Growth Inhibitory Effects Of Paclitaxel Research Articles

Sensitization of cancer cells to paclitaxel-induced apoptosis by canagliflozin

Cancer cells consume more glucose and usually overexpress glucose transporters which have become potential targets for the development of anticancer drugs. It has been demonstrated that selective SGLT2 inhibitors, such as canagliflozin and dapagliflozin, display anticancer activity. Here we demonstrated that canagliflozin and dapagliflozin synergistically enhanced the growth inhibitory effect of paclitaxel in cancer cells including ovarian cancer and oral squamous cell carcinoma cells. Canagliflozin also inhibited glucose uptake via GLUTs. The combination of paclitaxel and WZB117, a GLUT inhibitor, exhibited a strong synergy, supporting the notion that inhibition of GLUTs by canagliflozin may also account for the synergy between canagliflozin and paclitaxel. Mechanistic studies in ES-2 ovarian cancer cells revealed that canagliflozin potentiated paclitaxel-induced apoptosis and DNA damaging effect. Paclitaxel in the nanomolar range elevated abnormal mitotic cells as well as aneuploid cells, and canagliflozin further enhanced this effect. Furthermore, canagliflozin downregulated cyclin B1 and phospho-BUBR1 upon spindle assembly checkpoint (SAC) activation by paclitaxel, and may consequently impair SAC. Thus, paclitaxel disturbed microtubule dynamics and canagliflozin compromised SAC activity, together they may induce premature mitotic exit, accumulation of aneuploid cells with DNA damage, and ultimately apoptosis.

A CAF-Based Two-Cell Hybrid Co-Culture Model to Test Drug Resistance in Endometrial Cancers.

The management of advanced or recurrent endometrial cancers presents a challenge due to the development of resistance to treatments. The knowledge regarding the role of the tumor microenvironment (TME) in determining the disease's progression and treatment outcome has evolved in recent years. As a TME component, cancer-associated fibroblasts (CAFs) are essential in developing drug-induced resistance in various solid tumors, including endometrial cancers. Hence, an unmet need exists to test the role of endometrial CAF in overcoming the roadblock of resistance in endometrial cancers. We present a novel tumor-TME two-cell ex vivo model to test CAF's role in resisting the anti-tumor drug, paclitaxel. Endometrial CAFs, both NCAFs (tumor-adjacent normal-tissue-derived CAFs) and TCAFs (tumor-tissue-derived CAFs) were validated by their expression markers. Both TCAFs and NCAFs expressed positive markers of CAF, including SMA, FAP, and S100A4, in varying degrees depending on the patients, while they consistently lacked the negative marker of CAF, EpCAM, as tested via flow cytometry and ICC. CAFs expressed TE-7 and immune marker, PD-L1, via ICC. CAFs better resisted the growth inhibitory effect of paclitaxel on endometrial tumor cells in 2D and 3D formats compared to the resistance of the tumoricidal effect of paclitaxel in the absence of CAFs. TCAF resisted the growth inhibitory effect of paclitaxel on endometrial AN3CA and RL-95-2 cells in an HyCC 3D format. Since NCAF similarly resisted the growth inhibitor action of paclitaxel, we tested NCAF and TCAF from the same patient to demonstrate the protective action of NCAF and TCAF in resisting the tumoricidal effect of paclitaxel in AN3CA in both 2D and 3D matrigel formats. Using this hybrid co-culture CAF and tumor cells, we established a patient-specific, laboratory-friendly, cost-effective, and time-sensitive model system to test drug resistance. The model will help test the role of CAFs in developing drug resistance and contribute to understanding tumor cell-CAF dialogue in gynecological cancers and beyond.

