Oncogene

Platinum resistance remains a major barrier in Ovarian cancer (OC) treatment[1]. While hyperactivation of DNA damage response (DDR) is a hallmark of chemoresistance[2], the underlying epigenetic mechanisms driving this adaptation remain poorly understood. Here, we identify a novel post-transcriptional regulatory axis involving miR-221-5p that governs two critical DDR effectors: RAD18, which mediates DNA damage tolerance through trans-lesion synthesis (TLS)[3][4], and RAD51, the central recombinase for homologous recombination (HR)[5][6]. Although the miR-221/222 cluster is traditionally categorized as oncogenic[7][8], we demonstrate that the miR-221-5p arm functions as a potent tumor suppressor in OC. Bioinformatic and luciferase reporter assays confirmed that miR-221-5p directly targets the 3'UTRs of both RAD18 and RAD51. In OC clinical specimens and cell lines, miR-221-5p downregulation inversely correlates with RAD18/RAD51 expression. Functionally, miR-221-5p restoration suppressed platinum-induced PCNA mono-ubiquitination and HR, inducing a "functional BRCAness" that sensitized both established and patient-derived primary OC cells to carboplatin and PARP inhibition. Furthermore, in vivo disseminated xenograft models demonstrated that stable miR-221-5p expression significantly reduced tumor burden. Collectively, our results delineate a novel regulatory mechanism where loss of miR-221-5p drives chemoresistance by derepressing the RAD18/RAD51 axis, identifying this axis as a promising therapeutic target.

Cancer-testis antigens (CTAs) are germ cell-restricted proteins aberrantly expressed in diverse malignancies, yet whether these proteins contribute to tumor progression remains poorly defined. The CTA Testis-Specific Serine Kinase 6 (TSSK6) is frequently expressed in colorectal cancer (CRC), where it promotes key hallmarks of tumor progression, including anchorage-independent growth, invasion, and in vivo tumor formation. However, the signaling network by which ectopic TSSK6 drives these phenotypes has not been established. Here, we define the signaling pathways regulated by TSSK6 in CRC cells. We demonstrate that TSSK6 promotes focal adhesion kinase (FAK) activation, leading to enhanced STAT3 Ser727 phosphorylation and increased STAT3-dependent transcription. Transcriptomic analyses revealed induction of gene programs enriched for extracellular matrix remodeling, cytoskeletal organization, adhesion, and motility in a STAT3-dependent manner. Disruption of the FAK-STAT3 signaling axis abrogated anchorage-independent growth and invasive outgrowth in a spheroid model. Collectively, these findings demonstrate that aberrant expression of a germline-restricted kinase promotes focal adhesion signaling, which activates STAT3-dependent transcriptional programs that promote anoikis resistance and invasive behavior in CRC.

Since its discovery in a metastatic lymph node in breast cancer patients, LIM and SH3 Domain Protein (LASP1) has been shown to be over-expressed in and promote the progression of various cancers. We recently demonstrated that LASP1 is highly expressed in human Papillomavirus positive (HPV+) cervical cancers where it promotes cell proliferation and invasion. Importantly, we showed that the HPV E7 oncoprotein increased LASP1 expression by downregulating the microRNA miR-203, which directly targets the LASP1 mRNA 3UTR. However, whether LASP1 is regulated by other mechanisms in HPV+ cervical cancers is unclear. Here, we demonstrate an additional mechanism by which HPV E7 regulates LASP1 transcription. Our data demonstrates an important the role for Rb/E2F1 signalling in promoting LASP1 expression in HPV+ cervical cancer cells. Mechanistically, E7-mediated Rb binding and degradation is required for E7-driven LASP1 promoter activity. Overexpression of Rb decreased LASP1 promoter activity, LASP1 mRNA expression and LASP1 protein levels, whereas E2F1 expression promoted LASP1 expression. Importantly, E2F1 directly bound to the LASP1 promoter region and the E2F1 binding sites are essential for LASP1 expression in HPV+ cervical cancer cells. Finally, we demonstrate that LASP1 can partially rescue the growth defects observed in E2F1 knockdown cervical cancer cells. Taken together, our data show that HPV E7 regulates LASP1 expression via the Rb/E2F1 signalling pathway. In combination with our previous work, our studies demonstrate that HPV E7 employs multiple mechanisms to drive LASP1 expression, reinforcing the importance of LASP1 in HPV+ cervical cancer.

