Increased Lung Metastasis Research Articles

Abstract A020: Elevated extracellular glucose level in tumor microenvironment by hyperglycemia increases glycolysis rate, stiffness, contractility, and motility of breast cancer cells through the cAMP-RhoA-Rock and AMPK-YAP-RhoA axes to promote metastasis

Abstract Glucose is a preferred nutrient for most cells, including cancer cells. The tumor microenvironment is both hypoxic and hypoglycemic. Glucose levels in tumors are ten times lower than in normal tissues due to poor vascularization and high glucose consumption by cancer cells, which adapt to hypoglycemia. Obesity, often accompanied by hyperglycemia, hyperinsulinemia, and hypertriglyceridemia, is linked to increased breast cancer metastasis. High extracellular glucose levels have been shown to promote cancer cell motility, though the mechanisms remain unclear. Given cancer cells' reliance on aerobic glycolysis (the Warburg effect), we hypothesized that hyperglycemia in obesity promotes cancer metastasis by modulating glucose metabolism and related cell mechanics pathways. Using Triple-Negative Breast Cancer (TNBC) cells, we found that elevated extracellular glucose levels increase glycolysis, activating the RhoA GTPase signaling pathway. This results in greater cell stiffness and contractility, correlating with increased motility. Our unpublished data, which I will present, validate these findings in obese-TNBC mouse models and further elucidate the glycolysis-mediated activation of the RhoA-ROCK axis. We also identified a novel long-term effect of hyperglycemia in promoting metastasis via transcriptional regulation of the AMPK-YAP-RhoA axis. To confirm hyperglycemia's pro-metastatic effects, we developed two obese-TNBC mouse models using diet-induced obesity (DIO) in NSG and C57BL/6J mice with orthotopic implantation of human and mouse TNBC cells, respectively. RhoA GTPase activity was measured with a GTP-RhoA FRET sensor or pull-down assay. Cell stiffness was assessed using our innovative parallel microfiltration (PMF) assay or Atomic Force Microscopy (AFM). We disrupted glucose uptake by knocking out glucose transporter 3 (GLUT3) via CRISPR/Cas9 or using a GLUT3-selective inhibitor, G3iA. Cell motility was measured by scratch wound-healing and invasion assays. Bulk RNA-seq identified differentially expressed genes under high glucose conditions in human breast cancer cells. Our results show increased lung metastasis of breast cancer cells under hyperglycemic conditions in vivo. Besides the previously reported cAMP-RhoA-ROCK axis, we discovered the glycolysis-AMPK-YAP axis also regulates RhoA-ROCK activity transcriptionally. GLUT3 inhibition activated AMPK, reduced F-actin levels via the AMPK-VASP axis, and decreased non-muscle myosin activity through the AMPK-YAP-RhoA axis. These changes in cell mechanics correlated with reduced motility. Our study suggests that targeting glucose metabolism and cell mechanics could be a novel approach to inhibit cancer metastasis, particularly in obese patients. Citation Format: Tae-Hyung Kim, Aadil Q Bhat, Jun-Yong Choe, Donghoon Yoon. Elevated extracellular glucose level in tumor microenvironment by hyperglycemia increases glycolysis rate, stiffness, contractility, and motility of breast cancer cells through the cAMP-RhoA-Rock and AMPK-YAP-RhoA axes to promote metastasis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A020.

55 Influence of gender on immunosurveillance in a novel mouse model of clear cell renal cell carcinoma

Abstract Background Renal Cell Carcinoma (RCC) is a cancer that exhibits sex dimorphism. Males have twice the incidence rate of their female counterparts and more than twice the mortality rate. They frequently present with larger, higher-grade tumors, greater metastatic spread, and earlier diagnosis of disease. Many hormonal, genetic, and environmental reasons have been explored, however a considerable amount of uncertainty remains. Methods Here, we explored the immunologic differences using a novel syngeneic mouse model of ccRCC. Tumors were orthotopically implanted by sub-renal capsular injection in immunocompetent WT C57Bl/6 and immunodeficient mice NOD/Scid/Gamma (NSG) mice, and tumor growth was longitudinally monitored using ultrasound imaging. At necropsy, liver and lung metastases were quantified and immune populations in the tumor and peripheral blood were analyzed by flow cytometry. Results In the immune-competent model, female mice had lower tumor penetrance as well as delayed tumor growth compared to male mice. In contrast, in the immune-deficient model female mice had similar tumor penetrance and growth rates as males suggesting that the female immune system may be protective against tumor development. No metastases were seen in either sex in the immune-competent model, whereas both lung and liver masses were found in the immune-deficient model suggesting the immune system is critical for restricting metastatic development. Interestingly, increased lung metastases were observed in females compared with male counterparts in NSG mice, suggesting that perhaps hormonal or other non-adaptive immunity-mediated mechanisms can promote metastatic seeding into the lungs. Flow cytometry characterization revealed higher peripheral B- and T-cells in females, with a higher CD8/CD4 T-cell ratio. Tumors from females had more activated and cytotoxic CD8 T cells and were more frequently metastatic to the lung compared to male mice. Conclusions Our findings suggest sex-related immunologic differences in immunosurveillance and metastatic tropism that warrants further interrogation. DOD CDMRP Funding: yes

Novel Inhibition of Central Carbon Metabolism Pathways by Rac and CDC42 inhibitor MBQ167 and Paclitaxel.

