Summer Cancer Research Experience for High School Students from Historically Marginalized Populations in Kansas City

The Accelerate Cancer Education (ACE) summer research program at The University of Kansas Cancer Center (KUCC) is a six-week, cancer-focused, summer research experience for high school students from historically marginalized populations in the Kansas City metropolitan area. Cancer affects all populations and continues to be the second leading cause of death in the United States, and a large number of disparities impact racial and ethnic minorities, including increased cancer incidence and mortality. Critically, strategies to bolster diversity, equity, inclusion, and accessibility are needed to address persistent cancer disparities. The ACE program offers an educational opportunity for a population of students who otherwise would not have easy access onto a medical center campus to make connections with cancer physicians and researchers and provides a vital response to the need for a more diverse and expansive oncology workforce. Students grow their technical, social, and professional skills and develop self-efficacy and long-lasting connections that help them matriculate and persist through post-secondary education. Developed in 2018, the ACE program has trained 37 high school junior and senior students. This article describes the need for and how we successfully developed and implemented the ACE program.

A community engagement training program for basic and translational cancer researchers

PURPOSE

There is an increasing awareness of the importance of patient engagement in cancer research, but many basic and translational researchers have never been trained to do so. To address this unmet need, a 1-year patient engagement training program for researchers was developed.

METHODS

Eleven researchers and eleven paired research advocates participated. This program, designed for virtual delivery, included 3 didactic modules focused on (1) Community Outreach and Engagement principles and methods, (2) Communication skills, and (3) Team Science. This was followed by longitudinal projects to be completed by the researcher/advocate pairs, including learning about the research project, and co-authoring abstracts, manuscripts and grant proposals. Monthly group meetings allowed pairs to share their experiences. The program culminated in the pairs creating and presenting oral abstracts for the University of Kansas Cancer Center's Annual Research Symposium.

RESULTS

All participants indicated that the modules had a positive impact on their ability to collaborate in research. Both researcher self-evaluations and patient advocate evaluations of their researcher partner showed an improvement in researcher communication competency. Results from the Patient Engagement in Research Scale showed that advocates were highly engaged. Within 1 year after program completion, participating pairs have completed four abstracts and 9 grant proposals.

CONCLUSION

The program will be modified based on participant feedback, and can be adapted for future cohorts if an increased number of sessions per month and shortened program duration are desired. The program's virtual format allows scalability across institutions to potentially benefit large cohorts of researchers.

Understanding the need for digital twins' data in patient advocacy and forecasting oncology

Digital twins are made of a real-world component where data is measured and a virtual component where those measurements are used to parameterize computational models. There is growing interest in applying digital twins-based approaches to optimize personalized treatment plans and improve health outcomes. The integration of artificial intelligence is critical in this process, as it enables the development of sophisticated disease models that can accurately predict patient response to therapeutic interventions. There is a unique and equally important application of AI to the real-world component of a digital twin when it is applied to medical interventions. The patient can only be treated once, and therefore, we must turn to the experience and outcomes of previously treated patients for validation and optimization of the computational predictions. The physical component of a digital twins instead must utilize a compilation of available data from previously treated cancer patients whose characteristics (genetics, tumor type, lifestyle, etc.) closely parallel those of a newly diagnosed cancer patient for the purpose of predicting outcomes, stratifying treatment options, predicting responses to treatment and/or adverse events. These tasks include the development of robust data collection methods, ensuring data availability, creating precise and dependable models, and establishing ethical guidelines for the use and sharing of data. To successfully implement digital twin technology in clinical care, it is crucial to gather data that accurately reflects the variety of diseases and the diversity of the population.

Functional inhibition of the RNA-binding protein HuR sensitizes triple-negative breast cancer to chemotherapy

Chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC); however, chemoresistance compromises its efficacy. The RNA-binding protein Hu antigen R (HuR) could be a potential therapeutic target to enhance the chemotherapy efficacy. HuR is known to mainly stabilize its target mRNAs, and/or promote the translation of encoded proteins, which are implicated in multiple cancer hallmarks, including chemoresistance. In this study, a docetaxel-resistant cell subline (231-TR) was established from the human TNBC cell line MDA-MB-231. Both the parental and resistant cell lines exhibited similar sensitivity to the small molecule functional inhibitor of HuR, KH-3. Docetaxel and KH-3 combination therapy synergistically inhibited cell proliferation in TNBC cells and tumor growth in three animal models. KH-3 downregulated the expression levels of HuR targets (e.g., β-Catenin and BCL2) in a time- and dose-dependent manner. Moreover, KH-3 restored docetaxel's effects on activating Caspase-3 and cleaving PARP in 231-TR cells, induced apoptotic cell death, and caused S-phase cell cycle arrest. Together, our findings suggest that HuR is a critical mediator of docetaxel resistance and provide a rationale for combining HuR inhibitors and chemotherapeutic agents to enhance chemotherapy efficacy.

Career disruption and limitation of financial earnings due to cancer

PURPOSE

This study investigated how cancer diagnosis and treatment lead to career disruption and, consequently, loss of income and depletion of savings.

DESIGN

This study followed a qualitative descriptive design that allowed us to understand the characteristics and trends of the participants.

METHOD

Patients recruited (n = 20) for this study were part of the University of Kansas Cancer Center patient advocacy research group (Patient and Investigator Voices Organizing Together). The inclusion criteria were that participants must be cancer survivors or co-survivors, be aged 18 years or older, be either employed or a student at the time of cancer diagnosis, have completed their cancer treatment, and be in remission. The responses were transcribed and coded inductively to identify themes. A thematic network was constructed based on those themes, allowing us to explore and describe the intricacies of the various themes and their impacts.

RESULTS

Most patients had to quit their jobs or take extended absences from work to handle treatment challenges. Patients employed by the same employer for longer durations had the most flexibility to balance their time between cancer treatment and work. Essential, actionable items suggested by the cancer survivors included disseminating information about coping with financial burdens and ensuring that a nurse and financial navigator were assigned to every cancer patient.

CONCLUSIONS

Career disruption is common among cancer patients, and the financial burden due to their career trajectory is irreparable. The financial burden is more prominent in younger cancer patients and creates a cascading effect that financially affects close family members.

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.

Abstract P1-13-08: Inhibition of RNA binding protein HuR function sensitizes the TNBC to chemotherapy

The 5-year relative survival rate for triple-negative breast cancer (TNBC) is 77%, which is notably lower than 90%, the overall survival rate for breast cancer. The primary systemic treatment for TNBC remains to be chemotherapy. However, patients frequently develop resistance to conventional chemotherapy, greatly compromising the anti-tumor effects of chemodrugs. Therefore, this study is aimed to enhance the effects of chemotherapy. The RNA-binding protein Hu antigen R (HuR) plays an important role in chemotherapy resistance. HuR post-transcriptionally regulates the stability of the target mRNA by binding to the U- or AU-rich elements (ARE) mainly in the 3’ untranslated region (UTR) of mRNA. In most cases, the binding stabilizes mRNA, thereby enhancing the translation of the encoded protein, many of which are implicated in multiple cancer hallmarks, including chemoresistance. The overexpression of HuR, and accumulated cytoplasmic expression, are reported to be related to chemoresistance in many types of cancer cells. We hypothesized that inhibition of HuR function by disrupting its interaction with mRNA can accelerate the decay of mRNA and thus reduce the translation of proteins contributing to chemoresistance. Previously, our lab reported a small molecule HuR inhibitor, KH-3, which potently inhibits HuR function by disrupting the HuR-mRNA interactions. To test our hypothesis, we utilized KH-3 as a tool compound to assess whether HuR inhibition enhances the efficacy of chemotherapy for TNBC cells. We generated a cell sub-line (231-TR) derived from the human TNBC cell line MDA-MB-231 with acquired resistance against docetaxel (TXT). Compared with the parental cell line, 231-TR exhibited similar sensitivity to KH-3 in the MTT-based cytotoxicity assay and the colony formation assay. The in vitro and in vivo combination of KH-3 and TXT synergized in inhibiting cell proliferation and tumor growth of multiple TNBC cell lines. Regarding mechanisms of action, the apoptosis pathway was downregulated and the Wnt signaling pathway was upregulated in 231-TR cells. KH-3 treatment downregulated β-Catenin, involved in promoting cell proliferation, in a time and dose-dependent manner. KH-3 was also identified to induce apoptosis cell death via inhibiting the anti-apoptotic protein BCL2. The cell cycle analysis revealed that KH-3 treatment caused the S phase accumulation. Therefore, the cell proliferation inhibition by KH-3 results from a combination of apoptosis and cell cycle arrest. Furtherly, KH-3 restored the effects of docetaxel in inducing apoptotic cell death in 231-TR cells. Together, this study provides a new strategy to overcome chemotherapy resistance in TNBC cells by functional inhibiting HuR.

Citation Format: Lanjing Wei, Qi Zhang, Cuncong Zhong, Jeffrey Aubé, Danny R. Welch, Xiaoqing Wu, Liang Xu. Inhibition of RNA binding protein HuR function sensitizes the TNBC to chemotherapy [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 P1-13-08.

