BRCA1/2 -mutated breast cancers exhibit homologous recombination deficiency (HRD), making them initially sensitive to poly(ADP-ribose) polymerase (PARP) inhibitors. However, 40-70% of patients develop resistance, necessitating combination strategies and predictive biomarkers. We first investigated approaches to overcome PARP resistance and then explored spatial microRNA (miRNA) profiling as a prognostic tool. Using the K14-Cre Brca1 f/f Trp53 f/f model with tumors that acquired PARP resistance, we evaluated PARP inhibitor combinations with either PI3K inhibition or Poly(I:C) in vivo . Both combinations improved antitumor activity compared to PARP inhibition alone. Next, to predict resistance we applied a sensitive assay that quantifies and spatially profiles miRNA expression in situ onto FFPE sections from tumors treated for 10 days using nanoliter well arrays with functionalized hydrogel posts. We developed a spatial miRNA analysis framework integrating latent Dirichlet allocation (LDA) and principal component analysis (PCA) to develop "topics" that stratify early tumors as either PARP inhibitor-sensitive or - resistant and distinguish their treatment regimens. We also incorporated immune architecture using Structural Similarity Index Measure (SSIM) maps that revealed co-localization of immune infiltration and miRNA topics. This integrative approach highlights how miRNA-based spatial analysis can predict PARP inhibitor resistance and provide a promising biomarker to inform therapeutic strategies for BRCA1/2- related breast cancers.

Tumor recurrence, which can occur many years after therapeutic intervention, represents the main challenge in clinical oncology. Clinically, this period between the “cure” of the primary tumor and its local or distal metastatic relapse is known as the “dormancy state.” Tumor dormancy has been linked to therapeutic resistance and a high metastatic potential of malignant neoplasms. During tumor immunoediting, the immune response shapes the tumor to adapt and thrive within an immunocompetent host. Epigenetic modulation is an important way by which cells can quickly regulate gene expression and respond to environmental pressures. Another way of rapid modulation can be through regulatory RNAs, such as lncRNAs which can interact at the level of transcription and translation of other molecules, such as protein-coding genes, and regulate gene expression. To better understand the molecular basis of this tumor dormancy and awakening, we established a murine immune-mediated model of awakening of dormant melanoma cells. In this model, a large number of apoptotic cells are used to generate an acute inflammation process in C57BL/6 mice that promotes a permissive environment for a sub-tumorigenic dose of viable metastatic melanoma cells grown into a fully formed tumor, that would not be formed otherwise. Our study shows that the sub-tumorigenic dose of viable cells only generates tumors in immunosuppressed (NSG) mice (100% of animals), indicating that in immunocompetent animals, the primary defense system - T and B lymphocytes, and NK cells - appears to contain it. Considering the role of epigenetic modulation in rapid cell response to the pressure of the environment, we also show that treatment with the global demethylating agent 5-aza-2’-deoxycytidine causes delay and reduction of tumor mainly through immune activation. This suggests the need for future investigations regarding the epigenetic machinery in our model. Thereby, genome-wide DNA methylome analysis was conducted (EPICarray), and differential gene expression (RNA-seq) analysis of tumors from animals treated (or not) with the demethylating agent. Differentially expressed genes are being selected for further in vitro and in vivo studies. To elucidate this model, we are carrying on assays to understand the role of acute inflammation in the awakening of melanoma dormancy by analyzing the inflammatory profile of the defense system using flow cytometry meanwhile we are conducting other in vivo experiments to better characterize our model. Now, we investigated lncRNAs that are differentially expressed in tumors of animals treated with that drug aiming for new potential biomarkers, or regulators of important immune-response protein-coding genes. All in vivo data were statistically validated using the Student's t-test. We aim to discover potential therapeutic targets with a functional role in the immune-mediated progression of melanoma. Supported by CNPq, CAPES, FAPESP Ianca R. Dias, Débora K. Alves-Fernandes, Lih Hongtao, Frank J. Slack, Gangning Liang, Miriam G. Jasiulionis. Unraveling molecular mechanisms underlying the awakening of dormant melanomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3292.

