APC loss affects DNA damage repair causing doxorubicin resistance in breast cancer cells

Drug resistance mechanisms in cancers: Execution of pro-survival strategies

One of the quintessential challenges in cancer treatment is drug resistance. Several mechanisms of drug resistance have been described to date, and new modes of drug resistance continue to be discovered. The phenomenon of cancer drug resistance is now widespread, with approximately 90% of cancer-related deaths associated with drug resistance. Despite significant advances in the drug discovery process, the emergence of innate and acquired mechanisms of drug resistance has impeded the progress in cancer therapy. Therefore, understanding the mechanisms of drug resistance and the various pathways involved is integral to treatment modalities. In the present review, I discuss the different mechanisms of drug resistance in cancer cells, including DNA damage repair, epithelial to mesenchymal transition, inhibition of cell death, alteration of drug targets, inactivation of drugs, deregulation of cellular energetics, immune evasion, tumor-promoting inflammation, genome instability, and other contributing epigenetic factors. Furthermore, I highlight available treatment options and conclude with future directions.

DNA-PKcs-mediated transcriptional regulation of TOP2B drives chemoresistance in acute myeloid leukemia

Anthracyclines, topoisomerase II enzyme poisons that cause DNA damage, are the mainstay of acute myeloid leukemia (AML) treatment. However, acquired resistance to anthracyclines leads to relapse, which currently lacks effective treatment and is the cause of poor survival in individuals with AML. Therefore, the identification of the mechanisms underlying anthracycline resistance remains an unmet clinical need. Here, using patient-derived primary cultures and clinically relevant cellular models that recapitulate acquired anthracycline resistance in AML, we have found that GCN5 (also known as KAT2A) mediates transcriptional upregulation of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in AML relapse, independently of the DNA-damage response. We demonstrate that anthracyclines fail to induce DNA damage in resistant cells, owing to the loss of expression of their target enzyme, TOP2B; this was caused by DNA-PKcs directly binding to its promoter upstream region as a transcriptional repressor. Importantly, DNA-PKcs kinase activity inhibition re-sensitized AML relapse primary cultures and cells resistant to mitoxantrone, and abrogated their tumorigenic potential in a xenograft mouse model. Taken together, our findings identify a GCN5-DNA-PKcs-TOP2B transcriptional regulatory axis as the mechanism underlying anthracycline resistance, and demonstrate the therapeutic potential of DNA-PKcs inhibition to re-sensitize resistant AML relapse cells to anthracycline.

Establishing the role of BRCA1 in the diagnosis, prognosis and immune infiltrates of breast invasive cancer by bioinformatics analysis and experimental validation

BACKGROUND

Breast cancer susceptibility gene 1 (BRCA1) is a well-known gene that acts a vital role in suppressing the growth of tumors. Previous studies have primarily focused on the genetic mutations of BRCA1 and its association with hereditary breast invasive carcinoma (BRCA). However, little research has been done to investigate the relationship between BRCA1 and immune infiltrates and prognosis in BRCA.

METHODS

We obtained the expression profiles and clinical information of patients with BRCA from the Cancer Genome Atlas (TCGA) database. The levels of the BRCA1 gene between BRCA tissues and normal breast tissues were compared through the Wilcoxon rank-sum test. Additionally, we performed WB and RT-qPCR techniques to detect the expression of BRCA1. We conducted functional enrichment analyses. Furthermore, we assessed immune cell infiltration using a single-sample gene set enrichment analysis. The methylation status of the BRCA1 gene was analyzed using the UALCAN and MethSurv databases. The Cox regression analysis and (KM) Kaplan-Meier method were employed to determine the prognostic value of BRCA1. In order to provide a practical tool for predicting the overall survival rates at different time points, we also constructed a nomogram.

RESULTS

Our analysis revealed that the expression of BRCA1 was significantly higher in BRCA tissues compared to normal tissues. Furthermore, this increased level of BRCA1 was found to be associated with specific BRCA subtypes, including T2, stage II, ER positive, ect. Importantly, the overexpression of BRCA1 was shown to be a negative prognostic marker for the overall survival rates of BRCA patients. Moreover, low methylation status of the BRCA1 gene was related to a poorer prognosis. Furthermore, our results indicated that high levels of BRCA1 are related to a decrease in level of killer immune cells, such as natural killer (NK) cells, macrophages, CD8+ T cells, and plasma-like dendritic cells (pDCs) within the tumor microenvironment.

CONCLUSIONS

Our study is the first to provide evidence indicating that the presence of BRCA1 can serve as a reliable marker for both diagnosing and determining the prognosis of BRCA. Moreover, BRCA1 acts as a crucial indicator of the cancer's potential to infiltrate and invade the immune system, which has important implications for developing targeted therapies in BRCA.

Targeted Hyperbranched Nanoparticles for Delivery of Doxorubicin in Breast Cancer Brain Metastasis

Breast cancer brain metastases (BM) are associated with a dismal prognosis and very limited treatment options. Standard chemotherapy is challenging in BM patients because the high dosage required for an effective outcome causes unacceptable systemic toxicities, a consequence of poor brain penetration, and a short physiological half-life. Nanomedicines have the potential to circumvent off-target toxicities and factors limiting the efficacy of conventional chemotherapy. The HER3 receptor is commonly expressed in breast cancer BM. Here, we investigate the use of hyperbranched polymers (HBP) functionalized with a HER3 bispecific-antibody fragment for cancer cell-specific targeting and pH-responsive release of doxorubicin (DOX) to selectively deliver and treat BM. We demonstrated that DOX-release from the HBP carrier was controlled, gradual, and greater in endosomal acidic conditions (pH 5.5) relative to physiologic pH (pH 7.4). We showed that the HER3-targeted HBP with DOX payload was HER3-specific and induced cytotoxicity in BT474 breast cancer cells (IC50: 17.6 μg/mL). Therapeutic testing in a BM mouse model showed that HER3-targeted HBP with DOX payload impacted tumor proliferation, reduced tumor size, and prolonged overall survival. HER3-targeted HBP level detected in ex vivo brain samples was 14-fold more than untargeted-HBP. The HBP treatments were well tolerated, with less cardiac and oocyte toxicity compared to free DOX. Taken together, our HER3-targeted HBP nanomedicine has the potential to deliver chemotherapy to BM while reducing chemotherapy-associated toxicities.

Phosphorylated Hsp27 promotes adriamycin resistance in breast cancer cells through regulating dual phosphorylation of c-Myc

Chemotherapy resistance of breast cancer cells is one of the major factors affecting patient survival rate. Heat shock protein 27 (Hsp27) is a member of the small heat shock protein family that has been reported to be associated with chemotherapy resistance in tumor cells, but the exact mechanism is not fully understood. Here, we explored the regulation of Hsp27 in adriamycin-resistant pathological conditions of breast cancer in vitro and in vivo. We found that overexpression of Hsp27 in MCF-7 breast cancer cells reversed DNA damage induced by adriamycin, and thereby reduced subsequent cell apoptosis. Non-phosphorylated Hsp27 accelerated ubiquitin-mediated degradation of c-Myc under normal physiological conditions. After stimulation with adriamycin, Hsp27 was phosphorylated and translocated from the cytoplasm into the nucleus, where phosphorylated Hsp27 upregulated c-Myc and Nijmegen breakage syndrome 1 (NBS1) protein levels thus leading to ATM activation. We further showed that phosphorylated Hsp27 promoted c-Myc nuclear import and stabilization by regulating T58/S62 phosphorylation of c-Myc through a protein phosphatase 2A (PP2A)-dependent mechanism. Collectively, the data presented in this study demonstrate that Hsp27, in its phosphorylation state, plays a critical role in adriamycin-resistant pathological conditions of breast cancer cells.

