Aggressive Phenotype Research Articles

Abstract B017: The double-edged sword of cystatin B in luminal-like and triple-negative breast cancers

Abstract The complex protease network of cathepsins and their inhibitors, cystatins, intricately regulates numerous cellular processes, and its dysregulation is frequently implicated in cancer pathogenesis. Abnormal cathepsin activity, subcellular localization, and a disrupted balance between cathepsins and cystatins have been identified in cancer. While diminished cystatin levels typically correlate with more aggressive cancer phenotypes, few findings challenge this paradigm. In this context, our latest study revealed elevated expression of cystatin B (CSTB) in luminal-like breast cancer (BC) patients experiencing relapse within five years post-surgery. Furthermore, computational analysis of publicly available datasets supports our idea of CSTB as a potential negative prognostic biomarker in luminal-like tumors. Intriguingly, a converse relationship is observed in basal-like/triple negative BC patients, where increased CSTB expression seems to be associated with improved prognosis. In addition, the cysteine/cathepsin network intricately intersects with immune functions, adding another layer of complexity. Cathepsins are indeed involved in the induction of an efficient anti-tumor immune response, being key in antigen processing and presentation by antigen-presenting cells and in the cytotoxic activities of NK and T cells. On the other hand, myeloid cells rely on cathepsins for the degradation of ECM proteins that may favor migration and invasion of tumor cells. All these pieces of evidence led to the hypothesis that the functional impact of CSTB may vary depending on the tumor intrinsic characteristics and on its microenvironment and therefore that CSTB might fulfill distinct functional roles in luminal-like and basal-like BC. To start addressing our hypothesis, we silenced CSTB expression in the 4T1 mouse cell line, a TNBC model spontaneously metastasizing to the lungs upon intra-mammary fat pad injection. Preliminary in vivo experiments to investigate the effect on primary tumor growth and metastatic dissemination showed that 4T1 shCSTB lines were indeed characterized by increased tumor growth and metastatic dissemination than the two sh-control lines. Interestingly, expression of stemness- related genes (Nanog, Sox2 and Oct4) were up-modulated upon CTSB silencing, in agreement with a more aggressive phenotype. On the other hand, preliminary in vitro assays with a luminal- like BC cell line support the hypothesis of an opposite effect of CSTB down-modulation in luminal BC subtype. Moreover, CSTB silencing in RAW264.7 macrophagic cell line, impaired M1 in vitro polarization, while it did not appear to affect M2 skewing. Overall, although preliminary, these data suggest that CSTB may affect BC aggressiveness by both interfering with tumor cell-intrinsic features and microenviroment-related traits. Citation Format: Anna Zaccaria, Chiara Ratti, Laura Botti, Sabina Sangaletti, Mario P. Colombo, Claudia Chiodoni. The double-edged sword of cystatin B in luminal-like and triple-negative breast cancers [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 B017.

Abstract B022: Investigating how monocytes impair NK cell cytotoxicity in lung metastasis of triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) accounts for 20% of breast cancer (BC) cases worldwide, yet due to its aggressive phenotype and lack of targeted therapies it has the worst prognosis amongst BC subtypes. Up to 40% of TNBC patients will relapse after treatment and develop distant metastasis. Metastasis is the complex process by which disseminated tumor cells (DTCs) leave the primary tumor and grow at distal sites. Since most metastases occur within 3 years of diagnosis, the rapid onset and lack of effective treatments in metastatic TNBC (mTNBC) means less than 20% of patients survive after 4 years. Even though it is the most “immune-activated” BC subtype, and immune checkpoint blockade (ICB) has shown clinical benefits in early TNBC, there is a clear need for novel immunotherapeutic approaches for patients with mTNBC. Natural killer (NK) cells are innate lymphocytes that function as the body’s first line defense against metastatic cancer cells. NK cells eliminate DTCs in the blood or at distal sites via NK cell cytotoxicity (NKCC) and this process is known to be impaired in successful metastasis. We hypothesized that other cells within the tumor microenvironment (TME) can inhibit NKCC at the earliest stages of metastatic outgrowth. We have used Cherry-niche, an in vivo labelling tool, to characterize how TME cells change in early and established lung micro-metastases by single-cell RNA sequencing (scRNA-seq) and flow cytometry. Our initial analyses showed that monocytes are highly enriched, not only in the entire metastatic lung, but specifically in the established niche surrounding DTCs. Although we detected a slight increase in total NK cells, there was a shift in maturation status with fewer mature NK cells (CD27-CD11b+) and more immature NK cells (CD27+/-CD11b-) in the metastatic lung. Furthermore, NK cells were largely absent from the metastatic niche and those that were present displayed a dysfunctional phenotype. CellChat and NicheNet analyses of our scRNA-seq data predicted that several receptor-ligand interactions, including the cytokine macrophage migration inhibitory factor (MIF), can mediate the crosstalk between NK cells and monocytes. Next, we developed an in vitro 3D co-culture system to study the effect of blood-derived monocytes on human NKCC against mTNBC cells. We found that monocytes can suppress NKCC against MDA-MB-231 cells and decrease the viability of mature NK cells. Furthermore, recombinant MIF was able to directly inhibit NKCC, whilst a selective MIF antagonist was able to rescue monocyte-induced impairment of NKCC. These data implicate MIF as a critical monocyte-derived factor in the suppression of NK cell function against mTNBC cells. Future work will aim to identify the exact mechanism by which MIF inhibits NKCC, whilst also evaluate the effect of monocyte depletion and MIF inhibition on metastatic outgrowth and NK cell activation/maturation in vivo. This study will reveal novel inter-cellular dynamics occurring in the metastatic lung, as well as immunotherapeutic targets that may restore NKCC in mTNBC. Citation Format: Christos Ermogenous, Luigi Ombrato, Gordon Beattie. Investigating how monocytes impair NK cell cytotoxicity in lung metastasis of triple-negative breast cancer [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 B022.

