Induction of tubulin by docetaxel is associated with p53 status in human non small cell lung cancer cell lines

Impact of Docetaxel on blood-brain barrier function and formation of breast cancer brain metastases

BACKGROUND

Breast cancer (BC) is the most frequent malignant tumor in females and the 2nd most common cause of brain metastasis (BM), that are associated with a fatal prognosis. The increasing incidence from 10% up to 40% is due to more effective treatments of extracerebral sites with improved prognosis and increasing use of MRI in diagnostics. A frequently administered, potent chemotherapeutic group of drugs for BC treatment are taxanes usually used in the adjuvant and metastatic setting, which, however, have been suspected to be associated with a higher incidence of BM. The aim of our study was to experimentally analyze the impact of the taxane docetaxel (DTX) on brain metastasis formation, and to elucidate the underlying molecular mechanism.

METHODS

A monocentric patient cohort was analyzed to determine the association of taxane treatment and BM formation. To identify the specific impact of DTX, a murine brain metastatic model upon intracardial injection of breast cancer cells was conducted. To approach the functional mechanism, dynamic contrast-enhanced MRI and electron microscopy of mice as well as in-vitro transendothelial electrical resistance (TEER) and tracer permeability assays using brain endothelial cells (EC) were carried out. PCR-based, immunohistochemical and immunoblotting analyses with additional RNA sequencing of murine and human ECs were performed to explore the molecular mechanisms by DTX treatment.

RESULTS

Taxane treatment was associated with an increased rate of BM formation in the patient cohort and the murine metastatic model. Functional studies did not show unequivocal alterations of blood-brain barrier properties upon DTX treatment in-vivo, but in-vitro assays revealed a temporary DTX-related barrier disruption. We found disturbance of tubulin structure and upregulation of tight junction marker claudin-5 in ECs. Furthermore, upregulation of several members of the tubulin family and downregulation of tetraspanin-2 in both, murine and human ECs, was induced.

CONCLUSION

In summary, a higher incidence of BM was associated with prior taxane treatment in both a patient cohort and a murine mouse model. We could identify tubulin family members and tetraspanin-2 as potential contributors for the destabilization of the blood-brain barrier. Further analyses are needed to decipher the exact role of those alterations on tumor metastatic processes in the brain.

High pemetrexed sensitivity of docetaxel-resistant A549 cells is mediated by TP53 status and downregulated thymidylate synthase

The chemoresistance of non-small cell lung cancer (NSCLC) that occurs in docetaxel (DOC) chemotherapy substantially decreases the survival of patients. To overcome DOC-induced chemoresistance, we established DOC-selected A549 lung cancer sublines (A549/D16 and A549/D32) and revealed that both sublines were cross-resistant to vincristine (VCR) and doxorubicin (DXR). Notably, both sublines were more sensitive to pemetrexed (PEM) than parental cells according to MTT and clonogenic assays. The expression levels of thymidylate synthase (TS) and γ-glutamyl hydrolase (GGH) were downregulated in DOC-resistant sublines. When exogenous TS was overexpressed in A549/D16 cells, PEM sensitivity was significantly decreased, however it was not decreased by overexpression of exogenous GGH. PEM treatment induced more apoptotic sub-G1 cells in both DOC-resistant sublines and in the in vivo PEM sensitivities of A549/D16 cells. These findings were further confirmed by a xenografted tumor model. To unmask the mediator of TS downregulation, we investigated human lung cancer cell lines that have various TP53 statuses using DOC treatment. The level of TS protein was significantly decreased in wild-type TP53-containing cells with DOC treatment; TS expression levels were not affected in mutant-TP53 and TP53-null cells under the same conditions. Furthermore, when the expression of TP53 was inhibited in A549 cells, the expression level of TS was increased. Our data indicated that DOC activated wild-type TP53 and suppressed TS expression under continuous DOC exposure. Therefore, the expression of TS remained at low levels in DOC-resistant A549 cancer cells. Our data revealed that for lung cancer with DOC resistance and wild-type TP53 status, the administration of PEM as a second-line agent to overcome DOC-resistance may benefit patients.