In Doxorubicin-Adapted Hodgkin Lymphoma Cells, Acquiring Multidrug Resistance and Improved Immunosuppressive Abilities, Doxorubicin Activity Was Enhanced by Chloroquine and GW4869

Classical Hodgkin lymphoma (cHL) is a highly curable disease (70-80%), even though long-term toxicities, drug resistance, and predicting clinical responses to therapy are major challenges in cHL treatment. To solve these problems, we characterized two cHL cell lines with acquired resistance to doxorubicin, KM-H2dx and HDLM-2dx (HRSdx), generated from KM-H2 and HDLM-2 cells, respectively. HRSdx cells developed cross-resistance to vinblastine, bendamustin, cisplatin, dacarbazine, gemcitabine, brentuximab vedotin (BV), and γ-radiation. Both HDLM-2 and HDLM-2dx cells had intrinsic resistance to BV but not to the drug MMAE. HDLM-2dx acquired cross-resistance to caelyx. HRSdx cells had in common decreased CD71, CD80, CD54, cyt-ROS, HLA-DR, DDR1, and CD44; increased Bcl-2, CD58, COX2, CD26, CCR5, and invasive capability; increased CCL5, TARC, PGE2, and TGF-β; and the capability of hijacking monocytes. In HRSdx cells less sensitive to DNA damage and oxidative stress, the efflux drug transporters MDR1 and MRP1 were not up-regulated, and doxorubicin accumulated in the cytoplasm rather than in the nucleus. Both the autophagy inhibitor chloroquine and extracellular vesicle (EV) release inhibitor GW4869 enhanced doxorubicin activity and counteracted doxorubicin resistance. In conclusion, this study identifies common modulated antigens in HRSdx cells, the associated cross-resistance patterns, and new potential therapeutic options to enhance doxorubicin activity and overcome resistance.

CL4-modified exosomes deliver lncRNA DARS-AS1 siRNA to suppress triple-negative breast cancer progression and attenuate doxorubicin resistance by inhibiting autophagy

Triple-negative breast cancer (TNBC) is a fatal disease. Drug resistance and the lack of effective drugs are the leading causes of death in patients with TNBC. Recently, long non-coding RNAs have been proven to be effective drug design targets owing to their high tissue specificity; however, an effective drug delivery system is necessary for their clinical application. In this study, we constructed a novel nanodrug delivery system based on the epidermal growth factor receptor (EGFR)-targeted aptamer CL4-modified exosomes (EXOs-CL4) for the targeted delivery of aspartyl-tRNA synthetase-antisense RNA 1 (DARS-AS1) small interfering RNA (siRNA) and doxorubicin (DOX) to TNBC cells in vitro and in vivo. This delivery system exerted potent anti-proliferation, anti-migration, and pro-apoptotic effects on TNBC cells. Silencing DARS-AS1 increased the sensitivity of TNBC cells to DOX by suppressing the transforming growth factor-β (TGF-β)/Smad3 signaling pathway-induced autophagy, thereby enhancing the synergetic antitumor effects. Collectively, our findings revealed that EXOs-CL4-mediated delivery of DARS-AS1 siRNA can be used as a new treatment strategy for DOX-resistant TNBC. Moreover, EXOs-CL4 can be used as effective drug delivery systems for targeted TNBC therapy.

Doxorubicin and other anthracyclines in cancers: Activity, chemoresistance and its overcoming

Anthracyclines have been important and effective treatments against a number of cancers since their discovery. However, their use in therapy has been complicated by severe side effects and toxicity that occur during or after treatment, including cardiotoxicity. The mode of action of anthracyclines is complex, with several mechanisms proposed. It is possible that their high toxicity is due to the large set of processes involved in anthracycline action. The development of resistance is a major barrier to successful treatment when using anthracyclines. This resistance is based on a series of mechanisms that have been studied and addressed in recent years. This work provides an overview of the anthracyclines used in cancer therapy. It discusses their mechanisms of activity, toxicity, and chemoresistance, as well as the approaches used to improve their activity, decrease their toxicity, and overcome resistance.

Combined doxorubicin and arctigenin treatment induce cell cycle arrest-associated cell death by promoting doxorubicin uptake in doxorubicin-resistant breast cancer cells

Chemotherapy failure is often caused by drug resistance, for which no effective treatment strategy has been established. Many studies have been undertaken with the aim of overcoming drug resistance using natural products. Arctigenin (ATG), a natural product, has been investigated for its anti-cancer effects in HER2-overexpressing, ER-positive, and triple-negative breast cancer cells. We investigated the efficacy of ATG against self-established doxorubicin (DOX)-resistant breast cancer cells (MCF-DR and MDA-DR cells) derived from MCF-7 and MDA-MB-231 cells, respectively. ATG was found to increase DOX intracellular levels by downregulating multidrug Resistance 1 (MDR1) mRNA expression in DOX-resistant cells. In addition, combined treatment with DOX and ATG (DOX/ATG) reduced the viability of and colony formation by DOX-resistant cells. DOX/ATG also significantly induced G2/M cell cycle arrest by suppressing the Cyclin D1/CDK4/RB pathways and suppressed the expressions of MDR1 and Cyclin D1 by inhibiting the Mitogen-activated protein kinase (MAPK)/Activating protein-1 (AP-1) signaling pathways. Furthermore, DOX/ATG induced DNA damage and attenuated the expressions of RAD51 and Ku80. However, PARP1 (Poly [ADP-ribose] polymerase1) cleavage and AIF (Apoptosis-inducing factor) induced apoptosis did not occur despite DNA damage-induced cell death. Rather, flow cytometry showed that DOX/ATG caused necrosis. In summary, DOX/ATG increased intracellular DOX levels by inhibiting MDR1 and inducing G2/M arrest by inhibiting the Cyclin D1/CDK4/RB pathways and causing necrosis by damaging DNA. Our results suggest that ATG might be used as an adjuvant to enhance the efficacy of DOX in DOX-resistant breast cancer.

Crosstalk between Wnt/β-catenin signaling pathway and DNA damage response in cancer: a new direction for overcoming therapy resistance

Wnt signaling plays an important role in regulating the biological behavior of cancers, and many drugs targeting this signaling have been developed. Recently, a series of research have revealed that Wnt signaling could regulate DNA damage response (DDR) which is crucial for maintaining the genomic integrity in cells and closely related to cancer genome instability. Many drugs have been developed to target DNA damage response in cancers. Notably, different components of the Wnt and DDR pathways are involved in crosstalk, forming a complex regulatory network and providing new opportunities for cancer therapy. Here, we provide a brief overview of Wnt signaling and DDR in the field of cancer research and review the interactions between these two pathways. Finally, we also discuss the possibility of therapeutic agents targeting Wnt and DDR as potential cancer treatment strategies.

