Reverse Doxorubicin Resistance Research Articles

TRIP13 Activates Glycolysis to Promote Cell Stemness and Strengthen Doxorubicin Resistance of Colorectal Cancer Cells.

Chemotherapy resistance is one of the main causes of clinical chemotherapy failure. Current cancer research explores the drug resistance mechanism and new therapeutic targets. This work aims to elucidate the mechanism of thyroid hormone receptor interactor 13 (TRIP13) affecting doxorubicin (DOX) resistance in colorectal cancer (CRC). Bioinformatics analyses were employed to clarify TRIP13 expression in CRC tissues and predict the correlation of the TRIP13 enrichment pathway with glycolysis-related genes and stemness index mRNAsi. Quantitative real-time polymerase chain reaction and western blot were adopted to analyze the expression of TRIP13 and glycolysis- related genes. Cell Counting Kit-8 was utilized to determine the cell viability and IC50 value. Western blot was employed to measure the expression of stemness-related factors. Cell function assays were performed to detect cells' sphere-forming ability and glycolysis level. Animal models were constructed to determine the effects of TRIP13 expression on CRC tumor growth. TRIP13 was significantly overexpressed in CRC, concentrated in the glycolysis signaling pathway, and positively correlated with stemness index mRNAsi. High expression of TRIP13 facilitated DOX resistance in CRC. Further mechanistic studies revealed that overexpression of TRIP13 could promote cell stemness through glycolysis, which was also confirmed in animal experiments. TRIP13 was highly expressed in CRC, which enhanced the DOX resistance of CRC cells by activating glycolysis to promote cell stemness. These findings offer new insights into the pathogenesis of DOX resistance in CRC and suggest that TRIP13 may be a new target for reversing DOX resistance in CRC.

PYCR3 modulates mtDNA copy number to drive proliferation and doxorubicin resistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) poses significant challenges in treatment due to its aggressive nature and limited therapeutic targets. Understanding the underlying molecular mechanisms driving TNBC progression and chemotherapy resistance is imperative for developing effective therapeutic strategies. Thus, in this study, we aimed to elucidate the role of pyrroline-5-carboxylate reductase 3 (PYCR3) in TNBC pathogenesis and therapeutic response. We observed that PYCR3 is significantly upregulated in TNBC specimens compared to normal breast tissues, correlating with a poorer prognosis in TNBC patients. Knockdown of PYCR3 not only suppresses TNBC cell proliferation but also reverses acquired resistance of TNBC cells to doxorubicin, a commonly used chemotherapeutic agent. Mechanistically, we identified the mitochondrial localization of PYCR3 in TNBC cells and demonstrated its impact on TNBC cell proliferation and sensitivity to doxorubicin through the regulation of mtDNA copy number and mitochondrial respiration. Importantly, Selective reduction of mtDNA copy number using the mtDNA replication inhibitor 2′, 3′-dideoxycytidine effectively recapitulates the phenotypic effects observed in PYCR3 knockout, resulting in decreased TNBC cell proliferation and the reversal of doxorubicin resistance through apoptosis induction. Thus, our study underscores the clinical relevance of PYCR3 and highlight its potential as a therapeutic target in TNBC management. By elucidating the functional significance of PYCR3 in TNBC, our findings contribute to a deeper understanding of TNBC biology and provide a foundation for developing novel therapeutic strategies aimed at improving patient outcomes.

