Promotes Cancer Cell Survival Research Articles

CSIG-21. THE ROLE OF GUT MICROBIOTA IN GLIOBLASTOMA: INSIGHTS FROM MICROBIOME-GENE EXPRESSION INTERACTIONS

Abstract Glioblastoma, the most aggressive form of primary brain tumor, remains a formidable clinical challenge due to its invasiveness and resistance to therapy. Emerging evidence suggests that the gut microbiome plays a crucial role in modulating cancer progression through complex interactions with host physiology. In this study, we investigated the influence of gut microbiota and tumor gene expression by analyzing stool and tissue samples from glioblastoma patients. Utilizing 16S rRNA sequencing of stool samples and NanoString gene expression analysis of tumor tissue samples, we explored the relationship between gut microbiome taxa and gene expression levels in tissue. Pathway analysis using KEGG and Gene Ontology databases was employed to elucidate the functional implications of these interactions. Our findings reveal contrasting effects of specific gut microbiota taxa and gene expression, with Fusobacterium demonstrating a potential oncogenic role, while Bifidobacteriaceae and Akkermansiaceae display potential tumor-suppressive effects. Fusobacterium is associated with the upregulation of key oncogenes and pathways promoting cancer cell survival, growth, and metabolism, whereas Bifidobacteriaceae and Akkermansiaceae are linked to the downregulation of genes involved in pathways promoting cancer cell survival and proliferation, such as MAPK signaling and stress response pathways, potentially inhibiting cancer cell growth. These results highlight the intricate interplay between gut microbiota composition and cancer biology and underscore the potential of gut microbiota modulation as a therapeutic strategy in glioblastoma management.

Enterococcus faecalis co-cultured with oral cancer cells exhibits higher virulence and promotes cancer cell survival, proliferation, and migration: an in vitro study.

Introduction. Enterococcus faecalis is a common pathogen associated with many oral diseases and is often isolated from oral cancer patients. However, limited information is available on its key virulence gene expression in oral cancer cell microenvironment and cancer cell behaviour in co-culture studies.Hypothesis. E. faecalis overexpresses virulence genes when co-cultured with oral cancer cells and possibly alters the tumour microenvironment, promoting oral cancer proliferation and survival.Aim. To investigate altered virulence gene expression in E. faecalis and oral cancer cell behaviour using in vitro co-culture experiments.Methodology. Cal27 cells were co-cultured with E. faecalis and assessed for their cell proliferation, apoptosis, migration and clonogenicity using standard cell culture assays. The levels of reactive oxygen species (ROS) and inflammatory cytokines, along with proliferative, angiogenic and apoptotic biomarker expressions, were also assessed. E. faecalis adherence to cancer cells was demonstrated by the gentamicin protection assay. Real time-PCR was used to analyse the expression of virulence genes.Results. Co-culture of Cal27 cells with E. faecalis showed significantly higher cell proliferation, migration and clonogenicity compared to the control (P<0.01). A significant increase in the levels of ROS and inflammatory cytokines and overexpression of Ki67, vascular endothelial growth factor, extracellular signal-regulated kinase 1/2, phosphoinositide 3 kinase and Akt was observed in the co-culture group. E. faecalis also downregulated p53 and Bax genes while upregulated Bcl-2. The virulence genes GelE, Asa and Ace were overexpressed in E. faecalis co-cultured with Cal27 cells.Conclusion. The results from this study indicate the possible risks of E. faecalis infection in oral cancer. An effective antibiotic strategy against E. faecalis to prevent complications associated with oral diseases, including cancer, is needed.

ATF4/NUPR1 axis promotes cancer cell survival and mediates immunosuppression in clear cell renal cell carcinoma

Cancer cells encounter unavoidable stress during tumor growth. The stress-induced transcription factor, activating transcription factor 4 (ATF4), has been reported to upregulate various adaptive genes involved in salvage pathways to alleviate stress and promote tumor progression. However, this effect is unknown in clear cell renal cell carcinoma (ccRCC). In this study, we found that ATF4 expression was remarkably upregulated in tumor tissues and associated with poor ccRCC outcomes. ATF4 depletion significantly impaired ccRCC cell proliferation, migration, and invasion in vitro and in vivo by inhibiting the AKT/mTOR and epithelial–mesenchymal transition (EMT)-related signaling pathway. RNA sequencing and functional studies identified nuclear protein 1 (NUPR1) as a key downstream target of ATF4 for repressing ferroptosis and promoting ccRCC cell survival. In addition, targeting ATF4 or pharmacological inhibition using NUPR1 inhibitor ZZW115 promoted antitumor immunity in syngeneic graft mouse models, represented by increased infiltration of CD4+ and CD8+ T cells. Furthermore, ZZW115 could improve the response to the PD-1 immune checkpoint blockade. The results demonstrate that the ATF4/NUPR1 signaling axis promotes ccRCC survival and facilitates tumor-mediated immunosuppression, providing a set of potential targets and prognostic indicators for ccRCC patients.Graphical abstract

