Abstract Background: Gallbladder carcinoma (GBC) is a highly aggressive malignancy with poor prognosis and limited therapeutic options. Enhancers and super-enhancers (SEs) are critical regulators of cell type-specific transcription and oncogenic programs, yet their roles in GBC progression remain poorly defined. Objective: We aimed to map enhancer and SE reprogramming in GBC and identify master transcription factors (TFs) driving these transcriptional programs. Design: Chromatin immunoprecipitation sequencing and RNA sequencing were performed on normal, inflammatory, and tumorous gallbladder tissues, as well as GBC cell lines. Integrative analyses of enhancer remodeling, TF motif enrichment, expression, and transcriptional connectivity were conducted to identify SE-driven master TFs. Functional assays and immunohistochemistry were used to evaluate their oncogenic and immunomodulatory functions. Results: GBC exhibited extensive enhancer and SE reprogramming relative to non-tumorous gallbladder tissues, with gained enhancers and SEs preferentially enriched in oncogenic pathways. ETS1, RUNX1, and FOSL1 were identified as SE-driven master TFs that form an interconnected regulatory circuitry co-occupying SEs, including those of CD274 (encoding PD-L1), to promote oncogenic transcription and immune evasion. Perturbation of this circuitry suppressed GBC cell proliferation, migration, and tumor growth in vitro and in vivo. Clinically, elevated expression of these master TFs correlated with reduced CD8+ T cell infiltration, poorer patient survival, and diminished responsiveness to immunotherapy in GBC. Conclusion: This study delineates enhancer and SE reprogramming during gallbladder malignant transformation, identifies an ETS1-RUNX1-FOSL1 master TF circuitry, and highlights FOSL1 as a key driver of oncogenic transcription and immune evasion, providing mechanistic, prognostic, and therapeutic insights into GBC. Citation Format: Jiaxi Sun, Xing He, Yuntan Qiu, Zhenyu Zhou, Daning Lu, Shiru Tang, Wenbin Li, Dong Yin, Lehang Lin. Enhancer reprogramming establishes ETS1-RUNX1-FOSL1 as an oncogenic and immunosuppressive transcriptional circuitry in gallbladder carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7256.

Osteosarcoma is a primary malignant bone tumour with an unsatisfactory prognosis, and individualised and comprehensive treatment is needed. HP1 (α/β/γ) is an important heterochromatin protein involved in transcriptional regulation and is also involved in the DNA damage response (DDR). However, little is known about the participation of HP1 in DNA damage-induced transcriptional repression. In this study, HP1 proteins were shown to be involved in DNA damage-mediated transcriptional repression at the very onset of DNA damage. Mechanistically, HP1 proteins were recruited to DNA damage sites by interacting with and being covalently PARylated by PARP1. This process increased H2AK119Ub, which ultimately led to the inactivation of RNA Pol II to achieve transcriptional suppression. Silencing HP1 led to a weakening of PARP1 recruitment and homologous recombination (HR) repair. Concurrently, HP1γ (CBX3) knockdown resulted in an increased the sensitivity of osteosarcoma cells to radiotherapy, chemotherapy and PARP1 inhibitors. The results of the study demonstrated the involvement of HP1 in the DDR via covalent PARylation by PARP1, resulting in the suppression of transcription and the promotion of HR repair. Overall, these results identify a new molecular mechanism of DNA damage-induced transcriptional repression and provide a theoretical basis for the potential application of DNA damage-induced transcriptional repression in the treatment of osteosarcoma.