Medical Needs and Therapeutic Options for Melanoma Patients Resistant to Anti-PD-1-Directed Immune Checkpoint Inhibition

Available 4- and 5-year updates for progression-free and for overall survival demonstrate a lasting clinical benefit for melanoma patients receiving anti-PD-directed immune checkpoint inhibitor therapy. However, at least one-half of the patients either do not respond to therapy or relapse early or late following the initial response to therapy. Little is known about the reasons for primary and/or secondary resistance to immunotherapy and the patterns of relapse. This review, prepared by an interdisciplinary expert panel, describes the assessment of the response and classification of resistance to PD-1 therapy, briefly summarizes the potential mechanisms of resistance, and analyzes the medical needs of and therapeutic options for melanoma patients resistant to immune checkpoint inhibitors. We appraised clinical data from trials in the metastatic, adjuvant and neo-adjuvant settings to tabulate frequencies of resistance. For these three settings, the role of predictive biomarkers for resistance is critically discussed, as well as are multimodal therapeutic options or novel immunotherapeutic approaches which may help patients overcome resistance to immune checkpoint therapy. The lack of suitable biomarkers and the currently modest outcomes of novel therapeutic regimens for overcoming resistance, most of them with a PD-1 backbone, support our recommendation to include as many patients as possible in novel or ongoing clinical trials.

p53-Dependent Cytoprotective Mechanisms behind Resistance to Chemo-Radiotherapeutic Agents Used in Cancer Treatment

Resistance to chemoradiotherapy is the main cause of cancer treatment failure. Cancer cells, especially cancer stem cells, utilize innate cytoprotective mechanisms to protect themselves from the adverse effects of chemoradiotherapy. Here, we describe a few such mechanisms: DNA damage response (DDR), immediate early response gene 5 (IER5)/heat-shock factor 1 (HSF1) pathway, and p21/nuclear factor erythroid 2-related factor 2 (NRF2) pathway, which are regulated by the tumour suppressor p53. Upon DNA damage caused during chemoradiotherapy, p53 is recruited to the sites of DNA damage and activates various DNA repair enzymes including GADD45A, p53R2, DDB2 to repair damaged-DNA in cancer cells. In addition, the p53-IER5-HSF1 pathway protects cancer cells from proteomic stress and maintains cellular proteostasis. Further, the p53-p21-NRF2 pathway induces production of antioxidants and multidrug resistance-associated proteins to protect cancer cells from therapy-induced oxidative stress and to promote effusion of drugs from the cells. This review summarises possible roles of these p53-regulated cytoprotective mechanisms in the resistance to chemoradiotherapy.

DNA repair pathways in breast cancer: from mechanisms to clinical applications

BACKGROUND

Breast cancer (BC) is a complex disease with various subtypes and genetic alterations that impact DNA repair pathways. Understanding these pathways is essential for developing effective treatments and improving patient outcomes.

AREA COVERED

This study investigates the significance of DNA repair pathways in breast cancer, specifically focusing on various pathways such as nucleotide excision repair, base excision repair, mismatch repair, homologous recombination repair, non-homologous end joining, fanconi anemia pathway, translesion synthesis, direct repair, and DNA damage tolerance. The study also examines the role of these pathways in breast cancer resistance and explores their potential as targets for cancer treatment.

CONCLUSION

Recent advances in targeted therapies have shown promise in exploiting DNA repair pathways for BC treatment. However, much research is needed to improve the efficacy of these therapies and identify new targets. Additionally, personalized treatments that target specific DNA repair pathways based on tumor subtype or genetic profile are being developed. Advances in genomics and imaging technologies can potentially improve patient stratification and identify biomarkers of treatment response. However, many challenges remain, including toxicity, resistance, and the need for more personalized treatments. Continued research and development in this field could significantly improve BC treatment.

Germline variants of uncertain significance, their frequency, and clinico-pathological features in a cohort of Sri Lankan patients with hereditary breast cancer

BACKGROUND

Next-Generation Sequencing (NGS)-based testing in cancer patients has led to increased detection of variants of uncertain significance (VUS). VUS are genetic variants whose impact on protein function is unknown. VUS pose a challenge to clinicians and patients due to uncertainty regarding their cancer predisposition risk. Paucity of data exists on the pattern of VUS in under-represented populations. This study describes the frequency of germline VUS and clinico-pathological features in Sri Lankan hereditary breast cancer patients.

METHODS

Data of 72 hereditary breast cancer patients who underwent NGS-based testing between January 2015 and December 2021 were maintained prospectively in a database and analyzed retrospectively. Data were subjected to bioinformatics analysis and variants were classified according to international guidelines.

RESULTS

Germline variants were detected in 33/72(45.8%) patients, comprising 16(48.5%) pathogenic/likely pathogenic variants and 17(51.5%) VUS. Distribution of VUS in breast cancer predisposing genes were :APC:1(5.8%), ATM:2(11.7%), BRCA1:1(5.8%), BRCA2:5(29.4%), BRIP1:1(5.8%), CDKN2A:1(5.8%), CHEK2:2(11.7%), FANC1:1(5.8%), MET:1(5.8%), STK11:1(5.8%), NF2:1(5.8%). Mean age at cancer diagnosis in patients with VUS was 51.2 years. Most common tumour histopathology was ductal carcinoma 11(78.6%). 50% of tumours in patients having VUS in BRCA1/2 genes were hormone receptor negative. 73.3% patients had family history of breast cancer.

CONCLUSIONS

A significant portion of patients had a germline VUS. Highest frequency was in BRCA2 gene. Majority had family history of breast cancer. This highlights the need to undertake functional genomic studies to determine the biological effects of VUS and identify potentially clinically actionable variants that would be useful for decision-making and patient management.

Exploring the ATR-CHK1 pathway in the response of doxorubicin-induced DNA damages in acute lymphoblastic leukemia cells

Doxorubicin (Dox) is one of the most commonly used anthracyclines for the treatment of solid and hematological tumors such as B-/T cell acute lymphoblastic leukemia (ALL). Dox compromises topoisomerase II enzyme functionality, thus inducing structural damages during DNA replication and causes direct damages intercalating into DNA double helix. Eukaryotic cells respond to DNA damages by activating the ATM-CHK2 and/or ATR-CHK1 pathway, whose function is to regulate cell cycle progression, to promote damage repair, and to control apoptosis. We evaluated the efficacy of a new drug schedule combining Dox and specific ATR (VE-821) or CHK1 (prexasertib, PX) inhibitors in the treatment of human B-/T cell precursor ALL cell lines and primary ALL leukemic cells. We found that ALL cell lines respond to Dox activating the G2/M cell cycle checkpoint. Exposure of Dox-pretreated ALL cell lines to VE-821 or PX enhanced Dox cytotoxic effect. This phenomenon was associated with the abrogation of the G2/M cell cycle checkpoint with changes in the expression pCDK1 and cyclin B1, and cell entry in mitosis, followed by the induction of apoptosis. Indeed, the inhibition of the G2/M checkpoint led to a significant increment of normal and aberrant mitotic cells, including those showing tripolar spindles, metaphases with lagging chromosomes, and massive chromosomes fragmentation. In conclusion, we found that the ATR-CHK1 pathway is involved in the response to Dox-induced DNA damages and we demonstrated that our new in vitro drug schedule that combines Dox followed by ATR/CHK1 inhibitors can increase Dox cytotoxicity against ALL cells, while using lower drug doses. • Doxorubicin activates the G2/M cell cycle checkpoint in acute lymphoblastic leukemia (ALL) cells. • ALL cells respond to doxorubicin-induced DNA damages by activating the ATR-CHK1 pathway. • The inhibition of the ATR-CHK1 pathway synergizes with doxorubicin in the induction of cytotoxicity in ALL cells. • The inhibition of ATR-CHK1 pathway induces aberrant chromosome segregation and mitotic spindle defects in doxorubicin-pretreated ALL cells.