Triple negative breast cancer (TNBC) represents a therapeutic challenge in which standard chemotherapy is limited to paclitaxel. MBQ167, a clinical stage small molecule inhibitor that targets Rac and Cdc42, inhibits tumor growth and metastasis in mouse models of TNBC. Herein, we investigated the efficacy of MBQ167 in combination with paclitaxel in TNBC preclinical models, as a prelude to safety trials of this combination in patients with advanced breast cancer. Individual MBQ167 or combination therapy with paclitaxel was more effective at reducing TNBC cell viability and increasing apoptosis compared with paclitaxel alone. In orthotopic mouse models of human TNBC (MDA-MB231 and MDA-MB468), individual MBQ167, paclitaxel, or the combination reduced mammary tumor growth with similar efficacy, with no apparent liver toxicity. However, paclitaxel single agent treatment significantly increased lung metastasis, whereas MBQ167, single or combined, reduced lung metastasis. In the syngeneic 4T1/BALB/c model, combined MBQ167 and paclitaxel decreased established lung metastases by ∼80%. To determine the molecular basis for the improved efficacy of the combined treatment on metastasis, 4T1 tumor extracts from BALB/c mice treated with MBQ167, paclitaxel, or the combination were subjected to transcriptomic analysis. Gene set enrichment identified specific downregulation of central carbon metabolic pathways by the combination of MBQ167 and paclitaxel but not individual compounds. Biochemical validation, by immunoblotting and metabolic Seahorse analysis, shows that combined MBQ167 and paclitaxel reduces glycolysis. This study provides a strong rationale for the clinical testing of MBQ167 in combination with paclitaxel as a potential therapeutic for TNBC and identifies a unique mechanism of action.

Extracellular Vesicles Containing circMYBL1 Induce CD44 in Adenoid Cystic Carcinoma Cells and Pulmonary Endothelial Cells to Promote Lung Metastasis.

Adenoid cystic carcinoma (ACC) is a rare malignant epithelial neoplasm that arises in secretory glands and commonly metastasizes to the lungs. MYBL1 is frequently overexpressed in ACC and has been suggested to be a driver of the disease. In this study, we identified a circular RNA (circRNA) derived from MYBL1 pre-mRNA that was accompanied by the overexpression of MYBL1 in ACC. Overexpression of circMYBL1 was correlated with increased lung metastasis and poor overall survival in patients with ACC. Ectopic circMYBL1 overexpression promoted malignant phenotypes and lung metastasis of ACC cells. Mechanistically, circMYBL1 formed a circRNA-protein complex with CCAAT enhancer-binding protein β (CEBPB), which inhibited ubiquitin-mediated degradation and promoted nuclear translocation of CEBPB. In the nucleus, circMYBL1 increased the binding of CEBPB to the CD44 promoter region and enhanced its transcription. In addition, circMYBL1 was enriched in small extracellular vesicles (sEV) isolated from the plasma of patients with ACC. Treatment with sEVs containing circMYBL1 in sEVs enhanced prometastatic phenotypes of ACC cells, elevated the expression of CD44 in human pulmonary microvascular endothelial cells (HPMEC), and enhanced the adhesion between HPMECs and ACC cells. Moreover, circMYBL1 encapsulated in sEVs increased the arrest of circulating ACC cells in the lung and enhanced lung metastatic burden. These data suggest that circMYBL1 is a tumor-promoting circRNA that could serve as a potential biomarker and therapeutic target for ACC. Significance: circMYBL1 stabilizes CEBPB and upregulates CD44 to promote adhesion between cancer cells and endothelial cells and enables lung metastasis of adenoid cystic carcinoma, suggesting that inhibition of this axis could improve patient outcomes.

Tumor Cell-Associated IL-1α Affects Breast Cancer Progression and Metastasis in Mice through Manipulation of the Tumor Immune Microenvironment.

IL-1α is a dual function cytokine that affects inflammatory and immune responses and plays a pivotal role in cancer. The effects of intracellular IL-1α on the development of triple negative breast cancer (TNBC) in mice were assessed using the CRISPR/Cas9 system to suppress IL-1α expression in 4T1 breast cancer cells. Knockout of IL-1α in 4T1 cells modified expression of multiple genes, including downregulation of cytokines and chemokines involved in the recruitment of tumor-associated pro-inflammatory cells. Orthotopical injection of IL-1α knockout (KO) 4T1 cells into BALB/c mice led to a significant decrease in local tumor growth and lung metastases, compared to injection of wild-type 4T1 (4T1/WT) cells. Neutrophils and myeloid-derived suppressor cells were abundant in tumors developing after injection of 4T1/WT cells, whereas more antigen-presenting cells were observed in the tumor microenvironment after injection of IL-1α KO 4T1 cells. This switch correlated with increased infiltration of CD3+CD8+ and NKp46+cells. Engraftment of IL-1α knockout 4T1 cells into immunodeficient NOD.SCID mice resulted in more rapid tumor growth, with increased lung metastasis in comparison to engraftment of 4T1/WT cells. Our results suggest that tumor-associated IL-1α is involved in TNBC progression in mice by modulating the interplay between immunosuppressive pro-inflammatory cells vs. antigen-presenting and cytotoxic cells.

