Cancer Letters

Chimeric antigen receptor (CAR) T cells have limited efficacy against solid tumors due to the hostile microenvironment. Circulating tumor cells (CTCs) are essential to metastasis, which is the cause of most of cancer-related death. Here, we generated GrB-CAR T cells targeting membrane-bound HSP70 (mHSP70), a highly tumor-specific antigen detected in numerous cancers. GrB-CAR T cells exhibited potent cytotoxicity against a broad spectrum of cancer cell lines and stem-like cancer cells in vitro and effectively inhibited xenograft tumor growth in vivo. Importantly, GrB-CAR T cells markedly decreased the number of CTCs and, therefore, hindered cancer metastasis in spontaneous metastasis models with uncontrollable primary tumor growth, a scenario commonly encountered in clinical trials of CAR T therapies for solid tumors. Furthermore, despite the 100% homology between human and macaque HSP70 protein, the autotransplantation of macaque T cells expressing human GrB-CAR did not cause any obvious toxic effects. These results not only demonstrate GrB-CAR T cells as a safe and effective tactic with broad-spectrum anticancer activity, but also offer strong experimental evidence and proof-of-concept validation for CAR T cell-mediated metastasis inhibition by targeting CTCs.

Triple-negative breast cancer (TNBC) is an aggressive form of cancer with poor prognosis. Beyond the absence of targeted therapies, a major challenge is its high recurrence rate, driven by the outgrowth of residual tumor cells that survive chemotherapy and persist during minimal residual disease (MRD). To monitor the therapy response of TNBC by enhanced intravital imaging, we established a clinically relevant combination chemotherapy protocol for the treatment of mouse mammary tumors engrafted from K14cre;Brca1F/F;Trp53F/F (KB1P) organoids engineered to express an mCherry-AkaLuc dual reporter (mCA-KB1P). Reproducible MRD and relapse response patterns with significantly extended relapse-free survivals were achieved with the TAC protocol, consisting of docetaxel, doxorubicin and cyclophosphamide. AkaLuc bioluminescence imaging (AkaBLI) of mCA-KB1P organoids verified the single-cell sensitivity of the system in vitro, and showed a detection limit of approximately 1000 cells in the mammary gland of living mice. Unexpectedly, mCA-KB1P organoids elicited an immune response, which necessitated the use of immunodeficient hosts for the longitudinal intravital monitoring of MRD. AkaBLI and an adapted TAC protocol enabled, for the first time, the non-invasive intravital tracking and an estimation of the number of surviving tumor cells in the MRD state following intensive chemotherapy. Engineering KB1P organoids for Histon2B-mCherry reporter expression (HmC-KB1P) enabled the estimation of tumor cell survival also in syngeneic immunocompetent hosts. Flow cytometry and histological analysis revealed that immunocompetent hosts harbored only a few residual cells at MRD, which exhibited a transient loss of epithelial characteristics, whereas immunodeficient hosts had a greater number of surviving cells with a maintained epithelial phenotype. These findings are consistent with the immune systems role in shaping phenotypic changes influencing survival following chemotherapy Together, the results demonstrate the utility of the AkaBLI system for rare tumor cell tracking and highlight the immune systems role in triggering adaptive responses to chemotherapy.

Leucine-rich repeat containing, G protein-coupled receptor 4, 5, and 6 (LGR4/5/6) are three homologous receptors that are co-expressed or alternately expressed at high levels in tumor cells of colorectal cancer (CRC) and high-risk neuroblastoma (NB). Simultaneous targeting of all three receptors may provide increased efficacy or overcome drug resistance due to tumor heterogeneity and cancer cell plasticity. LGR4/5/6 all bind to R-spondins (RSPOs) with high affinity and potentiate Wnt/{beta}-catenin signaling in response. Previously, we showed that a peptibody based on a mutant RSPO4 furin domain that bound to LGR4/5/6 without potentiating Wnt/{beta}-catenin signaling was able to deliver cytotoxins into cancer cells that express any of the three receptors. We have now generated a mutant RSPO2 furin domain that retains high affinity binding to LGR4/5/6 without signaling activity. Peptibodies based on this RSPO2 furin mutant were conjugated with either pyrrolobenzodiazepine dimer (PBD) or camptothecin derivative (CPT2), and the resulting peptibody-drug conjugates (PDCs) showed potent and specific cytotoxic activity in NB and CRC cell lines expressing any of LGR4/5/6 in vitro and robust anti-tumor activity in vivo. The results support the potential of RSPO2-based PDCs for the treatment of CRC, high-risk NB, and other cancers that express any of LGR4/5/6.

