Up-regulation of breast cancer resistance protein plays a role in HER2-mediated chemoresistance through PI3K/Akt and nuclear factor-kappa B signaling pathways in MCF7 breast cancer cells

Epigenetic-modification associated hnRNPA3 acts as a prognostic biomarker and promotes malignant progression of HCC

OBJECTIVE

hnRNPA3 is highly expressed in numerous malignancies, including hepatocellular carcinoma (HCC), but its function and mechanism has not been elucidated. In this study, we performed a comprehensive bioinformatics analysis of hnRNPA3 in the TCGA-LIHC dataset and several experiments in vitro to investigate the function and potential mechanisms of hnRNPA3 in HCC.

METHODS

Pan-cancer expression including hnRNPA3 levels as well as DNA methylation, associated ceRNA, immune infiltration, and immune checkpoint genes of hnRNPA3 in TCGA-LIHC dataset were assessed. Logistic regression, receiver operating characteristic curve (ROC), Kaplan-Meier analysis, and nomogram modeling were used to evaluate prognostic values of hnRNPA3 in HCC. hnRNPA3 level in cell subtypes in HCC tumor microenvironment was analysed through spatial transcriptomic. "pRRophetic" package was used to predict potential chemotherapeutic drugs sensitivity. hnRNPA3 level in HCC patients and cell lines were detected by qRT-PCR or WB. hnRNPA3's impact on proliferation, migration were studied in SNU449 and HuH7 cell lines. RNA-seq showed hnRNPA3 controled different important singaling passways in HCC.

RESULTS

hnRNPA3 was significantly elevated in HCC tumors compared to controls. hnRNPA3 levels correlated with Age, HCC stage, histologic grade, and tumor status, and may independently predict the overall and disease-specific survival. Significant associations were found between hnRNPA3 levels and DNA methylation. hsa-miR-22-3p may act as a regulatory factor for hnRNPA3 and form a ceRNA network with multiple lncRNAs.Analysis of immune infiltration and immune checkpoint genes revealed a correlation between hnRNPA3 expression and macrophages. The similar conclusion also occurred in the spatial transcriptomic detection. 5-Fluorouracil, Doxorubicin, Etoposide, et al., may be potential sensitive drugs in therapy of high-hnRNPA3 HCC patients. Silencing hnRNPA3 expression in SNU449 and HuH7 cells resulted in reducing proliferation and migration. RNA-seq showed hnRNPA3 played an important regulatory role in the malignant progression of HCC.

CONCLUSION

hnRNPA3 was found to represent a promising biomarker within HCC diagnosis and prognosis and maybe a potential drug-target in HCC therapy.

Navigating the future of gastric cancer treatment: a review on the impact of antibody-drug conjugates

Gastric cancer, marked by its high incidence and poor prognosis, demands the urgent development of novel and effective treatment strategies, especially for patients ineligible for surgery or those who have had limited success with chemotherapy, radiotherapy and targeted therapies. Recently, antibody-drug conjugates (ADCs) have become a key area of investigation due to their high specificity and potent antitumor effects. These therapies combine monoclonal antibodies, designed to bind to tumor-specific antigens, with cytotoxic agents that selectively target and destroy malignant cells. ADCs have generated significant interest in clinical trials as a promising approach to improve both treatment efficacy and patient outcomes in gastric cancer. However, their clinical application is not without challenges and limitations that must be addressed. This review discusses the recent progress in the use of ADCs for gastric cancer treatment.

Navigating heme pathways: the breach of heme oxygenase and hemin in breast cancer

Breast cancer remains a significant global health challenge, with diverse subtypes and complex molecular mechanisms underlying its development and progression. This review comprehensively examines recent advances in breast cancer research, with a focus on classification, molecular pathways, and the role of heme oxygenases (HO), heme metabolism implications, and therapeutic innovations. The classification of breast cancer subtypes based on molecular profiling has significantly improved diagnosis and treatment strategies, allowing for tailored approaches to patient care. Molecular studies have elucidated key signaling pathways and biomarkers implicated in breast cancer pathogenesis, shedding light on potential targets for therapeutic intervention. Notably, emerging evidence suggests a critical role for heme oxygenases, particularly HO-1, in breast cancer progression and therapeutic resistance, highlighting the importance of understanding heme metabolism in cancer biology. Furthermore, this review highlights recent advances in breast cancer therapy, including targeted therapies, immunotherapy, and novel drug delivery systems. Understanding the complex interplay between breast cancer subtypes, molecular pathways, and innovative therapeutic approaches is essential for improving patient outcomes and developing more effective treatment strategies in the fight against breast cancer.

Cell plasticity modulation by flavonoids in resistant breast carcinoma targeting the nuclear factor kappa B signaling

Cancer cell plasticity plays a crucial role in tumor initiation, progression, and metastasis and is implicated in the multiple cancer defense mechanisms associated with therapy resistance and therapy evasion. Cancer resistance represents one of the significant obstacles in the clinical management of cancer. Some reversal chemosensitizing agents have been developed to resolve this serious clinical problem, but they have not yet been proven applicable in oncological practice. Activated nuclear factor kappa B (NF-κB) is a frequently observed biomarker in chemoresistant breast cancer (BC). Therefore, it denotes an attractive cellular target to mitigate cancer resistance. We summarize that flavonoids represent an essential class of phytochemicals that act as significant regulators of NF-κB signaling and negatively affect the fundamental cellular processes contributing to acquired cell plasticity and drug resistance. In this regard, flavokawain A, icariin, alpinetin, genistein, wogonin, apigenin, oroxylin A, xanthohumol, EGCG, hesperidin, naringenin, orientin, luteolin, delphinidin, fisetin, norwogonin, curcumin, cardamonin, methyl gallate and catechin-3-O-gallate, ampelopsin, puerarin, hyperoside, baicalein, paratocarpin E, and kaempferol and also synthetic flavonoids such as LFG-500 and 5,3'-dihydroxy-3,6,7,8,4'-pentamethoxyflavone have been reported to specifically interfere with the NF-κB pathway with complex signaling consequences in BC cells and could be potentially crucial in re-sensitizing unresponsive BC cases. The targeting NF-κB by above-mentioned flavonoids includes the modification of tumor microenvironment and epithelial-mesenchymal transition, growth factor receptor regulations, and modulations of specific pathways such as PI3K/AKT, MAP kinase/ERK, and Janus kinase/signal transduction in BC cells. Besides that, NF-κB signaling in BC cells modulated by flavonoids has also involved the regulation of ATP-binding cassette transporters, apoptosis, autophagy, cell cycle, and changes in the activity of cancer stem cells, oncogenes, or controlling of gene repair. The evaluation of conventional therapies in combination with plasticity-regulating/sensitizing agents offers new opportunities to make significant progress towards a complete cure for cancer.

ABCG2 in Acute Myeloid Leukemia: Old and New Perspectives

Despite recent advances, prognosis of acute myeloid leukemia (AML) remains unsatisfactory due to poor response to therapy or relapse. Among causes of resistance, over-expression of multidrug resistance (MDR) proteins represents a pivotal mechanism. ABCG2 is an efflux transporter responsible for inducing MDR in leukemic cells; through its ability to extrude many antineoplastic drugs, it leads to AML resistance and/or relapse, even if conflicting data have been reported to date. Moreover, ABCG2 may be co-expressed with other MDR-related proteins and is finely regulated by epigenetic mechanisms. Here, we review the main issues regarding ABCG2 activity and regulation in the AML clinical scenario, focusing on its expression and the role of polymorphisms, as well as on the potential ways to inhibit its function to counteract drug resistance to, eventually, improve outcomes in AML patients.