Abstract IA007: Regulation of metastasis efficiency via mitochondrial genetics

While there has been increasing appreciation for the roles of mitochondria in cancer, most efforts investigating the genetics of cellular functions study only the nuclear genome. To overcome technical complications of studying the specific contributions of mitochondrial genetics, we created mitochondrial nuclear exchange (MNX) mice by transferring an oocyte nucleus from strain-x into an enucleated oocyte from strain-y. Using MNX mice, we made the following discoveries demonstrating the profound role(s) of mtDNA on several complex phenotypes. - Crossing nuclear genome-matched female mice with male transgenic mice bearing oncogenes, tumorigenicity and metastasis were up- or down-regulated depending upon mtDNA. - MNX mice exhibit different autochthonous tumor formation. - When syngeneic (i.e., histocompatible) mammary and melanoma cells were injected into MNX mice, metastasis changed 3-5X, depending on mtDNA SNP. C57BL/6J mtDNA inhibited metastasis while C3H/HeN mtDNA increased metastasis. - MNX mice have selectively altered epigenetic marks (DNA methylation and histone marks) in the nuclear genome. - MNX mice with higher ROS form more metastases. Scavenging ROS reduced metastasis. - Baseline immune profiles differ in MNX mice compared to nDNA-matched counterparts and polarization states of myeloid populations infiltrating lung metastases were also significantly different. - Metabolomic profiling of >5000 metabolites showed minor differences, none of which appear to correlate with the above-referenced phenotypic changes. - MNX mice have distinct gut microbiota than matched wild-type strains, suggesting mitochondrial-bacterial communication. Together, these results demonstrate that mitochondrial genes are among metastatic quantitative trait loci by intrinsic and extrinsic mechanisms. Candidate signals from mitochondria to the nucleus or bacteria will be reported. And since mitochondrial SNP are markers of genetic ancestry, our findings also suggest that mtDNA SNP could serve as prognostic biomarkers and partially explain racial disparities in disease severity. Support: Susan G. Komen for the Cure (SAC11037), METAvivor Research & Support Inc., National Foundation for Cancer Research, National Cancer Institute P30-CA168524.

Citation Format: Danny R. Welch. Regulation of metastasis efficiency via mitochondrial genetics [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 IA007.

Generating Mitochondrial-Nuclear Exchange (MNX) Mice to Identify Mitochondrial Determinants of Cancer Metastasis

Understanding the contributions of mitochondrial genetics to disease pathogenesis is facilitated by a new and unique model-the mitochondrial-nuclear exchange mouse. Here we report the rationale for their development, the methods used to create them, and a brief summary of how MNX mice have been used to understand the contributions of mitochondrial DNA in multiple diseases, focusing on cancer metastasis. Polymorphisms in mtDNA which distinguish mouse strains exert intrinsic and extrinsic effects on metastasis efficiency by altering epigenetic marks in the nuclear genome, changing production of reactive oxygen species, altering the microbiota, and influencing immune responses to cancer cells. Although the focus of this report is cancer metastasis, MNX mice have proven to be valuable in studying mitochondrial contributions to other diseases as well.

Roles of mitochondrial genetics in cancer metastasis

The contributions of mitochondria to cancer have been recognized for decades. However, the focus on the metabolic role of mitochondria and the diminutive size of the mitochondrial genome compared to the nuclear genome have hindered discovery of the roles of mitochondrial genetics in cancer. This review summarizes recent data demonstrating the contributions of mitochondrial DNA (mtDNA) copy-number variants (CNVs), somatic mutations, and germline polymorphisms to cancer initiation, progression, and metastasis. The goal is to summarize accumulating data to establish a framework for exploring the contributions of mtDNA to neoplasia and metastasis.

Questions to guide cancer evolution as a framework for furthering progress in cancer research and sustainable patient outcomes

We appear to be faced with ‘two truths’ in cancer—one of major advances and successes and another one of remaining short-comings and significant challenges. Despite decades of research and substantial progress in treating cancer, most patients with metastatic cancer still experience great suffering and poor outcomes. Metastatic cancer, for the vast majority of patients, remains incurable. In the context of advanced disease, many clinical trials report only incremental advances in progression-free and overall survival. At the same time, the breadth and depth of new scientific discoveries in cancer research are staggering. These discoveries are providing increasing mechanistic detail into the inner workings of normal and cancer cells, as well as into cancer–host interactions; however, progress remains frustratingly slow in translating these discoveries into improved diagnostic, prognostic, and therapeutic interventions. Despite enormous advances in cancer research and progress in progression-free survival, or even cures, for certain cancer types—with earlier detection followed by surgical, adjuvant, targeted, or immuno- therapies, we must challenge ourselves to do even better where patients do not respond or experience evolving therapy resistance. We propose that defining cancer evolution as a separate domain of study and integrating the concept of evolvability as a core hallmark of cancer can help position scientific discoveries into a framework that can be more effectively harnessed to improve cancer detection and therapy outcomes and to eventually decrease cancer lethality. In this perspective, we present key questions and suggested areas of study that must be considered—not only by the field of cancer evolution, but by all investigators researching, diagnosing, and treating cancer.

Abstract 1780: Functional inhibition of RNA-binding protein HuR reverses chemotherapeutic resistance in triple-negative breast cancer

The 5-year relative survival rate of patients with triple-negative breast cancer (TNBC) is lower than the overall patients with breast cancer. The primary systemic treatment for TNBC remains to be chemotherapy. But chemoresistance frequently develops with the conventional usage of chemotherapy drugs, which results in poorer prognosis and higher recurrence of TNBC than other subtypes of breast cancer. Therefore, to improve the treatment for TNBC, overcoming chemoresistance is a critical challenge to conquer. The RNA-binding protein Hu antigen R (HuR) is a posttranscriptional regulator. It can stabilize target mRNAs through binding to U- or AU- rich elements mainly in 3’ untranslated region (UTR) of mRNA and upregulate their translation level in most cases. The encoded proteins of HuR target mRNAs are implicated in multiple cancer hallmarks, including chemotherapeutic sensitivity. The cytoplasmic accumulation of HuR is reported to contribute to chemoresistance in multiple cancer cells, and HuR inhibition sensitizes cancer cells to chemodrugs. We hypothesize that inhibition of HuR function by disrupting its interaction with mRNA can accelerate the decay of target mRNAs and thus reduce the translation level of proteins responsible for chemoresistance. Recently, our lab identified a small molecule HuR inhibitor, KH-3, which potently inhibits HuR function by disrupting HuR-mRNA interactions. In this study, KH-3 is used as a tool compound to investigate the roles HuR plays in chemoresistance development and evaluate whether HuR inhibition can enhance the efficacy of chemotherapy for TNBC cells. Two MDA-MB-231 cell sublines resistant to docetaxel (231-TR) or doxorubicin (231-DR) were generated in our lab. Compared to the parental cell line, two sub-lines exhibit similar sensitivity to KH-3, and KH-3 re-sensitizes chemoresistant cells to docetaxel or doxorubicin in the MTT-based cytotoxicity assay and the colony formation assay, indicating that HuR inhibition can overcome the acquired chemoresistance. The in vivo efficacy studies in orthotopic xenograft mouse models of human TNBC confirm that KH-3 synergizes docetaxel treatment. Regarding to mechanisms of action, several HuR direct target mRNAs implicated in chemoresistance were found upregulated in the resistant cells, which were reversed by KH-3 treatment. Detailed molecular mechanisms are now under investigation. This study suggests that HuR inhibition is a promising strategy to overcome the challenge of chemoresistance of TNBC.

Citation Format: Lanjing Wei, Qi Zhang, Cuncong Zhong, Jeffrey Aubé, Danny R. Welch, Xiaoqing Wu, Liang Xu. Functional inhibition of RNA-binding protein HuR reverses chemotherapeutic resistance in triple-negative breast cancer [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 1780.

Synergistic anti-proliferative activity of JQ1 and GSK2801 in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) constitutes 10-20% of breast cancers and is challenging to treat due to a lack of effective targeted therapies. Previous studies in TNBC cell lines showed in vitro growth inhibition when JQ1 or GSK2801 were administered alone, and enhanced activity when co-administered. Given their respective mechanisms of actions, we hypothesized the combinatorial effect could be due to the target genes affected. Hence the target genes were characterized for their expression in the TNBC cell lines to prove the combinatorial effect of JQ1 and GSK2801.

METHODS

RNASeq data sets of TNBC cell lines (MDA-MB-231, HCC-1806 and SUM-159) were analyzed to identify the differentially expressed genes in single and combined treatments. The topmost downregulated genes were characterized for their downregulated expression in the TNBC cell lines treated with JQ1 and GSK2801 under different dose concentrations and combinations. The optimal lethal doses were determined by cytotoxicity assays. The inhibitory activity of the drugs was further characterized by molecular modelling studies.

RESULTS

Global expression profiling of TNBC cell lines using RNASeq revealed different expression patterns when JQ1 and GSK2801 were co-administered. Functional enrichment analyses identified several metabolic pathways (i.e., systemic lupus erythematosus, PI3K-Akt, TNF, JAK-STAT, IL-17, MAPK, Rap1 and signaling pathways) enriched with upregulated and downregulated genes when combined JQ1 and GSK2801 treatment was administered. RNASeq identified downregulation of PTPRC, MUC19, RNA5-8S5, KCNB1, RMRP, KISS1 and TAGLN (validated by RT-qPCR) and upregulation of GPR146, SCARA5, HIST2H4A, CDRT4, AQP3, MSH5-SAPCD1, SENP3-EIF4A1, CTAGE4 and RNASEK-C17orf49 when cells received both drugs. In addition to differential gene regulation, molecular modelling predicted binding of JQ1 and GSK2801 with PTPRC, MUC19, KCNB1, TAGLN and KISS1 proteins, adding another mechanism by which JQ1 and GSK2801 could elicit changes in metabolism and proliferation.

CONCLUSION

JQ1-GSK2801 synergistically inhibits proliferation and results in selective gene regulation. Besides suggesting that combinatorial use could be useful therapeutics for the treatment of TNBC, the findings provide a glimpse into potential mechanisms of action for this combination therapy approach.

