Mechanisms Of Chemoresistance Research Articles

Abstract 1190 Investigating chemoresistance mechanisms and collateral responses in pancreatic ductal adenocarcinoma

Abstract 1190 Investigating chemoresistance mechanisms and collateral responses in pancreatic ductal adenocarcinoma

Novel players in the development of chemoresistance in ovarian cancer: ovarian cancer stem cells, non-coding RNA and nuclear receptors.

Ovarian cancer (OC) ranks as the fifth leading factor for female mortality globally, with a substantial burden of new cases and mortality recorded annually. Survival rates vary significantly based on the stage of diagnosis, with advanced stages posing significant challenges to treatment. OC is primarily categorized as epithelial, constituting approximately 90% of cases, and correct staging is essential for tailored treatment. The debulking followed by chemotherapy is the prevailing treatment, involving platinum-based drugs in combination with taxanes. However, the efficacy of chemotherapy is hindered by the development of chemoresistance, both acquired during treatment (acquired chemoresistance) and intrinsic to the patient (intrinsic chemoresistance). The emergence of chemoresistance leads to increased mortality rates, with many advanced patients experiencing disease relapse shortly after initial treatment. This review delves into the multifactorial nature of chemoresistance in OC, addressing mechanisms involving transport systems, apoptosis, DNA repair, and ovarian cancer stem cells (OCSCs). While previous research has identified genes associated with these mechanisms, the regulatory roles of non-coding RNA (ncRNA) and nuclear receptors in modulating gene expression to confer chemoresistance have remained poorly understood and underexplored. This comprehensive review aims to shed light on the genes linked to different chemoresistance mechanisms in OC and their intricate regulation by ncRNA and nuclear receptors. Specifically, we examine how these molecular players influence the chemoresistance mechanism. By exploring the interplay between these factors and gene expression regulation, this review seeks to provide a comprehensive mechanism driving chemoresistance in OC.

EGR1 mediates MDR1 transcriptional activity regulating gemcitabine resistance in pancreatic cancer

BackgroundGemcitabine is a cornerstone drug for the treatment of all stages of pancreatic cancer and can prolong the survival of patients with pancreatic cancer, but resistance to gemcitabine in pancreatic cancer patients hinders its efficacy. The overexpression of Early growth response 1(EGR1) in pancreatic ductal adenocarcinoma as a mechanism of gemcitabine chemoresistance in pancreatic cancer has not been explored. The major mechanisms of gemcitabine chemoresistance are related to drug uptake, metabolism, and action. One of the common causes of tumor multidrug resistance (MDR) to chemotherapy in cancer cells is that transporter proteins increase intracellular drug efflux and decrease drug concentrations by inducing anti-apoptotic mechanisms. It has been reported that gemcitabine binds to MDR1 with high affinity. The purpose of this research was to investigate the potential mechanisms by which EGR1 associates with MDR1 to regulate gemcitabine resistance in pancreatic cancer cells.MethodsThe following in vitro and in vivo techniques were used in this research to explore the potential mechanisms by which EGR1 binds to MDR1 to regulate gemcitabine resistance in pancreatic cancer cells. Cell culture; in vitro and in vivo study of EGR1 function by loss of function analysis. Binding of EGR1 to the MDR1 promoter was detected using the ChIP assay. qRT-PCR, Western blot assays to detect protein and mRNA expression; use of Annexin V apoptosis detection assay to test apoptosis; CCK8, Edu assay to test cell proliferation viability. The animal model of pancreatic cancer subcutaneous allograft was constructed and the tumours were stained with hematoxylin eosin and Ki-67 expression was detected using immunohistochemistry.FindingsWe revealed that EGR1 expression was increased in different pancreatic cancer cell lines compared to normal pancreatic ductal epithelial cells. Moreover, gemcitabine treatment induced upregulation of EGR1 expression in a dose- and time-dependent manner. EGR1 is significantly enriched in the MDR1 promoter sequence.Upon knockdown of EGR1, cell proliferation was impaired in CFPAC-1 and PANC-1 cell lines, apoptosis was enhanced and MDR1 expression was decreased, thereby partially reversing gemcitabine chemoresistance. In animal experiments, knockdown of EGR1 enhanced the inhibitory effect of gemcitabine on tumor growth compared with the sh-NC group.ConclusionsOur study suggests that EGR1 may be involved in the regulation of MDR1 to enhance gemcitabine resistance in pancreatic cancer cells. EGR1 could be a novel therapeutic target to overcome gemcitabine resistance in pancreatic cancer.

