Role In Cancer Resistance Research Articles

LncRNA LINC01664 promotes cancer resistance through facilitating homologous recombination-mediated DNA repair

The intracellular responses to DNA double-strand breaks (DSB) repair are crucial for genomic stability and play an essential role in cancer resistance. In addition to canonical DSB repair proteins, long non-coding RNAs (lncRNAs) have been found to be involved in this sophisticated network. In the present study, we performed a loss-of-function screen for a customized siRNA Premix Library to identify lncRNAs that participate in homologous recombination (HR) process. Among the candidates, we identified LINC01664 as a novel lncRNA required for HR repair. Furthermore, LINC01664 knockdown significantly increased the sensitivity of cancer cells to DNA damage agents such as ionizing radiation and genotoxic drugs. Mechanistically, LINC01664 interacted with Sirt1 promoter and then activated Sirt1 transcription, which contributed to HR-mediated DNA damage repair. In summary, our findings revealed a new mechanism of LINC01664 in DNA damage repair, providing evidence for a potential therapeutic strategy for eliminating the treatment bottlenecks caused by cancer resistance to chemotherapy and radiotherapy.

Exploring potential roles of long non-coding RNAs in cancer immunotherapy: a comprehensive review.

Cancer treatment has long been fraught with challenges, including drug resistance, metastasis, and recurrence, making it one of the most difficult diseases to treat effectively. Traditional therapeutic approaches often fall short due to their inability to target cancer stem cells and the complex genetic and epigenetic landscape of tumors. In recent years, cancer immunotherapy has revolutionized the field, offering new hope and viable alternatives to conventional treatments. A particularly promising area of research focuses on non-coding RNAs (ncRNAs), especially long non-coding RNAs (lncRNAs), and their role in cancer resistance and the modulation of signaling pathways. To address these challenges, we performed a comprehensive review of recent studies on lncRNAs and their impact on cancer immunotherapy. Our review highlights the crucial roles that lncRNAs play in affecting both innate and adaptive immunity, thereby influencing the outcomes of cancer treatments. Key observations from our review indicate that lncRNAs can modify the tumor immune microenvironment, enhance immune cell infiltration, and regulate cytokine production, all of which contribute to tumor growth and resistance to therapies. These insights suggest that lncRNAs could serve as potential targets for precision medicine, opening up new avenues for developing more effective cancer immunotherapies. By compiling recent research on lncRNAs across various cancers, this review aims to shed light on their mechanisms within the tumor immune microenvironment.

Tumor and cancer stem cells‐derived exosomes interplay: A secret of cancer complications

AbstractCancer stem cells (CSCs) are a small subset of tumor cells, efficient in self‐renewal within the tumor and also play a vital role in cancer resistance and metastasis. Recent cancer research has focused on exosomes, a tiny subpopulation of extracellular vesicles (EVs), known for their role in intercellular communication, and significantly contributing to tumor development and metastasis (Tumor derived exosomes‐TEXs). These exosomes complicate cancer treatment by promoting tumor and CSC formation and developing drug and therapeutic resistance. This article explores how tumor‐derived exosomes impact CSC survival, proliferation, and resistance to therapies, leading to tumor recurrence. In a tumor microenvironment (TME), exosomes facilitate tumor growth and metastasis. Targeting exosomes could disrupt CSC communication and improve cancer treatment efficacy. Current studies highlight the role of CSCs exosomes in cancer progression and therapeutic resistance. Understanding CSCs exosome‐based cell‐to‐cell communication in tumor opens a new horizon in cancer therapeutics development.

Predicting circRNA-drug resistance associations based on a multimodal graph representation learning framework.

Circular RNA (circRNA) is a class of noncoding RNA that is highly conserved and exhibit exceptional stability. Due to its function as a microRNA sponge, circRNA has gained significant attention as an essential biomarker and potential drug target in the pathogenesis of several cancers. Although many circRNAs have been identified to play a role in cancer resistance, traditional methods are time-consuming and expensive. In this context, computational methods offer a promising way to facilitate the discovery process. However, most existing prediction models focus on the association between circRNAs and drug resistance, without considering the corresponding disease-related information in the circRNA-drug resistance association. Incorporating disease-related information into the prediction of circRNA-drug resistance associations could potentially improve the efficiency and speed of discovering and developing circRNA-targeting drugs. We propose a computational framework, named GraphCDD, for predicting the association between circRNA and drug resistance. Our model utilizes data from three sources, namely circRNA, disease, and drug, to construct three similarity networks that represent the features of circRNA, disease, and drug, respectively. We utilize a multimodal graph neural network to acquire efficient representations of circRNAs, diseases, and drugs by integrating various types of information, and establish a predictive model. The experimental results have validated the effectiveness of our model and provided a promising method in predicting potential associations between circRNA and drug resistance. The source code and dataset of GraphCDD can be found at https://github.com/Ziqiang-Liu/GraphCDD.

