• Archives of Pharmacal Research
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• v.29 no.11
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• pp.1018-1023
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• 2006

Chemoresistance remains the major obstacle to successful therapy of cancer. In order to understand the mechanism of multidrug resistance (MDR) that is frequently observed in lung cancer patients, here we studied the contribution of MDR-related proteins by establishing lung cancer cell lines with acquired resistance against etoposide. We found that human H460 lung cancer cells responded to etoposide more sensitively than A549 cells. Among MDR-related proteins, the expression of p-glycoprotein (Pgp) and lung resistance protein (LRP) were much higher in A549 cells compared with that in H460 cells. When we established H460-R1 and -R2 cell lines by progressive exposure of H460 cells to increasing doses of etoposide, the response against etopbside as well as doxorubicin was greatly reduced in R1 and R2 cells, suggesting MDR induction. Induction of MDR was not accompanied by a decrease in the intracellular accumulation of etoposide and the expression of MDR-related proteins that function as drug efflux pumps such as Pgp and MRP1 was not changed. We found that the acquired resistance paralleled an increased expression of LRP in H460 cells. Taken together, our data suggest the implicative role of LRP in mediating MDR in lung cancer.

• Biomedical Science Letters
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• v.27 no.3
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• pp.134-141
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• 2021

c-Jun N-terminal kinases (JNKs) have a Janus face, regulating both cell apoptosis and survival. The present study focused on understanding the function of JNK in tumor development and the chemoresistance underlying JNK-mediated cancer cell survival. We identified an inhibitor of JNK1, an important regulator of cancer cell survival. Kinase assay data showed that JNK1-dependent c-Jun phosphorylation was inhibited by indirubin derivatives. In particular, indirubin-3-monoxime (I3M) directly inhibited the phosphorylation of c-Jun in vitro, with a half inhibition dose (IC₅₀) of 10 nM. I3M had a significant inhibitory effect on JNK1 activity. Furthermore, we carried out assays to determine the viability, migration, and proliferation of breast cancer cells. Our results demonstrated that cell growth, scratched wound healing, and colony forming abilities were inhibited by the JNK inhibitor SP600125 and I3M. The combination of SP600125 and I3M significantly decreased cancer cell proliferation, compared with either SP600125 or I3M alone. Our studies may provide further support for JNK1-targeting cancer therapy using the indirubin derivative I3M in breast cancer.

• The Korean Journal of Physiology and Pharmacology
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• v.27 no.1
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• pp.21-29
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• 2023

The poor outcome of advanced ovarian cancer under conventional therapy necessitates new strategies to improve therapeutic efficacy. β-glucosidase (encoded by GBA) is a lysosomal enzyme and is involved in sphingolipids metabolism. Recent studies revealed that β-glucosidase plays a role in cancer development and chemoresistance. In this work, we systematically evaluated the expression and role of GBA in ovarian cancer. Our work demonstrates that inhibition of β-glucosidase has therapeutic potential for ovarian cancer. Gene Expression Profiling Interactive Analysis database, western blot and immunohistochemistry analyses of patient samples demonstrated that GBA mRNA and protein expression levels were significantly increased in ovarian cancer compared to normal tissues. Functional studies using gainof-function and loss-of-function approaches demonstrated that GBA overexpression did not affect growth and migration but alleviated cisplatin's efficacy in ovarian cancer cells. In addition, GBA depletion resulted in growth inhibition, apoptosis induction, and enhancement of cisplatin's efficacy. Of note, we found that GBA inhibition specifically decreased receptor tyrosine kinase AXL level, leading to the suppression of AXL-mediated signaling pathways. Our data suggest that GBA represents a promising target to inhibit AXL signaling and overcome cisplatin resistance in ovarian cancer.

• Anatomy and Cell Biology
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• v.56 no.1
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• pp.94-108
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• 2023

Cancer cell heterogeneity is a serious problem in the control of tumor progression because it can cause chemoresistance and metastasis. Heterogeneity can be generated by various mechanisms, including genetic evolution of cancer cells, cancer stem cells (CSCs), and niche heterogeneity. Because the genetic heterogeneity of CSCs has been poorly characterized, the genetic mutation status of CSCs was examined using Exome-Seq and RNA-Seq data of liver cancer. Here we show that different surface markers for liver cancer stem cells (LCSCs) showed a unique propensity for genetic mutations. Cluster of differentiation 133 (CD133)-positive cells showed frequent mutations in the IRF2, BAP1, and ERBB3 genes. However, leucine-rich repeat-containing G protein-coupled receptor 5-positive cells showed frequent mutations in the CTNNB1, RELN, and ROBO1 genes. In addition, some genetic mutations were frequently observed irrespective of the surface markers for LCSCs. BAP1 mutations was frequently observed in CD133-, CD24-, CD13-, CD90-, epithelial cell adhesion molecule-, or keratin 19-positive LCSCs. ASXL2, ERBB3, IRF2, TLX3, CPS1, and NFATC2 mutations were observed in more than three types of LCSCs, suggesting that common mechanisms for the development of these LCSCs. The present study provides genetic heterogeneity depending on the surface markers for LCSCs. The genetic heterogeneity of LCSCs should be considered in the development of LCSC-targeting therapeutics.