The scaffold protein FRS2 is central to FGFR signaling, linking receptor activation to MAPK/ERK and PI3K/AKT pathways. Elevated FRS2 expression correlates with aggressive tumor phenotypes and poor prognosis across multiple cancers, including the pediatric cerebellar tumor medulloblastoma (MB). Here, we characterized FRS2s subcellular localization and interactome in MB cells, employing live-cell imaging, phosphoproteomics, immunoprecipitation, and APEX2-based proximity labeling. We found that increased FRS2 expression is associated with increased motile and invasive behavior in MB tumor cells. We furthermore identified novel candidate FRS2-associated proteins involved in actin cytoskeleton remodeling, cell junction assembly, and translation initiation, which indicate a growth factor-dependent reorganization of the FRS2 signalosome. Our data furthermore indicate a regulatory role of FRS2 in directing subcellular distribution of the cell junction and cell motility regulator TJP1. Our findings highlight the relevance of FRS2 as a mediator of cell motility and invasiveness and provide candidate proteins associated with FRS2 that are involved in cellular processes governing migration and invasion. This study thus provides a framework for exploring the FRS2 interactome as a possible target to attenuate FGFR-driven oncogenic processes with next-generation therapeutic strategies.

Cancer metabolism rewiring is one of the hallmarks of cancer, enabling cancer cell survival in a nutrient deprived microenvironment. Key to this is nutrient scavenging where cancer cells rely on extracellular proteins, including extracellular matrix (ECM) components, to sustain their proliferation. ECM uptake is mediated by 2{beta}1 integrin, however it is not clear how this process is controlled by nutrient availability. Here we demonstrated that amino acid starvation promoted ECM internalisation, by inducing the expression of 2 integrin. Mechanistically, starvation-driven RAS/MAPK pathway activation in cells harbouring oncogenic RAS mutations and mTOR inhibition increased 2 integrin, while the GCN2-depedent integrated stress response was not required. Functionally, elevated 2 integrin levels promoted cell adhesion and migration in nutrient starved cells. Finally, 2 integrin was found upregulated in pancreatic tumours and correlated with poor prognosis in pancreatic adenocarcinoma patients. Together, these data indicate that the nutrient- starved pancreatic cancer microenvironment synergises with KRAS mutation to drive pancreatic cancer aggressiveness.

Activating mutations in PI3K are one of the most frequent mutations in breast cancer and are associated with worse patient outcomes in many breast cancer subtypes. Despite intense interest, cancer treatments that target the PI3K pathway have been only modestly effective due to intrinsic and acquired resistance mechanisms which reactivate PI3K signaling. Here, we characterize a feedback mechanism by which PI3K pathway inhibitors increase insulin receptor substrate 2 (IRS2) abundance and demonstrate the role of IRS2 in promoting resistance to these drugs. In PIK3CA mutant breast tumors and cell lines, there is a significant reduction in IRS2 mRNA and protein abundance which is reversed by PI3K pathway inhibition and mediated by the transcription factor FOXO3. PIK3CA mutations do not alter IRS1 expression. IRS2 confers resistance to PI3K pathway inhibition by sustaining PI3K signaling in PIK3CA mutant, but not wild-type breast cancer cells. Increased IRS2 abundance also correlates with PI3K pathway inhibitor resistance across PI3K mutant cancer cell lines from a variety of tissues. The clinical relevance of these findings is highlighted by the frequency of PI3K mutations in cancer and the identification of a new target to address the challenges associated with prior efforts to block the reactivation of PI3K signaling during PI3K inhibition.

