The activation of protease-activated receptor 1 mediates proliferation and invasion of nasopharyngeal carcinoma cells

Protease-activated receptor 1 (PAR-1) is a G-coupled membrane protein, which is involved in physiological and malignant invasion processes. It is activated by serine proteases such as thrombin through a unique form or by specific synthetic peptides. In this study, we determined the expression of PAR-1 in five nasopharyngeal carcinoma (NPC) cell lines with different characteristics of invasiveness and metastasis, and found that the levels of PAR-1 expression were higher in invasive or metastatic cell lines than those in low invasive or metastatic ones. Of the five NPC cell lines, CNE1-LMP1 cells had the highest expression levels of PAR-1, which was mainly distributed at the membrane and in the cytoplasm of tumor cells. Further study showed that the thrombin receptor synthetic activating peptide SFLLRN could stimulate the growth of CNE1-LMP1 cells in a dose-dependent manner. However, thrombin itself had a dual effect on the proliferation of NPC cells. Concentrations of thrombin in the range of 0.1-0.5 U/ml promoted cell growth, but concentrations higher than 0.5 U/ml impaired cell growth. Moreover, thrombin and SFLLRN also enhanced the invasive capabilities of CNE1-LMP1 cells in vitro, and this was partly due to enhancing the activities of MMP-2 and MMP-9. Our findings suggest that PAR-1 may contribute to the growth and invasive potential of NPC cells.     

三氧化二砷抑制人鼻咽癌细胞侵袭的体外实验研究

 目的 观察三氧化二砷(As₂O₃)对人鼻咽癌细胞株HNEl-LMPl侵袭、转移的影响。方法 鼻咽癌细胞在含3μmol／L的As₂O₃培养基中培养48小时。然后在无含砷的培养基中继续培养48小时后，收集此时间点贴壁的细胞作为研究对象；用细胞-基质黏附实验、细胞运动实验和肿瘤细胞重组基底膜侵袭实验检测As₂O₃对HNEl-LMPl细胞黏附、运动及侵袭能力的影响；用激光共聚焦的方法检测EB病毒编码的潜伏膜蛋白1(LMPl)的表达情况。结果 肿瘤细胞-基质黏附实验结果显示，经As₂O₃处理的HNEl-LMPl细胞，其黏附能力(平均吸光度为0．524±0．09)低于对照组细胞(平均吸光度为0．665±0．14)，两者相比有差异(P<0．05)。运动实验和肿瘤细胞重组基底膜侵袭结果均显示，经As₂O₃处理后，穿过游离的聚乙烯吡咯烷酮膜(PVP-F)的肿瘤细胞数明显减少(P<0.01)，同时As₂O₃能够下调LMPl的表达。结论As₂O₃具有抗人鼻咽癌细胞株转移的潜力，其机制可能与抑制LMPl的表达相关。     

Knockdown of cyclophilin A reverses paclitaxel resistance in human endometrial cancer cells via suppression of MAPK kinase pathways

Purpose

Paclitaxel resistance remains to be a major obstacle to the chemotherapy of endometrial cancer. Using proteomic-based approach, we used to identify cyclophilin A (CypA) as a potential therapeutic target for endometrial cancer. As a natural continuation, this study aimed to reveal the correlation between CypA and paclitaxel resistance and evaluate the possibility of CypA as a therapeutic target for reversal of resistance.

Methods

Two paclitaxel-resistant endometrial cancer cell sublines HEC-1-B/TAX and AN3CA/TAX were generated, and expressions of CypA, P-gp, MRP-2 and survivin were demonstrated by Western blotting. CypA was knocked down by RNA interference, and the subsequent effects on the alteration of paclitaxel resistance were examined by MTT, flow cytometry and migratory/invasive transwell assays. MAPK kinases activities were examined by Western blotting.

Results

CypA knockdown led to significant inhibition of cell proliferation, induction of apoptosis and suppression of migratory/invasive capacity in HEC-1-B/TAX and AN3CA/TAX cells when exposed to paclitaxel. CypA knockdown led to reductions in total and phosphorylated MAPK kinases, including Akt, ERK1/2, p38 MAPK and JNK, in HEC-1-B/TAX cells. Furthermore, pretreatment with MAPK kinase inhibitors exhibited a synergistic effect in combination with CypA knockdown.