• IMMUNE NETWORK
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• v.16 no.2
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• pp.85-98
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• 2016

The mitogen-activated protein kinases (MAPKs) are key regulators of cell growth and survival in physiological and pathological processes. Aberrant MAPK signaling plays a critical role in the development and progression of human cancer, as well as in determining responses to cancer treatment. The MAPK phosphatases (MKPs), also known as dual-specificity phosphatases (DUSPs), are a family of proteins that function as major negative regulators of MAPK activities in mammalian cells. Studies using mice deficient in specific MKPs including MKP1/DUSP1, PAC-1/DUSP2, MKP2/DUSP4, MKP5/DUSP10 and MKP7/DUSP16 demonstrated that these molecules are important not only for both innate and adaptive immune responses, but also for metabolic homeostasis. In addition, the consequences of the gain or loss of function of the MKPs in normal and malignant tissues have highlighted the importance of these phosphatases in the pathogenesis of cancers. The involvement of the MKPs in resistance to cancer therapy has also gained prominence, making the MKPs a potential target for anti-cancer therapy. This review will summarize the current knowledge of the MKPs in cancer development, progression and treatment outcomes.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.16
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• pp.6973-6979
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• 2015

Background: Ovarian cancer is the third most common cause of cancer in Indian women. Despite an initial 70-80% response rate, most patients relapse within 1-2 years and develop chemoresistance. Hence, identification or repositioning of drugs to resensitise ovarian cancer cells to existing chemotherapy is needed. Traditionally immortalized cell lines have been used in research, but these may contain genetic aberrations and chromosomal abnormalities serving as poor indicators of normal cell phenotype and progression of early-stage disease. The use of primary cells, maintained for only short periods of time in vitro, may serve as the best representative for studying in vivo conditions of the tissues from which they are derived. In this study we have attempted to evaluate the effect of metformin (an antidiabetic drug) in primary ovarian cancer cells because of its promising effect in other solid tumours. Materials and Methods: Primary cultures of epithelial ovarian cancer cells established from ascitic fluid of untreated ovarian cancer patients were used. The cells were treated with metformin at doses standardized by MTT assay and its ability to induce apoptosis was studied. The cells were analysed for apoptosis and apoptosis related proteins by flow cytometry and western blotting respectively. Results: Metformin induced apoptosis in ovarian cancer cells, provoking cell cycle arrest in the G0/G1 and S phase. It induced apoptosis in ovarian cancer cells by, down-regulating Bcl-2 and up-regulating Bax expression. Conclusions: Metformin was able to induce apoptosis in primary ovarian cancer cells by modulating the expression of Bcl-2 family proteins. These data are relevant to ongoing translational research efforts exploring the chemotherapeutic potential of metformin.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.9
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• pp.4807-4814
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• 2012

Purpose: The chemoresistance of human hepatocellular carcinoma (HCC) to cytotoxic drugs, especially intrinsic or acquired multidrug resistance (MDR), still remains a major challenge in the management of HCC. In the present study, possible mechanisms involved in MDR of HCC were identified using a 5-fluorouracil (5-FU)-resistant human HCC cell line. Methods: BEL-7402/5-FU cells were established through continuous culturing parental BEL-7402 cells, imitating the pattern of chemotherapy clinically. Growth curves and chemosensitivity to cytotoxic drugs were determined by MTT assay. Doubling times, colony formation and adherence rates were calculated after cell counting. Morphological alteration, karyotype morphology, and untrastructure were assessed under optical and electron microscopes. The distribution in the cell cycle and drug efflux pump activity were measured by flow cytometry. Furthermore, expression of potential genes involved in MDR of BEL-7402/5-FU cells were detected by immunocytochemistry. Results: Compared to its parental cells, BEL-7402/5-FU cells had a prolonged doubling time, a lower mitotic index, colony efficiency and adhesive ability, and a decreased drug efflux pump activity. The resistant cells tended to grow in clusters and apparent changes of ultrastructures occurred. BEL-7402/5-FU cells presented with an increased proportion in S and G2/M phases with a concomitant decrease in G0/G1 phase. The MDR phenotype of BEL-7402/5-FU might be partly attributed to increased drug efflux pump activity via multidrug resistance protein 1 (MRP1), overexpression of thymidylate synthase (TS), resistance to apoptosis by augmentation of the Bcl-xl/Bax ratio, and intracellular adhesion medicated by E-cadherin (E-cad). P-glycoprotein (P-gp) might play a limited role in the MDR of BEL-7402/5-FU. Conclusion: Increased activity or expression of MRP1, Bcl-xl, TS, and E-cad appear to be involved in the MDR mechanism of BEL-7402/5-FU.