Lower FGFR2 mRNA Expression and Higher Levels of FGFR2 IIIc in HER2-Positive Breast Cancer

Fibroblast growth factor receptor 2 (FGFR2) has been associated with breast cancer. We performed in silico analyses to investigate the FGFR2 mRNA expression and splice variants associated with breast cancer subtypes. Online databases, including cBioPortal and TCGA SpliceSeq, were used to examine the association between the FGFR2 expression and splice variants with breast cancer subtypes. A higher FGFR2 mRNA was significantly associated with luminal, oestrogen receptor (ER)-positive breast cancers, and invasive lobular carcinomas, whereas a lower FGFR2 was associated with human epidermal growth factor receptor 2 (HER2)-positive breast cancer and invasive ductal carcinomas. The epithelial alternatively spliced FGFR2 IIIb isoform was significantly enriched in ER+ breast cancer, while the mesenchymal FGFR2 IIIc isoform was significantly prevalent in HER2+ cancer. Increased levels of FGFR2 and IIIb splice isoforms are associated with less aggressive breast cancer phenotypes, while decreased levels of FGFR2 and increased IIIc splice isoform are associated with more aggressive phenotypes.

Abstract A053: Liquid biopsy-based detection of triple negative breast cancer using DNA methylation biomarkers

Abstract Triple-negative breast cancer (TNBC) presents significant clinical challenges due to its aggressive phenotype, rapid progression, and limited targeted treatment options. TNBC often mimics benign lesions on ultrasound and metastatic features can be missed in routine mammography screening leading to misdiagnosis and delayed treatment. These limitations led us to investigate whether a blood-based liquid biopsy could provide a non-invasive, sensitive method for early TNBC detection, potentially overcoming the constraints of conventional imaging techniques. To discover biomarkers for TNBC, we performed targeted bisulfite sequencing on a cohort of 46 breast cancer solid tissue biopsy samples, comprising 19 TNBC and 27 non-TNBC cases. We identified 150 differentially methylated regions (mean length 703bp) separating TNBC and non-TNBC samples. Upon linking each region to its nearest gene, we observed several genes previously associated with prognosis and survival (HOXB3, PAX9, SOX9) substantiating the clinical relevance of these biomarkers. Using public TCGA data (369 breast cancer samples), we integrated expression and methylation data and observed directionally consistent changes. For example, HOXB3 showed increased methylation at its associated differential regions and decreased expression in TNBC cases. To ascertain whether these biomarkers could be useful in a liquid biopsy approach, we performed targeted bisulfite- sequencing on cell-free DNA samples derived from prospectively collected patients with breast cancer. All samples had independent tissue-based assessment of ER, PR and HER2 using immunohistochemistry or in situ hybridization. We then built a feed-forward neural network classifier with classes TNBC and non-TNBC that used transfer-learning and the identified biomarkers to learn methylation signatures in the biopsy samples and map them to cell-free DNA. To emulate clinical workflow, where subtyping follows cancer diagnosis and tissue of origin identification, we evaluated cfDNA samples correctly identified as breast cancer using two independent machine learning models trained using 2,393 prospectively collected multi- indication cancer and non-cancer samples (NCT05435066). Subsequent TNBC subtyping of breast cancer-positive cases (N=56) accurately identified 77% (10/13) of TNBC samples and 91% (39/43) of non-TNBC cases, with overall accuracy of 84%. The estimated tumor content range for correctly predicted TNBC samples was 0.5-33% with the three mis-classified samples all showing very low tumor content (0.22%, 0.28%, 0.59%). Non-TNBC cases showed a tumor content range of 0.07-36% for correct and 2.3-14% for misclassified samples. In conclusion, we identified novel methylation biomarkers that distinguish TNBC in the cell-free DNA of patients without needing invasive tissue biopsies. The high sensitivity of our assay at low tumor fractions has the potential to improve outcomes through earlier intervention and may enable earlier screening in high-risk groups, monitoring of minimal residual disease and longitudinal monitoring during treatment. Citation Format: Jocelyn Charlton, Shiva Farashahi, Kade Pettie, Elie Massaad, Josh Hubbell, Feras Hantash, Kieran I Chacko. Liquid biopsy-based detection of triple negative breast cancer using DNA methylation biomarkers [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A053.