Multidrug efflux transporter ABCG2: expression and regulation

The adenosine triphosphate (ATP)-binding cassette efflux transporter G2 (ABCG2) was originally discovered in a multidrug-resistant breast cancer cell line. Studies in the past have expanded the understanding of its role in physiology, disease pathology and drug resistance. With a widely distributed expression across different cell types, ABCG2 plays a central role in ATP-dependent efflux of a vast range of endogenous and exogenous molecules, thereby maintaining cellular homeostasis and providing tissue protection against xenobiotic insults. However, ABCG2 expression is subjected to alterations under various pathophysiological conditions such as inflammation, infection, tissue injury, disease pathology and in response to xenobiotics and endobiotics. These changes may interfere with the bioavailability of therapeutic substrate drugs conferring drug resistance and in certain cases worsen the pathophysiological state aggravating its severity. Considering the crucial role of ABCG2 in normal physiology, therapeutic interventions directly targeting the transporter function may produce serious side effects. Therefore, modulation of transporter regulation instead of inhibiting the transporter itself will allow subtle changes in ABCG2 activity. This requires a thorough comprehension of diverse factors and complex signaling pathways (Kinases, Wnt/β-catenin, Sonic hedgehog) operating at multiple regulatory levels dictating ABCG2 expression and activity. This review features a background on the physiological role of transporter, factors that modulate ABCG2 levels and highlights various signaling pathways, molecular mechanisms and genetic polymorphisms in ABCG2 regulation. This understanding will aid in identifying potential molecular targets for therapeutic interventions to overcome ABCG2-mediated multidrug resistance (MDR) and to manage ABCG2-related pathophysiology.

A Network Pharmacology Analysis of the Systems-Perspective Anticancer Mechanisms of the Herbal Drug FDY2004 for Breast Cancer

Breast cancer is a malignant tumor with high incidence, prevalence, and mortality rates in women. In recent years, herbal drugs have been assessed as anticancer therapy against breast cancer, owing to their promising therapeutic effects and reduced toxicity. However, their pharmacological mechanisms have not been fully explored at the systemic level. Here, we conducted a network pharmacology analysis of the systems-perspective molecular mechanisms of FDY2004, an anticancer herbal formula that consists of Moutan Radicis Cortex, Persicae Semen , and Rhei Radix et Rhizoma, against breast cancer. We determined that FDY2004 may contain 28 active compounds that exert pharmacological effects by targeting 113 breast cancer-related human genes/proteins. Based on the gene ontology terms, the FDY2004 targets were involved in modulating biological processes such as cell growth, cell proliferation, and apoptosis. Pathway enrichment analysis identified various breast cancer-associated pathways that may mediate the anticancer activity of FDY2004, including the PI3K-Akt, MAPK, TNF, HIF-1, focal adhesion, estrogen, ErbB, NF-kappa B, p53, and VEGF signaling pathways. Thus, our analysis offers novel insights into the anticancer properties of herbal drugs for breast cancer treatment from a systemic perspective.

STAT3-induced ZBED3-AS1 promotes the malignant phenotypes of melanoma cells by activating PI3K/AKT signaling pathway

Melanoma is considered as the most frequent primary malignancy occurring in skin. Accumulating studies have suggested that long non-coding RNAs (lncRNAs) play critical parts in multiple cancers. In this study, we explored the molecular mechanism of ZBED3 antisense RNA 1 (ZBED3-AS1) in melanoma. We observed that ZBED3-AS1 expression was remarkably up-regulated in melanoma tissues, and high ZBED3-AS1 level was linked to unsatisfactory survival of melanoma patients. Then, we discovered that ZBED3-AS1 was overexpressed in melanoma cells compared with human epidermal melanocytes. In addition, loss-of-function assays verified that ZBED3-AS1 knockdown restrained cell proliferation, migration, epithelial-mesenchymal transition (EMT), and stemness in melanoma. In addition, signal transducer and activator of transcription 3 (STAT3), which also showed tumour-facilitating functions in melanoma, was confirmed as a transcriptional activator of ZBED3-AS1. Moreover, ZBED3-AS1 enhanced the expression of AT-rich interaction domain 4B (ARID4B) through sequestering miR-381-3p. Importantly, we further confirmed that ZBED3-AS1 promoted the malignant progression of melanoma by regulating miR-381-3p/ARID4B axis to activate the phosphatidylinositol 3-kinase/AKT serine/threonine kinase (PI3K/AKT) signalling pathway. In a word, our research might provide a novel therapeutic target for melanoma.

Targeting Thymidylate Synthase Enhances the Chemosensitivity of Triple-Negative Breast Cancer Towards 5-FU-Based Combinatorial Therapy

BACKGROUND

The ongoing treatment modalities for breast cancer (BC) primarily rely on the expression status of ER, PR and HER-2 receptors in BC tissues. Our strategy of chemosensitization provides new insights to counter chemoresistance, a major obstacle that limits the benefits of chemotherapy of mammary cancers.

METHODS

By utilizing a murine breast cancer model employing NSG mice bearing orthotopic triple-negative breast cancer (TNBC) xenografts, we have evaluated the ability of phytochemical curcumin in chemosensitizing BC to 5-Fluorouracil (5-FU) chemotherapy and the differential modulations of cellular events in response to this strategy, independent of their receptor status.

RESULTS

A significant synergistic antitumor potential was observed in the murine model with a sub-optimal dose treatment of 5-FU plus curcumin, as evaluated by a reduction in the tumor-related parameters. We authenticated the pivotal role of thymidylate synthase (TS) in regulating the 5-FU-curcumin synergism using the TNBC pre-clinical model. Our study also confirmed the pharmacological safety of this chemotherapeutic plus phytoactive combination using acute and chronic toxicity studies in Swiss albino mice. Subsequently, the molecular docking analysis of curcumin binding to TS demonstrated the affinity of curcumin towards the cofactor-binding site of TS, rather than the substrate-binding site, where 5-FU binds. Our concomitant in vivo and in silico evidence substantiates the superior therapeutic index of this combination.

CONCLUSION

This is the first-ever pre-clinical study portraying TS as the critical target of combinatorial therapy for mammary carcinomas and therefore we recommend its clinical validation, especially in TNBC patients, who currently have limited therapeutic options.

Synergistic Cytotoxicity Effect of 5-fluorouracil and SHP2 Inhibitor Demethylincisterol A3 on Cervical Cancer Cell

BACKGROUND

Demethylincisterol A3 (DTA3) has been identified as an SHP2 inhibitor and suppresses the growth of many cancer cells. 5-Fluorouracil (5-FU) is widely used for the clinical treatment of various cancers. However, the combined effects of 5-FU and DTA3 on cervical cancer cells remain unknown.

OBJECTIVE

This study evaluates the mechanism of the combined effects of 5-FU and DTA3 in cervical cancer cells.

METHODS

The synergistic cytotoxic effects of 5-FU and DTA3 in cervical cancer cells were calculated. Apoptosis was analysed by flow cytometry. Western blot analyses were used to examine the related signalling pathways.

RESULTS

DTA3 and 5-FU synergized to induce apoptosis and repress proliferation of cervical cancer cells by downregulating the activation of PI3K/AKT and NF-κB signalling pathway. We provided evidence that the upregulation of SHP2 expression by transfection significantly inhibited the cytotoxicity of 5-FU and DTA3. SHP2 knockdown enhanced the antiproliferation activity of 5-FU, indicating targeting SHP2 sensitized cervical cancer cells to 5-FU.