Comparative study on ABCB1-dependent efflux of anthracyclines and their metabolites: consequences for cancer resistance

1. ABCB1 (P-glycoprotein, MDR1) is one of the most important transporter involved in cancer multi-drug resistance. It also plays a significant role in cancer resistance against anthracyclines, an anticancer group of drugs, including doxorubicin and daunorubicin. Several intracellular enzymes metabolise anthracyclines to carbonyl-reduced, hydroxy metabolites, which have impaired cytotoxic properties. However, metabolite efflux by ABCB1 transporter is not well characterised, while it may be the mechanism responsible for the metabolites’ lack of activity. 2. In this study recombinant ABCB1 ATPase transporter assay; anthracyclines accumulation assay in resistant cells overexpressing ABCB1; and molecular modelling were used to investigate anthracyclines: doxorubicin and daunorubicin and their carbonyl-reduced metabolites (doxorubicinol, daunorubicinol) susceptibility for ABCB1-dependent efflux. 3. Based on the kinetics parameters of ATPase activity of ABCB1, it was found that daunorubicinol exerted an exceptionally high potential for being effluxed by the ABCB1 transporter. ABCB1 significantly affected the accumulation pattern of studied chemicals in resistant cancer cells. Doxorubicin and daunorubicinol accumulation were influenced by the activity of ABCB1 modulator – valspodar. 4. Results indicate that ABCB1 activity affects not only anthracyclines but also their metabolites. Therefore crosstalk between the process of anthracyclines metabolism and metabolite efflux may be the mechanism of impairing anticancer properties of anthracyclines metabolites.

Targeting Epidermal Growth Factor Receptor for Cancer Treatment: Abolishing Both Kinase-Dependent and Kinase-Independent Functions of the Receptor.

Epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, is activated by ligand binding, overexpression, or mutation. It is well known for its tyrosine kinase-dependent oncogenic activities in a variety of human cancers. A large number of EGFR inhibitors have been developed for cancer treatment, including monoclonal antibodies, tyrosine kinase inhibitors, and a vaccine. The EGFR inhibitors are aimed at inhibiting the activation or the activity of EGFR tyrosine kinase. However, these agents have shown efficacy in only a few types of cancers. Drug resistance, both intrinsic and acquired, is common even in cancers where the inhibitors have shown efficacy. The drug resistance mechanism is complex and not fully known. The key vulnerability of cancer cells that are resistant to EGFR inhibitors has not been identified. Nevertheless, it has been increasingly recognized in recent years that EGFR also possesses kinase-independent oncogenic functions and that these noncanonical functions may play a crucial role in cancer resistance to EGFR inhibitors. In this review, both kinase-dependent and -independent activities of EGFR are discussed. Also discussed are the mechanisms of actions and therapeutic activities of clinically used EGFR inhibitors and sustained EGFR overexpression and EGFR interaction with other receptor tyrosine kinases to counter the EGFR inhibitors. Moreover, this review discusses emerging experimental therapeutics that have shown potential for overcoming the limitation of the current EGFR inhibitors in preclinical studies. The findings underscore the importance and feasibility of targeting both kinase-dependent and -independent functions of EGFR to enhance therapeutic efficacy and minimize drug resistance. SIGNIFICANCE STATEMENT: EGFR is a major oncogenic driver and therapeutic target, but cancer resistance to current EGFR inhibitors remains a significant unmet clinical problem. This article reviews the cancer biology of EGFR as well as the mechanisms of actions and the therapeutic efficacies of current and emerging EGFR inhibitors. The findings could potentially lead to development of more effective treatments for EGFR-positive cancers.

SRPKs: a promising therapeutic target in cancer.