Tumorigenesis is a complex biological process, accompanied by cellular dedifferentiation and metabolic reprogramming, which similarities to the metabolic characteristics of embryonic development stages. In our research, we focused particularly on the RNA-binding protein PEG10, which is highly expressed in the placenta and found to be similarly overexpressed in liver cancer cells, playing a key role in the process of aerobic glycolysis in tumor cells. This discovery suggests that there may be a phenomenon of fetal-like metabolic reprogramming in hepatocellular carcinoma (HCC), which is of significant importance for understanding the pathogenesis of HCC and for seeking new therapeutic strategies. In hepatocellular carcinoma (HCC) cells, we found that PEG10 enhances the stability of mRNA for key glycolytic genes hexokinase2 (HK2) and Glucose transporter 1 (GLUT1) by inhibiting the STAU1-mediated RNA degradation pathway, thereby promoting aerobic glycolysis in tumor cells. This process not only promotes the proliferation of tumor cells but also reduces the sensitivity of tumor cells to sorafenib. Furthermore, we observed in clinical samples that high expression of PEG10 is closely associated with poor prognosis in HCC patients, further confirming the important role of PEG10 in the development of HCC. Our research also found that retinoic acid can effectively inhibit aerobic glycolysis in tumor cells by suppressing the transcriptional expression of PEG10, thereby inhibiting the growth of tumor cells. In animal models, mice with liver-specific PEG10 gene knockout showed significant resistance to oncogene-induced liver cancer occurrence and development, providing strong evidence for PEG10 as a therapeutic target. These findings not only reveal the biological link between PEG10 and onco-fetal metabolic reprogramming at the molecular level but also indicate from a clinical perspective that PEG10 may be a potential biomarker and therapeutic target for HCC. The high expression of PEG10 is associated with poor prognosis in HCC patients, and the inhibitory effect of retinoic acid on PEG10 expression provides a new strategy for the treatment of HCC. These results provide new ideas for the future diagnosis and treatment of HCC, especially in the development of targeted therapeutic drugs against PEG10, which has important application prospects. Our research has laid a solid foundation for a deeper understanding of the metabolic reprogramming mechanisms of HCC and the development of new therapeutic methods. Dong Yin, Xinyi Yao, Jingyuan Zhang, Yin Zhang, Jianyou Liao, Kaishun Hu, Jiehua He, Daning Lu. Placental gene PEG10 promotes onco-fetal metabolic reprogramming in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5399.

RNA-binding proteins (RBPs) play key roles in a wide range of physiological and pathological processes. To facilitate the investigation of RBP functions and disease associations, we updated the EuRBPDB and renamed it as RBPWorld (http://research.gzsys.org.cn/rbpworld/#/home). Leveraging 998 RNA-binding domains (RBDs) and 87 RNA-binding Proteome (RBPome) datasets, we successfully identified 1 393 413 RBPs from 445 species, including 3030 human RBPs (hRBPs). RBPWorld includes primary RNA targets of diverse hRBPs, as well as potential downstream regulatory pathways and alternative splicing patterns governed by various hRBPs. These insights were derived from analyses of 1515 crosslinking immunoprecipitation-seq datasets and 616 RNA-seq datasets from cells with hRBP gene knockdown or knockout. Furthermore, we systematically identified 929 RBPs with multi-functions, including acting as metabolic enzymes and transcription factors. RBPWorld includes 838 disease-associated hRBPs and 970 hRBPs that interact with 12 disease-causing RNA viruses. This provision allows users to explore the regulatory roles of hRBPs within the context of diseases. Finally, we developed an intuitive interface for RBPWorld, facilitating users easily access all the included data. We believe that RBPWorld will be a valuable resource in advancing our understanding of the biological roles of RBPs across different species.

Hyperactivation of ribosome biogenesis (RiBi) drives cancer progression, yet the role of RiBi-associated proteins (RiBPs) in breast cancer (BC) is underexplored. In this study, we perform a comprehensive multi-omics analysis and reveal that assembly and maturation factors (AMFs), a subclass of RiBPs, are upregulated at both RNA and protein levels in BC, correlating with poor patient outcomes. In contrast, ribosomal proteins (RPs) do not show systematic upregulation across various cancers, including BC. We further demonstrate that the oncogenic activation of a top AMF candidate in BC, DCAF13, enhances Pol I transcription and promotes proliferation in BC cells both in vitro and in vivo. Mechanistically, DCAF13 promotes Pol I transcription activity by facilitating the K63-linked ubiquitination of RPA194. This process stimulates global protein synthesis and cell growth. Our findings uncover a modification of RPA194 that regulates Pol I activity; this modification is dysregulated in BC, contributing to cancer progression.