CONCLUSION

Our study demonstrates that SHP2 inhibitor DTA3 and 5-FU have a synergistic cytotoxic effect on cervical cancer cells. The synergistic combination of SHP2 inhibitor and 5-FU may present a promising strategy for the treatment of cervical cancer.

Effects of Sambucus Ebulus Extract on Cell Proliferation and Viability of Triple-Negative Breast Cancer: An In Vitro and In Vivo Study

BACKGROUND

Triple-negative breast cancer (TNBC) accounts for 15% of all breast cancer (BC) cases and is a severe type of BC. Since medicinal herbs containing biocompatible substances that are accepted by patient more than chemical therapeutics, they can be considered a safe option for treating BC.

OBJECTIVE

This study evaluated the effect of Sambucus Ebulus (S. ebulus) extract on a model of TNBC.

METHODS

S. ebulus extract was prepared using petroleum ether, ethyl acetate, and methanol. The petroleum ether extract was fractionated and analyzed using vacuum liquid chromatography and GC-MS, respectively. MDA-MB-231 and MCF-10A were used as TNBC and normal breast cells, respectively. Flowcytometry and MTT assays were performed to evaluate cell cycle, apoptosis, and viability of the cells. Gene expression analysis was performed using RT-qPCR. Nude mouse allograft tumor models were used, and pathological sections were evaluated.

RESULTS

The findings indicated that S. ebulus extract remarkably decreased cell proliferation and viability. The extract had no toxicity to the normal breast cells but efficiently killed the cancer cells. Cell cycle- and apoptosis-related gene expression showed that fraction 4 of S. ebulus extract significantly increased the expression of Bax, Bak, P53, and c-MYC.

CONCLUSION

This study showed satisfactory results of the effect of S. ebulus extract on clearing BC cells both in vitro and in vivo. Thus, S. ebulus extract may be a safe herbal compound for eliminating BC cells without toxicity to host cells.

The role of epithelial-mesenchymal transition-regulating transcription factors in anti-cancer drug resistance

The complex orchestration of gene expression that mediates the transition of epithelial cells into mesenchymal cells is implicated in cancer development and metastasis. As the primary regulator of the process, epithelial-mesenchymal transition-regulating transcription factors (EMT-TFs) play key roles in metastasis. They are also highlighted in recent preclinical studies on resistance to cancer therapy. This review describes the role of three main EMT-TFs, including Snail, Twist1, and zinc-finger E homeobox-binding 1 (ZEB1), relating to drug resistance and current possible approaches for future challenges targeting EMT-TFs.

High Intrinsic Expression of P-glycoprotein and Breast Cancer Resistance Protein in Canine Mammary Carcinomas Regardless of Immunophenotype and Outcome

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are major actors in multidrug resistance (MDR) phenomenon in both human and canine mammary carcinomas (CMCs). The aim of this study was to investigate an association between the intrinsic expression of P-gp and BCRP compared to the immunophenotypes and outcome in CMCs. Fifty CMCs were evaluated at immunohistochemistry (IHC) for P-gp, BCRP, Estrogen receptor alpha (ER), Progesterone receptors (PR), Human Epidermal Growth Factor Receptor type 2 (HER2), basal cytokeratins 5/6 (CK5/6), Epidermal Growth Factor Receptor 1 (EGFR), and Ki67 proliferation index. P-gp and BCRP positive cases were, respectively, 52% and 74.5%, with a significantly higher expression of BCRP than P-gp. Five immunophenotypes were defined in 37 out of 50 CMCs: 9 (24.3%) Luminal A, 5 (13.5%) Luminal B, 9 (24.3%) HER2 overexpressing, 9 (24.3%) Triple-negative basal-like, and 5 (13.5%) Triple-negative non-basal-like. In all CMCs at least one marker was expressed. Follow-up data were available for 25 animals. The average cancer-specific survival was 739 ± 444 days. A number of CMCs bear a high expression of P-gp and BCRP but no significant association was found between their expression and the immunophenotypes, Ki67 index, the histological grade, and tumor-related death.

sATP‑binding cassette subfamily G member 2 enhances the multidrug resistance properties of human nasal natural killer/T cell lymphoma side population cells

Extranodal natural killer (NK)/T cell lymphoma, nasal type (ENKL) is a rare type of non-Hodgkin's lymphoma that is associated with limited effective treatment options and unfavorable survival rate, which is partly the result of multidrug resistance (MDR). The presence of side population (SP) cells-SNK-6/ADM-SP (SSP) cells has been previously used to explore mechanisms of drug resistance. ATP-binding cassette subfamily G member 2 (ABCG2) is a gene involved in MDR and is closely associated with SPs. However, the function of ABCG2 in SSP cells is unclear. The present study verified the high expression of ABCG2 in SSP cells. The IC₅₀ values of doxorubicin, cytarabine, cisplatin, gemcitabine and l-asparaginase were tested to evaluate drug sensitivity in SSP cells with different levels of ABCG2 expression. ABCG2 was identified as a gene promoting in MDR. ABCG2 upregulated cell proliferation, increased clonogenicity, increased invasive ability and decreased apoptosis, in vivo and in vitro, when cells were treated with gemcitabine. To conclude, ABCG2 enhanced MDR and increased the typical biological characteristics associated with cancer cells in SP cells. With further investigation of the ABCG2 gene could have the potential to reverse MDR in ENKL.

Pyrotinib Sensitizes 5-Fluorouracil-Resistant HER2+ Breast Cancer Cells to 5-Fluorouracil

5-Fluorouracil (5-FU) is a widely used chemotherapeutic agent for breast cancer. However, acquired chemoresistance leads to a loss of its efficacy; methods to reverse are urgently needed. Some studies have shown that pyrotinib, an ErbB receptor tyrosine kinase inhibitor, is effective against HER2⁺ breast cancer. However, whether pyrotinib sensitizes 5-FU-resistant breast cancer cells to 5-FU is unknown. We hypothesized that the combination of pyrotinib and 5-FU would show synergistic antitumor activity, and pyrotinib could reverse 5-FU resistance in HER2⁺ breast cancer cells in vitro and in vivo. Our data showed that pyrotinib inhibited the growth of 5-FU-resistant SKBR-3/FU and MDA-MB-453/FU cell lines and the parental cell lines. 5-FU remarkably suppressed the growth of SKBR-3 and MAD-MB-453 cells. However, SKBR-3/FU and MAD-MB-453/FU cells showed resistance to 5-FU. A combination of pyrotinib and 5-FU resulted in the synergistic inhibition of the growth of the 5-FU-resistant SKBR-3/FU and MDA-MB-453/FU cell lines and the parental cell lines. Pyrotinib decreased significantly the IC₅₀ values of 5-FU and the thymidylate synthase (TS) mRNA expression levels in the 5-FU-resistant SKBR-3/FU and MDA-MB-453/FU cell lines and the parental cell lines and increased significantly the intracellular concentration of 5-FU in SKBR-3/FU and MDA-MB-453/FU cells. In addition, pyrotinib reduced the ABCG2 mRNA and protein expression levels in SKBR-3/FU and MDA-MB-453/FU cells and downregulated the protein expression levels of pAKT, pHER2, and pHER4 in all four cell lines. After TS or ABCG2 in 5-FU-resistant breast cancer cells was knocked down, the sensitivity of SKBR-3/FU and MDA-MB-453/FU cells to 5-FU was restored. Moreover, in vivo experiments demonstrated that pyrotinib in combination with 5-FU more effectively inhibited SKBR-3/FU tumor growth than either pyrotinib or 5-FU alone. In conclusion, our findings suggest that pyrotinib could restore sensitivity of 5-FU-resistant HER2⁺ breast cancer cells to 5-FU through downregulating the expression levels of TS and ABCG2.