MicroRNA-302a enhances 5-fluorouracil sensitivity in HepG2 cells by increasing AKT/ULK1-dependent autophagy-mediated apoptosis

Abstract Objectives MicroRNA-302a (miR-302a) has been implicated in the oncogenic processes, but its role in hepatocellular carcinoma (HCC) chemoresistance and related mechanisms are still unclear. Therefore, the aim of this study was to investigate the role of miR-302a in HCC chemoresistance and elucidate its underlying mechanism. Methods In this study, we detected the level of miR-302a in HCC tissues (including chemoresistant and chemosensitive tissues), non-tumor tissues, liver cancer cell lines, and 5-fluorouracil (5-FU)-resistant cells (HepG2/R). Additionally, we conducted cell viability, apoptosis, and autophagy analyses as well as assessed the levels of cleaved caspase-3, cleaved caspase-9, microtubule-associated protein 1 light chain 3 beta II (LC3B-II), Akt, and UNC-51 like kinase 1 (ULK1) in HepG2 cells transfected with miR-302a mimic or inhibitor prior to 5-FU treatment. Lastly, we predicted the target of miR-302a and verified the relationship between miR-302a and Akt by luciferase reporter and functional repair assays. Results Our results revealed that miR-302a was down-regulated in HCC tissues (p<0.01), especially in chemoresistant tissues (p<0.01). Consistently, the miR-302a level exhibited a lower expression in HepG2/R cells compared to their parental cells (p<0.01). Furthermore, the 5-FU-induced apoptosis and autophagy of HepG2 cells were promoted by miR-302a over-expression and diminished by miR-302a inhibition (p<0.01). Target analysis revealed that miR-302a could directly target Akt. Moreover, miR-302a inhibited Akt expression and subsequently elevated ULK1 expression (p<0.01). Inhibition of ULK1 could abrogate the sensitization of overexpressed miR-302a to 5-FU in HepG2 cells (p<0.01). Conclusions Altogether, our results demonstrate that the down-regulation of miR-302a promotes 5-FU resistance in HCC by attenuating the Akt/ULK1 axis-dependent autophagy and apoptosis.

Transcription factor ATMIN facilitates chemoresistance in nasopharyngeal carcinoma

Despite that the docectaxel-cisplatin-5-fluorouracil (TPF) induction chemotherapy has greatly improved patients’ survival and became the first-line treatment for advanced nasopharyngeal carcinoma (NPC), not all patients could benefit from this therapy. The mechanism underlying the TPF chemoresistance remains unclear. Here, by analyzing gene-expression microarray data and survival of patients who received TPF chemotherapy, we identify transcription factor ATMIN as a chemoresistance gene in response to TPF chemotherapy in NPC. Mass spectrometry and Co-IP assays reveal that USP10 deubiquitinates and stabilizes ATMIN protein, resulting the high-ATMIN expression in NPC. Knockdown of ATMIN suppresses the cell proliferation and facilitates the docetaxel-sensitivity of NPC cells both in vitro and in vivo, while overexpression of ATMIN exerts the opposite effect. Mechanistically, ChIP-seq combined with RNA-seq analysis suggests that ATMIN is associated with the cell death signaling and identifies ten candidate target genes of ATMIN. We further confirm that ATMIN transcriptionally activates the downstream target gene LCK and stabilizes it to facilitate cell proliferation and docetaxel resistance. Taken together, our findings broaden the insight into the molecular mechanism of chemoresistance in NPC, and the USP10-ATMIN-LCK axis provides potential therapeutic targets for the management of NPC.

