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Xu T, Yan S, Wang M, Jiang L, Ma P, Lu B, Chen Q, Wei C, Wang Z. LncRNA UCA1 Induces Acquired Resistance to Gefitinib by Epigenetically Silencing CDKN1A Expression in Non-small-Cell Lung Cancer. Front Oncol 2020; 10:656. [PMID: 32477939 PMCID: PMC7235350 DOI: 10.3389/fonc.2020.00656] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 04/08/2020] [Indexed: 12/12/2022] Open
Abstract
Lung cancer is the most common cancer globally and is associated with high morbidity and mortality. Gefitinib has been widely used for treating advanced non-small-cell lung cancer (NSCLC). However, acquired resistance usually develops, although we still know little about the mechanism underlying this. In the present study, we found that the lncRNA UCA1 was upregulated in NSCLC tissues and cells with acquired gefitinib resistance, indicating the special role of UCA1 in gefitinib resistance. Knockdown of UCA1 promoted the sensitivity to gefitinib both in vitro and in vivo by suppressing cell proliferation and inducing apoptosis. Moreover, UCA1 could interact with EZH2 (enhancer of zeste homolog 2) to epigenetically reduce the expression of CDKN1A. Taking the obtained findings together, our study suggests that UCA1 is important for NSCLC to develop gefitinib resistance, and is a potential biomarker for gefitinib resistance and a therapeutic target for advanced NSCLC.
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Affiliation(s)
- Tianwei Xu
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Shuai Yan
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China.,Department of Oncology, The Affiliated Jiangyin Hospital of Southeast University Medical College, Jiangyin, China
| | - Mengwei Wang
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Lihua Jiang
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Pei Ma
- Department of Oncology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Binbin Lu
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Qinnan Chen
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Chenchen Wei
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Zhaoxia Wang
- Cancer Medical Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
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Yang Q, Chen W, Xu Y, Lv X, Zhang M, Jiang H. Polyphyllin I modulates MALAT1/STAT3 signaling to induce apoptosis in gefitinib-resistant non-small cell lung cancer. Toxicol Appl Pharmacol 2018; 356:1-7. [DOI: 10.1016/j.taap.2018.07.031] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Revised: 07/18/2018] [Accepted: 07/31/2018] [Indexed: 12/14/2022]
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Furukawa C, Fujii N, Manabe A, Matsunaga T, Endo S, Hasegawa H, Ito Y, Yamaguchi M, Yamazaki Y, Ikari A. Up-Regulation of Transient Receptor Potential Melastatin 6 Channel Expression by Tumor Necrosis Factor-α in the Presence of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor. J Cell Physiol 2017; 232:2841-2850. [DOI: 10.1002/jcp.25709] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 12/01/2016] [Indexed: 01/22/2023]
Affiliation(s)
- Chisa Furukawa
- Laboratory of Biochemistry; Department of Biopharmaceutical Sciences; Gifu Pharmaceutical University; Gifu Japan
| | - Naoko Fujii
- Laboratory of Biochemistry; Department of Biopharmaceutical Sciences; Gifu Pharmaceutical University; Gifu Japan
| | - Aya Manabe
- Laboratory of Biochemistry; Department of Biopharmaceutical Sciences; Gifu Pharmaceutical University; Gifu Japan
| | - Toshiyuki Matsunaga
- Laboratory of Biochemistry; Department of Biopharmaceutical Sciences; Gifu Pharmaceutical University; Gifu Japan
| | - Satoshi Endo
- Laboratory of Biochemistry; Department of Biopharmaceutical Sciences; Gifu Pharmaceutical University; Gifu Japan
| | - Hajime Hasegawa
- Saitama Medical Center; Saitama Medical University; Saitama Japan
| | - Yoshinori Ito
- Department of Pharmacy; Gifu University Hospital; Gifu Japan
| | - Masahiko Yamaguchi
- School of Pharmaceutical Sciences; University of Shizuoka; Shizuoka Japan
| | - Yasuhiro Yamazaki
- School of Pharmaceutical Sciences; University of Shizuoka; Shizuoka Japan
| | - Akira Ikari
- Laboratory of Biochemistry; Department of Biopharmaceutical Sciences; Gifu Pharmaceutical University; Gifu Japan