Abstract LB073: The growth inhibitory effect of paclitaxel on gefitinib-resistant non-small cell lung cancer (NSCLC) cells during the COVID-19 pandemic

Abstract Background: Coronavirus disease 2019 (COVID-19) has posed a great challenge for the treatment of cancer patients. COVID-19 presents as a severe respiratory infection in aging individuals, including lung cancer patients. COVID-19 may be linked to the progression of aggressive lung cancer. Conversely, the side effects of chemotherapy, such as chemotherapy resistance and the acceleration of cellular senescence could worsen COVID-19. Considering the above-mentioned facts, our present work aimed to investigate the role of paclitaxel (a chemotherapy drug) in the cell proliferation, apoptosis, and cellular senescence of gefitinib-resistant NSCLC cells (PC9-MET) and to reveal the underlying mechanisms. Methods: PC9-MET cells were treated with paclitaxel for 72 h and were then evaluated by a cell viability assay, DAPI staining, Giemsa staining, apoptosis assay, ROS assay, SA-β-Gal staining, TUNEL assay and Western blotting.Results: Our results revealed that paclitaxel significantly reduced the viability of PC9-MET cells and induced morphological signs of apoptosis. The apoptotic effects of paclitaxel were observed by increased levels of cleaved caspase-3, cleaved caspase-9 and cleaved PARP. Additionally, paclitaxel increased ROS production, leading to DNA damage. Importantly, paclitaxel eliminated cellular senescence, which was observed by SA-β-Gal staining.Conclusion: In light of these findings, paclitaxel could be a promising anticancer drug and could offer a new therapeutic strategy for gefitinib-resistant NSCLC during the COVID-19 pandemic. Citation Format: Md Mohiuddin, Hideharu Kimura, Takashi Sone, Satoshi Watanabe, Hiroki Matsuoka, Keigo Saeki, Nanao Terada, Miki Abo, Kazuo Kasahara. The growth inhibitory effect of paclitaxel on gefitinib-resistant non-small cell lung cancer (NSCLC) cells during the COVID-19 pandemic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB073.

The mechanism of the growth inhibitory effect of paclitaxel on gefitinib-resistant non-small cell lung cancer (NSCLC) cells during the COVID-19 pandemic.

e15007 Background: Coronavirus disease 2019 (COVID-19) poses a great challenge for the treatment of cancer patients. It presents as a severe respiratory infection in aging individuals, including lung cancer patients. COVID-19 may be linked to the progression of aggressive lung cancer. In addition, the side effects of chemotherapy, such as chemotherapy resistance and the acceleration of cellular senescence, can worsen COVID-19. Given this situation, we investigated the role of paclitaxel (a chemotherapy drug) in the cell proliferation, apoptosis, and cellular senescence of gefitinib-resistant non-small-cell lung cancer (NSCLC) cells (PC9-MET) to clarify the underlying mechanisms. Methods: PC9-MET cells were treated with paclitaxel for 72 h and then evaluated by a cell viability assay, DAPI staining, Giemsa staining, apoptosis assay, a reactive oxygen species (ROS) assay, SA-β-Gal staining, a terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and Western blotting. Results: Our results revealed that paclitaxel significantly reduced the viability of PC9-MET cells and induced morphological signs of apoptosis. The apoptotic effects of paclitaxel were observed by increased levels of cleaved caspase-3 (Asp 175), cleaved caspase-9 (Asp 330) and cleaved PARP (Asp 214). In addition, paclitaxel increased ROS production, leading to DNA damage. Inhibition of ROS production by N-acetylcysteine attenuates paclitaxel-induced DNA damage. Importantly, paclitaxel eliminated cellular senescence, as observed by SA-β-Gal staining. Cellular senescence elimination was associated with p53/p21 and p16/pRb signaling inactivation. Conclusions: Given these findings, paclitaxel may be a promising anticancer drug and offer a new therapeutic strategy for managing gefitinib-resistant NSCLC during the COVID-19 pandemic.

Lurbinectedin (PM01183), a selective inhibitor of active transcription, effectively eliminates both cancer cells and cancer stem cells in preclinical models of uterine cervical cancer.