Targeted Therapy and Mechanisms of Drug Resistance in Breast Cancer

Breast cancer is the most common cause of cancer-related death in women worldwide. Multidrug resistance (MDR) has been a large hurdle in reducing BC death rates. The drug resistance mechanisms include increased drug efflux, enhanced DNA repair, senescence escape, epigenetic alterations, tumor heterogeneity, tumor microenvironment (TME), and the epithelial-to-mesenchymal transition (EMT), which make it challenging to overcome. This review aims to explain the mechanisms of resistance in BC further, identify viable drug targets, and elucidate how those targets relate to the progression of BC and drug resistance.

PLAGL2 increases adriamycin resistance and EMT in breast cancer cells by activating the Wnt pathway

BACKGROUND

Adriamycin (ADR) is an effective treatment for breast cancer; nevertheless, it is often linked with acquired resistance in breast cancer cells, reducing ADR's therapeutic efficacy and increasing the risk of recurrence and poor prognosis. It has been revealed that the zinc-finger transcription factor pleomorphic adenoma gene like-2 (PLAGL2) is required for epithelial to mesenchymal transition (EMT) in cancer cells. Recent data indicates that PLAGL2 is also involved in regulating chemotherapeutic drug resistance, albeit the exact mechanism by which this happens remains unknown.

OBJECTIVE

This study examines the effect of PLAGL2 on adriamycin resistance and EMT in breast cancer cells.

METHODS

The small interfering RNA (siRNA) targeting PLAGL2 was transfected to breast cancer cells to alter PLAGL2 expression. Cell counting kit-8 (CCK-8) and colony formation assay detected cell growth and proliferation rate. Moreover, wound-healing and transwell assays were conducted to evaluate migration and invasion. Western blot (WB) checked the apoptosis and EMT-associated proteins.

RESULTS

PLAGL2 expression is associated with breast cancer cells' acquired resistance to ADR in this investigation. Additionally, deletion of PLAGL2 was associated with enhanced sensitivity to ADR, reduced proliferation, migration, and invasion capabilities, increased E-cadherin levels, and reduced Wnt6, β-catenin, and DVL1 levels in ADR-resistant breast cancer cells (MCF-7/ADR and MDA-MB-231/ADR cells). PLAGL2 could bind to the promoter region of Wnt6 and promote its expression. Additionally, the results of this research established that Wnt signaling is implicated in breast cancer cells' resistance to ADR since BML-284, a Wnt signaling activator partly restored the sensitivity of MCF-7/ADR and MDA-MB-231/ADR cells to ADR.

CONCLUSION

PLAGL2 promotes adriamycin resistance and cell aggressiveness in breast cancer cells via activating the Wnt signaling pathway.

DNA Damage Response in Cancer Therapy and Resistance: Challenges and Opportunities

Resistance to chemo- and radiotherapy is a common event among cancer patients and a reason why new cancer therapies and therapeutic strategies need to be in continuous investigation and development. DNA damage response (DDR) comprises several pathways that eliminate DNA damage to maintain genomic stability and integrity, but different types of cancers are associated with DDR machinery defects. Many improvements have been made in recent years, providing several drugs and therapeutic strategies for cancer patients, including those targeting the DDR pathways. Currently, poly (ADP-ribose) polymerase inhibitors (PARP inhibitors) are the DDR inhibitors (DDRi) approved for several cancers, including breast, ovarian, pancreatic, and prostate cancer. However, PARPi resistance is a growing issue in clinical settings that increases disease relapse and aggravate patients' prognosis. Additionally, resistance to other DDRi is also being found and investigated. The resistance mechanisms to DDRi include reversion mutations, epigenetic modification, stabilization of the replication fork, and increased drug efflux. This review highlights the DDR pathways in cancer therapy, its role in the resistance to conventional treatments, and its exploitation for anticancer treatment. Biomarkers of treatment response, combination strategies with other anticancer agents, resistance mechanisms, and liabilities of treatment with DDR inhibitors are also discussed.

Construction of prognostic signature of breast cancer based on N7-Methylguanosine-Related LncRNAs and prediction of immune response

Background: Long non-coding RNA (LncRNA) is a prognostic factor for malignancies, and N7-Methylguanosine (m7G) is crucial in the occurrence and progression of tumors. However, it has not been documented how well m7G-related LncRNAs predict the development of breast cancer (BC). This study aims to develop a predictive signature based on long non-coding RNAs (LncRNAs) associated with m7G to predict the prognosis of breast cancer patients.

Methods: The Cancer Genome Atlas (TCGA) database provided us with the RNA-seq data and matching clinical information of individuals with breast cancer. To identify the signature of N7-Methylguanosine-Related LncRNAs and create a prognostic model, we employed co-expression network analysis, least absolute shrinkage selection operator (LASSO) regression analysis, univariate Cox regression analysis, and multivariate Cox regression analysis. The signature was assessed using the Kaplan-Meier analysis and Receiver Operating Characteristic (ROC) curve. A nomogram and principal component analysis (PCA) were employed to confirm the predictive signature’s usefulness. Then, we examined the drug sensitivity between the two risk groups and utilized single-sample gene set enrichment analysis (ssGSEA) to investigate the association between predictive factors and the tumor immune microenvironment in high-risk and low-risk groups.

Results: Nine m7G-related LncRNAs (LINC01871, AP003469.4, Z68871.1, AC245297.3, EGOT, TFAP2A-AS1, AL136531.1, SEMA3B-AS1, AL606834.2) that are independently associated with the overall survival time (OS) of BC patients make up the signature we developed. For predicting 1-, 3-, and 5-year survival rates, the areas under the ROC curve (AUC) were 0.715, 0.724, and 0.726, respectively. The Kaplan-Meier analysis revealed that the prognosis of BC patients in the high-risk group was worse than that of those in the low-risk group. When compared to clinicopathological variables, multiple regression analysis demonstrated that risk score was a significant independent predictive factor for BC patients. The results of the ssGSEA study revealed a substantial correlation between the predictive traits and the BC patients’ immunological status, low-risk BC patients had more active immune systems, and they responded better to PD1/L1 immunotherapy.

Conclusion: The prognostic signature, which is based on m7G-related LncRNAs, can be utilized to inform patients’ customized treatment plans by independently predicting their prognosis and how well they would respond to immunotherapy.

Reorganization of 3D chromatin architecture in doxorubicin-resistant breast cancer cells

Background: Doxorubicin resistance remains a major therapeutic challenge leading to poor survival prognosis and treatment failure in breast cancer. Although doxorubicin induces massive changes in the transcriptional landscape are well known, potential diagnostic or therapeutic targets associated with the reorganization of three-dimensional (3D) chromatin architecture have not yet been systematically investigated.

Methods: Here we performed in situ high-throughput chromosome conformation capture (Hi-C) on parental and doxorubicin-resistant MCF7 (MCF7-DR) human breast cancer cells, followed by integrative analysis of HiC, ATAC-seq, RNA-seq and TCGA data.

Results: It revealed that A/B compartment switching was positively correlated to genome-wide differential gene expression. The genome of MCF7-DR cells was spatially reorganized into smaller topologically associating domains (TADs) and chromatin loops. We also revealed the contribution of increased chromatin accessibility and potential transcription factor families, including CTCF, AP-1 and bHLH, to gained TADs or loops. Intriguingly, we observed two condensed genomic regions (∼20 kb) with decreased chromatin accessibility flanking TAD boundaries, which might play a critical role in the formation or maintenance of TADs. Finally, combining data from TCGA, we identified a number of gained and lost enhancer-promoter interactions and their corresponding differentially expressed genes involved in chromatin organization and breast cancer signaling pathways, including FA2H, FOXA1 and JRKL, which might serve as potential treatment targets for breast cancer.