Lysosomal targeting chimeras (LYTACs) represent an emerging class of bifunctional molecules that bridge extracellular target proteins with intrinsic lysosome-targeting receptors (LTRs) on the cell surface, facilitating endocytic internalization and subsequent lysosomal degradation of the targets. However, the therapeutic potential of LYTACs has been limited by the scarcity of suitable intrinsic LTRs. We previously identified an aptamer, SAPT8, that selectively targets nucleolin, a shuttling protein overexpressed on the surface of pathogenic FLSs in rheumatoid arthritis (RA), and induced its lysosomal degradation. In this study, we repurposed SAPT8 as a tumor-targeting and lysosome-directed ligand, leveraging the elevated expression of NCL on tumor cell surfaces. By conjugating SAPT8 with either the c-Met-binding aptamer SL1 or the small molecule inhibitor Tepotinib, we engineered novel LYTACs that demonstrated potent tumor-targeting capability and induced concurrent degradation of both c-Met and NCL, leading to significant antitumor effects. Furthermore, fusion of SAPT8 with VEGFR-2-targeting aptamer Apt02 generated LYTACs that simultaneously degraded VEGFR-2 and NCL, effectively suppressing RA-FLS activity. These results establish SAPT8 as a versatile platform for developing next-generation LYTACs, overcoming current limitations in extracellular protein degradation by circumventing dependence on endogenous LTRs. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=69 SRC="FIGDIR/small/672993v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@975b74org.highwire.dtl.DTLVardef@f55565org.highwire.dtl.DTLVardef@b9639corg.highwire.dtl.DTLVardef@13aaba7_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundStandard of care therapies such as radiotherapy and chemotherapy have shown little efficacy against pancreatic ductal adenocarcinoma (PDAC). Immunotherapy is a newly emerging form of treatment that has shown promise; however, toxic systemic effects resulted in limited use in the clinic. Shifting from systemic to local delivery of cancer therapeutics reduces adverse systemic effects and increases response rates in multiple malignancies. Importantly, the effects of tumor-targeted therapies on distal tissues, such as the bone marrow, have not been thoroughly investigated. MethodsUsing a murine model of PDAC, we treated tumors with targeted stereotactic body radiation therapy (SBRT) and intratumoral interleukin-12 (IL-12). 13 days-13 months after tumor injection, the cells in the tumor, blood, and bone marrow were analyzed for therapy-induced changes. Hematopoietic cell numbers and lymphocytes were quantified by flow cytometry, and cytokine levels were quantified by enzyme-linked immunosorbent assays (ELISAs). ResultsWe demonstrated that although SBRT/IL-12 delivered locally to PDAC tumors successfully eradicated primary disease, it also induced significant acute and long-term effects in the bone marrow. Within days of intratumoral SBRT/IL-12 treatment, we observed acute lymphopenia in the blood, accompanied by an immunostimulatory response in the bone marrow characterized by an increase in hematopoiesis. Long-term effects included a decrease in hematopoietic stem cells (HSCs) and skewing toward a myeloid lineage bias, which could indicate premature aging of the HSC population. ConclusionsThese findings demonstrate that despite being locally delivered to the tumor, SBRT/IL-12 therapy exerts significant effects on the distal bone marrow, reinforcing the need for further investigations into the long-term systemic immunological outcomes of localized cancer treatments. Key MessagesWhat is already known on this topic: Systemic cancer therapies used to combat pancreatic ductal adenocarcinoma (PDAC) often induce toxic systemic effects. Local delivery of radiation and immunotherapy reduces adverse effects; however, the systemic spread of these therapies and the resulting effects on distal tissues such as the bone marrow have yet to be elucidated. What this study adds: Intratumoral delivery of stereotactic body radiation therapy (SBRT) and interleukin-12 (IL-12) augment hematopoiesis in the bone marrow soon after treatment and induce long-term alterations in the hematopoietic stem cells (HSCs). These effects are mainly a result of IL-12 that is transiently increased in the bone marrow after treatment. How this study might affect research, practice, or policy: Targeted SBRT/IL-12 therapy induces long-term systemic effects on the bone marrow, indicating the need for further investigation of the systemic spread of locally delivered therapeutics.