Objective The objective of this study was to evaluate the antitumor effects of lurbinectedin on cervical cancer with a special focus on its effects on cancer stem cells (CSCs). Methods Using two cervical cell lines (ME180 and CaSki cells), the antitumor effects of lurbinectedin were assessed in vitro using the MTS assay and colony formation assay. The growth inhibitory effects of paclitaxel and cisplatin were also evaluated as controls. By employing ALDH1 activity as a marker of CSCs, the antitumor effects of lurbinectedin on cervical CSCs and non-CSCs were individually evaluated. Finally, we investigated the mechanisms by which lurbinectedin eliminated cervical CSCs. Results Lurbinectedin had significant antitumor activity toward cervical cancer cells at low nanomolar concentrations in vitro. Mouse xenografts of cervical cancer revealed that lurbinectedin significantly inhibits tumor growth. The growth-inhibitory effect of lurbinectedin was greater than that of cisplatin and paclitaxel. ALDH-high CSCs were observed in both cervical cancer cell lines (4.4% and 2.4% in ME180 and CaSki cells, respectively). Lurbinectedin downregulated stem cell-related gene expression (Oct4, Nanog, and SOX2), inhibited HDAC1 activity, and effectively eliminated ALDH-high CSCs. Conclusions Lurbinectedin is highly effective on uterine cervical cancer because it eliminates CSCs, and lurbinectedin is a promising agent to overcome platinum resistance in cervical cancer.

Elevated alpha1-acid glycoprotein in gastric cancer patients inhibits the anticancer effects of paclitaxel, effects restored by co-administration of erythromycin.

Paclitaxel (PTX) which easily elutes into ascites is widely used to treat gastric cancer patients with peritoneal carcinomatosis (PC), but clinical outcomes are suboptimal. Increased concentrations of α1-acid glycoprotein (AGP), an important drug-binding protein, have been reported in the plasma and ascites of cancer patients. This study sought to clarify whether AGP binds to PTX and alters its anticancer effects. AGP concentrations were measured in the serum and ascites of gastric cancer patients with PC and in the serum of healthy volunteers. The in vitro effects of AGP and AGP plus erythromycin (EM) on PTX were evaluated by MTT assays in the gastric cancer cell lines. We also measured AGP concentrations in the ascites of PC model mice and examined the effects of EM plus PTX on PC. The mean AGP concentrations in the serum and ascites of gastric cancer patients with PC were 1524 and 834 μg/mL, respectively, higher than the mean AGP concentration of 650 μg/mL observed in the sera of healthy volunteers. AGP > 400 μg/mL significantly suppressed the cell growth inhibitory effect of PTX in vitro, but the co-administration of EM restored it. Elevated AGP concentrations were observed in the ascites of PC model mice. Administration of PTX alone did not markedly diminish PC, whereas co-administration of PTX and EM significantly reduced PC (p = 0.011). AGP is an important regulatory factor modulating the anticancer activity of intraperitoneal PTX. The co-administration of PTX and EM may be effective in treating gastric cancer patients with PC.

Methylseleninic Acid Enhances Paclitaxel Efficacy for the Treatment of Triple-Negative Breast Cancer

A major challenge in breast cancer therapy is the lack of an effective therapeutic option for a particularly aggressive subtype of breast cancer, triple-negative breast cancer. Here we provide the first preclinical evidence that a second-generation selenium compound, methylseleninic acid, significantly enhances the anticancer efficacy of paclitaxel in triple-negative breast cancer. Through combination-index value calculation, we demonstrated that methylseleninic acid synergistically enhanced the growth inhibitory effect of paclitaxel in triple-negative breast cancer cells. The synergism was attributable to more pronounced induction of caspase-mediated apoptosis, arrest of cell cycle progression at the G2/M checkpoint, and inhibition of cell proliferation. Treatment of SCID mice bearing MDA-MB-231 triple-negative breast cancer xenografts for four weeks with methylseleninic acid (4.5 mg/kg/day, orally) and paclitaxel (10 mg/kg/week, through intraperitoneal injection) resulted in a more pronounced inhibition of tumor growth compared with either agent alone. The attenuated tumor growth correlated with a decrease in tumor cell proliferation and an induction of apoptosis. The in vivo study also indicated the safety of using methylseleninic acid in the combination regime. Our findings thus provide strong justification for the further development of methylseleninic acid and paclitaxel combination therapy for the treatment of triple-negative breast cancer.