Epstein-Barr virus (EBV) infection is an established causal factor for Hodgkin lymphoma (HL). MicroRNAs (miRNAs) are master regulators of gene expression and are ideal biomarkers. We profiled the circulating expression of 42 EBV miRNAs in HL patients to determine if EBV miRNA(s) can be a noninvasive biomarker for EBV+ HL or disease severity. Plasma was obtained from 11 patients with HL in a tuberculosis and HIV-endemic setting in Cape Town, South Africa. EBV infection in HL tumor cells were confirmed using a clinical PCR assay. The expression of 42 miRNAs were measuring using a qPCR-based Mirxes ID3EALTM EBV miRNA panel. Wilcoxon test or Fisher’s test were used to compare data between two groups. Spearman’s rho was used for correlation analysis. Fold changes were calculated using the 2^-ΔΔCT method. EBV+ HL patients were significantly older (p=0.04; Table 1). No miRNA was associated with EBV or prognostic factors at FDR<0.05. Of interest, miR-BART20-3p expression was 33% lower in EBV+ patients compared to EBV- patients (p=0.052) and did not correlate with age (rho=0.39, p=0.23). MiR-BART17-3p was inversely correlated with stage (rho=-0.61, p=0.047). MiR-BART2-5p correlated with International Prognostic Score (IPS; rho=0.72, p=0.01). miR-BART14-3p was inversely correlated with Eastern Cooperative Oncology Group (ECOG) score (rho=-0.60, p=0.049). MiR-BART11-5p and miR-BART14-5p were higher in patients that reported B-symptoms (11.2-fold p=0.01 and 2.5-fold p=0.02, respectively). In contrast, MiR-BART14-3p and miR-BART17-3p were 33% and 41% lower in patients with B-symptoms (both p=0.03). No miRNA was associated with HIV. Circulating EBV miRNAs were associated with HL disease severity but not EBV status. Further investigations into these candidate miRNAs will increase our understanding of HL disease progression as well as explore the potential of these miRNAs as therapeutics or therapeutic targets. Table 1. Soo Mi Lee, Cristina S. Bogsan, Jason T. Howard, Abigail G. Wandoff, Meng-Xuan Wu, Estelle Verburgh, Maxine van der Schyff, Frank J. Slack, Yujing J. Heng, Katherine Antel. Circulating Epstein-Barr virus microRNAs associated with Hodgkin lymphoma prognosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6682.

Metastasis is the leading cause of cancer related deaths, however therapies specifically targeting metastasis are lacking and remain a dire therapeutic need in the clinic. Metastasis is a highly inefficient process that is inhibited by extracellular stress. Therefore, metastasizing cells that ultimately survive and successfully colonize distant organs must undergo molecular rewiring to mitigate stress. Wobble uridine modifications, especially 5-methoxycarbonylmethyl-2-thiouridine (mcm 5 s 2 U 34 ), have been implicated in stress response and poor prognosis of cancer patients. We use a patient derived xenograft (PDX) model of melanoma metastasis to study the role of the mcm 5 s 2 U 34 modification in the stress response of metastasizing cells. We find that upon depletion of elongator acetyltransferase complex subunit 1 (ELP1)- a component of the mcm 5 s 2 U 34 pathway on , and -codon-biased translation, migration, invasion, and metastatic burden in vivo is reduced. Further, we observe that stress granule components are enriched in a subset of codon-biased genes that are exclusively upregulated at the protein level in metastatic nodules compared to the primary tumor in our PDX model. Additionally, upon knockdown of ELP1, stress granule components have decreased protein expression with no significant change to their mRNA levels. Efficient translation, mediated by the carboxy-methylation arm of the mcm 5 s 2 U 34 modification, is required for metastasizing cancer cells to withstand stress via stress granule formation and increase survival throughout the metastatic cascade. This makes the mcm 5 s 2 U 34 machinery a potentially actionable therapeutic target, specific to metastatic disease.