PurposeStem cells-like properties in cancer cells may confer cancer development and therapy resistance. With the advancement of multi-omics technology, the multi-omics-based exploration of cancer stemness has attracted certain interests. However, subtyping of cancer based on the combination of different types of stem cell signatures remains scarce. MethodsIn this study, 10,323 cancer specimens from 33 TCGA cancer types were clustered based on the enrichment scores of six stemness gene sets, representing two types of stem cell backgrounds: embryonic stem cells (ESCs) and hematopoietic stem cells (HSCs). ResultsWe identified four subtypes of pan-cancer, termed StC1, StC2, StC3 and StC4, which displayed distinct molecular and clinical features, including stemness, genome integrity, intratumor heterogeneity, methylation levels, tumor microenvironment, tumor progression, chemotherapy and immunotherapy responses, and survival prognosis. This subtyping method for pan-cancer is reproducible at the protein level. ConclusionOur findings indicate that the ESC signature is an adverse prognostic factor, while the HSC signature and ratio of HSC/ESC signatures are positive prognostic factors in cancer. The ESC and HSC signatures-based subtyping of cancer may provide insights into cancer biology and clinical implications of cancer.

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive disease characterized by its metastatic potential and chemoresistance. These traits are partially attributable to the highly tumorigenic pancreatic cancer stem cells (PaCSCs). Interestingly, these cells show unique features in order to sustain their identity and functionality, some of them amenable for therapeutic intervention. Screening of phospho-receptor tyrosine kinases revealed that PaCSCs harbored increased activation of anaplastic lymphoma kinase (ALK). We subsequently demonstrated that oncogenic ALK signaling drives tumorigenicity in PDAC patient-derived xenografts (PDXs) by promoting stemness through ligand-dependent activation. Indeed, the ALK ligands midkine (MDK) or pleiotrophin (PTN) increased self-renewal, clonogenicity and CSC frequency in several in vitro local and metastatic PDX models. Conversely, treatment with the clinically-approved ALK inhibitors Crizotinib and Ensartinib decreased CSC content and functionality in vitro and in vivo, by inducing cell death. Strikingly, ALK inhibitors sensitized chemoresistant PaCSCs to Gemcitabine, as the most used chemotherapeutic agent for PDAC treatment. Consequently, ALK inhibition delayed tumor relapse after chemotherapy in vivo by effectively decreasing the content of PaCSCs. In summary, our results demonstrate that targeting the MDK/PTN-ALK axis with clinically-approved inhibitors impairs in vivo tumorigenicity and chemoresistance in PDAC suggesting a new treatment approach to improve the long-term survival of PDAC patients. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/505637v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@21d661org.highwire.dtl.DTLVardef@1817b5eorg.highwire.dtl.DTLVardef@1ca97aaorg.highwire.dtl.DTLVardef@1ab5443_HPS_FORMAT_FIGEXP M_FIG C_FIG

ObjectiveGastric cancer (GC) tumors are highly heterogenous with different subpopulations of epithelial cells. We employed single cell RNA sequencing (scRNA-seq) to dissect the heterogeneity and identified subpopulations of cancer cells with stem-like properties. We further investigated their resistance to oxaliplatin chemotherapy and their contribution to gastric cancer outcome. DesignWe performed scRNA-seq on FACS sorted epithelial and immune cells from paired samples of GC tumors and normal adjacent tissues. We identified two epithelial subpopulations (STMN1+IQGAP3+ and STMN1+IQGAP3-) with stem-like properties. We characterized and compared them to known healthy gastric stem cell populations. We also cultivated GC derived organoids to study the chemoresistance of similarly marked populations. Lastly, we employed immunohistochemistry (IHC) staining to ascertain the predicted immunosuppressive interactions. ResultsThe STMN1+IQGAP3+ subpopulation showed a higher tumor mutation burden, upregulated proliferative pathways and transcriptomically resembled proliferative healthy gastric isthmus stem cells. The STMN1+IQGAP3- subpopulation were comparatively quiescent and transcriptomically resembled enteroendocrine cells. Both transcriptomic signatures were associated with worse mortality than other epithelial subpopulations with the quiescent being associated with the poorest patient survival. GC tissue derived organoids were dominated by STMN1+IQGAP3+ cells but the STMN1+IQGAP3- compartment was more resistant to chemotherapy. We also verified the likely suppression of CD8 T cell cytotoxicity by STMN1+IQGAP3+ cells through the NECTIN2/TIGIT interaction. ConclusionsCancer cells with stem-like characteristics are associated with poor survival through chemoresistance and immunosuppression. Reactivating the immune system through checkpoint blockade is an opportunity to eliminate these cells. What is already known on this topicMultiple gastric stem cell populations have been identified and linked to tumor initiation in rodent-based studies. However, none of them have been conclusively proven in human tumors. Isolating and characterizing tumor cells with stem-like properties will help shed light on their possible origin and possible mitigation strategies. What this study addsHere we identified two sets of stem-like gastric cancer cells that are associated with poorer patient prognosis. One set is highly proliferative and exhibits oxaliplatin susceptibility. It also engages in immunosuppressive interactions such as NECTIN2/TIGIT. The other set is quiescent and highly resistant to oxaliplatin. How this study might affect research, practice or policyThe transcriptome signatures of the identified stem-like cells can aid in patient prognosis and identify patients who can benefit from checkpoint blockade therapy to reactivate their immune response towards gastric cancer cells.