Inhibitor of Interleukin-1 Receptor-associated Kinases 1/4, Can Increase the Sensitivity of Breast Cancer Cells to Methotrexate

Breast cancer is the most common type of cancer among women. Chemotherapy is one of the main methods of breast cancer treatment, but this method is increasingly affected due to drug resistance. One of the newly discovered factors associated with drug resistance in cancer cells is interleukin receptor-associated kinase 1 (IRAK1). The aim of this study was to investigate the relationship between IRAK1 inhibition and sensitivity to methotrexate (MTX). Effects of various concentrations of MTX and constant concentration (1μg/ml) of IRAK1/4 inhibitor was examined on MCF-7, BT-20, BT-549, MB-468 cell lines. Cell viability was examined by water soluble tetrazole -1, and cell apoptosis by flow cytometry. The expression of IRAK1 and BCRP genes was also assessed by real-time PCR method. IRAK1 inhibitor decreased IC₅₀ in all examined cell lines, but the most prominent effect was observed in MB-468. 72 h incubation of cell lines with IRAK inhibitor and MTX, significantly increased the annexin-V and annexin-V/7AAD positive cells, suggesting an apoptotic effect of IRAK on all examined breast cancer cell lines. RT-qPCR test results showed that the IRAK inhibitor had no effect on the expression of BCRP at any time. Our results showed that IRAK inhibitor can increase the chemosensitivity of breast cancer cell lines without effect on BCRP mRNA expression. IRAK inhibitor in combination with MTX can induce apoptosis in breast cancer cell lines.

Analysis Natrium Iodide Symporter Expression in Breast Cancer Subtypes for Radioiodine Therapy Response

Purpose

This study investigates natrium iodide symporter (NIS) expression in three breast cancer subtypes to predict radioiodine response.

Materials and Methods

Frozen breast tissues from triple negative (TN), human epidermal receptor 2 (HER2+), and luminal A cancers were used in this research. NIS protein expression in each subtype was analyzed using immunohistochemistry (IHC) and western blot (WB). Secondary data such as age, subtypes, and Ki 67 index were drawn from the surgical oncologist database. Breast cancer cell lines were used to investigate the effect of radioiodine by measuring cell proliferation.

Results

The forty-one breast cancer samples were analyzed consisted of the following subtypes: TN, HER2+, and luminal A were 58%, 22%, and 20% respectively. The stages of disease were 2A to 4A. Most of samples were at 3B. Ki 67 index of TN, HER2+, and luminal A were 21 ± 12, 19 ± 5, and 7 ± 3 respectively. The NIS expression was detected in 95% of samples in cytoplasm and/or cell membrane; 93% of samples were invasive breast carcinomas. Only 20% of the samples showed NIS expression at cell membrane; four samples were HER2+, and other four were TN subtypes. NIS membrane score was significantly positively correlated with Ki67 index, p = 0.04. NIS protein expression was detected at sizes 88 kDa, 50 kDa, and 27 kDa. Cell proliferation rate means of MDA-MB 231, SKBR3, and MCF7 cells were 81.6 ± 4, 10.6 ± 5, and 15.4 ± 13 respectively (p = 0.009).

Conclusion

NIS protein expression is detectable in breast cancer cells to varying degrees. HER2+ is the most likely to express NIS in the cell membrane followed by TN subtypes. This indicates that radioiodine could be used as a novel adjuvant treatment in breast cancer.

Reviewing the mechanisms of natural product-drug interactions involving efflux transporters and metabolic enzymes

The World Health Organization (WHO) and other worldwide health agencies have recently taken initiatives to encourage the use of traditional medicine and/or complementary/alternative medicine in order to promote well-being and public health. In this way, one of the WHO's concerns is the safe use of these therapies. Phytotherapy is a strategy consisting of the use of medicinal plants (MP) and/or herbal medicinal products (HMP) for medicinal purposes. The use of phytotherapy concomitantly with drugs may cause interactions compromising the expected pharmacological action or generating toxic effects. These interactions are complex processes that may occur with multiple medications targeting different metabolic pathways, and involving different compounds present in MP and HMP. Thus, the aim of this review was to summarize the main MP- and HMP-drug interactions that involve specific transporters (P-glycoprotein and BCRP) and CYP450 enzymes (CYP3A4 and CYP2D6), which play relevant roles in the mechanisms of interactions. Firstly, multiple databases were used to search studies describing in vitro or in vivo MP and HMP-drug interactions and, after that, a systematic note-taking and appraisal of the literature was conducted. It was observed that several MP and HMP, metabolic pathways and transcription factors are involved in the transporters and enzymes expression or in the modulation of their activity having the potential to provide such interactions. Thus, the knowledge of MP- and HMP-drug interaction mechanisms could contribute to prevent harmful interactions and can ensure the safe use of these products to help the establishment of the therapeutic planning in order to certify the best treatment strategy to be used.

Chemoresistance mechanisms of breast cancer and their countermeasures

Chemoresistance is one of the major challenges for the breast cancer treatment. Owing to its heterogeneous nature, the chemoresistance mechanisms of breast cancer are complicated, and not been fully elucidated. The existing treatments fall short of offering adequate solution to drug resistance, so more effective approaches are desperately needed to improve existing therapeutic regimens. To overcome this hurdle, a number of strategies are being investigated, such as novel agents or drug carriers and combination treatment. In addition, some new therapeutics including gene therapy and immunotherapy may be promising for dealing with the resistance. In this article, we review the mechanisms of chemoresistance in breast cancer. Furthermore, the potential therapeutic methods to overcome the resistance were discussed.

Estradiol induces cell proliferation in MCF‑7 mammospheres through HER2/COX‑2

Cluster of differentiation (CD)44+/CD24- breast cancer cells have stem cell‑like characteristics and are potent initiators of tumorigenesis. Mammosphere cells can partially initiate breast tumorigenesis by inducing estradiol (E2)‑dependent breast cancer cells. However, the mechanisms by which E2 mediates cancer formation in MCF‑7 mammosphere (MS) cells have remained elusive. In the present study, MS cells were isolated by sphere culture. It was possible to maintain these MS cells in culture for long periods of time, while retaining the CD44+/CD24- stem cell marker status. The CD44+/CD24- status was confirmed by flow cytometry. Furthermore, the stem‑cell markers Musashi‑1, cytokeratin (CK)7 and CK19 were identified by immunofluorescence microscopy. It was revealed that treatment of MS cells with E2 increased the expression of CD44, whereas decreased the expression of CD24 on MS cells. In addition, treatment with E2 increased colony formation by MS cells. E2 also induced cyclooxygenase‑2 (COX‑2) expression in MS cells, which promoted their proliferation through the estrogen receptor/human epidermal growth factor receptor 2 (HER2)/mitogen‑activated protein kinase/phosphoinositide‑3 kinase signaling pathway. The results suggested a tumorigenic mechanism by which E2 promotes tumor cell proliferation via HER2/COX‑2 signaling. The present study provided evidence for the molecular impact of E2 on breast tumorigenesis, and suggested possible strategies for preventing and treating human breast cancer.