Cancers such as lung, breast, colon, and prostate have been linked to dysregulation of SRPKs. In preclinical studies, inhibition of SRPKs has been shown to reduce the growth and survival of cancer cells, suggesting that SRPKs may be potential therapeutic targets. Research is ongoing to develop small molecule inhibitors of SRPKs, identify specific SRPKs that are important in different cancer types, and explore the use of RNA interference (RNAi) to target SRPKs. In addition, researchers are examining the potential of using SRPK inhibitors in combination with other cancer therapies, such as chemotherapy or immunotherapy, to improve treatment outcomes. However, more research is needed to fully understand the role of SRPKs in cancer and determine the most effective ways to target them. In the present review, we shed light on the role of SRPKs in most common cancers, its role in cancer resistance, and targeting it for cancer treatment.

Roles of circRNAs in cancer chemoresistance (Review)

Circular RNA (circRNA) is a type of endogenous, high‑stability, noncoding RNA. circRNAs exhibit various biological functions, and are involved in physiological and pathological processes occurring in various diseases, including cancers. They can not only act as microRNA and protein sponges, but also interact with proteins, translated peptides, and transcriptional and translational regulators, and compete with pre‑mRNA splicing. Chemotherapy is one of the most important types of cancer treatment. However, the resistance of cancer cells to chemotherapy is a leading reason for the failure of chemotherapy. It has been reported that circRNAs play important roles in cancer resistance via a number of mechanisms. The functions of the circRNAs provide insight into their roles in chemoresistance pathways. In addition, some circRNAs may serve as novel biomarkers for the diagnosis and prognosis of cancer resistance. Obtaining improved understanding of the molecular regulatory networks featuring circRNAs in tumors and searching for markers for the diagnosis and treatment of cancer resistance are leading issues in circRNA research. The present review introduced the functions of circRNAs, illustrated the mechanisms underlying drug resistance in cancer, described the contributions of circRNAs to this resistance and discussed the potential application of circRNAs in the treatment of drug‑resistant cancer. In particular, the review aimed to reveal the main mechanisms of circRNAs in cancer drug resistance, including mechanisms involving drug transport and metabolism, alterations of drug targets, DNA damage repair, downstream resistance mechanisms, adaptive responses and the tumor microenvironment. The findings may provide novel therapeutic targets for clinical treatment of cancer chemoresistance.

Mitochondrial Dysfunction in Diseases, Longevity, and Treatment Resistance: Tuning Mitochondria Function as a Therapeutic Strategy.

Mitochondria are very important intracellular organelles because they have various functions. They produce ATP, are involved in cell signaling and cell death, and are a major source of reactive oxygen species (ROS). Mitochondria have their own DNA (mtDNA) and mutation of mtDNA or change the mtDNA copy numbers leads to disease, cancer chemo/radioresistance and aging including longevity. In this review, we discuss the mtDNA mutation, mitochondrial disease, longevity, and importance of mitochondrial dysfunction in cancer first. In the later part, we particularly focus on the role in cancer resistance and the mitochondrial condition such as mtDNA copy number, mitochondrial membrane potential, ROS levels, and ATP production. We suggest a therapeutic strategy employing mitochondrial transplantation (mtTP) for treatment-resistant cancer.

The role of exosomes derived miRNAs in cancer.

Exosomes are 20-150nm cell secreting nano-bodies that helps in the transportation of various biomolecules, including micro ribonucleic acid (miRNA) in the human body during both normal and diseased conditions. The current review was planned to summarise the role of miRNA carried by circulatory exosomes in cancer. miRNA is responsible for contribution in cancer, regulation of gene expression, interfering in biological pathways, gene silencing or amplification, and also has a role in cancer resistance. (miRNA) plays a dynamic role in this process by regulating the genes related to drug resistance, cell proliferation, cell cycle and apoptosis through a tissue-specific fashion. Owing to its significances, micro ribonucleic acid has been reported to be the key regulator of cancer, metastasis and also a factor in cancer resistance, and is a better source of possible potential diagnostic biomarkers. Though many studies have explored the biological roles of RNAs in cancer, many facts are needed to be investigated for clinical applications.

A CRISPR Screen Reveals Resistance Mechanisms to CD3-Bispecific Antibody Therapy.