Pancreatic ductal adenocarcinoma (PDAC) frequently metastasizes to the liver, which drives patient mortality. CA19-9 is elevated in most PDAC tumors and is widely used as a clinical biomarker. Elevated serum levels are associated with poor outcomes. However, whether CA19-9 functionally contributes to metastatic progression has not been fully defined, in part because mice lack endogenous CA19-9 expression. Here, using syngeneic murine PDAC cells engineered to express CA19-9, we investigated its functional role in liver metastasis. In splenic injection models, CA19-9 expression markedly increased liver metastatic burden by promoting both metastatic seeding and subsequent metastatic outgrowth. In vitro, CA19-9 enhanced tumor cell adhesion to endothelial cells through interaction with E-selectin. Metastatic seeding of CA19-9-expressing cells was reduced by genetic deletion of E-selectin or antibody neutralization of either CA19-9 or E-selectin in vivo. Therapeutic targeting of CA19-9 with a neutralizing antibody markedly reduced liver metastatic burden after metastatic seeding. CA19-9 expression increased AKT signaling in PDAC cells and liver metastases, and CA19-9 levels correlated with AKT activation in human PDAC tissues. These findings show that CA19-9 promotes PDAC liver metastasis through E-selectin-dependent metastatic seeding and AKT-associated metastatic outgrowth, highlighting CA19-9 as a functional mediator of PDAC metastasis and a potential therapeutic target.

TP53 mutations occur in 80-90% of triple-negative breast cancers (TNBCs) and drive genomic instability and metastatic progression. Poly (ADP-ribose) polymerase (PARP) is critical for DNA repair and replication fork stability. How oncogenic signaling influences PARP function to sustain proliferation during replication stress remains unclear. Mutant p53 (mtp53) R273H associates tightly with chromatin, forms complexes with PARP, and enhances PARP recruitment to replication forks [1-3]. The C-terminal region of mtp53 mediates mtp53-PARP and mtp53-Poly (ADP-ribose) (PAR) interactions that facilitate S phase progression [4, 5]. The PARP inhibitor talazoparib (TAL) combined with the alkylating agent temozolomide (TMZ) produces synergistic cytotoxicity selectively in mtp53, but not wild-type p53 (wtp53), breast cancer cells and organoids. Herein we evaluated the mechanism of mtp53-associated cell death and tested if this could translate to a preclinical xenograft model. We found that TMZ+TAL treatment induced elevated cleaved PARP and {gamma}H2AX and reduced the metastasis-promoting oncoprotein MDMX. In orthotopic xenografts expressing mtp53 R273H, but not wtp53, combination therapy significantly decreased circulating tumor cells (CTCs) and lung metastases. Transcriptomic profiling of tumors from combination treated animals demonstrated downregulation of MDMX, VEGF, and NF-{kappa}B, consistent with the observed suppression of CTCs and lung metastasis, and increased {gamma}H2AX, indicative of replication stress in mtp53 xenografts. Inhibition of metastasis was also observed in mtp53 R273H WHIM25 and p53-undetectable WHIM6 TNBC patient-derived xenografts (PDX). The mtp53 C-terminal domain (347-393) demonstrated a critical tumor promoting function, as CRISPR-mediated deletion impaired replication fork progression, tumor growth, and metastatic dissemination. DNA fiber combing showed that expression of full-length mtp53 R273H, but not C-terminal deleted {Delta}347-393, supported sustained single-stranded DNA gaps (ssGAPs) following Poly (ADP-ribose) glycohydrolase (PARG) inhibition. These findings support that mtp53 uses C-terminal amino acids to exploit PARP to enable replication stress adaptation and that mtp53 is a predictive biomarker for combined PARP inhibitor and DNA damaging therapies targeting TNBC. Significance statementTP53 mutations are the most common genetic alterations in TNBC and a major driver of replication stress and metastasis. This study shows that missense mutant p53 uses C-terminal amino acids to reprogram PARP activity to maintain tumor cell survival under replication stress. We demonstrate that p53 status governs the response to combined PARP inhibitor (PARPi) and DNA-damaging chemotherapy, establishing an additional molecular basis beyond BRCA1 mutations for treating TNBC with PARPi therapy. These findings reveal a previously unrecognized mechanism by which the mutant p53-PARP axis enables replication stress tolerance and drives cancer metastasis. We show mutation of p53 in TNBC provides an additional biomarker-guided framework to improve PARPi therapeutic outcomes.

