Abstract 3964: APE1 protects SMAD3 against ROC1 ubiquitin mediated degradation in esophageal adenocarcinoma cells

Abstract Background: The incidence of esophageal adenocarcinoma (EAC) has increased more than six-fold over the past three decades and continues to rise in the Western world. The 5-year survival rate for EAC patients is less than 20% which underscores the need to better understand the underlying mechanisms to identify new therapeutic approaches. This study aimed at investigating the potential role of APE1 in regulating SMAD3 and promoting EAC progression. Methods and Results: Western blot data showed that APE1 and SMAD3 were highly expressed in EAC cell lines. APE1 silencing reduced SMAD3 nuclear expression and downregulated its downstream targets SERPINE1 and c-myc. These results were confirmed by immunofluorescence staining showing loss of nuclear accumulation of SMAD3 after APE1 knockdown. Mechanistically, immunoprecipitation and proximity ligation assays revealed a direct binding between APE1 and SMAD3 in the nucleus. Further investigation showed that APE1 binds to the C-terminal MH2 domain of SMAD3, and this binding protects SMAD3 from ubiquitin mediated proteasomal degradation by blocking its interaction with the RING finger protein, ROC1. Interestingly, APE1-redox-specific inhibition (APX2009) downregulated SMAD3 expression and the APE1 redox-deficient mutant (C65A) disrupted APE1-SMAD3 binding indicating that this regulation depends on APE1 redox activity. Conclusion: Our findings establish a role of APE1 in regulating SMAD3 in EAC. These findings provide a potential therapeutic approach for the treatment of EAC by the pharmacological inhibition of APE1. Citation Format: Farah Ballout, Heng Lu, Dunfa Peng, Wael El-Rifai. APE1 protects SMAD3 against ROC1 ubiquitin mediated degradation in esophageal adenocarcinoma cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3964

Differential Expression of NEK Kinase Family Members in Esophageal Adenocarcinoma and Barrett’s Esophagus

The incidence of esophageal adenocarcinoma (EAC) has risen rapidly during the past four decades, making it the most common type of esophageal cancer in the USA and Western countries. The NEK (Never in mitosis A (NIMA) related kinase) gene family is a group of serine/threonine kinases with 11 members. Aberrant expression of NEKs has been recently found in a variety of human cancers and plays important roles in tumorigenesis, progression, and drug-resistance. However, the expression of the NEKs in EAC and its precancerous condition (Barrett’s esophagus, BE) has not been investigated. In the present study, we first analyzed the TCGA and 9 GEO databases (a total of 10 databases in which 8 contain EAC and 6 contain BE) using bioinformatic approaches for NEKs expression in EAC and BE. We identified that several NEK members, such as NEK2 (7/8), NEK3 (6/8), and NEK6 (6/8), were significantly upregulated in EAC as compared to normal esophagus samples. Alternatively, NEK1 was downregulated in EAC as compared to the normal esophagus. On the contrary, genomic alterations of these NEKs are not frequent in EAC. We validated the above findings using qRT-PCR and the protein expression of NEKs in EAC cell lines using Western blotting and in primary EAC tissues using immunohistochemistry and immunofluorescence. Our data suggest that frequent upregulation of NEK2, NEK3, and NEK7 may be important in EAC

Abstract 4776: NRF2 is overexpressed in esophageal adenocarcinoma and its targeting sensitizes tumor cells to cisplatin through induction of ferroptosis and apoptosis

Abstract Background: Esophageal adenocarcinoma (EAC) is the predominant type of esophageal cancer in the United States, with the 5-year survival rate is below 20%. EAC develops through Barrett’s esophagus (BE)-dysplasia-carcinoma cascade. Gastroesophageal reflux disease (GERD), where acidic bile salts refluxate into the esophagus, is the main risk factor for the development of BE and its progression to EAC. The NFE2-related factor 2 (NRF2) is the master cellular antioxidant regulator, involving in many cancer hallmarks. Methods and Results: Using western blotting and immunohistochemistry technologies, we detected high NRF2 protein levels in EAC cell lines and primary EAC tissues, as compared with normal esophagus and non-neoplastic Barrett’s esophagus samples. The knockdown of NRF2 using NRF2 specific siRNAs significantly increased oxidative stress in response to cellular stress stimuli by bile salts or cisplatin. This was associated with an increase in DNA damage and inhibition of EAC cell growth. Brusatol, a NRF2 inhibitor, significantly inhibited NRF2 transcriptional activity and downregulated NRF2 target genes. We discovered that in addition to inducing apoptosis, Brusatol alone or in combination with CDDP induced significant lipid peroxidation and ferroptosis as evidenced by reduced xCT and GPX4 expression, two known ferroptosis markers. Moreover, the combination of Brusatol and CDDP significantly inhibited EAC tumor xenografts growth in vivo. We confirmed the in vitro data showing ferroptosis as an important mechanism in the xenografted tumors treated with Brusatol or Brusatol and CDDP combination using IHC staining. Conclusion: Our data support the role of NRF2 in protecting against stress-induced apoptosis and ferroptosis in EACs. Targeting NRF2 in combination with platinum therapy can be an effective strategy for eliminating cancer cells in EAC. Citation Format: Farah Ballout, Heng Lu, Zheng Chen, Tianling Hu, Lei Chen, Wael El-Rifai, Dunfa Peng. NRF2 is overexpressed in esophageal adenocarcinoma and its targeting sensitizes tumor cells to cisplatin through induction of ferroptosis and apoptosis. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4776