Perturb-Seq combines CRISPR (clustered regularly interspaced short palindromic repeats)-based genetic screens with single-cell RNA sequencing readouts for high-content phenotypic screens. Despite the rapid accumulation of Perturb-Seq datasets, there remains a lack of a user-friendly platform for their efficient reuse. Here, we developed PerturbDB (http://research.gzsys.org.cn/perturbdb), a platform to help users unveil gene functions using Perturb-Seq datasets. PerturbDB hosts 66 Perturb-Seq datasets, which encompass 4 518 521 single-cell transcriptomes derived from the knockdown of 10 194 genes across 19 different cell lines. All datasets were uniformly processed using the Mixscape algorithm. Genes were clustered by their perturbed transcriptomic phenotypes derived from Perturb-Seq data, resulting in 421 gene clusters, 157 of which were stable across different cellular contexts. Through integrating chemically perturbed transcriptomes with Perturb-Seq data, we identified 552 potential inhibitors targeting 1409 genes, including an mammalian target of rapamycin (mTOR) signaling inhibitor, retinol, which was experimentally verified. Moreover, we developed a ‘Cancer’ module to facilitate the understanding of the regulatory role of genes in cancer using Perturb-Seq data. An interactive web interface has also been developed, enabling users to visualize, analyze and download all the comprehensive datasets available in PerturbDB. PerturbDB will greatly drive gene functional studies and enhance our understanding of the regulatory roles of genes in diseases such as cancer.

Figures S1-S12;Tables S1-S4

Transcriptional dysregulation of genes is a hallmark of tumors and can serve as targets for cancer drug development. However, it is extremely challenging to develop small-molecule inhibitors to target abnormally expressed transcription factors (TFs) except for the nuclear receptor family of TFs. Little is known about the interaction between TFs and transcription cofactors in gastroesophageal adenocarcinoma (GEA) or the therapeutic effects of targeting TF and transcription cofactor complexes. In this study, we found that ETS homologous factor (EHF) expression is promoted by a core transcriptional regulatory circuitry (CRC), specifically ELF3-KLF5-GATA6, and interference with its expression suppressed the malignant biological behavior of GEA cells. Importantly, we identified Ajuba LIM protein (AJUBA) as a new coactivator of EHF that cooperatively orchestrates transcriptional network activity in GEA. Furthermore, we identified KRAS signaling as a common pathway downstream of EHF and AJUBA. Applicably, dual targeting of EHF and AJUBA by lipid nanoparticles cooperatively attenuated the malignant biological behaviors of GEA in vitro and in vivo. In conclusion, EHF is upregulated by the CRC and promotes GEA malignancy by interacting with AJUBA through the KRAS pathway. Targeting of both EHF and its coactivator AJUBA through lipid nanoparticles is a novel potential therapeutic strategy.

Cysteine-rich angiogenic inducer 61 (CYR61), also called CCN1, has long been characterized as a secretory protein. Nevertheless, the intracellular function of CYR61 remains unclear. Here, we found that CYR61 is important for proper cell cycle progression. Specifically, CYR61 interacts with microtubules and promotes microtubule polymerization to ensure mitotic entry. Moreover, CYR61 interacts with PLK1 and accumulates during the mitotic process, followed by degradation as mitosis concludes. The proteolysis of CYR61 requires the PLK1 kinase activity, which directly phosphorylates two conserved motifs on CYR61, enhancing its interaction with the SCF E3 complex subunit FBW7 and mediating its degradation by the proteasome. Mutations of phosphorylation sites of Ser167 and Ser188 greatly increase CYR61's stability, while deletion of CYR61 extends prophase and metaphase and delays anaphase onset. In summary, our findings highlight the precise control of the intracellular CYR61 by the PLK1-FBW7 pathway, accentuating its significance as a microtubule-associated protein during mitotic progression.