Poly I:C inhibits cell proliferation and enhances the growth inhibitory effect of paclitaxel in oral sqaumous cell carcinoma

Objective. Toll-like receptors (TLR) signaling has dual effect of promoting tumor progression and anti-cancer property. This study was designed to determine the effect of polyinosinic-polycytidilic acid (poly I:C), a TLR3 agonist, on the proliferation of oral cancer cells. Materials and methods: Human oral squamous cell carcinoma cell lines, YD-10B and YD-8, were used. TLRs expression was examined by RT-PCR and IL-8 production by poly I:C was examined by ELISA. Cell proliferation was determined by MTT assay. Flow cytometry and Western blot analysis were performed to determine the molecular mechanism of poly I:C-induced cell death. Results. TLR3 was functionally expressed in YD-10B and YD-8 cells. Treatment of poly I:C inhibited the cell growth in a dose-dependent manner. Flow cytometry and Western blot analysis revealed that poly I:C induced apoptosis via a mitochondria-dependent pathway. In addition, combination treatment with poly I:C and paclitaxel more significantly inhibited cell proliferation compared with poly I:C or paclitaxel alone. Conclusions. Poly I:C effectively inhibits oral cancer cell proliferation and can be considered as a candidate to improve the inhibitory effect of anti-cancer drugs.

3′-O, 4′-O-aromatic acyl substituted 7,8-pyranocoumarins: a new class of P-glycoprotein modulators

P-glycoprotein (Pgp) overexpression in tumour cells leads to multidrug resistance (MDR) and causes failure in cancer chemotherapy. We have previously identified (±)-praeruptorin A (PA) as a potential lead compound for Pgp modulators. In this study we investigated the MDR-reversing activities of PA derivatives. Series 7,8-pyranocoumarins with various C-3' and C-4' side chains had been semi-synthesized and their MDR-reversing activity was investigated in Pgp-overexpressing MDR tumour cell line HepG2/Dox and in a KB V1 xenograft animal model. All 7,8-pyranocoumarins exhibited equal or higher activity in modulating Pgp. DCK (12), DMDCK (15), 16, 21, 23 and 24 at 4 µm achieved 91%∼99% decrease in IC50 value (concentration inhibiting cell growth by 50%) of anticancer agents vinblastine, doxorubicin, puromycin and paclitaxel, and were more active than others. DMDCK also remarkably enhanced the growth inhibitory effect of paclitaxel on KB V1 xenografts (P < 0.05), showing a potency required for clinical usage. Mechanistic studies suggested that these 7,8-pyranocoumarins might reverse Pgp-MDR through directly binding to substrate binding site(s) or allosteric site(s) on Pgp therefore impairing Pgp-mediated drug transport. Results from the study suggested that 3'-O, 4'-O-aromatic acyl substituted 7,8-pyranocoumarins could serve as a new class of Pgp modulator. Acyls play an important role in maintaining and enhancing the Pgp-modulating ability of pyranocoumarins. 3,4-Dimethoxyl substituted aromatic acyls, bearing a methoxy that might interact with Pgp as hydrogen bond accepter, were shown to be the most potent for reversing MDR.

Re-expression of ARHI (DIRAS3) induces autophagy in breast cancer cells and enhances the inhibitory effect of paclitaxel

BackgroundARHI is a Ras-related imprinted gene that inhibits cancer cell growth and motility. ARHI is downregulated in the majority of breast cancers, and loss of its expression is associated with its progression from ductal carcinoma in situ (DCIS) to invasive disease. In ovarian cancer, re-expression of ARHI induces autophagy and leads to autophagic death in cell culture; however, ARHI re-expression enables ovarian cancer cells to remain dormant when they are grown in mice as xenografts. The purpose of this study is to examine whether ARHI induces autophagy in breast cancer cells and to evaluate the effects of ARHI gene re-expression in combination with paclitaxel.MethodsRe-expression of ARHI was achieved by transfection, by treatment with trichostatin A (TSA) or by a combination of TSA and 5-aza-2'-deoxycytidine (DAC) in breast cancer cell cultures and by liposomal delivery of ARHI in breast tumor xenografts.ResultsARHI re-expression induces autophagy in breast cancer cells, and ARHI is essential for the induction of autophagy. When ARHI was re-expressed in breast cancer cells treated with paclitaxel, the growth inhibitory effect of paclitaxel was enhanced in both the cell culture and the xenografts. Although paclitaxel alone did not induce autophagy in breast cancer cells, it enhanced ARHI-induced autophagy. Conversely, ARHI re-expression promoted paclitaxel-induced apoptosis and G2/M cell cycle arrest.ConclusionsARHI re-expression induces autophagic cell death in breast cancer cells and enhances the inhibitory effects of paclitaxel by promoting autophagy, apoptosis, and G2/M cell cycle arrest.

