patients that would benefit from aggressive upfront adjuvant systemic therapy. Citation Format: Nan Sethakorn, Erika Heninger, Jamie M. Sperger, Kenneth J. Pienta, Joshua M. Lang. An immunosuppressive signature in bone marrow as a potential biomarker for recurrence of metastatic prostate cancer after prostatectomy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1078.

Abstract 4580: Primary tumor-induced immunity eradicates disseminated tumor cells in syngeneic mouse model

Abstract Although clinically apparent metastasis is associated with late stages of cancer development, micro-metastatic dissemination may be an early event. However, the fate of these early disseminated tumor cells (DTC) remains elusive. Using the syngeneic mouse models, we demonstrated that although both orthotopically-implanted murine 4T1 and EMT6 tumors are capable of disseminating into secondary organs, only 4T1 tumors develop overt metastasis. However, EMT6 tumors induce an anti-tumor immunity in syngeneic mice and that eradicates disseminated tumor cells (DTC) in distant organs. Following the complete removal of primary EMT6 tumors, mice do not develop detectable metastasis and generate an immunological memory that leads to complete elimination of repeatedly injected tumor cells via tail vein. Conversely, these cells readily grow and metastasize in immuno-deficient athymic or Rag2- mice, and when g-MDSCs from 4T1 tumor-bearing mice were co-injected into immunocompetent EMT6 primed mice. In contrast to complete resection, mice with residual tumors following surgery exhibited an enhanced growth of local and concomitant growth of DTCs at metastatic site with increased g-MDSCs accumulation in lung and spleen. Together, our results suggest that some tumors are capable of inducing anti-tumor immunity against the DTCs when complete resection of primary tumor cures animals. However, in the presence of residual tumors, inflammation induced by surgical procedure promote the growth of DTCs. Citation Format: Raziye Piranlioglu, Eunmi Lee, Maria Ouzuonova, Riley Rodier, Adam Greer, Feyzanur Bayraktar, Omer Can Durmus, Ali S. Arbab, Muthushamy Thangaraju, Max S. Wicha, Esteban Celis, Hasan Korkaya. Primary tumor-induced immunity eradicates disseminated tumor cells in syngeneic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4580.

Primary tumor-induced immunity eradicates disseminated tumor cells in syngeneic mouse model

Although clinically apparent metastasis is associated with late stages of cancer development, micro-metastatic dissemination may be an early event. However, the fate of these early disseminated tumor cells (DTC) remains elusive. We show that despite their capacity to disseminate into secondary organs, 4T1 tumor models develop overt metastasis while EMT6-tumor bearing mice clear DTCs shed from primary tumors as well as those introduced by intravenous (IV) injection. Following the surgical resection of primary EMT6 tumors, mice do not develop detectable metastasis and reject IV-injected tumor cells. In contrast, these cells readily grow and metastasize in immuno-deficient athymic or Rag2−/− mice, an effect mimicked by CD8+ T-cell depletion in immunocompetent mice. Furthermore, recombinant G-CSF or adoptive transfer of granulocytic-MDSCs isolated from 4T1 tumor-bearing mice, induce metastasis by suppressing CD8+ T-cells in EMT6-primed mice. Our studies support the concept of immune surveillance providing molecular insights into the immune mechanisms during tumor progression.

Abstract P3-08-11: The prognostic impact of retinoic acid-induced 2 (RAI2) expression in ERα-positive breast cancer patients