Abstract B023: Paracrine enhancement of tumor cell proliferation provides indirect stroma-mediated chemoresistance via acceleration of tumor recovery between chemotherapy cycles

Abstract The ability of tumors to survive therapy reflects both cell-intrinsic and microenvironmental mechanisms. Across many cancers, including triple-negative breast cancer (TNBC), a high stroma/tumor ratio correlates with poor survival. In many contexts, this correlation can be explained by the direct reduction of therapy sensitivity by stroma-produced paracrine factors. We sought to explore whether this direct effect contributes to the link between stroma and poor responses to chemotherapies. Our in vitro studies with panels of TNBC cell line models and stromal isolates failed to detect a direct modulation of chemoresistance. At the same time, consistent with prior studies, we observed treatment-independent enhancement of tumor cell proliferation by fibroblast-produced secreted factors. Using spatial statistics analyses, we found that proximity to stroma is often associated with enhanced tumor cell proliferation in vivo. Based on these observations, we hypothesized an indirect link between stroma and chemoresistance, where stroma-augmented proliferation potentiates the recovery of residual tumors between chemotherapy cycles. To evaluate the feasibility of this hypothesis, we developed a spatial agent-based model of stroma impact on proliferation/death dynamics. The model was quantitatively parameterized using inferences from histological analyses and experimental studies. We found that the observed enhancement of tumor cell proliferation within stroma-proximal niches can enable tumors to avoid elimination over multiple chemotherapy cycles. Therefore, our study supports the existence of a novel, indirect mechanism of environment-mediated chemoresistance that might contribute to the negative correlation between stromal content and poor therapy outcomes. Citation Format: Daria Miroshnychenko, Tatiana Miti, Pragya Kumar, Anna Miller, Mark Laurie, Nathalia Giraldo, Marilyn M. Bui, Philipp M. Altrock, David Basanta, Anriy Marusyk. Paracrine enhancement of tumor cell proliferation provides indirect stroma-mediated chemoresistance via acceleration of tumor recovery between chemotherapy cycles [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Cancer Evolution and Data Science: The Next Frontier; 2023 Dec 3-6; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_2):Abstract nr B023.

Meta-analysis of microarray data to determine gene indicators involved in cisplatin resistance in non-small cell lung cancer.

Lung cancer is a major cause of cancer-related mortality worldwide, with a 5-year survival rate of approximately 22%. Cisplatin is one of the standard first-line chemotherapeutic agents for non-small cell lung cancer (NSCLC), but its efficacy is often limited by the development of resistance. Despite extensive research on the molecular mechanisms of chemoresistance, the underlying causes remain elusive and complex. We analyzed three microarray datasets to find the gene signature and key pathways related to cisplatin resistance in NSCLC. We compared the gene expression of sensitive and resistant NSCLC cell lines treated with cisplatin. We found 274 DEGs, including 111 upregulated and 163 downregulated genes, in the resistant group. Gene set enrichment analysis showed the potential roles of several DEGs, such as TUBB2B, MAPK7, TUBAL3, MAP2K5, SMUG1, NTHL1, PARP3, NTRK1, G6PD, PDK1, HEY1, YTHDF2, CD274, and MAGEA1, in cisplatin resistance. Functional analysis revealed the involvement of pathways, such as gap junction, base excision repair, central carbon metabolism, and Notch signaling in the resistant cell lines. We identified several molecular factors that contribute to cisplatin resistance in NSCLC cell lines, involving genes and pathways that regulate gap junction communication, DNA damage repair, ROS balance, EMT induction, and stemness maintenance. These genes and pathways could be targets for future studies to overcome cisplatin resistance in NSCLC.

Mass Spectrometry Investigation of Some ATP-Binding Cassette (ABC) Proteins.

Drug resistance remains one of the main causes of poor outcome in cancer therapy. It is also becoming evident that drug resistance to both chemotherapy and to antibiotics is driven by more than one mechanism. So far, there are at least eight recognized mechanisms behind such resistance. In this review, we choose to discuss one of these mechanisms, which is known to be partially driven by a class of transmembrane proteins known as ATP-binding cassette (ABC) transporters. In normal tissues, ABC transporters protect the cells from the toxic effects of xenobiotics, whereas in tumor cells, they reduce the intracellular concentrations of anticancer drugs, which ultimately leads to the emergence of multidrug resistance (MDR). A deeper understanding of the structures and the biology of these proteins is central to current efforts to circumvent resistance to both chemotherapy, targeted therapy, and antibiotics. Understanding the biology and the function of these proteins requires detailed structural and conformational information for this class of membrane proteins. For many years, such structural information has been mainly provided by X-ray crystallography and cryo-electron microscopy. More recently, mass spectrometry-based methods assumed an important role in the area of structural and conformational characterization of this class of proteins. The contribution of this technique to structural biology has been enhanced by its combination with liquid chromatography and ion mobility, as well as more refined labelling protocols and the use of more efficient fragmentation methods, which allow the detection and localization of labile post-translational modifications. In this review, we discuss the contribution of mass spectrometry to efforts to characterize some members of the ATP-binding cassette (ABC) proteins and why such a contribution is relevant to efforts to clarify the link between the overexpression of these proteins and the most widespread mechanism of chemoresistance.