Digitoxin activates EGR1 and synergizes with paclitaxel on human breast cancer cells.

Background:Numerous studies have suggested that digitalis derivatives promise to be superior to existing adjuvant therapy for breast cancer as to effects and side-effects. In the present study, we have used gene expression analysis to determine the molecular action of digitoxin on breast cancer cells and assessed digitoxin’s ability to synergize with the chemotherapy agent paclitaxel with respect to inhibition of cell proliferationMaterials and Methods:We treated (Her2 overexpressing, ER low) MDA-MB-453 human breast cancer cells with digitoxin at four doses {20 ng/ml (26 nM) to 1 μg/ml} and collected RNA at 6 h and 24 h for gene expression analysis. To examine the effects on ER positive cells, we treated MCF7 cells with digitoxin at 1 μg/ml and collected RNA for RT-PCR analysis. In addition, we assayed the growth inhibitory effect of low doses of digitoxin combined with paclitaxel and determined combination index values.Results:To reveal primary effects, we examined digitoxin’s effect 6 h post-treatment with the highest dose, 1μg/ml, and found upregulation of the stress response genes EGR-1 and NAB2, lipid biosynthetic genes and the tumor suppressor gene p21, and downregulation of the mitotic cell cycle gene CDC16 and the replication gene PolR3B. RT-PCR analysis validated effects on stress response, apoptotic and cell cycle genes on MDA-MB-453 and MCF7 cells. Western blot analysis confirmed induction of EGR1 protein at 1 h and ATF3 at 24 h. Paclitaxel, as well as digitoxin, inhibited the in vitro activity of the purified Na+-K+-ATPase; digitoxin enhanced the growth inhibitory effects of paclitaxel on Her2 overexpressing breast cancer cells.Conclusions:Our studies show the potential of digitoxin to prevent and treat breast cancer and indicate that the combination of digitoxin and paclitaxel is a promising treatment for ER negative breast cancer. These findings are the first to alert physicians to the possible dangers to patients who take a combination of digitoxin and paclitaxel. The potential dangers ensuing when paclitaxel and digitoxin are combined are dependent on the dose of digitoxin.

Curcumin Suppresses the Paclitaxel-Induced Nuclear Factor-κB in Breast Cancer Cells and Potentiates the Growth Inhibitory Effect of Paclitaxel in a Breast Cancer Nude Mice Model

Most anticancer agents activate nuclear factor kappa B (NF-kappaB), which can mediate cell survival, proliferation, and metastasis. Curcumin has been shown to inhibit the growth of various cancer cells, without toxicity to normal cells. The antitumor effects of curcumin could be due in part to the inactivation of NF-kappaB. We hypothesize that blocking NF-kappaB activity may augment paclitaxel cancer chemotherapy. In this study, we investigated whether the inactivation of NF-kappaB by curcumin would enhance the efficacy of paclitaxel for inhibiting breast cancer growth in vitro and in vivo. We confirmed that curcumin inhibited paclitaxel-induced activation of NF-kappaB and potentiated the growth inhibitory effect of paclitaxel in MDA-MB-231 breast cancer cells. The combination of curcumin with paclitaxel elicited significantly greater inhibition of cell growth and more apoptosis, compared with either agent alone. In an experimental breast cancer murine model using MDA-MB-231 cells, combination therapy with paclitaxel and curcumin significantly reduced tumor size and decreased tumor cell proliferation, increased apoptosis, and decreased the expression of matrix metalloprotease 9 compared with either agent alone. These results clearly suggest that a curcumin-paclitaxel combination could be a novel strategy for the treatment of breast cancer.