9304 Integration of Glucocorticoid and Mineralocorticoid Receptor Signaling in Triple-negative Breast Cancer Models

Abstract Disclosure: S. Posani: None. C.A. Lange: None. Glucocorticoid receptors (GR) sense a convergence of host and cellular stress signaling to orchestrate an array of advanced cancer phenotypes associated with triple-negative breast cancer (TNBC) progression. The Lange lab reported p38 MAP kinase mediated phosphorylation of GR at serine 134 (Ser134) in response to tumor microenvironment-derived cytokines, such as TGF-beta-1. Phospho-Ser134-GR (p-Ser134-GR) upregulated gene sets that promote cancer cell survival, chemoresistance, altered metabolism, and migratory/invasive behavior in TNBC models. In addition to acting as ligands for GR, glucocorticoids also bind to and activate another closely related steroid hormone receptor - the mineralocorticoid receptor (MR). The elucidation of functional responses upon activation of MR remains an untapped area in breast cancer research. Our probe into public datasets (METABRIC, and TCGA) demonstrated significantly higher expression of MR transcripts in TNBC relative to luminal breast cancer. High expression of MR predicted worse overall survival in ERα-negative breast cancer patients compared to the low expressing cohort. Silencing of MR was carried out by siRNA-mediated knockdown and treatment with spironolactone, a competitive MR antagonist. Interestingly, MR knockdown significantly reduced the TGF-beta-1 induced migratory capacity of breast cancer cells compared to the wild-type control cells expressing endogenous MR. This biological phenotype of decreased TGF-beta-1 induced migration upon MR knockdown parallels the reduced migration we observed when the p38 MAPK site (Ser134 on GR was mutated to Ala in TNBC models. We therefore hypothesized that MR and GR may cooperate under the influence stress signaling in response to growth factors and cytokines abundantly present in the tumor-microenvironment. Preliminary data suggest that cytoplasmic p-Ser134-GR/MR complexes associate upon TGF-beta-1 treatment, while GR and/or MR ligands stimulate the formation of nuclear GR/MR complexes. We are further investigating cytokine- and stress-signal mediated regulation of GR/MR complexes and their functional role in TNBC biology. The overarching goal of this study is to elucidate if MR is a required GR binding-partner and a potential therapeutic target in GR- and cytokine-driven metastatic TNBC processes. Presentation: 6/2/2024

7873 Integration Of Glucocorticoid And Mineralocorticoid Receptor Signaling In Triple-Negative Breast Cancer Models

Abstract Disclosure: S. Posani: None. C.A. Lange: None. Glucocorticoid receptors (GR) sense a convergence of host and cellular stress signaling to orchestrate an array of advanced cancer phenotypes associated with triple-negative breast cancer (TNBC) progression. The Lange lab reported p38 MAP kinase mediated phosphorylation of GR at serine 134 (Ser134) in response to tumor microenvironment-derived cytokines, such as TGF-beta-1. Phospho-Ser134-GR (p-Ser134-GR) upregulated gene sets that promote cancer cell survival, chemoresistance, altered metabolism, and migratory/invasive behavior in TNBC models. In addition to acting as ligands for GR, glucocorticoids also bind to and activate another closely related steroid hormone receptor - the mineralocorticoid receptor (MR). The elucidation of functional responses upon activation of MR remains an untapped area in breast cancer research. Our probe into public datasets (METABRIC, and TCGA) demonstrated significantly higher expression of MR transcripts in TNBC relative to luminal breast cancer. High expression of MR predicted worse overall survival in ERα-negative breast cancer patients compared to the low expressing cohort. Silencing of MR was carried out by siRNA-mediated knockdown and treatment with spironolactone, a competitive MR antagonist. Interestingly, MR knockdown significantly reduced the TGF-beta-1 induced migratory capacity of breast cancer cells compared to the wild-type control cells expressing endogenous MR. This biological phenotype of decreased TGF-beta-1 induced migration upon MR knockdown parallels the reduced migration we observed when the p38 MAPK site (Ser134 on GR was mutated to Ala in TNBC models. We therefore hypothesized that MR and GR may cooperate under the influence stress signaling in response to growth factors and cytokines abundantly present in the tumor-microenvironment. Preliminary data suggest that cytoplasmic p-Ser134-GR/MR complexes associate upon TGF-beta-1 treatment, while GR and/or MR ligands stimulate the formation of nuclear GR/MR complexes. We are further investigating cytokine- and stress-signal mediated regulation of GR/MR complexes and their functional role in TNBC biology. The overarching goal of this study is to elucidate if MR is a required GR binding-partner and a potential therapeutic target in GR- and cytokine-driven metastatic TNBC processes. Presentation: 6/2/2024