A Review of Limbic System-Associated Membrane Protein in Tumorigenesis

Purpose of Review: This review aims to describe the role of limbic system-associated membrane protein (LSAMP) in normal- and pathophysiology, and its potential implications in oncogenesis. We have summarized research articles reporting the role of LSAMP in the development of a variety of malignancies, such as clear cell renal cell carcinoma, prostatic adenocarcinoma, lung adenocarcinoma, osteosarcoma, neuroblastoma, acute myeloid leukemia, and epithelial ovarian cancer. We also examine the current understanding of how defects in LSAMP gene function may contribute to oncogenesis. Finally, this review discusses the implications of future LSAMP research and clinical applications. Recent Findings: LSAMP has been originally described as a surface adhesion glycoprotein expressed on cortical and subcortical neuronal somas and dendrites during the development of the limbic system. It is categorized as part of the IgLON immunoglobulin superfamily of cell-adhesion molecules and is involved in regulating neurite outgrowth and neural synapse generation. LSAMP is both aberrantly expressed and implicated in the development of neuropsychiatric disorders due to its role in the formation of specific neuronal connections within the brain. Additionally, LSAMP has been shown to support brain plasticity via the formation of neuronal synapses and is involved in modulating the hypothalamus in anxiogenic environments. In murine studies, the loss of LSAMP expression was associated with decreased sensitivity to amphetamine, increased sensitivity to benzodiazepines, increased hyperactivity in new environments, abnormal social behavior, decreased aggressive behavior, and decreased anxiety. Findings have suggested that LSAMP plays a role in attuning serotonergic activity as well as GABA activity. Given its importance to limbic system development, LSAMP has also been studied in the context of suicide. In malignancies, LSAMP may play a significant role as a putative tumor suppressor, the loss of which leads to more aggressive phenotypes and mortality from metastatic disease. Loss of the LSAMP gene facilitates epithelial-mesenchymal transition, or EMT, where epithelial cells lose adhesion and gain the motile properties associated with mesenchymal cells. Additionally, LSAMP and the function of the RTK pathway have been implicated in tumorigenesis through the modulation of RTK expression in cell membranes and the activation of second messenger pathways and β-catenin. Summary: Beyond its many roles in the limbic system, LSAMP functions as a putative tumor suppressor protein. Loss of the LSAMP gene is thought to facilitate epithelial-mesenchymal transition, or EMT, where cells lose adhesion and migrate to distant organs. LSAMP’s role in modulating RTK activity and downstream ERK and Akt pathways adds to a large body of data investigating RTK expression in oncogenesis. The characteristics of LSAMP defects and their association with aggressive and metastatic disease are evident in reports on clear cell renal cell carcinoma, prostatic adenocarcinoma, lung adenocarcinoma, osteosarcoma, neuroblastoma, acute myeloid leukemia, and epithelial ovarian cancer.

Abstract A026: A novel ddPCR detects hypermethylated RASSF1A in plasma of patients with pediatric Wilms tumor

Abstract Background: Wilms tumor is the most common pediatric renal cancer. Within the SIOP-Renal Tumor Study Group (SIOP-RTSG), diagnosis is based on imaging and patients receive neo- adjuvant treatment. Final diagnosis is established via histopathological analysis at the timepoint of surgery, which also determines the intensity of adjuvant treatment. Overall, patients with Wilms tumor have a 90% survival rate, but one in five patients will suffer from a relapse, which requires intensive treatment and induces long-term toxicity. It is challenging to identify patients at risk of suffering from relapse at initial diagnosis. Hence the need for additional biomarkers that will optimize risk stratification and minimal residual disease monitoring. RASSF1A is a tumor suppressor gene that is silenced via hypermethylation of its promotor region in multiple adult and pediatric tumors and is reported to represent an aggressive phenotype. We have previously reported on thirteen patients with Wilms tumor where increased hypermethylation of RASSF1A (RASSF1A-M) was observed in plasma cell-free DNA (cfDNA). The aim of this study was to further investigate the levels of RASSF1A-M in a larger cohort. Methods: The presence of RASSF1A-M in plasma cfDNA of patients with Wilms tumor was quantified using a multiplexed droplet digital PCR comprising methylation-specific restriction enzymes. Diagnosis and pre- surgery samples were included to evaluate RASSF1A-M levels during treatment. Results: A total of 49 patients were evaluated. At diagnosis, 37/46 (80.4%) samples were positive for RASSF1A-M. Negative samples were from patients with localized disease (N=6), regressive type regionally advanced Wilms (N=1) or mixed type metastatic Wilms (N=2). RASSF1A-M levels were significantly elevated in regionally advanced and metastatic disease compared to localized disease. Of the 37 positive diagnosis samples, 23 pre-surgical follow-up samples were available. In 7/23, RASSF1A-M was still detectable. These belong to patients with stromal-, regressive- or diffuse anaplastic predominant tumors. Interestingly, an increasing methylation level was seen in one patient with a regressive tumor. Conclusion: RASSF1A-M is a potential biomarker for patients with Wilms tumor, since it was detected in the majority of patients. Furthermore, significantly increased levels were observed in regionally advanced and metastatic disease. In the small number of patients with persisting levels of RASSF1A-M, we did not observe an association with risk groups. In collaboration with SIOP-RTSG, additional follow-up samples will be analyzed to explore the potential of RASSF1A-M as biomarker for relapse detection. Citation Format: Julia Sprokkerieft, Nathalie S.M. Lak, Zeinab van Gestel-Fadaie, Marry M. van den Heuvel-Eibrink, Godelieve A.M. Tytgat. A novel ddPCR detects hypermethylated RASSF1A in plasma of patients with pediatric Wilms tumor [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A026.