Abstract 6994: MerTK drives proliferation and metastasis activity in triple negative breast cancer

Abstract Triple negative breast cancer (TNBC) is characterized by the absence of estrogen, progesterone, and HER2 receptors. It exhibits a higher level of aggressiveness compared to other types of breast cancer, with a greater likelihood of recurrence following standard treatments such as surgery, chemotherapy, and radiation. Despite limited FDA-approved targeted therapies for TNBC, there is an ongoing need for additional molecular targeting agents.Our investigation focused on the role of the receptor tyrosine kinase MerTK and its impact on proliferation and invasion/metastatic potential. Immunohistochemistry analysis revealed that approximately 86% (128/148) expressed varying levels of MerTK in human TNBC samples, whereas approximately 50% (23/47) of TNBC patient-derived xenografts (PDX) expressed MerTK. Additionally, three established TNBC cell lines (BT549, MDAMB231, and MDAMB436) exhibited elevated MerTK expression levels.To further explore the role of MerTK in TNBC, we stably overexpressed MerTK in human TNBC cell lines SUM102 and SUM159, which naturally have low MerTK levels. The results demonstrated that MerTK overexpression led to increases in proliferative potential, robust in vivo tumor growth, heightened migration/invasion potential, and increased lung metastasis. NanoString nCounter analysis of MerTK-overexpressing SUM102 cells (SUM102-MerTK) revealed upregulation of several signaling pathways, including PI3k-Akt, PDGF, and Myc, ultimately driving cell cycle progression, reducing apoptosis, and enhancing cell survival in TNBC.Further investigation using a cytokine array showed increased endoglin production in SUM102-MerTK cells compared to vector control cells. This suggested that MerTK might be creating a conducive environment for increased proliferative and metastatic activity via elevated endoglin expression in TNBC. To ascertain the role of endoglin in increase proliferation and/or invasion potential, we knocked out endoglin in SUM102-MerTK cells. While endoglin knockout SUM102-MerTK cells exhibited similar growth to SUM102-MerTK cells, the number of lung metastases was significantly impacted, indicating that MerTK regulates invasion and metastasis through endoglin in TNBC. Collectively, our data suggests that MerTK regulates a unique proliferative signature allowing for robust tumor growth and increased metastatic potential through endoglin regulation. This suggests that targeting MerTK and endoglin simultaneously may be a viable approach for TNBC patients. Citation Format: Christine Glitchev, Mari Iida, Bridget E. Crossman, Kourtney L. Kostecki, Carlene A. Kranjac, Jillian M. Adams, Peng Liu, Irene Ong, David T. Yang, Irene Kang, Ravi Salgia, Deric L. Wheeler. MerTK drives proliferation and metastasis activity in triple negative breast cancer [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 6994.

Abstract 5517: Chronic stress causes metastasis via neutrophil-mediated changes to the microenvironment

Abstract Chronic stress is associated with increased risk of metastasis and poor survival in cancer patients, yet the reasons are unclear. We show that chronic stress increased lung metastasis from disseminated cancer cells 2- to 4-fold in mice. Chronic stress significantly altered the lung microenvironment, with fibronectin accumulation, reduced T cell infiltration, and increased neutrophil infiltration. Depleting neutrophils abolished stress-induced metastasis, indicating their critical role. Chronic stress shifted neutrophils’ normal circadian rhythm, and, via glucocorticoid release, caused increased neutrophil extracellular trap (NET) formation. Importantly, in mice with neutrophil-specific glucocorticoid receptor deletion, chronic stress failed to increase NETs and metastasis. Furthermore, digesting NETs with deoxyribonuclease (DNase) I prevented chronic stress-induced metastasis. Together, our data show that glucocorticoids released during chronic stress cause NET formation and establish a metastasis-promoting microenvironment. Therefore, NETs could be targets for preventing metastatic recurrence in cancer patients, many of whom will experience chronic stress due to their disease. Citation Format: Xue-Yan He, Yuan Gao, David Ng, Evdokia Michalopoulou, Shanu George, Jose M. Adrover, Lijuan Sun, Jean Albrengues, Juliane Daßler-Plenker, Xiao Han, Ledong Wan, Xiaoli S. Wu, Longling S. Shui, Yu-Han Huang, Bodu Liu, Chang Su, David L. Spector, Christopher R. Vakoc, Linda VanAelst, Mikala Egeblad. Chronic stress causes metastasis via neutrophil-mediated changes to the microenvironment [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 5517.