9304 Integration Of Glucocorticoid And Mineralocorticoid Receptor Signaling In Triple-Negative Breast Cancer Models

Abstract Disclosure: S. Posani: None. C.A. Lange: None. Glucocorticoid receptors (GR) sense a convergence of host and cellular stress signaling to orchestrate an array of advanced cancer phenotypes associated with triple-negative breast cancer (TNBC) progression. The Lange lab reported p38 MAP kinase mediated phosphorylation of GR at serine 134 (Ser134) in response to tumor microenvironment-derived cytokines, such as TGF-beta-1. Phospho-Ser134-GR (p-Ser134-GR) upregulated gene sets that promote cancer cell survival, chemoresistance, altered metabolism, and migratory/invasive behavior in TNBC models. In addition to acting as ligands for GR, glucocorticoids also bind to and activate another closely related steroid hormone receptor - the mineralocorticoid receptor (MR). The elucidation of functional responses upon activation of MR remains an untapped area in breast cancer research. Our probe into public datasets (METABRIC, and TCGA) demonstrated significantly higher expression of MR transcripts in TNBC relative to luminal breast cancer. High expression of MR predicted worse overall survival in ERα-negative breast cancer patients compared to the low expressing cohort. Silencing of MR was carried out by siRNA-mediated knockdown and treatment with spironolactone, a competitive MR antagonist. Interestingly, MR knockdown significantly reduced the TGF-beta-1 induced migratory capacity of breast cancer cells compared to the wild-type control cells expressing endogenous MR. This biological phenotype of decreased TGF-beta-1 induced migration upon MR knockdown parallels the reduced migration we observed when the p38 MAPK site (Ser134 on GR was mutated to Ala in TNBC models. We therefore hypothesized that MR and GR may cooperate under the influence stress signaling in response to growth factors and cytokines abundantly present in the tumor-microenvironment. Preliminary data suggest that cytoplasmic p-Ser134-GR/MR complexes associate upon TGF-beta-1 treatment, while GR and/or MR ligands stimulate the formation of nuclear GR/MR complexes. We are further investigating cytokine- and stress-signal mediated regulation of GR/MR complexes and their functional role in TNBC biology. The overarching goal of this study is to elucidate if MR is a required GR binding-partner and a potential therapeutic target in GR- and cytokine-driven metastatic TNBC processes. Presentation: 6/2/2024

Abstract C047: Autophagy-mediated proline-supply is important for cell survival in pancreatic cancers

Abstract Oncogenic KRAS mutations present in 90–95% of pancreatic cancer patients. KRAS mutation in pancreatic cancer increased the dependency on glutamine and consumption of proline. Proline is a non-essential amino acid but it is important for the synthesis of proteins such as collagen, and also for precursors of antioxidant molecules. Several enzymes such as P5CS(ALDH18A1),PYCR1 and PYCR2 are involving proline synthesis. The effects of proline synthesis enzymes on pancreatic cancer cells are relatively less studied than that of enzymes catalyzing proline. Here, we examined the impact of proline synthesis enzymes on pancreatic cancer cell survival and proliferation. We first examined that exogenous proline promotes cell survival under low glutamine conditions in various pancreatic cancer cells. Exogenous proline supplementation increased some pancreatic cell survival even when glutamine was not sufficiently available, whereas proline supplement is dispensible for certain cell types of pancreatic cancer. Next, to investigate the importance of proline synthesis enzymes in cell survival, we measured the cell proliferation of pancreatic cancer with knock-down the proline synthesis enzymes. The knockdown of ALDH18A1 and PYCR1,2, which are proline biosynthesis enzyme genes, reduced cell survival in pancreatic cancer cells, suggesting that in PDAC cells, the enzymes that synthesize proline from glutamine are crucial for cancer cell survival and growth. To test the effect of proline-sysnthesis enzymes on autophagy, we measured autophagy flux in the cell harboring GFP-RFP-LC3 or GFP-LC3 as a reporter. Knockdown of proline synthesis enzymes, particularly ALDH18A1 or PYCR1 led to an increase in autophagy levels, indicating that proline-independent cells can bypass proline synthesis by autophagy induction in the absence of proline synthesis genes. Furthermore gemcitabine-resistant cells showed reduced levels of proline synthesis enzymes. In pancreatic cancer cell lines, proline promotes cancer cell survival, generated by both biosynthesis from glutamine and starvation-induced autophagy, which also critically important for supporting cellular drug resistance. Taken together, these results indicate that proline synthesis is mechanistically associated with autophagy induced by glutamine-starvation, which is pivotal for supplying proline in pancreatic cancer cells. Citation Format: Ji hyeon Kim, Heesun Cheong. Autophagy-mediated proline-supply is important for cell survival in pancreatic cancers [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C047.

