• Molecules and Cells
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• 제45권10호
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• pp.729-737
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• 2022

Carboplatin-based chemotherapy is the primary treatment option for the management of retinoblastoma, an intraocular malignant tumor observed in children. The aim of the present study was to establish carboplatin-resistant retinoblastoma cell lines to facilitate future research into the treatment of chemoresistant retinoblastoma. In total, two retinoblastoma cell lines, Y79 and SNUOT-Rb1, were treated with increasing concentrations of carboplatin to develop the carboplatin-resistant retinoblastoma cell lines (termed Y79/CBP and SNUOT-Rb1/CBP, respectively). To verify resistance to carboplatin, the degree of DNA fragmentation and the expression level of cleaved caspase-3 were evaluated in the cells, following carboplatin treatment. In addition, the newly developed carboplatin-resistant retinoblastoma cells formed in vivo intraocular tumors more effectively than their parental cells, even after the intravitreal injection of carboplatin. Interestingly, the proportion of cells in the G₀/G₁ phase was higher in Y79/CBP and SNUOT-Rb1/CBP cells than in their respective parental cells. In line with these data, the expression levels of cyclin D1 and cyclin D3 were decreased, whereas p18 and p27 expression was increased in the carboplatin-resistant cells. In addition, the expression levels of genes associated with multidrug resistance were increased. Thus, these carboplatin-resistant cell lines may serve as a useful tool in the study of chemoresistance in retinoblastoma and for the development potential therapeutics.

• BMB Reports
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• 제56권6호
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• pp.347-352
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• 2023

The protein family of poly (ADP-ribose) polymerases (PARPs) is comprised of multifunctional nuclear enzymes. Several PARP inhibitors have been developed as new anticancer drugs to combat resistance to chemotherapy. Herein, we characterized PARP4 mRNA expression profiles in cisplatin-sensitive and cisplatin-resistant ovarian cancer cell lines. PARP4 mRNA expression was significantly upregulated in cisplatin-resistant ovarian cancer cell lines, and this upregulation was associated with the hypomethylation of specific cytosine-phosphate-guanine (CpG) sites (cg18582260 and cg17117459) on its promoter. Reduced PARP4 expression was restored by treating cisplatin-sensitive cell lines with a demethylation agent, implicating the epigenetic regulation of PARP4 expression by promoter methylation. Depletion of PARP4 expression in cisplatin-resistant cell lines reduced cisplatin chemoresistance and promoted cisplatin-induced DNA fragmentation. The differential mRNA expression and DNA methylation status at specific PARP4 promoter CpG sites (cg18582260 and cg17117459) according to cisplatin responses, was further validated in primary ovarian tumor tissues. The results showed significantly increased PARP4 mRNA expressions and decreased DNA methylation levels at specific PARP4 promoter CpG sites (cg18582260 and cg17117459) in cisplatin-resistant patients. Additionally, the DNA methylation status at cg18582260 CpG sites in ovarian tumor tissues showed fairly clear discrimination between cisplatin-resistant patients and cisplatin-sensitive patients, with high accuracy (area under the curve = 0.86, P = 0.003845). Our findings suggest that the DNA methylation status of PARP4 at the specific promoter site (cg18582260) may be a useful diagnostic biomarker for predicting the response to cisplatin in ovarian cancer patients.

• 생명과학회지
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• 제26권11호
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• pp.1313-1319
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• 2016

암은 비균질적으로 구성된 세포집합체로 간질세포 및 세포 외 기질로 구성된 미세환경과 상호작용에 의해 발병, 전이, 심화되는 복잡한 질병이다. 하지만, 기존의 2차원 배양 세포 기반 플랫폼이 3차원적 생체 환경과 암의 비균질성을 대표하기 힘든 한계를 극복하기 위해 스페로이드 배양 세포를 비롯한 다양한 플랫폼 개발이 활발해지고 있다. 본 연구에서는 특히 감염, 염증 및 식이적 환경성 영향력에 민감한 HCT-8 대장암 세포주를 기반으로 하여 3차원 스페로이드 배양법을 보다 효과적인 방법으로 개선하고, 대장암 스페로이드 세포를 기반으로 암의 비균질적인 특질과 항암내성 연구의 간단하고 개선된 플랫폼을 제시고자 하였다. 3차원 배양법 최적화를 위해 물리적 배양환경 조성과 배양배지 구성에 따른 스페로이드 형태형성을 비교 분석하고 암 줄기세포군의 증가 양상을 확인한 결과, 필수요소로 구성된 제한 배지와 균일한 형태의 비부착성 표면 배양접시에서 배양된 스페로이드가 균일한 형태의 구형을 형성하고 암 줄기세포군이 증가함을 확인하였다. 대장암 스페로이드 세포를 기반으로 대장암 치료제인 5-Fluorouracil (5-FU)에 대한 화학적 감응성 변화를 측정한 결과, 암 줄기세포가 5-FU에 대한 화학적 감수성 저해의 원인이 되며, 최적배양 조건에서 암 줄기세포의 약제 내성의 표현이 증대되었다. 이는 암줄기세포의 항암제 내성에 대한 잠재적 위험성을 내포하는 것으로, 이 방법론은 감염, 염증 및 식이적 요인과 연관된 대장암 스페로이드 세포 기반 항암제 약물반응을 검증하기 위해 효과적이면서 간소한 시험법으로 활용될 수 있을 것이다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권8호
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• pp.3577-3581
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• 2012