Neoadjuvant chemotherapy-induced remodeling of human hormonal receptor-positive breast cancer revealed by single-cell RNA sequencing

Hormone receptor-positive breast cancer (HR+ BC) is known to be relatively insensitive to chemotherapy, and since chemotherapy has remained the major neoadjuvant therapy for HR+ BC, the undetermined mechanism of chemoresistance and how chemotherapy reshapes the immune microenvironment need to be explored by high-throughput technology. By using single-cell RNA sequencing and multiplexed immunofluorescence staining analysis of HR+ BC samples (paired pre- and post-neoadjuvant chemotherapy (NAC)), the levels of previously unrecognized immune cell subsets, including CD8+ T cells with pronounced expression of T-cell development (LMNA) and cytotoxicity (FGFBP2) markers, CD4+ T cells characterized by proliferation marker (ATP1B3) expression and macrophages characterized by CD52 expression, were found to be increased post-NAC, which were predictive of chemosensitivity and their antitumor function was also validated with in vitro experiments. In terms of immune checkpoint expression of CD8+ T cells, we found their changes were inconsistent post-NAC, that LAG3, VSIR were decreased, and PDCD1, HAVCR2, CTLA4, KLRC1 and BTLA were increased. In addition, we have identified novel genomic and transcriptional patterns of chemoresistant cancer cells, both innate and acquired, and have confirmed their prognostic value with TCGA cohorts. By shedding light on the ecosystem of HR+ BC reshaped by chemotherapy, our results uncover valuable candidates for predicting chemosensitivity and overcoming chemoresistance in HR+ BC.

Hepatitis B surface antigen positivity is associated with poor short- and long-term outcomes in patients with diffuse large B-cell lymphoma who received CHOP or R-CHOP.

The development of diffuse large B-cell lymphoma (DLBCL) is closely related to the host infection status. China is a highly endemic area for hepatitis B virus (HBV) infection. It is not clear whether HBV infection has a consistent effect on the prognostic implications of patients with DLBCL in different treatment settings. We conducted a cohort study of 692 patients with DLBCL receiving three or more cycles of treatment with a CHOP or R-CHOP regimen from the First Hospital of Jilin University between July 2011 and July 2022. The patients were divided into two groups based on their hepatitis B surface antigen (HBsAg) status: HBsAg-positive (n = 84, 12.1%) and HBsAg-negative (n = 608, 87.9%) groups. Tumor specimens from 180 patients with primary DLBCL were collected for next-generation sequencing (NGS). The HBsAg-positive group had more frequent abnormal liver function (P= 0.003), hypoalbuminemia (P < 0.001), incidence of > 2 extranodal organs (P= 0.011), and spleen involvement (P < 0.001) than the HBsAg-negative group. HBsAg-positive patients had lower complete response (CR) and overall response rates (ORR) rates (all the p values < 0.05), in either the CHOP group or R-CHOP group. Among patients receiving R-CHOP, the rates of disease progression within 12 and 24 months were higher in the HBsAg-positive group than in the HBsAg-negative group (P=0.018, P=0.029). However, no significant difference in disease progression was observed between HBsAg-positive and HBsAg-negative patients in the CHOP group(P > 0.05). HBsAg positivity (OS: HR [95% CI] = 2.511 [1.214-5.192], P = 0.013) was only associated with poorer OS in the CHOP group. Whereas in the R-CHOP group, HBsAg positivity was associated with both poorer OS and PFS (OS: HR [95% CI] = 1.672 [1.050-2.665], P = 0.030; PFS: HR [95% CI] = 1.536 [1.013-2.331], P = 0.043). Additionally, HBsAg-positive patients with DLBCL also had a higher prevalence of mutations in MYC, ATM, PTPN6, and epigenetically regulated genes. These findings suggest that HBsAg-positive DLBCL patients may represent a distinct subgroup with a poorer prognosis. The standard therapies may be insufficient and new therapeutic strategies should be developed based on a better understanding of the underlying mechanisms of chemoresistance.