Pancreatic cancer-derived exosomal miR-510 promotes macrophage M2 polarization and facilitates cancer cell aggressive phenotypes.

Extensive tumor microenvironment (TME) and tumor-associated macrophages (TAMs) contribute to the initiation and progression of pancreatic cancer (PC). Cancer cell-derived exosomal miRNAs that stimulate macrophage M2 polarization might play an important role in the process. In the current study, we observed significant upregulation of miR-510 in PC cell lines in comparison to normal HPDE cell line, with PANC-1 exhibiting the highest and MIA PaCa-2 the lowest miR-510 levels. Functional assays demonstrated that miR-510 overexpression enhanced, while its inhibition reduced, PC cell viability, migration, invasion, and EMT. In vivo, miR-510 mimics promoted tumor growth and macrophage M2 polarization, whereas miR-510 inhibition had the opposite effect. Exosomes from PANC-1 and MIA PaCa-2 cells, characterized by nanoparticle tracking analysis and TEM, contained significantly higher miR-510 levels than those from HPDE cells. Macrophages incubated with conditioned media from these PC cells showed increased M2 polarization markers, a process inhibited by the exosome inhibitor GW4869. The delivery of miR-510 via PC cell-derived exosomes facilitated macrophage M2 polarization and regulated the STAT signaling pathway, suggesting that exosomal miR-510 plays a crucial role in the tumor microenvironment of PC by modulating macrophage M2 polarization.

The Expression of HPV-16 E5 Oncoprotein Impacts the Transcript Profiles of FGFR2 and EMT-Related Genes in Preneoplastic Anal Epithelium Lesions

Anal Squamous Cell Carcinoma (SCCA) is a rare Human Papillomavirus type 16 (HPV16)-associated carcinoma whose pathogenesis is still poorly understood. Recent studies based on biopsy and Next Generation Sequencing (NGS) approaches have linked the viral episomal status to aggressive SCCA phenotypes, suggesting a potential role of the 16E5 oncoprotein in tumor development. Our previous findings indicated that 16E5 induces Fibroblast Growth Factor Receptor 2 (FGFR2) isoform switching, aberrant mesenchymal FGFR2c expression, Epithelial Mesenchymal Transition (EMT), and cell invasion in various in vitro human keratinocyte models, as well as in the in vivo context of cervical Low-grade Squamous Intraepithelial Lesions (LSILs). To further explore the role of 16E5 in epithelial carcinogenesis, this study aims to investigate the molecular profile in HPV-related anal lesions. The results showed a significant positive correlation between 16E5 and FGFR2c, as well as 16E5 or FGFR2c and key EMT-related transcription factors, particularly in the group of HPV16 positive anal samples not containing without high grade lesions. Additionally, by coupling the molecular analysis with an interactome investigation, we hypothesized a potential functional interplay between the Ca2+ channel Transient Receptor Potential Ankyrin 1 (TRPA1) and FGFR2c, mediated by 16E5 during the establishment of the oncogenic signaling. These findings will help to elucidate the actual relevance of 16E5 in the early progression of anal lesions and contribute to determine its potential as target for future preventive approaches for HPV16-positive SCCA.

STEM-12. A NEURONAL STEM-LIKE PHENOTYPE IN GRADE 4 IDH-MUTANT ASTROCYTOMA WITH CDKN2A/B LOSS IS ASSOCIATED WITH CUX2 DEFICIENCY

Abstract Diffuse gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, the loss of CDKN2A/B in IDH-mutant astrocytoma confers an aggressive high grade phenotype and is the strongest implicated molecular alteration associated poor clinical survival, thus is now sufficient to define a grade 4 tumor regardless of histologic grade. However, there remains no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with RNA sequencing data and found the increased expression of regulators of embryonic nervous system development and signaling concurrent with CDKN2A/B loss. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and cell-lines harboring CDKN2A/B homozygous deletion, we stably re-expressed p14ARF, p15INK4B, and p16INK4A using a Tet-inducible system. IDH-mutant cell lines with re-expression of p14, p15, or p16 displayed differential transcription factor activation, impaired neurosphere capability, decreased colony formation, and lower neurosphere proliferation. Intriguingly, RNA-seq data revealed CUX2, a transcription factor known to control neuronal precursor behavior, as the likely candidate regulating the differential expression profile across CDKN2A/B status. We observed increased CUX2 expression in cell lines stably re-expressing p14, p15, and p16. We validated the CUX2 signature across publicly available datasets of IDH-mutant astrocytoma where CUX2 expression negatively correlated with loss of CDKN2A/B in patient tumors. Together our work suggests CUX2 deficiency in IDH-mutant astrocytoma with CDKN2A/B deletion enables an increased neuronal stem-like phenotype in these grade 4 tumors.