Reversal Effect of NVP-BEZ235 on Doxorubicin-Resistance in Burkitt Lymphoma RAJI Cell Line

To study the reversal effect of NVP-BEZ235 on doxorubicin resistance in Burkitt lymphoma RAJI cell line. The doxorubicin-resistant cell line was induced by treating RAJI cells with a concentration gradient of doxorubicin. The levels of Pgp, p-AKT, and p-mTOR in cells were detected by Western blot. Cell viability was detected by MTT assay. IC50 was computed by SPSS. The doxorubicin-resistant Burkitt lymphoma cell line, RAJI/DOX, was established successfully. The expression of Pgp and the phosphorylation levels of AKT and mTOR in RAJI/DOX cell line were both higher than those in RAJI cell line. NVP-BEZ235 downregulated the phosphorylation levels of AKT and mTOR in RAJI/DOX cell line. NVP-BEZ235 inhibited the proliferation of RAJI/DOX cell line, and the effect was obvious when it was cooperated with doxorubicin. The constitutive activation of PI3K/AKT/mTOR pathway of RAJI/DOX cell line was more serious than RAJI cell line. NVP-BEZ235 reversed doxorubicin resistance of RAJI/DOX cell line by inhibiting the PI3K/AKT/mTOR signal pathway.

Overexpression of miR-506-3p reversed doxorubicin resistance in drug-resistant osteosarcoma cells.

Background and objective: Osteosarcoma is a common primary malignant tumor of bone, and doxorubicin is one of the most widely used therapeutic drugs. While the problem of doxorubicin resistance limits the long-term treatment benefits in osteosarcoma patients. The role of miRNAs and their target genes in osteosarcoma have become increasingly prominent. Currently, there is no report on miR-506-3p reversing doxorubicin resistance by targeting STAT3 in osteosarcoma. The purpose of this study was to investigate the molecular mechanism that overexpression of miR-506-3p reverses doxorubicin resistance in drug-resistant osteosarcoma cells. Methods: Doxorubicin-resistant osteosarcoma cells (U-2OS/Dox) were constructed by intermittent stepwise increasing stoichiometry. The target genes of miR-506-3p were predicted by bioinformatics approach and the targeting relationship between miR-506-3p and STAT3 was detected using dual luciferase reporter assay. U-2OS/Dox cells were treated with miR-506-3p overexpression and STAT3 silencing respectively. Then Western blot and RT-qPCR were used to detect the protein and mRNA expression levels of JAK2/STAT3 signaling pathway, drug-resistant and apoptotic associated molecules. The migration and invasion were assessed by cell scratch assay and transwell assay. The cell proliferative viability and apoptosis were investigated by CCK8 assay and flow cytometry assay. Results: U-2OS/Dox cells were successfully constructed with a 14.4-fold resistance. MiR-506-3p is directly bound to the 3'-UTR of STAT3 mRNA. Compared with U-2OS cells, the mRNA expression of miR-506-3p was reduced in U-2OS/Dox cells. Overexpression of miR-506-3p decreased the mRNA expression levels of JAK2, STAT3, MDR1/ABCB1, MRP1/ABCC1, Survivin and Bcl-2, and decreased the protein expression levels of p-JAK2, STAT3, MDR1/ABCB1, MRP1/ABCC1, Survivin and Bcl-2, and conversely increased Bax expression. It also inhibited the proliferation, migration and invasion of U-2OS/Dox cells and promoted cells apoptosis. The results of STAT3 silencing experiments in the above indicators were consistent with that of miR-506-3p overexpression. Conclusion: Overexpression of miR-506-3p could inhibit the JAK2/STAT3 pathway and the malignant biological behaviors, then further reverse doxorubicin resistance in drug-resistant osteosarcoma cells. The study reported a new molecular mechanism for reversing the resistance of osteosarcoma to doxorubicin chemotherapy and provided theoretical support for solving the clinical problems of doxorubicin resistance in osteosarcoma.

DNAJC12 causes breast cancer chemotherapy resistance by repressing doxorubicin-induced ferroptosis and apoptosis via activation of AKT