Autophagy, a key lysosomal degradation pathway regulating metabolic adaptation in cancer, plays fundamental roles in both the tumor and host stromal compartments during cancer progression. An important unanswered question is whether and how autophagy in specific host stromal elements, such as endothelial cells, influences metastasis. Here, we scrutinize how the genetic loss of autophagy in endothelial cells impacts primary tumor progression and metastasis in the Polyoma Middle T (PyMT) model of luminal B breast cancer. In both autochthonous and orthotopic mammary transplant models, PyMT primary tumor growth is significantly delayed upon endothelial cell Atg12 or Atg5 genetic deletion (Atg12 or 5 ECKO), which correlates with increased tumor cell apoptosis and HIF1 activation. In contrast, PyMT-bearing Atg12 ECKO mice exhibit increased metastasis, as well as higher rates of primary tumor and lung metastatic recurrence following surgical resection of PyMT primary tumors. Experimental metastasis assays further corroborate that loss of endothelial cell autophagy in Atg12 ECKO host animals promotes PyMT metastatic colonization and outgrowth, resulting in increased lung metastases compared to controls. Similarly, in the Rat Insulin Promoter T antigen pancreatic neuroendocrine tumor (RT2-PNET) model, endothelial cell deletion of Atg12 promotes liver micro-metastases. Taken together, these results from distinct preclinical cancer models reveal that endothelial cell autophagy suppresses metastatic seeding and progression and broach that autophagy inhibition in host endothelial cells may adversely influence the efficacy of systemic autophagy-lysosomal pathway inhibition in the clinical oncology setting.

Metastasis is the leading cause of cancer-related deaths, yet its regulatory mechanisms are not fully understood. Small-cell lung cancer (SCLC) is the most metastatic form of lung cancer, with most patients presenting with widespread disease, making it an ideal model for studying metastasis. However, the lack of suitable preclinical models has limited such studies. We utilized rapid autopsy-derived tumors to develop xenograft models that mimic key features of SCLC, including histopathology, rapid and widespread development of metastasis to the liver, brain, adrenal, bone marrow, and kidneys within weeks, and response to chemotherapy. By integrating in vivo lineage selection with comprehensive bulk and single cell multiomic profiling of transcriptomes and chromatin accessibility, we identified critical cellular programs driving metastatic organotropism to the liver and brain, the most common sites of SCLC metastasis. Our findings reveal the key role of nuclear-cytoskeletal interactions in SCLC liver metastasis. Specifically, the loss of the nuclear envelope protein lamin A/C, encoded by the LMNA gene, increased nuclear deformability and significantly increased the incidence of liver metastasis. Human liver metastases exhibited reduced LMNA expression compared to other metastatic sites, correlating with poorer patient outcomes and increased mortality. This study introduces novel preclinical models for SCLC metastasis and highlights pathways critical for organ-specific metastasis, offering new avenues for the development of targeted therapies to prevent or treat metastatic disease.