EXTH-27. POLYCOMB OVERACTIVITY DRIVES TUMORIGENESIS IN AGGRESSIVE CUSHING’S DISEASE

Abstract INTRODUCTION Aggressive Cushing’s disease (CD) tumors (Ki67 > 3%) exhibit rapid growth, poor postsurgical outcomes, and resistance to conventional therapies. Polycomb group (PcG) proteins are canonical epigenetic silencers that can drive tumor aggressiveness. We asked if PcG underlies rare but fatal pituitary tumor progression. METHODS We performed paired multiome analysis (single nucleus RNAseq and ATACseq) in 5 aggressive CD adenomas, and adjacent normal gland. We verified protein expression with multiplexed immunohistochemistry (mIHC) and PcG activity by H3K27me3 ChIPseq. Aggressive murine pituitary tumor cells ATT20 were treated using PcG inhibitors (DZNep, tazemetostat), HDAC inhibitor (vorinostat), or siRNA (Ezh2, Suz12). PcG binding to the POMC promoter was assessed by reverse chromatin immunoprecipitation (rChIP). We treated one patient off-label with oral vorinostat 400mg daily for 6 days prior to radiation. RESULTS PcG loci (EZH2 and EED) were more accessible in aggressive CD adenoma versus normal gland corticotrophs, and EZH2, SUZ12 and EED mRNA was robustly overexpressed. mIHC confirmed SUZ12, EZH2 and H3K27me3 overexpression, and ChIPseq confirmed polycomb overactivity in aggressive CD adenomas. Polycomb inhibition by DZNep, vorinostat, or siRNAs led to proliferative arrest and Pomc suppression in ATT20 cells (P < 0.05 versus controls). Vorinostat enriched Suz12 at the Pomc promoter (P < 0.01), confirming direct silencing. In a patient with aggressive CD and hypercortisolemia despite two prior surgeries, a single course of vorinostat decreased cortisol (24mcg/dL to 7.5mcg/dL) and ACTH (63.7pg/mL to 44.9pg/mL) prior to radiation therapy initiation. CONCLUSIONS PcG hyperactivity is associated with a more aggressive CD phenotype. We report here the therapeutic potential of HDAC inhibition against aggressive CD adenomas in a first-in-human application.

BIOM-32. GENOMIC DETERMINANTS OF DIFFUSELY INFILTRATIVE GLIOMATOSIS CEREBRI PATTERN

Abstract Gliomatosis cerebri (GC), though no longer a distinct pathological entity in WHO 2021, is a unique and aggressive phenotype of diffuse gliomas with extensive and widespread infiltration. GC can present as primary de novo or secondary after treatment. We aimed to study the genomic determinants of GC. We identified 72 GC cases from 2013-2023 at MD Anderson Cancer Center. Cases were confirmed by detailed radiographic review. This included 57 glioblastoma (79%), 13 IDH mutant astrocytoma (18%), 1 IDH mutant oligodendroglioma (1.4%), and 1 high-grade astrocytoma with piloid features (1.4%). 53/72 (73.6%) were primary and 19/72 (26.4%) were secondary GC. We used 40 patients without the GC pattern as controls. Among glioblastoma GC cases and in comparison with controls, mutations in PTEN and EGFR were significantly associated with the GC pattern: 18/57 (32%) vs 3/38 (7.9%), p-value=0.01 and 23/57 (40%) vs 6/38 (16%), p-value=0.013, respectively. This held true in primary but not secondary GC. Out of 20 most commonly mutated genes in GC, mutations in EGFR, TERT, and MDM4 were associated with worse PFS: p-value=0.004, p-value=0.007, p-value=0.013, respectively and mutations in TERT and MDM4, but not EGFR, were associated with worse OS: p-value=0.003, p-value=0.015, respectively. Secondary GC was associated with IDH mutation compared to control non-GC cases: 8/19 (42%) vs 2/40 (5%), p-value=0.001. As expected, IDH mutation was associated with improved PFS, p-value<0.001 and OS, p-value=0.003 in GC. No genes were significantly associated with laterality of GC. We found novel associations between PTEN and EGFR mutations and the GC phenotype and IDH mutation with the occurrence of secondary GC after treatment. While MDM4 is not associated with outcomes in gliomas, we show that MDM4 mutation is associated with poor survival in GC. These findings shed light into molecular basis of GC and need to be further validated in larger studies.