Abstract P4-01-16: Overcome chemoresistance of triple-negative breast cancer by inhibiting the RNA-binding protein HuR

Chemotherapy remains the primary systemic treatment for triple-negative breast cancer (TNBC). However, patients with TNBC often develop resistance to conventional chemotherapy, resulting in a poorer prognosis and a higher recurrence rate than those with other subtypes of breast cancer. The RNA-binding protein Hu antigen R (HuR) is a posttranscriptional regulator, which can stabilize target mRNAs and regulate the translation of encoded proteins implicated in several hallmarks of cancer, including drug resistance. The high cytoplasmic expression of HuR is associated with high-grade malignancy and poor clinical outcomes of breast cancer. The accumulated cytoplasmic HuR has also been reported to contribute to chemoresistance in several types of cancer cells and inhibition of HuR sensitizes cancer cells to chemotherapy. Therefore, HuR is a promising target to overcome chemoresistance. We hypothesize that inhibition of HuR function by disrupting its interaction with mRNA can accelerate the decay of target mRNAs and thus reduce the translation level of proteins responsible for chemoresistance.Recently, our lab reported a small molecule HuR inhibitor, KH-3, which potently inhibits HuR function by disrupting HuR-mRNA interactions. In this study, we aim to investigate the functions of HuR in TNBC chemoresistance formation and evaluate whether HuR inhibition by KH-3 can enhance the efficacy of chemotherapy for TNBC. In order to determine whether HuR inhibition overcomes acquired chemoresistance of TNBC, we generated two MDA-MB-231 cell sub-lines with acquired resistance to docetaxel (231-TR) or doxorubicin (231-DR), respectively. Compared to the parental cell line, the two resistant sub-lines exhibit similar sensitivity to KH-3, and KH-3 re-sensitizes chemoresistant cells to docetaxel and doxorubicin in the MTT-based cytotoxicity assay and the colony formation assay, indicating that HuR inhibition can overcome acquired chemoresistance. The combination index suggests that the combination KH-3 with docetaxel or. doxorubicin has a synergistic effect. Moreover, the in vivo efficacy studies confirm that KH-3 synergized docetaxel treatment in both MDA-MB-231 and 231-TR orthotopic xenograft models. Mechanistically, several HuR direct target mRNAs implicated in chemoresistance are upregulated in the resistant cells, and KH-3 treatment can reverse the enhanced mRNA levels. The bioinformatic analysis suggests that several pathways may involve in the acquired resistance to docetaxel and doxorubicin. However, detailed molecular mechanisms of how KH-3 sensitizes TNBC to chemotherapy are still under investigation. This study suggests that inhibition of HuR is a promising strategy for overcoming chemotherapy resistance of TNBC.

Citation Format: Lanjing Wei, Qi Zhang, Cuncong Zhong, Jeffrey Aubé, Danny R. Welch, Xiaoqing Wu, Liang Xu. Overcome chemoresistance of triple-negative breast cancer by inhibiting the RNA-binding protein HuR [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-01-16.

Perturbation of BRMS1 interactome reveals pathways that impact metastasis

Breast Cancer Metastasis Suppressor 1 (BRMS1) expression is associated with longer patient survival in multiple cancer types. Understanding BRMS1 functionality will provide insights into both mechanism of action and will enhance potential therapeutic development. In this study, we confirmed that the C-terminus of BRMS1 is critical for metastasis suppression and hypothesized that critical protein interactions in this region would explain its function. Phosphorylation status at S237 regulates BRMS1 protein interactions related to a variety of biological processes, phenotypes [cell cycle (e.g., CDKN2A), DNA repair (e.g., BRCA1)], and metastasis [(e.g., TCF2 and POLE2)]. Presence of S237 also directly decreased MDA-MB-231 breast carcinoma migration in vitro and metastases in vivo. The results add significantly to our understanding of how BRMS1 interactions with Sin3/HDAC complexes regulate metastasis and expand insights into BRMS1's molecular role, as they demonstrate BRMS1 C-terminus involvement in distinct protein-protein interactions.

Abstract SY02-01: Using the hallmarks of metastasis to develop antimetastatic treatments

The complex interplay between tumor cells and the multiple microenvironments with which they interact during metastasis provides numerous potential targets for therapeutic intervention. Since metastasis is the primary cause of cancer morbidity and mortality, critical evaluation and prioritization of those targets represents the first step in developing treatments specifically targeting metastases. I will focus on the four features of metastatic cells that distinguish them from malignant cancer cells: motility & invasion, modulating local or secondary microenvironments, plasticity/adaptability, and colonizing secondary tissues. By defining the hallmarks of metastasis, my hope is that new therapies will be developed that will improve survival and quality of life.

For >4000 years, medical practitioners have recognized that tumor cell dissociation, dissemination and colonization of discontiguous secondary sites is the most lethal attribute of neoplastic cells. Cure rates are high for most cancers when diagnosis occurs before spread; but, once metastases develop, cancer is frequently considered incurable. I prefer to think of it as currently incurable, but potentially curable. Otherwise, what's the point? The premise is that the hallmarks when coupled with deeper understanding of the molecular mechanisms responsible will accelerate development of therapies that prevent and/or treat metastasis, reduce cancer deaths and improve patients' quality of life.

The context requires recognizing that metastasis is a distinct (but interrelated) phenotype to cancer. Development of cancer involves several hallmarks, as defined by Hanahan and Weinberg - immortality, genomic instability, resisting cell death, altered metabolism and invasion/metastasis, including how cancer cells interact with the stroma - sustained angiogenesis, promote inflammation, immune evasion, resistance to growth inhibition, and relative autonomy. Acquisition of malignant characteristics, in general, follow a progression through precancerous, transformed, benign and malignant (invasive) states. Superimposed upon the hallmarks of cancer development are the hallmarks of metastasis. Critically, the definition of metastasis is the process of spreading to a nearby or distant, discontiguous secondary site and the establishment of macroscopic secondary foci.

Every metastatic cell must accomplish an entire cascade series of sequential steps. To spread, a subset of heterogenous primary tumor cells enter a circulatory compartment (hematogenous, lymphatic, or body cavity) and disseminate (note: cells can move between circulatory compartments). This early step is surprisingly common with >106 cells/gm tumor entering the vasculature. Indeed, many cells disseminate long prior to tumor detection.

Before tumors are detectable, cells begin to manipulate local stroma and distant sites. Establishment of a pre-metastatic niche occurs via tumor cell-derived soluble factors and extracellular vesicles communicating with HSC or MSC. Induced bone marrow-derived stem cells mobilize to seed and manipulate secondary microenvironments, making each niche favorable for colonization.

Cells must migrate, restructure or degrade the ECM, often co-opting normal physiologic activities and responding to motility-inducing and chemotactic factors. Migration can occur as cooperating cell clusters (collective migration) or as rogue individual cells. Some cells usurp a reversible embryologic process, the epithelial-mesenchymal transition (EMT), or entosis, or use amoeboid characteristics to squeeze through small spaces without proteolytic ECM degradation, or a combinations of these mechanisms to invade. Invasion through a basement membrane is the defining feature of malignancy. But the ability to invade is insufficient to metastasize. Since millions to billions of cancer cells begin the process but the vast majority fail to complete it, mobility is also necessary, but not sufficient. Importantly, tumor cells can manipulate stromal cells and immune cells into assisting their motile and invasive phenotypes.

Upon entry into a transport compartments, tumor cells distribute to wherever that compartment leads using both active and passive mechanisms. Circulating tumor cells (CTC) can provide very useful information regarding probabilities of metastatic spread as well as therapeutic efficacy. But, as noted above, many cells disseminate, but few successfully form metastases. Therefore, it is critical to distinguish between mere dispersal of cells and actual metastasis formation.

To successfully form a metastatic focus, a disseminated cell must eventually arrest at a compatible ectopic site and extravasate. Arrest can either be active or passive. However, the distribution of metastases is non-random.

The last step of metastasis, colonization, utilizes the same processes that lead to primary tumor growth - response to pro-growth factors, resistance to growth inhibitors, adequate oxygenation, nutrients and angiogenesis. Successful colonization often requires landing at a pre-metastatic niche. Despite extensive study the molecular mechanisms of colonization are still largely unknown. Some cells undergo prolonged (months to years) quiescence between seeding and colonization. What happens during that time is unknown except that some cells temporarily mitotically arrest, while others await angiogenesis.

Lineage tracing shows that metastases utilized both parallel and sequential evolution processes. Single cell analyses confirm that >90% of metastases are clonally derived and possess the same driver mutations that led to tumorigenesis. Individual metastases arise from different subpopulations from the primary tumor, many sharing overlapping gene changes. All steps of metastasis involve coordinated expression of multiple genes. Cells in the process of metastasizing sometimes exhibit an incomplete cohort of those gene cassettes. Intervention will require distinguishing between cells partially capable versus those destined to become metastases. This distinction is most critical when cells that have seeded, but not yet colonized, a secondary site.

So, what constitutes the ‘hallmarks' of metastasis? The challenge when defining any hallmarks in cancer is that cancer cells utilize the same molecules and processes that normal cells use. It is the combination of hallmarks that distinguish metastatic cells, not just the presence of a subset of hallmarks. All metastatic cells are motile and penetrate basement membranes. All metastatic cells somehow manipulate myriad microenvironments prior to and during transit. All cells must continuously adapt to the conditions in which they find themselves (i.e., sheer forces in the blood stream, immune attack, deformability, etc.). And finally, all metastatic cells must successfully colonize secondary tissues. This last hallmark distinguishes mere dissemination from metastasis.

Is defining the hallmarks of metastasis helpful in clinical oncology? Distinguishing cells with the potential from those which actually metastasize is key to identifying targets for new treatments. Some insights have already led to improved 5-year survival and quality-of-life. But unfortunately, improvements have not yet been realized for all cancers. Yet, I believe we are poised to make significant inroads by applying the principles outlined here.

Besides the biology, there are other aspects of metastasis which are just as important. While not the focus of this presentation, they deserve attention. They include better management of the emotional toll treatments exert on patients (and families). Every scan is anticipated with ‘scanxiety,' a fear that the tumor has grown or recurred. Metastatic patients constantly fear of running out of options. And financial toxicities cannot be overlooked and are not sustainable. By proposing these hallmarks of metastasis, I hope a framework is provided which will accelerate translating the growing knowledge of molecular circuitry into treatments that prevent and eliminate metastases.