BackgroundChemotherapy is a primary treatment for breast cancer (BC), yet many patients develop resistance over time. This study aims to identify critical factors contributing to chemoresistance and their underlying molecular mechanisms, with a focus on reversing this resistance. MethodsWe utilized samples from the Gene Expression Omnibus (GEO) and West China Hospital to identify and validate genes associated with chemoresistance. Functional studies were conducted using MDA-MB-231 and MCF-7 cell lines, involving gain-of-function and loss-of-function approaches. RNA sequencing (RNA-seq) identified potential mechanisms. We examined interactions between DNAJC12, HSP70, and AKT using co-immunoprecipitation (Co-IP) assays and established cell line-derived xenograft (CDX) models for in vivo validations. ResultsBoruta analysis of four GEO datasets identified DNAJC12 as highly significant. Patients with high DNAJC12 expression showed an 8 % pathological complete response (pCR) rate, compared to 38 % in the low expression group. DNAJC12 inhibited doxorubicin (DOX)-induced cell death through both ferroptosis and apoptosis. Combining apoptosis and ferroptosis inhibitors completely reversed DOX resistance caused by DNAJC12 overexpression. RNA-seq suggested that DNAJC12 overexpression activated the PI3K-AKT pathway. Inhibition of AKT reversed the DOX resistance induced by DNAJC12, including reduced apoptosis and ferroptosis, restoration of cleaved caspase 3, and decreased GPX4 and SLC7A11 levels. Additionally, DNAJC12 was found to increase AKT phosphorylation in an HSP70-dependent manner, and inhibiting HSP70 also reversed the DOX resistance. In vivo studies confirmed that AKT inhibition reversed DNAJC12-induced DOX resistance in the CDX model. ConclusionDNAJC12 expression is closely linked to chemoresistance in BC. The DNAJC12-HSP70-AKT signaling axis is crucial in mediating resistance to chemotherapy by suppressing DOX-induced ferroptosis and apoptosis. Our findings suggest that targeting AKT and HSP70 activities may offer new therapeutic strategies to overcome chemoresistance in BC.

Resveratrol is an inhibitory polyphenol of epithelial-mesenchymal transition induced by Fusobacterium nucleatum

ObjectiveResveratrol is a natural phytoalexin that has anti-inflammatory properties, reverses doxorubicin resistance, and inhibits epithelial-mesenchymal transition (EMT) in many types of cancer cells. Fusobacterium nucleatum is reportedly enriched in oral squamous cell carcinoma (OSCC) tissues compared to adjacent normal tissues, sparking interest in the relationship between F. nucleatum and OSCC. Recently, F. nucleatum was shown to be associated with EMT in OSCC. In the present study, we aimed to investigate the effects of the natural plant compound resveratrol on F. nucleatum-induced EMT in OSCC. DesignF. nucleatum was co-cultured with OSCC cells, with a multiplicity of infection (MOI) of 300:1. Resveratrol was used at a concentration of 10 μM. Cell Counting Kit-8 and wound healing assays were performed to examine the viability and migratory ability of OSCC cells. Subsequently, real-time RT-PCR was performed to investigate the gene expression of EMT-related markers. Western blotting and immunofluorescence analyses were used to further analyze the expression of the epithelial marker E-cadherin and the EMT transcription factor SNAI1. ResultsCo-cultivation with F. nucleatum did not significantly enhance cell viability. The co-cultured cells displayed similarities to the positive control of EMT, exhibiting enhanced migration and expression changes in EMT-related markers. SNAI1 was significantly upregulated, whereas E-cadherin, was significantly downregulated. Notably, resveratrol inhibited F. nucleatum-induced cell migration, decreasing the expression of SNAI1. ConclusionsResveratrol inhibited F. nucleatum-induced EMT by downregulating SNAI1, which may provide a target for OSCC treatment.

Andrographolide Reverses Doxorubicin Resistance in Human Breast Cancer Stem Cells by Regulating Apoptotic Gene Expressions