Chemoresistance‑related long non‑coding RNA expression profiles in human breast cancer cells

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death in females worldwide. Chemoresistance has been a major reason for the drug therapy failure. The present study performed a microarray analysis between MCF-7 and MCF-7/adriamycin (ADR) cells, and intended to identify long non-coding (lnc)RNA expression character in drug resistant breast cancer cells. MCF-7/ADR cells were induced from MCF-7 cells via pulse-selection with doxorubicin for 4 weeks, and the resistance to doxorubicin of ADR cells was confirmed by MTT assay. Microarray analysis was performed between MCF-7 and MCF-7/ADR cells. Total RNA was extracted from the two cell lines respectively and was transcribed into cDNA. The results of the microarray were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Gene Ontology (GO) and pathways analysis were conducted to enrich the dysregulated lncRNAs presented in the microarray results. Compared to the MCF-7 cells, 8,892 lncRNAs were differentially expressed in MCF/ADR cells (absolute fold-change >2.0). A total of 32 lncRNAs were selected for RT-qPCR by fold-change filtering, standard Student's t-test, and multiple hypothesis testing. Among the dysregulated lncRNAs, AX747207 was prominent because its associated gene RUNX3 was previously reported to be relative to malignant tumor chemoresistance. GO analysis results also indicated some biological processes and molecular functions linked to chemoresistance. The pathway enrichment results provided some potential pathways associated with chemoresistance. In the present study, the authors intended to identify lncRNA expression character in drug resistant cell line MCF-7/ADR, corresponding to the parental MCF-7 cell line. In addition, the study identified the lncRNA AX747207, and its potential targeted gene RUNX3, may be related to chemoresistance in breast cancer. These results may new insights into exploring the mechanisms of chemoresistance in breast cancer.

Characterization of acquired paclitaxel resistance of breast cancer cells and involvement of ABC transporters

Development of taxane resistance has become clinically very important issue. The molecular mechanisms underlying the resistance are still unclear. To address this issue, we established paclitaxel-resistant sublines of the SK-BR-3 and MCF-7 breast cancer cell lines that are capable of long-term proliferation in 100nM and 300nM paclitaxel, respectively. Application of these concentrations leads to cell death in the original counterpart cells. Both sublines are cross-resistant to doxorubicin, indicating the presence of the MDR phenotype. Interestingly, resistance in both paclitaxel-resistant sublines is circumvented by the second-generation taxane SB-T-1216. Moreover, we demonstrated that it was not possible to establish sublines of SK-BR-3 and MCF-7 cells resistant to this taxane. It means that at least the tested breast cancer cells are unable to develop resistance to some taxanes. Employing mRNA expression profiling of all known human ABC transporters and subsequent Western blot analysis of the expression of selected transporters, we demonstrated that only the ABCB1/PgP and ABCC3/MRP3 proteins were up-regulated in both paclitaxel-resistant sublines. We found up-regulation of ABCG2/BCRP and ABCC4 proteins only in paclitaxel-resistant SK-BR-3 cells. In paclitaxel-resistant MCF-7 cells, ABCB4/MDR3 and ABCC2/MRP2 proteins were up-regulated. Silencing of ABCB1 expression using specific siRNA increased significantly, but did not completely restore full sensitivity to both paclitaxel and doxorubicin. Thus we showed a key, but not exclusive, role for ABCB1 in mechanisms of paclitaxel resistance. It suggests the involvement of multiple mechanisms in paclitaxel resistance in tested breast cancer cells.

Resveratrol chemosensitizes HER-2-overexpressing breast cancer cells to docetaxel chemoresistance by inhibiting docetaxel-mediated activation of HER-2-Akt axis

As breast cancer cells often develop chemoresistance, better therapeutic options are in search to circumvent it. Here we demonstrate that human epidermal growth factor receptor-2 (HER-2)-overexpressing breast cancer cells resist docetaxel-induced cytotoxicity by upregulating HER-2 and its activity downstream, through Akt and mitogen-activated protein kinase (MAPK) pathways. We observed that introducing resveratrol as a chemosensitizer in docetaxel chemotherapy blocks upregulation and activation of HER-2 in addition to blocking downstream signaling pathways such as Akt. Resveratrol and docetaxel combination results in the synergistic induction of cell death in HER-2-overexpressing SK-BR-3 cells, whereas introduction of wild-type HER-2 in MDA-MD-231 cells increased the resistance to docetaxel. Dominant-negative HER-2 sensitizes SK-BR-3 cells to docetaxel. Our study identified a new synergistic therapeutic combination that targets HER-2-induced breast cancer resistance and might help to overcome therapeutic resistance during breast cancer therapy. The synergism of docetaxel and resveratrol was maximum in SK-BR-3, which is unique among the cell lines studied, due to its high expression status of HER-2, a receptor known to dictate the signaling environment of breast cancer cells. Docetaxel could further induce HER-2 activity in these cells, which was downregulated on resveratrol treatment. Transfection of DN-HER-2 in SK-BR-3 cells inhibits the synergism as the transfection itself sensitizes these cells to docetaxel, leaving no role for resveratrol, whereas ectopic expression of HER-2 introduces the synergism in MDA-MB-231, the triple-negative cell line, in which the synergism was minimum, attesting the crucial role of HER-2 in suppressing the sensitivity to docetaxel. Single-agent docetaxel induced HER-2-mediated resistance to cell death, which was blocked by resveratrol. Resveratrol also downregulated docetaxel-induced activation of MAPK and Akt, survival signaling pathways downstream of HER-2. In short, this study, for the first time, establishes the role of HER-2–Akt signaling axis in regulating the synergistic effect of docetaxel and resveratrol in breast cancer cells overexpressing HER-2.

Doxorubicin resistance in breast cancer is driven by light at night-induced disruption of the circadian melatonin signal

Chemotherapeutic resistance, particularly to doxorubicin (Dox), represents a major impediment to successfully treating breast cancer and is linked to elevated tumor metabolism and tumor over-expression and/or activation of various families of receptor- and non-receptor-associated tyrosine kinases. Disruption of circadian time structure and suppression of nocturnal melatonin production by dim light exposure at night (dLEN), as occurs with shift work, and/or disturbed sleep-wake cycles, is associated with a significantly increased risk of an array of diseases, including breast cancer. Melatonin inhibits human breast cancer growth via mechanisms that include the suppression of tumor metabolism and inhibition of expression or phospho-activation of the receptor kinases AKT and ERK1/2 and various other kinases and transcription factors. We demonstrate in tissue-isolated estrogen receptor alpha-positive (ERα+) MCF-7 human breast cancer xenografts, grown in nude rats maintained on a light/dark cycle of LD 12:12 in which dLEN is present during the dark phase (suppressed endogenous nocturnal melatonin), a significant shortening of tumor latency-to-onset, increased tumor metabolism and growth, and complete intrinsic resistance to Dox therapy. Conversely, a LD 12:12 dLEN environment incorporating nocturnal melatonin replacement resulted in significantly lengthened tumor latency-to-onset, tumor regression, suppression of nighttime tumor metabolism, and kinase and transcription factor phosphorylation, while Dox sensitivity was completely restored. Melatonin acts as both a tumor metabolic inhibitor and circadian-regulated kinase inhibitor to reestablish the sensitivity of breast tumors to Dox and drive tumor regression, indicating that dLEN-induced circadian disruption of nocturnal melatonin production contributes to a complete loss of tumor sensitivity to Dox chemotherapy.

A literature mining-based approach for identification of cellular pathways associated with chemoresistance in cancer

Chemoresistance is a major obstacle to the successful treatment of many human cancer types. Increasing evidence has revealed that chemoresistance involves many genes and multiple complex biological mechanisms including cancer stem cells, drug efflux mechanism, autophagy and epithelial-mesenchymal transition. Many studies have been conducted to investigate the possible molecular mechanisms of chemoresistance. However, understanding of the biological mechanisms in chemoresistance still remains limited. We surveyed the literature on chemoresistance-related genes and pathways of multiple cancer types. We then used a curated pathway database to investigate significant chemoresistance-related biological pathways. In addition, to investigate the importance of chemoresistance-related markers in protein-protein interaction networks identified using the curated database, we used a gene-ranking algorithm designed based on a graph-based scoring function in our previous study. Our comprehensive survey and analysis provide a systems biology-based overview of the underlying mechanisms of chemoresistance.