Conclusions

These results demonstrated that CypA expression was up-regulated in paclitaxel-resistant cancer cells, and knockdown of CypA could reverse the paclitaxel resistance through, at least partly, suppression of MAPK kinase pathways, presenting a possibility of CypA serving as a therapeutic target to overcome paclitaxel resistance.     

Stathmin 1 inhibition amplifies ruxolitinib-induced apoptosis in JAK2V617F cells

The JAK/STAT pathway is constitutively activated in myeloproliferative neoplasms and can be inhibited by ruxolitinib, a selective JAK1/2 inhibitor. The JAK2^V617F mutation leads to constitutive STAT3 phosphorylation and potentially leads to inhibition of Stathmin 1 activity via STAT3. In support of this hypothesis, we found that, in HEL JAK2^V617F cells, ruxolitinib treatment decreased STAT3 and Stathmin 1 association, induced Stathmin 1 activation and microtubule instability. Silencing of Stathmin 1 significantly reduced cell proliferation and clonal growth, and increased apoptosis induced by ruxolitinib. Stathmin 1 silencing also prevented ruxolitinib-induced microtubule instability. To phenocopy the effect of Stathmin 1 inhibition, cells were treated with paclitaxel, a microtubule-stabilizing drug, in association or not with ruxolitinib; combined treatment significantly increased apoptosis, when compared to monotherapy. Notably, Stathmin 1 mRNA levels were highly expressed in CD34⁺ cells from primary myelofibrosis patients. We then proposed that an undesired effect of ruxolitinib treatment may constitute Stathmin 1 activation and microtubule instability in JAK2^V617F cells. Induction of microtubule stability, through Stathmin 1 silencing or paclitaxel treatment, combined with ruxolitinib could be an effective strategy for promoting apoptosis in JAK2^V617F cells.     

siRNA-mediated knock-down of DFF45 amplifies doxorubicin therapeutic effects in breast cancer cells

Purpose

RNA interference (RNAi) has become a promising tool for cancer therapy. Small interfering RNAs (siRNAs) can synergistically enhance the cell killing effects of drugs used in cancer treatment. Here we examined the effects of siRNA-mediated DNA fragmentation factor 45 (DFF45) gene silencing on breast cancer cell viability, cell cycle arrest, and apoptosis in the presence and absence of doxorubicin.

Methods

We designed three siRNAs, which target different regions of the DFF45 mRNA. Gene silencing was confirmed by real time RT-PCR and Western blot analyses. The impact of DFF45 siRNA, doxorubicin, and their combination on the viability, cell cycle and apoptosis of T-47D and MDA-MB-231 breast cancer cells were determined by MTT, PI staining, annexin V binding, caspase-3 activity, DNA laddering, and chromatin condensation assays.

Results

Based on flow cytometric analyses, we found that silencing of DFF45 alone had little effect on apoptosis, especially in T-47D cells. However, when used in combination with doxorubicin (0.33 μM) a significant increase (P?<?0.05) in apoptosis was observed in T-47D and MDA-MB-231 cells, i.e., ~2.5- and 3-fold, respectively. Caspase-3 activity, chromatin condensation, as well as DNA laddering supported increased apoptosis in the combinatorial treatment. Cell cycle arrest in both cell lines occurred at lower levels after siRNA + doxorubicin treatment compared to doxorubicin only.

Conclusions

Our data indicate that DFF45 gene silencing, when applied in combination with doxorubicin, may offer a novel therapeutic strategy for the treatment of breast cancer.     