BACKGROUND: Breast cancer stem cells (BCSCs) have been identified as playing a crucial role in therapeutic resistance. This resistance can be attributed to the anti-apoptotic protein survivin and the antioxidant MnSOD high expression. To overcome the resistance to doxorubicin (DOX), this study proposed the utilization of andrographolide (ANDRO), the primary bioactive compound in Andrographis paniculata leaves. The objective was to examine the role of andrographolide in regulating survivin, caspase-9, and caspase-3 gene expressions to reverse doxorubicin resistance in human BCSCs.METHODS: BCSCs were exposed to 0.1 µM DOX every two days or 50 µM rotenone (ROT) for 6 hours, subsequently supplemented with 0.3 mM ANDRO. Superoxide and peroxide levels were measured using DHE and DCFH-DA assay. The MnSOD, survivin, caspase-9, and caspase-3 mRNA expression levels were analyzed using qRT-PCR. Protein expressions were evaluated using Western blotting assay. MnSOD activity was determined using xanthine oxidase inhibition assay. The apoptotic cells were determined using Annexin-V/PI staining.RESULTS: This study indicated that the cytotoxic mechanisms of DOX, similar to ROT, in BCSCs were attributed to oxidative stress, as evidenced by an elevation in superoxide rather than peroxide levels, accompanied by a decrease in MnSOD activity. This study also highlighted that ANDRO reversed DOX resistance in BCSCs subjected to repeated DOX treatment by downregulating survivin and upregulating caspase-9 and caspase-3 mRNA expressions, thereby activating the intrinsic apoptotic pathway.CONCLUSION: This study provides insights into the role of ANDRO in modulating the expression of apoptotic genes, such as survivin, caspase-9, and caspase-3, to overcome DOX resistance in BCSCs.KEYWORDS: breast cancer, breast cancer stem cell, andrographolide, doxorubicin, oxidative stress, apoptosis

Interference KRT17 reverses doxorubicin resistance in triple-negative breast cancer cells by Wnt/β-catenin signaling pathway

BackgroundTriple-negative breast cancer (TNBC) is a subtype of breast cancer with the highest degree of malignancy and is easily resistant to drugs due to the lack of hormone receptors. Research on the resistance mechanisms in TNBC is particularly important. Keratin 17 (KRT17) is highly expressed in TNBC. Anthracycline doxorubicin (Dox) is a commonly used chemotherapeutic drug for early stage triple-negative breast cancer.ObjectiveThis study investigated the role of KRT17 in TNBC-Dox resistance.MethodsImmuno-histochemical staining, qPCR, western blotting (WB), and immunofluorescence were used to detect the expression of KRT17 in TNBC-Dox-resistant patients and in TNBC-Dox-resistant MDA-MB-468 and MDA-MB-231. the effect of KRT17 on the proliferation and migration in KRT17 knockdown of TNBC-Dox-resistant cells was determined by the CCK8, clone formation, transwell invasion and wound healing assays were used to determine.ResultsKRT17 was highly expressed in the TNBC-Dox-resistant cells. Knockdown of KRT17 significantly reduced the IC50s of TNBC-Dox-resistant and parental strains and also reduced the proliferation and invasion abilities of TNBC-Dox-resistant cell lines. KRT17 regulated the Wnt/β-catenin signaling pathway. The inhibitory effect of KRT17 knockdown on the proliferation and migration of TNBC-Dox-resistant cells was reversed by an activator of the Wnt signaling pathway.ConclusionKRT17 can inhibit the Wnt/β-catenin signaling pathway, thereby reducing the proliferation and invasion ability of TNBC-Dox-resistant cells.

Breviscapine reverses doxorubicin resistance in breast cancer and its related mechanisms.