Acknowledgments: I thank colleagues, friends, trainees and metastatic patients who have taught me much and inspired me with your strength and courage. My lab has been supported by grants from the NIH, NCI, DoD, Komen, NFCR, METAvivor, Theresa's Foundation and Hall Family Professorship.

For additional details and references, see Cancer Res (2019) 79(12):3011-3027.

Citation Format: Danny R. Welch. Using the hallmarks of metastasis to develop antimetastatic treatments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr SY02-01.

Mechanisms of breast cancer metastasis

Invasive breast cancer tends to metastasize to lymph nodes and systemic sites. The management of metastasis has evolved by focusing on controlling the growth of the disease in the breast/chest wall, and at metastatic sites, initially by surgery alone, then by a combination of surgery with radiation, and later by adding systemic treatments in the form of chemotherapy, hormone manipulation, targeted therapy, immunotherapy and other treatments aimed at inhibiting the proliferation of cancer cells. It would be valuable for us to know how breast cancer metastasizes; such knowledge would likely encourage the development of therapies that focus on mechanisms of metastasis and might even allow us to avoid toxic therapies that are currently used for this disease. For example, if we had a drug that targeted a gene that is critical for metastasis, we might even be able to cure a vast majority of patients with breast cancer. By bringing together scientists with expertise in molecular aspects of breast cancer metastasis, and those with expertise in the mechanical aspects of metastasis, this paper probes interesting aspects of the metastasis cascade, further enlightening us in our efforts to improve the outcome from breast cancer treatments.

Abstract PS16-20: Targeting the RNA-binding protein HuR to overcome chemoresistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a much lower 5-year relative survival rate (77%) than the overall breast cancer (91%). Chemotherapy remains the primary choice for the treatment of TNBC. However, patients often develop resistance to conventional chemotherapy after long-term exposure to the chemo-drugs, resulting in poorer prognosis and higher tumor reoccurrence compared to other subtypes of breast cancer. Therefore, understanding and overcoming drug resistance is critical for the successful treatment of TNBC. The Hu antigen R (HuR) or ELAVL1 (embryonic lethal, abnormal vision, Drosophila-like protein 1) plays an important role in chemotherapy resistance. The RNA-binding protein HuR is a posttranscriptional regulator, which can stabilize target mRNAs by binding to U- or AU-rich elements (ARE) mainly in 3’ untranslated region (UTR) of mRNAs and upregulate the translation of them. The encoded proteins are implicated in multiple cancer hallmarks, including chemoresistance. The overexpression of HuR, especially accumulated cytoplasmic expression, has been identified to be related to chemoresistance in many types of cancer. We hypothesize that inhibition of HuR function by disrupting its interaction with mRNAs can accelerate the decay of mRNAs and thus reduce the translation of proteins responsible for chemoresistance.Recently, we reported a small molecule HuR inhibitor, KH-3, which potently inhibit HuR function by disrupting the HuR-mRNA interaction. KH-3 can effectively suppress the growth and invasion of TNBC cells in vitro and in vivo. In this study, we aim to verify that HuR is a target for overcoming chemoresistance and evaluate that KH-3 as a HuR functional inhibitor can enhance the efficacy of chemotherapy for TNBC cells. To determine whether HuR inhibition can overcome acquired chemotherapy resistance of TNBCs, we generated MDA-MB-231 sub-cell lines with acquired resistance against docetaxel or doxorubicin. Our results show that inhibition of HuR by KH-3 could synergize chemotherapy for TNBC in vitro and in vivo. More interestingly, KH-3 treatment could re-sensitize resistant TNBC cells to chemo-drugs, indicating that HuR inhibition can overcome acquired chemoresistance. In the study of mechanism of actions, several pathways and HuR direct target mRNAs are found to be involved in acquired docetaxel and doxorubicin resistance. The detailed molecular mechanisms of how KH-3 sensitizes TNBC to chemotherapy is currently under investigation. This study provides a new strategy to overcome chemotherapy resistance and improve the overall survival rate of patients with TNBC.

Citation Format: Lanjing Wei, Qi Zhang, Gulhumay Gardashova, Cuncong Zhong, Jeffrey Aubé, Danny R. Welch, Xiaoqing Wu, Liang Xu. Targeting the RNA-binding protein HuR to overcome chemoresistance in triple-negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-20.

Preclinical Evaluation of Gilteritinib on NPM1-ALK-Driven Anaplastic Large Cell Lymphoma Cells

Anaplastic large cell lymphoma (ALCL) is an aggressive type of non-Hodgkin lymphoma. More than three-fourths of anaplastic lymphoma kinase (ALK)-positive ALCL cases express the nucleophosmin 1 (NPM1)-ALK fusion gene as a result of t(2;5) chromosomal translocation. The homodimerization of NPM1-ALK fusion protein mediates constitutive activation of the chimeric tyrosine kinase activity and downstream signaling pathways responsible for lymphoma cell proliferation and survival. Gilteritinib is a tyrosine kinase inhibitor recently approved by the FDA for the treatment of FMS-like tyrosine kinase mutation-positive acute myeloid leukemia. In this study, we demonstrate for the first time gilteritinib-mediated growth inhibitory effects on NPM1-ALK-driven ALCL cells. We utilized a total of five ALCL model cell lines, including both human and murine. Gilteritinib treatment inhibits NPM1-ALK fusion kinase phosphorylation and downstream signaling, resulting in induced apoptosis. Gilteritinib-mediated apoptosis was associated with caspase 3/9, PARP cleavage, the increased expression of proapoptotic protein BAD, and decreased expression of antiapoptotic proteins, survivin and MCL-1. We also found downregulation of fusion kinase activity resulted in decreased c-Myc protein levels. Furthermore, cell-cycle analysis indicated gilteritinib induced G₀-G₁-phase cell-cycle arrest and reduced CD30 expression. In summary, our preclinical studies explored the novel therapeutic potential of gilteritinib in the treatment of ALCL cells expressing NPM1-ALK and potentially in other ALK or ALK fusion-driven hematologic or solid malignancies. IMPLICATIONS: Our preclinical results explore the use of gilteritinib for the treatment of NPM1-ALK-driven ALCL cells and pave a path for developing future clinical trials. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/19/5/913/F1.large.jpg.

Suppression of pancreatic cancer liver metastasis by secretion-deficient ITIH5

BACKGROUND

Previously, we identified ITIH5 as a suppressor of pancreatic ductal adenocarcinoma (PDAC) metastasis in experimental models. Expression of ITIH5 correlated with decreased cell motility, invasion and metastasis without significant inhibition of primary tumour growth. Here, we tested whether secretion of ITIH5 is required to suppress liver metastasis and sought to understand the role of ITIH5 in human PDAC.

METHODS

We expressed mutant ITIH5 with deletion of the N-terminal secretion sequence (ITIH5Δs) in highly metastatic human PDAC cell lines. We used a human tissue microarray (TMA) to compare ITIH5 levels in uninvolved pancreas, primary and metastatic PDAC.

RESULTS

Secretion-deficient ITIH5Δs was sufficient to suppress liver metastasis. Similar to secreted ITIH5, expression of ITIH5Δs was associated with rounded cell morphology, reduced cell motility and reduction of liver metastasis. Expression of ITIH5 is low in both human primary PDAC and matched metastases.

CONCLUSIONS

Metastasis suppression by ITIH5 may be mediated by an intracellular mechanism. In human PDAC, loss of ITIH5 may be an early event and ITIH5-low PDAC cells in primary tumours may be selected for liver metastasis. Further defining the ITIH5-mediated pathway in PDAC could establish future therapeutic exploitation of this biology and reduce morbidity and mortality associated with PDAC metastasis.

KISS1 in metastatic cancer research and treatment: potential and paradoxes

The significance of KISS1 goes beyond its original discovery as a metastasis suppressor. Its function as a neuropeptide involved in diverse physiologic processes is more well studied. Enthusiasm regarding KISS1 has cumulated in clinical trials in multiple fields related to reproduction and metabolism. But its cancer therapeutic space is unsettled. This review focuses on collating data from cancer and non-cancer fields in order to understand shared and disparate signaling that might inform clinical development in the cancer therapeutic and biomarker space. Research has focused on amino acid residues 68-121 (kisspeptin 54), binding to the KISS1 receptor and cellular responses. Evidence and counterevidence regarding this canonical pathway require closer look at the covariates so that the incredible potential of KISS1 can be realized.

Abstract 2662: Mitochondrial genetics appear to alter immune cell development/trafficking

Background Metastatic burden is the leading cause of cancer deaths; however, it remains unclear why some patients are more susceptible to metastatic disease. While the nuclear genome's role in tumor progression and metastasis is known, the role of mitochondrial DNA (mtDNA) polymorphisms (SNP) has only recently been explored. Using mitochondrial nuclear exchange (MNX) mice, we previously showed that mtDNA strongly influences mammary carcinoma progression and metastasis both intrinsically and via non-cell autonomous mechanisms. We hypothesized that mtDNA SNP alter immune cell development/trafficking which, in turn, could influence metastasis efficiency.

Methods Peritoneal exudate, and splenocytes were collected from male and female wild-type C57BL/6J (CC) and C3H/HeN (HH), and MNX mice - C57BL/6-mtMNX(C3H/HeN) (CH) and C3H/HeN-mtMNX(C57BL/6J) (HC) mice [first letter=nuclear; second letter=mitochondrial]. Lung metastases were established from tail-vein injection of E0771 (CC/CH) or K1735-M2 (HH/HC) cell lines.