Implications of Akt2/Twist crosstalk on breast cancer metastatic outcome

Akt2 is a pivotal player in a complex web of signaling pathways controlling cell growth, proliferation, and survival. The deregulation or aberrations of Akt2 have been associated with tumor progression, metastatic spread, and, lastly, chemoresistance. The impairment of its activity has gained more attention because Akt2 is intertwined with a range of signaling paths, including the Phosphatidylinositol 3 kinase/Akt/Mammalian target of rapamycin (PI3K/mTOR) signaling axis, which are involved in macromolecules synthesis and metabolism. Here, we focus on Akt2 because of its involvement in the acquisition of stem cell-like properties, responsible for invasiveness and chemoresistance, also promoted by Twist. We also suggest therapeutic strategies targeting Akt2 to overcome the drawbacks of current cancer therapies.

Melatonin: an inhibitor of breast cancer

The present review discusses recent work on melatonin-mediated circadian regulation, the metabolic and molecular signaling mechanisms that are involved in human breast cancer growth, and the associated consequences of circadian disruption by exposure to light at night (LEN). The anti-cancer actions of the circadian melatonin signal in human breast cancer cell lines and xenografts heavily involve MT1 receptor-mediated mechanisms. In estrogen receptor alpha (ERα)-positive human breast cancer, melatonin suppresses ERα mRNA expression and ERα transcriptional activity via the MT1 receptor. Melatonin also regulates the transactivation of other members of the nuclear receptor superfamily, estrogen-metabolizing enzymes, and the expression of core clock and clock-related genes. Furthermore, melatonin also suppresses tumor aerobic metabolism (the Warburg effect) and, subsequently, cell-signaling pathways critical to cell proliferation, cell survival, metastasis, and drug resistance. Melatonin demonstrates both cytostatic and cytotoxic activity in breast cancer cells that appears to be cell type-specific. Melatonin also possesses anti-invasive/anti-metastatic actions that involve multiple pathways, including inhibition of p38 MAPK and repression of epithelial-mesenchymal transition (EMT). Studies have demonstrated that melatonin promotes genomic stability by inhibiting the expression of LINE-1 retrotransposons. Finally, research in animal and human models has indicated that LEN-induced disruption of the circadian nocturnal melatonin signal promotes the growth, metabolism, and signaling of human breast cancer and drives breast tumors to endocrine and chemotherapeutic resistance. These data provide the strongest understanding and support of the mechanisms that underpin the epidemiologic demonstration of elevated breast cancer risk in night-shift workers and other individuals who are increasingly exposed to LEN.

HER2 confers drug resistance of human breast cancer cells through activation of NRF2 by direct interaction

Overexpression and/or activation of HER2 confers resistance of cancer cells to chemotherapeutic drugs. NRF2 also gives drug resistance of cancer cells through induction of detoxification and/or drug efflux proteins. Although several upstream effectors of NRF2 overlapped with the downstream molecules of HER2 pathway, no direct link between HER2 and NRF2 has ever been established. Here, we identified that co-expression of a constitutively active HER2 (HER2CA) and NRF2 increased the levels of NRF2 target proteins, HO-1 and MRP5. We also identified HER2CA activated the DNA-binding of NRF2 and the antioxidant response element (ARE)-mediated transcription in an NRF2-dependent manner. In addition, NRF2 and HER2CA cooperatively up-regulated the mRNA expression of various drug-resistant and detoxifying enzymes including GSTA2, GSTP1, CYP3A4, HO-1, MRP1, and MRP5. We also demonstrated that NRF2 binds to HER2 not only in transiently transfected HEK293T cells but also in HER2-amplified breast cancer cells. Functionally, overexpression of HER2CA gave resistance of MCF7 breast cancer cells to either paraquat or doxorubicin. Overexpression of dominant negative NRF2 (DN-NRF2) reduced the HER2CA-induced resistance of MCF7 cells to these agents. Taken together, these results suggest that active HER2 binds and regulates the NRF2-dependent transcriptional activation and induces drug resistance of cancer cells.

2,3,7,8-Tetrachlorodibenzo-p-dioxin induced cell-specific drug transporters with acquired cisplatin resistance in cisplatin sensitive cancer cells

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can induce drug transporter genes such as the ATP-binding cassette G member 2 (ABCG2), which contributes to multidrug resistance. We investigated the effect of TCDD pretreatment on drug transporters induction from cancer cells of various origins. Cell viabilities after treatment of cisplatin were measured to evaluate acquiring cisplatin resistance by TCDD. Acquring cisplatin resistance was found only in cisplatin senstivie cancer cells including gastric SNU601, colon LS180, brain CRT-MG and lymphoma Jurkat cells which showed a significant increase in cell viability after combined treatment with TCDD and cisplatin. High increase of ABCG2 gene expression was found in SNU601 and LS180 cells with a mild increase in the expression of the ABCC3, ABCC5,and SLC29A2 genes in SNU601 cells, and of major vault protein (MVP) in LS180 cells. The AhR inhibitor kaempferol suppressed the upregulation of ABCG2 expression and reversed the TCDD-induced increase in cell viability in LS180 cells. However, in CRT-MG cells, other transporter genes including ABCC1, ABCC5, ABCA3, ABCA2, ABCB4, ABCG1, and SLC29A1 were up-regulated. These findings suggested the acquiring cisplatin resistance by TCDD associated with cancer cell-type-specific induction of drug transporters.

Deconstructing breast cancer cell biology and the mechanisms of multidrug resistance

Cancer complexity constantly challenges the way that clinicians manage breast cancer therapy. Tumor heterogeneity and intratumoral stroma characteristics allow cells with different phenotypes and deregulated apoptotic, proliferative and migration abilities to co-exist contributing to a disappointing therapeutic response. While new approaches are being associated with conventional chemotherapy, such as hormonal therapy or target monoclonal antibodies, recurrence and metastasization are still observed. Membrane transporters are the cell's first line of contact with anticancer drugs having a major role in multidrug resistance events. This structural-based activity enables the cell to be drug-resistant by decreasing drug intracellular concentration through an efflux-transport mechanism, mainly associated with overexpression of ATP-binding cassette (ABC) proteins. This review focuses on some of the important structural and biological properties of the malignant cell and tumor microenvironment, addressing the role of the membrane ABC transporters in therapeutic outcomes, and highlighting related molecular pathways that may represent meaningful target therapies.

Sensitization of U937 leukemia cells to doxorubicin by the MG132 proteasome inhibitor induces an increase in apoptosis by suppressing NF-kappa B and mitochondrial membrane potential loss

Background

The resistance of cancerous cells to chemotherapy remains the main limitation for cancer treatment at present. Doxorubicin (DOX) is a potent antitumor drug that activates the ubiquitin-proteasome system, but unfortunately it also activates the Nuclear factor kappa B (NF-кB) pathway leading to the promotion of tumor cell survival. MG132 is a drug that inhibits I kappa B degradation by the proteasome-avoiding activation of NF-кB. In this work, we studied the sensitizing effect of the MG132 proteasome inhibitor on the antitumor activity of DOX.

Methods

U937 human leukemia cells were treated with MG132, DOX, or both drugs. We evaluated proliferation, viability, apoptosis, caspase-3, -8, and −9 activity and cleavage, cytochrome c release, mitochondrial membrane potential, the Bcl-2 and Bcl-XL antiapoptotic proteins, senescence, p65 phosphorylation, and pro- and antiapoptotic genes.