siRNA干扰KLF8表达对鼻咽癌细胞上皮间质转化的作用

目的 探讨下调KLF8的表达对鼻咽癌CNE1-LMP1细胞侵袭能力的影响及其机制。方法 通过脂质体转染法将KLF8 siRNA真核表达质粒稳定转染至鼻咽癌细胞株CNE1-LMP1。Western blot和RT-PCR法检测CNE1-LMP1细胞中KLF8、E-cadherin、N-cadherin蛋白和mRNA表达水平的变化。Transwell侵袭实验观察siRNA后对CNE1-LMP1细胞侵袭能力的影响。结果 KLF8 siRNA转染的CNE1-LMP1细胞株与其阴性对照NC-si组比较KLF8蛋白和mRNA表达水平均下调,证实稳转细胞株建立成功。KLF8 siRNA可上调CNE1-LMP1细胞中E-cadherin的表达,而下调N-cadherin的表达。Transwell侵袭实验显示siRNA干扰CNE1-LMP1细胞侵袭能力下降。结论 KLF8在鼻咽癌CNE1-LMP1细胞中高表达;通过siRNA下调KLF8的表达能干扰上皮间质转化（EMT）相关蛋白E-cadherin、N-cadherin的表达,阻断EMT过程,抑制CNE1-LMP1细胞侵袭转移。     

Phenotypic alterations induced by the Hong Kong-prevalent Epstein-Barr virus-encoded LMP1 variant (2117-LMP1) in nasopharyngeal epithelial cells

Epstein-Barr virus (EBV) is closely associated with nasopharyngeal carcinoma (NPC), a common cancer in Hong Kong. The EBV-encoded LMP1 protein is believed to play an important role in cell transformation. We have previously identified a prevalent LMP1 variant (2117-LMP1) that is expressed in 86% of primary NPC in Hong Kong. In this study, the biologic phenotypes induced by 2117-LMP1 were compared with those of the prototypic B95.8-LMP1 in an immortalized nasopharyngeal epithelial cell line, NP69. The 2117-LMP1 could induce cell proliferation and resistance to apoptosis induced by growth factor deprivation. Expression of 2117-LMP1 also suppressed expression of p16, p21 and Bax but induced expression of CDK2 and A20. Compared with B95.8-LMP1, 2117-LMP1 could induce a higher migration ability in NP69 cells but was less efficient in inducing morphologic changes, anchorage-independent growth and cell invasion. Relatively weaker ability of 2117-LMP1 than B95.8-LMP1 in upregulation of vimentin, VEGF and MMP9 as well as in downregulation of E-cadherin was observed. 2117-LMP1 could activate higher level of NF-kappaB activity in HEK 293 cells than B95.8-LMP1. The present study supports a role of 2117-LMP1 in NPC development by enhancing cell proliferation, cell death inhibition and migration in premalignant nasopharyngeal epithelial cells. Furthermore, our study reveals significant functional differences between 2117-LMP1 and the prototypic B95.8-LMP1. Our results provide insights into the pathologic significance of this prevalent LMP1 variant, 2117-LMP1, in the development of NPC in the Hong Kong population.     

明胶酶在不同类型鼻咽癌细胞株中的表达及其活性差异

目的:探讨明胶酶的表达与鼻咽癌细胞转移潜能的关系。方法:Real-time PCR和明胶酶谱法检测CNE1、CNE1-LMP1、CNE2、SUNE1-5-8F和SUNE1-6-10B 5株鼻咽癌细胞株中明胶酶mRNA的表达及分泌,并比较其差异。结果:明胶酶mRNA在5株鼻咽癌细胞中都有表达,其相对表达量为SUNE1-5-8F>CNE1-LMP1>SUNE1-6-10B>CNE2>CNE1,其中,明胶酶mRNA在SUNE1-5-8F细胞和SUNE1-6-10B之间以及CNE1-LMP1细胞和CNE1细胞之间的表达差异有统计学意义,P<0.001;在CNE2细胞和CNE1细胞之间,MMP-9 mRNA的表达差异有统计学意义(P<0.001),而MMP-2 mR-NA的表达差异无统计学意义,P=0.078;明胶酶谱结果显示,明胶酶的活性在CNE1-LMP1细胞上清液中明显高于CNE1细胞(P≤0.001),在SUNE1-5-8F细胞上清液中明显高于SUNE1-6-10B细胞(P<0.001),而CEN2细胞分泌明胶酶的量为5株细胞中最低1株。结论:明胶酶的表达和分泌与鼻咽癌细胞的转移潜能密切相关。     

Restoration of klotho expression induces apoptosis and autophagy in hepatocellular carcinoma cells

Purpose

Klotho has been identified as a tumor suppressor in several human malignancies including hepatocellular carcinoma (HCC). However, the signaling pathways involved in the tumor suppressive role of klotho in HCC have not been reported. Here, we investigated the role of klotho in HCC cell proliferation, apoptosis, autophagy, and invasion, as well as its associated signal transduction pathways.