The formation of the premetastatic niche prepares distant tissues for tumor cell engraftment. Endothelial cells are critical mediators of premetastatic niche formation, orchestrating extravasation of circulating tumor cells and critical pro-tumor immune cells, such as neutrophils. In mouse models of breast cancer, we show that primary tumors upregulate the non-signaling chemokine receptor ACKR1 in the endothelium of the lung premetastatic niche. ACKR1-expressing venules were found to be preferential sites of neutrophil and tumor cell localization within lung tissue. A newly generated conditional ACKR1 allele was used to show that endothelial-specific removal of ACKR1 expression significantly reduces metastatic engraftment in the lung. When ACKR1 is activated by tumor-secreted factors, endothelial ACKR1 functions to promote neutrophil recruitment within the lung parenchyma. We conclude that ACKR1 is a critical component of the endothelial response to tumors at the metastatic site of the lung, leading to neutrophil recruitment and promotion of tumor cell metastasis. SUMMARYEndothelial cells play critical roles in breast cancer metastasis. ACKR1 is upregulated in the endothelium of the lung metastatic niche in response to primary mammary tumors. Endothelial ACKR1 expression was found to promote neutrophil infiltration into the metastatic niche and support breast tumor cell metastasis to the lung.

Withdrawal StatementThe authors have withdrawn this manuscript to address issues related to data-use permission and authorship review. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

Chromophobe renal cell carcinoma (ChRCC) accounts for 5% of all renal cancer cases. Despite its generally indolent behavior and low mutational burden, there is no targeted therapy for metastatic ChRCC. Profilin-1 (Pfn1), a cytoskeletal regulator of actin and tubulin dynamics, has emerged as a potential oncogenic driver in several cancers including RCC, but its role in ChRCC, remains undefined. We observed elevated Pfn1 expression in stage IV ChRCC patients, implicating Pfn1 in advanced disease progression. To investigate this, we manipulated Pfn1 expressions in two ChRCC cell lines UOK276 and RCJ41M. Pfn1 knockdown (KD) significantly reduced proliferation, invasion, and colony formation, whereas Pfn1 overexpression (OE) in UOK276 enhanced ChRCC aggressive phenotypes. Pharmacological inhibition of Pfn1 significantly suppressed proliferation and clonogenic growth in both cell lines. Additionally, Pfn1 KD increased intracellular ROS accumulation, while overexpressed reduced ROS levels, linking cytoskeletal regulation to oxidative stress control. Together, these findings position Pfn1 as a critical mediator of ChRCC progression, linking cytoskeletal remodeling to aggressive tumor behavior. This work highlights Pfn1 as a potential therapeutic target and establishes a framework for cytoskeletal-focused strategies in advanced ChRCC.

Aberrant expression of Long Interspersed Element-1 (LINE-1/L1) retrotransposons is increasingly linked to genomic instability in cancer, particularly in the context of compromised p53 function. The endonuclease (EN) domain of the LINE-1 ORF2 protein (ORF2p) generates DNA strand breaks, yet its role in shaping downstream chromatin and transcriptional responses remains poorly defined. Here, we investigate the impact of ORF2p-EN activity on DNA damage response signalling and epigenomic remodeling in isogenic wild-type and p53-deficient A375 melanoma cells using a L1 expression system. ORF2p-EN expression induced activation of ATM dependent DNA damage signalling, as evidenced by increased {gamma}H2AX accumulation. This response was accompanied by altered levels of the DNA repair factor XRCC5, consistent with engagement of non-homologous end joining pathways. Notably, EN-associated DNA damage correlated with increased p300 activity and enhanced H3K27ac enrichment at regulatory regions, suggesting coupling between DNA damage signalling and chromatin acetylation. Pharmacological inhibition of ATM attenuated both {gamma}H2AX accumulation and H3K27ac levels, supporting a model in which chromatin remodeling occurs downstream of DNA damage signalling. Collectively, our findings position ORF2p endonuclease activity as an initiating source of DNA damage that is functionally linked to chromatin remodeling and transcriptional reprogramming, with p53 acting as a critical modulator of this axis. These results provide mechanistic insight into how LINE-1 activation may contribute to oncogenic gene expression programs in cancer.