Results

The greatest apoptosis percentage in U937 cells was obtained with a combination of MG132 + DOX. Likewise, employing both drugs, we observed a decrease in tumor cell proliferation and important caspase-3 activation, as well as mitochondrial membrane potential loss. Therefore, MG132 decreases senescence, p65 phosphorylation, and the DOX-induced Bcl-2 antiapoptotic protein. The MG132 + DOX treatment induced upregulation of proapoptotic genes BAX, DIABLO, NOXA, DR4, and FAS. It also induced downregulation of the antiapoptotic genes BCL-XL and SURVIVIN.

Conclusion

MG132 sensitizes U937 leukemia cells to DOX-induced apoptosis, increasing its anti-leukemic effectiveness.

The role of the dysfunctional akt-related pathway in cancer: establishment and maintenance of a malignant cell phenotype, resistance to therapy, and future strategies for drug development

Akt serine/threonine kinases, or PKB, are key players in the regulation of a wide variety of cellular activities, such as growth, proliferation, protection from apoptotic injuries, control of DNA damage responses and genome stability, metabolism, migration, and angiogenesis. The Akt-related pathway responds to the stimulation mediated by growth factors, cytokines, hormones, and several nutrients. Akt is present in three isoforms: Akt1, Akt2, and Akt3, which may be alternatively named PKB α , PKB β , and PKB γ , respectively. The Akt isoforms are encoded on three diverse chromosomes and their biological functions are predominantly distinct. Deregulations in the Akt-related pathway were observed in many human maladies, including cancer, cardiopathies, neurological diseases, and type-2 diabetes. This review discusses the significance of the abnormal activities of the Akt axis in promoting and sustaining malignancies, along with the development of tumor cell populations that exhibit enhanced resistance to chemo- and/or radiotherapy. This occurrence may be responsible for the relapse of the disease, which is unfortunately very often related to fatal consequences in patients.

STAT3 activation in HER2-overexpressing breast cancer promotes epithelial-mesenchymal transition and cancer stem cell traits

Clinically, HER2 proto-oncogene amplification is found in about 25–30% of human breast cancers, where it is correlated to a poor prognosis. Constitutive STAT3 activation is found in about 50–60% of the breast tumors and associated with tumorigenesis and drug resistance. In this study, we showed that STAT3 was phosphorylated in HER2-overexpressing, ER-positive human breast tumors and, furthermore, phosphorylated STAT3 promoted the stem-like cell phenotype. We examined the dysregulation of the stem cell markers (Oct-4, Sox-2 and CD44) and the tumorsphere formation in HER2-overexpressing human breast cancer cell lines. We demonstrated that the STAT3 inhibitor, Stattic, treatment abolished the cancer stem cell phenotype in HER2-positive breast cancers. Combined treatment of Herceptin and Stattic showed the synergistic effect on the cancer cell growth in vitro. In addition, when the STAT3 gene was knocked down, the expression of the stem cell markers Oct-4, Sox-2 and CD44 were downregulated and tumorsphere formation was abolished. HER2-elicited STAT3 signaling may provide a potential model for drug resistance induced by stem-like cell characteristics. This mechanism may be responsible for acquiring resistance to Herceptin in the treatment of HER2-overexpressing breast tumors. Based on our findings, targeting pSTAT3 could overcome Herceptin-induced resistance in HER2-overexpressing breast tumors.

Expression of the breast cancer resistance protein and 5-fluorouracil resistance in clinical breast cancer tissue specimens

The breast cancer resistance protein (BCRP) is a recently characterized xenobiotic half-transporter protein that acts as an energy-dependent efflux pump and may be associated with the multidrug-resistant phenotype. The aim of this study was to determine the association between BCRP expression and 5-fluorouracil (5-FU) resistance in clinical breast cancer tissue specimens. The BCRP expression was investigated using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) by use of the Master SYBR-Green I reagent and immunohistochemistry (IHC) by use of the BXP-21 anti-BCRP monoclonal antibody in clinical breast cancer tissue specimens. Chemosensitivity to 5-FU for BCRP-positive clinical breast cancer tissue specimens was colorimetrically assessed with the cytotoxicity assay through methyl thiazolyl tetrazolium (MTT) reduction. A total of 37 BCRP-positive clinical breast cancer tissue specimens were identified with quantitative RT-PCR and IHC. There was a significant correlation in BCRP expression between the results of quantitative RT-PCR and IHC in the specimens. The fold resistance to 5-FU was 7–12 compared to sensitivity to paclitaxel as determined by the colorimetric assay through MTT reduction in the 37 specimens. Our study results indicated that 5-FU resistance may be mediated by BCRP expression in clinical breast cancer tissue specimens, which may help optimize the design of breast cancer clinical chemotherapy schemes in BCRP-positive specimens.

Establishment of paclitaxel-resistant breast cancer cell line and nude mice models, and underlying multidrug resistance mechanisms in vitro and in vivo

BACKGROUND

Breast cancer is a common malignant tumor which affects health of women and multidrug resistance (MDR) is one of the main factors leading to failure of chemotherapy. This study was conducted to establish paclitaxel-resistant breast cancer cell line and nude mice models to explore underlying mechanisms of MDR.

METHODS

The breast cancer drug-sensitive cell line MCF-7 (MCF-7/S) was exposed in stepwise escalating paclitaxel (TAX) to induce a resistant cell line MCF-7/TAX. Cell sensitivity to drugs and growth curves were measured by MTT assay. Changes of cell morphology and ultrastructure were examined by optical and electron microscopy. The cell cycle distribution was determined by flow cytometry. Furthermore, expression of proteins related to breast cancer occurrence and MDR was tested by immunocytochemistry. In Vivo, nude mice were injected with MCF-7/S and MCF-7/TAX cells and weights and tumor sizes were observed after paclitaxel treatment. In addition, proteins involved breast cancer and MDR were detected by immunohistochemistry.

RESULTS

Compared to MCF-7/S, MCF-7/TAX cells had a higher resistance to paclitaxel, cross-resistance and prolonged doubling time. Moreover, MCF-7/TAX showed obvious alterations of ultrastructure. Estrogen receptor (ER) expression was low in drug resistant cells and tumors while expression of human epidermal growth factor receptor 2 (HER2) and Ki-67 was up-regulated. P-glycoprotein (P-gp), lung resistance-related protein (LRP) and glutathione-S-transferase-π (GST-π) involved in the MDR phenotype of resistant cells and tumors were all overexpressed.

CONCLUSION

The underlying MDR mechanism of breast cancer may involve increased expression of P-gp, LRP and GST-π.

The importance of HER2 signaling in the tumor-initiating cell population in aromatase inhibitor-resistant breast cancer

Aromatase inhibitors (AIs) are an effective therapy in treating estrogen receptor-positive breast cancer. Nonetheless, a significant percentage of patients either do not respond or become resistant to AIs. Decreased dependence on ER-signaling and increased dependence on growth factor receptor signaling pathways, particularly human epidermal growth factor receptor 2 (EGFR2/HER2), have been implicated in AI resistance. However, the role of growth factor signaling remains unclear. This current study investigates the possibility that signaling either through HER2 alone or through interplay between epidermal growth factor receptor 1 (EGFR/HER1) and HER2 mediates AI resistance by increasing the tumor initiating cell (TIC) subpopulation in AI-resistant cells via regulation of stem cell markers, such as breast cancer resistance protein (BCRP). TICs and BCRP are both known to be involved in drug resistance. Results from in vitro analyses of AI-resistant versus AI-sensitive cells and HER2-versus HER2+ cells, as well as from in vivo xenograft tumors, indicate that (1) AI-resistant cells overexpress both HER2 and BCRP and exhibit increased TIC characteristics compared to AI-sensitive cells; (2) inhibition of HER2 and/or BCRP decrease TIC characteristics in letrozole-resistant cells; and (3) HER2 and its dimerization partner EGFR/HER1 are involved in the regulation of BCRP. Overall, these results suggest that reducing or eliminating the TIC subpopulation with agents that target BCRP, HER2, EGFR/HER1, and/or their downstream kinase pathways could be effective in preventing and/or treating acquired AI resistance.