Distinct conformational states enable transglutaminase 2 to promote cancer cell survival versus cell death

Transglutaminase 2 (TG2) is a GTP-binding, protein-crosslinking enzyme that has been investigated as a therapeutic target for Celiac disease, neurological disorders, and aggressive cancers. TG2 has been suggested to adopt two conformational states that regulate its functions: a GTP-bound, closed conformation, and a calcium-bound, crosslinking-active open conformation. TG2 mutants that constitutively adopt an open conformation are cytotoxic to cancer cells. Thus, small molecules that bind and stabilize the open conformation of TG2 could offer a new therapeutic strategy. Here, we investigate TG2, using static and time-resolved small-angle X-ray scattering (SAXS) and single-particle cryoelectron microscopy (cryo-EM), to determine the conformational states responsible for conferring its biological effects. We also describe a newly developed TG2 inhibitor, LM11, that potently kills glioblastoma cells and use SAXS to investigate how LM11 affects the conformational states of TG2. Using SAXS and cryo-EM, we show that guanine nucleotides bind and stabilize a monomeric closed conformation while calcium binds to an open state that can form higher order oligomers. SAXS analysis suggests how a TG2 mutant that constitutively adopts the open state binds nucleotides through an alternative mechanism to wildtype TG2. Furthermore, we use time resolved SAXS to show that LM11 increases the ability of calcium to bind and stabilize an open conformation, which is not reversible by guanine nucleotides and is cytotoxic to cancer cells. Taken together, our findings demonstrate that the conformational dynamics of TG2 are more complex than previously suggested and highlight how conformational stabilization of TG2 by LM11 maintains TG2 in a cytotoxic conformational state.

Bilayer 3D co‐culture platform inducing the differentiation of normal fibroblasts into cancer‐associated fibroblast like cells: New in vitro source to obtain cancer‐associated fibroblasts

AbstractThis study presents a novel in vitro bilayer 3D co‐culture platform designed to obtain cancer‐associated fibroblasts (CAFs)‐like cells. The platform consists of a bilayer hydrogel structure with a collagen/polyethylene glycol (PEG) hydrogel for fibroblasts as the upper layer and an alginate hydrogel for tumor cells as the lower layer. The platform enabled paracrine interactions between fibroblasts and cancer cells, which allowed for selective retrieval of activated fibroblasts through collagenase treatment for further study. Fibroblasts remained viable throughout the culture periods and showed enhanced proliferation when co‐cultured with cancer cells. Morphological changes in the co‐cultured fibroblasts resembling CAFs were observed, especially in the 3D microenvironment. The mRNA expression levels of CAF‐related markers were significantly upregulated in 3D, but not in 2D co‐culture. Proteomic analysis identified upregulated proteins associated with CAFs, further confirming the transformation of normal fibroblasts into CAF within the proposed 3D co‐culture platform. Moreover, co‐culture with CAF induced radio‐ and chemoresistance in pancreatic cancer cells (PANC‐1). Survival rate of cancer cells post‐irradiation and gemcitabine resistance increased significantly in the co‐culture setting, highlighting the role of CAFs in promoting cancer cell survival and therapeutic resistance. These findings would contribute to understanding molecular and phenotypic changes associated with CAF activation and provide insights into potential therapeutic strategies targeting the tumor microenvironment.

Overcoming Chemoresistance in Cancer: The Promise of Crizotinib.