CD3-bispecific antibodies represent an important therapeutic strategy in oncology. These molecules work by redirecting cytotoxic T cells to antigen-bearing tumor cells. Although CD3-bispecific antibodies have been developed for several clinical indications, cases of cancer-derived resistance are an emerging limitation to the more generalized application of these molecules. Here, we devised whole-genome CRISPR screens to identify cancer resistance mechanisms to CD3-bispecific antibodies across multiple targets and cancer types. By validating the screen hits, we found that deficiency in IFNγ signaling has a prominent role in cancer resistance. IFNγ functioned by stimulating the expression of T-cell killing-related molecules in a cell type-specific manner. By assessing resistance to the clinical CD3-bispecific antibody flotetuzumab, we identified core fucosylation as a critical pathway to regulate flotetuzumab binding to the CD123 antigen. Disruption of this pathway resulted in significant resistance to flotetuzumab treatment. Proper fucosylation of CD123 was required for its normal biological functions. In order to treat the resistance associated with fucosylation loss, flotetuzumab in combination with an alternative targeting CD3-bispecific antibody demonstrated superior efficacy. Together, our study reveals multiple mechanisms that can be targeted to enhance the clinical potential of current and future T-cell-engaging CD3-bispecific antibody therapies.

Sialic Acid Metabolic Engineering of Breast Cancer Cells Interferes with Adhesion and Migration

Breast cancer is the most frequent cancer diagnosed in women and the second most common cancer-causing death worldwide. The major problem around the management of breast cancer is its high heterogeneity and the development of therapeutic resistance. Therefore, understanding the fundamental breast cancer biology is crucial for better diagnosis and therapy. Protein sialylation is a key posttranslational modification of glycoproteins, which is also involved in tumor progression and metastasis. Increased expression of sialic acids (Sia) can interfere in receptor–ligand interactions and might protect tumor cells from the immune system. Furthermore, Sia content on the cell membrane plays a role in cancer resistance towards chemo- and radiation therapy. In this study, we glycoengineered MCF-7 breast cancer cells using a series of non-natural Sia precursors, which are prolonged in their acyl side chain. We observed a significant reduction in the natural Sia (N-Acetylneuraminic acid) expression after cultivation of MCF-7 cells with these Sia precursors. In addition, the expression of polySia, a unique glycosylation of the neural cell adhesion molecule NCAM, which interferes with cell adhesion, was decreased. We conclude that sialic acid engineering i) opens up novel opportunities to study the biological role of Sia in breast cancer and ii) provides a toolbox to examine the sialic acid-dependent complex cellular alterations in breast cancer cell biology.

Abstract C109: Modulation of HDAC activity in subtypes of triple-negative breast cancer: Effects of vorinostat on HDAC 7 expression and cancer stem cells progression

Abstract Epigenetic drugs, such as histone deacetylase inhibitors (HDACi), are continuing to emerge as promising therapies for various cancers. These drugs, including FDA-approved vorinostat, are capable of multiple actions and considered to be multifunctional. Histone deacetylases (HDAC) are chromatin-modifying enzymes that are involved in various cellular events, such as tissue differentiation, autophagy, apoptosis, migration, mitosis and angiogenesis. High levels of HDACs have been detected in several cancers. Early studies in our laboratory showed different effects by vorinostat on global HDAC activity in several triple-negative breast cancer (TNBC) subtypes. This study focused on HDAC 7, which has been associated with increases in cancer stem cells and poor prognosis. Cancer stem cells play an important role in cancer resistance to therapy. Histone deacetylase inhibitors are emerging as therapy for triple-negative breast cancer, which is currently an unmet need in women's health due to the lack of targeted therapies. This study investigated the effects of vorinostat on apoptosis and the modulation of HDAC 7 expression in two subtypes of triple-negative breast cancers, MB231(MSL) and HCC70 (BL-2). Using caspase 3/7 assays vorinostat induced apoptosis. Additionally, flow cytometry and immunostaining were conducted to determine vorinostat's effects on expression of two cancer stem cell (CSC) markers, CD44 and CD24. Western blot and real-time PCR showed a significant decrease (10-fold) in the expression of HDAC 7 by vorinostat in HCC70 cells. A modest decrease (3-fold) was also observed in MB231 cells. CD44 expression was deceased by vorinostat in MB231 cells. This study demonstrated that vorinostat exerts its anticancer effects through several mechanisms, such as inducing apoptosis, downregulating HDAC 7 and decreasing cancer stem cells. This therapy could be beneficial for subtypes of TNBC, such as HCC70, an aggressive basal-like 2 cell line from an African American. Citation Format: Fatemeh Nouri Emamzadeh, Anfernee Hawkins, Gustavo Miranda-Carboni, Rhonda Moore, Beverly Word, Beverly Lyn-Cook. Modulation of HDAC activity in subtypes of triple-negative breast cancer: Effects of vorinostat on HDAC 7 expression and cancer stem cells progression [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C109.