TMIC-67. EMERGING ROLE OF EXTRACELLULAR MATRIX STIFFNESS AS A HALLMARK OF GLIOBLASTOMA: INSIGHT TO MECHANICAL MEMORY FORMATION AND PROLONGED INVASION IN THE TUMOR PERIPHERY

Abstract The extracellular matrix (ECM) plays a critical role in cancer progression, with its biophysical properties influencing cancer behavior. ECM stiffness can induce long-lasting adaptations in cancer cells, promoting sustained invasion through a process known as “mechanical memory” (MM). Glioblastoma (GBM) exhibits spatial heterogeneity in stiffness, with stiffer ECM found at the tumor periphery where invasive cells reside and promote recurrence. We hypothesize that increased stiffness at the tumor periphery primes GBM cells for sustained invasion through MM. METHODS Cell lines were established from image-guided human GBM samples from tumor margin and core (n=10 patients, 20 cell lines). Cells from random locations were conditioned in physiologically relevant extracellular matrices for two weeks. Human organotypic assay (n=3), Migration Assays, Atomic Force Microscopy (AFM), Immunocytochemistry, Western Blot, and RNA-sequencing (n=6) were performed. RESULTS GBM cells at higher stiff surfaces displayed increased migration (p<0.01). Magnetic Resonance Elastography (n=9) confirmed GBM heterogeneity, with softer cores (0.2-0.5kPa) transitioning to stiffer margins (>2kPa). Organotypic scaffolds mimicking the tumor margin promoted enhanced migration of GFP-labeled GBM cells. Margin cells and cells conditioned on stiffer matrices demonstrated higher migratory potential compared to their core and soft-conditioned counterparts (p<0.05). These trends persist over time and across multiple passages. ECM stiffness exposure causes nanomechanical, cytoskeletal, and transcriptional adaptations. AFM shows that cells from the margin (n=6) are softer (p<0.01) and more deformable (p<0.01). RNAseq identified upregulation of MM-specific genes in GBM margin cells. The mechanosensitive transcription factor YAP1 emerged as a key driver of MM. Notably, YAP1 is targetable by the FDA-approved drug Verteporfin. YAP1 expression was elevated in margin and stiff-conditioned cells (p<0.05). Stiff-conditioned cells and margin cells displayed increased sensitivity to Verteporfin treatment (p<0.05), with treatment significantly reducing margin migration compared to the core (p<0.001). CONCLUSION Stiffer GBM margins promote the formation of aggressive phenotypes through MM. Targeting YAP1 with Verteporfin, a readily available drug, presents a promising strategy to halt GBM invasion and improve patient outcomes.

CSIG-23. CYTOMEGALOVIRUS-INFECTED HUMAN GLIOBLASTOMA CELL LINES SHOW AN AGGRESSIVE PHENOTYPE ASSOCIATED WITH UPREGULATION OF IL-6/STAT3 AND AKT SIGNALING

Abstract BACKGROUND Cytomegalovirus (CMV) has been implicated in glioblastoma (GBM) pathogenesis by affecting stemness, angiogenesis and immune pathways. Clinical trials targeting CMV in GBM patients have shown some early promise, and CMV seropositivity has been associated with poorer outcomes. However, the underlying mechanisms remain unclear. Here we investigated the effects of CMV infection on critical signaling pathways in GBM (IL6/STAT3, and Akt signaling) based on the hypothesis that CMV may contribute to poorer outcomes in GBM by increasing oncogenic signaling. MATERIALS AND METHODS Human U251 and LN229 GBM cell lines were infected with mCherry expressing human CMV TB40 strain at a multiplicity of infection (MOI) of 0.5. We performed basic phenotypic studies in vitro and investigated the status of IL6/STAT3, and Akt signaling by Western blotting. RESULTS Both LN229 and U251 cell lines were readily infectable by CMV. Infection of U251 cells was over 90% and in LN229 cells was approximately 60%. Interestingly expression of CMV was sustained over many passages in these cell lines. Infection was also verified by the presence of the CMV pp65 protein assessed by Western blotting. Measurement of cell proliferation indicated faster growth after CMV infection. Interrogation of key pro-oncogenic signaling pathways in GBM revealed a robust upregulation of IL6, as well as phospho(Tyr705)-STAT3 and phospho(Thr308)-Akt. This elevation of pro-oncogenic signaling pathways was observed in both cell lines compared with controls. CONCLUSIONS Here we show for the first time that infection of human GBM cell lines with CMV results in a more aggressive phenotype associated with upregulation of IL6/STAT3 signaling as well as a significant increase in phospho-Akt levels. We are currently studying sensitivity to standard therapies and additional molecular changes in these cells. These data support the hypothesis that CMV causes more aggressive disease and that CMV is a relevant therapeutic target in GBM.

Targeting N-methyl-lysine histone demethylase KDM4 in cancer: natural products inhibitors as a driving force for epigenetic drug discovery.