Chemoresistance is a major obstacle in cancer treatment, often leading to disease progression and poor outcomes. It arises through various mechanisms such as genetic mutations, drug efflux pumps, enhanced DNA repair, and changes in the tumor microenvironment. These processes allow cancer cells to survive despite chemotherapy, underscoring the need for new strategies to overcome resistance and improve treatment efficacy. Crizotinib, a first-generation multi-target kinase inhibitor, is approved by the FDA for the treatment of ALK-positive or ROS1-positive non-small cell lung cancer (NSCLC), refractory inflammatory (ALK)-positive myofibroblastic tumors (IMTs) and relapsed/refractory ALK-positive anaplastic large cell lymphoma (ALCL). Crizotinib exists in two enantiomeric forms: (R)-crizotinib and its mirror image, (S)-crizotinib. It is assumed that the R-isomer is responsible for the carrying out various processes reviewed here The S-isomer, on the other hand, shows a strong inhibition of MTH1, an enzyme important for DNA repair mechanisms. Studies have shown that crizotinib is an effective multi-kinase inhibitor targeting various kinases such as c-Met, native/T315I Bcr/Abl, and JAK2. Its mechanism of action involves the competitive inhibition of ATP binding and allosteric inhibition, particularly at Bcr/Abl. Crizotinib showed synergistic effects when combined with the poly ADP ribose polymerase inhibitor (PARP), especially in ovarian cancer harboring BRCA gene mutations. In addition, crizotinib targets a critical vulnerability in many p53-mutated cancers. Unlike its wild-type counterpart, the p53 mutant promotes cancer cell survival. Crizotinib can cause the degradation of the p53 mutant, sensitizing these cancer cells to DNA-damaging substances and triggering apoptosis. Interestingly, other reports demonstrated that crizotinib exhibits anti-bacterial activity, targeting Gram-positive bacteria. Also, it is active against drug-resistant strains. In summary, crizotinib exerts anti-tumor effects through several mechanisms, including the inhibition of kinases and the restoration of drug sensitivity. The potential of crizotinib in combination therapies is emphasized, particularly in cancers with a high prevalence of the p53 mutant, such as triple-negative breast cancer (TNBC) and high-grade serous ovarian cancer (HGSOC).

Low BCL-xL expression in triple-negative breast cancer cells favors chemotherapy efficacy, and this effect is limited by cancer-associated fibroblasts

Triple negative breast cancers (TNBC) present a poor prognosis primarily due to their resistance to chemotherapy. This resistance is known to be associated with elevated expression of certain anti-apoptotic members within the proteins of the BCL-2 family (namely BCL-xL, MCL-1 and BCL-2). These regulate cell death by inhibiting pro-apoptotic protein activation through binding and sequestration and they can be selectively antagonized by BH3 mimetics. Yet the individual influences of BCL-xL, MCL-1, and BCL-2 on the sensitivity of TNBC cells to chemotherapy, and their regulation by cancer-associated fibroblasts (CAFs), major components of the tumor stroma and key contributors to therapy resistance remain to be delineated. Using gene editing or BH3 mimetics to inhibit anti-apoptotic BCL-2 family proteins in TNBC line MDA-MB-231, we show that BCL-xL and MCL-1 promote cancer cell survival through compensatory mechanisms. This cell line shows limited sensitivity to chemotherapy, in line with the clinical resistance observed in TNBC patients. We elucidate that BCL-xL plays a pivotal role in therapy response, as its depletion or pharmacological inhibition heightened chemotherapy effectiveness. Moreover, BCL-xL expression is associated with chemotherapy resistance in patient-derived tumoroids where its pharmacological inhibition enhances ex vivo response to chemotherapy. In a co-culture model of cancer cells and CAFs, we observe that even in a context where BCL-xL reduced expression renders cancer cells more susceptible to chemotherapy, those in contact with CAFs display reduced sensitivity to chemotherapy. Thus CAFs exert a profound pro-survival effect in breast cancer cells, even in a setting highly favoring cell death through combined chemotherapy and absence of the main actor of chemoresistance, BCL-xL.

Unraveling the intricacies of cancer-associated fibroblasts: a comprehensive review on metabolic reprogramming and tumor microenvironment crosstalk.

Cancer-associated fibroblasts (CAFs) are crucial component of tumor microenvironment (TME) which undergo significant phenotypic changes and metabolic reprogramming, profoundly impacting tumor growth. This review delves into CAF plasticity, diverse origins, and the molecular mechanisms driving their continuous activation. Emphasis is placed on the intricate bidirectional crosstalk between CAFs and tumor cells, promoting cancer cell survival, proliferation, invasion, and immune evasion. Metabolic reprogramming, a cancer hallmark, extends beyond cancer cells to CAFs, contributing to the complex metabolic interplay within the TME. The 'reverse Warburg effect' in CAFs mirrors the Warburg effect, involving the export of high-energy substrates to fuel cancer cells, supporting their rapid proliferation. Molecular regulations by key players like p53, Myc, and K-RAS orchestrate this metabolic adaptation. Understanding the metabolic symbiosis between CAFs and tumor cells opens avenues for targeted therapeutic strategies to disrupt this dynamic crosstalk. Unraveling CAF-mediated metabolic reprogramming provides valuable insights for developing novel anticancer therapies. This comprehensive review consolidates current knowledge, shedding light on CAFs' multifaceted roles in the TME and offering potential targets for future therapies.

Glucose deprivation triggers DCAF1-mediated inactivation of Rheb-mTORC1 and promotes cancer cell survival

Low glucose is a common microenvironment for rapidly growing solid tumors, which has developed multiple approaches to survive under glucose deprivation. However, the specific regulatory mechanism remains largely elusive. In this study, we demonstrate that glucose deprivation, while not amino acid or serum starvation, transactivates the expression of DCAF1. This enhances the K48-linked polyubiquitination and proteasome-dependent degradation of Rheb, inhibits mTORC1 activity, induces autophagy, and facilitates cancer cell survival under glucose deprivation conditions. This study identified DCAF1 as a new cellular glucose sensor and uncovered new insights into mechanism of DCAF1-mediated inactivation of Rheb-mTORC1 pathway for promoting cancer cell survival in response to glucose deprivation.

