SAHA and cisplatin sensitize gastric cancer cells to doxorubicin by induction of DNA damage, apoptosis and perturbation of AMPK-mTOR signalling. Exp Cell Res. 2018;370:283-291. [PMID: 29959912 DOI: 10.1016/j.yexcr.2018.06.029]

A Normalization Protocol Reduces Edge Effect in High-Throughput Analyses of Hydroxyurea Hypersensitivity in Fission Yeast

Edge effect denotes better growth of microbial organisms situated at the edge of the solid agar media. Although the precise reason underlying edge effect is unresolved, it is generally attributed to greater nutrient availability with less competing neighbors at the edge. Nonetheless, edge effect constitutes an unavoidable confounding factor that results in misinterpretation of cell fitness, especially in high-throughput screening experiments widely employed for genome-wide investigation using microbial gene knockout or mutant libraries. Here, we visualize edge effect in high-throughput high-density pinning arrays and report a normalization approach based on colony growth rate to quantify drug (hydroxyurea)-hypersensitivity in fission yeast strains. This normalization procedure improved the accuracy of fitness measurement by compensating cell growth rate discrepancy at different locations on the plate and reducing false-positive and -negative frequencies. Our work thus provides a simple and coding-free solution for a struggling problem in robotics-based high-throughput screening experiments.

Reversal of P-glycoprotein-mediated multidrug resistance by natural N-alkylated indole alkaloid derivatives in KB-ChR-8-5 drug-resistant cancer cells

Multidrug resistance (MDR) remains a significant challenge in cancer chemotherapy due to the overexpression of ATP-binding cassette drug-efflux transporters, namely P-glycoprotein (P-gp)/ATP-binding cassette subfamily B member 1. In this study, derivatives of N-alkylated monoterpene indole alkaloids such as N-(para-bromobenzyl) (NBBT), N-(para-methylbenzyl) (NMBT), and N-(para-methoxyphenethyl) (NMPT) moieties were investigated for the reversal of P-gp-mediated MDR in drug-resistant KB colchicine-resistant 8-5 (KB-ChR-8-5) cells. Among the three indole alkaloid derivatives, the NBBT exhibited the highest P-gp inhibitory activity in a dose-dependent manner. Further, it significantly decreased P-gp overexpression by inactivating the nuclear translocation of the nuclear factor kappa B p-50 subunit. In the cell survival assay, doxorubicin showed 6.3-fold resistance (FR) in KB-ChR-8-5 cells compared with its parental KB-3-1 cells. However, NBBT significantly reduced doxorubicin FR to 1.7, 1.3, and 0.4 and showed strong synergism with doxorubicin for all the concentrations studied in the drug-resistant cells. Furthermore, NBBT and doxorubicin combination decreased the cellular migration and showed increased apoptotic incidence by downregulating Bcl-2, then activating BAX, caspase 3, and p53. The present findings suggest that NBBT could be a lead candidate for the reversal of P-gp- mediated multidrug resistance in cancer cells.

Differential operation of MLH1/MSH2 and FANCD2 crosstalk in chemotolerant bladder carcinoma: a clinical and therapeutic intervening study

We aimed to understand the crosstalk between mismatch repair (MMR) and FA-BRCA pathway in primary bladder carcinoma (BlCa) samples as well as in chemotolerant cell line. We analysed the genetic alterations of MLH1 and MSH2 (MMR-related genes) and after that we correlated it with the nuclear translocation of FANCD2 protein. Next, we evaluated this crosstalk in T24 BlCa cell line in response to doxorubicin treatment. In primary BlCa tumors, infrequent genetic deletion (17-20%) but frequent promoter methylation (28-55%) of MLH1 and MSH2 was observed, where MLH1 was significantly (p < 0.05) more methylated among the early staged samples (NMIBC). However, MSH2 was significantly more altered among the NMIBC samples, signifying the importance of MMR pathway during the early pathogenesis of the disease. Furthermore, BlCa samples with underexpressed MLH1/MSH2 protein possessed cytoplasmic FANCD2 protein; encouraging that inefficiency of MMR proteins might restrict FANCD2 nuclear translocation. Next, we analysed publicly available data in GEO2R tool where we observed that in response to chemotherapeutic drugs, expression of MLH1, MSH2 and FANCD2 were diminishing. Validating this result in doxorubicin tolerant T24 cells, we found that expression of MLH1 and MSH2 was gradually decreased with increasing dose of doxorubicin. Interestingly, FANCD2 mono-ubiquitination (L-form) was also reduced in chemotolerant T24 cells. The crosstalk between MMR and FA-BRCA pathway was substantiated in the primary BlCa tumors. Further, in response to doxorubicin, this crosstalk was found to be hampered due to under-expression of MLH1 and MSH2 gene, thereby rendering chemotolerance.