Results Lung metastases derived from histocompatible (i.e. nDNA matched) tumor cell injection into wild-type or MNX mice increased in C3H/HeN mtDNA backgrounds (HH and CH). No significant differences were observed in seeding, suggesting that mtDNA mediated differences in metastatic microenvironments likely impact metastatic outgrowth. No significant changes in broad immune cell populations were observed in naïve animals, but selective changes in differentiation markers were observed. The most significant change was lower CD11c+ peritoneal macrophages in HH (3%) versus CC (16%) mice (p < 0.001). C57BL/6 mtDNA (HC) increased the percentage of macrophages (9%) compared to wild-type (HH) (p < 0.001). We next confirmed a role for mitochondrial derived ROS mediating immune microenvironmental regulation of metastasis, as mtDNA mediated metastatic differences are abrogated upon treatment with the anti-oxidant MitoTEMPO. Tumor infiltrating CD8+ lymphocytes (TIL) increased 1.5-fold in CH (1.7%) compared to wild-type CC (1.2%) (p = 0.07) while no differences were observed between HH and HC mice. Consistent with changes in metastasis in the HH background, MitoTempo treatment reduced CD4+ TIL >1.5-fold (1.5%), compared to the vehicle control (2.8%) (p = 0.029).

Discussion Our data support the hypothesis that mitochondrial SNP modulate immune cell development and/or trafficking, providing a plausible explanation for how metastatic potentials of syngeneic tumor cells injected into MNX mice are altered. That is, mtDNA contributions to immune function affect metastasis and may provide insight as to why some immune therapies succeed/fail.

Support: DOD BCRP BC171381 and Kansas INBRE P20 GM103418 (TCB); Susan G. Komen for the Cure SAC110037; National Foundation for Cancer Research and NIH CA168524 (DRW)

Citation Format: Thomas C. Beadnell, Amanda E. Brinker, Cori Fain, Carolyn J. Vivian, Danny R. Welch. Mitochondrial genetics appear to alter immune cell development/trafficking [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 2662.

Abstract IA30: Intrinsic and extrinsic contributions of mitochondrial DNA to metastatic efficiency: A genetic explanation for disparities in metastasis efficiency?

Single-nucleotide polymorphisms (SNP) in nuclear and mitochondrial DNA are used to define clades (or races) in people, as well as different strains in mice (PMID: 27383787). Previous studies showed that nuclear SNP determine metastasis efficiency; we hypothesized that mtDNA SNP could also play roles in tumorigenicity and metastasis. Mitochondrial Nuclear Exchange (MNX) mice, created by transferring an oocyte nucleus from strainx into an enucleated oocyte from strainy (PMID: 27840835), show that mammary tumor formation and metastasis are regulated by inherited mitochondrial polymorphisms when MNX mice were bred to MMTV-PyMT or MMTV-HER2 mice (PMID: 26471915; 29070615). Since stromal compartments also possess changed mitochondria in MNX mice, we hypothesized that mitochondrial SNP in noncancer compartments could exert effects on tumor formation or metastasis in addition to genetic (cell autonomous) changes. Syngeneic tumor cells were injected into MNX mice with the same nuclear (and, therefore, same histocompatibility) background. Experimental metastasis was compared between wild-type and MNX mice (i.e., with same or different mtDNA backgrounds, respectively). E0771 mammary carcinoma and B16-F10 melanoma cells (both syngeneic to C57BL/6J), formed significantly (P<0.01) more lung metastases in C57BL/6J-mtMNX(C3H/HeN). K1735-M2 melanoma cells (syngeneic to C3H/HeN) formed significantly (P<0.05) fewer lung metastases in C3H/HeNmtMNX(C57BL/6J) mice. These results have been replicated ≥3 times using >10 mice per experiment. C57BL/6J mitochondria confer resistance to metastasis in both cell autonomous and non-cell autonomous experiments. Basal metabolic and ROS differences comparing mouse embryonic fibroblasts isolated from wild-type and MNX mice exist and may be responsible for the stromal effects. Likewise, significant and statistically significant differences in MNX mice for nuclear DNA methylation (PMID: 28663334) and epigenetic marks (J. McGuire & D.R. Welch, in preparation), immune (T.C. Beadnell & D.R. Welch, in preparation) and microbota (S.J. Manley & D.R. Welch, in preparation) profiles are observed. Together, our findings highlight the striking influences that mitochondrial haplotypes can exert on tumorigenicity and metastasis via both intrinsic and extrinsic mechanisms. These findings also suggest that mitochondrial SNP could serve, in part, as a genetic basis to explain racial disparities with regard to cancer aggressiveness.

Support: Susan G. Komen for the Cure (SAC11037), Natl. Fndn. Cancer Res., CA168524, W81XWH-18-1-0450, GM103418.

Citation Format: Danny R. Welch. Intrinsic and extrinsic contributions of mitochondrial DNA to metastatic efficiency: A genetic explanation for disparities in metastasis efficiency? [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr IA30.

Role of the tumor microenvironment in regulating the anti-metastatic effect of KISS1

KISS1, a metastasis suppressor gene, has been shown to block metastasis without affecting primary tumor formation. Loss of KISS1 leads to invasion and metastasis in multiple cancers, which is the leading cause of cancer morbidity and mortality. The discovery of KISS1 has provided a ray of hope for early clinical diagnosis and for designing effective treatments targeting metastatic cancer. However, this goal requires greater holistic understanding of its mechanism of action. In this review, we go back into history and highlight some key developments, from the discovery of KISS1 to its role in regulating multiple physiological processes including cancer. We discuss key emerging roles for KISS1, specifically interactions with tissue microenvironment to promote dormancy and regulation of tumor cell metabolism, acknowledged as some of the key players in tumor progression and metastasis. We finally discuss strategies whereby KISS1 might be exploited clinically to treat metastasis.

Mitochondrial Haplotype of the Host Stromal Microenvironment Alters Metastasis in a Non-cell Autonomous Manner

Mitochondria contribute to tumor growth through multiple metabolic pathways, regulation of extracellular pH, calcium signaling, and apoptosis. Using the Mitochondrial Nuclear Exchange (MNX) mouse models, which pair nuclear genomes with different mitochondrial genomes, we previously showed that mitochondrial SNPs regulate mammary carcinoma tumorigenicity and metastatic potential in genetic crosses. Here, we tested the hypothesis that polymorphisms in stroma significantly affect tumorigenicity and experimental lung metastasis. Using syngeneic cancer cells (EO771 mammary carcinoma and B16-F10 melanoma cells) injected into wild-type and MNX mice (i.e., same nuclear DNA but different mitochondrial DNA), we showed mt-SNP-dependent increases (C3H/HeN) or decreases (C57BL/6J) in experimental metastasis. Superoxide scavenging reduced experimental metastasis. In addition, expression of lung nuclear-encoded genes changed specifically with mt-SNP. Thus, mitochondrial-nuclear cross-talk alters nuclear-encoded signaling pathways that mediate metastasis via both intrinsic and extrinsic mechanisms. SIGNIFICANCE: Stromal mitochondrial polymorphisms affect metastatic colonization through reactive oxygen species and mitochondrial-nuclear cross-talk.

Abstract P5-05-09: Chemo-sensitization of triple negative breast cancer by targeting RNA-binding protein HuR

Triple negative breast cancer (TNBC) has a lower 5-year survival rate and higher recurrence rate compared to other types of breast cancer, which is partially due to the acquired resistance to current treatment regimens. The RNA-binding protein Hu antigen R (HuR) is overexpressed in breast cancer. Cytoplasmic HuR accumulation correlates with high-grade malignancy, poor distant disease-free survival and serves as a prognostic factor for poor clinical outcome in breast cancer. HuR promotes tumorigenesis by promoting mRNA stability and translation of proteins implicated in proliferation, survival, angiogenesis, invasion, and metastasis. HuR also modulates sensitivity of breast cancer cells to chemotherapy. HuR knockout in TNBC cells with high HuR sensitizes them to chemotherapy while HuR overexpression induces chemo-resistance. Meanwhile, chemotherapy promotes cytoplasmic HuR accumulation and increases expression of HuR target encoding proteins in TNBC cells. Therefore, there is a positive feedback loop between HuR and chemo-resistance. These findings suggest that HuR plays a critical role in promoting a drug-resistance mechanism and HuR is a potential target for developing a novel therapy to overcome chemo-resistance in TNBC. RNA-binding proteins such as HuR had previously been considered to be “undruggable” due to the lack of a well-defined binding pocket for target RNAs. Nevertheless, using high throughput screening followed by structure-based rational design and lead optimization, we have identified small molecules that potently inhibit HuR-mRNA interaction with nM to sub-µM potency. Our top HuR inhibitor, KH-3, inhibits TNBC cell growth in vitro and in vivo. KH-3 also sensitizes TNBC cells to docetaxel and doxorubicin treatment in vitro. Furthermore, acquired docetaxel-resistant MDA-MB-231 cells and doxorubicin-resistant MDA-MB-231 cells display similar sensitivity to KH-3 to their parental cells. In the study of mechanism of action, several HuR direct targets are found to be involved in acquired docetaxel and doxorubicin resistance. KH-3 can disrupt the interaction of HuR with those target mRNAs. In animal efficacy studies, the combination of KH-3 and chemotherapy shows synergistic effect in both parental and acquired resistant cell xenograft models. Our data provide a proof-of-principle that HuR inhibition by KH-3 may be developed as a promising molecular therapy to overcome chemo-resistance of TNBC with high HuR.

Citation Format: Xiaoqing Wu, Lanjing Wei, Gulhumay Gardashova, Cuncong Zhong, Lan Lan, Qi Zhang, Dan A Dixon, Danny R Welch, Jeffrey Aubé, Liang Xu. Chemo-sensitization of triple negative breast cancer by targeting RNA-binding protein HuR [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-05-09.