LncRNA MST1P2/miR-133b axis affects the chemoresistance of bladder cancer to cisplatin-based therapy via Sirt1/p53 signaling.

Although bladder cancer is commonly chemosensitive to standard first-line therapy, the acquisition of the resistance to cisplatin (DDP)-based therapeutic regimens remains a huge challenge. Noncoding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs) and microRNAs, have been reported to play a critical role in cancer resistance to DDP. Here, we attempted to provide a novel mechanism by which the resistance of bladder cancer to DDP treatment could be modulated from the perspective of ncRNA regulation. We demonstrated that lncRNA MST1P2 (lnc-MST1P2) expression was dramatically upregulated, whereas miR-133b expression was downregulated in DDP-resistant bladder cancer cell lines, SW 780/DDP and RT4/DDP. Lnc-MST1P2 and miR-133b negatively regulated each other via targeting miR-133b. Both lnc-MST1P2 silence and miR-133b overexpression could resensitize DDP-resistant bladder cancer cells to DDP treatment. More important, miR-133b could directly target the Sirt1 3'-untranslated region to inhibit its expression. Inc-MST1P2/miR-133b axis affected the resistance of bladder cancer cells to DDP via Sirt1/p53 signaling. In conclusion, MST1P2 serves as a competing endogenous RNA for miR-133b to counteract miR-133b-induced suppression on Sirt1, therefore enhancing the resistance of bladder cancer cells to DDP. MST1P2/miR-133b axis affects the resistance of bladder cancer cells to DDP via downstream Sirt1/p53 signaling.

Aldo-keto reductase 1C3 (AKR1C3): a missing piece of the puzzle in the dinaciclib interaction profile

Dinaciclib is a multi-specific cyclin-dependent kinase (CDK) inhibitor with significant preclinical and clinical activity. It inhibits CDK1, CDK2, CDK5, CDK9 and CDK12 in the nanomolar range and exhibits potent antiproliferative effects on various cancers in vitro and in vivo. Aldo-keto reductases (AKR) and carbonyl reductases (CBR) are enzymes involved at the biosynthesis, intermediary metabolism and detoxification processes, but can also play a significant role in cancer resistance. Here, we report that dinaciclib is a strong inhibitor of aldo-keto reductase 1C3 (AKR1C3), an enzyme that is known to be an important regulator of cell proliferation and differentiation. AKR1C3 is overexpressed in a range of cancer types and is also involved in tumour cell resistance to anthracyclines. In our study, dinaciclib displayed tight-binding inhibition of human recombinant AKR1C3 (Kiapp = 0.07µM) and was also active at the cellular level (IC50 = 0.23µM). Dinaciclib acts as a noncompetitive inhibitor with respect to daunorubicin and as an uncompetitive inhibitor with respect to the NADPH. In subsequent experiments, pretreatment with dinaciclib (0.1µM) significantly sensitized AKR1C3-overexpressing anthracycline-resistant cancer cells to daunorubicin. In conclusion, our results indicate that dinaciclib may potentially increase the therapeutic efficacy and safety of anthracyclines by preventing anthracycline resistance and minimizing their adverse effects.

Drug metabolizing enzymes and their inhibitors' role in cancer resistance.

Despite continuous research on chemotherapeutic agents, different mechanisms of resistance have become a major pitfall in cancer chemotherapy. Although, exhaustive efforts are being made by several researchers to target resistance against chemotherapeutic agents, there is another class of resistance mechanism which is almost carrying on unattended. This class of resistance includes pharmacokinetics resistance such as efflux by ABC transporters and drug metabolizing enzymes. ABC transporters are the membrane bound proteins which are responsible for the movement of substrates through the cell membrane. Drug metabolizing enzymes are an integral part of phase-II metabolism that helps in the detoxification of exogenous, endogenous and xenobiotics substrates. These include uridine diphospho-glucuronosyltransferases (UGTs), glutathione-S-transferases (GSTs), dihydropyrimidine dehydrogenases (DPDs) and thiopurine methyltransferases (TPMTs). These enzymes may affect the role of drugs in both positive as well negative manner, depending upon the type of tissue and cells present and when present in tumors, can result in drug resistance. However, the underlying mechanism of resistance by drug metabolizing enzymes is still not clear. Here, we have tried to cover various aspects of these enzymes in relation to anticancer drugs.