Based on the effect of breviscapine (BRE) on reversing drug resistance of human breast cancer cell line MCF-7/doxorubicin (Dox), the mechanism was preliminarily explored. The methyl thiazolyl tetrazolium (MTT) method was introduced to detect inhibitory effect of Dox alone or in combination with BRE on MCF-7 (M) and MCF-7/Dox (MD) cells, and the inhibitory concentration (IC50 ) was obtained. Cell apoptosis and Dox concentration was assessed by flow cytometry. The drug resistance multiple and reversal fold were calculated. Western blot was performed to evaluate the expression of Bcl-2, Bax, EGFR, p-EGFR, P-gp, caspase-3, and cleaved-caspase-3 protein in cells. The efflux of Rho-123 was measured by flow cytometry and fluorescence microscopy. The IC50 of Dox on MD and M cells was 16.67 and 0.71 μg/mL, respectively, with a drug resistance ratio of 23.48 times. The IC50 of Dox combined with BRE on MD cells was 5.62 μg/mL, with a reversal ratio of 2.97 times. BRE greatly enhanced Dox-induced apoptosis of MD cells. Bax and cleaved-caspase-3 (proapoptotic protein) expression were obviously increased, while Bcl-2 (antiapoptotic protein) expression was significantly decreased after BRE treatment. BRE inhibited EGFR activation and P-gp expression. BRE increased the intracellular accumulation of Dox in MD cells by P-gp. BRE could increase the MD sensitivity to Dox via increasing Bax and cleaved-caspase-3 expression and inhibiting Bcl-2 expression, thereby promoting cell apoptosis. BRE reversed Dox resistance of MD cells by increasing Dox intracellular accumulation through inhibiting P-gp expression via EGFR.

TCFL5 knockdown sensitizes DLBCL to doxorubicin treatment via regulation of GPX4

BackgroundResistance to chemo-drug is a major cause of bad outcome in diffuse large B-cell lymphoma (DLBCL). It was reported that TCFL5 may be related to chemoresistance in childhood acute lymphoblastic leukemia. However, it is still unclear whether TCFL5 is involved in DLBCL drug-resistance. MethodsTo explore the underlying mechanism of doxorubicin resistance, recombinant lentivirus was applied to control expression of TCFL5 in DLBCL cells. CCK-8 assay was perfomed to investigate the influence of doxorubicin on proliferation of TCFL5-overexpressed or sh-TCFL5 DLBCL cells. Correlation between TCFL5 and GPX4 was analyzed with bioinformatic methods, which was further confirmed by qPCR and western blot. TCFL5 overexpression conferred doxorubicin resistance via regulating GPX4 and was verified by TUNEL assay and western blot in vitro and mice model in vivo. ResultsTCFL5 was enriched in DLBCL cells and conferred doxorubicin resistance through binding to GPX4. Inhibition of TCFL5 enhanced the sensitivity of DLBCL cells to doxorubicin. GPX4 knockdown reversed doxorubicin resistance in TCFL5-overexpressed DLBCL cells. ConclusionDLBCL cells overexpress TCFL5 that promotes chemoresistance by regulating GPX4. Targeting TCFL5 may provide a prospective therapeutic strategy for doxorubicin-resistant DLBCL.

Caffeic acid phenethyl ester reverses doxorubicin resistance in breast cancer cells via lipid metabolism regulation at least partly by suppressing the Akt/mTOR/SREBP1 pathway.

Chemotherapy is one of the common treatment methods for breast cancer, but chemoresistance is a severe challenge. Caffeic acid phenethyl ester (CAPE) is an active ingredient of propolis extract and has been shown to have a variety of beneficial effects, and its potential as a treatment for breast cancer is worth exploring. The effects of CAPE on doxorubicin (DOX) resistance were determined by cell counting kit-8 (CCK-8) assay, colony-formation assay, and flow cytometry. Oil Red O staining and the detection of free fatty acids, triglycerides, phospholipids, and cholesterol were performed to assess the status of lipid metabolism. Quantitative polymerase chain reaction (qPCR) and western blotting were applied to investigate the molecules involved in lipid metabolism and the protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/sterol regulatory element binding protein 1 (SREBP1) pathway. CAPE treatment reversed DOX resistance in breast cancer cells and suppressed their lipid metabolism. In addition, CAPE combined with DOX remarkably suppressed SREBP1 expression in part by inhibiting Akt/mTOR pathway activation. Furthermore, by inhibiting lipid metabolism, partly via the Akt/mTOR/SREBP1 pathway, CAPE ultimately reversed DOX resistance in breast cancer. Our results suggest that CAPE treatment reversed DOX resistance in breast cancer cells, at least in part by inhibiting Akt/mTOR/SREBP1 pathway-mediated lipid metabolism, indicating that CAPE may be an effective substance to assist in the treatment of breast cancer.