The Warburg effect is a hallmark of cancer that refers to the preference of cancer cells to metabolize glucose anaerobically rather than aerobically1,2. This results in substantial accumulation of lacate, the end product of anaerobic glycolysis, in cancer cells3. However, how cancer metabolism affects chemotherapy response and DNA repair in general remains incompletely understood. Here we report that lactate-driven lactylation of NBS1 promotes homologous recombination (HR)-mediated DNA repair. Lactylation of NBS1 at lysine 388 (K388) is essential for MRE11-RAD50-NBS1 (MRN) complex formation and the accumulation of HR repair proteins at the sites of DNA double-strand breaks. Furthermore, we identify TIP60 as the NBS1 lysine lactyltransferase and the 'writer' of NBS1 K388 lactylation, and HDAC3 as the NBS1 de-lactylase. High levels of NBS1 K388 lactylation predict poor patient outcome of neoadjuvant chemotherapy, and lactate reduction using either genetic depletion of lactate dehydrogenase A (LDHA) or stiripentol, a lactate dehydrogenase A inhibitor used clinically for anti-epileptic treatment, inhibited NBS1 K388 lactylation, decreased DNA repair efficacy and overcame resistance to chemotherapy. In summary, our work identifies NBS1 lactylation as a critical mechanism for genome stability that contributes to chemotherapy resistance and identifies inhibition of lactate production as a promising therapeutic cancer strategy.

Abstract Perturb-seq is a high-throughput technique that combines clustered regularly interspaced short palindromic repeats (CRISPR)-based screens with single-cell RNA sequencing (scRNA-seq) readouts for high-content phenotypic screens to comprehensively map the transcriptional effects of genetic perturbations, showing great advantages in revealing disease-associated gene functions and mechanisms in high volumes. Despite the rapid accumulation of Perturb-seq datasets, no dedicated database exists for reusing these valuable information. In this study, we developed a platform called PerturbDB (http://research.gzsys.org.cn/perturbdb) to facilitate users to unveil genotype-phenotype relations, especially gene functions and regulatory networks involved in several classical cancer associated phenotypes using 37 Perturb-seq datasets from 15 studies. By reanalyzing 3,429,829 single-cell transcriptomes from the knockdown of 3214 genes across 10 different cell lines, we identified 749 classical cancer phenotype-related genes and 373 functional gene clusters annotating potential novel functions. Utilizing Marker genes scoring and the InferCNV algorithm, we identified genes involved in 9 malignant phenotypes, which consists of sustaining proliferative signaling (362 genes), resisting cell death (120 genes), inducing angiogenesis (145 genes), tissue invasion and metastasis (321 genes), enabling replicative immortality (160 genes), deregulating cellular metabolism (247 genes), avoiding immune destruction (95 genes), unlocking phenotypic plasticity (231 genes), and chromosome instability (231 genes). Additionally, functional clusters were calculated utilizing Principal Component Analysis (PCAs) and the HDBSCAN package to introduce unknown gene functions related to the cancer associated phenotypes. Perturbation clusters (PCs) were identified by comparing similarities in the transcriptomes of perturbed cells, suggesting individual genes in the same functional cluster perform similar gene functions, and therefore novel functions of 735 genes can be inferred from the known functions of neighboring genes. The PGSEA tool was developed to facilitate functional analysis of genes not yet included, which helps users to predict gene functions through a combination of PerturbDB datasets and personalized RNA-seq datasets. This study will greatly expand our understanding of genes involved in emblematic cancer associated phenotypes and their coordinated functions and regulatory networks. Citation Format: Bing Yang, Man Zhang, Yanmei Shi, Yi-Ming Dong, Xingyu Ma, Jingyuan Zhang, Daning Lu, Jian-You Liao, Dong Yin. PerturbDB: A resource for revealing gene functions and cancer-associated phenotypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3550.

Drug-tolerant persister (DTP) cancer cells drive residual tumor and relapse. However, the mechanisms underlying DTP state development are largely unexplored. In a recent study, we determined that PINK1-mediated mitophagy favors DTP generation in the context of MAPK inhibition therapy. DTP cells that persist in the presence of a MAPK inhibitor exhibit mitochondriadependent metabolism. During DTP state development, MYC depletion alleviates the transcriptional repression of PINK1, resulting in PINK1 upregulation and mitophagy activation. PINK1-mediated mitophagy is essential for mitochondrial homeostasis in DTP cells. Either knockdown of PINK1 or inhibition of mitophagy eradicates DTP cells and achieves complete responses to MAPK inhibition therapy. This study reveals a novel role of mitophagy as a protective mechanism for DTP development.