Abstract Background: Breast cancer cells disseminate to the bone marrow and form bone metastases in a large majority of late-stage patients. Retinoic Acid-Induced 2 (RAI2) was reported as a putative suppressor of early hematogenous dissemination of tumor cells to the bone marrow in breast cancer, particularly in estrogen receptor α (ERα)-positive breast cancer. Here, we investigated mRNA expression of RAI-2 in breast cancer patients during long-term follow-up. Materials and methods: A total of 451 invasive breast cancer tissues was available for analysis of RAI2 mRNA using a TaqMan PCR system. We also sought correlations between clinicopathological factors and levels of RAI2 expression in these samples. The expression of markers associated with tumor-initiating capacity, such as SNAI1, SNAI2 and VIM was also analyzed. The median follow-up period was 9.0 years. Survival curves were analyzed using the Kaplan-Meier method. Cox proportional hazards regression analysis was used for univariate and multivariate analyses of prognostic values. Results: We found positive correlations between low expression of RAI2 mRNA and shorter disease-free survival and overall survival in breast cancer patients (P=0.003, P<0.0001, respectively), which was limited to ERα-positive patients (P=0.04, P=0.0009, respectively), and not seen in ERα-negative patients (P=0.52, P=0.27, respectively). Low RAI2 mRNA levels were positively correlated with high grade, ERα-negativity and PgR negativity. Multivariate analysis indicated that low level RAI2 mRNA expression was an independent factor for survival both overall in breast cancer and in ERα-positive breast cancer patients Multivariate analysis (ERα-positive breast cancer patients) OS Multivariate patientsp valueHR(95%CI)Tumor size≤2cm1390.83691 (Reference) >2cm207 1.08(0.54-2.28)Node statusNegative176<0.00011 (Reference) Positive144 4.72(2.33-10.34)Grade11240.95921 (Reference) 2•3218 0.98(0.50-2.14)RAI2 mRNA expressionhigh140<0.00011 (Reference) middle•low206 4.79(2.14-12.78) . Conclusion:We show that low expression of RAI2 is an independent factor predictive of a poor prognosis in ERα-positive breast cancer patients. RAI2 could be a promising candidate biomarker and therapeutic target in ERα-positive breast cancer to prevent dissemination to the bone marrow. Citation Format: Nishikawa S, Kondo N, Endo Y, Hato Y, Hisada T, Nishimoto M, Dong Y, Okuda K, Kato H, Takahashi S, Nakanishi R, Toyama T. The prognostic impact of retinoic acid-induced 2 (RAI2) expression in ERα-positive breast cancer patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-08-11.

Abstract 5807: Disseminated tumor cell clearance by the immune system

Abstract The classical model of metastasis suggests that the tumor cell dissemination occurs late in tumor development, however accumulating evidence coming from mouse studies and clinical data provide striking evidence that tumor cells start to disseminate during the initial steps of tumor development. However, the dissemination from the primary area does not always result in metastasis. Due to the non-permissive nature of microenvironment in distant sites, these early disseminated tumor cells might be cleared or maintained in a non-proliferative/dormant state. The mechanism by which some early disseminated tumor cells colonize and generate metastatic growth while some remain dormant is not well known. In order to understand the underlying factors that may contribute to the metastatic growth, we performed time course experiments by utilizing murine mammary tumors (4T1 as metastatic and EMT6 as less metastatic) in a syngeneic mouse model. Luciferase expressing 4T1 or EMT6 tumor cells were orthotopically implanted into the fat pads and tumor cell dissemination was analyzed over 3-week time points. We determined that both 4T1 and EMT tumors disseminated as early as one to two-week post implantation, however only 4T1 tumor develop metastasis in distant organs. Moreover, we also resected primary tumors 1, 2 and 3-week post implantation of EMT6-Luci or 4T1-Luci tumors and observed distant metastasis via optical imaging of luciferase expression in live animals. Although the majority of 4T1 tumor-bearing mice (>80%) develop pulmonary metastasis when 4T1 tumors resected 2 and 3 weeks post-implantation only 10% of mice develop metastasis when primary tumor resected one-week post implantation. In contrast, EMT6 tumors following resection only relapsed in the primary tumor site but failed to develop metastasis. Furthermore, EMT6 tumor-bearing mice efficiently cleared tail vein injected EMT6-luci cells in the lungs. We investigated the possible mechanism by which EMT6 tumor-bearing mice clears disseminated tumor cells in the lung. We provide evidence that pulmonary infiltrated mMDSCs mediate tumor cell killing via secretion of high levels of cytotoxic granules, granzyme A, granzyme B, perforin. This was confirmed by mouse transcriptome and qPCR analyses as well as biochemistry using in vivo samples and in vitro co-culture samples. Our studies provide a new paradigm in the understanding of the fate of disseminated tumor cells in secondary organs and the role of the immune system in this process. Citation Format: Raziye Piranlioglu, Eun Mi Lee, Maria Ouzunova, Ali S. Arbab, Paulo C. Rodriguez, Asm L. Iskander, Hasan Korkaya. Disseminated tumor cell clearance by the immune system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5807. doi:10.1158/1538-7445.AM2017-5807

Circulating tumor cells in patients with advanced urothelial carcinoma of the bladder: Association with tumor stage, lymph node metastases, FDG-PET findings, and survival