Hypoxia-ameliorated photothermal manganese dioxide nanoplatform for reversing doxorubicin resistance.

Drug resistance is a huge hurdle in tumor therapy. Tumor hypoxia contributes to chemotherapy resistance by inducing the hypoxia-inducible factor-1α (HIF-1α) pathway. To reduce tumor hypoxia, novel approaches have been devised, providing significant importance to reverse therapeutic resistance and improve the effectiveness of antitumor therapies. Herein, the nanosystem of bovine serum albumin (BSA)-templated manganese dioxide (MnO2) nanoparticles (BSA/MnO2 NPs) loaded with doxorubicin (DOX) (DOX-BSA/MnO2 NPs) developed in our previous report was further explored for their physicochemical properties and capacity to reverse DOX resistance because of their excellent photothermal and tumor microenvironment (TME) response effects. The DOX-BSA/MnO2 NPs showed good biocompatibility and hemocompatibility. Meanwhile, DOX-BSA/MnO2 NPs could greatly affect DOX pharmacokinetic properties, with prolonged circulation time and reduced cardiotoxicity, besides enhancing accumulation at tumor sites. DOX-BSA/MnO2 NPs can interact with H2O2 and H+ in TME to form oxygen and exhibit excellent photothermal effect to further alleviate hypoxia due to MnO2, reversing DOX resistance by down-regulating HIF-1α expression and significantly improving the antitumor efficiency in DOX-resistant human breast carcinoma cell line (MCF-7/ADR) tumor model. The hypoxia-ameliorated photothermal MnO2 platform is a promising strategy for revering DOX resistance.

Berberine Reverses Doxorubicin Resistance by Inhibiting Autophagy Through the PTEN/Akt/mTOR Signaling Pathway in Breast Cancer [Retraction

[This retracts the article DOI: 10.2147/OTT.S241632.].

Olaparib Conjugates with Selenopheno[3,2-c]quinolinone Inhibit PARP1 and Reverse ABCB1-Related Multidrug Resistance.

The restoration of the efficacy of antitumor medicines is a cornerstone in the combat with multidrug resistant (MDR) cancers. The overexpression of the ABCB1 transporter is a major obstacle to conventional doxorubicin therapy. The synergy of ABCB1 suppression and PARP1 activity inhibition that hampers malignant cell DNA repair could be a powerful tool in anticancer therapy. Herein, we report the design and synthesis of three novel olaparib conjugates with selenophenoquinolinones, their ability to reverse doxorubicin resistance in uterus sarcoma cells as well as their mechanism of action. It was found that the most potent chemosensitizer among studied compounds preserves PARP1 inhibitory activity and attenuates cells' resistance to doxorubicin by inhibiting ABCB1 transporter activity. These results demonstrate that the conjugation of PARP inhibitors with selenophenoquinolinones is a prospective direction for the development of agents for the treatment of MDR cancers.

Knockdown of the long noncoding RNA PURPL induces apoptosis and sensitizes liver cancer cells to doxorubicin

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer with increasing incidence in western countries. Most HCC patients have advanced cancer at the time of diagnosis due to the asymptomatic nature of early-stage HCC and do not qualify for potentially curative surgical treatment, thus, highlighting the need for new therapeutic strategies. Long noncoding RNAs (lncRNAs) comprise a large and heterogeneous group of non-protein coding transcripts that play important regulatory roles in numerous biological processes in cancer. In this study, we performed RNA sequencing of liver biopsies from ten HCC, ten hepatitis C virus-associated HCC, and four normal livers to identify dysregulated lncRNAs in HCC. We show that the lncRNA p53-upregulated-regulator-of-p53-levels (PURPL) is upregulated in HCC biopsies and that its expression is p53-dependent in liver cancer cell lines. In addition, antisense oligonucleotide-mediated knockdown of PURPL inhibited cell proliferation, induced apoptosis, and sensitized HepG2 human HCC cells to treatment with the chemotherapeutic agent doxorubicin. In summary, our findings suggest that PURPL could serve as a new therapeutic target for reversing doxorubicin resistance in HCC.