Genome-wide gene expression analysis of a murine model of prostate cancer progression: Deciphering the roles of IL-6 and p38 MAPK as potential therapeutic targets.

BACKGROUND:Prostate cancer (PCa) is the most commonly diagnosed cancer and the second leading cause of cancer-related deaths among adult males globally. The poor prognosis of PCa is largely due to late diagnosis of the disease when it has already progressed to an advanced stage marked by androgen-independence, thus necessitating new strategies for early detection and treatment. We construe that these direly needed advances are limited by our poor understanding of early events in the progression of PCa and that would thus represent ideal targets for early intervention. To begin to fill this void, we interrogated molecular "oncophenotypes" that embody the transition of PCa from an androgen-dependent (AD) to-independent (AI) state. METHODS:To accomplish this aim, we used our previously established AD and AI murine PCa cell lines, PLum-AD and PLum-AI, respectively, which recapitulate primary and progressive PCa morphologically and molecularly. We statistically surveyed global gene expressions in these cell lines by microarray analysis. Differential profiles were functionally interrogated by pathways, gene set enrichment and topological gene network analyses. RESULTS:Gene expression analysis of PLum-AD and PLum-AI transcriptomes (n = 3 each), revealed 723 differentially expressed genes (392 upregulated and 331 downregulated) in PLum-AI compared to PLum-AD cells. Gene set analysis demonstrated enrichment of biological functions and pathways in PLum-AI cells that are central to tumor aggressiveness including cell migration and invasion facilitated by epithelial-to-mesenchymal transition (EMT). Further analysis demonstrated that the p38 mitogen-activated protein kinase (MAPK) was predicted to be significantly activated in the PLum-AI cells, whereas gene sets previously associated with favorable response to the p38 inhibitor SB203580 were attenuated (i.e., inversely enriched) in the PLum-AI cells, suggesting that these aggressive cells may be therapeutically vulnerable to p38 inhibition. Gene set and gene-network analysis also alluded to activation of other signaling networks particularly those associated with enhanced EMT, inflammation and immune function/response including, but not limited to Tnf, IL-6, Mmp 2, Ctgf, and Ptges. Accordingly, we chose SB203580 and IL-6 to validate their effect on PLum-AD and PLum-AI. Some of the common genes identified in the gene-network analysis were validated at the molecular and functional level. Additionally, the vulnerability to SB203580 and the effect of IL-6 were also validated on the stem/progenitor cell population using the sphere formation assay. CONCLUSIONS:In summary, our study highlights pathways associated with an augmented malignant phenotype in AI cells and presents new high-potential targets to constrain the aggressive malignancy seen in the castration-resistant PCa

Novel 2‑(5-Imino‑5H‑isoquinolones[3,4‑b]quinoxalin-7-ylmethyl)-benzonitrile (DIQ3) and Other Related Derivatives Targeting Colon Cancer Cells: Syntheses and in Vitro Models

Chemotherapy has been shown to be effective in reducing the progression and development of cancer in metastatic patients. However, drug selectivity is still a major issue for most chemotherapeutics. In this study, we synthesized four novel heterocyclic compounds having similarity in structure with quinone systems whereby nitrogen atoms replace the oxygen atoms. The anticancer activity of these compounds (DIQ3-6) was tested against HCT116 human colon cancer cells. We showed that all four heterocycles caused significant reduction in colon cancer cell viability at doses as low as 4 μM, a concentration that was not cytotoxic to normal human FHs74Int intestinal cell lines. Interestingly, these heterocycles inhibited colon sphere formation in 3D cultures at first generation (G1), mainly because of inhibition of proliferation as evidenced by Ki67 staining. Thus, DIQ3 causes sufficient eradication of the self-renewal ability of the highly resistant cancer stem cells. This study represents the first documentation of the activity of these novel heterocyclic compounds, particularly compound DIQ3, and their potential therapeutic use in targeting colon cancer self-renewal capacity. Our findings provide the basis for proposing these nontoxic and stable compounds for additional testing against cancer