Long noncoding RNAs (lncRNAs) play numerous roles in cellular biology and alterations in lncRNA expression profiles have been implicated in a variety of cancers. Here, we identify and characterize a lncRNA, TRIM28 Interacting DNA damage repair Enhancing Noncoding Transcript (TRIDENT), whose expression is induced upon epithelial growth factor receptor (EGFR) activation, and which exerts pro-oncogenic functions in EGFR-driven non-small cell lung cancer. Knocking down TRIDENT leads to decreased tumor-cell proliferation in both in vitro and in vivo model systems and induces sensitization to chemotherapeutic drugs. Using ChIRP-MS analysis we identified TRIM28 as a protein interactor of TRIDENT. TRIDENT promotes phosphorylation of TRIM28 and knocking down TRIDENT leads to accumulation of DNA damage in cancer cells via decreased TRIM28 phosphorylation. Altogether, our results reveal a molecular pathway in which TRIDENT regulates TRIM28 phosphorylation to promote tumor cell growth and drug resistance. Our findings suggest that TRIDENT can be developed as a biomarker or therapeutic target for EGFR mutant non-small cell lung cancer.

Oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV), an etiological agent of Kaposi's sarcoma and primary effusion lymphoma, employs a biphasic life cycle consisting of latency and lytic replication to achieve lifelong infection. Despite its essential role in KSHV persistence and tumorigenicity, much remains unknown about how KSHV lytic reactivation is regulated. Leveraging high-throughput transcriptomics, we identify microRNA-31-5p (miR-31-5p) as a key regulator of KSHV lytic reactivation capable of restricting KSHV entry into the lytic replication cycle. Ectopic expression of miR-31-5p impairs KSHV lytic gene transcription and production of lytic viral proteins, culminating in dramatic reduction of infectious virion production during KSHV reactivation. miR-31-5p overexpression also markedly reduces the expression of critical viral early genes, including the master regulator of the latent-lytic switch, KSHV replication and transcription activator (RTA) protein. Through mechanistic studies, we demonstrate that miR-31-5p represses KSHV lytic reactivation by directly targeting the KH domain protein KHDRBS3, an RNA-binding protein known to regulate RNA processing including alternative splicing. Our study highlights KHDRBS3 as an essential proviral host factor that is key to the successful completion of KSHV lytic replication and suggests its novel function in viral lytic gene transcription during KSHV reactivation. Taken together, these findings reveal a previously unrecognized role for the miR-31-5p/KHDRBS3 axis in regulating the KSHV latency-lytic replication switch and provide insights into gene expression regulation of lytic KSHV, which may be leveraged for lytic cycle-targeted therapeutic strategies against KSHV-associated malignancies.

The tumor microenvironment (TME) is a heterogeneous ecosystem containing cancer cells, immune cells, stromal cells, cytokines, and chemokines which together govern tumor progression and response to immunotherapies. Methyltransferase-like 3 (METTL3), a core catalytic subunit for RNA N6-methyladenosine (m6A) modification, plays a crucial role in regulating various physiological and pathological processes. Whether and how METTL3 regulates the TME and anti-tumor immunity in non-small-cell lung cancer (NSCLC) remain poorly understood. Here, we report that METTL3 elevates expression of pro-tumorigenic chemokines including CXCL1, CXCL5, and CCL20, and destabilizes PD-L1 mRNA in an m6A-dependent manner, thereby shaping a non-inflamed TME. Thus, inhibiting METTL3 reprograms a more inflamed TME that renders anti-PD-1 therapy more effective in several murine lung tumor models. Clinically, NSCLC patients who exhibit low-METTL3 expression have a better prognosis when receiving anti-PD-1 therapy. Collectively, our study highlights targeting METTL3 as a promising strategy to improve immunotherapy in NSCLC patients.

The landscape of non-coding mutations in cancer progression and immune evasion is largely unexplored. Here, we identify transcrptome-wide somatic and germline 3' untranslated region (3'-UTR) variants from 375 gastric cancer patients from The Cancer Genome Atlas. By performing gene expression quantitative trait loci (eQTL) and immune landscape QTL (ilQTL) analysis, we discover 3'-UTR variants with cis effects on expression and immune landscape phenotypes, such as immune cell infiltration and T cell receptor diversity. Using a massively parallel reporter assay, we distinguish between causal and correlative effects of 3'-UTR eQTLs in immune-related genes. Our approach identifies numerous 3'-UTR eQTLs and ilQTLs, providing a unique resource for the identification of immunotherapeutic targets and biomarkers. A prioritized ilQTL variant signature predicts response to immunotherapy better than standard-of-care PD-L1 expression in independent patient cohorts, showcasing the untapped potential of non-coding mutations in cancer.