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Zhou G, Zhang F, Guo Y, Huang J, Xie Y, Yue S, Chen M, Jiang H, Li M. miR-200c enhances sensitivity of drug-resistant non-small cell lung cancer to gefitinib by suppression of PI3K/Akt signaling pathway and inhibites cell migration via targeting ZEB1. Biomed Pharmacother 2016; 85:113-119. [PMID: 27930974 DOI: 10.1016/j.biopha.2016.11.100] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 11/22/2016] [Accepted: 11/22/2016] [Indexed: 01/08/2023] Open
Abstract
Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is a major obstacle in the treatment of non-small cell lung cancer (NSCLC) patients. We explored the role of miR-200c in modulating the sensitivity of gefitinib-resistant NSCLC cells and examined the underlying mechanism. The gefitinib-resistant cell line PC-9-ZD and its parental PC-9 cells were used. Growth inhibition was detected by MTT assay. The cell apoptosis was detected by Annexin V/PI assay. Cell migration was assessed by wound-healing assay. RT-PCR was used to detected levels of miR-200c and ZEB1. The PI3k, Bcl-2, Bax, caspase-3 and ZEB1 protein expression were detected using Western blot analysis, and TUNEL, Immunohistochemistry for xenograft model. PC-9-ZD cells had low level of miR-200c expression compared to its parental PC-9 cells. PC-9-ZD cells with miR-200c transfection were more sensitive to gefitinib treatment. Apoptosis induced by gefitinib was observed in PC-9-ZD cells with miR-200c transfection significantly. The levels of phosphorylated-Akt and Bcl-2 expression decreased and levels of Bax and Caspase-3 expression increased in PC-9-ZD cells with miR-200c transfection. Cell migration was inhibited and ZEB1 mRNA level and protein expression were significantly decreased in PC-9-ZD cells with miR-200c transfection. Further in gefitinib resistant xenograft model, miR-200c enhanced sensitivity of gefitinib and induced apoptosis significantly through PI3K/Akt signaling pathway and targeting ZEB1. These results provided insights into the functions of miR-200c and offered an alternate approach in treating gefitinib-resistance NSCLC.
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Affiliation(s)
- Guohua Zhou
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Fangli Zhang
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Yu Guo
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Jianfei Huang
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Yaqiong Xie
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Shuanglei Yue
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Minghui Chen
- Department of Oncology, Anji People's Hospital, Anji, Zhejiang 313399, PR China
| | - Hao Jiang
- Department of Oncology, Zhejiang Hospital, Hangzhou, Zhejiang 310013, PR China
| | - Mengjie Li
- Department of Hematology, Zhejiang Hospital, Hangzhou, Zhejiang 310013, PR China.
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Lovastatin overcomes gefitinib resistance through TNF-α signaling in human cholangiocarcinomas with different LKB1 statuses in vitro and in vivo. Oncotarget 2016; 6:23857-73. [PMID: 26160843 PMCID: PMC4695157 DOI: 10.18632/oncotarget.4408] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 06/12/2015] [Indexed: 11/25/2022] Open
Abstract
Gefitinib resistance has been shown to complicate cancer therapy. Lovastatin is a proteasome inhibitor that enhances gefitinib-induced antiproliferation in non-small cell lung cancer. The objective of this study is to investigate the mechanism of lovastatin-induced antiproliferation in gefitinib-resistant human cholangiocarcinoma. Two gefitinib-resistant cholangiocarcinoma cell lines, SSP-25 and HuH-28, were used in this study to determine how to compensate gefitinib resistance. The combined effect of these two drugs was examined using the MTT assay, qPCR, immunoblotting, flow cytometry, and in vivo xenograft. Results indicated that lovastatin enhanced TNF-α-induced cell death in vitro. In addition, the combination of lovastatin with gefitinib enhanced accumulation of TNF-α. Furthermore, the treatment induced a synergistic cytotoxic effect and antiproliferation through apoptosis in SSP-25 cells and cell cycle arrest in HuH-28 cells. Reproductive results were also observed in in vivo xenografts. These observations suggest that the combination of gefitinib and lovastatin might have additive antiproliferative effects against gefitinib-resistant cholangiocarcinoma cells. Based on these observations, we concluded that the combination of gefitinib and lovastatin could be used to overcome gefitinib resistance in cholangiocarcinoma cells.