Abstract The drug-tolerant persister (DTP) state enables cancer cells to evade cytotoxic stress from anticancer therapy. However, the mechanisms governing DTP generation remain poorly understood. Here, we observed that lung adenocarcinoma (LUAD) cells and organoids entered a quiescent DTP state to survive MAPK inhibitor treatment. DTP cells following MAPK inhibition underwent a metabolic switch from glycolysis to oxidative phosphorylation (OXPHOS). PTEN-induced kinase 1 (PINK1), a serine/threonine kinase that initiates mitophagy, was upregulated to maintain mitochondrial homeostasis during DTP generation. PINK1-mediated mitophagy supported DTP cell survival and contributed to poor prognosis. Mechanistically, MAPK pathway inhibition resulted in MYC-dependent transcriptional upregulation of PINK1, leading to mitophagy activation. Mitophagy inhibition using either clinically applicable chloroquine or depletion of PINK1 eradicated drug tolerance and allowed complete response to MAPK inhibitors. This study uncovers PINK1-mediated mitophagy as a novel tumor protective mechanism for DTP generation, providing a therapeutic opportunity to eradicate DTP and achieve complete responses. Significance: DTP cancer cells that cause relapse after anticancer therapy critically depend on PINK1-mediated mitophagy and metabolic reprogramming, providing a therapeutic opportunity to eradicate persister cells to prolong treatment efficacy.

MEX3A is an RNA-binding protein that mediates mRNA decay through binding to 30 untranslated regions. However, its role and mechanism in clear cell renal cell carcinoma remain unknown. In this study, we found that MEX3A expression was transcriptionally activated by ETS1 and upregulated in clear cell renal cell carcinoma. Silencing MEX3A markedly reduced clear cell renal cell carcinoma cell proliferation in vitro and in vivo. Inhibiting MEX3A induced G1/S cell-cycle arrest. Gene set enrichment analysis revealed that E2F targets are the central downstream pathways of MEX3A. To identify MEX3A targets, systematic screening using enhanced cross-linking and immunoprecipitation sequencing, and RNA-immunoprecipitation sequencing assays were performed. A network of 4,000 genes was identified as potential targets of MEX3A. Gene ontology analysis of upregulation of the cell proliferation pathway was highly enriched. Further assays indicated that MEX3A bound to the CDKN2B 30 untranslated region, promoting its mRNA degradation. This leads to decreased levels of CDKN2B and an uncontrolled cell cycle in clear cell renal cell carcinoma, which was confirmed by rescue experiments. Our findings carcinoma.

Background The main cause of death in colorectal cancer patients is metastasis. Accumulating evidences suggest that circRNA plays pivotal roles in cancer initiation and development. However, the underlying molecular mechanisms of circRNAs that orchestrate cancer metastasis remain vague and need further clarification. Methods Two paired CRC and adjacent normal tissues were used to screen the upregulated circRNAs by circRNA-seq; then, cell invasion assay was applied to confirm the functional invasion-related circRNAs. According to the above methods, circHERC4 (hsa_circ_0007113) was selected for further research. Next, we investigated the clinical significance of circHERC4 in a large cohort of patients with CRC. The oncogenic activity of circHERC4 was investigated in both CRC cell lines and animal xenograft studies. Finally, we explored the molecular mechanisms underlying circHERC4 as a malignant driver. Results We demonstrated that circHERC4 was aberrantly elevated in CRC tissues (P < 0.001), and was positively associated with lymph node metastasis and advanced tumor grade (P < 0.01). Notably, the expression of circHERC4 was associated with worse survival in patients with CRC. Silencing of circHERC4 significantly inhibited the proliferation and migration of two highly aggressive CRC cell lines and reduced liver and lung metastasis in vivo. Mechanistically, we revealed that circHERC4 inactivated the tumor suppressor, miR-556-5p, leading to the activation of CTBP2/E-cadherin pathway which promotes tumor metastasis in CRC. Conclusions CircHERC4 exerts critical roles in promoting tumor aggressiveness through miR-556-5p/CTBP2/E-cadherin pathway and is a prognostic biomarker of the disease, suggesting that circHERC4 may serve as an exploitable therapeutic target for patients with CRC.