Aging is associated with decreased health span, and despite the recent advances made in understanding the mechanisms of aging, no antiaging drug has been approved for therapy. Therefore, strategies to promote a healthy life in aging are desirable. Previous work has shown that chronic treatment with extracellular vesicles (EVs) from young mice prolongs lifespan in old mice, but the mechanism of action of this effect on liver metabolism is not known. Here we investigated the role of treatment with EVs derived from young sedentary (EV-C) or exercised (EV-EX) mice in the metabolism of old mice and aimed to identify key youthful-associated microRNA (miRNA) cargos that could promote healthy liver function. We found that aged mice treated with either EV-C or EV-EX had higher insulin sensitivity, higher locomotor activity resulting in longer distance traveled in the cage, and a lower respiratory exchange ratio compared to mice treated with EVs from aged mice (EV-A). In the liver, treatment with young-derived EVs reduced aging-induced liver fibrosis. We identified miR-30c in the EVs as a possible youth-associated miRNA as its level was higher in circulating EVs of young mice. Treatment of aged mice with EVs transfected with miR-30c mimic reduced stellate cell activation in the liver and reduced fibrosis compared to EV-negative control by targeting Foxo3. Our results suggest that by delivering juvenile EVs to old mice, we can improve their liver health. Moreover, we identified miR-30c as a candidate for antiaging liver therapy.

ABSTRACT:Hematological malignancies such as Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B-cell lymphoma (DLBCL) cause significant morbidity in humans. A substantial number of these lymphomas, particularly HL and DLBCLs have poorer prognosis because of their association with Epstein-Barr virus (EBV). Our earlier studies have shown that EBV-encoded nuclear antigen (EBNA2) upregulates programmed cell death ligand 1 in DLBCL and BLs by downregulating microRNA-34a. Here, we investigated whether EBNA2 affects the inducible costimulator (ICOS) ligand (ICOSL), a molecule required for efficient recognition of tumor cells by T cells through the engagement of ICOS on the latter. In virus-infected and EBNA2-transfected B-lymphoma cells, ICOSL expression was reduced. Our investigation of the molecular mechanisms revealed that this was due to an increase in microRNA-24 (miR-24) by EBNA2. By using ICOSL 3' untranslated region-luciferase reporter system, we validated that ICOSL is an authentic miR-24 target. Transfection of anti-miR-24 molecules in EBNA2-expressing lymphoma cells reconstituted ICOSL expression and increased tumor immunogenicity in mixed lymphocyte reactions. Because miR-24 is known to target c-MYC, an oncoprotein positively regulated by EBNA2, we analyzed its expression in anti-miR-24 transfected lymphoma cells. Indeed, the reduction of miR-24 in EBNA2-expressing DLBCL further elevated c-MYC and increased apoptosis. Consistent with the in vitro data, EBNA2-positive DLBCL biopsies expressed low ICOSL and high miR-24. We suggest that EBV evades host immune responses through EBNA2 by inducing miR-24 to reduce ICOSL expression, and for simultaneous rheostatic maintenance of proproliferative c-MYC levels. Overall, these data identify miR-24 as a potential therapeutically relevant target in EBV-associated lymphomas.