Insights into long noncoding RNAs of naked mole rat (Heterocephalus glaber) and their potential association with cancer resistance.

BackgroundLong noncoding RNAs (lncRNAs) are a class of ubiquitous noncoding RNAs and have been found to act as tumor suppressors or oncogenes, which dramatically altered our understanding of cancer. Naked mole rat (NMR, Heterocephalus glaber) is an exceptionally long-lived and cancer-resistant rodent; however, whether lncRNAs play roles in cancer resistance in this seductive species remains unknown.ResultsIn this study, we developed a pipeline and identified a total of 4422 lncRNAs across the NMR genome based on 12 published transcriptomes. Systematic analysis revealed that NMR lncRNAs share many common characteristics with other vertebrate species, such as tissue specificity and low expression. BLASTN against with 1057 human cancer-related lncRNAs showed that only 5 NMR lncRNAs displayed homology, demonstrating the low sequence conservation between NMR lncRNAs and human cancer-related lncRNAs. Further correlation analysis of lncRNAs and protein-coding genes indicated that a total of 1295 lncRNAs were intensively coexpressed (r ≥ 0.9 or r ≤ −0.9, cP value ≤ 0.01) with potential tumor-suppressor genes in NMR, and 194 lncRNAs exhibited strong correlation (r ≥ 0.8 or r ≤ −0.8, cP value ≤ 0.01) with four high-molecular-mass hyaluronan related genes that were previously identified to play key roles in cancer resistance of NMR.ConclusionIn this study, we provide the first comprehensive genome-wide analysis of NMR lncRNAs and their possible associations with cancer resistance. Our results suggest that lncRNAs may have important effects on anticancer mechanism in NMR.Electronic supplementary materialThe online version of this article (doi:10.1186/s13072-016-0101-5) contains supplementary material, which is available to authorized users.

Abstract 2216: Study of PDL-1 regulation and expression in glioblastoma and its role in cancer resistance

Abstract Among the high-grade malignant gliomas (III-IV), grade IV glioma, or glioblastoma (GBM), is the most common and destructive form of brain cancer. Despite rigorous molecular, preclinical, and clinical research these tumors remain a challenge to treat and 70% of patients diagnosed with GBM will succumb to the disease within 2 years. New immune-based cancer treatments are currently in development, among which, anti-PD-1 is in a phase II clinical trial for recurrent glioblastoma. Tumor cells exploit PDL-1/PD1 pathway to induce T cell exhaustion and evade host antitumour immunity. PDL-1 expression on glioblastoma has been shown to correlate with a bad prognosis. There is strong demand for knowledge about the mechanisms regulating PDL-1 expression in glioblastoma. Our research group, has previously identified a relevant role for FKBP51, and its spliced isoform FKBP51s, in PDL-1 expression and melanoma resistance to the therapy. FKBP51 is an immunophilin capable of immunosuppression, originally cloned in lymphocytes. Because FKBP51 was identified as highly expressed in glioblastoma, correlating with tumor aggressiveness, we investigated whether this protein and/or its spliced isoform FKBP51s could be involved in regulation of PDL-1 expression in glioblastoma. In addition, we looked at the role of these protein-isoforms in glioblastoma resistance to chemotherapy. To this aim, we used two different glioblastoma cell lines termed D54 and U251. Our results suggest that, differently from melanoma, in which PDL-1 is inducible and associated with FKBP51 splicing, glioblastoma cell lines express high basal levels of PDL-1. Interestingly, both the canonical and the spliced FKBP51 isoforms were highly expressed in the glioblastoma cell lines. Expression of PDL-1 was regulated by FKBP51s knockin and knockout and the levels changed in accordance with FKBP51s levels. Moreover, in glioblastoma cells silenced for FKBP51s, the decrease in PDL-1 levels was associated with a significant increase in apoptosis, either spontaneous apoptosis and the one stimulated by etoposide or temozolomide. Two recently developed compounds, selective inhibitor of FKBP51, termed SAFit1 and SAFit2 were able to reduce expression of PDL-1 on glioblastoma cell lines. Particularly, SAFit 2 was found to be more effective, in accordance with the notion that it is more brain-permeable than SAFit1. SaFit 2 was also shown to increase sensitivity to etoposide of glioblastoma cell, although to a lesser extent when compared to FKBP51siRNAs. In conclusion, our preliminary results suggest that FKBP51s plays a relevant role in glioblastoma resistance and PDL-1 expression. Future studies are needed to shed light on the mechanisms underlying FKBP51s-induced PDL-1 expression and signaling pathway downstream to FKBP51s/PDL-1 that sustain glioblastoma resistance. Citation Format: Michele Russo, Paolo D’Arrigo, Felix Hausch, Anna Rea, Martina Tufano, Maria Fiammetta Romano, Simona Romano. Study of PDL-1 regulation and expression in glioblastoma and its role in cancer resistance. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2216.