Methods

Restoration of klotho gene expression was established by delivering a klotho gene expression vector into the human HCC cell lines HepG2 and MHCC-97-H. Cell viability was measured using a cell counting (CCK-8) assay and apoptosis was analyzed through flow cytometry. Autophagy was measured via LC3-I and LC3-II protein expression levels and tumor cell invasion was assessed using a Matrigel invasion chamber assay. Expression and phosphorylation of several apoptosis and survival related proteins were assessed using Western blot assays.

Results

Exogenous klotho gene expression significantly inhibited HCC cell proliferation, induced HCC cell apoptosis, increased LC3-I and LC3-II protein expression in HCC cells, and decreased migration of HCC cells in a Matrigel invasion chamber assay. Exogenous klotho gene expression also down-regulated the phosphorylation levels of the IGF-1 receptor, and the downstream Akt, ERK, and p70S6K proteins. Both apoptosis and autophagy inhibitors decreased klotho-induced apoptosis and autophagy.

Conclusion

Klotho is a tumor suppressor that, through the regulation of IGF-1R phosphorylation and subsequent activation of downstream Akt-p70S6K and ERK signaling, regulates HCC tumor cell proliferation, apoptosis, autophagy and invasion.     

下调miR-21表达抑制鼻咽癌CNE2细胞增殖和侵袭

背景与目的：miR-21在人类多种肿瘤中异常高表达。本研究探讨干扰miR-21表达对鼻咽癌CNE2细胞增殖、迁移和侵袭的影响。方法：使用脂质体将miR-21 inhibitor转染CNE2细胞,以无关序列(NC inhibitor)作为阴性对照。采用qRT-PCR技术验证miR-21 inhibitor转染的CNE2细胞中miR-21的表达水平;通过MTS法、细胞划痕、Transwell侵袭实验观察下调miR-21表达对CNE2细胞增殖、迁移和侵袭的影响。结果：转染miR-21 inhibitor的CNE2细胞中miR-21的表达明显下调,并且呈浓度依赖性。表明转染miR-21 inhibitor能有效抑制CNE2细胞中miR-21的表达。转染miR-21 inhibitor的CNE2细胞与对照细胞相比,增殖速度明显减慢,差异有统计学意义(P<0.05)。细胞划痕实验显示,下调miR-21表达抑制CNE2细胞迁移(P<0.05)。Transwell侵袭实验结果显示,下调miR-21表达抑制CNE2细胞侵袭(P<0.05)。结论：miR-21能促进鼻咽癌细胞增殖、迁移和侵袭,其可能在鼻咽癌的发生、发展中发挥重要作用。     

Over-expression of BMPR-IB reduces the malignancy of glioblastoma cells by upregulation of p21 and p27Kip1

Background

Human interacting protein X1 (PinX1) has been identified as a critical telomerase inhibitor and proposed to be a putative tumor suppressor gene. Loss of PinX1 has been found in a large variety of malignancies, however, its function in inhibiting telomerase activity of tumor cells is not well documented. Here we show that PinX1 is essential for down-regulation telomerase activity of nasopharyngeal carcinoma.

Methods

Expression vectors of human PinX1 (pEGFP-C3-PinX1) and its small interfering RNA (PinX1-FAM-siRNA) were constructed and transfected into NPC. Their effects on mRNA of telomerase catalytic subunit (hTERT), telomerase activity, cell proliferation, cell migration, wound healing, cell cycles and apoptosis were examined using semi-quantitative RT-PCR, stretch PCR, MTT assay, Transwell, scratch assay and flow cytometry, respectively.

Results

Transfection of pEGFP-C3-PinX1 and PinX1-FAM-siRNA increased and reduced PinX1 mRNA by 1.6-fold and 70%, respectively. Over-expression of PinX1 decreased hTERT mRNA by 21%, reduced telomerase activity, inhibited cell growth, migration and wound healing ability, arrested cells in G0/G1 phase, and increased apoptotic index. In contrast, down-regulation of PinX1 did not alter the above characteristics.