Combining the farnesyltransferase inhibitor lonafarnib with paclitaxel results in enhanced growth inhibitory effects on human ovarian cancer models in vitro and in vivo

Objectives. To determine the effects of combining lonafarnib with paclitaxel on the growth of human ovarian cancer cells and tumor xenografts as well as to monitor a pharmacodynamic marker of farnesyltransferase inhibition (HDJ-2) in peripheral blood mononuclear cells (PBMCs) isolated from tumor-bearing animals after treatment with this combination. Methods. Proliferation of A2780, PA-1, IGROV-1, and TOV-112D cells was assessed after treatment with lonafarnib and paclitaxel. Cell cycle progression was determined by flow cytometry, and apoptosis was evaluated by assaying for caspase-3 and cleaved PARP. The effects of lonafarnib and paclitaxel on the tumor growth of each model were determined in immunocompromised mice. Proteins extracted from cells, tumors, and PBMCs were assayed for HDJ-2 mobility shifts by Western blotting as well as for farnesyl protein transferase (FTase) enzyme activity by biochemical analyses. Results. In A2780, PA-1, IGROV-1, and TOV-112D cells lonafarnib potentiated the growth inhibitory effects of paclitaxel. In each of the models lonafarnib enhanced paclitaxel-induced mitotic arrest and apoptosis. The combination of lonafarnib plus paclitaxel resulted in marked tumor regressions in A2780, TOV-112D, PA-1, and IGROV-1 tumor xenografts. Western blotting demonstrated that in PBMCs isolated from the animals, paclitaxel treatment suppressed lonafarnib-induced HDJ-2 mobility shifts. Paclitaxel did not affect lonafarnib inhibition of FTase enzyme activity levels in these PBMCs. Conclusions. Lonafarnib enhances the antiproliferative effects of paclitaxel on ovarian cancer cells in vitro and ovarian tumor xenografts in vivo. Measuring FTase enzyme activity levels rather than HDJ-2 shifts in PBMCs may be a more accurate biomarker to predict levels of farnesyltransferase inhibition in patients who are also receiving paclitaxel chemotherapy.

In vitro sensitivity of human endometrial cancer cell lines to paclitaxel or irinotecan (CPT-11) in combination with other aniticancer drugs

We have evaluated the growth inhibitory effects of paclitaxel alone or irinotecan (CPT-11) alone and their combined effects with other drugs on human endometrial cancer cell lines. IC50 doses of paclitaxel (Tx), SN-38 (active metabolite of CPT-11; 7-ethyl-10-hydroxycamptothecin) and cisplatin, including other drugs which have been used for treatment of patients with endometrial cancer, were examined using five human endometrial cancer cell lines (Ishikawa, HEC-1A, HEC-50B, HEC-59 and HEC-108). When in vitro sensitivity was defined IC50 lower than 10% of the peak plasma concentration (PPC), all endometrial cancer cell lines were sensitive to paclitaxel and three of five endometrial cancer cell lines were sensitive to SN-38, whereas cisplatin was not active against any endometrial cancer cell lines used in this study. Regarding the other drugs, aclarubicin (ACR) and actinomycin D (ACD) were active against four of five endometrial cancer cell lines, etoposide (VP-16) and pirarubicin (THP) against two, and 5-fluorouracil (5-FU) against only one, while ifosfamide (4-OHIFO) was not active against any endometrial cancer cell lines. When combined effects of paclitaxel or SN-38 with other one drug were determined by the median-effect analysis, paclitaxel followed by cisplatin resulted in synergistic effects to all endometrial cancer cell lines. Paclitaxel followed by SN-38 also had synergistic effects to four cell lines. Sequential but not simultaneous administration of taxol and THP-adriamycin showed synergistic effects to three cell lines. In combinations of SN-38 with other drugs, simultaneous administration of SN-38 and cisplatin resulted in synergistic effects to all cell lines. It is noteworthy that ACD followed by SN-38 showed synergistic effects to all cell lines, and simultaneous treatment of ACD and SN-38 or SN-38 followed by ACD also resulted in synergistic effects to three cell lines. THP-adriamycin followed by SN-38 had synergistic effects to four cell lines. The present quantitative data analysis for synergism provides a basis for a rational design of clinical protocols for combination chemotherapy in patients with endometrial cancer of the uterus.