Abstract LB-042: MCPIP1 suppresses breast tumor progression by targeting anti-apoptosis pathway

Abstract The ability to evade apoptosis is a hallmark of cancer and also plays a significant role in cancer resistance to conventional therapy. While recent progress has broadened our understanding of the apoptosis-evasion mechanisms by cancer cells, how apoptosis resistance develops in cancer cells through posttranscriptional mechanisms, especially by the newly discovered RNA-binding protein monocyte chemotactic protein induced protein 1 (MCPIP1), remains unknown. Here, we report that MCPIP1 expression is impaired in breast tumors and breast tumor cell lines, with the severest impairment in highly metastatic tumors. Ectopic expression of MCPIP1 causes apoptosis of breast tumor cells through selectively suppression of anti-apoptotic gene transcripts, including Bcl2L1, Bcl2A1, RelB, Birc3 and Bcl3. This suppression is medicated through a physical interaction between the PIN domain of MCPIP1 and the 3′UTRs of anti-apoptotic transcripts, resulting in mRNA degradation and tumor cell apoptosis. In difference from the RNA-binding protein tristetraprolin which binds to the ARE in the 3′UTR of target genes for mRNA decay, MCPIP1 specially recognizes a stem-loop structure in the 3′UTR of anti-apoptotic genes for binding and mRNA decay. Furthermore, induction of MCPIP not only ameliorates breast tumor formation but also completely shrinks the established tumors within six days. Lung metastasis is also significantly reduced by MCPIP1 induction. The tumor suppressive effect of MCPIP1 acts through activation of apoptosis. Importantly, by analysis of the excised breast tumors of 251 patients, we found that low MCPIP1 levels in tumors are strongly associated with poor survival of patients over 13 years of follow up. Taken together, we demonstrate that MCPIP1 is a novel potent tumor suppressor which induces tumor apoptosis through tipping the balance between pro-apoptotic and anti-apoptotic genes via selectively targeting the mRNAs of anti-apoptotic genes for degradation. MCPIP1 can serve as a new therapeutic target for treatment of breast cancer and other cancers as well. Citation Format: Jianguo Liu, Wenbao Lu, Huan Ning, Hui Peng, Qinghong Wang, Rong Hou. MCPIP1 suppresses breast tumor progression by targeting anti-apoptosis pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-042. doi:10.1158/1538-7445.AM2015-LB-042

Expression and role of PGP, BCRP, MRP1 and MRP3 in multidrug resistance of canine mammary cancer cells

BackgroundIn both women and female dogs, the most prevalent type of malignant neoplasm is the spontaneous mammary tumor. In dogs, half of these are malignant. The treatment of choice for the canine patients is surgical mastectomy. Unfortunately, it often fails in high-risk, locally invasive mammary tumors as of during the time of the surgery the micro-metastases are present. Moreover, there are neither large studies conducting to prove of the benefit from the chemotherapy in dogs nor established chemotherapy treatment protocols available. Additionally, the effectiveness of each individual chemotherapeutic agent and drug resistance of canine mammary cancer have not yet been characterized. That has become the aim of our study, to assess the expression of PGP, BCRP, MRP1 and MRP3 in canine mammary cancer cell lines and to investigate their role in cancer resistance to vinblastine, cisplatin and cyclophosphamide with using RNAi approach.ResultsThe results suggested that in canine mammary cancer, the vinblastine efflux was mediated by PGP and MRP1 proteins, cisplatin efflux was mediated by all four examined efflux pumps (PGP, BCRP, MRP1 and MRP3), whereas cyclophosphamide resistance was related to BCRP activity. RNAi silencing of these efflux pumps significantly decreased IC50 doses of the examined drugs in canine mammary carcinoma cells.ConclusionsOur results have indicated the treatment of cells involving use of the siRNA targeting efflux pumps could be a beneficial approach in the future.