Conclusion: These data uncovered a close connection between 3D genome reorganization, chromatin accessibility as well as gene transcription and provide novel insights into the epigenomic mechanisms involving doxorubicin resistance in breast cancer.

Breast cancer: molecular mechanisms of underlying resistance and therapeutic approaches

Breast cancer (BC) affects over 250,000 women in the US each year. Drug-resistant cancer cells are responsible for most breast cancer fatalities. Scientists are developing novel chemotherapeutic drugs and targeted therapy combinations to overcome cancer cell resistance. Combining drugs can reduce the chances of a tumor developing resistance to treatment. Clinical research has shown that combination chemotherapy enhances or improves survival, depending on the patient's response to treatment. Combination therapy is a highly successful supplemental cancer treatment. This review sheds light on intrinsic resistance to BC drugs and the importance of combination therapy for BC treatment. In addition to recurrence and metastasis of BC, the article discussed biomarkers for BC.

Cross-Resistance Among Sequential Cancer Therapeutics: An Emerging Issue

Over the past two decades, cancer treatment has benefited from having a significant increase in the number of targeted drugs approved by the United States Food and Drug Administration. With the introduction of targeted therapy, a great shift towards a new era has taken place that is characterized by reduced cytotoxicity and improved clinical outcomes compared to traditional chemotherapeutic drugs. At present, targeted therapies and other systemic anti-cancer therapies available (immunotherapy, cytotoxic, endocrine therapies and others) are used alone or in combination in different settings (neoadjuvant, adjuvant, and metastatic). As a result, it is not uncommon for patients affected by an advanced malignancy to receive subsequent anti-cancer therapies. In this challenging complexity of cancer treatment, the clinical pathways of real-life patients are often not as direct as predicted by standard guidelines and clinical trials, and cross-resistance among sequential anti-cancer therapies represents an emerging issue. In this review, we summarize the main cross-resistance events described in the diverse tumor types and provide insight into the molecular mechanisms involved in this process. We also discuss the current challenges and provide perspectives for the research and development of strategies to overcome cross-resistance and proceed towards a personalized approach.

Identification and validation of a twelve immune infiltration-related lncRNA prognostic signature for bladder cancer

The prognosis of bladder cancer patients is strongly related to both the immune-infiltrating cells and the expression of lncRNAs. In this study, we analyzed the infiltration of immune cells in 403 bladder cancer samples obtained from TCGA by applying the ssGSEA to these samples, then dividing them into high/low immune cell infiltration groups. Based on these groupings, we found 404 differentially expressed immune infiltration-related lncRNAs, which were successively analyzed by univariate Cox regression, then Least Absolute Shrinkage and Selection Operator (LASSO), and finally stepwise multiple Cox regression. Then 12 differentially expressed immune infiltration-related lncRNAs were identified and used to construct a prognostic signature for bladder cancer. Subsequently, Kaplan-Meier analysis, univariate Cox regression, multivariate Cox regression, and multivariate time-dependent ROC analyses (for 1, 3, 5 years) all revealed that this signature performed well in predicting overall survival and served as an independent prognostic factor for patients with bladder cancer. Finally, both TIMER and CIBESORT showed that this 12-lncRNA prognostic signature for bladder cancer was associated with the infiltration of immune cell subtypes. Besides, nomogram considered risk score and clinical characteristics was assembled and showed great performance. More importantly, we found our signature could well distinguish the drug response of patients with bladder cancer. High risk patients showed a better response to cisplatin, doxorubicin, and anti- CTLA4 immunotherapy, low risk patients showed a better response to methotrexate and anti-PD1 immunotherapy compared with each other.

Impact of Non-Coding RNAs on Chemotherapeutic Resistance in Oral Cancer

Drug resistance in oral cancer is one of the major problems in oral cancer therapy because therapeutic failure directly results in tumor recurrence and eventually in metastasis. Accumulating evidence has demonstrated the involvement of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in processes related to the development of drug resistance. A number of studies have shown that ncRNAs modulate gene expression at the transcriptional or translational level and regulate biological processes, such as epithelial-to-mesenchymal transition, apoptosis, DNA repair and drug efflux, which are tightly associated with drug resistance acquisition in many types of cancer. Interestingly, these ncRNAs are commonly detected in extracellular vesicles (EVs) and are known to be delivered into surrounding cells. This intercellular communication via EVs is currently considered to be important for acquired drug resistance. Here, we review the recent advances in the study of drug resistance in oral cancer by mainly focusing on the function of ncRNAs, since an increasing number of studies have suggested that ncRNAs could be therapeutic targets as well as biomarkers for cancer diagnosis.

HMGB1 Promotes Resistance to Doxorubicin in Human Hepatocellular Carcinoma Cells by Inducing Autophagy via the AMPK/mTOR Signaling Pathway

Chemoresistance remains as a major hindrance in the treatment of hepatocellular carcinoma (HCC). High mobility group box protein 1 (HMGB1) enhances autophagic flux and protects tumor cells from apoptosis, which results in acquired drug resistance. However, the exact mechanisms underlying HMGB1-modulated autophagy in HCC chemoresistance remain to be defined. In the present study, we found that administration of doxorubicin (DOX) significantly promoted HMGB1 expression and induced HMGB1 cytoplasmic translocation in human HCC cell lines BEL7402 and SMMC7721, which enhanced autophagy that contributes to protecting HCC cells from apoptosis and increasing drug resistance. Moreover, we observed HMGB1 translocation and elevation of autophagy in DOX-resistant BEL7402 and SMMC7721 cells. Additionally, inhibition of HMGB1 and autophagy increased the sensitivities of BEL-7402 and SMMC-7721 cells to DOX and re-sensitized their DOX-resistant cells. Subsequently, we confirmed with HMGB1 regulated autophagy by activating the 5ʹ adenosine monophosphate-activated protein kinase (AMPK)/mTOR pathway. In summary, our results indicate that HMGB1 promotes acquired DOX resistance in DOX-treated BEL7402 and SMMC7721 cells by enhancing autophagy through the AMPK/mTOR signaling pathway. These findings provide the proof-of-concept that HMGB1 inhibitors might be an important targeted treatment strategy for HCC.

m6A-Mediated Tumor Invasion and Methylation Modification in Breast Cancer Microenvironment

Background

We analyzed the n6-methyladenosine (m6A) modification patterns of immune cells infiltrating the tumor microenvironment of breast cancer (BC) to provide a new perspective for the early diagnosis and treatment of BC.

Methods

Based on 23 m6A regulatory factors, we identified m6A-related gene characteristics and m6A modification patterns in BC through unsupervised cluster analysis. To examine the differences in biological processes among various m6A modification modes, we performed genomic variation analysis. We then quantified the relative infiltration levels of different immune cell subpopulations in the tumor microenvironment of BC using the CIBERSORT algorithm and single-sample gene set enrichment analysis. Univariate Cox analysis was used to screen for m6A characteristic genes related to prognosis. Finally, we evaluated the m6A modification pattern of patients with a single BC by constructing the m6Ascore based on principal component analysis.

