The role of betaIII tubulin in predicting chemoresistance in non-small cell lung cancer

Tubulin-β-III overexpression by uterine serous carcinomas is a marker for poor overall survival after platinum/taxane chemotherapy and sensitivity to epothilones

BACKGROUND

Uterine serous carcinoma (USC) is a subtype of endometrial cancer associated with chemoresistance and poor outcome. Overexpression of tubulin-β-III and p-glycoprotein has been linked to paclitaxel resistance in many cancers but has been undercharacterized among USCs. Epothilones have demonstrated activity in certain paclitaxel-resistant malignancies. In this study, relationships are clarified, in USCs relative to ovarian serous carcinomas (OSCs), between tubulin-β-III and p-glycoprotein expression, clinical outcome, and in vitro chemoresponsiveness to epothilone B, ixabepilone, and paclitaxel.

METHODS

Tubulin-β-III and p-glycoprotein were quantified by real-time polymerase chain reaction in 48 fresh-frozen tissue samples and 13 cell lines. Copy number was correlated with immunohistochemistry and overall survival. Median inhibitory concentration (IC50 ) was determined using viability and metabolic assays. Impact of tubulin-β-III knockdown on IC50 was assessed with small interfering RNAs.

RESULTS

USC overexpressed tubulin-β-III but not p-glycoprotein relative to OSC in both fresh-frozen tissues (552.9 ± 106.7 versus 202.0 ± 43.99, P = .01) and cell lines (1701.0 ± 376.4 versus 645.1 ± 157.9, P = .02). Tubulin-β-III immunohistochemistry reflected quantitative real-time polymerase chain reaction copy number and overexpression stratified patients by overall survival (copy number ≤ 400: 615 days; copy number > 400: 165 days, P = .049); p-glycoprotein did not predict clinical outcome. USCs remained exquisitely sensitive to patupilone in vitro despite tubulin-β-III overexpression (IC50,USC 0.245 ± 0.11 nM versus IC50,OSC 1.01 ± 0.13 nM, P = .006).

CONCLUSIONS

Tubulin-β-III overexpression in USCs discriminates poor prognosis, serves as a marker for sensitivity to epothilones, and may contribute to paclitaxel resistance. Immunohistochemistry reliably identifies tumors with overexpression of tubulin-β-III, and a subset of individuals likely to respond to patupilone and ixabepilone. Epothilones warrant clinical investigation for treatment of USCs.

The role of βIII-tubulin in non-small cell lung cancer patients treated by taxane-based chemotherapy

BACKGROUND

The aim of this study is to evaluate whether class III β-tubulin (TUBB3) expression could predict progression-free survival or overall survival in relapsed non-small cell lung cancer (NSCLC) patients treated with taxene-based chemotherapy.

METHODS

Immunohistochemistal staining was used to examine the expression of TUBB3 in resected lung tumor specimens obtained from 56 patients treated with platinum-based chemotherapy against recurrent tumors after curative resections. Excision repair cross-complementation group 1, breast cancer susceptibility gene 1, vascular endothelial growth factor, Ki-67, CD34, and p53 were also correlated with clinical features and outcome after treatment.

RESULTS

Of the 56 patients enrolled in the study, 29 were treated by carboplatin plus paclitaxel as first-line treatment, and 24 patients received docetaxel monotherapy as second- or third-line treatment. A positive TUBB3 expression is closely associated with a poor response to taxane-based chemotherapy. TUBB3 expression was an independent prognostic factor for predicting poor progression-free survival after docetaxel administration. However, TUBB3 expression could not predict outcome after carboplatin plus paclitaxel treatment. The other biomarkers tested were not independent prognostic factors for predicting outcome after taxane-based chemotherapy.

CONCLUSION

TUBB3 expression is associated with resistance to taxane-based chemotherapy and is an independent prognostic factor for predicting poor progression-free survival after docetaxel treatment alone. TUBB3 expression may be a predictive marker for chemoresistance to docetaxel in NSCLC with postoperative recurrent disease.