Small cell lung cancer (SCLC) is characterized by a short cell doubling time, rapid progression and early occurrence of blood-borne and lymph metastasis. The malignancy is the highest of all lung cancer types. Although SCLC has a relatively good initial response to chemotherapy as well as radiotherapy, relapse or disease progression may occur quickly after the initial treatment. Drug resistance, especially multi-drug resistance, is the most important cause of failure of SCLC chemotherapy. This article provides a brief update of research on mechanisms of drug resistance in SCLC and reversal strategies.

• Journal of Pharmaceutical Investigation
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• 제37권5호
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• pp.287-290
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• 2007

Intrinsic or acquired resistance to chemotherapeutic drugs is one of the major obstacles to effective cancer treatment. Hypoxia is widespread in solid tumors as a consequence of decreased blood flow in the tumor-derived neovasculature. The recent finding of a link between hypoxia and chemoresistance prompted us to investigate whether hypoxia induces doxorubicin resistance in human MCF-7 breast cancer cells. Low oxygen concentration decreased the doxorubicin sensitivity in MCF-7 cells. The expression of p-glycoprotein, a major MDR-related transporter, and those of apoptosis-related proteins (anti-apoptotic Bcl-2, Bcl-XL and pro-apoptotic Bax) were not altered by hypoxia in MCF-7 cells. Intracellular uptake of doxorubicin was significantly decreased under hypoxic conditions. Decreased cellular uptake of doxorubicin under hypoxia may contribute to causing doxorubicin resistance in these cells. The use of agents that can modulate the doxorubicin uptake for adjuvant therapy may contribute to improving the therapeutic efficacy of doxorubicin in breast cancer patients.

• Asian Pacific Journal of Cancer Prevention
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• 제15권23호
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• pp.10439-10444
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• 2015

Many chemotherapeutic agents have been successfully used to treat hepatocellular carcinoma (HCC); however, the development of chemoresistance in liver cancer cells usually results in a relapse and worsening of prognosis. It has been demonstrated that DNA methylation and histone modification play crucial roles in chemotherapy resistance. Currently, extensive research has shown that there is another potential mechanism of gene expression control, which is mediated through the function of short noncoding RNAs, especially for microRNAs (miRNAs), but little is known about their roles in cancer cell drug resistance. In present study, by taking advantage of miRNA effects on the resistance of human hepatocellular carcinoma cells line to cisplatin, it has been demonstrated that miR-340 were significantly downregulated whereas Nrf2 was upregulated in HepG2/CDDP (cisplatin) cells, compared with parental HepG2 cells. Bioinformatics analysis and luciferase assays of Nrf2-3'-untranslated region-based reporter constructor indicated that Nrf2 was the direct target gene of miR-340, miR-340 mimics suppressing Nrf2-dependent antioxidant pathway and enhancing the sensitivity of HepG2/CDDP cells to cisplatin. Interestingly, transfection with miR-340 mimics combined with miR-340 inhibitors reactivated the Nrf2 related pathway and restored the resistance of HepG2/CDDP cells to CDDP. Collectively, the results first suggested that lower expression of miR-340 is involved in the development of CDDP resistance in hepatocellular carcinoma cell line, at least partly due to regulating Nrf2-dependent antioxidant pathway.