BackgroundTumor cells frequently develop immune resistance through interferon-{gamma} (IFN-{gamma})-induced PD-L1 expression, acquisition of cancer stem cell (CSC)-like features, and adaptation to hypoxia within the tumor microenvironment (TME). Although IFN-{gamma} activates both STAT1 and STAT3, how these pathways interact to regulate immune evasion under hypoxia remains unclear. MethodsUsing the MC38 murine colorectal cancer model and T cell-tumor spheroid co-culture assays, we examined how IFN-{gamma} signaling through STAT1 and STAT3 influences PD-L1 expression, CSC plasticity, and cytotoxic T cell function under normoxic and hypoxic conditions. Pharmacologic inhibitors and siRNA knockdown were used to dissect pathway function, and Niclosamide, an FDA-approved anthelmintic, was evaluated as a dual STAT1/STAT3 inhibitor. ResultsWe found that IFN-{gamma} primarily induced PD-L1 through STAT1 activation, while CSC plasticity was associated with STAT3 signaling. STAT1 and STAT3 displayed reciprocal regulation--blocking one enhanced activation of the other. Niclosamide effectively inhibited phosphorylation of both STAT1 and STAT3, which led to suppressed PD-L1 upregulation and reduced CSC enrichment. In addition, it also partially inhibited hypoxia-induced HIF-1 expression. In co-culture assays, Niclosamide improved T cell infiltration and reduced exhaustion under hypoxic conditions, resulting in improved T cell killing. ConclusionsOur findings identified Niclosamide as a potent dual STAT1/3 inhibitor capable of reversing IFN-{gamma} and hypoxia-driven immune evasion. Repurposing Niclosamide may represent a promising strategy to enhance the efficacy of immune checkpoint blockade in solid tumors. key messagesInterferon-{gamma} (IFN-{gamma}) enhances cytotoxic T cell function but also promotes tumor immune evasion by upregulating PD-L1 and inducing cancer stem cell- like properties. Our study identifies a reciprocal regulatory mechanism between STAT1 and STAT3 in IFN-{gamma}-treated tumor cells that shapes immune evasion outcomes. We demonstrate that Niclosamide, an FDA-approved anthelmintic, acts as a dual STAT1/STAT3 inhibitor, effectively suppressing PD-L1 induction, limiting cancer stemness, and reducing HIF-1 expression under hypoxia. Niclosamide also restores T cell infiltration and decreases exhaustion in a 3D tumor spheroid model. By repurposing Niclosamide, this work provides a feasible approach to enhance the efficacy of immune checkpoint blockade and guide future translational and clinical studies in immunotherapies against solid tumors.

Acute myeloid leukemia (AML), the most common hematologic malignancy, generally has a poor prognosis. Despite initial favorable responses to the BCL2 inhibitor venetoclax (VEN), remission is transient, and AML is eventually fatal. Resistance to VEN is primarily due to the overexpression of anti-apoptotic proteins, including MCL-1, BCL2L1 (BCL-XL), and BCL2A1. Casein kinase II (CK2) is a serine-threonine kinase and a known suppressor of apoptosis. We and others have reported that protein kinase CK2 activity is high in leukemic stem cells (LSCs) and associated with resistance to chemotherapy. We have shown that the selective CK2 inhibitor, CX-4945, suppresses BCL-XL and has a significant anti-tumor effect in AML preclinical models. CK2 expression and activity are high in venetoclax-resistant AML (VR-AML) cell lines. Genetic and pharmacological inhibition of CK2 significantly altered VR-AML gene signature, decreased MCL-1 protein level, increased BH3 priming and sensitized VR-AML cells to apoptosis. More importantly, CX-4945 selectively targeted LSCs (CD34+CD38-) and chemoresistant (CD123+CD47+) subpopulation in VR-AML. CX-4945 combined with VEN decreased leukemia burden and prolonged the survival of VR-AML cell line-derived and patient-derived xenografts compared to either drug alone. The combinatorial treatment was well tolerated in mice without additional myelosuppression or organ toxicity. CX-4945 (silmitasertib) is being tested in several early-phase clinical trials against adult and pediatric cancers. These preclinical results support the use of CX-4945 in combination with VEN to overcome resistance to apoptosis and re-sensitize VR-AML to chemotherapy. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/696284v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@6a902forg.highwire.dtl.DTLVardef@2028f5org.highwire.dtl.DTLVardef@160fd4dorg.highwire.dtl.DTLVardef@95da53_HPS_FORMAT_FIGEXP M_FIG C_FIG

The tumor microenvironment (TME) provides a niche for immune evasion and immunotherapy resistance, in part, by recruiting pro-tumor M2-like macrophages. In the present study, using heterospheroids consisting of cancer cells and macrophages, we identified TAM activators, which are compounds that reprogram M2-like tumor-associated macrophages (TAMs) toward the antitumor M1-like phenotype. THP-1- or human peripheral monocyte-derived macrophages were co-cultured with liver cancer cells in an ultra-low attachment dish to generate heterospheroids. Cell surface marker expression and macrophage infiltration into the heterospheroids were assessed by flow cytometry and fluorescence microscopy, respectively. Lipopolysaccharide (LPS) and interferon-{gamma} (IFN{gamma})-induced M1 marker expression was observed on the macrophages in the homospheroids; however, this induction was suppressed in heterospheroids. Microscopic imaging revealed that macrophage infiltration into the heterospheroids was decreased in the presence of LPS and IFN{gamma}, which prompted us to develop a high-content imaging screen. We identified two compounds [alprostadil (prostaglandin E1) and HX531] with TAM-activating activity. RNA-seq analysis revealed that HX531 modulated the immune and IFN response in cancer cells and cell division in macrophages. Moreover, alprostadil promoted the M1-like polarization of TAMs, increased tumor-infiltrating CD8+ T cells, and enhanced anti-PD-1 antibody therapeutic efficacy in a syngeneic mouse xenograft model. In conclusion, the heterospheroid culture recapitulates the immunosuppressive TME, which prevents the M1 polarization of TAMs. It provides a new platform for screening TAM activators and will enable the development of novel cancer immunotherapeutics when combined with high-content imaging analysis.