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Zhu X, Jiang H, Li J, Xu J, Fei Z. Anticancer Effects of Paris Saponins by Apoptosis and PI3K/AKT Pathway in Gefitinib-Resistant Non-Small Cell Lung Cancer. Med Sci Monit 2016; 22:1435-41. [PMID: 27125283 PMCID: PMC4917328 DOI: 10.12659/msm.898558] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Paris saponins have been studied for their anticancer effects in various cancer types, but the mechanisms underlying the cytotoxic effects, especially in EGFR-TKI-resistant cells, are still unclear. We explored the potential mechanism of the antitumor effects of PSI, II, VI, VII in EGFR-TKI-resistant cells and attempted to develop PSI, II, VI, VII as a systemic treatment strategy for EGFR-TKI-resistant lung cancer. Material/Methods Growth inhibition was detected by MTT assay. The apoptosis assay was detected using annexin-V/PI and Hoechst staining. The level of PI3K, pAKT, Bax, Bcl-2, caspase-3, and caspase-9 protein expression were detected using Western blot analysis. Results The results revealed that PSI, II, VI, VII inhibited the proliferation of PC-9-ZD cells. Furthermore, PSI, II, VI, VII induced significant cell apoptosis. The levels of PI3K, pAKT, Bcl-2 protein decreased, while the Bax, caspase-3, and caspase-9 protein was increased by PSI, II, PSVI, PSVII treatment and resulted in increased sensitivity to gefitinib in PC-9-ZD cells. Conclusions The underlying mechanism of Paris saponins may be related to targeting the PI3K/AKT pathways to cause apoptosis. Our results suggest a therapeutic potential of Paris saponins in clinical settings for gefitinib-resistant NSCLC.
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Affiliation(s)
- XinHai Zhu
- Department of Thoracic Surgery, Zhejiang Hospital, Hangzhou, Zhejiang, China (mainland)
| | - Hao Jiang
- Department of Oncology, Zhejiang Hospital, Hangzhou, Zhejiang, China (mainland)
| | - Jinhui Li
- Department of Chinese Medicine and Rehabilitation, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (mainland)
| | - Ji Xu
- Department of Surgery, Huashan Luxeme Medical Cosmetology Hospital, Hangzhou, Zhejiang, China (mainland)
| | - Zhenghua Fei
- Department of Oncology, The First Clinical Medical Institute, Wenzhou Medical University, Wenzhou, Zhejiang, China (mainland)
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ZHAO PENGJUN, SONG SHUICHUAN, DU LEIWEN, ZHOU GUOHUA, MA SHENGLIN, LI JINHUI, FENG JIANGUO, ZHU XINHAI, JIANG HAO. Paris Saponins enhance radiosensitivity in a gefitinib-resistant lung adenocarcinoma cell line by inducing apoptosis and G2/M cell cycle phase arrest. Mol Med Rep 2016; 13:2878-84. [DOI: 10.3892/mmr.2016.4865] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 12/21/2015] [Indexed: 11/06/2022] Open
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JIANG HAO, ZHAO PENGJUN, SU DAN, FENG JIANGUO, MA SHENGLIN. Paris saponin I induces apoptosis via increasing the Bax/Bcl-2 ratio and caspase-3 expression in gefitinib-resistant non-small cell lung cancer in vitro and in vivo. Mol Med Rep 2014; 9:2265-72. [DOI: 10.3892/mmr.2014.2108] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 03/07/2014] [Indexed: 11/06/2022] Open
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Jiang H, Zhao P, Feng J, Su D, Ma S. Effect of Paris saponin I on radiosensitivity in a gefitinib-resistant lung adenocarcinoma cell line. Oncol Lett 2014; 7:2059-2064. [PMID: 24932289 PMCID: PMC4049680 DOI: 10.3892/ol.2014.2020] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 02/26/2014] [Indexed: 01/08/2023] Open
Abstract
Previous studies have observed that Paris saponin I (PSI) exerts a wide range of pharmacological activities, including cytotoxic activity against a number of malignancies, such as non-small cell lung cancers. The present study aimed to investigate the radiosensitization of PSI treatment on a gefitinib-resistant lung adenocarcinoma cell line, PC-9-ZD, and its possible mechanism. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay was used to determine the growth inhibition effect of PSI. A clonogenic assay was performed to determine the radiosensitizing effect of PSI treatment on the PC-9-ZD cell line. A single-hit multi-target model was used to plot survival curves and calculate sensitizing enhancement ratios. The cell cycle was analyzed by flow cytometry and cell apoptosis was analyzed with fluorescein-isothiocyanate-Annexin V/propidium iodide and Hoechst staining. The expression levels of the proteins were detected by western blotting. There was a significant reduction observed in the proliferation of the PC-9-ZD cell lines that were treated with PSI. PSI enhanced the radiosensitivity of the PC-9-ZD cells with a sensitization enhancement ratio of 1.77. Furthermore, PSI induced G2/M arrest and apoptosis of the irradiated PC-9-ZD cells. Notably, B-cell lymphoma 2 (Bcl-2) was downregulated, and caspase-3, Bcl-2-like protein 4 (Bax) and cyclin-dependent kinase inhibitor 1 (P21waf1/cip1) were upregulated by the PSI treatment. The present study showed that PSI treatment exhibited potent radiosensitivity against gefitinib-resistant PC-9-ZD cells in vitro. This radiosensitivity was associated with cell cycle arrest at the G2/M phase, and apoptosis via an increase in caspase-3, Bax and P21waf1/cip1 as well as a decrease in Bcl-2 production.
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Affiliation(s)
- Hao Jiang
- Department of Oncology, Zhejiang Hospital, Hangzhou, Zhejiang 310013, P.R. China
| | - Pengjun Zhao
- Department of Radiation Oncology, Hangzhou Cancer Hospital, Hangzhou, Zhejiang 310002, P.R. China
| | - Jianguo Feng
- Department of Oncology, Zhejiang Cancer Hospital, Hangzhou, Zhejiang 310022, P.R. China
| | - Dan Su
- Department of Oncology, Zhejiang Cancer Hospital, Hangzhou, Zhejiang 310022, P.R. China
| | - Shenglin Ma
- Department of Oncology, Hangzhou First People's Hospital, Hangzhou, Zhejiang 310006, P.R. China
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Zhou Y, Li G, Ji Y, Liu C, Zhu J, Lu Y. Cytoplasmic p21 induced by p65 prevents doxorubicin-induced cell death in pancreatic carcinoma cell line. J Biomed Sci 2012; 19:15. [PMID: 22305266 PMCID: PMC3298465 DOI: 10.1186/1423-0127-19-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 02/04/2012] [Indexed: 12/29/2022] Open
Abstract
Background Studies have shown the existence of p21 induction in a p53-dependent and -independent pathway. Our previous study indicates that DOX-induced p65 is able to bind the p21 promoter to activate its transactivation in the cells. Methods Over-expression and knock-down experiments were performed in Human Pancreatic Carcinoma (PANC1) cells. Cell cycle and cell death related proteins were assessed by Western Blotting. Cytotoxicity assay was checked by CCK-8 kit. Cell growth was analyzed by flow cytometers. Results Here we showed that over-expression of p65 decreased the cytotoxic effect of DOX on PANC1 cells, correlating with increased induction of cytoplasmic p21. We observed that pro-caspase-3 physically associated with cytoplasmic p21, which may be contribution to prevent p21 translocation into the nucleus. Our data also suggested that no clear elevation of nuclear p21 by p65 provides a survival advantage by progression cell cycle after treatment of DOX. Likewise, down-regulation of p65 expression enhanced the cytotoxic effect of DOX, due to a significant decrease of mRNA levels of anti-apoptotic genes, such as the cellular inhibitor of apoptosis-1 (c-IAP1), and the long isoform of B cell leukemia/lymphoma-2 (Bcl-2), leading to efficient induction of caspase-3 cleavage in the cells. More, we present evidence that over-expression of p53 or p53/p65 in the PANC1 cells were more sensitive to DOX treatment, correlated with activation of caspase-3 and clear elevation of nuclear p21 level. Our previous data suggested that expression of p21 increases Gefitinib-induced cell death by blocking the cell cycle at the G1 and G2 phases. The present findings here reinforced this idea by showing p21's ability of potentiality of DOX-induced cell death correlated with its inhibition of cell cycle progression after over-expression of p53 or p53/p65. Conclusion Our data suggested p65 could increase p53-mediated cell death in response to DOX in PANC1 cells. Thus, it is worth noting that in p53 null or defective tumors, targeting in down-regulation of p65 may well be useful, leading to the potentiality of chemotherapeutic drugs.