Conclusions

PinX1 may play important roles in NPC proliferation, migration and apoptosis and has application potential in tumor-targeted gene therapy.     

DNAzymes targeted to EBV-encoded latent membrane protein-1 induce apoptosis and enhance radiosensitivity in nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is involved in the carcinogenesis of several types of cancers such as nasopharyngeal carcinoma (NPC) and Burkitt's lymphoma. The latent membrane protein (LMP1) encoded by EBV is expressed in the majority of EBV-associated human malignancies and has been suggested to be one of the major oncogenic factors in EBV-mediated carcinogenesis. Therefore, genetic manipulation of LMP1 expression may provide a novel strategy for the treatment of the EBV-associated human cancers. Deoxyribozymes (DNAzymes) are catalytic nucleic acids that bind and cleave a target RNA in a highly sequence-specific manner. We have designed several LMP1-specific DNAzymes and tested their effect on cell proliferation and apoptosis in LMP1-positive cells. Here, we show that active DNAzymes down-regulated the expression of the EBV oncoprotein LMP1 and inhibited cellular signal transduction pathways abnormally activated by LMP1. This down-regulation of the LMP1 expression was shown to be associated with a decrease in the level of antiapoptotic Bcl-2 and an increase in Caspase-3 and -9 activities in the nasopharyngeal carcinoma cell line CNE1-LMP1, which constitutively expresses the LMP1. When combined with radiation treatment, the DNAzymes significantly induced apoptosis in CNE1-LMP1 cells, leading to an increased radiosensitivity both in cells and in a xenograft NPC model in mice. The results suggest that LMP1 may represent a molecular target for DNAzymes and provide a basis for the use of the LMP1 DNAzymes as potential radiosensitizers for treatment of the EBV-associated carcinomas.     

Mechanistic population pharmacokinetics of total and unbound paclitaxel for a new nanodroplet formulation versus Taxol in cancer patients

Purpose

Our objectives were (1) to compare the disposition and in vivo release of paclitaxel between a tocopherol-based Cremophor-free formulation (Tocosol Paclitaxel^®) and Cremophor^® EL-formulated paclitaxel (Taxol^®) in human subjects, and (2) to develop a mechanistic model for unbound and total paclitaxel pharmacokinetics.

Methods

A total of 35 patients (average ± SD age: 59 ±13 years) with advanced non-hematological malignancies were studied in a randomized two-way crossover trial. Patients received 175 mg/m² paclitaxel as 15 min (Tocosol Paclitaxel) or 3 h (Taxol) intravenous infusion in each study period. Paclitaxel concentrations were determined by LC–MS/MS in plasma ultrafiltrate and whole blood. NONMEM VI was used for population pharmacokinetics.

Results

A linear disposition model with three compartments for unbound paclitaxel and a one-compartment model for Cremophor were applied. Total clearance of unbound paclitaxel was 845 L/h (variability: 25% CV). The prolonged release with Tocosol Paclitaxel was explained by the limited solubility of unbound paclitaxel of 405 ng/mL (estimated) in plasma. The 15 min Tocosol Paclitaxel infusion yielded a mean time to 90% cumulative input of 1.14 ± 0.16 h. Tocosol Paclitaxel was estimated to release 9.8% of the dose directly into the deep peripheral compartment. The model accounted for the presence of drug-containing nanodroplets in blood.

Conclusions

Population pharmacokinetic analysis indicated linear disposition and a potentially higher bioavailability of unbound paclitaxel following Tocosol Paclitaxel administration due to direct release at the target site. The prolonged release of Tocosol Paclitaxel supports 15 min paclitaxel infusions. This mechanistic model may be important for development of prolonged release formulations that distribute in and from the systemic circulation.     

Role of JNK signaling pathway in sensitivity to radiotherapy of nasopharyngeal carcinoma

Objective

The aim of the study was to investigate the effect of c-Jun N-terminal protein kinase (JNK) signaling pathway on influencing the sensitivity to radiotherapy of human nasopharyngeal carcinoma CNE cells.