Results

We identified three different m6A modification patterns in 2128 BC samples. A higher abundance of the immune infiltration of the m6Acluster C was indicated by the results of CIBERSORT and the single-sample gene set enrichment analysis. Based on the m6A characteristic genes obtained through screening, the m6Ascore was determined. The BC patients were segregated into m6Ascore groups of low and high categories, which revealed significant survival benefits among patients with low m6Ascores. Additionally, the high-m6Ascore group had a higher mutation frequency and was associated with low PD-L1 expression, and the m6Ascore and tumor mutation burden showed a positive correlation. In addition, treatment effects were better in patients in the high-m6Ascore group.

Conclusions

In case of a single patient with BC, the immune cell infiltration characteristics of the tumor microenvironment and the m6A methylation modification pattern could be evaluated using the m6Ascore. Our results provide a foundation for improving personalized immunotherapy of BC.

The clinical outcomes and genomic landscapes of acute lymphoblastic leukemia patients with E2A-PBX1: A 10-year retrospective study

The clinical outcomes and genomic features of E2A-PBX1 (TCF3-PBX1)-positive B-cell acute lymphoblastic leukemia (B-ALL) patients remain unclear. A total of 137 patients carrying E2A-PBX1 among 3164 B-ALL patients between 2009 and 2019 were retrospectively analyzed. The 5-year overall survival (OS) and disease-free survival (DFS) rates of the whole cohort were 68.6% and 61.0%, respectively. Age [DFS, p = 0.037; cumulative incidence of relapse (CIR), p = 0.005] and the level of minimal residual disease (MRD) after induction chemotherapy (OS, p = 0.020; DFS, p = 0.002; CIR, p = 0.006) were independent risk factors. In adolescents/adults, allogeneic hematopoietic stem cell transplantation (allo-HSCT) at first complete remission (CR1) significantly improved the 5-year prognosis (OS, p < 0.001; DFS, p < 0.001; CIR, p < 0.001). Haploidentical HSCT decreased the CIR compared with human leukocyte antigen-matched HSCT in adolescents/adults (p = 0.017). Mutations in PBX1, PAX5, CTCF and SETD2, amplification of AKT3, and deletion of CDKN2A/B were common in the total cohort, while transcriptome differences were found in the cell cycle, nerve growth factor (NGF) signaling pathway and transcriptional regulation by TP53 between adolescents/adults and children. Patients with multiple subclones at diagnosis tended to have unfavorable 3-year prognoses (DFS, p = 0.010; CIR, p = 0.021). Leukemia clones with DNA repair gene mutations showed aggressive and treatment-refractory phenotypes in this subtype of ALL. Our study indicated that age, the level of MRD and DNA repair gene mutations were associated with E2A-PBX1-positive B-ALL outcomes. Allo-HSCT, especially haploidentical HSCT, could improve the prognosis of adolescent/adult patients.

Genetic heterogeneity during breast cancer progression in young patients

Background

Because a number of years may be required for normal cells to develop into carcinoma, genes involved in tumorigenesis and progression might differ among breast cancers in young women and those in older women. The present study sought to analyze subclonality during breast cancer evolution as well as diversity within each individual in our young patients’ cohort.

Methods

A total of 13 women aged <35 years at diagnosis with early breast cancer were recruited. Serial sections of breast samples consisting of synchronous invasive carcinoma, adjacent ductal carcinoma in situ (DCIS), normal breast tissue, and metastatic lymph nodes were collected and prepared for immunohistochemical analysis of estrogen receptor, progesterone receptor, HER2, and Ki67, and for extraction of genomic DNA. Germline and somatic gene alterations of genomic DNA were examined by targeted sequencing.

Results

Genomic DNA from 13 blood samples and 36 breast tissues consisting of 14 invasive carcinomas, nine adjacent DCIS, 11 normal breast tissues, and two metastatic lymph nodes were successfully sequenced. Germline gene alterations including pathogenic variants and gene alterations that were not yet evaluated for their clinical significance were detected in all patients but one. Somatic gene alterations were identified in eight invasive carcinomas, five DCIS, and one metastatic lymph node. Different somatic gene alterations between invasive carcinoma and DCIS were detected in two patients. Somatic gene mutations were present in non-neoplastic tissues in three patients. No two patients had the same gene alterations.

Conclusion

Our results reveal diversity within each individual during breast cancer progression.

•

Subclonality during breast cancer progression in young patients were analyzed.

•

No two patients had the same germline and/or somatic gene alterations.

•

Somatic gene mutations were present in normal breast tissue.

The role of non-coding RNAs in drug resistance of oral squamous cell carcinoma and therapeutic potential

Oral squamous cell carcinoma (OSCC), the eighth most prevalent cancer in the world, arises from the interaction of multiple factors including tobacco, alcohol consumption, and betel quid. Chemotherapeutic agents such as cisplatin, 5-fluorouracil, and paclitaxel have now become the first-line options for OSCC patients. Nevertheless, most OSCC patients eventually acquire drug resistance, leading to poor prognosis. With the discovery and identification of non-coding RNAs (ncRNAs), the functions of dysregulated ncRNAs in OSCC development and drug resistance are gradually being widely recognized. The mechanisms of drug resistance of OSCC are intricate and involve drug efflux, epithelial-mesenchymal transition, DNA damage repair, and autophagy. At present, strategies to explore the reversal of drug resistance of OSCC need to be urgently developed. Nano-delivery and self-cellular drug delivery platforms are considered as effective strategies to overcome drug resistance due to their tumor targeting, controlled release, and consistent pharmacokinetic profiles. In particular, the combined application of new technologies (including CRISPR systems) opened up new horizons for the treatment of drug resistance of OSCC. Hence, this review explored emerging regulatory functions of ncRNAs in drug resistance of OSCC, elucidated multiple ncRNA-meditated mechanisms of drug resistance of OSCC, and discussed the potential value of drug delivery platforms using nanoparticles and self-cells as carriers in drug resistance of OSCC.

Battling Chemoresistance in Cancer: Root Causes and Strategies to Uproot Them

With nearly 10 million deaths, cancer is the leading cause of mortality worldwide. Along with major key parameters that control cancer treatment management, such as diagnosis, resistance to the classical and new chemotherapeutic reagents continues to be a significant problem. Intrinsic or acquired chemoresistance leads to cancer recurrence in many cases that eventually causes failure in the successful treatment and death of cancer patients. Various determinants, including tumor heterogeneity and tumor microenvironment, could cause chemoresistance through a diverse range of mechanisms. In this review, we summarize the key determinants and the underlying mechanisms by which chemoresistance appears. We then describe which strategies have been implemented and studied to combat such a lethal phenomenon in the management of cancer treatment, with emphasis on the need to improve the early diagnosis of cancer complemented by combination therapy.

Integrated Chromatin Accessibility and Transcriptome Landscapes of Doxorubicin-Resistant Breast Cancer Cells

BACKGROUND

Doxorubicin is one of the most effective chemotherapeutic drugs for breast cancer while its common drug resistance leads to poor patient prognosis and survival. Growing evidence indicate dynamically reorganized chromatin allows rapid access of the gene regulatory machinery to open genomic regions facilitating subsequent gene expression through direct transcription factor (TF) activation and regulatory element binding.

METHODS

To better understand the regulatory network underlying doxorubicin resistance in breast cancer cells, we explored the systematic alterations of chromatin accessibility and gene expression by the assay for transposase-accessible chromatin using sequencing (ATAC-seq) in combination with RNA sequencing, followed by integrative analysis to identify potential regulators and their targets associated with differentially accessible regions (DARs) in doxorubicin-resistant MCF7 (MCF7-DR) cells.