The novel SMYD3 inhibitor EM127 impairs DNA repair response to chemotherapy-induced DNA damage and reverses cancer chemoresistance

BackgroundSMYD3 has been found implicated in cancer progression. Its overexpression correlates with cancer growth and invasion, especially in gastrointestinal tumors. SMYD3 transactivates multiple oncogenic mechanisms, favoring cancer development. Moreover, it was recently shown that SMYD3 is required for DNA restoration by promoting homologous recombination (HR) repair.MethodsIn cellulo and in vivo models were employed to investigate the role of SMYD3 in cancer chemoresistance. Analyses of SMYD3-KO cells, drug-resistant cancer cell lines, patients’ residual gastric or rectal tumors that were resected after neoadjuvant therapy and mice models were performed. In addition, the novel SMYD3 covalent inhibitor EM127 was used to evaluate the impact of manipulating SMYD3 activity on the sensitization of cancer cell lines, tumorspheres and cancer murine models to chemotherapeutics (CHTs).ResultsHere we report that SMYD3 mediates cancer cell sensitivity to CHTs. Indeed, cancer cells lacking SMYD3 functions showed increased responsiveness to CHTs, while restoring its expression promoted chemoresistance. Specifically, SMYD3 is essential for the repair of CHT-induced double-strand breaks as it methylates the upstream sensor ATM and allows HR cascade propagation through CHK2 and p53 phosphorylation, thereby promoting cancer cell survival. SMYD3 inhibition with the novel compound EM127 showed a synergistic effect with CHTs in colorectal, gastric, and breast cancer cells, tumorspheres, and preclinical colorectal cancer models.ConclusionsOverall, our results show that targeting SMYD3 may be an effective therapeutic strategy to overcome chemoresistance.

Extracellular vesicles in cancer: golden goose or Trojan horse.

Intercellular communication can be mediated by direct cell-to-cell contact and indirect interactions through secretion of soluble chemokines, cytokines, and growth factors. Extracellular vesicles (EVs) have emerged as important mediators of cell-to-cell and cell-to-environment communications. EVs from tumor cells, immune cells, and stromal cells can remodel the tumor microenvironment and promote cancer cell survival, proliferation, metastasis, immune evasion, and therapeutic resistance. Most importantly, EVs as natural nanoparticles can be manipulated to serve as a potent delivery system for targeted cancer therapy. EVs can be engineered or modified to improve their ability to target tumors and deliver therapeutic substances, such as chemotherapeutic drugs, nucleic acids, and proteins, for the treatment of cancer. This review provides an overview of the biogenesis and recycling of EVs, discusses their roles in cancer development, and highlights their potential as a delivery system for targeted cancer therapy.

Iron promotes ovarian cancer malignancy and advances platinum resistance by enhancing DNA repair via FTH1/FTL/POLQ/RAD51 axis

Iron is crucial for cell DNA synthesis and repair, but an excess of free iron can lead to oxidative stress and subsequent cell death. Although several studies suggest that cancer cells display characteristics of ‘Iron addiction’, an ongoing debate surrounds the question of whether iron can influence the malignant properties of ovarian cancer. In the current study, we initially found iron levels increase during spheroid formation. Furthermore, iron supplementation can promote cancer cell survival, cancer spheroid growth, and migration; vice versa, iron chelators inhibit this process. Notably, iron reduces the sensitivity of ovarian cancer cells to platinum as well. Mechanistically, iron downregulates DNA homologous recombination (HR) inhibitor polymerase theta (POLQ) and relieves its antagonism against the HR repair enzyme RAD51, thereby promoting DNA damage repair to resist chemotherapy-induced damage. Additionally, iron tightly regulated by ferritin (FTH1/FTL) which is indispensable for iron-triggered DNA repair. Finally, we discovered that iron chelators combined with platinum exhibit a synergistic inhibitory effect on ovarian cancer in vitro and in vivo. Our findings affirm the pro-cancer role of iron in ovarian cancer and reveal that iron advances platinum resistance by promoting DNA damage repair through FTH1/FTL/POLQ/RAD51 pathway. Our findings highlight the significance of iron depletion therapy, revealing a promising avenue for advancing ovarian cancer treatment.