Methods

Human nasopharyngeal carcinoma CNE multicellular spheroids (MCS) were constructed with three dimensional cell culture methods. Western blot was employed to analyze the activity of JNK signaling pathway in MCS after X-ray irradiation, and the expression of caspase-3 protein before and after using SP600125 (a special inhibitor of JNK). X-ray induced cell apoptosis in MCS before and after treated with SP600125 were detected by TUNEL.

Results

The level of JNK phosphorylation in MCS was a dynamic course after radiation, and there was a phosphorylation peaks at 2 h later, the apoptotic rate of MCS (P < 0.05) and the expression of caspase-3 protein (P < 0.05) were significantly increased after treated with SP600125.

Conclusion

The transient activation of JNK played a important role in sensitivity to radiotherapy of CNE MCS via mediating survival signals, blocking this pathway accelerate cell apoptosis, which may be related to the increased expression of caspase-3.     

Prediction of paclitaxel sensitivity by CDK1 and CDK2 activity in human breast cancer cells

Introduction

Paclitaxel is used widely in the treatment of breast cancer. Not all tumors respond to this drug, however, and the characteristics that distinguish resistant tumors from sensitive tumors are not well defined. Activation of the spindle assembly checkpoint is required for paclitaxel-induced cell death. We hypothesized that cyclin-dependent kinase (CDK) 1 activity and CDK2 activity in cancer cells, which reflect the activation state of the spindle assembly checkpoint and the growth state, respectively, predict sensitivity to paclitaxel.

Methods

Cell viability assays and DNA and chromatin morphology analyses were performed in human breast cancer cell lines to evaluate sensitivity to paclitaxel and the cell cycle response to paclitaxel. We then examined the specific activities of CDK1 and CDK2 in these cell lines and in xenograft models of human breast cancer before and after paclitaxel treatment. Protein expression and kinase activity of CDKs and cyclins were analyzed using a newly developed assay system.

Results

In the cell lines, biological response to paclitaxel in vitro did not accurately predict sensitivity to paclitaxel in vivo. Among the breast cancer xenograft tumors, however, tumors with significantly increased CDK1 specific activity after paclitaxel treatment were sensitive to paclitaxel in vivo, whereas tumors without such an increase were resistant to paclitaxel in vivo. Baseline CDK2 specific activity was higher in tumors that were sensitive to paclitaxel than in tumors that were resistant to paclitaxel.

Conclusions

The change in CDK1 specific activity of xenograft tumors after paclitaxel treatment and the CDK2 specific activity before paclitaxel treatment are both associated with the drug sensitivity in vivo. Analysis of cyclin-dependent kinase activity in the clinical setting could be a powerful approach for predicting paclitaxel sensitivity.     

The cytosol activity of thymidine phosphorylase in endometrial cancer

Background

The cellular apoptosis susceptibility (CAS) protein is regarded as a proliferation-associated protein that associates with tumour proliferation as it associates with microtubule and functions in the mitotic spindle checkpoint. However, there is no any actual experimental study showing CAS (or CSE1 and CSE1L) can increase the proliferation of cancer cells. Previous pathological study has reported that CAS was strongly positive stained in all of the metastasis melanoma that be examined. Thus, CAS may regulate the invasion and metastasis of cancers. CAS is highly expressed in cancers; if CAS is associated with cancer proliferation, then increased CAS expression should be able to increase the proliferation of cancer cells. We studied whether increased CAS expression can increase cancer cell proliferation and whether CAS regulates the invasion of cancer cells.

Methods

We enhanced or reduced CAS expression by transfecting CAS or anti-CAS expression vectors into human MCF-7 breast cancer cells. The proliferations of cells were determined by trypan blue exclusion assay and flow cytometry analysis. Invasion of cancer cells were determined by matrigel-based invasion assay.

Results

Our studies showed that increased CAS expression was unable to enhance cancer cell proliferation. Immunofluorescence showed CAS was distributed in cytoplasm areas near cell membrane and cell protrusions. CAS was localized in cytoplasmic vesicle and immunogold electronmicroscopy showed CAS was located in vesicle membrane. CAS overexpression enhanced matrix metalloproteinase-2 (MMP-2) secretion and cancer cell invasion. Animal experiments showed CAS reduction inhibited the metastasis of B16-F10 melanoma cells by 56% in C57BL/6 mice.