Background Long noncoding RNAs (lncRNAs) play important roles in many physiological and pathological processes, this indicates that lncRNAs can serve as potential targets for gene therapy. Stable expression is a fundamental technology in the study of lncRNAs. The lentivirus is one of the most widely used delivery systems for stable expression. However, it was initially designed for mRNAs, and the applicability of lentiviral vectors for lncRNAs is largely unknown. Results We found that the lentiviral vector produces lncRNAs with improper termination, appending an extra fragment of ~ 2 kb to the 3ʹ-end. Consequently, the secondary structures were changed, the RNA–protein interactions were blocked, and the functions were impaired in certain lncRNAs, which indicated that lentiviral vectors are not ideal delivery systems of lncRNAs. Here, we developed a novel lncRNA delivery method called the Expression of LncRNAs with Endogenous Characteristics using the Transposon System (ELECTS). By inserting a termination signal after the lncRNA sequence, ELECTS produces transcripts without 3ʹ-flanking sequences and retains the native features and function of lncRNAs, which cannot be achieved by lentiviral vectors. Moreover, ELECTS presents no potential risk of infection for the operators and it takes much less time. ELECTS provides a reliable, convenient, safe, and efficient delivery method for stable expression of lncRNAs. Conclusions Our study demonstrated that improper transcriptional termination from lentiviral vectors have fundamental effects on molecular action and cellular function of lncRNAs. The ELECTS system developed in this study will provide a convenient and reliable method for the lncRNA study. Graphic Abstract

Abstract To reconstruct systematically hyperactive transcription factor (TF)-dependent transcription networks in squamous cell carcinomas (SCCs), a computational method (ELMER) was applied to 1293 pan-SCC patient samples, and 44 hyperactive SCC TFs were identified. As a top candidate, DLX5 exhibits a notable bifurcate re-configuration of its bivalent promoter in cancer. Specifically, DLX5 maintains a bivalent state in normal tissues; its promoter is hypermethylation, leading to DLX5 transcriptional silencing in esophageal adenocarcinoma (EAC). In stark contrast, DLX5 promoter gains active histone marks and becomes transcriptionally activated in ESCC, which is directly mediated by SOX2. Functionally, silencing of DLX5 substantially inhibits SCC viability both in vitro and in vivo. Mechanistically, DLX5 cooperates with TP63 in regulating ∼2000 enhancers and promoters, which converge on activating cancer-promoting pathways. Together, our data establish a novel and strong SCC-promoting factor and elucidate a new epigenomic mechanism - bifurcate chromatin re-configuration - during cancer development.

CCAAT/enhancer binding proteins (CEBPs, including CEBPA, CEBPB, CEBPD, CEBPE, CEBPG, and CEBPZ) play critical roles in a variety of physiological and pathological processes. However, the molecular characteristics and biological significance of CEBPs in esophageal squamous cell carcinoma (ESCC) have rarely been reported. Here, we show that most of the CEBPs are upregulated and accompanied with copy number amplifications in ESCC. Of note, high CEBPG expression is regulated by the ESCC specific transcription factor TP63 and serves as a prognostic factor for poor survival in ESCC patients. Functionally, CEBPG significantly promotes the proliferation and migration of ESCC cells both in vitro and in vivo. Mechanistically, CEBPG activates the PI3K-AKT signaling pathway through directly binding to distal enhancers and/or promoters of genes involved in this pathway, including genes of CCND1, MYC, CDK2, etc. These findings provide new insights into CEBPs dysregulation in ESCC and elucidate a crucial role for CEBPG in the progression of ESCC, highlighting its potential therapeutic value for ESCC treatment.