During breast cancer metastasis, tumor cells migrate toward intratumoral blood vessels and intravasate through stable structures known as TMEM (Tumor Microenvironment of Metastasis) doorways. TMEM doorways, composed of a Mena-expressing tumor cell, a Tie2hi/VEGFhi macrophage, and an endothelial cell, are clinically validated prognostic markers of distant metastasis in breast cancer and represent the exclusive sites of tumor cell intravasation. We previously demonstrated that Tie2 signaling is essential for TMEM doorway function and tumor cell intravasation. In this study, we investigated how Tie2 signaling promotes tumor cell intravasation and metastasis. Because all three TMEM doorway-associated cell types can express Tie2, we sought to determine which of these cells contribute to the Tie2 signaling-dependent vascular opening at TMEM doorways and tumor cell dissemination. We found that endothelial cells associated with TMEM doorways secrete Ang2, which stimulates VEGF-A expression in Tie2hi macrophages. Elevated VEGF-A levels at TMEM doorways increase vascular permeability, facilitating tumor cell entry into the bloodstream. Using tissue staining and line-scan analysis of Tie2 and lineage markers in human and mouse breast cancer models, we observed Tie2 expression in macrophages, tumor cells, and endothelial cells. To assess functional contributions, we selectively disrupted Tie2 in macrophages, endothelial cells, and cancer cells using CRISPR-Cas9 and RNAi approaches and tested in which of these cell-knockouts of Tie2 expression affected transendothelial migration in vitro. Macrophage-specific Tie2 deletion had the greatest impact on tumor cell intravasation. To confirm this finding in vivo, we generated a mouse model with inducible, macrophage-specific Tie2 knockout. Acute, targeted loss of Tie2 specifically in macrophages significantly reduced TMEM doorway associated vascular opening and tumor cell intravasation. Together, these findings establish macrophage Tie2 signaling as a critical driver of TMEM doorway-mediated vascular permeability and metastatic dissemination in breast cancer.

Epithelial-mesenchymal transition (EMT) and glycolytic metabolism are well-characterized drivers of cancer progression and metastasis. However, most primary breast tumors and metastases express E-cadherin and the epithelial phenotype is associated with mitochondrial oxidative metabolism, yet the causality and relevance of these relationships and their underlying mechanisms remain poorly understood. Using a 3D culture model with mechano-stimulation, we found that E-cadherin promotes mitochondrial oxidative phosphorylation (OXPHOS) while reducing oxidative stress. Through pharmacological and genetic manipulations of inflammatory breast cancer (IBC) and/or triple negative breast cancer (TNBC) cell lines, we identified pyruvate carboxylase (PC) as an E-cadherin effector. Critically, restoring PC in E-cadherin-silenced cells rescued mitochondrial oxygen consumption and protection from oxidative stress. Co-expression of E-cadherin and PC was confirmed in breast cancer tissues and experimental lung metastases. Mechanistically, E-cadherin induced PC expression and OXPHOS via AKT-mediated activation of YAP/ /TEAD transcription factors, which are better known as supporting EMT. Clinically relevant AKT and TEAD inhibitors reduced both PC expression and oxidative respiration. Importantly, PC inhibition as monotherapy attenuated established experimental lung metastases and primary tumor burden in mice. Taken together, these findings reveal that E-cadherin-mediated cell-cell adhesions directly support mitochondrial metabolism through AKT-YAP/TEAD-PC signaling, identifying a therapeutic vulnerability in metastatic epithelial TNBC.