Histone Deacetylase Functions in Gastric Cancer: Therapeutic Target?

Gastric cancer (GC) is one of the most aggressive cancers. Therapeutic treatments are based on surgery combined with chemotherapy using a combination of platinum-based agents. However, at metastatic stages of the disease, survival is extremely low due to late diagnosis and resistance mechanisms to chemotherapies. The development of new classifications has not yet identified new prognostic markers for clinical use. The studies of epigenetic processes highlighted the implication of histone acetylation status, regulated by histone acetyltransferases (HATs) and by histone deacetylases (HDACs), in cancer development. In this way, inhibitors of HDACs (HDACis) have been developed and some of them have already been clinically approved to treat T-cell lymphoma and multiple myeloma. In this review, we summarize the regulations and functions of eighteen HDACs in GC, describing their known targets, involved cellular processes, associated clinicopathological features, and impact on survival of patients. Additionally, we resume the in vitro, pre-clinical, and clinical trials of four HDACis approved by Food and Drug Administration (FDA) in cancers in the context of GC.

Preparation of a pH‐responsive chitosan‐montmorillonite‐nitrogen‐doped carbon quantum dots nanocarrier for attenuating doxorubicin limitations in cancer therapy

Despite its widespread usage as a chemotherapy drug in cancer treatment, doxorubicin (DOX) has limitations such as short in vivo circulation time, low solubility, and poor permeability. In this regard, a pH‐responsive chitosan (CS)‐ montmorillonite (MMT)‐ nitrogen‐doped carbon quantum dots (NCQDs) nanocomposite was first developed, loaded with DOX, and then incorporated into a double emulsion to further develop the sustained release. The incorporated NCQDs into the CS‐MMT hydrogel exhibited enhanced loading and entrapment efficiencies. The presence of NCQDs nanoparticles in the CS‐MMT hydrogel also resulted in an extended pH‐responsive release of DOX over a period of 96 h compared to that of CS‐MMT‐DOX nanocarriers at pH 5.4. Based on the Korsmeyer‐Peppas model, there was a controlled DOX release at pH 5.4, while no diffusion was observed at pH 7.4, indicating fewer side effects. MTT assay showed that the cytotoxicity of DOX‐loaded CS‐MMT‐NCQDs hydrogel nanocomposite was significantly higher than those of free DOX (p < 0.001) and CS‐MMT‐NCQDs (p < 0.001) on MCF‐7 cells. Flow cytometry results demonstrated that a higher apoptosis induction achieved after incorporating NCQDs nanoparticles into CS‐MMT‐DOX nanocarrier. These findings suggest that the DOX‐loaded nanocomposite is a promising candidate for the targeted treatment of cancer cells.

Single-cell transcriptome of the mouse retinal pigment epithelium in response to a low-dose of doxorubicin

Cellular senescence of the retinal pigment epithelium (RPE) is thought to play an important role in vision-threatening retinal degenerative diseases, such as age-related macular degeneration (AMD). However, the single-cell RNA profiles of control RPE tissue and RPE tissue exhibiting cellular senescence are not well known. We have analyzed the single-cell transcriptomes of control mice and mice with low-dose doxorubicin (Dox)-induced RPE senescence (Dox-RPE). Our results have identified 4 main subpopulations in the control RPE that exhibit heterogeneous biological activities and play roles in ATP synthesis, cell mobility/differentiation, mRNA processing, and catalytic activity. In Dox-RPE mice, cellular senescence mainly occurs in the specific cluster, which has been characterized by catalytic activity in the control RPE. Furthermore, in the Dox-RPE mice, 6 genes that have not previously been associated with senescence also show altered expression in 4 clusters. Our results might serve as a useful reference for the study of control and senescent RPE.

Single cell transcriptomics pinpoints a cell subpopulation that could be involved in inducing cellular senescence of the retinal pigment epithelium, which in turn may construe retinal degenerative disease.