Abstract Chemotherapy is applied in over 70% of breast cancer patients. Antimicrotubule drugs and DNA-damaging drugs are the most popular medicine used for chemotherapy. However, it still lack of predictor for indicating which chemotherapy drug will benefit to patients. An urgent need is to develop biomarker used to determine which chemotherapy will work for individual patient. Antimicrotubule drugs such as docetaxel and vinorelbine are prescribed widely for breast cancer, nevertheless, about one-third of breast cancer patients suffer from the side effects of anti-microtubule drugs chemotherapy without benefit from it. Here, we report that PARK2 is a potential biomarker for chemosensitivity to antimicrotubule drugs in breast cancer. PARK2 gene encodes an E3 ubiquitin ligase. 34% of breast cancer patients exhibited PARK2 deletion. Interestingly, high PARK2 expression was positively correlated with favorable survival in breast cancer patients receiving chemotherapy, but not in those not receiving chemotherapy. Moreover, PARK2 overexpression specifically rendered cells more sensitive to antimicrotubule drugs, but not to DNA-damaging drugs. Depletion of PARK2 augmented resistance to antimicrotubule drugs. Mechanistically, PARK2 markedly activated the mitochondrial pathway of apoptosis after exposure to antimicrotubule drugs. This occurred through downregulating the antiapoptotic protein BCL-2. Notably, PARK2 physically interacted with BCL-2 and promoted ubiquitination of BCL-2 in an E3 ligase-dependent manner. Hence, PARK2 significantly enhanced the chemosensitivity of antimicrotubule drugs both in vitro and in vivo, while loss-of-function PARK2 mutants failed to enhance the sensitivity of antimicrotubule drugs. Taken together, we identified PARK2 as a novel mediator of antimicrotubule drug which provides a predictor for the chemosensitivity of antimicrotubule drugs in breast cancer. Citation Format: Hengxing Chen, Yun Li, Yu Li, Zhen Chen, Limin Xie, Wenjia Li, Yuanxin Zhu, Daning Lu, Xue Hong, H. Phillip Koeffler, Wenjing Wu, Kaishun Hu, Dong Yin. PARK2 enhances chemosensitivity of antimicrotubule drugs in breast cancer via promoting degradation of BCL-2 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 72.

IntroductionThe molecular events that lead to irreversible myocardial damage during severe ischemia remain poorly understood. Changes in cytosolic redox status and ability of mitochondria to oxidatively metabolize fatty acids and carbohydrates have been implicated in ischemic Injury. The pentose phosphate pathway (PPP) produces NADPH, which can be used to maintain glutathione in its reduced state, providing protection against oxidative damage. The rate of glycolysis during ischemia determines extent of ischemic injury. We investigated flux of glucose through PPP and glycolysis in mouse hearts subjected to low‐flow ischemia in this study.MethodsIsolated mouse hearts were perfused in Langendorff mode with 10mM [1,2‐13C2]‐glucose for 60min, followed by 90min low‐flow ischemia (perfused at 10% of baseline flow rate). The cardiac function was recorded with PowerLab Data Acquisition Systems. Lipid peroxidation was determined with Colorimetric/Fluorometric Assay Kit. The flux of glucose through the PPP and glycolysis was assessed by the contribution of the doublet (D23, [2,3‐13C2]‐lactate) and singlet (S3, [3‐13C]‐lactate) to the total 13C‐NMR signal of lactate C3 in effluent, respectively.Results90min low‐flow ischemia resulted in both systolic dysfunction (as indicated by decreased left ventricular systolic pressure, rate of tension development and developed pressure) and diastolic dysfunction (as indicated by increased end diastolic pressure and decreased rate of relaxation) accompanied with increased lipid peroxidation. Furthermore, the flux of glucose through PPP increased substantially and correlatively with that through glycolysis.Conclusion[1,2‐13C2]‐glucose can be used to simultaneously assess flux of glucose through PPP and glycolysis. The flux of glucose through both PPP and glycolysis increased during myocardial low‐flow ischemia.Support or Funding InformationThis study was supported by Department Fund.