Abstract Liver disease is a major global health concern, claiming approximately 2 million lives worldwide annually, yet curative treatments remain elusive. In our study, we aimed to investigate the role of microRNA-21-5p (miR-21) in metabolic dysfunction-associated steatotic liver disease (previously NAFLD), metabolic-associated steatohepatitis (previously NASH), and hepatocellular carcinoma (HCC) within the context of a Western high-fat diet (HFD) and offering potential therapeutic insights. We found that reduced miR-21 levels correlated with liver disease progression in WT mice fed on HFD, while miR-21 knockout mice showed exacerbated metabolic dysfunction, including obesity, hepatomegaly, hyperglycemia, insulin resistance, steatosis, fibrosis, and HCC. Our study reveals that miR-21 plays a protective role in metabolic syndrome and in the progression of liver disease to cancer. miR-21 directly targets Transforming growth factor beta-induced (Tgfbi), a gene also known to be significantly upregulated and a potential oncogene in HCC. Further, our study showed that intervention with the administration of a miR-21 mimic in WT livers in HFD conditions effectively improves insulin sensitivity, steatosis, fibrosis, tumor burden, as well as Tgfbi expression. These findings indicate that miR-21 could serve as an effective strategy to delay or prevent liver disease in high-fat-diet environments. Citation Format: Urmila Jagtap, Anan Quan, Yuho Ono, Jonathan Lee, Kylie A. Shen, Sergei Manakov, Gyongyi Szabo, Imad Nasser, Frank J. Slack. miR-21: A therapeutic target that delays severe liver disease and hepatocellular carcinoma under high-fat-diet conditions [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 5689.

Nucleic acids are a class of drugs that can modulate gene and protein expression by various mechanisms, namely, RNAi, mRNA degradation by RNase H cleavage, splice modulation, and steric blocking of protein binding or mRNA translation, thus exhibiting immense potential to treat various genetic and rare diseases. Unlike protein-targeted therapeutics, the clinical use of nucleic acids relies on Watson-Crick sequence recognition to regulate aberrant gene expression and impede protein translation. Though promising, targeted delivery remains a bottleneck for the clinical adoption of nucleic acid-based therapeutics. To overcome the delivery challenges associated with nucleic acids, various chemical modifications and bioconjugation-based delivery strategies have been explored. Currently, liver targeting by N-acetyl galactosamine (GalNAc) conjugation has been at the forefront for the treatment of rare and various metabolic diseases, which has led to FDA approval of four nucleic acid drugs. In addition, various other bioconjugation strategies have been explored to facilitate active organ and cell-enriched targeting. This review briefly covers the different classes of nucleic acids, their mechanisms of action, and their challenges. We also elaborate on recent advances in bioconjugation strategies in developing a diverse set of ligands for targeted delivery of nucleic acid drugs.

Severe COVID-19 leads to widespread transcriptomic changes in the human brain, mimicking diminished cognitive performance. As long noncoding RNAs (lncRNAs) play crucial roles in the regulation of gene expression, identification of the lncRNAs differentially expressed upon COVID-19 may nominate key regulatory nodes underpinning cognitive changes. Here we identify hundreds of lncRNAs differentially expressed in the brains of COVID-19 patients relative to uninfected age/sex-matched controls, many of which are associated with decreased cognitive performance and inflammatory cytokine response. Our analyses reveal pervasive transcriptomic changes in lncRNA expression upon severe COVID-19, which may serve as key regulators of neurocognitive changes in the brain.

Interactions between tumor and stromal cells are well known to play prominent roles in progression of pancreatic ductal adenocarcinoma (PDAC). As knowledge of stromal crosstalk in PDAC has evolved, it has become clear that cancer associated fibroblasts can play both tumor promoting and tumor suppressive roles through a combination of paracrine crosstalk and juxtacrine interactions involving direct physical contact. Another major contributor to dismal survival statistics for PDAC is development of resistance to chemotherapy drugs, though less is known about how the acquisition of chemoresistance impacts upon tumor-stromal crosstalk. Here, we use time lapse imaging and image analysis to study how co-culture geometry impacts interactions between epithelial and stromal cells. We show that extracellular matrix (ECM) overlay cultures in which stromal cells (pancreatic stellate cells, or normal human fibroblasts) are placed adjacent to PDAC cells (PANC1) result in direct heterotypic cell adhesions accompanied by dramatic fibroblast contractility. We analyze these interactions in co-cultures using particle image velocimetry (PIV) analysis to quantify cell velocities over the course of time lapse movie sequences. We further contrast co-cultures of PANC1 with those containing a drug resistant subline (PANC1-OR) previously established in our lab and find that heterotypic cell-cell interactions are suppressed in the latter relative to the parental line. We use RNA-seq and bioinformatics analysis to identify differential gene expression in PANC1 and PANC1-OR, which shows that negative regulation of cell adhesion molecules, consistent with increased epithelial mesenchymal transition (EMT), is also correlated with reduction in the hetrotypic cell-cell contact necessary for the contractile behavior observed in drug naïve cultures. Overall these findings elucidate the role of drug-resistance in inhibiting an avenue of stromal crosstalk which is associated with tumor suppression and also help to establish cell culture conditions useful for further mechanistic investigation.