Gastric cancer: An epigenetic view

Gastric cancer (GC) poses a serious threat worldwide with unfavorable prognosis mainly due to late diagnosis and limited therapies. Therefore, precise molecular classification and search for potential targets are required for diagnosis and treatment, as GC is complicated and heterogeneous in nature. Accumulating evidence indicates that epigenetics plays a vital role in gastric carcinogenesis and progression, including histone modifications, DNA methylation and non-coding RNAs. Epigenetic biomarkers and drugs are currently under intensive evaluations to ensure efficient clinical utility in GC. In this review, key epigenetic alterations and related functions and mechanisms are summarized in GC. We focus on integration of existing epigenetic findings in GC for the bench-to-bedside translation of some pivotal epigenetic alterations into clinical practice and also describe the vacant field waiting for investigation.

Temozolomide modulates the expression of miRNAs in colorectal cancer

Cancer is the second leading cause of death globally, where nearly 1 in 6 deaths is due to cancer, with 70% of all deaths from cancer occur in low- and middle-income countries. The overall lifetime risk of developing colorectal cancer is 1 in 22 in men and 1 in 24 in women. In this work, we aimed to evaluate the role of temozolomide (TMZ) in controlling colon cancer cells (CRC) via regulating the miRnome. For this purpose, CRC cells (CaCo-2) were treated with 50 µM of TMZ for 48 h. Cell count using trypan test and cytotoxicity using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) were carried out, and the obtained results indicated a significant decrease in cell count (p = 0.029), and in the cell viability (p = 0.0019). Cell cycle analysis was performed using flow cytometer, and results showed that TMZ arrested CRC cells at G2/M phase. A total of 84 miRNAs were profiled using real time PCR, and the results indicated that TMZ treatment upregulated 15 of 84 miRNAs panel profiled and downregulated the rest. The TMZ-upregulated/downregulated miRNAs were predicted to interact with many epigenetic-related proteins i.e., DNMTs, EZH2, and SUV31H1. This study shed some light on the role of TMZ in regulating the miRnome of CRC and hence in different types of cancers.

NMIIA promotes tumorigenesis and prevents chemosensitivity in colorectal cancer by activating AMPK/mTOR pathway

Non-muscle myosin IIA (NMIIA) has been reported to be involved in the carcinogenesis and malignant progression of various human tumors. However, the role and potential mechanism of NMIIA in the biological functions and apoptosis in colorectal cancer (CRC) remain elusive. In this study, we found that NMIIA was overexpressed in CRC tissues and significantly associated with poor survival in CRC patients. In addition, NMIIA promoted CRC cell proliferation and invasion via activating the AMPK/mTOR pathway in vitro, and NMIIA knockdown inhibited CRC growth in vivo. Meanwhile, NMIIA knockdown downregulated the CSCs markers (CD44 and CD133) expression in CRC cells. Furthermore, AMPK/mTOR pathway activation effectively reversed the NMIIA knockdown-induced inhibition of proliferation, invasion and stemness in CRC cells. Finally, NMIIA protects CRC cells from 5-FU-induced apoptosis and proliferation inhibition through the AMPK/mTOR pathway. Taken together, these results indicate that NMIIA plays a pivotal role in CRC growth and progression by regulating AMPK/mTOR pathway activation, and it may act as a novel therapeutic target prognostic factor in CRC.

Knockdown of PDIA6 Inhibits Cell Proliferation and Enhances the Chemosensitivity in Gastric Cancer Cells

Background

Protein disulfide isomerase A6 (PDIA6), a member of the disulfide isomerase (PDI) family, has been reported to be closely associated with progression of various cancers. However, the specific effects of PDIA6 on gastric cancer (GC) remain unclear. In this study, we investigated the expression pattern and biological functions of PDIA6 in GC.

Materials and Methods

The CCK-8 assay was carried out to examine cell proliferation and cisplatin cytotoxicity. The Western blot analysis was used to measure the protein expression of PDIA6, Wnt3a and β-catenin. The xenograft tumor assay was performed to evaluate the in vivo effect of PDIA6 on GC cell proliferation and chemoresistance.

Results

PDIA6 was significantly elevated in GC tissues and cell lines. Down-regulation of PDIA6 inhibited GC cell proliferation and chemoresistance to cisplatin while up-regulation of PDIA6 promoted the proliferation and chemoresistance of GC cells. Besides, PDIA6 regulated the chemosensitivity of GC cells to cisplatin in vivo. Mechanically, PDIA6 served as a regulator of the Wnt/β-catenin signaling pathway by affecting the protein expression of Wnt3a and β-catenin in GC cells. Additionally, Wnt activator reversed the inhibitory effect of PDIA6 knockdown on cisplatin resistance in GC cells.