Differential in vitro sensitivity to patupilone versus paclitaxel in uterine and ovarian carcinosarcoma cell lines is linked to tubulin-beta-III expression

OBJECTIVE

To compare the in vitro sensitivity/resistance to patupilone versus paclitaxel in uterine and ovarian carcinosarcomas (CS).

METHODS

Five primary carcinosarcoma cell lines, two from uterine and three of ovarian origin, were evaluated for growth rate and tested for their in vitro sensitivity/resistance to patupilone versus paclitaxel by MTS assays. To identify potential mechanisms underlying the differential sensitivity/resistance to patupilone, expression levels of β-tubulin III (TUBB3) were determined with quantitative-real-time-polymerase-chain-reaction (q-RT-PCR) in primary uterine and ovarian CS cell lines and in 26 uterine and 9 ovarian CS fresh-frozen-tissues.

RESULTS

No appreciable difference in sensitivity to patupilone versus paclitaxel was noted in ovarian CS cell lines, or when uterine and ovarian CS cell lines were compared in their response to paclitaxel. In contrast, uterine CS cell lines were found to be significantly more sensitive to patupilone than to paclitaxel (P<0.002) and demostrated lower IC(50s) to patupilone (range 0.76-0.93nM) when compared to ovarian CS (range 1.9-3.4 nM, p<0.05). Higher levels of TUBB3 were detected in uterine CS cell lines and fresh frozen tissues when compared to ovarian CS (P<0.05).

CONCLUSIONS

Uterine CS cell lines are significantly more sensitive than ovarian CS cell lines to patupilone versus paclitaxel. High expression of TUBB3 is associated with sensitivity to patupilone in primary CS cell lines and may act as a genetic marker to predict chemotherapy efficacy. Patupilone may represent a promising drug in the treatment of this subset of rare but highly aggressive gynecological tumors.

Polygamain, a new microtubule depolymerizing agent that occupies a unique pharmacophore in the colchicine site

Bioassay-guided fractionation was used to isolate the lignan polygamain as the microtubule-active constituent in the crude extract of the Mountain torchwood, Amyris madrensis. Similar to the effects of the crude plant extract, polygamain caused dose-dependent loss of cellular microtubules and the formation of aberrant mitotic spindles that led to G(2)/M arrest. Polygamain has potent antiproliferative activities against a wide range of cancer cell lines, with an average IC(50) of 52.7 nM. Clonogenic studies indicate that polygamain effectively inhibits PC-3 colony formation and has excellent cellular persistence after washout. In addition, polygamain is able to circumvent two clinically relevant mechanisms of drug resistance, the expression of P-glycoprotein and the βIII isotype of tubulin. Studies with purified tubulin show that polygamain inhibits the rate and extent of purified tubulin assembly and displaces colchicine, indicating a direct interaction of polygamain within the colchicine binding site on tubulin. Polygamain has structural similarities to podophyllotoxin, and molecular modeling simulations were conducted to identify the potential orientations of these compounds within the colchicine binding site. These studies suggest that the benzodioxole group of polygamain occupies space similar to the trimethoxyphenyl group of podophyllotoxin but with distinct interactions within the hydrophobic pocket. Our results identify polygamain as a new microtubule destabilizer that seems to occupy a unique pharmacophore within the colchicine site of tubulin. This new pharmacophore will be used to design new colchicine site compounds that might provide advantages over the current agents.

An Evidence-Based Approach to the Use of Predictive Biomarkers in the Treatment of Non- Small Cell Lung Cancer (NSCLC)