KISS1 in breast cancer progression and autophagy

Tumor suppressors are cellular proteins typically expressed in normal (non-cancer) cells that not only regulate such cellular functions as proliferation, migration and adhesion, but can also be secreted into extracellular space and serve as biomarkers for pathological conditions or tumor progression. KISS1, a precursor for several shorter peptides, known as metastin (Kisspeptin-54), Kisspeptin-14, Kisspeptin-13 and Kisspeptin-10, is one of those metastasis suppressor proteins, whose expression is commonly downregulated in the metastatic tumors of various origins. The commonly accepted role of KISS1 in metastatic tumor progression mechanism is the ability of this protein to suppress colonization of disseminated cancer cells in distant organs critical for the formation of the secondary tumor foci. Besides, recent evidence suggests involvement of KISS1 in the mechanisms of tumor angiogenesis, autophagy and apoptosis regulation, suggesting a possible role in both restricting and promoting cancer cell invasion. Here, we discuss the role of KISS1 in regulating metastases, the link between KISS1 expression and the autophagy-related biology of cancer cells and the perspectives of using KISS1 as a potential diagnostic marker for cancer progression as well as a new anti-cancer therapeutics.

Mitochondrial genetics cooperate with nuclear genetics to selectively alter immune cell development/trafficking

The nuclear genome drives differences in immune cell populations and differentiation potentials, in part regulated by changes in metabolism. Despite this connection, the role of mitochondrial DNA (mtDNA) polymorphisms (SNP) in this process has not been examined. Using mitochondrial nuclear exchange (MNX) mice, we and others have shown that mtDNA strongly influences varying aspects of cell biology and disease. Based upon an established connection between mitochondria and immune cell polarization, we hypothesized that mtDNA SNP alter immune cell development, trafficking, and/or differentiation. Innate and adaptive immune cell populations were isolated and characterizated from the peritoneum and spleen. While most differences between mouse strains are regulated by nuclear DNA (nDNA), there are selective changes that are mediated by mtDNA differences (e.g., macrophage (CD11c) differentiation), These findings highlight how nuclear-mitochondrial crosstalk may alter pathology and physiology via regulation of specific components of the immune system.

The Histone Demethylase KDM3A, Increased in Human Pancreatic Tumors, Regulates Expression of DCLK1 and Promotes Tumorigenesis in Mice

BACKGROUND & AIMS

The histone lysine demethylase 3A (KDM3A) demethylates H3K9me1 and H3K9Me2 to increase gene transcription and is upregulated in tumors, including pancreatic tumors. We investigated its activities in pancreatic cancer cell lines and its regulation of the gene encoding doublecortin calmodulin-like kinase 1 (DCLK1), a marker of cancer stem cells.

METHODS

We knocked down KDM3A in MiaPaCa-2 and S2-007 pancreatic cancer cell lines and overexpressed KDM3A in HPNE cells (human noncancerous pancreatic ductal cell line); we evaluated cell migration, invasion, and spheroid formation under hypoxic and normoxic conditions. Nude mice were given orthotopic injections of S2-007 cells, with or without (control) knockdown of KDM3A, and HPNE cells, with or without (control) overexpression of KDM3A; tumor growth was assessed. We analyzed pancreatic tumor tissues from mice and pancreatic cancer cell lines by immunohistochemistry and immunoblotting. We performed RNA-sequencing analysis of MiaPaCa-2 and S2-007 cells with knockdown of KDM3A and evaluated localization of DCLK1 and KDM3A by immunofluorescence. We analyzed the cancer genome atlas for levels of KDM3A and DCLK1 messenger RNA in human pancreatic ductal adenocarcinoma (PDAC) tissues and association with patient survival time.

RESULTS

Levels of KDM3A were increased in human pancreatic tumor tissues and cell lines, compared with adjacent nontumor pancreatic tissues, such as islet and acinar cells. Knockdown of KDM3A in S2-007 cells significantly reduced colony formation, invasion, migration, and spheroid formation, compared with control cells, and slowed growth of orthotopic tumors in mice. We identified KDM3A-binding sites in the DCLK1 promoter; S2-007 cells with knockdown of KDM3A had reduced levels of DCLK1. HPNE cells that overexpressed KDM3A formed foci and spheres in culture and formed tumors and metastases in mice, whereas control HPNE cells did not. Hypoxia induced sphere formation and increased levels of KDM3A in S2-007 cells and in HPNE cells that overexpressed DCLK1, but not control HPNE cells. Levels of KDM3A and DCLK1 messenger RNA were higher in human PDAC than nontumor pancreatic tissues and correlated with shorter survival times of patients.

CONCLUSIONS

We found human PDAC samples and pancreatic cancer cell lines to overexpress KDM3A. KDM3A increases expression of DCLK1, and levels of both proteins are increased in human PDAC samples. Knockdown of KDM3A in pancreatic cancer cell lines reduced their invasive and sphere-forming activities in culture and formation of orthotopic tumors in mice. Hypoxia increased expression of KDM3A in pancreatic cancer cells. Strategies to disrupt this pathway might be developed for treatment of pancreatic cancer.

Abstract 654: Dietary interventions ameliorate infectious colitis through differential regulation of Lgr5

Background: During inflammatory bowel disease (IBD), the disruption of the epithelial barrier and translocation of bacteria drive inappropriate immune responses and unresolved inflammation. Rapid wound healing responses orchestrated by intestinal stem cells (ISCs) are central to inflammatory resolution and normalization of the mucosal barrier. Commensal microbiota ferment fibers to produce short-chain-fatty-acids (SCFAs) such as butyrate and its decrease has been linked to IBD. However, the mechanism through which SCFAs promote wound healing is poorly understood.

Aims: The present study was designed to test the hypothesis that dietary fibers/butyrate ameliorate infectious colitis by differentially regulating Lgr5-dependent crypt regeneration and wound healing.

Methods: Lgr5CreERT2/+; Rosa26LacZ reporter (Lgr5-R) mice and wild-type littermates were infected with Citrobacter rodentium (CR; 108 CFUs) and fed with either 6% Pectin (Pec) or 6% Tributyrin (Tbt) diets followed by euthanasia at 12 days post-infection. To partially deplete microbiota, mice were also given a cocktail of vancomycin (500mg/L), metronidazole (1g/L) and Ciprofloxacin (0.2g/L) for 10 days starting 3-days post-CR infection. Fresh feces pre- and post-infection/treatments were taken for 16S rDNA sequencing. Lineage tracing post-tamoxifen and Lgr5 promoter reporter activity assays were performed.

Results: Both Pec and Tbt reduced the severity of CR-induced colitis as was evidenced by increased body weight and colon length, reduced immune cell infiltration and increased mucus production compared with CR-infected but untreated mice. 16s rDNA sequencing revealed significant dysbiosis during CR infection with the dominance of Proteobacteria and loss of Firmicutes and Bacteroidetes. Both Pec and Tbt diets reduced the levels of Proteobacteria and restored Firmicutes and Bacteroidetes phyla to pre-infection levels. X-gal staining revealed that there was an expansion of LacZ-labeled Lgr5(+) stem cells in the colons of CR infected Lgr5-R mice when subjected to dietary intervention via Pectin and Tributyrin as sources of butyrate compared with controls. Interestingly, Pec-induced Lgr5 regulation was dependent upon the presence of gut microbiota as antibiotics treatment reduced Pec-induced Lgr5 expansion and the extent of crypt regeneration. Tbt-treatment, on the other hand, regulated Lgr5 independently of the microbiota. Butyrate, in a dose-dependent (1-10mM) manner, increased Lgr5 promoter reporter activity. Docking studies further revealed butyrate’s ability to efficiently bind Lgr5 with a -4.0 Kcal/mol binding energy. The cellular thermal shift assay showed that butyrate was indeed able to bind Lgr5.

Conclusions: Thus, dietary interventions, by altering the gut microbiota, can differentially regulate Lgr5’s ability to orchestrate crypt regeneration and wound healing to ameliorate colitis.

Citation Format: Ishfaq Ahmed, Badal C. Roy, Rita-Marie T. Raach, Sharon J. Manley, Pugazhendhi Srinivasan, Prasad Dandawate, Afreen Sayed, Danny R. Welch, Shrikant Anant, Venkatesh Sampath, Shahid Umar. Dietary interventions ameliorate infectious colitis through differential regulation of Lgr5 [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 654.

Abstract 1235: Targeting RNA-binding protein HuR to inhibit human breast cancer invasion and metastasis

The majority of breast cancer-related mortality is due to metastasis. Patients diagnosed with metastatic breast cancer have a dismal 5-year survival rate of only 24%. The RNA-binding protein Hu antigen R (HuR) is overexpressed in breast cancer. Cytoplasmic HuR accumulation correlates with high-grade malignancy, poor distant disease-free survival and serves as a prognostic factor for poor clinical outcome in breast cancer. HuR promotes tumorigenesis by regulating numerous proto-oncogenes, growth factors and cytokines that implicate major tumor hallmarks including invasion and metastasis. Knocking out HuR by CRISPR/CAS9 technology inhibits cell invasion in breast cancer cells. Therefore, HuR is an emerging target for breast cancer therapy, especially the lethal metastatic breast cancer. RNA-binding proteins had previously been considered “undruggable” due to lack of a well-defined binding pocket for target RNAs. Using high throughput screening followed by structure-based rational design and lead optimization, we have identified small molecules that inhibit HuR-mRNA interaction at nM to sub-µM potency. Our lead compound, KH-3, potently inhibits breast cancer cell growth and decreases cell invasion in vitro similar to HuR knockout, as well as increasing the expression of epithelial marker E-cadherin. In the study of mechanism of action, a transcription factor, FOXQ1, which is recently revealed to implicate in breast cancer invasion and metastasis processes, is found for the first time to be a direct mRNA target of HuR and one of the top genes that are reduced by KH-3 treatment. Exogenous introduction of FOXQ1 can rescue cell invasive capability impaired by HuR knockout and abolish the effect of KH-3 on inhibiting cell invasion in breast cancer cells. Moreover, KH-3 disrupts HuR-FOXQ1 interaction in RNP-IP, RNA pull down and FOXQ1 3′-UTR luciferase reporter assays. In vivo efficacy studies show that KH-3 not only exhibits potent antitumor efficacy in an orthotopic xenograft model of breast cancer, but also efficiently inhibits lung metastasis and improves mouse survival in an experimental metastasis model. Our data provide a proof-of-principle that HuR inhibition by KH-3 may be developed as a promising molecular therapy for inhibiting progression and metastasis of breast cancer with high HuR.