Cytochrome P450 2E1 (CYP2E1) regulates the response to oxidative stress and migration of breast cancer cells

Introduction

The cytochrome P450 (CYP) enzymes are a class of heme-containing enzymes involved in phase I metabolism of a large number of xenobiotics. The CYP family member CYP2E1 metabolises many xenobiotics and pro-carcinogens, it is not just expressed in the liver but also in many other tissues such as the kidney, the lung, the brain, the gastrointestinal tract and the breast tissue. It is induced in several pathological conditions including cancer, obesity, and type II diabetes implying that this enzyme is implicated in other biological processes beyond its role in phase I metabolism. Despite the detailed description of the role of CYP2E1 in the liver, its functions in other tissues have not been extensively studied. In this study, we investigated the functional significance of CYP2E1 in breast carcinogenesis.

Methods

Cellular levels of reactive oxygen species (ROS) were measured by H₂DCFDA (2 2.9.2 2′,7′-dichlorodihydrofluorescein diacetate) staining and autophagy was assessed by tracing the cellular levels of autophagy markers using western blot assays. The endoplasmic reticulum stress and the unfolded protein response (UPR) were detected by luciferase assays reflecting the splicing of mRNA encoding the X-box binding protein 1 (XBP1) transcription factor and cell migration was evaluated using the scratch wound assay. Gene expression was recorded with standard transcription assays including luciferase reporter and chromatin immunoprecipitation.

Results

Ectopic expression of CYP2E1 induced ROS generation, affected autophagy, stimulated endoplasmic reticulum stress and inhibited migration in breast cancer cells with different metastatic potential and p53 status. Furthermore, evidence is presented indicating that CYP2E1 gene expression is under the transcriptional control of the p53 tumor suppressor.

Conclusions

These results support the notion that CYP2E1 exerts an important role in mammary carcinogenesis, provide a potential link between ethanol metabolism and breast cancer and suggest that progression, and metastasis, of advanced stages of breast cancer can be modulated by induction of CYP2E1 activity.

Novel hydrophilic docetaxel (CQMU-0519) analogue inhibits proliferation and induces apoptosis in human A549 lung, SKVO3 ovarian and MCF7 breast carcinoma cell lines

OBJECTIVE

Objectives of this investigation were not merely to perform a comparative study with original docetaxel, but to define anti-proliferative and apoptotic effects of novel hydrophilic docetaxel (CQMU-0519) analogue on A549 lung, SKVO3 ovary and MCF7 breast carcinoma cell lines.

MATERIALS AND METHODS

The materials for the study consist of a completely new docetaxel analogue (CQMU-0519), synthesized by the Department of Pharmacology, Chongqing Medical University, China, which is completely soluble in water. 50 nm of drug concentration was utilized on all three cell lines where cell population growth was assessed using cell culture kit-8 and flow cytometry analysis, whereas apoptotic pathways were unveiled by use of annexin-V FITC, apoptosis DNA ladder, caspases-3, 6, 8 and 9; in the meanwhile, regulation of Bcl-2 family members was analysed by western blotting.

RESULT

The novel docetaxel analogue (CQMU-0519) suppressed cell proliferation in all three cell lines, inhibition of cell proliferation and cell cycle arrest being more evident in G(2) /M phase. Also, in both lung and ovarian cell lines, apoptotic levels were higher as measured by the various tests performed, and downregulation of Bcl-2 and Bcl-xL with increased expressions of Bad and Bax indicated the intrinsic pathway for apoptosis. Nevertheless, it was found that MCF7 cells, although also manifesting high levels of apoptosis, used the extrinsic pathway instead. Hence, it was shown that novel docetaxel analogue (CQMU-0519) may have some prospective use in future clinical trials.