Saracatinib (AZD0530) is a potent modulator of ABCB1-mediated multidrug resistance in vitro and in vivo

Saracatinib, a highly selective, dual Src/Abl kinase inhibitor, is currently in a Phase II clinical trial for the treatment of ovarian cancer. In our study, we investigated the effect of saracatinib on the reversal of multidrug resistance (MDR) induced by ATP-binding cassette (ABC) transporters in vitro and in vivo. Our results showed that saracatinib significantly enhanced the cytotoxicity of ABCB1 substrate drugs in ABCB1 overexpressing HeLa/v200, MCF-7/adr and HEK293/ABCB1 cells, an effect that was stronger than that of gefitinib, whereas it had no effect on the cytotoxicity of the substrates in ABCC1 overexpressing HL-60/adr cells and its parental sensitive cells. Additionally, saracatinib significantly increased the doxorubicin (Dox) and Rho 123 accumulation in HeLa/v200 and MCF-7/adr cells, whereas it had no effect on HeLa and MCF-7 cells. Furthermore, saracatinib stimulated the ATPase activity and inhibited photolabeling of ABCB1 with [(125)I]-iodoarylazidoprazosin in a concentration-dependent manner. In addition, the homology modeling predicted the binding conformation of saracatinib within the large hydrophobic drug-binding cavity of human ABCB1. However, neither the expression level of ABCB1 nor the phosphorylation level of Akt was altered at the reversal concentrations of saracatinib. Importantly, saracatinib significantly enhanced the effect of paclitaxel against ABCB1-overexpressing HeLa/v200 cancer cell xenografts in nude mice. In conclusion, saracatinib reverses ABCB1-mediated MDR in vitro and in vivo by directly inhibiting ABCB1 transport function, without altering ABCB1 expression or AKT phosphorylation. These findings may be helpful to attenuate the effect of MDR by combining saracatinib with other chemotherapeutic drugs in the clinic.

A new hypothesis for the cancer mechanism

Several observations have led us to a new hypothesis for cancer mechanism. First, that cancer appears only on those multicellular organisms with complicated wound-healing capacities. Second, that wounds considered as risk factors can be identified in all cancers in clinics. And finally, that oncogene activation appears not only in cancer, but also in normal physiology and noncancer pathology processes. Our proposed hypothesis is that cancer is a natural wound healing-related process, which includes oncogene activations, cytokine secretions, stem cell recruitment differentiation, and tissue remodeling. Wounds activate oncogenes of some cells and the latter secrete cytokines to recruit stem cells to heal the wounds. However, if the cause of the wound or if the wound persists, such as under the persistent UV and carcinogen exposures, the continuous wound healing process will lead to a clinical cancer mass. There is no system in nature to stop or reverse the wound healing process in the middle stage when the wound exists. The outcome of the cancer mechanism is either healing the wound or exhausting the whole system (death). The logic of this cancer mechanism is consistent with the rationales of the other physiological metabolisms in the body-for survival. This hypothesis helps to understand many cancer mysteries derived from the mutation theory, such as why cancer only exists in a small proportion of multicellular organisms, although they are all under potential mutation risks during DNA replications. The hypothesis can be used to interpret and guide cancer prevention, recurrence, metastasis, in vitro and in vivo studies, and personalized treatments.

Role of breast cancer resistance protein (BCRP/ABCG2) in cancer drug resistance

Since cloning of the ATP-binding cassette (ABC) family member breast cancer resistance protein (BCRP/ABCG2) and its characterization as a multidrug resistance efflux transporter in 1998, BCRP has been the subject of more than two thousand scholarly articles. In normal tissues, BCRP functions as a defense mechanism against toxins and xenobiotics, with expression in the gut, bile canaliculi, placenta, blood-testis and blood-brain barriers facilitating excretion and limiting absorption of potentially toxic substrate molecules, including many cancer chemotherapeutic drugs. BCRP also plays a key role in heme and folate homeostasis, which may help normal cells survive under conditions of hypoxia. BCRP expression appears to be a characteristic of certain normal tissue stem cells termed "side population cells," which are identified on flow cytometric analysis by their ability to exclude Hoechst 33342, a BCRP substrate fluorescent dye. Hence, BCRP expression may contribute to the natural resistance and longevity of these normal stem cells. Malignant tissues can exploit the properties of BCRP to survive hypoxia and to evade exposure to chemotherapeutic drugs. Evidence is mounting that many cancers display subpopulations of stem cells that are responsible for tumor self-renewal. Such stem cells frequently manifest the "side population" phenotype characterized by expression of BCRP and other ABC transporters. Along with other factors, these transporters may contribute to the inherent resistance of these neoplasms and their failure to be cured.

A marine anthraquinone SZ-685C overrides adriamycin-resistance in breast cancer cells through suppressing Akt signaling

Breast cancer remains a major health problem worldwide. While chemotherapy represents an important therapeutic modality against breast cancer, limitations in the clinical use of chemotherapy remain formidable because of chemoresistance. The HER2/PI-3K/Akt pathway has been demonstrated to play a causal role in conferring a broad chemoresistance in breast cancer cells and thus justified to be a target for enhancing the effects of anti-breast cancer chemotherapies, such as adriamycin (ADR). Agents that can either enhance the effects of chemotherapeutics or overcome chemoresistance are urgently needed for the treatment of breast cancer. In this context, SZ-685C, an agent that has been previously shown, as such, to suppress Akt signaling, is expected to increase the efficacy of chemotherapy. Our current study investigated whether SZ-685C can override chemoresistance through inhibiting Akt signaling in human breast cancer cells. ADR-resistant cells derived from human breast cancer cell lines MCF-7, MCF-7/ADR and MCF-7/Akt, were used as models to test the effects of SZ-685C. We found that SZ-685C suppressed the Akt pathway and induced apoptosis in MCF-7/ADR and MCF-7/Akt cells that are resistant to ADR treatment, leading to antitumor effects both in vitro and in vivo. Our data suggest that use of SZ-685C might represent a potentially promising approach to the treatment of ADR-resistant breast cancer.

14-3-3σ regulation by p53 mediates a chemotherapy response to 5-fluorouracil in MCF-7 breast cancer cells via Akt inactivation

We previously demonstrated that 14-3-3σ was downregulated in 5-fluorouracil (5-Fu)-resistant MCF-7 breast cancer cells (MCF-7/5-Fu). Here, we found that stably enhanced 14-3-3σ expression strengthened the effects of 5-Fu, Mitoxantrone and cDDP. 14-3-3σ stabilised the p53 protein and bound Akt to inhibit its activity and its downstream targets: survivin, Bcl-2 and NF-κB-p50. In addition, decreased p53 expression, but not promoter hypermethylation, was responsible for the downregulation of 14-3-3σ in MCF-7/5-Fu cells. Meanwhile, initial treatments with high concentrations of 5-Fu clearly induced 14-3-3σ and p53 expression in a time-dependent manner. 14-3-3σ-mediated molecular events that synergise with p53 may play important roles in the chemotherapy of breast cancer.