Abstract B085: K17-induced pyrimidine biosynthesis drives chemoresistance in PDAC

Abstract Background: The 5-year survival rate of pancreatic cancer is extremely low compared with other cancers, although it has increased to 12% in 2023 in the United States. 80% of pancreatic ductal adenocarcinoma (PDAC) patients are not eligible for surgical procedure, and unfortunately, PDAC is refractory to standard-of-care chemotherapy. Thus, developing novel and more effective treatment strategies for PDAC is urgently needed. We previously reported keratin 17 (K17) as a novel negative prognostic and predictive biomarker, whose overexpression confers the resistance to chemotherapies. Here, we investigated the mechanisms of chemoresistance and tumor-specific vulnerabilities that can be exploited for K17-mediated targeted therapies. Methods: Survival analyses, immunohistochemistry (IHC), and matrix assisted laser desorption/ionization mass spectrometry (MALDI MSI) metabolite imaging were applied in patient derived samples. The K17 stable expression cell line models (KPC and PANC-1) and K17 loss-of-function cell line model (L3.6) were generated, where the analyses were applied including western blots, qRT-PCR, mass spectrometric metabolomics analysis, immunofluorescence imaging, cell viability and proliferation assays. KPC cells with or without K17 expression were orthotopically implanted into the head of the pancreas of c57B6J mice for tumor growth and treatment study. Results: Unbiased metabolomic studies in isogenic PDAC models identified several key metabolic pathways that are upregulated in the presence of K17. We demonstrate that K17 increases pyrimidine biosynthesis, a pathway that drives chemoresistance. Patient dataset analysis revealed that K17 expression and enzymes involved in pyrimidine, but not purine, de novo biosynthesis is associated with shorter patient survival. Furthermore, K17-expressing cells were more sensitive to Brequinar, a specific inhibitor of dihydroorotate dehydrogenase (DHODH), the rate-limiting enzyme in de novo pyrimidine biosynthetic pathway. Targeting DHODH by small interfering RNA or by Brequinar with Gemcitabine synergistically inhibited the viability of K17- positive cells. Importantly, the combination of Gemcitabine and Brequinar significantly inhibited the growth of K17-expressing tumors and extended survival of mice bearing K17-positive tumors. Mechanistically, K17 increased mitochondrial DHODH translocation which made these cells more sensitive to Brequinar. We also found that the coil 2 domain of K17 was crucial for triggering metabolic reprogramming and promoting tumor aggression. Conclusions: Overall, we define a novel connection between K17, nucleotide metabolism, and chemoresistance in PDAC. We report for the first time that K17, a negative biomarker of the most aggressive PDAC subtype, drives chemoresistance by up-regulating de novo pyrimidine biosynthesis, which provides a tumor-specific vulnerability: DHODH. Further study could lead to the development of a DHODH targeted therapy for K17-expressing PDAC. Citation Format: Yinghuan Lyu, Kenneth Shroyer, Chun-Hao Pan, Robert Tseng, Md Afjalus Siraj, Girish Halemirle Rajacharya, Bo Chen, Katie L Donnelly, Michael Horowitz, Carlos Mauricio Mejia Arbelaez, Sumedha Chowdhury, Lyanne Oblein, Natalia Marchenko, Luisa Escobar-Hoyos, Pankaj K. Singh. K17-induced pyrimidine biosynthesis drives chemoresistance in PDAC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B085.