BackgroundThere are currently no methods in clinical use that can detect early systemic dissemination of urothelial tumor cells. ObjectiveTo evaluate measurement of circulating tumor cells (CTCs) as a biomarker for disseminated disease in patients with advanced bladder cancer. Design, setting, and participantsBetween March 2013 and October 2015, 88 patients were prospectively included in the study: 78 were scheduled for radical cystectomy (RC) ± perioperative chemotherapy and 10 treated with palliative chemotherapy. The CellSearch CTC test was further assessed in this context by investigating expression of epithelial cell adhesion molecule (EpCAM) in primary tumors obtained at cystectomy from an independent cohort of 409 patients. Outcome measurements and statistical analysisPresence of CTCs was tested for association with tumor stage, lymph node metastases, metastatic disease on [18 F]-fluorodeoxyglucose-positron emission tomography (FDG-PET), and cancer-specific and progression-free survival. ResultsCTCs were detected in 17/88 patients (19%). In 61 patients who underwent FDG-PET-computed tomography (CT), a statistically significant association with presence of CTCs was found for radiological metastatic disease but not for normal PET-CT results (12/35 [34%] vs. 2/26 [8%], P = 0.014). After a median follow-up time of 16.5 months (95% CI: 9.6–21.4), presence of CTCs was associated with an increased risk of progression among patients treated with RC with or without perioperative chemotherapy (n = 75, P = 0.049). A multivariate analysis adjusted for clinical tumor stage, clinical lymph node status, and age showed that CTCs were an independent marker of progression (n = 75; hazard ratio = 2.78; 95% CI: 1.005–7.69; P = 0.049) but not of cancer-specific death (P = 0.596). In 409 cystectomised patients, more than 392 (96%) of the bladder tumors expressed EpCAM. ConclusionsCTCs were present in 19% of patients with advanced urothelial tumors and were associated with metastatic disease on FDG-PET-CT and with increased risk of disease progression after RC. A significant portion of urothelial cancer cells do express EpCAM and can thus be identified using EpCAM-antigen–based CTC detection methods.

Mechanisms governing metastatic dormancy in breast cancer.

Breast cancer is a systemic disease characterized by early dissemination of tumor cells to distant organs. In this foreign environment, tumor cells may stay in a dormant state as single cells or as micrometastases for many years before growing out into a macrometastatic lesion. As metastasis is the primary cause for breast cancer-related death, it is important to understand the mechanisms underlying the maintenance of dormancy and dormancy escape to find druggable targets to eradicate metastatic tumor cells. Metastatic dormancy is regulated by complex interactions between tumor cells and the local microenvironment. In addition, cancer-directed immunity and systemic instigation play a crucial role.

Abstract 908: Immune regulation of tumor dormancy in syngeneic mouse model

Abstract Metastatic disease -end stage of tumor progression- is the major cause of cancer-related death.It is widely accepted that malignant cell plasticity between epithelial-mesenchymal-transition (EMT) and mesenchymal-epithelial-transition (MET) is required for metastasis to occur. The classical model of metastasis suggests tumor cell dissemination occur late in tumor development, however emerging studies strongly indicates that dissemination is an early process and provide a striking evidence that tumor cells start to disseminate during the initial steps of tumor development. Late appearing metastases arise from these early-disseminated tumor cells. The mechanism by which some early-disseminated tumor cells colonize and generate metastatic growth while some remain dormant is not well known. In order to understand the underlying factors, we utilized murine mammary tumors (4T1 as metastatic and EMT6 as less metastatic) in a syngeneic mouse model. We performed time course experiments to determine the early factors that may contribute to the metastatic growth. 4T1 or EMT6 tumor cells were implanted orthotopically into the fat pads and tumor cell dissemination was analyzed over 3 weeks time points. We determined that both 4T1 and EMT tumor cells disseminated as early as one week post-implantation, however only 4T1 tumor cells develop metastasis in distant organs. Furthermore, we also resected primary tumors 1,2 and 3 week post implantation of EMT6-Luci or 4T1-Luci tumors and observed distant metastasis via optical imaging of luciferase expression in live animals. Although the majority of 4T1 tumor bearing mice (>80%) develop pulmonary metastasis when 4T1 tumors resected 2 and 3 weeks post-implantation, only 10% of mice develop metastasis when primary tumor resected one week post implantation. In contrast, EMT6 tumors following resection only relapsed in the primary tumor site but failed to develop metastasis. We investigated the possible mechanism of efficient pulmonary metastatic growth following the resection of tumors 2-3 week post implantation. Interestingly we found a significant infiltration of granulocytic subset of myeloid derived suppressor cells (g-MDSC) in 4T1 tumor bearing mice by week 2 and 3. Furthermore, we found that lung infiltrated g-MDSCs promote tumor cell growth via paracrine factors. In co-culture studies we found that there is a reciprocal secretion of panel of inflammatory cytokines, growth factors and matrix metalloproteases between tumor cell and g-MDSCs suggesting that these cells in the lung microenvironment support the metastatic growth. Our studies provide a new paradigm in the understanding of metastatic growth and the role of microenvironment in distant organs. Citation Format: Raziye Piranlioglu, Maria Ouzounova, Eunmi Lee, Alicia Hudson, Sumeyye Korkaya, Ali Arbab, Hasan Korkaya. Immune regulation of tumor dormancy in syngeneic mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 908.