• BMB Reports
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• v.45 no.11
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• pp.647-652
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• 2012

We previously reported that MSTO-211H cells have a higher capacity to regulate Nrf2 activation in response to changes in the cellular redox environment. To further characterize its biological significance, the response of Nrf2, a transcription factor that regulates ARE-containing genes, on the synergistic cytotoxic effect of clofarabine and resveratrol was investigated in mesothelioma cells. The combination treatment showed a marked growth-inhibitory effect, which was accompanied by suppression of Nrf2 activation and decreased expression of heme oxygenase-1 (HO-1). While transient overexpression of Nrf2 conferred protection against the cytotoxicity caused by their combination, knockdown of Nrf2 expression using siRNA enhanced their cytotoxic effect. Pretreatment with Ly294002, a PI3K inhibitor, augmented the decrease in HO-1 level by their combination, whereas no obvious changes were observed in Nrf2 levels. Altogether, these results suggest that the synergistic cytotoxic effect of clofarabine and resveratrol was mediated, at least in part, through suppression of Nrf2 signaling.

• Biomolecules & Therapeutics
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• v.22 no.2
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• pp.114-121
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• 2014

Refractoriness of acute myeloid leukemia (AML) cells to chemotherapeutics represents a major clinical barrier. Suicide gene therapy for cancer has been attractive but with limited clinical efficacy. In this study, we investigated the potential application of herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) based system to inhibit chemoresistant AML cells. We first generated Ara-C resistant K562 cells and doxorubicin-resistant THP-1 cells. We found that the HSV-TK/GCV anticancer system suppressed drug resistant leukemic cells in culture. Chemoresistant AML cell lines displayed similar sensitivity to HSV-TK/GCV. Moreover, HSV-TK/GCV killing of leukemic cells was augmented to a mild but significant extent by all-trans retinoic acid (ATRA) with concomitant upregulation of Connexin 43, a major component of gap junctions. Interestingly, HSV-TK/GCV killing was enhanced by expression of vesicular stomatitis virus G glycoprotein (VSV-G), a fusogenic membrane protein, which also increased leukemic cell fusion. Co-culture resistant cells expressing HSV-TK and cells stably transduced with VSV-G showed that expression of VSV-G could promote the bystander killing effect of HSV-TK/GCV. Furthermore, combination of HSV-TK/GCV with VSV-G plus ATRA produced more pronounced antileukemia effect. These results suggest that the HSV-TK/GCV system in combination with fusogenic membrane proteins and/or ATRA could provide a strategy to mitigate the chemoresistance of AML.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.6
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• pp.2979-2984
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• 2012

Recent studies have indicated a link between levels of cyclooxygenase-2 (COX-2) and development of the multidrug resistance (MDR) phenotype. The ATP-binding cassette sub-family G member 2 (ABCG2) is a major MDR-related transporter protein that is frequently overexpressed in cancer patients. In this study, we aimed to evaluate any positive correlation between COX-2 and ABCG2 gene expression using the COX-2 inducer 12-O-tetradecanoylphorbol-13-acetate (TPA) in human breast cancer cell lines. ABCG2 mRNA and protein expression was studied using real-time RT-PCR and flow cytometry, respectively. A significant increase of COX-2 mRNA expression (up to 11-fold by 4 h) was induced by TPA in MDA-MB-231 cells, this induction effect being lower in MCF-7 cells. TPA caused a considerable increase up to 9-fold in ABCG2 mRNA expression in parental MCF-7 cells, while it caused a small enhancement in ABCG2 expression up to 67 % by 4 h followed by a time-dependent decrease in ABCG2 mRNA expression in MDA-MB-231 cells. TPA treatment resulted in a slight increase of ABCG2 protein expression in MCF-7 cells, while a time-dependent decrease in ABCG2 protein expression was occurred in MDA-MB-231 cells. In conclusion, based on the observed effects of TPA in MDA-Mb-231 cells, it is proposed that TPA up-regulates ABCG2 expression in the drug sensitive MCF-7 breast cancer cell line through COX-2 unrelated pathways.