Abstract A056: Targeting the mevalonate biosynthesis pathway in gemcitabine resistant pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDA) is a lethal malignancy with a low survival rate. A lack of durable responses to chemotherapy renders its treatment particularly challenging and largely contributes to the devastating prognosis. Gemcitabine, a pyrimidine anti-metabolite, is a cornerstone in PDA therapy, but resistance remains a major hurdle in clinical care. Multiple mechanisms of chemoresistance have been attributed to rewired metabolic pathways in PDA cells. Accordingly, we hypothesized that altered metabolism in gemcitabine resistance represents a therapeutic vulnerability that can be targeted to improve response to treatment. To investigate metabolic vulnerabilities in gemcitabine resistance, we generated gemcitabine resistant murine PDA cell lines and assembled patient-derived gemcitabine high versus low responder organoids. Transcriptomic profiling revealed a downregulation of the mevalonate biosynthesis pathway and its rate-limiting enzyme, HMG-CoA reductase, upon the acquisition of gemcitabine resistance. Upregulation of this pathway has been proposed as a primary resistance mechanism to statins, HMG-CoA reductase inhibitors that are frequently prescribed to treat patients with hyperlipidemia. Accordingly, we postulated that statins would be more potent in gemcitabine resistant PDA cells than in their sensitive counterparts. Indeed, resistant cells were exquisitely susceptible to inhibition of the mevalonate pathway, an observation consistent across multiple clinically available statins. Downstream rescue experiments suggested that the main impact of blocking the mevalonate biosynthesis pathway is through lowered levels of geranylgeranyl pyrophosphate and reduced protein geranylation. To validate our findings in vivo, we implanted gemcitabine resistant murine PDA cells into syngeneic mice that were fed with a modified diet precluding geranylgeraniol. Here, the treatment combination gemcitabine and pitavastatin inhibited tumor growth of resistant allografts. Collectively, these data suggest that targeting the HMG-CoA reductase is a metabolic vulnerability that is gained in PDA cells upon the acquisition of gemcitabine resistance. The combination therapy gemcitabine and pitavastatin, two widely used compounds in patients, has potential to translate into a clinical benefit and improve survival in this deadly disease. Citation Format: Alica K. Beutel, Sabrina Calderon, Ethan Nghiem, Rima Singh, Cecily Anaraki, Kevin Gulay, Herve Tiriac, Alexander Kleger, Thomas Seufferlein, Alexander Muir, Cholsoon Jang, Dennis Juarez, David Fruman, Christopher Halbrook. Targeting the mevalonate biosynthesis pathway in gemcitabine resistant pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A056.

Peroxiredoxin-1 as a molecular chaperone that regulates glutathione S-transferase P1 activity and drives mutidrug resistance in ovarian cancer cells

Ovarian cancer is among the most prevalent gynecological malignancies around the globe. Nonetheless, chemoresistance continues to be one of the greatest obstacles in the treatment of ovarian cancer. Therefore, understanding the mechanisms of chemoresistance and identifying new treatment options for ovarian cancer patients is urgently required. In this study, we found that the mRNA and protein expression levels of PRDX1 were significantly increased in cisplatin resistant A2780/CDDP cells. Cell survival assays revealed that PRDX1 depletion substantially increased ovarian cancer cell sensitivity to cisplatin, docetaxel, and doxorubicin. Additionally, PRDX1 significantly increased GSTP1 activity, resulting in multidrug resistance. Biochemical experiments showed that PRDX1 interacted with GSTP1 through Cysteine 83, which regulated GSTP1 activity as well as chemotherapy resistance in ovarian cancer cells. Our findings indicate that the molecular chaperone activity of PRDX1 is a promising new therapeutic target for ovarian cancer.

RUNX2 prompts triple negative breast cancer drug resistance through TGF-β pathway regulating breast cancer stem cells

Triple-negative breast cancer (TNBC) stands out as the most aggressive subtype within the spectrum of breast cancer. The current clinical guidelines propose treatment strategies involving cytotoxic agents like epirubicin or paclitaxel. However, the emergence of acquired resistance frequently precipitates secondary tumor recurrence or the spread of metastasis. In recent times, significant attention has been directed toward the transcription factor RUNX2, due to its pivotal role in both tumorigenesis and the progression of cancer. Previous researches suggest that RUNX2 might be intricately linked to the development of resistance against chemotherapy, with its mechanism of action possibly intertwined with the signaling of TGF-β. Nevertheless, the precise interplay between their effects and the exact molecular mechanisms underpinning chemoresistance in TNBC remain elusive. Therefore, we have taken a multifaceted approach from in vitro and in vivo experiments to validate the relationship between RUNX2 and TGF-β and to search for their pathogenic mechanisms in chemoresistance. In conclusion, we found that RUNX2 affects chemoresistance by regulating cancer cell stemness through direct binding to TGF-β, and that TGF-β dually regulates RUNX2 expression. The important finding will provide a new reference for clinical reversal of the development of chemoresistance in breast cancer.