Combination of an aurora kinase inhibitor and the ABL tyrosine kinase inhibitor asciminib against ABL inhibitor-resistant CML cells

The development of BCR::ABL1-targeting tyrosine kinase inhibitors (TKIs) has improved the prognosis of patients with chronic myeloid leukemia (CML). However, resistance to ABL TKIs can develop in CML patients due to BCR::ABL1 point mutations and CML leukemia stem cell (LSC). Aurora kinases are essential kinases for cell division and regulate mitosis, especially the process of chromosomal segregation. Aurora kinase members also promote cancer cell survival and proliferation. This study analyzed whether aurora kinases were regulated in the progression of CML. It also evaluated the efficacy of the ABL TKI asciminib and the aurora kinase inhibitor LY3295668. The expressions of AURKA and AURKB were higher in the CML cells compared with normal cells using a public database (GSE100026). Asciminib or LY3295668 alone inhibited CML cells after 72 h, and cellular cytotoxicity was increased. The combined use of Asciminib and LY3295668 increased superior efficacy compared with either drug alone. Colony formation was reduced by cotreatment with asciminib and LY3295668. In the cell-cycle analyses, LY3295668 induced G2/M arrest. Cell populations in the sub-G1 phase were observed when cotreating with asciminib and LY3295668. The combination treatment also changed the mitochondrial membrane potential. In addition, AURKA shRNA transfectant cells had increased asciminib sensitivity. Combining asciminib and aurora kinase inhibition enhanced the efficacy and is proposed as a new therapeutic option for patients with CML. These findings have clinical implications for a potential novel therapeutic strategy for CML patients.

Extra-nuclear TERT counteracts oxidative stress and promotes progression in papillary thyroid carcinoma

The reactivation of TERT is associated with poor outcome in papillary thyroid cancer (PTC). Extra-telomeric functions of TERT were reported, with a protective role against oxidative stress (OS). The aim of the present study was to explore the extra-nuclear TERT localization in PTC and its role in cancer progression.TERT nuclear export under OS were analyzed in K1 PTC cell line. We investigated the role of different TERT localizations using specific TERT constructs that limit its localization to the nucleus or to the mitochondria. The effect of SRC kinase inhibitor PP2, which reduces TERT nuclear export, was investigated as well. Moreover, TERT localization was analyzed in 39 PTC tissues and correlated with the genetic profile and the level of OS, DNA damage and apoptosis in the tumors and with the clinical characteristics of the patients.We demonstrated that TERT is exported from the nucleus in response to OS induced either from H2O2 or the BRAF inhibitor PLX4720. We proved that extra-nuclear TERT reduces mitochondrial OS and induces mitochondrial fragmentation. Moreover, limiting mitochondrial TERT localization reduced proliferation, migration, AKT phosphorylation and glycolysis and increased DNA damage and p21 expression. Finally, in PTC tissues the fraction of mitochondrial/nuclear TERT resulted inversely correlated with OS and p21 expression and associated with tumor persistence.In conclusion, our data indicate that extra-nuclear TERT is involved in reducing the effect of excessive OS, thus promoting cancer cell survival. Extra-nuclear TERT may thus represent a marker of cancer progression and a possible therapeutic target in PTC.

Abstract 4744: Overcoming MK1775 resistance in upper gastrointestinal cancers with combined WEE1 and CHK1 inhibition

Abstract Background: Upper gastrointestinal cancers (UGC), encompassing esophageal and gastric cancers, rank among the top causes of cancer-related deaths globally, with esophageal cancer being the sixth and gastric cancer the fourth leading cause. Esophageal adenocarcinoma (EAC), predominant in the western world, shares histopathological and molecular characteristics with gastric cancer (GC). Despite these similarities, treatment challenges persist, exemplified by the limited efficacy of the WEE1 inhibitor MK1775 in clinical trials due to drug resistance. Our study investigates novel mechanisms underlying this resistance in UGC. Methods and results: RNA sequencing and immunohistochemistry staining demonstrated notable overexpression of WEE1 in over two hundred human EAC and GC samples compared to normal tissues. Concurrently, Western blot analysis revealed a positive correlation between WEE1 and CHK1 overexpression across 16 UGC cell lines. To categorize UGC cells based on their sensitivity to MK1775, we conducted ATP-glo cell viability assays, determining their half-maximal inhibitory concentration (IC50) values. Utilizing nuclear-cytosol separation, our data intriguingly uncovered, for the first time, that in MK1775-resistant cells, MK1775 treatment induces the abnormal translocation of phosphorylated CHK1 (p-CHK1) from the nucleus to the cytoplasm, a shift not observed in MK1775-sensitive cells. Further analysis through Western blot suggested that the cytoplasmic presence of p-CHK1 might trigger the activation of oncogenic STAT3 following MK1775 treatment. This activation appears to stimulate the expression of genes that promote cancer cell survival and drug resistance by enhancing cell survival and inhibiting apoptosis. Notably, combining the WEE1 inhibitor with the CHK1 inhibitor CHIR124 effectively inhibited CHK1 kinase activity and abrogated STAT3 phosphorylation, DNA binding, and transcriptional activity in UGC cells. Our findings strongly indicate that a combined therapy of WEE1 and CHK1 inhibitors could be a promising strategy to overcome MK1775 resistance in UGC cells. Our ongoing research will employ human-derived UGC organoids, patient-derived xenografts (PDXs), and human tissue samples to further validate these findings. Conclusions: Our study underscores the potential of combining WEE1 and CHK1 inhibitors to effectively combat MK1775 resistance in UGC, offering a promising direction for improved treatment strategies and patient outcomes in these challenging malignancies. Citation Format: Krishnapriya Thangaretnam, MD Obaidul Islam, Heng Lu, Dunfa Peng, Nadeem Sidiq Bhat, Mohammed Soutto, EL-Rifai Wael, Zheng Chen. Overcoming MK1775 resistance in upper gastrointestinal cancers with combined WEE1 and CHK1 inhibition [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 4744.