CONCLUSIONS

Novel hydrophilic docetaxel analogue (CQMU-0519) inhibited cell proliferation and enhanced the intrinsic apoptotic pathway in lung and ovarian carcinoma cells, whereas it used the extrinsic one in breast adenocarcinoma cells.

Regulation of chemosensitivity and migration by clusterin in non-small cell lung cancer cells

PURPOSE

In terms of drug resistance, cancer cells usually benefit from high clusterin (CLU) expression on chemotherapy. In contrast, CLU expression has been found to be a favorable prognostic factor in lung cancer patients. The aims of this study are to determine the association between CLU expression and chemotherapeutic sensitivity and the potential role of CLU in migration in human non-small-cell lung cancer (NSCLC) cell lines.

METHODS

The levels of clusterin in NSCLC cell lines were altered by short hairpin RNA interference (shRNAi) and overexpression on chemosensitivity assay. Migratory ability of these cell lines was also investigated.

RESULTS

H1355 cells with the highest level of CLU demonstrated the lowest sensitivities to Adriamycin (ADR), docetaxel (DOC), and gemcitabine (GEM) treatment. Inhibition of CLU expression in H1355 cells resulted in higher chemosensitivities. When CLU was stably overexpressed in A549 and H1299 cells, only the chemosensitivity to ADR was reduced. The migratory ability of CLU-overexpressing cells significantly decreased. Moreover, MMP2 transcription was inhibited in CLU-overexpressing H1299 cells. These results indicated lower metastatic potential for cancer cells with high CLU level.

CONCLUSION

Lung cancer cells with high level of CLU have reduced chemosensitivity. High level of CLU may result in migratory inhibition and thus favorable prognosis in lung cancer.

Randomized phase II trial of concurrent versus sequential bortezomib plus docetaxel in advanced non-small-cell lung cancer: a California cancer consortium trial

BACKGROUND

The proteasome inhibitor bortezomib sensitizes tumor cells to chemotherapy-induced apoptosis. In preclinical non-small-cell lung cancer (NSCLC) models, p53-dependent growth arrest after bortezomib treatment resulted in reduced cytotoxicity if bortezomib preceded docetaxel. The reverse sequence of docetaxel before bortezomib was associated with increased apoptosis, cleavage of caspase-3 and PARP (poly [ADP-ribose] polymerase), and reduction in Bcl-2. A prospective randomized phase II trial of concurrent versus sequential docetaxel and bortezomib was conducted to assess whether administration sequence resulted in measurable clinical differences.

PATIENTS AND METHODS

Previously treated patients with advanced NSCLC were randomized to concurrent (CON) or sequential (SEQ) docetaxel (75 mg/m² intravenous [I.V.]) followed by bortezomib, every 3 weeks. In the CON arm, bortezomib (1.6 mg/m² I.V.) was given on days 1 and 8, and in the SEQ arm, it was given on days 2 and 8. Previous erlotinib as well as treated or controlled brain metastases were allowed. The primary endpoint was objective response rate (RR); progression-free (PFS) and overall survival (OS) were secondary endpoints.

RESULTS

Eighty-one patients were randomized (40 CON and 41 SEQ). Grade 3+ toxicities were mostly due to myelosuppression. One patient each had grade 4 hyponatremia and syncope. Toxicities were similar between the arms. There was 1 treatment-related death in the SEQ arm. There were 8 partial responders, 4 in each arm, for an overall RR of 10%. Disease control rate was similar in both arms (50% vs. 49%). Median PFS was 12 weeks in the CON arm and 11 weeks in the SEQ arm. Median OS times in the CON and SEQ arms were 13.3 and 10.5 months, respectively.