Citation Format: Xiaoqing Wu, Gulhumay Gardashova, Lan Lan, Shuang Han, Cuncong Zhong, Ragul Gowthaman, John Karanicolas, Dan A. Dixon, Danny R. Welch, Ling Li, Min Ji, Jeffrey Aubé, Liang Xu. Targeting RNA-binding protein HuR to inhibit human breast cancer invasion and metastasis [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 1235.

Defining the Hallmarks of Metastasis

Metastasis is the primary cause of cancer morbidity and mortality. The process involves a complex interplay between intrinsic tumor cell properties as well as interactions between cancer cells and multiple microenvironments. The outcome is the development of a nearby or distant discontiguous secondary mass. To successfully disseminate, metastatic cells acquire properties in addition to those necessary to become neoplastic. Heterogeneity in mechanisms involved, routes of dissemination, redundancy of molecular pathways that can be utilized, and the ability to piggyback on the actions of surrounding stromal cells makes defining the hallmarks of metastasis extraordinarily challenging. Nonetheless, this review identifies four distinguishing features that are required: motility and invasion, ability to modulate the secondary site or local microenvironments, plasticity, and ability to colonize secondary tissues. By defining these first principles of metastasis, we provide the means for focusing efforts on the aspects of metastasis that will improve patient outcomes.

Mitochondrial polymorphisms contribute to aging phenotypes in MNX mouse models

Many inbred strains of mice develop spontaneous tumors as they age. Recent awareness of the impacts of mitochondrial DNA (mtDNA) on cancer and aging has inspired developing a mitochondrial-nuclear exchange (MNX) mouse model in which nuclear DNA is paired with mitochondrial genomes from other strains of mouse. MNX mice exhibit mtDNA influences on tumorigenicity and metastasis upon mating with transgenic mice. However, we also wanted to investigate spontaneous tumor phenotypes as MNX mice age. Utilizing FVB/NJ, C57BL/6J, C3H/HeN, and BALB/cJ wild-type inbred strains, previously documented phenotypes were observed as expected in MNX mice with the same nuclear background. However, aging nuclear matched MNX mice exhibited decreased occurrence of mammary tumors in C3H/HeN mice containing C57BL/6J mitochondria compared to wild-type C3H/HeN mice. Although aging tumor phenotypes appear to be driven by nuclear genes, evidence suggesting that some differences are modified by the mitochondrial genome is presented.

Roles of the mitochondrial genetics in cancer metastasis: not to be ignored any longer

Mitochondrial DNA (mtDNA) encodes for only a fraction of the proteins that are encoded within the nucleus, and therefore has typically been regarded as a lesser player in cancer biology and metastasis. Accumulating evidence, however, supports an increased role for mtDNA impacting tumor progression and metastatic susceptibility. Unfortunately, due to this delay, there is a dearth of data defining the relative contributions of specific mtDNA polymorphisms (SNP), which leads to an inability to effectively use these polymorphisms to guide and enhance therapeutic strategies and diagnosis. In addition, evidence also suggests that differences in mtDNA impact not only the cancer cells but also the cells within the surrounding tumor microenvironment, suggesting a broad encompassing role for mtDNA polymorphisms in regulating the disease progression. mtDNA may have profound implications in the regulation of cancer biology and metastasis. However, there are still great lengths to go to understand fully its contributions. Thus, herein, we discuss the recent advances in our understanding of mtDNA in cancer and metastasis, providing a framework for future functional validation and discovery.

The second genome: Effects of the mitochondrial genome on cancer progression

The role of genetics in cancer has been recognized for centuries, but most studies elucidating genetic contributions to cancer have understandably focused on the nuclear genome. Mitochondrial contributions to cancer pathogenesis have been documented for decades, but how mitochondrial DNA (mtDNA) influences cancer progression and metastasis remains poorly understood. This lack of understanding stems from difficulty isolating the nuclear and mitochondrial genomes as experimental variables, which is critical for investigating direct mtDNA contributions to disease given extensive crosstalk exists between both genomes. Several in vitro and in vivo models have isolated mtDNA as an independent variable from the nuclear genome. This review compares and contrasts different models, their advantages and disadvantages for studying mtDNA contributions to cancer, focusing on the mitochondrial-nuclear exchange (MNX) mouse model and findings regarding tumor progression, metastasis, and other complex cancer-related phenotypes.

The isolated C-terminal nuclear localization sequence of the breast cancer metastasis suppressor 1 is disordered

BRMS1 is a 246-residue-long protein belonging to the family of metastasis suppressors. It is a predominantly nuclear protein, although it can also function in the cytoplasm. At its C terminus, it has a region that is predicted to be a nuclear localization sequence (NLS); this region, NLS2, is necessary for metastasis suppression. We have studied in vitro and in silico the conformational preferences in aqueous solution of a peptide (NLS2-pep) that comprises the NLS2 of BRMS1, to test whether it has a preferred conformation that could be responsible for its function. Our spectroscopic (far-UV circular dichroism, DOSY-NMR and 2D-NMR) and computational (all-atom molecular dynamics) results indicate that NLS2-pep was disordered in aqueous solution. Furthermore, it did not acquire a structure even when experiments were performed in a more hydrophobic environment, such as the one provided by 2,2,2-trifluoroethanol (TFE). The hydrodynamic radius of the peptide in water was identical to that of a random-coil sequence, in agreement with both our molecular simulations and other theoretical predictions. Thus, we suggest that NLS2 is a disordered region, with non pre-formed structure, that participates in metastasis suppression.

Zeeman spectroscopy as a method for determining the magnetic field distribution in self-magnetic-pinch diodes (invited)

In the self-magnetic-pinch diode, the electron beam, produced through explosive field emission, focuses on the anode surface due to its own magnetic field. This process results in dense plasma formation on the anode surface, consisting primarily of hydrocarbons. Direct measurements of the beam's current profile are necessary in order to understand the pinch dynamics and to determine x-ray source sizes, which should be minimized in radiographic applications. In this paper, the analysis of the C IV doublet (580.1 and 581.2 nm) line shapes will be discussed. The technique yields estimates of the electron density and electron temperature profiles, and the method can be highly beneficial in providing the current density distribution in such diodes.

Abstract 431: Mitochondrial-nuclear crosstalk influences accumulation of mitochondrial DNA mutations in mammary tumor progression

Introduction: Previous studies demonstrated that mitochondrial inheritance may contribute to aggressiveness of metastatic disease. Accumulating evidence suggests the mitochondrial genetic background may influence how certain cancers behave. We utilized Mitochondrial-Nuclear eXchange (MNX) female mice crossed with transgenic mice over-expressing the Her-2 gene and showed mitochondrial DNA (mtDNA)-dependent differences in tumor latency, lung metastasis number and lung metastasis size. We hypothesized that mtDNA mutations accumulate as mammary tumors progress and that the evolution is associated with mtDNA-nuclear DNA cross-talk. To test this hypothesis, we conducted next generation sequencing analyses to examine the spectra of mutations in the mitochondrial genome.

Methods: Normal mammary gland, primary tumor and lung metastases [n=5 each] were obtained from FVB/NJ mice with FVB/NJ (designated FF), C57BL/6J (designated FC) or BALB/cJ mtDNA (designated FB). Epithelial cells from mammary gland or tumor cells were carefully isolated by laser capture microdissection in order to minimize contamination from surrounding stromal cell mtDNA. mtDNA was deep sequenced using three pools totaling 182 overlapping primers spanning the whole mitochondrial genome using the Ion TorrentTM PGM System. Sequences were compared to an FVB mtDNA reference sequence to detect variants.

Results: Significant differences in the total number of mtDNA mutations were observed between the wild-type and MNX mice. Both FB and FC MNX cohorts exhibited increased mtDNA mutations compared to the wild-type (FF). As tumor progressed, the numbers of and distribution of mutations across the mitochondrial genome increased. ‘Hotspots' were observed in FB mice (S12 rRNA, COX I, ND4, CYTB) that were distinct from common mutations in the FC mice (16S rRNA, COX I).

Discussion: As predicted, tumor cells accumulated more mutations in mtDNA as neoplastic cells from the primary tumor progressed to metastasis. Surprisingly, wild-type (FF) mice, even though more clinically aggressive (i.e., more metastases), accumulated fewer mtDNA mutations than tumors arising in the MNX mice. The mutations appear to occur in different sites, depending upon the nuclear-mitochondrial combination. Whether the mtDNA mutations function as contributors to metastatic efficiency has not yet been determined. Nonetheless, the data imply that nuclear-mitochondrial cross-talk influences mtDNA mutational spectra and metastasis and that defining the critical mtDNA genes most commonly involved may eventually be used to predict patient prognosis.

Citation Format: Takae M. Brewer, Amanda E. Brinker, Sharon Manley, Carolyn J. Vivian, Danny R. Welch. Mitochondrial-nuclear crosstalk influences accumulation of mitochondrial DNA mutations in mammary tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 431.