Conclusion

Our results indicate that CAS increases the invasion but not the proliferation of cancer cells. Thus, CAS plus ECM-degradation proteinases may be used as the markers for predicting the advance of tumour metastasis.     

Inhibition of CDK4 sensitizes multidrug resistant ovarian cancer cells to paclitaxel by increasing apoptosiss

Purpose

Overexpression of cyclin-dependent kinase (CDK) 4 has been observed in a variety of cancers and has been found to contribute to tumor cell growth and proliferation. However, the effect of inhibition of CDK4 in ovarian cancer is unknown. We investigated the therapeutic effect of the CDK4 inhibitor palbociclib in combination with paclitaxel in ovarian cancer cells.

Methods

Cell viabilities were determined by MTT assay after exposure to different dosages of palbociclib and/or paclitaxel. Western blot, immunofluorescence, and Calcein AM assays were conducted to determine the mechanisms underlying the cytotoxic effects of palbociclib in combination with paclitaxel. CDK4 siRNA was used to validate the outcome of targeting CDK4 by palbociclib in ovarian cancer cells.

Results

We found that combinations of palbociclib and paclitaxel significantly enhanced drug sensitivity in both Rb-positive (SKOV3TR) and Rb-negative (OVCAR8TR) ovarian cancer-derived cells. When combined with paclitaxel, palbociclib induced apoptosis in both SKOV3TR and OVCAR8TR cells. We also found that palbociclib inhibited the activity of P-glycoprotein (Pgp), and that siRNA-mediated CDK4 knockdown sensitized multidrug resistant (MDR) SKOV3TR and OVCAR8TR cells to paclitaxel.

Conclusions

Inhibition of CDK4 by palbociclib can enhance paclitaxel sensitivity in both Rb-positive and Rb-negative MDR ovarian cancer cells by increasing apoptosis. CDK4 may serve as a promising target in the treatment of ovarian cancer.

     

Suppression of autophagy enhances preferential toxicity of paclitaxel to folliculin-deficient renal cancer cells

Background

Paclitaxel, a widely used chemotherapeutic drug, can induce apoptosis in variety of cancer cells. A previous study has shown preferential toxicity of paclitaxel to FLCN-deficient kidney cancer cell line, UOK257. In this report, we investigate the cellular and molecular mechanism of paclitaxel-induced autophagy and apoptosis in renal cancer cells with and without FLCN expression.

Methods

Two pairs of cell lines were used: FLCN siRNA-silenced ACHN cell line (ACHN-5968) and scrambled ACHN cell line (ACHN-sc); FLCN-null UOK257 cell line and UOK257-2 cell line restored with ectopic expression of FLCN. Autophagy was examined by western blot, GFP-LC3, transmission electron microscopy, and MDC assay. Cell viability and apoptosis were detected using MTT assay, DAPI stain and TUNEL assay. After inhibition of autophagy with 3-Methyladenine (3-MA) or Beclin 1 siRNA, cell viability and apoptosis were measured by MTT assay and TUNEL assay.

Results

After paclitaxel treatment, a dose-dependent decrease in cell viability and increase in apoptosis were observed in FLCN-deficient UOK257 and ACHN-5968 cells compared to their FLCN-expressing counterparts, suggesting that renal cancer cells without FLCN were more sensitive to paclitaxel. Enhanced autophagy was found to be associated with paclitaxel treatment in FLCN-deficient RCC cells. The MAPK pathway was also identified as a key pathway for the activation of autophagy in these kidney cancer cells. Inhibition of phosphorylated ERK with ERK inhibitor U0126 showed a significant decrease in autophagy. Furthermore, after inhibition of autophagy with 3-Methyladenine (3-MA) or Beclin 1 siRNA, apoptosis induced by paclitaxel was significantly increased in FLCN-deficient UOK257 and ACHN-5968 cells.

Conclusions

Preferential toxicity of paclitaxel to FLCN-deficient kidney cancer cells is associated with enhanced autophagy. Suppression of autophagy further enhances paclitaxel-induced apoptosis in FLCN-deficient renal cancer cells. Our results suggest that paclitaxel combined with an autophagy inhibitor might be a potentially more effective chemotherapeutic approach for FLCN-deficient renal cancer.