Calcitriol promotes M2 polarization of tumor-associated macrophages in 4T1 mouse mammary gland cancer via the induction of proinflammatory cytokines

Our research found that vitamin D3 (VD3) treatment increased lung metastasis in mice with 4T1 murine breast cancer (BC). This study aims to investigate the impact of VD3 on the activation of tumor-associated macrophages (TAMs) in BC. Mice bearing 4T1, E0771, 67NR BC cells, and healthy mice, were fed diets with varying VD3 contents (100—deficient, 1000—normal, and 5000 IU/kg—elevated). Some mice in the 1000 and 100 IU/kg groups received calcitriol. We studied bone metastasis and characterized TAMs and bone marrow-derived macrophages (BMDMs). 4T1 cells had higher bone metastasis potential in the 5000 IU/kg and calcitriol groups. In the same mice, an elevated tumor osteopontin level and M2 polarization of TAMs (MHCIIlow CD44high phenotype) were observed. Gene expression analysis confirmed M2 polarization of 4T1 (but not 67NR) TAMs and BMDMs, particularly in the 100 IU + cal group (increased Mrc1, Il23, and Il6). This polarization was likely due to COX-2/PGE2 induction in 4T1 calcitriol-treated cells, leading to increased proinflammatory cytokines like IL-6 and IL-23. Future studies will explore COX-2/PGE2 as a primary mediator of calcitriol-stimulated inflammation in the BC microenvironment, especially relevant for BC patients with VD3 deficiency and supplementation.

Intratumoral metastasis of sigmoid colon cancer to chromophobe renal cell carcinoma: a case report

We herein report an extremely rare case of intratumoral metastasis of colon cancer to chromophobe renal cell carcinoma. A 71-year-old woman was diagnosed with lung metastasis of sigmoid colon cancer and underwent sigmoid colon resection with D3 lymph node dissection. Preoperative contrast-enhanced computed tomography (CT) revealed a left renal tumor; however, colon resection was prioritized, and the renal tumor was placed under observation. Two years later, CT revealed enlargement of the left renal tumor, and laparoscopic partial left nephrectomy was performed 1 month later. Histopathologic examination showed that the resected renal tumor was a chromophobe renal cell carcinoma with intratumoral metastasis of colon cancer to the renal tumor center, and adjuvant chemotherapy with bevacizumab plus SOX (L-OHP + S-1) was initiated. Because of severe chemotherapy-induced fatigue and nausea, the patient was switched to bevacizumab + S-1. However, the patient’s nausea did not improve after this change, and postoperative adjuvant chemotherapy was discontinued at the patient’s request 4 months after the partial nephrectomy. Two months after discontinuation of chemotherapy, CT showed no renal recurrence; however, increased lung metastases and a new bone metastasis in the left sciatic bone were observed. Palliative treatment was then initiated because of severe adverse events that made it difficult to continue treatment. In patients who have multiple cancers and an increase in renal tumor size, the possibility of intratumoral metastasis to the renal tumor should be considered.

USP22 overexpression fails to augment tumor formation in MMTV-ERBB2 mice but loss of function impacts MMTV promoter activity.

The Ubiquitin Specific Peptidase 22 (USP22), a component of the Spt-Ada-Gcn5 Acetyltransferase (SAGA) histone modifying complex, is overexpressed in multiple human cancers, but how USP22 impacts tumorigenesis is not clear. We reported previously that Usp22 loss in mice impacts execution of several signaling pathways driven by growth factor receptors such as erythroblastic oncogene B b2 (ERBB2). To determine whether changes in USP22 expression affects ERBB2-driven tumorigenesis, we introduced conditional overexpression or deletion alleles of Usp22 into mice bearing the Mouse mammary tumor virus-Neu-Ires-Cre (MMTV-NIC) transgene, which drives both rat ERBB2/NEU expression and Cre recombinase activity from the MMTV promoter resulting in mammary tumor formation. We found that USP22 overexpression in mammary glands did not further enhance primary tumorigenesis in MMTV-NIC female mice, but increased lung metastases were observed. However, deletion of Usp22 significantly decreased tumor burden and increased survival of MMTV-NIC mice. These effects were associated with markedly decreased levels of both Erbb2 mRNA and protein, indicating Usp22 loss impacts MMTV promoter activity. Usp22 loss had no impact on ERBB2 expression in other settings, including MCF10A cells bearing a Cytomegalovirus (CMV)-driven ERBB2 transgene or in human epidermal growth factor receptor 2 (HER2)+ human SKBR3 and HCC1953 cells. Decreased activity of the MMTV promoter in MMTV-NIC mice correlated with decreased expression of known regulatory factors, including the glucocorticoid receptor (GR), the progesterone receptor (PR), and the chromatin remodeling factor Brahma-related gene-1 (BRG1). Together our findings indicate that increased expression of USP22 does not augment the activity of an activated ERBB2/NEU transgene but impacts of Usp22 loss on tumorigenesis cannot be assessed in this model due to unexpected effects on MMTV-driven Erbb2/Neu expression.