Multidrug Resistance Phenotype and Paclitaxel (Taxol®) Sensitivity in Human Renal Carcinoma Cell Lines of Different Histologic Types

We compared the effects of paclitaxel (Taxol®) in human renal cell carcinoma (RCC) of different histologic types. The growth inhibiotory effects of paclitaxel on 34 human RCC cell lines of strictly defined different histologic types were determined by 3–[4,5-dimethylthiazilyl]-2,5-diphenyltetrazoliumbromide (MTT) assays. Paclitaxel-induced morphologic alterations were visualized by light and immunofluorescence and by transmission electron microscopy. The expression and function of P-glyco-protein arid multidrug resistance-associated protein (MRP) were defined by reverse transcriptase polytnercise chain reaction and fluorescence-activated cell sorting (FACS) analysis, respectively. Modulation of P-glycoprotein function was performed by verapamil or Cretnophor EL. A significant (p < 0.05') dose-dependent paclitaxel-induced growth inhibition could be demonstrated in all cell lines, with the effects of paclitaxel dissolved in Cremophor® EL/ethanol (= Taxol®) exceeding the effects of piclitaxel dissolved in dimethyl sulfoxide. The extent of response markedly varied between the different cell lines, although chromophilic RCCs exhibited a more pronounced response to Taxol (IC50: 0.03–0.38 μM) than clear cell RCCs (IC50,: 0.01–36.69 μM). Exposure to paclitaxe/Taxol® induced an increuse of micro-tubule bundles in the clear cell and the chromophobe RCCs but not in the chromophilic RCCs. The expression of the MRP was low in RCC cell lines and was not found to be related to paclitaxel/Taxol® sensitivity. In contrast, the expression level of P-glycoprotein was much more pronounced and showed a positive correlation (p < 0.05) with the response to paditaxel. Reversal of P-glycoprotein function by verapamil or Cremophor® EL enhanced the growth inhibitory effects of paclitaxel and further supported the role of P-glycoprotein for paclitaxel sensitivity of human RCCs. Paclitaxel/Taxol® effktively inhibits proliferation of human RCCs in vitro, irrespective of their histologic types. Moreover, expression and function of P-glycoprotein markedly contribute to paclitaxel responsiveness, although other as yet undefined drug resistance mechanisms are effective in humun RCCs us well.

Local Growth Inhibitory Effect of Paclitaxel Released by a Biodegradable Stent Coating on Vascular Smooth Muscle Cells

Local Growth Inhibitory Effect of Paclitaxel Released by a Biodegradable Stent Coating on Vascular Smooth Muscle Cells

Antiproliferative effects of paclitaxel (Taxol) on human renal clear cell carcinomas in vitro.

The aim of this study was to analyse the direct antiproliferative effects of paclitaxel on 20 different renal clear cell carcinoma (RCCC) cell lines comparing the effects of paclitaxel dissolved in either DMSO or Cremophor EL/ethanol (Taxol). The MTT assay was used to determine the growth inhibition of the cell lines by paclitaxel. In addition, micronuclei and microtubule alterations were examined by light and immunofluorescence microscopy. A significant (P < 0.05) dose-dependent inhibition of proliferation was evident in 19 out of 20 cell lines after exposure to paclitaxel dissolved in DMSO and in all cell lines after exposure to paclitaxel in Cremophor EL/ethanol. The extent of response markedly varied between the different cell lines ranging from modest effects to reduction of cell viability down to 1-2% of the control. The effects of paclitaxel in Cremophor EL/ethanol proved to be more pronounced than the effects of paclitaxel dissolved in DMSO. This observation could be explained by additional growth inhibitory effects of Cremophor EL alone. Light microscopy revealed extensive micronucleus formation after treatment with paclitaxel. However, the failure to demonstrate differences of micronucleus formation in paclitaxel-responsive and non-responsive RCCC cell lines argued against a causal relationship between micronucleus formation and growth inhibition. Immunofluorescence microscopy revealed no differences in the formation of abnormal microtubules in cell lines responsive or non-responsive to the growth inhibitory effects of paclitaxel. Further investigations, therefore, are needed to understand the mechanisms determining the response of RCCCs to paclitaxel treatment.