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Affiliation(s)
- YingQi Zhou
- Tongji University School of Medicine, Shanghai, China
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Li G, Ji Y, Liu C, Li J, Zhou Y. Reduced levels of p15INK4b, p16INK4a, p21cip1 and p27kip1 in pancreatic carcinoma. Mol Med Rep 2012; 5:1106-10. [PMID: 22293850 PMCID: PMC3493078 DOI: 10.3892/mmr.2012.771] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 01/10/2012] [Indexed: 12/15/2022] Open
Abstract
Pancreatic carcinoma is one of the leading causes of cancer mortality worldwide, although the molecular mechanisms of this disease are poorly understood. The aim of this study was to examine the expression of cyclin-dependent kinase inhibitors (CDKIs) and the epigenetic modifications in the promoters of these genes. We also evaluated the correlation between the methylation status of CDKI genes and smoking habit in clinical pancreatic carcinoma specimens. Western blotting and real-time PCR were performed to assess CDKI expression. Methylation-specific PCR was carried out to examine the methylation status of the promoters of CDKI genes. In this study, we revealed that reduced levels of the CDKI proteins, p15INK4b, p16INK4a, p21cip1 and p27kip1, are a prominent feature of pancreatic carcinoma patients. The DNA hypermethylation of the promoter was observed in 40% (2 of 5) of the p15INK4b genes, 60% (3 of 5) of the p16INK4a genes and 60% of the p21cip1 genes, which markedly correlated with their decreased mRNA expression. No hypermethylation was detected in the p27kip1 gene promoter in 5 pancreatic carcinoma patients with markedly decreased expression of p27kip1 mRNA, suggesting an alternative mechanism of p27kip in these patients. In this study, patients with a smoking habit displayed methylation of 2 CDKI genes in their pancreatic carcinoma specimens. We concluded that epigenetic modification via hypermethylation represents a critical mechanism for the inactivation of CDKI genes in pancreatic carcinoma.
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Affiliation(s)
- Gang Li
- The Third General Surgery Department, Zhanghai Hospital, Second Military Medical University, Shanghai, PR China
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P21 (waf1/cip1) is required for non-small cell lung cancer sensitive to Gefitinib treatment. Biomed Pharmacother 2011; 65:151-6. [PMID: 21616632 DOI: 10.1016/j.biopha.2011.02.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 02/08/2011] [Indexed: 01/26/2023] Open
Abstract
Lung cancer is the leading cause of death from cancer in the world. Gefitinib is known to its inhibition of EGFR tyrosine kinase and worldwide used for antitumor in non-small cell lung cancer (NSCLC). Here, we show that Gefitinib reduces p-Akt levels, concomitant with elevation of p21 levels and suppression of cdk2/4 and cyclinE/D1 activities which result in impaired cell cycle progression through G1 arrest only in NSCLC cells in which it inhibits growth. We find that Gefitinib-induced p21 protein stability, rather than increased RNA accumulation, was responsible for the elevated p21 levels. More, treatment of beta-elemene, a natural plant drug extracted from Curcuma wenyujin, restored sensitivity to Gefitinib via the mechanism modulated the elevation of p21 levels in the cells which are acquired resistance to Gefitinib. These data suggest that administration of Gefitinib in combination with beta-elemene may offer great opportunities for NSCLC which are acquired resistance to Gefitinib. The p21 effect on the cells to response to Gefitinib was further confirmed by p21 over-expression and knockdown studies pointing to a requirement of p21 for the cells sensitive to Gefitinib. Thus, we propose that p21 is required for Gefitinib-sensitive NSCLC cells.
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