The RNA polymerase-associated factor 1 complex (PAF1C) is an evolutionarily conserved transcription elongation complex that regulates RNA polymerase II-mediated transcription and chromatin modification. LEO1, a core subunit of PAF1C, has been implicated in developmental gene regulation, WNT signaling, and leukemogenesis; however, its role in solid tumor progression remains poorly understood. In this study, we found that although LEO1 expression is generally elevated in colorectal cancer (CRC), its expression is reduced in stage IV tumors and is associated with poor clinical outcomes. To investigate its function, we established LEO1 -deficient HCT116 cell line and performed transcriptomic analyses. Loss of LEO1 suppressed epithelial differentiation and developmental gene programs while inducing cell cycle delay. Despite these changes, LEO1-deficient cells exhibited aggressive phenotypes, including enlarged nuclei and increased expression of migration-associated genes, which were further enhanced under glucose deprivation. Motif analysis identified FOXM1 as a key regulator of these migration-related genes. Mechanistically, LEO1 deficiency promoted accelerated transcriptional activation of GRP78, a central regulator of endoplasmic reticulum (ER) stress adaptation. GRP78 was required for survival under ER stress conditions, and its inhibition suppressed both migration and migration-associated gene expression. In addition, transcriptomic analyses revealed upregulation of cholesterol metabolism-related genes in LEO1-deficient cells. Consistently, treatment with the HMG-CoA reductase inhibitor atorvastatin selectively impaired their survival, indicating cholesterol metabolic dependency. Collectively, these findings demonstrate that LEO1 loss promotes ER stress-adapted migration and cholesterol metabolic dependency in CRC, suggesting that these pathways may represent therapeutic vulnerabilities in metastatic LEO1-low CRC.

Metastasis remains the primary cause of cancer-related morbidity and mortality, despite significant advances in targeted therapies. Although metastatic dissemination requires tumor cells to escape the primary lesion and colonize distant organs, the mechanisms by which primary tumor cells gain metastatic competence remain poorly understood. Increasing evidence demonstrates that fusion of tumor (i.e., neoplastic) and immune (e.g., macrophages) cells generate a distinct population of tumor-immune hybrid cells with enhanced functional ability to migrate and disseminate into peripheral blood. Herein, our study investigates tumor-macrophage hybrid cells, an underexplored population of disseminated tumor cells, and their inherent heterogeneity and acquisition of molecular mechanisms underlying their dissemination as metastatic effectors in colorectal cancer (CRC). Through hybrid cell phenotyping utilizing integrative single-cell RNA sequencing (scRNA-seq), cyclic immunofluorescence (cyCIF) and functional assays with an in vitro model of CRC hybrid cells, we identify Runt-related transcription factor 1 (Runx1) as a central regulator of hybrid cell motility and invasion. Runx1 depletion in hybrid cells suppressed functional protease expression, chemotactic activity and extracellular matrix (ECM) invasion. Furthermore, pharmacologic inhibition of RUNX1 in an in vivo model reduced hybrid tumor growth and dissemination into peripheral blood, key attributes of metastatic spread of disease. In patients with CRC, RUNX1+ hybrid cells were identified in both primary tumor and peripheral blood, where circulating hybrid cells (CHCs) exhibited enriched migratory and epithelial-to-mesenchymal transition (EMT) phenotypes. Taken together, these findings reveal a mechanistic role for RUNX1 in driving invasive behavior of tumor-immune hybrids and highlight disseminated CHCs as an under-recognized contributor to metastatic spread and a promising noninvasive biomarker for tumor progression.

The PBAF is one of three biochemically distinct BAF chromatin remodelers in humans. We previously proposed the role of ARID2, a PBAF component, as a bonafide tumor suppressor in colorectal cancer (CRC). Here, we validated loss of tumor suppression under conditions of ARID2 deficiency emanating from a marked reduction in PBAF complex assembly resulting from destabilization of PBAF-specific components BRD7, PHF10, and PBRM1. Transcriptome profiling of ARID2 deficient CRC cells revealed perturbation of disease processes, including CRC and neurodegenerative disorders, as well as CRC relevant pathways including Wnt/{beta}-catenin signalling, but transcript levels of PBAF-specific components remained unchanged, confirmed by RT-qPCR and TCGA data analysis. Our study establishes ARID2 as a critical stabilizer of the PBAF complex of relevance to CRC.