A SUCCESSFUL CASE OF LYMPHATIC EMBOLIZATION IN A PATIENT WITH PROLONGED LYMPHATIC LEAKAGE AFTER CYTOREDUCTIVE NEPHRECTOMY FOR METASTATIC RENAL CANCER

A 57-years-old woman was referred to our urological department due to a 7.2-cm tumor in the left kidney, detected on computed tomography (CT). Dynamic CT of the kidney confirmed the diagnosis of left renal cancer, with lung metastasis (cT2aN0M1). The patient had a poor prognosis (IMDC classification), given the following risk factors: Time from initial diagnosis to initiation of systemic therapy < 1year, hemoglobin of 8.4 g/dL, calcium of 10.7 mg/dL, and platelet of 74.2×104/mm3. Laparoscopic left radical nephrectomy was performed before systemic drug treatment because the solitary lung metastasis was relatively small (10 mm) and the patient had symptoms of hematuria and fever. The pathological diagnosis was a clear cell carcinoma with renal sinus invasion (pT3a). Four days postoperatively, the patient developed lymphatic leakage, and was unresponsive to diet and conservative treatment. Lymphatic embolization with iodized poppy oil fatty acid ethyl ester was performed 22 days postoperatively. Contrast material leakage from the left renal hilar lymph node was observed before embolization. Post-embolization CT confirmed no contrast leakage. The patient resumed oral feeding on the 28th postoperative day, and the drain was successfully removed the next day. She was discharged on the 35th postoperative day. On follow-up, increased lung metastases were observed on CT. She was treated with the combination of ipilimumab and nivolumab. After one course of treatment, a CT scan showed a further increased in lung metastases (RECIST: PD). Thus, she was initiated on cabozantinib monotherapy. Lymphatic embolization may be a safe and effective treatment for lymphatic leakage that does not improve with conservative treatment.

Abstract 62: Untangling the connection between stress and metastatic breast cancer

Abstract There is emerging evidence that exposure to chronic stress is associated with increased risk of metastasis and poor survival in cancer patients. However, the underlying molecular and cellular mechanisms responsible for the effects of stress on tumor progression remain unclear. To determine how stress promotes metastasis, we established new mouse models in which multiple chronic stress exposure promoted breast cancer metastasis to the lungs. We found that chronic stress generates a pro-metastatic lung microenvironment with e.g., reduced T cell infiltration and increased extracellular matrix (ECM) deposition and neutrophil infiltration. Among them, neutrophils were required for these changes as their depletion abolished the pro-metastatic effects of stress and normalized the lung tumor microenvironment. Mechanistically, we analyzed neutrophils from chronically stressed mice and identified dramatically altered transcriptomes, including increased expression of several glucocorticoid receptor regulated genes. Phenotypically, neutrophils from stress exposed mice exhibited increased ROS production, and an increased ability to inhibit T cell activation and to form spontaneous neutrophil extracellular traps (NETs). The stress-associated changes to neutrophils were dependent on glucocorticoid receptor (GR) signaling as neutrophil-specific GR knockout mice showed no increase in NET-formation, a normalized lung microenvironment and no increase in lung metastasis upon stress exposure. Among the changes in the neutrophils caused by stress exposure, we found that the formation of pro-metastatic NETs was critical as directly digesting NETs with DNase I prevented stress-induced metastasis and normalized the lung microenvironment. In sum, this work shows that chronic stress exposure causes a glucocorticoid-mediated increase in NET formation and that NETs are critical drivers in the establishment of a stress-induced, metastasis-promoting microenvironment. Targeting NETs could be an important strategy to prevent metastatic recurrence in cancer patients, many of whom will experience stress due to their cancer diagnosis and subsequent treatments. Citation Format: Xue-Yan He, David Ng, Yuan Gao, Evdokia Michalopoulou, Shanu George, Jose M. Adrover, Lijuan Sun, Jean Albrengues, Ledong Wan, Xiao Han, Christopher Vakoc, Linda Van Aelst, Mikala Egeblad. Untangling the connection between stress and metastatic breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 62.

Abstract 3743: circPMS1 is a pro-metastatic circular RNA in melanoma

Abstract Deregulated gene expression is a major driver of melanoma metastasis, a process that results in the majority of melanoma-related deaths. Importantly, these alterations are not limited to protein-coding mRNAs, but also include noncoding RNAs. Despite many recent studies implicating circular RNAs (circRNAs) in cancer development, it is unknown if their deregulation contributes to melanoma metastasis. To identify circRNAs with putative roles in melanomagenesis, we performed RNA sequencing on a panel of melanoma and melanocyte cell lines. 21 differentially expressed circRNAs were validated by qPCR and Sanger sequencing of the backsplice junction. Further analyses of the ratio of the circular and cognate linear RNA transcripts and expression in a larger panel of cell lines identified circPMS1 as a circRNA that is upregulated in melanoma through enhanced backsplicing of the linear PMS1 mRNA. Using transposon-mediated delivery, we examined the effects of stable circPMS1 overexpression on melanoma cells. While proliferation and focus formation were not impacted, migration and invasion were enhanced by circPMS1. Moreover, tail vein injection of circPMS1 overexpressing melanoma cells increased lung metastasis. In addition to this transplant model, we generated the first genetically engineered mouse model of melanoma overexpressing a pro-tumorigenic circRNA. These mice are currently being analyzed. Mechanistically, we find that circularization is required for the pro-migratory effects of the circPMS1 overexpression construct. Additionally, circPMS1 harbors the canonical PMS1 start codon, a predicted ORF spanning over the backsplice junction, and a predicted IRES sequence. Indeed, inserting a flag-tag in the overexpression construct revealed circPMS1 to be translated into a truncated 25kD PMS1 protein as well as a 20kD protein likely arising from an in-frame downstream start codon. Importantly, these truncated circPMS1 proteins are endogenously expressed and increased in melanoma compared to melanocytes while the full-length PMS1 protein is evenly expressed. These findings suggest that circPMS1 promotes melanoma metastasis, at least in part, by coding for truncated circPMS1 proteins. Further work will establish the functions of the circPMS1-encoded proteins and their roles in driving melanoma progression and metastasis. Citation Format: Nicol Mecozzi, Olga Vera, Florian Karreth. circPMS1 is a pro-metastatic circular RNA in melanoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3743.