Characterization of residual cancer by comparison of a pair of organoids established from a patient with esophageal squamous cell carcinoma before and after neoadjuvant chemotherapy.

Neoadjuvant chemotherapy (NAC) followed by surgery is a standard approach for management of locally advanced esophageal squamous cell carcinoma (ESCC). Patients who do not respond well to NAC have a poor prognosis. Despite extensive research, the mechanisms of chemoresistance in ESCC remain largely unknown. Here, we established paired tumor organoids-designated as PreNAC-O and PostNAC-O-from one ESCC patient before and after NAC, respectively. Although the two organoids did not exhibit significant differences in proliferation, morphology or drug sensitivity in vitro, the tumorigenicity of PostNAC-O in vivo was significantly higher than that of PreNAC-O. Xenografts from PreNAC-O tended to exhibit keratinization, while those from PostNAC-O displayed conspicuous necrotic areas. The tumorigenicity of PostNAC-O xenografts during the chemotherapy was comparable to that of PreNAC-O without treatment. Furthermore, the gene expression profiles of the xenografts suggested that expression of genes involved in the EMT and/or hypoxia response might be related to the tumorigenicity of PostNAC-O. Our data suggested that the tumorigenicity of residual cancer had been enhanced, outweighing the effects of chemotherapy, rather than being attributable to intrinsic chemoresistance. Further studies are required to clarify the extent to which residual cancers share a common mechanism similar to that revealed here.

NRF2 activation in BON‑1 neuroendocrine cancercells reduces the cytotoxic effects of a novel Ruthenium(II)‑curcumin compound: A pilot study.

Gastroenteropancreatic neuroendocrine neoplasms (GEP‑NEN) are a group of rare tumors whose specific pathogenetic mechanisms of resistance to therapies have not been completely revealed yet. Chemotherapy is the main therapeutic approach in patients with GEP‑NEN, however, novel combination regimens and targeted therapy are continuously explored. In the present study, the anticancer effect of a novel Ruthenium (Ru)(II)‑Bisdemethoxycurcumin (Ru‑bdcurc) compound was evaluated in BON‑1 cell line, one of the few cell lines derived from GEP‑NEN, largely used in experimental research of this type of tumors. The experimental data revealed that the Ru‑bdcurc compound induced cell death in a dose‑dependent manner, invitro. Biochemical studies demonstrated that, in response to the lower dose of treatment, BON‑1 cells activated the nuclear factor erythroid 2‑related factor 2 (NRF2) pathway with induction of some of its targets including catalase and p62 as well as of the antiapoptotic marker Bcl2, all acting as chemoresistance mechanisms. NRF2 induction associated also with increased expression of endogenous p53 which is reported to be dysfunctional in BON‑1 cells and to inhibit apoptosis. Genetic or pharmacologic targeting of NRF2 inhibited the activation of the NRF2 pathway, as well as of endogenous dysfunctional p53, in response to the lower dose of Ru‑bdcurc, increasing the cell death. To assess the interplay between NRF2 and dysfunctional p53, genetic targeting of p53 showed reduced activation of the NRF2 pathway in response to the lower dose of Ru‑bdcurc, increasing the cell death. These findings identified for the first time a possible dysfunctional p53/NRF2 interplay in BON‑1 cell line that can be a novel key determinant in cell resistance to cytotoxic agents to be evaluated also in GEP‑NEN.

The Interaction of Calcium-Sensing Receptor with KIF11 Enhances Cisplatin Resistance in Lung Adenocarcinoma via BRCA1/cyclin B1 pathway.