BackgroundDormant or slow cycling cells (SSCs) pre-exist in tumor and responsible for chemo-resistant and tumor recurrence. Due to their low differentiation and dormancy characteristics, SCCs are resistant to standard chemotherapy and targeted therapy. Label-retaining is a common method used to identify and isolate live SCCs. However, it remains unclear whether different label-retaining methods yield distinct SCC subpopulations. In this study, we investigated that various label-retaining methods result in overlapping yet heterogeneous subpopulations of SCCs. Additionally, we explored the molecular mechanisms regulating dormancy in triple-negative breast cancer (TNBC). MethodsWe employed multiple label-retaining methods to simultaneously label MDA-MB-231 cells, thereby generating distinct subpopulations of SCCs. We subsequently analyzed these subpopulations for heterogeneity in cell cycle distribution, drug resistance, invasive capacity, and other characteristics using real-time PCR, flow cytometry, and Transwell assays. RNA-seq analysis was performed to characterize the gene expression profiles of the SCCs. Furthermore, we used real-time PCR, Western blotting, immunofluorescence, and luciferase assays to investigate the role of characteristic AP-1 expression in dormancy regulation. Finally, the therapeutic effects of targeting AP-1 in the treatment of TNBC were assessed using a cell-derived xenograft model. ResultsWe labeled and separated three overlapping but non-identical SCCs subpopulations. We found that all three SCCs subgroups are cell cycle arrested. Additionally, Violet enriched SCCs showed stronger drug resistance and more G1 phase arrest, while Claret enriched SCCs demonstrated enhanced migratory and invasive abilities, along with more G2/M phase arrest. Furthermore, we observed upregulation of AP-1 expression in SCCs, and the JunB subunit of AP-1 promoted the expression of CDKN1A and GADD45A, thereby maintaining cell cycle arrest. CC-930 can inhibit AP-1 transcriptional activity by suppressing JNK activity, ultimately improving the therapeutic efficacy and prognosis of TNBC when used in combination with chemotherapy drugs. ConclusionsWe obtained three subpopulations of SCCs with heterogeneous drug resistance. Our findings suggest that AP-1 plays a regulatory role in dormancy regulation in TNBC, and elucidated the molecular function of JunB subunit. Targeting AP-1 with CC-930 has the potential to improve the treatment and prognosis of TNBC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/566980v2_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@129ce76org.highwire.dtl.DTLVardef@1b1cfa1org.highwire.dtl.DTLVardef@b68315org.highwire.dtl.DTLVardef@57faf1_HPS_FORMAT_FIGEXP M_FIG C_FIG TNBC harbors both fast-cycling cells (FCCs) and functionally overlapping slow-cycling cell (SCC) subpopulations that manifest differential drug sensitivities and motility (A) but are commonly regulated by the JunB-containing AP1 complex (B). (A). Slow-cycling (quiescent) TNBC cells in culture (a) identified by different label-retaining approaches phenotypically overlap (b), display differential drug sensitivities (c, d) and motility (e) but share common gene expression profiles (f). (B). Schematic depicting regulation of proliferation in FCCs by the c-Jun/c-Fos AP1 complex (left) and regulation of cellular dormancy in SCCs by c-Jun/JunB AP1 complex.

Cancer cells employ various mechanisms to evade immune surveillance. Their surface features, including a protective "sugar coat" and immune checkpoints like PD-L1 (programmed death ligand 1), can impede immune cell recognition. Sialic acids, which carry negative charges, may hinder cell contact through electrostatic repulsion, while PD-L1 transmits immunosuppressive signals to T cells. Furthermore, cancer cells manipulate macrophages within the tumor microenvironment to facilitate immune escape. Prior research has demonstrated the effectiveness of separately blocking the PD-L1 and sialic acid pathways in eliciting anti-tumor effects. In this study, we investigated the relationship between PD-L1 expression and genes associated with sialic acid in clinical databases. Subsequently, we developed a novel nanobody enzyme fusion protein termed Nb16-Sia to simultaneously target both PD-L1 and sialic acid pathways. In vivo experiments confirmed the anti-tumor activity of Nb16-Sia and highlighted its dependence on macrophages. Further investigations revealed that Nb16-Sia could polarize macrophages towards the M1 phenotype through the C-type lectin pathway in vitro and eliminate tumor-associated macrophages in vivo. In conclusion, our findings demonstrate that the fusion of PD-L1 nanobody with sialidase effectively targets tumor-associated macrophages, resulting in significant anti-tumor effects. This approach holds promise for drug development aimed at enhancing immune responses against cancer.