CONCLUSION

Docetaxel plus bortezomib given sequentially or concurrently has similar RR and PFS. Median survival in the SEQ arm exceeds published survival estimates for either agent alone or in combination. Any further studies in this population would require molecular characterization of a phenotype most likely to benefit from proteasome inhibitor therapy.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

Hepatitis delta virus epigenetically enhances clusterin expression via histone acetylation in human hepatocellular carcinoma cells

Both isoforms of the hepatitis delta antigen (HDAg) of hepatitis delta virus (HDV) are highly associated with virus proliferation and may act as co-activators of cellular gene expression. Human hepatocellular carcinoma (HCC) cell line Huh7, which stably expresses HDAgs, was differentially screened and the results showed that clusterin gene expression was enhanced. The mechanisms for HDAg-mediated clusterin gene upregulation were investigated. Expression of HDAgs was associated with enhanced histone H3 acetylation within the clusterin promoter in a chromatin immunoprecipitation assay. Transient transfection of HDAg-expressing plasmids into Huh7 cells also enhanced clusterin expression and histone acetylation. Furthermore, HDV replication was associated with histone hyperacetylation and clusterin induction. The effect of increased clusterin expression was determined by a chemosensitivity assay with adriamycin treatment. These data indicated that HDV-induced clusterin protein increases cell survival potential. Thus, it is possible that epigenetic regulation by HDV contributes to a pathological outcome of hepatitis D/hepatitis B viral hepatitis and HCC.

Promoter methylation of O(6)-methylguanine-DNA-methyltransferase in lung cancer is regulated by p53

Methylation of the O(6)-methylguanine-DNA-methyltransferase (MGMT) promoter is associated with G:C to A:T transitions in the p53 gene in various human cancers, including lung cancer. In tumors with p53 mutation, MGMT promoter methylation is more common in advanced tumors than in early tumors. However, in tumors with wild-type p53, MGMT promoter methylation is independent of tumor stage. To elucidate whether p53 participates in MGMT promoter methylation, we engineered three cell models: A549 cells with RNA interference (RNAi)-mediated knockdown of p53, and p53 null H1299 cells transfected with either wild-type p53 (WT-p53) or mutant-p53 (L194R, and R249S-p53). Knockdown of endogenous p53 increased MGMT promoter methylation in A549 cells, and transient expression of WT-p53 in p53 null H1299 cells diminished MGMT promoter methylation, whereas the MGMT promoter methylation status were unchanged by expression of mutant-p53. Previous work showed that p53 modulates DNA-methyltransferase 1 (DNMT1) expression; we additionally examined chromatin remodeling proteins expression levels of histone deacetylase 1 (HDAC1). We found that p53 knockdown elevated expression of both DNMT1 and HDAC1 in A549 cells. Conversely, expressing WT-p53 in p53 null H1299 cells reduced DNMT1 and HDAC1 expression, but the reduction of both proteins was not observed in expressing mutant-p53 H1299 cells. CHIP analysis further showed that DNMT1 and HDAC1 binding to the MGMT promoter was increased by MGMT promoter methylation and decreased by MGMT promoter demethylation. In conclusion, MGMT promoter methylation modulated by p53 status could partially promote p53 mutation occurrence in advanced lung tumors.

Dulxanthone A induces cell cycle arrest and apoptosisvia up-regulation of p53 through mitochondrial pathway in HepG2 cells