We explore the potential of clamp-G nucleobase-modified peptide nucleic acids (cGPNAs) as microRNA and messenger RNA inhibitors. For proof of concept, we target miR-155, which is upregulated in diffuse large B cell lymphoma. cGPNA shows significant downregulation of miR-155 and the upregulation of its downstream targets in multiple lymphoma cell lines. Also, cGPNA treatment in vivo reduced tumor growth and improved survival in the U2932 cell- derived xenograft mouse model. To assess the broad application of cGPNA as an antisense modality, we also target transthyretin (TTR) mRNA. We establish a dose-dependent effect of antisense cGPNA on TTR mRNA levels. For in vivo studies, we conjugated cGPNA-based TTR antisense with lactobionic acid-based targeting ligand for in vivo liver delivery. We establish that cGPNA exhibits significant TTR protein knockdown compared to unmodified peptide nucleic acid (PNA) in vivo. Overall, we confirm that clamp-G-modified PNA analogs are a robust antisense therapy platform.

MicroRNAs (miRNAs) have been implicated in human disorders, from cancers to infectious diseases. Targeting miRNAs or their target genes with small molecules offers opportunities to modulate dysregulated cellular processes linked to diseases. Yet, predicting small molecules associated with miRNAs remains challenging due to the small size of small molecule-miRNA datasets. Herein, we develop a generalized deep learning framework, sChemNET, for predicting small molecules affecting miRNA bioactivity based on chemical structure and sequence information. sChemNET overcomes the limitation of sparse chemical information by an objective function that allows the neural network to learn chemical space from a large body of chemical structures yet unknown to affect miRNAs. We experimentally validated small molecules predicted to act on miR-451 or its targets and tested their role in erythrocyte maturation during zebrafish embryogenesis. We also tested small molecules targeting the miR-181 network and other miRNAs using in-vitro and in-vivo experiments. We demonstrate that our machine-learning framework can predict bioactive small molecules targeting miRNAs or their targets in humans and other mammalian organisms. Here the authors developed and experimentally validated sChemNET, a deep learning framework to predict small molecules affecting microRNA function based on chemical structure and sequence data. sChemNET predicts bioactive small molecules on the basis of sparse chemical datasets.

Liver disease, including hepatocellular carcinoma (HCC), is a major global health concern, claiming approximately 2 million lives worldwide annually, yet curative treatments remain elusive. In this study, we aimed to investigate the role of microRNA-21-5p (miR-21) in metabolic dysfunction-associated steatotic liver disease (previously NAFLD), metabolic-associated steatohepatitis (previously NASH), and HCC within the context of a Western high-fat diet, without additional choline (HFD) and offering potential therapeutic insights. We found that reduced miR-21 levels correlated with liver disease progression in WT mice fed on HFD, while miR-21 knockout mice showed exacerbated metabolic dysfunction, including obesity, hepatomegaly, hyperglycemia, insulin resistance, steatosis, fibrosis, and HCC. Our study reveals that miR-21 plays a protective role in metabolic syndrome and in the progression of liver disease to cancer. MiR-21 directly targets Transforming growth factor beta-induced (Tgfbi), a gene also known to be significantly upregulated and a potential oncogene in HCC. Further, our study showed that intervention with the administration of a miR-21 mimic in WT livers effectively improves insulin sensitivity, steatosis, fibrosis, Tgfbi expression and tumor burden in HFD conditions. These findings indicate that miR-21 could serve as an effective strategy to delay or prevent liver disease in high-fat-diet environments.