Abstract 581: Identification of potential biomarkers of response to RASMULTI(ON) plus anti-PD-1 combination in preclinical PDAC models

Abstract Mutant KRAS is present in more than 80% pancreatic cancer, promotes cancer cell survival, and protects cancer cells from immune recognition and attack. We have shown that inhibitors of the active state of RAS (RAS(ON)) promote cancer neoantigen recognition and synergize with immunotherapy in preclinical immunogenic models. 1 We evaluated the impact of RMC-6236, an investigational RASMULTI(ON) inhibitor on anti-tumor activity and tumor microenvironment (TME) remodeling in two congenic KRASG12D/+ GEMM-derived PDAC models resistant to anti-PD-1 therapy - KPCY clone 2 (6694c2) and clone 3 (2838c3), developed by Ben Stanger at UPenn. 2 Daily oral administration of RMC-6236 drove tumor regressions in KPCY clone 3, leading to 10% durable complete responses (CRs). In combination with anti-PD-1, 40% of durable CRs were achieved. However, RMC-6236 only drove tumor growth inhibition in KPCY clone 2, and no combination benefit with anti-PD-1. We conducted preclinical biomarker analyses in the TME and periphery to explore differences in response to RMC-6236 alone and in combination with anti-PD-1 in these models. Assessment of baseline predictive biomarkers in tumors elucidated that the KPCY clone 3 cells developed tumors with lower suppressive myeloid cells (gMDSCs) and higher CD8+ T cell infiltration compared to those derived from KPCY clone 2 cells. IHC analyses showed that T cells in clone 3 were in the tumor core, while CD8+ T cells in clone 2 were at the tumor border (the latter frequently observed in PDAC patients). RMC-6236 induced transformation of the TME in favor of anti-tumor immunity in only the KPCY clone 3 - with decreased immunosuppressive gMDSCs, and increased T cells. Limited modulation of the TME was observed in the KPCY clone 2 cells-derived tumors, and gMDSC levels significantly higher than those in baseline tumors of KPCY clone 3. Peripheral immunophenotyping analyses revealed that baseline peripheral suppressive myeloid cells (mMDSCs) were significantly higher in mice harboring tumors originated from KPCY clone 2 cells, suggestive of a more systemic immunosuppressive status. Studies are ongoing to assess additional peripheral immune signatures of preclinical activity of RMC-6236 in combination with anti-PD-1. Taken together, baseline tumor levels of suppressive myeloid cells (gMDSCs) were shown to be a negative predictive biomarker for treatment outcome to RMC-6236 +/- anti-PD-1 in KRAS mutant preclinical PDAC models. Peripheral mMDSCs were shown to be higher in the mice with tumors from the PDAC model not sensitive to the combination of RMC-6236 with anti-PD-1, suggesting that it could be predictive of poor outcome for this combination. These studies in immune-competent models of RAS mutant PDAC allow us to generate tumor and blood-based biomarkers that may predict outcomes to RAS(ON) inhibitor combinations in the clinic. 1 Menard et al. AACR 2023 2 Li et al. Immunity 2018 Citation Format: Lillian Seu, Marie Menard, Jasmine Lee, Christopher Chow, Cristina Blaj, Mariela Moreno Ayala, Nataliya Shifrin, Avery Salmon, Swetha Ganesh, Philip Wig, Alice Kumamoto, Paola Soto-Perez, Tippy Taavili, Vivian Morton, James W. Evans, Jacqueline A. Smith, Elsa Quintana. Identification of potential biomarkers of response to RASMULTI(ON) plus anti-PD-1 combination in preclinical PDAC models [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 581.