RESULTS

A total of 3,963 differentially expressed genes (DEGs) related to doxorubicin resistance were identified, including dramatically up-regulated MT1E, GSTP1, LDHB, significantly down-regulated TFF1, UBB, DSCAM-AS1, and histone-modifying enzyme coding genes HDAC2, EZH2, PRMT5, etc. By integrating with transcriptomic datasets, we identified 18,228 DARs in MCF7-DR cells compared to control, which were positively correlated with their nearest DEGs (r = 0.6). There were 11,686 increased chromatin-accessible regions, which were enriched in up-regulated genes related to diverse KEGG pathways, such as the cell cycle, regulation of actin cytoskeleton, signaling pathways of MAPK, PI3K/Akt and Hippo, which play essential roles in regulating cell apoptosis, proliferation, metabolism, and inflammatory responses. The 6,542 decreased chromatin-accessible regions were identified for the declined doxorubicin-associated biological processes, for instance, endocrine and insulin resistance, central carbon metabolism, signaling pathways of TGF-beta and P53. Combining data from TCGA, analyses of the DAR sequences associated with the DNA-binding motifs of significantly enriched TF families including AP-1, TEAD and FOX, indicated that the loss-function of FOXA1 might play a critical role in doxorubicin-resistant breast cancer cells (DOX-R BCCs).

CONCLUSION

These data exhibit the non-genetic landscape of chromatin accessibility and transcript levels in the DOX-R BCCs, and provide clear insights and resources for the detection of critical TFs and potential cis-regulatory elements-based putative therapeutic targets.

APC Promoter Methylation in Gastrointestinal Cancer

The adenomatous polyposis coli (APC) gene, known as tumor suppressor gene, has the two promoters 1A and 1B. Researches on APC have usually focused on its loss-of-function variants causing familial adenomatous polyposis. Hypermethylation, however, which is one of the key epigenetic alterations of the APC CpG sequence, is also associated with carcinogenesis in various cancers. Accumulating studies have successively explored the role of APC hypermethylation in gastrointestinal (GI) tumors, such as in esophageal, colorectal, gastric, pancreatic, and hepatic cancer. In sporadic colorectal cancer, the hypermethylation of CpG island in APC is even considered as one of the primary causative factors. In this review, we systematically summarized the distribution of APC gene methylation in various GI tumors, and attempted to provide an improved general understanding of DNA methylation in GI tumors. In addition, we included a robust overview of demethylating agents available for both basic and clinical researches. Finally, we elaborated our findings and perspectives on the overall situation of APC gene methylation in GI tumors, aiming to explore the potential research directions and clinical values.

A comprehensive review on time-tested anticancer drug doxorubicin

Doxorubicin or Adriamycin, is one of the most widely used chemotherapeutic drug for treating a myriad of cancers. It induces cell death through multiple intracellular targets: reactive oxygen species generation, DNA-adduct formation, topoisomerase II inhibition, histone eviction, Ca²⁺ and iron hemostasis regulation, and ceramide overproduction. Moreover, doxorubicin-treated dying cells undergo cellular modifications that enable neighboring dendritic cell activation and enhanced presentation of tumor antigen. In addition, doxorubicin also aids in the immune-mediated clearance of tumor cells. However, the development of chemoresistance and cardiotoxicity side effect has undermined its widespread applicability. Several formulations of doxorubicin and co-treatments with inhibitors, miRNAs, natural compounds and other chemotherapeutic drugs have been essential in reducing its dosage-dependent toxicity and combating the development of resistance. Further, more advanced research into the molecular mechanism of chemoresistance development would be vital in improving the overall survivability of clinical patients and in preventing cancer relapse.

Emodin Interferes With AKT1-Mediated DNA Damage and Decreases Resistance of Breast Cancer Cells to Doxorubicin

Doxorubicin (DOX) is a cytotoxic drug used for the treatment of breast cancer (BC). However, the rapid emergence of resistance toward doxorubicin threatens its clinical application, thus the need for combination therapy. Here, we interrogate the role of Emodin, a chemical compound with tumor inhibitory properties, in the resistance of BC to Doxorubicin. We first evaluated the efficacy of Emodin in the treatment of BC cells. We then used γH2A to examine doxorubicin-induced DNA damage in BC cells, with or without Emodin. Data from CCK-8, flow cytometry, and tumor xenograft assays showed that Emodin suppresses the growth of BC cells. Further, we demonstrated that Emodin enhances γH2A levels in BC cells. Moreover, bioinformatics analysis and western blot assays indicated that Emodin down-regulates the AKT1 expression, and marginally decreases the levels of DNA damage proteins (XRCC1, PARP1, and RAD51) as well as increased p53 expression in BC cells. Taken together, our data demonstrates that Emodin affects cell proliferation, and DNA damage pathways in BC cells, thus increasing the sensitivity of BC cells to doxorubicin. Besides, we confirmed that Emodin confers sensitization of BC to doxorubicin through AKT1-mediated DNA.

DNA Repair Pathways in Cancer Therapy and Resistance

DNA repair pathways are triggered to maintain genetic stability and integrity when mammalian cells are exposed to endogenous or exogenous DNA-damaging agents. The deregulation of DNA repair pathways is associated with the initiation and progression of cancer. As the primary anti-cancer therapies, ionizing radiation and chemotherapeutic agents induce cell death by directly or indirectly causing DNA damage, dysregulation of the DNA damage response may contribute to hypersensitivity or resistance of cancer cells to genotoxic agents and targeting DNA repair pathway can increase the tumor sensitivity to cancer therapies. Therefore, targeting DNA repair pathways may be a potential therapeutic approach for cancer treatment. A better understanding of the biology and the regulatory mechanisms of DNA repair pathways has the potential to facilitate the development of inhibitors of nuclear and mitochondria DNA repair pathways for enhancing anticancer effect of DNA damage-based therapy.

An Escherichia coli Effector Protein EspF May Induce Host DNA Damage via Interaction With SMC1

Enterohemorrhagic Escherichia coli (EHEC) O157: H7 is an important foodborne pathogen that causes human diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. EspF is one of the most important effector proteins injected by the Type III Secretion System. It can target mitochondria and nucleoli, stimulate host cells to produce ROS, and promote host cell apoptosis. However, the mechanism of the host-pathogen interaction leading to host oxidative stress and cell cytotoxic effects such as DNA damage remains to be elucidated. Here, we used Cell Counting Kit-8 (CCK-8) assays and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG) ELISA to study cell viability and DNA oxidative damage level after exposure to EspF. Western blot and immunofluorescence were also used to determine the level of the DNA damage target protein p-H2AX and cell morphology changes after EspF infection. Moreover, we verified the toxicity in intestinal epithelial cells mediated by EspF infection in vivo. In addition, we screened the host proteins that interact with EspF using CoIP-MS. We found that EspF may more depend on its C-terminus to interact with SMC1, and EspF could activate SMC1 phosphorylation and migrate it to the cytoplasm. In summary, this study revealed that EspF might mediate host cell DNA damage and found a new interaction between EspF and the DNA damage repair protein SMC1. Thus, EspF may mediate DNA damage by regulating the subcellular localization and phosphorylation of SMC1.