KDM4A-F enzymes are a subfamily of histone demethylases containing the Jumonji C domain (JmjC) using Fe(II) and 2-oxoglutarate for their catalytic function. KDM4 enzymes are overexpressed or deregulated in cancer, thus leading to alteration in chromatin structure and transcriptional defects. As KDM4 enzymes have been associated with malignancy, they may represent novel targets for developing innovative therapeutic tools to treat different solid and blood tumors, of note, KDM4A is the isozyme most frequently associated with aggressive phenotypes of these tumors. To this aim, industrial and academic medicinal chemistry efforts have identified different KDM4 inhibitors. In most cases, these are pan-KDM4 inhibitors, with low selectivity against other Jumonji family members. The pharmacophoric features of the inhibitors frequently include a chelating group capable of coordinating the catalytic iron within the active site of the KDM4 enzyme. Nonetheless, non-chelating compounds have also demonstrated promising inhibitory activity, suggesting potential flexibility in the drug design. Several natural products, containing monovalent or bivalent chelators, have been identified as KDM4 inhibitors, albeit with a micromolar inhibition potency. This highlights the potential for leveraging them as templates for the design and synthesis of new derivatives, exploiting nature's chemical diversity to pursue more potent and selective KDM4 inhibitors.

Integrated single-cell transcriptomic analyses identify a novel lineage plasticity-related cancer cell type involved in prostate cancer progression

Cancer cell plasticity is the ability of neoplastic cells to alter their identity and acquire new biological properties under microenvironmental pressures. In prostate cancer (PCa), lineage plasticity often results in therapy resistance and trans-differentiation to neuroendocrine (NE) lineage. However, identifying the cancer cells harboring lineage plasticity-related status remains challenging. Based on 13 multi-center human PCa bulk transcriptomic cohorts (samples=3314) and 9 bulk transcriptomic datasets derived from PCa experimental models, we established an integrated lineage plasticity-related gene signature, termed LPSig. Leveraging this gene signature, AUCell enrichment analysis was applied to identify the cell population with high lineage plasticity from a comprehensive single-cell RNA-sequencing (scRNA-seq) meta-atlas assembled by us, which consisted of 10 public human PCa scRNA-seq datasets (samples=93, cells=222,529). Moreover, additional scRNA-seq dataset of human PCa, multiplex immunohistochemistry staining for human PCa tissues, invitro and invivo functional experiments, as well as qPCR and Western blot analyses were employed to validate our findings. We found that LPSig could finely capture the dynamics of tumor lineage plasticity throughout the progression of PCa, accurately estimating the status of lineage plasticity. Based on LPSig, we identified a previously undefined minority population of lineage plasticity-related PCa cells (LPCs) from the human PCa scRNA-seq meta-atlas assembled by this study. Furthermore, in-depth dissection revealed pivotal roles of LPCs in trans-differentiation, tumor recurrence, and poor patient survival during PCa progression. Furthermore, we identified HMMR as a representative cell surface marker for LPCs, which was validated using additional scRNA-seq datasets and multiplexed immunohistochemistry. Moreover, HMMR was transcriptionally inhibited by androgen receptor (AR), and was required for the aggressive adenocarcinoma features and NE phenotype. Our study uncovers a novel population of lineage plasticity-related cells with low AR activity, stemness-like traits, and elevated HMMR expression, that may facilitate poor prognosis in PCa. This work was supported by National Key R&D Program of China (2022YFA0807000), National Natural Science Foundation of China (82160584), Advanced Prostate Cancer Diagnosis and Treatment Technology Innovation Team of Kunming Medical University (CXTD202216), and Reserve Talents of Young and Middle-aged Academic Leaders in Yunnan Province (202105AC160013).

RNA methylase RBM15 facilitates malignant progression of colorectal cancer through regulating E2F2 in an m6A modification-dependent manner.

Recently, RBM15 has emerged as an oncogenic factor in a majority of tumors. However, the mechanism is unclear that accounts for how RBM15-induces colorectal cancer (CRC) progression and it is in need of further study. We determined RBM15 expression through the UALCAN database and RT-qPCR. The role of RBM15 in inducing the malignant and aggressive cancerous phenotype was characterized based on the results of the western blot, RT-qPCR, CCK-8 and transwell assays. The target genes of RBM15 were screened by LinkedOmics. m6A methylation kit was applied to analyze the methylation levels of mRNA. SRAMP website was employed to predict m6A sites of targeted mRNA. RIP, dual luciferase reporter gene and actinomycin D assay were conducted to verify the interactions between RBM15 and its targeted gene, and the presence of m6A modification site of its targeted mRNA, respectively. We confirmed the augmentation of RBM15 expression in CRC, which also has a high clinical diagnostic value for CRC. Functionally, RBM15 silencing clearly restrained malignant cellular processes in CRC cells. Mechanistically, RBM15 bound to E2F2 which increased its m6A binding and stabilized the corresponding E2F2 mRNA formation. Excessive E2F2 largely restored the repression malignant phenotype of tumor cells caused by RBM15 silencing. RBM15 regulated E2F2 in an m6A modification-dependent manner thereby boosting malignant cellular processes in CRC. The RBM15/E2F2 axis may be a novel target for CRC therapy.