Connexin32 regulates expansion of liver cancer stem cells via the PI3K/Akt signaling pathway.

Liver cancer stem cells (LCSCs) are responsible for liver cancer recurrence, metastasis, and drug resistance. Previous studies by the authors demonstrated that upregulated expression of connexin 32 (Cx32) reversed doxorubicin resistance and reduced invasion and metastasis of liver cancer cells. However, the role of Cx32 in expansion of LCSCs remains unclear. A total of 85 patients were enrolled in the present study and followed-up for 5 years. The expression of Cx32 in hepatocellular carcinoma (HCC) tissues and corresponding paracancerous tissues were detected by immunohistochemistry (IHC). Cx32 was silenced in HepG2 cells and overexpressed in HCCLM3 cells and the stemness of liver cells was examined by detecting the expression of LCSC markers (EpCAM, CD133, Nanog, Oct4, Sox9, c-Myc), sphere formation, and xenograft tumorigenesis. Finally, the effect of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway on Cx32-regulated LCSC expansion was investigated. Cx32 was downregulated in LCSCs and HCC tissues, and predicted poor prognosis in patients with HCC. Overexpression of Cx32 in HCCLM3 cells significantly inhibited LCSC expansion, tumorigenesis, and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway activity. By contrast, silencing of Cx32 in HepG2 cells upregulated expansion of LCSCs and PI3K/Akt pathway activity. Modulating the activity of the PI3K/Akt pathway by SC-79 and LY294002 in HepG2 and HCCLM3 cells, respectively, confirmed that Cx32 could affect the expansion of LCSCs through PI3K/Akt signaling. In conclusion, the present study demonstrated that Cx32 regulated the expansion of LCSCs, and increased expression of Cx32 significantly inhibited the expansion of LCSCs, suggesting that Cx32 may be an optimal target for intervention of HCC.

Glenthenamines A-F: Enamine Pyranonaphthoquinones from the Australian Pasture Plant Derived Streptomyces sp. CMB-PB042.

Chemical investigations into solid phase cultivations of an Australian sheep station pasture plant derived Streptomyces sp. CMB-PB042 yielded the rare enamine naphthopyranoquinones BE-54238A (1) and BE-54238B (2), together with four new analogues, glenthenamines B-D (4-6) and F (8), and two handling artifacts, glenthenamines A (3) and E (7). Single-crystal X-ray analyses of 1 and 2 resolved configurational ambiguities in the scientific literature, while detailed spectroscopic analysis and biosynthetic considerations assigned structures inclusive of absolute configuration to 3-8. We propose a plausible sequence of biosynthetic transformations linking structural and configurational features of 1-8 and apply a novel Schiff base "fishing" approach to detect a key deoxyaminosugar precursor. These enamine naphthopyranoquinones disclose a new P-gp inhibitory pharmacophore capable of reversing doxorubicin resistance in P-gp overexpressing colon carcinoma cells.

The matricellular protein CCN6 differentially regulates mitochondrial metabolism in normal epithelium and in metaplastic breast carcinomas.