Conclusion

These findings provided new insight into the potential role of PDIA6 as a promising target for drug resistance in GC chemotherapy.

Overlapping targets exist between the Par-4 and miR-200c axis which regulate EMT and proliferation of pancreatic cancer cells

The last decade has witnessed a substantial expansion in the field of microRNA (miRNA) biology, providing crucial insights into the role of miRNAs in disease pathology, predominantly in cancer progression and its metastatic spread. The discovery of tumor-suppressing miRNAs represents a potential approach for developing novel therapeutics. In this context, through miRNA microarray analysis, we examined the consequences of Prostate apoptosis response-4 (Par-4), a well-established tumor-suppressor, stimulation on expression of different miRNAs in Panc-1 cells. The results strikingly indicated elevated miR-200c levels in these cells upon Par-4 overexpression. Intriguingly, the Reverse Phase Protein Array (RPPA) analysis revealed differentially expressed proteins (DEPs), which overlap between miR200c- and Par-4-transfected cells, highlighting the cross-talks between these pathways. Notably, Phospho-p44/42 MAPK; Bim; Bcl-xL; Rb Phospho-Ser807, Ser811; Akt Phospho-Ser473; Smad1/5 Phospho-Ser463/Ser465 and Zyxin scored the most significant DEPs among the two data sets. Furthermore, the GFP-Par-4-transfected cells depicted an impeded expression of critical mesenchymal markers viz. TGF-β1, TGF-β2, ZEB-1, and Twist-1, concomitant with augmented miR-200c and E-cadherin levels. Strikingly, while Par-4 overexpression halted ZEB-1 at the transcriptional level; contrarily, silencing of endogenous Par-4 by siRNA robustly augmented the Epithelial-mesenchymal transition (EMT) markers, along with declining miR-200c levels. The pharmacological Par-4-inducer, NGD16, triggered Par-4 expression which corresponded with increased miR-200c resulting in the ZEB-1 downregulation. Noteworthily, tumor samples obtained from the syngenic mouse pancreatic cancer model revealed elevated miR-200c levels in the NGD16-treated mice that positively correlated with the Par-4 and E-cadherin levels in vivo; while a negative correlation was evident with ZEB-1 and Vimentin.

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Prostate apoptosis response-4 (Par-4) stimulation elevates the endogenous miR-200c levels

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Par-4- mediated miR-200c induction modulates the ZEB-1/miR-200c axis

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Pharmacological Par-4 inducer, NGD16, boosts the miR-200c and E-cadherin levels in vivo.

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Overlapping targets between miR 200c and Par-4 signaling axis highlight the cross-talks between these pathways.

Identification of a nine-gene prognostic signature for gastric carcinoma using integrated bioinformatics analyses

BACKGROUND

Gastric carcinoma (GC) is one of the most aggressive primary digestive cancers. It has unsatisfactory therapeutic outcomes and is difficult to diagnose early.

AIM

To identify prognostic biomarkers for GC patients using comprehensive bioinformatics analyses.

METHODS

Differentially expressed genes (DEGs) were screened using gene expression data from The Cancer Genome Atlas and Gene Expression Omnibus databases for GC. Overlapping DEGs were analyzed using univariate and multivariate Cox regression analyses. A risk score model was then constructed and its prognostic value was validated utilizing an independent Gene Expression Omnibus dataset (GSE15459). Multiple databases were used to analyze each gene in the risk score model. High-risk score-associated pathways and therapeutic small molecule drugs were analyzed and predicted, respectively.

RESULTS

A total of 95 overlapping DEGs were found and a nine-gene signature (COL8A1, CTHRC1, COL5A2, AADAC, MAMDC2, SERPINE1, MAOA, COL1A2, and FNDC1) was constructed for the GC prognosis prediction. Receiver operating characteristic curve performance in the training dataset (The Cancer Genome Atlas-stomach adenocarcinoma) and validation dataset (GSE15459) demonstrated a robust prognostic value of the risk score model. Multiple database analyses for each gene provided evidence to further understand the nine-gene signature. Gene set enrichment analysis showed that the high-risk group was enriched in multiple cancer-related pathways. Moreover, several new small molecule drugs for potential treatment of GC were identified.