Cisplatin (DDP) is commonly used in the treatment of non-small cell lung cancer (NSCLC), including lung adenocarcinoma (LUAD), and the primary cause for its clinical inefficacy is chemoresistance. Here, we aimed to investigate a novel mechanism of chemoresistance in LUAD cells, focusing on the calcium-sensing receptor (CaSR). In this study, high CaSR expression was detected in DDP-resistant LUAD cells, and elevated CaSR expression is strongly correlated with poor prognosis in LUAD patients receiving chemotherapy. LUAD cells with high CaSR expression exhibited decreased sensitivity to cisplatin, and the growth of DDP-resistant LUAD cells was inhibited by cisplatin treatment in combination with CaSR suppression, accompanied by changes in BRCA1 and cyclin B1 protein expression both in vitro and in vivo. Additionally, an interaction between CaSR and KIF11 was identified. Importantly, suppressing KIF11 resulted in decreased protein levels of BRCA1 and cyclin B1, enhancing the sensitivity of DDP-resistant LUAD cells to cisplatin with no obvious decrease in CaSR. Here, our findings established the critical role of CaSR in promoting cisplatin resistance in LUAD cells by modulating cyclin B1 and BRCA1 and identified KIF11 as a mediator, highlighting the potential therapeutic value of targeting CaSR to overcome chemoresistance in LUAD.

Cellular and Molecular Mechanisms of Chemoresistance for Gastric Cancer.

Gastric cancer (GC) is one of the most common malignant tumors in the digestive tract, and chemotherapy plays an irreplaceable role in the comprehensive treatment of GC. However, chemoresistance makes it difficult for patients with GC to benefit steadily from chemotherapy in the long term, which ultimately leads to tumor recurrence, metastasis, and patient death. Elucidating the detailed mechanism of chemoresistance in GC and identifying specific therapeutic targets will help to solve the difficult problem of chemoresistance and improve the prognosis of patients with GC. This review summarizes and clarifies the cellular and molecular mechanisms underlying chemoresistance for GC.

NAT10 Mediates XPO1 mRNA N4-acetylation and Promotes Drug Resistance of Myeloma Cells.

The eventually developed chemoresistance to proteasome inhibitors (PIs) is a major hurdle in curing patients with multiple myeloma (MM) and a key cause of poor prognosis, however the underlying molecular mechanisms of chemoresistance is still poorly understood. Herein, we provide evidences that N-acetyltransferase 10 (NAT10), a catalytic enzyme involving in the acetylation modification of RNA, is overexpressed in the BTZ-resistant (BR) MM cell lines and predicts poor outcomes in the clinic. Further manipulating of NAT10 gene expression in MM cells shows that enforced NAT10 expression decreases sensitivity to PI, however knockdown of NAT10 enhances anti-tumor efficacy of PIs in MM cells in vitro and in vivo. Acetylated RNA immunoprecipitation sequencing (acRIP-seq) combined with RIP-qPCR analysis identifies exportin 1 (XPO1) as an important downstream target of NAT10, with promotes N4-acetylcytidine (ac4C) modification of XPO1 mRNA. Importantly, expressions of XPO1 and NAT10 are meaningfully correlated in bone biopsies from the relapsed/refractory (R/R) MM patients, which were also highly associated with poor outcome. Translationally, dual pharmacological inhibition of NAT10 and XPO1 sensitizes MM cells to BTZ treatment in both cell lines and in a xenograft mouse model of MM. Thus, our study elucidates previously unrecognized role of ac4C modification of XPO1 mRNA in the chemoresistance of MM and provides a potential option for clinical management of R/R MM patients in the clinic.

The essential role of glucose metabolism in chemoresistance of colorectal cancer - a mini review

Colorectal cancer (CRC) ranks third in terms of incidence, but second in terms of mortality among all types of cancer globally. Despite emerging advances in cancer remedies, chemotherapy remains the major standard treatment for CRC patients. However, poor prognosis is still a great concern and chemoresistance is detected in 90% of patients with metastatic CRC. Recently, the reprogramming of multiple metabolisms in cancer cells has emerged as an essential effector in tumor growth and drivers of chemoresistance. Understanding the significant mechanisms of chemoresistance would help to find effective solutions to overcome drug resistance and improve the therapeutic efficacy of chemotherapy, thereby prolonging the survival of cancer patients. This review discusses the mechanisms of glucose metabolism reprogramming in the context of CRC chemoresistance and the perspectives of targeting glucose metabolism for the improvement of CRC therapy.