Metaplastic breast carcinoma (MBC) is an aggressive subtype of triple negative breast cancer with undefined precursors, limited response to chemotherapy, and frequent distant metastasis. Our laboratory has reported that CCN6/WISP3, a secreted protein that regulates growth factor signaling, is downregulated in over 85% of MBCs. Through generation of a mammary epithelial cell-specific Ccn6 knockout mouse model (MMTV-cre;Ccn6fl/fl) we have demonstrated that CCN6 is a tumor suppressor for MBC; MMTV-cre;Ccn6fl/fl mice develop tumors recapitulating the histopathology and proteogenomic landscape of human MBC, but the mechanisms need further investigation. In this study, we report that preneoplastic mammary glands of 8-week-old MMTV-Cre;Ccn6fl/fl female mice show significant downregulation of mitochondrial respiratory chain genes compared to controls, which are further downregulated in MBCs of MMTV-Cre;Ccn6fl/fl mice and humans. We found that CCN6 downregulation in non-tumorigenic breast cells reduces mitochondrial respiration and increases resistance to stress-induced apoptosis compared to controls. Intracellular ectopic CCN6 protein localizes to the mitochondria in MDA-MB-231 mesenchymal-like breast cancer cells, increases mitochondrial respiration and generation of reactive oxygen species, and reverses doxorubicin resistance of MBC cells. Our data highlight a novel function of CCN6 in the regulation of redox states in preneoplastic progression and suggest potential preventative and treatment strategies against MBC based on CCN6 upregulation.

Glabratephrin reverses doxorubicin resistance in triple negative breast cancer by inhibiting P-glycoprotein

Triple-negative breast cancer is one of the most aggressive breast cancer. The first therapeutic option is chemotherapy, often based on anthracycline as doxorubicin. However, chemotherapy efficacy is limited in by the presence of P-glycoprotein (Pgp), a membrane transporter protein that effluxes doxorubicin, reducing its cellular accumulation and toxicity. Inhibiting Pgp activity with effective and non-toxic products is still an open challenge. In this work, we demonstrated that the natural product Glabratephrin (Glab), a prenylated flavonoid from Tephrosia purpurea with a unique chemical structure, increased doxorubicin accumulation and cytotoxicity in triple negative breast cancer cells with high levels of Pgp, characterized by both acquired or intrinsic resistance to doxorubicin. Glab also reduced the growth of Pgp-expressing tumors, without adding significant extra-toxicities to doxorubicin treatment. Interestingly, Glab did not change the expression of Pgp, but it reduced the affinity for Pgp and the efflux of doxorubicin, as suggested by the increased Km and the reduced Vmax. In silico molecular docking predicted that Glab binds two residues (phenylalanine 322, glutamine 721) localized in the transmembrane domains of Pgp, facing the extracellular environment. Moreover, site-directed mutagenesis identified glycine 185 as a critical residue mediating the reduced catalytic efficacy of Pgp elicited by Glab. We propose Glab as an effective and safe compound able to reverse doxorubicin resistance mediated by Pgp in triple negative breast cancers, opening the way to a new combinatorial approach that may improve chemotherapy efficacy in the most refractory and aggressive breast cancer.

Precursor-Directed Biosynthesis Mediated Amplification of Minor Aza Phenylpropanoid Piperazines in an Australian Marine Fish-Gut-Derived Fungus, Chrysosporium sp. CMB-F214.

Chemical analysis of an M1 agar plate cultivation of a marine fish-gut-derived fungus, Chrysosporium sp. CMB-F214, revealed the known chrysosporazines A–D (11–14) in addition to a suite of very minor aza analogues 1–6. A microbioreactor (MATRIX) cultivation profiling analysis failed to deliver cultivation conditions that significantly improved the yields of 1–6; however, it did reveal that M2 agar cultivation produced the new natural product 15. A precursor-directed biosynthesis strategy adopting supplementation of a CMB-F214 M1 solid agar culture with sodium nicotinate enhanced production of otherwise inaccessible azachrysposorazines A1 (1), A2 (2), B1 (3), C1 (4), C2 (5) and D1 (6), in addition to four new chrysosporazines; chrysosporazines N–P (7–9) and spirochrysosporazine A (10). Structures inclusive of absolute configurations were assigned to 1–15 based on detailed spectroscopic and chemical analyses, and biosynthetic considerations. Non-cytotoxic to human carcinoma cells, azachrysosporazies 1–5 were capable of reversing doxorubicin resistance in P-glycoprotein (P-gp)-overexpressing human colon carcinoma cells (SW620 Ad300), with optimum activity exhibited by the C-2′ substituted analogues 3–5.