A hypoxic signature marks tumors formed by disseminated tumor cells in the BALB-neuT mammary cancer model.

Metastasis is the final stage of cancer progression. Some evidence indicates that tumor cell dissemination occurs early in the natural history of cancer progression. Disseminated tumor cells (DTC) have been described in the bone marrow (BM) of cancer patients as well as in experimental models, where they correlate with later development of metastasis. However, little is known about the tumorigenic features of DTC obtained at different time points along tumor progression. Here, we found that early DTC isolated from BM of 15-17 week-old Her2/neu transgenic (BALB-neuT) mice were not tumorigenic in immunodeficient mice. In contrast, DTC-derived tumors were easily detectable when late DTC obtained from 19-22 week-old BALB-neuT mice were injected. Angiogenesis, which contributes to regulate tumor dormancy, appeared dispensable to reactivate late DTC, although it accelerated growth of secondary DTC tumors. Compared with parental mammary tumors, gene expression profiling disclosed a distinctive transcriptional signature of late DTC tumors which was enriched for hypoxia-related transcripts and was maintained in ex-vivo cell culture. Altogether, these findings highlight a different tumorigenic potential of early and late DTC in the BALB-neuT model and describe a HIF-1α-related transcriptional signature in DTC tumors, which may render DTC angiogenesis-competent, when placed in a favourable environment.

Disseminated and circulating tumor cells in bone marrow and blood of breast cancer patients: properties, enrichment, and potential targets.

From the early days of pathology back in the nineteenth century until now, there has been an ongoing search for the missing link between solid tumors such as breast cancer and distant metastases, which sometimes occur many years after removal of the primary tumor. The "seed and soil" theory hypothesizes the early dissemination of occult tumor cells into blood or bone marrow, which can persist in a dormant state for a long time and then become precursors of metastases in distant organs which offer appropriate conditions. Advances in immunocytochemical methods have enabled the enrichment and visualization of those disseminated tumor cells in bone marrow (DTC-BM) or circulating tumor cells (CTC) in blood. Many studies could demonstrate prognostic significance of the detection of DTC-BM or CTC in different stages of breast cancer. Further characterization of those cells by immunocytochemical stainings, fluorescence in situ hybridizations, or PCR-based molecular methods will help to understand the biology of tumor cell dissemination and metastasis formation, as well as to define potential drug targets.

Suppression of early hematogenous dissemination of human breast cancer cells to bone marrow by retinoic Acid-induced 2.

Regulatory pathways that drive early hematogenous dissemination of tumor cells are insufficiently defined. Here, we used the presence of disseminated tumor cells (DTC) in the bone marrow to define patients with early disseminated breast cancer and identified low retinoic acid-induced 2 (RAI2) expression to be significantly associated with DTC status. Low RAI2 expression was also shown to be an independent poor prognostic factor in 10 different cancer datasets. Depletion of RAI2 protein in luminal breast cancer cell lines resulted in dedifferentiation marked by downregulation of ERα, FOXA1, and GATA3, together with increased invasiveness and activation of AKT signaling. Functional analysis of the previously uncharacterized RAI2 protein revealed molecular interaction with CtBP transcriptional regulators and an overlapping function in controlling the expression of a number of key target genes involved in breast cancer. These results suggest that RAI2 is a new metastasis-associated protein that sustains differentiation of luminal breast epithelial cells. We identified downregulation of RAI2 as a novel metastasis-associated genetic alteration especially associated with early occurring bone metastasis in ERα-positive breast tumors. We specified the role of the RAI2 protein to function as a transcriptional regulator that controls the expression of several key regulators of breast epithelial integrity and cancer.