Abstract SY37-03: Mitochondrial genetic contributions to metastatic efficiency

Complex phenotypes, like tumorigenicity or metastasis, require coordinated expression of multiple genes. Additionally, the contributions of some of those genes can be affected by polymorphisms in the protein coding or regulatory sequences (PMID: 22257951). The pathobiology of metastasis remains poorly understood because both intrinsic (i.e., genetic) and extrinsic (i.e., tumor-microenvironment interactions) are involved. A growing body of data indicates demonstrate that there are underlying genetic components that govern the processes involved in cancer spread and colonization. To assess the contributions of mitochondrial genetics in metastasis, we created Mitochondrial Nuclear Exchange (MNX) mice by transferring an oocyte nucleus from strainx into an enucleated oocyte from strainy, and showed that mammary tumor formation and metastasis are regulated by inherited mitochondrial polymorphisms in an oncogenic driver-dependent manner (PMID: 26471915; PMID: 29070615). Since stromal compartments also possess changed mitochondria in the MNX mice, we hypothesized that mitochondrial polymorphisms in non-cancer cell compartments could exert effects on tumor formation and/or metastasis in addition to genetic (cell autonomous) changes. Syngeneic tumor cells were injected into MNX mice with the same nuclear, and therefore same MHC, background. Experimental metastasis was compared between wild-type and MNX mice (i.e., with same or different mtDNA backgrounds, respectively). E0771 mammary carcinoma and B16-F10 melanoma cells (both syngeneic to C57BL/6J), formed significantly (P<0.01) more lung metastases in C57BL/6J-mtMNX(C3H/HeN). K1735-M2 melanoma cells (syngeneic to C3H/HeN) formed significantly (P<0.05) fewer lung metastases in C3H/HeNmtMNXC57BL/6J. These results have been replicated ≥3 times using >10 mice per experiment. C57BL/6J mitochondria confer resistance to metastasis in both cell autonomous and non-cell autonomous experiments. Basal metabolic and ROS differences comparing mouse embryonic fibroblasts isolated from wild-type and MNX mice are among mechanisms being explored. Differential gene expression occurred in tissues isolated from wild-type and MNX mice (PMID: 28663334). Additionally, altered immune and microbiota profiles have been observed. Together, our findings highlight striking influences that mitochondrial haplotypes can exert on tumorigenicity and metastasis via both intrinsic and extrinsic mechanisms.

Support: Susan G. Komen for the Cure (SAC11037), Natl Fndn Cancer Res. and CA168524.

Citation Format: Danny R. Welch. Mitochondrial genetic contributions to metastatic efficiency [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr SY37-03.

Abstract 867: Blocking breast cancer metastasis by targeting HuR-FOXQ1 signaling axis

As most of treatment options do not work very well for metastatic cancer. Patients with metastatic cancer have a greatly lower survival rate compared with patients with local cancer. Metastasis remains a life-threat to cancer patients and an unmet medical need. The RBP Hu antigen R (HuR) is overexpressed in virtually all malignancies tested, including breast cancer. Cytoplasmic HuR accumulation correlates with high-grade malignancy, poor distant disease-free survival and serves as a prognostic factor for poor clinical outcome in breast cancer. HuR promotes tumorigenesis by promoting mRNA stability and translation of proteins implicated in proliferation, survival, angiogenesis, invasion, and metastasis. We found that silencing of HuR inhibited cell invasion in vitro in breast cancer. Using RIP-seq (ribonucleoprotein immunoprecipitation-sequencing), a transcription factor FOXQ1, which is recently revealed to implicate in breast cancer invasion and metastasis processes, is found to be a direct HuR target. Furthermore, exogenous introduction of FOXQ1 can rescue cell invasive ability inhibited by HuR knockout. Taken together, HuR-FOXQ1 signaling axis is a potential target for blocking breast cancer metastasis. RNA-binding proteins had previously been considered “undruggable” due to lack of a well-defined binding pocket for target RNAs. Using high throughput screening followed by structure-based rational design and lead optimization, we have identified small molecules that inhibit HuR-mRNA interaction at nM to sub-µM potency. Our lead compound, KH-3, potently inhibits breast cancer cell growth and decreases cell invasion in vitro similar to HuR knockout, as well as increasing the expression of epithelial marker E-cadherin. FOXQ1 overexpression abolishes the effect of KH-3 on blocking metastasis in breast cancer cells, demonstrating that the HuR inhibitor KH-3 inhibits cell metastasis by blocking FOXQ1 function. Moreover, KH-3 treatment disrupts HuR-FOXQ1 interaction in RNP-IP and FOXQ1 3′-UTR luciferase reporter assays. In vivo efficacy studies show that KH-3 not only exhibits potent antitumor efficacy in orthotopic xenograft models of breast cancer, but also efficiently blocks lung metastasis in experimental metastatic cancer model. In conclusion, we identified a potent and specific small molecule disrupter of HuR-FOXQ1 interaction for potential novel anti-metastatic therapy of breast cancer with HuR overexpression.

Citation Format: Xiaoqing Wu, Gulhumay Gardashova, Lan Lan, Yu Zhan, Jiajun Liu, Dan A. Dixon, Jeffrey Aubé, Danny R. Welch, Liang Xu. Blocking breast cancer metastasis by targeting HuR-FOXQ1 signaling axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 867.

NGF reprograms metastatic melanoma to a bipotent glial-melanocyte neural crest-like precursor

Melanoma pathogenesis from normal neural crest-derived melanocytes is often fatal due to aggressive cell invasion throughout the body. The identification of signals that reprogram de-differentiated, metastatic melanoma cells to a less aggressive and stable phenotype would provide a novel strategy to limit disease progression. In this study, we identify and test the function of developmental signals within the chick embryonic neural crest microenvironment to reprogram and sustain the transition of human metastatic melanoma to a neural crest cell-like phenotype. Results reveal that co-culture of the highly aggressive and metastatic human melanoma cell line C8161 upregulate a marker of melanosome formation (Mart-1) in the presence of embryonic day 3.5 chick trunk dorsal root ganglia. We identify nerve growth factor (NGF) as the signal within this tissue driving Mart-1 re-expression and show that NGF receptors trkA and p75 cooperate to induce Mart-1 re-expression. Furthermore, Mart-1 expressing C8161 cells acquire a gene signature of poorly aggressive C81-61 cells. These data suggest that targeting NGF signaling may yield a novel strategy to reprogram metastatic melanoma toward a benign cell type.

Summary: We identify and test the function of nerve growth factor to reprogram human metastatic melanoma cells to a less aggressive phenotype. This article has an associated First Person interview with the first author of the paper as part of the supplementary information.

Chloroquine-Inducible Par-4 Secretion Is Essential for Tumor Cell Apoptosis and Inhibition of Metastasis

The induction of tumor suppressor proteins capable of cancer cell apoptosis represents an attractive option for the re-purposing of existing drugs. We report that the anti-malarial drug, chloroquine (CQ), is a robust inducer of Par-4 secretion from normal cells in mice and cancer patients in a clinical trial. CQ-inducible Par-4 secretion triggers paracrine apoptosis of cancer cells and also inhibits metastatic tumor growth. CQ induces Par-4 secretion via the classical secretory pathway that requires the activation of p53. Mechanistically, p53 directly induces Rab8b, a GTPase essential for vesicle transport of Par-4 to the plasma membrane prior to secretion. Our findings indicate that CQ induces p53- and Rab8b-dependent Par-4 secretion from normal cells for Par-4-dependent inhibition of metastatic tumor growth.

Mitochondrial Haplotype Alters Mammary Cancer Tumorigenicity and Metastasis in an Oncogenic Driver-Dependent Manner

Using a novel mouse model, a mitochondrial-nuclear exchange model termed MNX, we tested the hypothesis that inherited mitochondrial haplotypes alter primary tumor latency and metastatic efficiency. Male FVB/N-Tg(MMTVneu)202Mul/J (Her2) transgenic mice were bred to female MNX mice having FVB/NJ nuclear DNA with either FVB/NJ, C57BL/6J, or BALB/cJ mtDNA. Pups receiving the C57BL/6J or BALB/cJ mitochondrial genome (i.e., females crossed with Her2 males) showed significantly (P < 0.001) longer tumor latency (262 vs. 293 vs. 225 days), fewer pulmonary metastases (5 vs. 7 vs. 15), and differences in size of lung metastases (1.2 vs. 1.4 vs. 1.0 mm diameter) compared with FVB/NJ mtDNA. Although polyoma virus middle T-driven tumors showed altered primary and metastatic profiles in previous studies, depending upon nuclear and mtDNA haplotype, the magnitude and direction of changes were not the same in the HER2-driven mammary carcinomas. Collectively, these results establish mitochondrial polymorphisms as quantitative trait loci in mammary carcinogenesis, and they implicate distinct interactions between tumor drivers and mitochondria as critical modifiers of tumorigenicity and metastasis. Cancer Res; 77(24); 6941-9. ©2017 AACR.

Astrocytes promote progression of breast cancer metastases to the brain via a KISS1-mediated autophagy

Formation of metastases, also known as cancer dissemination, is an important stage of breast cancer (BrCa) development. KISS1 expression is associated with inhibition of metastases development. Recently we have demonstrated that BrCa metastases to the brain exhibit low levels of KISS1 expression at both mRNA and protein levels. By using multicolor immunofluorescence and coculture techniques here we show that normal adult astrocytes in the brain are capable of promoting metastatic transformation of circulating breast cancer cells localized to the brain through secretion of chemokine CXCL12. The latter was found in this study to downregulate KISS1 expression at the post-transcriptional level via induction of microRNA-345 (MIR345). Furthermore, we demonstrated that ectopic expression of KISS1 downregulates ATG5 and ATG7, 2 key modulators of autophagy, and works concurrently with autophagy inhibitors, thereby implicating autophagy in the mechanism of KISS1-mediated BrCa metastatic transformation. We also found that expression of KISS1 in human breast tumor specimens inversely correlates with that of MMP9 and IL8, implicated in the mechanism of metastatic invasion, thereby supporting the role of KISS1 as a potential regulator of BrCa metastatic invasion in the brain. This conclusion is further supported by the ability of KISS1, ectopically overexpressed from an adenoviral vector in MDA-MB-231Br cells with silenced expression of the endogenous gene, to revert invasive phenotype of those cells. Taken together, our results strongly suggest that human adult astrocytes can promote brain invasion of the brain-localized circulating breast cancer cells by upregulating autophagy signaling pathways via the CXCL12-MIR345- KISS1 axis.