Ferrocenyl Aminocresols Display Multimodal Activity Against Triple‐Negative Breast Cancer Cells In Vitro

AbstractTriple‐negative breast cancer (TNBC) lacks expression of the oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu), has an aggressive tumor phenotype, shows only a partial response to chemotherapy, and lacks clinically established targeted therapies. Therefore, there is a need to develop more effective drugs for the treatment of TNBC. The ferrocenyl benzoxazine and α‐aminocresols class of compounds gave a potential source of multimodal inhibitors of cancer based on previous studies. In this study, a set of ferrocenyl benzoxazines and α‐aminocresols were screened and characterized as potential inhibitors of TNBC in vitro. A panel of 11 compounds was screened for selective cytotoxicity to cancer cells over normal cell equivalents. Focusing on the previously proposed modes of action of their building blocks, α‐aminocresols 3a and 3b exhibited significant DNA binding capabilities and caused robust DNA damage in TNBC cells. In addition, both compounds exhibited significant ROS generation capability; however, introducing a ROS quencher in a cell viability assay only partially rescued the cells from the cytotoxicity effects of the α‐aminocresols. This, together with the observation that compounds 3a and 3b triggered significant protein aggregation in HCC1806 cells, supports a mixed mode of action for these compounds.

Enhanced cancer cell proliferation and aggressive phenotype counterbalance in breast cancer with high BRCA1 gene expression.

While comprehensive research exists on the mutation of the DNA repair gene BRCA1, limited information is available regarding the clinical significance of BRCA1 gene expression. Given that cancer cell proliferation is aggrevated by DNA repair, we hypothesized that high BRCA1 gene expression breast cancer (BC) might be linked with aggressive tumor biology and poor clinical outcomes. The cohorts: The Cancer Genome Atlas (TCGA, n = 1069), METABRIC (n = 1903), and SCAN-B (n = 3273) were utilzed to obtain data of 6245 BC patients. BC patients without BRCA1 mutation exhibited higher BRCA1 expression, which was associated with DNA repair functionality. However, no such correlation was observed with BRCA2 expression. The association of high BRCA1 expression with cancer cell proliferation was evidenced by significant enrichment of cell proliferation-related gene sets, higher histological grade, and proliferation score. Furthermore, increased levels of homologous recombination deficiency, intratumoral heterogeneity, and altered fractions were associated with high BRCA1 expression. Moreover, BC with high BRCA1 expression exhibited reduced infiltration of dendritic cells and CD8 T-cells, while showing increased infiltration of Th1 cells. Surprisingly, BRCA1 expression was not associated with the survival of BC irrespective of the subtypes. Conversely, BC with low BRCA1 expression enriched cancer aggravating pathway gene sets, such as Cancer Stem Cell-related signaling (NOTCH and HEDGEHOG), Angiogenesis, Epithelial-Mesenchymal Transition, Inflammatory Response, and TGF-beta signaling. Despite being linked to heightened proliferation of cancer cells and unassertive phenotype, BRCA1 expression did not show any association with survival in BC.

TGF-β Signaling Loop in Pancreatic Ductal Adenocarcinoma Activates Fibroblasts and Increases Tumor Cell Aggressiveness.

The interaction between cancer cells and cancer-associated fibroblasts (CAFs) is a key determinant of the rapid progression, high invasiveness, and chemoresistance of aggressive desmoplastic cancers such as pancreatic ductal adenocarcinoma (PDAC). Tumor cells are known to reprogram fibroblasts into CAFs by secreting transforming growth factor beta (TGF-β), amongst other cytokines. In turn, CAFs produce soluble factors that promote tumor-cell invasiveness and chemoresistance, including TGF-β itself, which has a major role in myofibroblastic CAFs. Such a high level of complexity has hampered progress toward a clear view of the TGFβ signaling loop between stromal fibroblasts and PDAC cells. Here, we tackled this issue by using co-culture settings that allow paracrine signaling alone (transwell systems) or paracrine and contact-mediated signaling (3D spheroids). We found that TGF-β is critically involved in the activation of normal human fibroblasts into alpha-smooth muscle actin (α-SMA)-positive CAFs. The TGF-β released by CAFs accounted for the enhanced proliferation and resistance to gemcitabine of PDAC cells. This was accompanied by a partial epithelial-to-mesenchymal transition in PDAC cells, with no increase in their migratory abilities. Nevertheless, 3D heterospheroids comprising PDAC cells and fibroblasts allowed monitoring the pro-invasive effects of CAFs on cancer cells, possibly due to combined paracrine and physical contact-mediated signals. We conclude that TGF-β is only one of the players that mediates the communication between PDAC cells and fibroblasts and controls the acquisition of aggressive phenotypes. Hence, these advanced in vitro models may be exploited to further investigate these events and to design innovative anti-PDAC therapies.

Distribution and inflammatory potential of hepatitis C virus genotypes in the United States, 2011-2020.

HCV is marked by genetic diversity that impacts disease progression and outcome. Using the NHANES data from 266 HCV-infected adults (2011-2020), this study infers that genotype 1a is the most prevalent (60.2%). Genotype 3 was associated with higher transaminase levels, though not statistically significant. These findings suggest a more aggressive phenotype for genotype 3. Despite pan-genotypic treatment guidelines, this underscores the importance of continued HCV genotype surveillance and consideration for genotype-specific treatment and monitoring strategies.