• Asian Pacific Journal of Cancer Prevention
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• 제15권1호
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• pp.17-24
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• 2014

Gastric cancer is highly invasive, aggressively malignant, and amongst the most prevalent of all forms of cancer. Despite improved management strategies, early stage diagnosis of gastric cancer and accurate prognostic assessment is still lacking. Several recent reports have indicated that the pathogenesis of gastric cancer involves complex molecular mechanisms and multiple genetic and epigenetic alterations in oncogenes and tumor suppressor genes. Functional inactivation of the tumor suppressor protein PTEN (Phosphatase and Tensin Homolog) has been detected in multiple cases of gastric cancer, and already shown to be closely linked to the development, progression and prognosis of the disease. Inactivation of PTEN can be attributed to gene mutation, loss of heterozygosity, promoter hypermethylation, microRNA- mediated regulation of gene expression, and post-translational phosphorylation. PTEN is also involved in mechanisms regulating tumor resistance to chemotherapy. This review provides a comprehensive analysis of PTEN and its roles in gastric cancer, and emphasizes its potential benefits in early diagnosis and gene therapy-based treatment strategies.

• Journal of Microbiology and Biotechnology
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• 제27권8호
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• pp.1367-1378
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• 2017

Epigenetic alterations such as DNA methylation, histone acetylation, and chromatin remodeling can control gene expression by regulating gene transcription. DNA methylation is one of the frequent epigenetic events that play important roles in cancer development. Cancer cells can gain significant resistance to anticancer drugs and escape programmed cell death through major epigenetic changes, including DNA methylation. To date, several research groups have identified instances of both (i) hypermethylation of tumor suppressor genes, and (ii) global hypomethylation of oncogenes. These changes in DNA methylation status could be used as biomarkers for the diagnosis and prognosis of cancer patients undergoing chemotherapies or other clinical therapies. Herein, we describe genes for which methylation is dependent upon anticancer drug resistance in patients with gastric cancer; we then suggest a significant epigenetic target to focus on for overcoming anticancer drug resistance.

• 약학회지
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• 제52권1호
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• pp.67-72
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• 2008

The use of doxorubicin, which is one of the most effective anticancer agents, is often limited by occurrence of acquired resistance in tumor cells. GSH has been shown to be involved in the development of this drug resistance. Transcription factor Nrf2 governs the expression of GSH synthesizing glutamylcysteine ligase (GCL), as well as multiple phase 2 detoxifying enzymes. Here we show that Nrf2 is one of factors determining doxorubicin sensitivity. Nrf2-deficient fibroblasts (murine embryonic fibroblasts, MEF) were more susceptible to doxorubicin mediated cell death than wild-type cells. Doxorubicin treatment elevated levels of Nrf2-regulated genes including NAD(P)H: quinone oxidoreductase (Nqo1) and GCL in wild-type fibroblasts, while no induction was observed in Nrf2-deficient cells. Doxorubicin resistance in human ovarian SK-OV cells was reversed by treatment with L-buthionine-sulfoxamine (BSO), which is depleting intracellular GSH. Finally, transfection of SK-OV cells with Nrf2 siRNA resulted in exacerbated cytotoxicity following doxorubicin treatment compared to scrambled RNA control. These results indicate that the Nrf2 pathway, which plays a protective role in normal cells, can be a potential target to control cancer cell resistance to anticancer agents.

• Journal of Pharmaceutical Investigation
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• 제36권4호
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• pp.231-237
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• 2006

Hypoxia in solid tumors is known to contribute to intrinsic chemoresistance. Histocultures are in vitro 3 dimensional cultures of tumor tissues and maintain the characteristic microenvironment of human solid tumors in vivo including hypoxia and multicellular structure. In this study, we evaluated the pharmacodynamics of tirapazamine(TPZ), a hypoxia-selective cytotoxin, in human non small cell lung cancer(NSCLC) cells grown as monolayers and histocultures. Antiproliferative activity of TPZ was determined after various conditions of drug exposure, and cell cycle arrest and apoptosis were also measured using flow cytometry. In monolayers, hypoxia selectivity measured by hypoxic/normoxic cytotoxicity ratio was increased with longer exposure. Lower cytotoxicity of TPZ was observed in histocultures compared to monolayers, however, a similar level of cytotoxicity was obtained with longer exposure of 96 hr. TPZ induced $G_2/M$ arrest and apoptosis in both culture conditions, which were greatly enhanced under hypoxic condition. Our data clearly showed the different pharmacodynamics of TPZ in monolayers and histocultures. Antiproliferative activity of TPZ against human solid tumors can be improved with longer drug exposure by exploiting drug delivery systems or by combining angiogenesis inhibitors to maintain drug concentration in tumor tissues.