Competitive interactions between tumor cells and surrounding healthy cells are constantly present during the progression of a solid tumor, and their outcome has been proposed to affect the clinical behavior. Previous studies have described various mechanistic and molecular aspects that characterize this process, overall indicating that cancer cells behave as supercompetitors, which eliminate neighboring healthy cells to gain vital space for growth and infiltration of the tissue. Nevertheless, there is a lack of systematic characterization of these competitive interactions, particularly in the context of cancer in mammals. Furthermore, previous studies in the field of cell competition have primarily focused on homotypic cell competition, involving different clones of the same cell or cells deriving from the same tissue. Data are scarce regarding heterotypic cell competition between two unrelated cell types, which is particularly critical for the understanding of metastatic tumors. In this research, we study cell competition in the context of liver metastases, providing a broad characterization of this process in different relevant scenarios, including cells growing in vitro in 2D and 3D, and in vivo. Results show that in vitro, only a subset of cancer cell lines are coherently strong or moderate competitors against hepatocytes, while the remaining demonstrate poor competitiveness. The competitive proficiency can vary depending on the experimental growth system that is employed, and often predicts the phenotype of liver metastases in terms of aggressiveness and morphology. Finally, our data point towards an involvement of mechanical competition in determining the supercompetitor trait of cancer cells. Altogether, our research provides the first comprehensive characterization of heterotypic cell competition, and indicates that cancer cells possess heterogeneous competitive proficiency towards hepatocytes which can be affected by the growth conditions.

Background. Colorectal carcinomas (CRCs) are seldom eradicated by cytotoxic chemotherapy. Cancer cells with stem-like functional properties, often referred to as "cancer stem cells" (CSCs), display preferential resistance to several anti-tumor agents used in cancer chemotherapy, but the molecular mechanisms underpinning their selective survival remain only partially understood. Methods. In this study, we used Transcription Factor Target Genes (TFTG) enrichment analysis to identify transcriptional regulators (activators or repressors) that undergo preferential activation by chemotherapy in CRC cells with a "bottom-of-the-crypt" phenotype (EPCAM+/CD44+/CD166+; CSC-enriched) as compared to CRC cells with a "top-of-the-crypt" phenotype (EPCAM+/CD44neg/CD166neg; CSC-depleted). The two cell populations were purified in parallel by fluorescence-activated cell sorting (FACS) from a patient-derived xenograft (PDX) line representative of a moderately differentiated human CRC, following in vivo chemotherapy with irinotecan (CPT-11). The transcriptional regulators identified as differentially activated were tested for differential expression in normal vs. cancer tissues, and in cell populations enriched in stem/progenitor cell-types as compared to differentiated lineages (goblet cells, enterocytes) in the mouse colon epithelium. Finally, the top candidate was tested for mechanistic contribution to drug-resistance by selective down-regulation using short-hairpin RNAs (shRNAs). Results. Our analysis identified E2F4 and TFDP1, two core components of the DREAM transcriptional repression complex, as transcriptional modulators preferentially activated by irinotecan in EPCAM+/CD44+/CD166+ as compared to EPCAM+/CD44neg/CD166neg cancer cells. The expression levels of both genes (E2F4, TFDP1) were found up-regulated in CRCs as compared to human normal colon tissues, and in a sub-population of mouse colon epithelial cells enriched in stem/progenitor elements (Epcam+/Cd44+/Cd66alow/Kitneg) as compared to other sub-populations enriched in either goblet cells (Epcam+/Cd44+/Cd66alow/Kit+) or enterocytes (Epcam+/Cd44neg/Cd66ahigh). Most importantly, E2F4 down-regulation using shRNAs dramatically enhanced the sensitivity of human CRCs to in vivo treatment with irinotecan, across three independent PDX models. Conclusions. Our data identified E2F4 and the DREAM repressor complex as critical regulators of human CRC resistance to irinotecan, and as candidate targets for the development of chemo-sensitizing agents.