Prostate cancer (PCa) is a lethal malignancy that displays profound resistance to immune checkpoint blockade (ICB), via mechanisms that are poorly understood. Here, we investigate the causes of CD8 T cell exhaustion and mechanisms of tumor progression in a PCa animal model, by single cell and spatial profiling, along a time course, following orthotopic transplantation of RB1/TP53/PTEN-deficient mouse organoids, competent to express neoantigens. The resulting tumors were castration resistant, consisting of largely basal and L2 malignant cells with upregulated inflammatory gene programs, and a specific spatial distribution of macrophages, cancer associated fibroblast (CAF) subtypes, and CD8 T-cells that was not previously reported. Using Zman-seq, we demonstrate that the effector function of tumor-infiltrating CD8 T cells was rapidly impaired as early as 24hrs after their infiltration, likely driven by signals from proinflammatory macrophages, Ccl2-Jak2+ inflammatory CAFs, and malignant basal cells, thus driving resistance to ICB. Interestingly, dual blockade of JAK1/2 and PD1 induced potent anti-tumor effects in tumor epithelial cells, decreased malignant epithelial cells and pro-inflammatory macrophages, and increased the proportion of normal (Pi16+) fibroblasts in the TME. Our results underscore the therapeutic potential of targeting JAK1/2 to enhance the efficacy of ICB, providing a rationale for clinical investigation of this combination in PCa.

To facilitate survival, migration and evasion of immune surveillance, cancer cells tightly coordinate the synthesis and trafficking of a diverse repertoire of proteins to their cell surface and the surrounding tumor microenvironment. A key mechanism underlying this process is the intracellular membrane trafficking pathways, including vesicular transport systems. There remains a paucity of mechanistic insight into the regulatory components that mediate nascent protein trafficking and their dysregulation in cancer. Herein, we investigate Tumor Protein D54 (TPD54) as a central regulator of intracellular protein transport that is exploited by melanoma cells to promote disease progression. Integrative analyses of patient-derived tumor tissue specimens show that the expression of TPD52L2 (the gene encoding TPD54) is frequently overexpressed in melanoma and correlates with adverse clinical outcomes, including reduced responses to immune checkpoint blockade. Mechanistic investigations further revealed that TPD54 maintains Golgi integrity and orchestrates trafficking of early endosomes, anterograde vesicles and extracellular vesicles. Functionally, TPD54 augments the secretion of pro-cancerous cytokines, increases the cell surface expression of adhesion-signaling receptors (e.g. integrin-{beta}1 and desmoglein-2), promotes melanoma cell migration and elevates their capability to undergo vasculogenic mimicry. Targeting TPD52L2 in two mouse models of melanoma (B16-F10 and HCmel12) showed significant attenuation of tumor growth, disrupted tumor vasculature, enhanced anti-tumor immunity with infiltration of CD8+ T cells and reduced metastatic disease. Collectively, these findings establish TPD54 as a critical and previously underappreciated regulator of protein trafficking in cancer cells that directly contributes to disease progression and highlights its potential as a novel therapeutic target to combat melanoma.

We previously reported that the murine lncRNA Epr is essential for maintaining colon mucosal integrity and permeability. Mice lacking Epr in the colon are more susceptible to colitis and tumor development. Additionally, we demonstrated that human EPR expression is reduced in ulcerative colitis and in a small cohort of colon adenocarcinoma patients. Here, we present evidence that human and mouse EPR share several key physiological features: preferential binding to the KH1 domain of their interacting protein, KSRP; specific expression in canonical and immature goblet cells of the large intestine; and a functional role in intestinal goblet cell development. The correlation between EPR levels and survival in large cohorts of metastatic colon adenocarcinoma patients, together with the capacity of human EPR to inhibit cell proliferation and induce apoptosis in two distinct human colon adenocarcinoma cell lines, suggests that EPR may serve as both a valuable prognostic marker for goblet cell-derived adenocarcinomas and a potential therapeutic target.