Abstract B036: Platelets promote in vitro osteosarcoma cell migration and in vivo metastatic lung seeding

Abstract Osteosarcoma (OS) is the most common primary bone cancer worldwide where it mainly affects adolescents. Metastatic OS has a 20% survival rate and treatment options remain poor, thus understanding mechanisms that contribute to OS metastasis is critical for improved patient outcomes. Platelets, commonly recognized for their role in hemostasis, have been shown to promote metastasis in several cancer models. However, most previous studies investigating platelet contributions to metastasis have focused on carcinomas while their role in osteosarcoma remains poorly understood. Previous studies by our lab have shown that platelet interactions with breast cancer cells resulted in increased migration in vitro and increased lung metastases in vivo. Thus, we hypothesized that OS cell migration will be enhanced in the presence of platelets, and that platelet depletion in vivo will inhibit OS lung seeding. Cell suspensions of SaOs2 and MG63.3 cells in serum free media were fluorescently stained and seeded, in triplicates, in the top chamber of an 8um pore Fluoroblock migration assay wells. In the bottom chamber, media and either Tyrode’s buffer or 1.5x106 isolated human platelets were added. The presence of platelets resulted in a 3.5- and 4.6-fold increase of migrated MG63.3 and SaOs2 cells respectively. For in vivo analysis, cohorts of eight-week-old, male Nod Scid-Gamma (NSG), Nod Scid, and Nude mice were randomly assigned to either the control or platelet depletion group. Mice were depleted of platelets by administration of Anti-Platelet glycoprotein Ib alpha (GPIbα) antibody and, 5x105 GFP transduced MG63.3 cells were injected via tail vein. 24 hrs later, the mice were euthanized, and lungs were collected and microscopically imaged. Platelet depletion in NSG mice resulted in a 48% reduction in MG63.3 lung seeding compared to the isotype control recipient mice. This result was more dramatic in the less immunocompromised Nude and Nod Scid mice with a 61% and 87% reduction of MG63.3 lung seeding in the platelet depleted mice respectively. Finally, RNAseq and was performed on seven OS cell lines co-cultured with isolated mouse platelets, and alterations in gene expression were compared to control cells. Gene Enrichment Set Analysis (GSEA) of the data indicated that platelet co-incubation significantly upregulated pathways related to inflammatory responses, Tumor Necrosis Factor (TNF)-a signaling, and Interleukin (IL)-6 signaling. These results suggest that platelet secreted factors facilitate OS cell migration in vitro while an immune dependent mechanism is involved in the role of platelets in the in vivo lung seeding of OS cells. Citation Format: Olivia K. Travis, Ruishan Wang, Myriam Labelle. Platelets promote in vitro osteosarcoma cell migration and in vivo metastatic lung seeding [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 B036.

The role of AFAP1-AS1 in mitotic catastrophe and metastasis of triple-negative breast cancer cells by activating the PLK1 signaling pathway.

Triple-negative breast cancer (TNBC) is characterized by fast growth, high metastasis, high invasion, and a lack of therapeutic targets. Mitosis and metastasis of TNBC cells are two important biological behaviors in TNBC malignant progression. It is well known that the long noncoding RNA AFAP1-AS1 plays a crucial role in various tumors, but whether AFAP1-AS1 is involved in the mitosis of TNBC cells remains unknown. In this study, we investigated the functional mechanism of AFAP1-AS1 in targeting Polo-like Kinase 1 (PLK1) activation and participating in mitosis of TNBC cells. We detected the expression of AFAP1-AS1 in the TNBC patient cohort and primary cells by in situ hybridization (ISH), northern blot, fluorescent in situ hybridization (FISH) and cell nucleus/cytoplasm RNA fraction isolation. High AFAP1-AS1 expression was negatively correlated with overall survival (OS), disease-free survival (DFS), metastasis-free survival (MFS) and recurrence-free survival (RFS) in TNBC patients. We explored the function of AFAP1-AS1 by transwell, apoptosis, immunofluorescence (IF) and patient-derived xenograft (PDX) models in vitro and in vivo. We found that AFAP1-AS1 promoted TNBC primary cell survival by inhibiting mitotic catastrophe and increased TNBC primary cell growth, migration and invasion. Mechanistically, AFAP1-AS1 activated phosphorylation of the mitosis-associated kinase PLK1 protein. Elevated levels of AFAP1-AS1 in TNBC primary cells increased PLK1 pathway downstream gene expression, such as CDC25C, CDK1, BUB1 and TTK. More importantly, AFAP1-AS1 increased lung metastases in a mouse metastasis model. Taken together, AFAP1-AS1 functions as an oncogene that activates the PLK1 signaling pathway. AFAP1-AS1 could be used as a potential prognostic marker and therapeutic target for TNBC.