Natural products derived from plants provide a rich source for development of new anticancer drugs. Dulxanthone A was found to be an active cytotoxic component in Garcinia cowa by bioactivity-directed isolation. Studies to elucidate the cytotoxic mechanisms of dulxanthone A showed that dulxanthone A consistently induced S phase arrest and apoptosis in the most sensitive cell line HepG2. Furthermore, p53 was dramatically up-regulated, leading to altered expression of downstream proteins upon dulxanthone A treatment. Cell cycle related proteins, such as cyclin A, cyclin B, cyclin E, cdc-2, p21 and p27 were down-regulated. Some apoptosis correlated proteins were also altered following the drug treatment. Bcl-2 family members PUMA was up-regulated while Bcl-2 and Bax were down-regulated. However, the expression ratio of Bax/Bcl-2 was increased. This resulted in the release of cytochrome C from the mitochondria to the cytosol. Concurrently, Apaf-1 was stimulated with p53 by dulxanthone A. In result, cytochrome C, Apaf-1 and procaspase-9 form an apoptosome, which in turn triggered the activation of caspase-9, caspase-3 and downstream caspase substrates. Lamin A/C and PARP were down-regulated or cleaved, respectively. Moreover, cell cycle arrest and apoptosis in HepG2 cells induced by dulxanthone A were markedly inhibited by siRNA knockdown of p53. In summary, dulxanthone A is an active cytotoxic component of G. cowa. It induces cell cycle arrest at lower concentrations and triggers apoptosis at higher concentrations via up-regulation of p53 through the intrinsic mitochondrial pathway in HepG2 cells. Dulxanthone A is therefore likely a promising preventive and/or therapeutic agent against Hepatoma.

Class III beta-tubulin overexpression is a marker of poor clinical outcome in advanced ovarian cancer patients

PURPOSE

Overexpression of beta III tubulin has been involved in paclitaxel resistance in several experimental models. We investigated the role of beta III tubulin as predictor of clinical outcome in ovarian cancer patients given platinum/paclitaxel treatment. We also investigated whether beta III tubulin expression could be modified after the selective pressure represented by chemotherapy in vivo.

EXPERIMENTAL DESIGN

The study was designed to include a series of consecutive ovarian cancer patients with unresectable disease at time of first surgery, who underwent interval debulking surgery with pathologic assessment of response to treatment with platinum/paclitaxel chemotherapy. Immunostaining was done on formalin-fixed, paraffin-embedded tissue sections from pretreatment and posttreatment tissue biopsies by using the polyclonal rabbit anti-class III beta-tubulin antibody.

RESULTS

beta III Tubulin immunoreaction was observed in 51 of 62 (82.2%) cases. beta III Tubulin positivity was neither associated with clinicopathologic variables nor with pathologic response to chemotherapy. Significantly lower percentages of beta III tubulin positivity were observed in posttreatment (range, 5-80%; median, 20%) versus pretreatment (range 10-100%; median, 40%) tissue biopsies (P = 0.0011). Cases with high beta III tubulin expression showed a worse overall survival with respect to cases with low beta III tubulin expression (median overall survival, 25 versus 46 months; P = 0.002). Multivariate analysis showed that high content of beta III tubulin remains independently associated with a worse prognosis.

CONCLUSIONS

Assessment of beta III tubulin could be useful to identify poor prognosis ovarian cancer patients candidates to more aggressive and/or targeted therapy.

Regulation of Class II β-Tubulin Expression by Tumor Suppressor p53 Protein in Mouse Melanoma Cells in Response toVincaAlkaloid

The continuous exposure of antimicrotubule drugs to tumors often results in the emergence of drug-resistant tumor cells with altered expression of several beta-tubulin isotypes. We found that Vinca alkaloid enhanced expression of class II beta-tubulin isotype (mTUBB2) in mouse B16F10 melanoma cells via alteration of the tumor suppressor p53 protein. Vincristine treatment stimulated an increase in mTUBB2 mRNA expression and promoted accumulation of this isotype around the nuclei. Transient transfection assays employing a reporter construct, together with site-directed mutagenesis studies, suggested that the p53-binding site found in the first intron was a critical region for mTUBB2 expression. Electrophoretic mobility shift assay and associated antibody supershift experiments showed that vincristine promoted release of p53 protein from the binding site. In addition, exogenous induction of TAp63gamma (p51A), a homologue of p53, canceled the effect of vincristine on mTUBB2 expression. These results suggest that p53 protein may function as a suppressor of mTUBB2 expression and vincristine-mediated inhibition of p53 binding results in enhanced mTUBB2 expression. This phenomenon could be related with the emergence of drug-resistant tumor cells induced by Vinca alkaloid and may participate in determining the fate of these cells.