CONCLUSION

The nine-gene signature-derived risk score allows to predict GC prognosis and might prove useful for guiding therapeutic strategies for GC patients.

Eupalinolide J induces apoptosis, cell cycle arrest, mitochondrial membrane potential disruption and DNA damage in human prostate cancer cells

Eupalinolide J (EJ) is a new sesquiterpene lactone isolated from Eupatorium lindleyanum DC. In the present study, we investigated the anti-cancer activity of EJ on cell proliferation in human prostate cancer cells. The MTT results indicated that EJ showed marked anti-proliferative activity in PC-3 and DU-145 cells in a dose- and time-dependent manner. DAPI staining analysis demonstrated that this effect was mediated by induction of cell apoptosis. Flow cytometric analysis indicated a significant increase in apoptotic cells, cell cycle arrest at G0/G1 phase and disruption of mitochondrial membrane potential (MMP) after EJ treatment. Meanwhile, the activation of caspase-3 and caspase-9 was visibly observed. Furthermore, our results demonstrated that the expression levels of γH2AX, p-Chk1 and p-Chk2 were significantly up-regulated, suggesting the induction of DNA damage responses in EJ-treated prostate cancer cells. The above results indicated that EJ exhibited effective anti-cancer activity in vitro. It could be a promising candidate agent for the clinical treatment of prostate cancer.

cGAS-STING pathway in oncogenesis and cancer therapeutics

The host innate immunity offers the first line of defense against infection. However, recent evidence shows that the host innate immunity is also critical in sensing the presence of cytoplasmic DNA derived from genomic instability events, such as DNA damage and defective cell cycle progression. This is achieved through the cyclic GMP-AMP synthase (cGAS)/Stimulator of interferon (IFN) genes (STING) pathway. Here we discuss recent insights into the regulation of this pathway in cancer immunosurveillance, and the downstream signaling cascades that coordinate immune cell recruitment to the tumor microenvironment to destroy transformed cells through cellular senescence or cell death programs. Its central role in immunosurveillance positions the cGAS-STING pathway as an attractive anti-cancer immunotherapeutic drug target for chemical agonists or vaccine adjuvants and suggests a key node to be targeted in a synthetic lethal approach. We also discuss adaptive mechanisms used by cancer cells to circumvent cGAS-STING signaling and present evidence linking chronic cGAS-STING activation to inflammation-induced carcinogenesis, cautioning against the use of activating the cGAS-STING pathway as an anti-tumor immunotherapy. A deeper mechanistic understanding of the cGAS-STING pathway will aid in the identification of potentially efficacious anti-cancer therapeutic targets.

Convergence of therapy-induced senescence (TIS) and EMT in multistep carcinogenesis: current opinions and emerging perspectives

Drug induced resistance is a widespread problem in the clinical management of cancer. Cancer cells, when exposed to cytotoxic drugs, can reprogram their cellular machinery and resist cell death. Evasion of cell death mechanisms, such as apoptosis and necroptosis, are part of a transcriptional reprogramming that cancer cells utilize to mediate cytotoxic threats. An additional strategy adopted by cancer cells to resist cell death is to initiate the epithelial to mesenchymal transition (EMT) program. EMT is a trans-differentiation process which facilitates a motile phenotype in cancer cells which can be induced when cells are challenged by specific classes of cytotoxic drugs. Induction of EMT in malignant cells also results in drug resistance. In this setting, therapy-induced senescence (TIS), an enduring "proliferative arrest", serves as an alternate approach against cancer because cancer cells remain susceptible to induced senescence. The molecular processes of senescence have proved challenging to understand. Senescence has previously been described solely as a tumor-suppressive mechanism; however, recent evidences suggest that senescence-associated secretory phenotype (SASP) can contribute to tumor progression. SASP has also been identified to contribute to EMT induction. Even though the causes of senescence and EMT induction can be wholly different from each other, a functional link between EMT and senescence is still obscure. In this review, we summarize the evidence of potential cross-talk between EMT and senescence while highlighting some of the most commonly identified molecular players. This review will shed light on these two intertwined and highly conserved cellular process, while providing background of the therapeutic implications of these processes.