Studies on the dynamic changes occurring in the tumor microenvironment (TME) following CAR-T cell therapy have been confounded by host lymphodepletion, multiple dosing and immunodeficient models. Here, a nanobody-based, mouse mesothelin-targeting CAR-T cell (A101) was developed, achieving effective primary tumor suppression, metastasis reduction, and improved survival after a single dose in immunocompetent, syngeneic mouse models without lymphodepletion. Temporal tumor profiling using RNA sequencing revealed initial downregulation of cell proliferation genes followed by upregulation of inflammation, epithelial-to-mesenchymal-transition (EMT) and extracellular matrix (ECM) modification genes in the CAR-T-treated tumors relative to mock-T-treated controls. This phenotype was reversed at a later timepoint which coincided with downregulation of immunosuppressive Cd274+ Lcn2+ neutrophils and upregulation of anti-tumor P2rx1+ Nrf2- neutrophils. At the same time, upregulation of Ccl2+ in fibroblasts and a more immunomodulatory macrophage phenotype was observed in CAR-T-treated tumors, indicating a tumor adaptation mechanism. This study demonstrates complex dynamic changes in the TME, and highlights time-dependent responses of solid tumors to CAR-T cell therapy. It further highlights Lcn2+ neutrophils and Ccl2+ fibroblasts as potential therapeutic targets for improving CAR-T cell anti-tumor efficacy. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/640438v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@88ec4org.highwire.dtl.DTLVardef@1d4fa64org.highwire.dtl.DTLVardef@182e11aorg.highwire.dtl.DTLVardef@1889182_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract.C_FLOATNO Tumor responses to A101 CAR-T cell treatment. C_FIG

CD19-targeting chimeric antigen receptor T cells (CART19) have demonstrated significant effectiveness in treating relapsed or refractory large B-cell lymphoma (LBCL). However, they often fail to sustain durable remissions in more than half of all treated patients. Therefore, there is an urgent need to identify approaches to enhance CART19 efficacy. Here, we studied the impact of low-dose radiation on CART19 activity in vitro and find that radiation enhances the cytotoxicity of CART19 against LBCL by upregulating death receptors. Disrupting the FAS receptor diminishes this benefit, indicating that this pathway plays an important role in enhancing the cytotoxic effects of CAR T cells. To further validate these findings, we conducted in vivo studies using a lymphoma syngeneic mouse model delivering total body irradiation (TBI). We observed that delivering TBI at a single dose of 1Gy prior to CAR T cell infusion significantly improved CART19-mediated tumor elimination and increased overall survival rates. Importantly, we characterized several important effects of TBI, including enhanced lymphodepletion, improved T cell expansion and persistence, better intra-tumoral migration, and a more favorable, anti-tumor phenotypic composition of the T cells. In summary, for the first time, we have demonstrated preclinically that administering TBI before CART19 infusion significantly accelerates tumor elimination and improves overall survival. This approach holds promise for translation into clinical practice and serves as a valuable foundation for further research to enhance outcomes for patients receiving CART19 treatment.

Gliomas are the most prevalent type of brain tumors and one of the leading causes of cancer-related death in the adolescent and young adult population (AYA). Two-thirds of glioma AYA patients are affected by low-grade gliomas (LGGs), but there are no specific treatments. Therefore, a percentage of LGG patients experience tumor relapse and malignant progression to high-grade glioma which leads to fatal outcomes. In part, malignant progression is potentiated by the immunosuppressive stromal component of the tumor microenvironment (TME) underscored by M2-macrophages and a paucity of cytotoxic T cells. As a result, first-line immunotherapies have failed to improve outcomes for patients with progressive high-grade gliomas. Here, we report the efficacy of an in vivo approach that demonstrates the potential for a novel cell-mediated innate immunotherapy designed to abrogate immunosuppressive mechanisms within the glioma TME and enhance the recruitment of activated effector T cells. A single dose of engineered bone marrow-derived myeloid cells that release Interleukin-2 (GEMys-IL2) was used systemically to treat mice with LGG tumors systemically. Our results demonstrate that GEMys-IL2 efficiently crossed the blood brain barrier (BBB), infiltrated the glioma microenvironment, and reprogrammed the infiltrating immune cell composition and transcriptome. In addition, GEMys-IL2 impaired tumor progression and extended survival in a LGG immunocompetent mouse model. In conclusion, we demonstrated that GEMys-IL2 have a therapeutic effect in vivo, thus supporting its potential application as a novel immunotherapy that warrants further investigation.