Adolescent- and adult-initiated alcohol exposure in mice differentially promotes tumorigenesis and metastasis of breast cancer.

Alcohol exposure increases the risk of breast cancer. Alcohol consumption by adolescents is a serious social and public health issue. This study investigated the impact of adolescent alcohol consumption on mammary tumorigenesis and progression and compared it to that of adult alcohol exposure in animal models. Female adolescent (5 weeks) and adult (8 weeks) MMTV-Wnt1 mice were exposed to alcohol either chronically or acutely. For chronic alcohol exposure, animals were fed a liquid diet containing 6.7% ethanol for 23 weeks. For acute exposure, animals were treated with ethanol (2.5g/kg, 25% w/v) via intraperitoneal (IP) injection for 15 days. In control animals, the tumor latency was 18.5 to 22 weeks. Both chronic and acute alcohol exposure in adolescent mice significantly shortened the tumor latency to 9.5 and 8.4 weeks, respectively. However, adult-initiated alcohol exposure had little effect on the tumor latency. Both adolescent- and adult-initiated alcohol exposure significantly increased lung metastasis. Adolescent-initiated alcohol exposure but not adult-initiated alcohol exposure increased the breast cancer stem cell population. Adolescent-initiated alcohol exposure significantly altered the proliferation of mammary epithelial cells, ductal growth, and the formation of terminal end buds in the mammary glands. Adolescent-initiated alcohol exposure but not adult-initiated alcohol exposure increased estradiol levels in the blood. Acute adolescent alcohol exposure also significantly increased blood progesterone levels. Furthermore, adolescent-initiated alcohol exposure activated PAK1 and p38γ MAPK, critical regulators of mammary tumorigenesis and aggressiveness, respectively, while adult-initiated alcohol exposure activated only p38γ MAPK. In addition, both adolescent and adult alcohol exposure significantly decreased the levels of a prognostic marker miR200b. Adolescent-initiated alcohol exposure enhanced both tumorigenesis and aggressiveness of mammary tumors, while adult-initiated alcohol exposure mainly promoted tumor metastasis. Thus, adolescent mice were more sensitive than adult mice in response to alcohol-induced tumor promotion.

Chewing Behavior Attenuates Lung-Metastasis-Promoting Effects of Chronic Stress in Breast-Cancer Lung-Metastasis Model Mice

We assessed the effects of chewing behavior on the lung-metastasis-promoting impact of chronic psychological-stress in mice. Human breast-cancer cells (MDA-MB-231) were injected into the tail vein of female nude mice. Mice were randomly divided into stress, stress-with-chewing, and control groups. We created chronic stress by placing mice in small transparent tubes for 45 min, 3 times a day for 7 weeks. Mice in the stress-with-chewing group were allowed to chew wooden sticks during the experimental period. The histopathological examination showed that chronic psychological-stress increased lung metastasis, and chewing behavior attenuated the stress-related lung metastasis of breast-cancer cells. Chewing behavior decreased the elevated level of the serum corticosterone, normalized the increased expression of glucocorticoid, and attenuated the elevated expression of adrenergic receptors in lung tissues. We also found that chewing behavior normalized the elevated expression of inducible nitric oxide synthase, 4-hydroxynonenal, and superoxide dismutase 2 in lung tissues, induced by chronic stress. The present study demonstrated that chewing behavior could attenuate the promoting effects of chronic psychological-stress on the lung metastasis of breast-cancer cells, by regulating stress hormones and their receptors, and the downstream signaling-molecules, involving angiogenesis and oxidative stress.

Artemin Promotes the Migration and Invasion of Cervical Cancer Cells through AKT/mTORC1 Signaling.

The neurotrophic factor Artemin (ARTN) is involved in tumor proliferation and metastasis. Nonetheless, ARTN's significance in cervical cancer (CC) has not been studied. In our study, we propose to investigate the biological function of ARTN in CC as well as its particular regulatory mechanism. Immunohistochemistry (IHC) was used to examine the degree of ARTN protein expression in CC patient tissue. Real-time PCR and Western blotting were performed to reveal related genes' levels in CC cells. The CCK-8 test, the colony formation assay, the wound-healing assay, and the transwell assay were utilized to determine the proliferation, migration, and invasion capabilities, respectively. To generate lung metastasis models, stable ARTN-expressing SiHa cells were injected into the caudal tail vein of mice. IHC was used to examine the protein levels in CC mice model tissues. ARTN was overexpressed in CC tissues relative to normal cervical tissues and linked positively with lymph node metastases (P=0.012) and recurrence (P=0.015) in CC patients. In vitro, ARTN overexpression promoted the proliferation, invasion, and migration of CC cells. In contrast, the consequences of depleting endogenous ARTN were the opposite. Moreover, overexpression of ARTN increased lung metastasis of CC cells in vivo and shortened the lifespan of mice models. In addition, ARTN overexpression significantly enhanced AKT phosphorylation on Ser473 and mTOR phosphorylation on Ser2448 and promoted the epithelial-mesenchymal transition (EMT) cascade. In addition, rapamycin, a selective inhibitor of mTORC1, might rescue the EMT phenotype caused by ARTN. Our findings suggested that ARTN may enhance CC metastasis through the AKT/mTORC1 pathway. ARTN is anticipated to be a novel potential therapeutic target for the treatment of CC metastases.