APC Promoter Hypermethylation as a Prognostic Marker in Breast Cancer Patients

Background:

Adenomatous polyposis coli (APC) promoter hypermethylation implicated in breast cancer development through Wnt signaling pathway, hypermethylation may result in inactivation of APC expression. This study aimed to investigated whether hypermethylation of APC promoter, the aggressive behavior of breast cancer cells, and correlated them with clinicopathological parameters and survival.

Methods:

Sixty-one fresh tissues of breast tumor were evaluated for APC promoter hypermethylation with methylation-specific PCR techniques (MS-PCR) and APC mRNA expression level analysis by quantitative real-time reverse transcription-PCR.

Results:

Our results show aberrant APC hypermethylation status was founded in 27 of 61 cases (44%), and significantly associated with chemotherapy treatment (OR= 6.9, 95%CI=1.5-31.01, P = 0.01), distant metastasis (OR = 5.52, 95%CI = 1.27-24.08, P = 0.04) as well as APC methylated status also associated with shorter overall survival than those without (8.4 and 11.0 years respectively, P = 0.02).

Conclusion:

The findings indicated hypermethylation of APC promoter may be used as a useful prognostic biomarker in breast cancer patients.

A look into the link between centrosome amplification and breast cancer

Centrosome amplification (CA) is a common feature of human tumors, but it is not clear whether this is a cause or a consequence of cancer. The centrosome amplification observed in tumor cells may be explained by a series of events, such as failure of cell division, dysregulation of centrosome cycle checkpoints, and de novo centriole biogenesis disorder. The formation and progression of breast cancer are characterized by genomic abnormality. The centrosomes in breast cancer cells show characteristic structural aberrations, caused by centrosome amplification, which include: an increase in the number and volume of centrosomes, excessive increase of pericentriolar material (PCM), inappropriate phosphorylation of centrosomal molecular, and centrosome clustering formation induced by the dysregulation of important genes. The mechanism of intracellular centrosome amplification, the impact of which on breast cancer and the latest breast cancer target treatment options for centrosome amplification are exhaustively elaborated in this review.

Wnt-Independent and Wnt-Dependent Effects of APC Loss on the Chemotherapeutic Response

Resistance to chemotherapy occurs through mechanisms within the epithelial tumor cells or through interactions with components of the tumor microenvironment (TME). Chemoresistance and the development of recurrent tumors are two of the leading factors of cancer-related deaths. The Adenomatous Polyposis Coli (APC) tumor suppressor is lost in many different cancers, including colorectal, breast, and prostate cancer, and its loss correlates with a decreased overall survival in cancer patients. While APC is commonly known for its role as a negative regulator of the WNT pathway, APC has numerous binding partners and functional roles. Through APC's interactions with DNA repair proteins, DNA replication proteins, tubulin, and other components, recent evidence has shown that APC regulates the chemotherapy response in cancer cells. In this review article, we provide an overview of some of the cellular processes in which APC participates and how they impact chemoresistance through both epithelial- and TME-derived mechanisms.

Mechanisms of tRNA-derived fragments and tRNA halves in cancer treatment resistance

The tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs) are newly discovered noncoding RNAs in recent years. They are derived from specific cleavage of mature and pre-tRNAs and expressed in various cancers. They enhance cell proliferation and metastasis or inhibit cancer progression. Many studies have investigated their roles in the diagnosis, progression, metastasis, and prognosis of various cancers, but the mechanisms through which they are involved in resistance to cancer treatment are unclear. This review outlines the classification of tRFs and tiRNAs and their mechanisms in cancer drug resistance, thus providing new ideas for cancer treatment.

Role of DNA Methylation in the Resistance to Therapy in Solid Tumors

Despite the recent advances in chemotherapeutic treatments against cancer, some types of highly aggressive and invasive cancer develop drug resistance against conventional therapies, which continues to be a major problem in the fight against cancer. In recent years, studies of alterations of DNA methylome have given us a better understanding of the role of DNA methylation in the development of tumors. DNA methylation (DNAm) is an epigenetic change that promotes the covalent transfer of methyl groups to DNA. This process suppresses gene expression through the modulation of the transcription machinery access to the chromatin or through the recruitment of methyl binding proteins. DNAm is regulated mainly by DNA methyltransferases. Aberrant DNAm contributes to tumor progression, metastasis, and resistance to current anti-tumoral therapies. Aberrant DNAm may occur through hypermethylation in the promoter regions of tumor suppressor genes, which leads to their silencing, while hypomethylation in the promoter regions of oncogenes can activate them. In this review, we discuss the impact of dysregulated methylation in certain genes, which impact signaling pathways associated with apoptosis avoidance, metastasis, and resistance to therapy. The analysis of methylome has revealed patterns of global methylation, which regulate important signaling pathways involved in therapy resistance in different cancer types, such as breast, colon, and lung cancer, among other solid tumors. This analysis has provided gene-expression signatures of methylated region-specific DNA that can be used to predict the treatment outcome in response to anti-cancer therapy. Additionally, changes in cancer methylome have been associated with the acquisition of drug resistance. We also review treatments with demethylating agents that, in combination with standard therapies, seem to be encouraging, as tumors that are in early stages can be successfully treated. On the other hand, tumors that are in advanced stages can be treated with these combination schemes, which could sensitize tumor cells that are resistant to the therapy. We propose that rational strategies, which combine specific demethylating agents with conventional treatment, may improve overall survival in cancer patients.

Melatonin protects against apoptosis of megakaryocytic cells via its receptors and the AKT/mitochondrial/caspase pathway

Clinical studies have shown that melatonin lowers the frequency of thrombocytopenia in patients with cancer undergoing radiotherapy or chemotherapy. Here, we investigated the mechanisms by which melatonin promotes platelet formation and survival. Our results show that melatonin exerted protective effects on serum-free induced apoptosis of CHRF megakaryocytes (MKs). Melatonin promoted the formation of MK colony forming units (CFUs) in a dose-dependent manner. Using doxorubicin-treated CHRF cells, we found that melatonin rescued G2/M cell cycle arrest and cell apoptosis induced by doxorubicin. The expression of p-AKT was increased by melatonin treatment, an effect that was abolished by melatonin receptor blocker. In addition, we demonstrated that melatonin enhanced the recovery of platelets in an irradiated mouse model. Megakaryopoiesis was largely preserved in melatonin-treated mice. We obtained the same results in vivo from bone marrow histology and CFU-MK formation assays. Melatonin may exert these protective effects by directly stimulating megakaryopoiesis and inhibiting megakaryocyte apoptosis through activation of its receptors and AKT signaling.

Identification and validation of immune-related lncRNA prognostic signature for breast cancer

The prognosis of patients with breast cancer is closely related to both the infiltration of immune cells and the expression of lncRNAs. In this study, we evaluated the infiltration of immune cells in 1109 breast cancer samples obtained from TCGA by applying the ssGSEA to the transcriptome of these samples, thereby generating high immune cell infiltration group and low immune cell infiltration group. On the basis of these groupings, we found 696 differentially expressed lncRNAs which were sequentially subjected to univariate Cox regression and stepwise multiple Cox regression analysis. 11 lncRNAs were identified as prognostic signature for breast cancer. Kaplan-Meier analysis, univariate Cox regression, multivariate Cox regression, and ROC analyses further revealed that this 11-lncRNA signature was a novel and important prognostic factor independent of multiple clinicopathological parameters. The TIMER database showed that this 11-lncRNA prognostic signature for breast cancer was associated with the infiltration of immune cell subtypes.