Synergistic induction of apoptosis in a cell model of human leukemia K562 by nitroglycerine and valproic acid

Nitroglycerin (NG), a nitric oxide donor, and valproic acid (VPA), an inhibitor of histone deacetylases, have impressive effects on numerous cancer cell lines. This study intended to evaluate synergistic effects of NG and VPA on cell viability and apoptosis in K562 cells. K562 cells were cultured in RPMI-1640 supplemented with 10 % heat-inactivated FBS. They were treated with different doses of NG, VPA and cisplatin for 24, 48, and 72 h, and MTT assay was performed to analyze cell viability. Also, Peripheral blood mononuclear cells (PBMC) were cultured in RPMI-1640 media and incubated with NG (200 μM), VAP (100 μM), NG+VPA (150 μM) and cisplatin (8 μM) to evaluate cytotoxicity. IC₅₀ of the drugs, when they were applied separately and in combination, were calculated using the COMPUSYN software. DNA electrophoresis, TUNEL assay, and Hoechst staining were performed to investigate apoptosis induction. RT-PCR was used for the evaluation of apoptotic genes expression. The results of the MTT assay showed that cell viability decreased at all applied doses of NG and VPA. It was noticed that the cytotoxic effects of these drugs were dose- and time-dependent. Based on the COMPUSYN output, the combination of the drugs (VPA and NG) in a certain ratio concentration synergistically decreased cell viability. Cisplatin significantly decreased cell viability of PBMCs and K562 cells. Also, the combination drug had cytotoxic effect and significantly reduced viability of K562 cells compared with PBMCs and control cells. In the target cells treated with this combination, Bax and caspase-3 expression increased but Bcl-2 expression decreased. These results suggest that NG, VPA, and their combination decreased cell viability and induced apoptosis via the intrinsic apoptotic pathway. This study suggests that this combination therapy can be considered for further evaluation as an effective chemotherapeutic strategy for patients with chronic myeloid leukemia.

Doxorubicin-Induced Cancer Cell Senescence Shows a Time Delay Effect and Is Inhibited by Epithelial-Mesenchymal Transition (EMT)

Background

Senescence is a natural barrier for the body to resist the malignant transformation of its own cells. This work investigated the senescence characteristics of cancer cells in vitro.

Material/Methods

Human cervical cancer HeLa cells were treated with different concentrations of doxorubicin for 3 days, with or without subsequent extended culture in drug-free medium for 6 days. Senescent cell ratios between these 2 culture schemes were calculated. Expression of 2 senescence-associated secretory factors, IL-6 and IL-8, were detected by RT-PCR and ELISA. Doxorubicin treatment induced epithelial-mesenchymal transition in cancer cells. The proportions of senescent cells in epithelial-like and mesenchymal-like sub-groups were calculated. Doxorubicin-treated HeLa cells were stained with Vimentin antibody and sorted by flow cytometry. Senescent cell marker p16^INK4a and IL-8 expression in Vimentin-high and Vimentin-low cells were detected by Western blot.

Results

We found that less than 1% of HeLa cells showed senescence phenotype after treatment with doxorubicin for 3 days. However, the proportion of senescent cells was significantly increased when the doxorubicin-treated cells were subsequently cultured in drug-free medium for another 6d. RT-PCR and ELISA results showed that this prolonged culture method could further improve the expression of IL-6 and IL-8. We also found that the senescent cells were mainly epithelial-like type and few presented mesenchymal-like shape. p16^INK4a and IL-8 expression were decreased in cell fraction with higher Vimentin expression.

Conclusions

Our results suggested the existence of time delay effect in doxorubicin-induced senescence of HeLa cells, and epithelial-mesenchymal transition may resist doxorubicin-induced cell senescence.

Targeting epigenetics using synthetic lethality in precision medicine

Technological breakthroughs in genomics have had a significant impact on clinical therapy for human diseases, allowing us to use patient genetic differences to guide medical care. The "synthetic lethal approach" leverages on cancer-specific genetic rewiring to deliver a therapeutic regimen that preferentially targets malignant cells while sparing normal cells. The utility of this system is evident in several recent studies, particularly in poor prognosis cancers with loss-of-function mutations that become "treatable" when two otherwise discrete and unrelated genes are targeted simultaneously. This review focuses on the chemotherapeutic targeting of epigenetic alterations in cancer cells and consolidates a network that outlines the interplay between epigenetic and genetic regulators in DNA damage repair. This network consists of numerous synergistically acting relationships that are druggable, even in recalcitrant triple-negative breast cancer. This collective knowledge points to the dawn of a new era of personalized medicine.