MicroRNAs (miRNAs) are small RNAs that are often dysregulated in many diseases, including cancers. They are highly tissue-specific and stable, thus, making them particularly useful as biomarkers. As the spatial transcriptomics field advances, protocols that enable highly sensitive and spatially resolved detection become necessary to maximize the information gained from samples. This is especially true of miRNAs where the location their expression within tissue can provide prognostic value with regard to patient outcome. Equally as important as detection are ways to assess and visualize the miRNA's spatial information in order to leverage the power of spatial transcriptomics over that of traditional nonspatial bulk assays. We present a highly sensitive methodology that simultaneously quantitates and spatially detects seven miRNAs in situ on formalin-fixed paraffin-embedded tissue sections. This method utilizes rolling circle amplification (RCA) in conjunction with a dual scanning approach in nanoliter well arrays with embedded hydrogel posts. The hydrogel posts are functionalized with DNA probes that enable the detection of miRNAs across a large dynamic range (4 orders of magnitude) and a limit of detection of 0.17 zeptomoles (1.7 x 10(-4) attomoles). We applied our methodology coupled with a data analysis pipeline to K14-Cre Brca1(f/f)Tp53(f/f) murine breast tumors to showcase the information gained from this approach.

Abstract Melanomas are responsible for about 80% of all deaths related to skin cancers. This is due to its high potential of metastasizing and developing resistance to treatments. Novel therapeutic modalities and the identification of biomarkers able to predict the prognosis are necessary. Studies have revealed the central role of long non-coding RNAs (lncRNAs) in regulatory networks controlling cell behavior. The disruption of these regulatory networks as a consequence of altered expression of lncRNAs can contribute to cancer development and progression. Our laboratory has developed a linear cellular model of melanoma progression consisting of distinct cell lines: melan-a (melanocytes), 4C (pre-malignant melanocytes), 4C11- (undifferentiated, slow-growing and non-metastatic melanoma cells) and 4C11+ (differentiated, highly proliferative and metastatic melanoma cells), which were analyzed for their lncRNA expression profile. Differentially expressed lncRNAs identified by RNAseq were selected by in silico analyses based on their proximity to differentially expressed coding-genes in the same melanoma model. Correlation analyses were performed between the expression of differentially expressed lncRNA neighboring genes and their melanoma patient survival, using two independent melanoma cohorts (TCGA and Leeds). Among those lncRNA located near genes presenting prognostic value is the lncRNA Gm20619, here named Slamon, neighbor to Slc25a13 gene (mitochondrial aspartate/glutamate carrier gene), which high expression correlates with poor prognosis. Both Slamon lncRNA and Slc25a13 are highly expressed in the metastatic melanoma cells 4C11+ compared to melan-a, 4C and 4C11- cell lines. The knocking down of Slamon or Slc25a13 were performed in 4C11+ melanoma cells, followed by analyses of collective migration, clonogenicity, proliferation, anoikis resistance, and dacarbazine and MEK inhibitor treatment. By knocking down Slamon lead 4C11+ cells significantly less migratory and less resistant to dacarbazine, and resulted in increased expression of Slc25a13 gene. 4C11+ melanoma cells knocked down for Slc25a13 also presented reduced migratory, clonogenicity, proliferation and anoikis resistance capability, diminished sensitivity to dacarbazine and MEK inhibitor treatment, and increased expression of Slamon lncRNA. The analysis of genes coexpressed with Slc25a13 revealed genes related to tumor progression, as Cdk15, Lsp1 and Pdgfrb. Our results suggest a crucial role of the lncRNA Slamon and Slc25a13 coding gene in melanoma progression which has never been described before. Slamon regulates tumor aggressiveness associated with Slc25a13, forming a regulatory network. These findings reveal the importance of lncRNAs in melanoma biology, potentially indicating transcripts that can serve as prognostic biomarkers and therapeutic targets in melanoma. Citation Format: Beatriz C. Tonin, Ana L. Ayub, André H. Lengert, Sang W. Han, Eduardo M. Reis, Frank J. Slack, Miriam G. Jasiulionis. The role of the lncRNA Slamon and Slc25a13 neighbor gene in melanoma aggressiveness [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 5684.