Abstract 5836: SMC4 promotes prostate cancer organ-specific metastasis by modifying cancer cell metabolism

Abstract Structural maintenance of chromosomes 4 (SMC4), one subunit of condensin complexes, is a key structural component of mitotic chromosomes. Accumulating evidence has suggested that SMC4 regulates prostate carcinogenesis. However, its roles on regulation of prostate cancer development remain unclear. Our previous studies showed that the expression of SMC4 is increased in highly lung-metastatic prostate cancer cells, RM1-LM, an organ-specific metastasis cell line that we developed. To investigate the function of SMC4, SMC4 gene was knockdown in RM1-LM cells by CRISPR/Cas9 system. Knockdown of SMC4 significantly diminished the cancer cell growth in RM1-LM. In addition, transwell assay results showed that SMC4 knockdown in RM1-LM suppressed the cell migration and invasion. Furthermore, we observed that SMC4 protein is important in the non-dividing phase of the cell cycle. In particular, cell cycle flow cytometry analysis indicated that SMC4 knockdown leaded to cell arrest in S phase. Finally, RM1-LM cells showed increased lung metastases compared with RM1-SMC4+/- cells in a murine model. The H&amp;E and IHC results confirmed that RM1-LM cells induced greater number of lung metastases and colonization than RM1-SMC4+/-cells, suggesting the loss of SMC4 suppressed prostate cancer metastasis. The interactome of SMC4 was uncovered through IP-MS and revealed that SMC4 may interacted with GLUT1, a key protein in glycolysis pathway. The ATP rate assay and Glycolysis rate assay illustrated a significantly metabolic switch existing in RM1-SMC4+/-cells compared with their parental cells. Collectively, our study suggested that the interaction between SMC4 and GLUT1, confirmed by Co-IP, promotes prostate cancer cells metastasis via modifying the cell metabolism. This work was supported by NSFC projects 81802949, 81773146, 81972766, 81972420, 82173336; Shenzhen Science and Technology Commission Project JCYJ20190809161811237, JCYJ2021032410424040; Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research (2017B030301018);and College students' innovative entrepreneurial training program (S202114325028) Citation Format: Wei Zhang, Xin Huang, yueming Li, yingxuan Gong, xiuzhi Li. SMC4 promotes prostate cancer organ-specific metastasis by modifying cancer cell metabolism [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 5836.

The m6A Methyltransferase METTL3-Mediated N6-Methyladenosine Modification of DEK mRNA to Promote Gastric Cancer Cell Growth and Metastasis.

Gastric cancer (GC) is the fifth most common cancer and the third deadliest cancer in the world, and the occurrence and development of GC are influenced by epigenetics. Methyltransferase-like 3 (METTL3) is a prominent RNA n6-adenosine methyltransferase (m6A) that plays an important role in tumor growth by controlling the work of RNA. This study aimed to reveal the biological function and molecular mechanism of METTL3 in GC. The expression level of METTL3 in GC tissues and cells was detected by qPCR, Western blot and immunohistochemistry, and the expression level and prognosis of METTL3 were predicted in public databases. CCK-8, colony formation, transwell and wound healing assays were used to study the effect of METTL3 on GC cell proliferation and migration. In addition, the enrichment effect of METTL3 on DEK mRNA was detected by the RIP experiment, the m6A modification effect of METTL3 on DEK was verified by the MeRIP experiment and the mRNA half-life of DEK when METTL3 was overexpressed was detected. The dot blot assay detects m6A modification at the mRNA level. The effect of METTL3 on cell migration ability in vivo was examined by tail vein injection of luciferase-labeled cells. The experimental results showed that METTL3 was highly expressed in GC tissues and cells, and the high expression of METTL3 was associated with a poor prognosis. In addition, the m6A modification level of mRNA was higher in GC tissues and GC cell lines. Overexpression of METTL3 in MGC80-3 cells and AGS promoted cell proliferation and migration, while the knockdown of METTL3 inhibited cell proliferation and migration. The results of in vitro rescue experiments showed that the knockdown of DEK reversed the promoting effects of METTL3 on cell proliferation and migration. In vivo experiments showed that the knockdown of DEK reversed the increase in lung metastases caused by the overexpression of METTL3 in mice. Mechanistically, the results of the RIP experiment showed that METTL3 could enrich DEK mRNA, and the results of the MePIP and RNA half-life experiments indicated that METTL3 binds to the 3’UTR of DEK, participates in the m6A modification of DEK and promotes the stability of DEK mRNA. Ultimately, we concluded that METTL3 promotes GC cell proliferation and migration by stabilizing DEK mRNA expression. Therefore, METTL3 is a potential biomarker for GC prognosis and a therapeutic target.