Recent advances in the treatment of non-small cell lung cancer (NSCLC) have led to improvements in patient survival and quality of life. It is unclear whether molecular abnormalities associated with NSCLC cell survival, growth and proliferation are useful in predicting treatment benefit. We conducted a systematic review to establish which biomarkers contribute meaningfully to the management of NSCLC. A team of researchers searched PubMed and conference proceedings (ASCO, ESMO, IASLC, USCAP) using MESH terms for NSCLC and randomized trials (RCT), plus keywords for variables of interest. Evidence from multiple RCTs confirmed that histologic subtype is prognostic for survival and predictive of treatment efficacy and/or toxicity in NSCLC. Likewise, activating mutations of the epidermal growth factor receptor (EGFR) are associated with benefit from EGFR tyrosine kinase inhibitors in patients with advanced non-squamous NSCLC and should be assessed routinely. No biomarkers to date reliably predict response to anti-Vascular Endothelial Growth Factor (VEGF) therapies. There are inconsistent data on the role of ERCC1, BRCA, Beta tubulin III, RRM1, K-RAS, or TP-53 in treatment decisions. These tests should not be routinely used in selecting treatment at this time, whereas EML4/ALK translocations predict responses to specific targeted agents, the optimal assessment of this molecular abnormality has yet to be established. Personalized care of patients with NSCLC based on biomarkers is increasingly important to both clinical practice and research.

Peloruside- and laulimalide-resistant human ovarian carcinoma cells have βI-tubulin mutations and altered expression of βII- and βIII-tubulin isotypes

Peloruside A and laulimalide are potent microtubule-stabilizing natural products with a mechanism of action similar to that of paclitaxel. However, the binding site of peloruside A and laulimalide on tubulin remains poorly understood. Drug resistance in anticancer treatment is a serious problem. We developed peloruside A- and laulimalide-resistant cell lines by selecting 1A9 human ovarian carcinoma cells that were able to grow in the presence of one of these agents. The 1A9-laulimalide resistant cells (L4) were 39-fold resistant to the selecting agent and 39-fold cross-resistant to peloruside A, whereas the 1A9-peloruside A resistant cells (R1) were 6-fold resistant to the selecting agent while they remained sensitive to laulimalide. Neither cell line showed resistance to paclitaxel or other drugs that bind to the taxoid site on β-tubulin nor was there resistance to microtubule-destabilizing drugs. The resistant cells exhibited impaired peloruside A/laulimalide-induced tubulin polymerization and impaired mitotic arrest. Tubulin mutations were found in the βI-tubulin isotype, R306H or R306C for L4 and A296T for R1 cells. This is the first cell-based evidence to support a β-tubulin-binding site for peloruside A and laulimalide. To determine whether the different resistance phenotypes of the cells were attributable to any other tubulin alterations, the β-tubulin isotype composition of the cells was examined. Increased expression of βII- and βIII-tubulin was observed in L4 cells only. These results provide insight into how alterations in tubulin lead to unique resistance profiles for two drugs, peloruside A and laulimalide, that have a similar mode of action.

Id1 promotes lung cancer cell proliferation and tumor growth through Akt-related pathway

Overexpression of Id family proteins inhibits cell differentiation and enhances cell proliferation and invasiveness. Although Id1 is the Id family member mostly linked to tumorigenesis, its role in lung cancer is unclear. An elevated Id1 expression was observed in lung cancer cell lines as well as lung cancer tissues. Id1 overexpression increased cell proliferation while Id1 knockdown decreased cell proliferation, mostly through Akt-related pathway. Nude mice study further confirmed an increased tumor growth in Id1-overexpressing cells and a decreased tumor growth in Id1-knockdowned cells. In conclusion, inactivation of Id1 may provide a novel strategy for treatment of lung cancer patients.

Dysfunction of volume-sensitive chloride channels contributes to cisplatin resistance in human lung adenocarcinoma cells

Cisplatin-based chemotherapy is the standard therapy used to treat non-small-cell lung cancer. However, its efficacy is largely limited due to the development of drug resistance. The exact mechanism in which cancer cells develop resistance to the drug is not yet fully understood. The purpose of the present study is to test the role of volume-sensitive Cl(-) channels in cisplatin resistance in human lung adenocarcinoma cells (A549 cells) using patch-clamp recording, cell volume measurement and apoptosis assay. The results showed that cisplatin treatment induced an apoptotic volume decrease (AVD) and activated a Cl(-) current that showed properties similar to the volume-sensitive outward rectifying (VSOR) Cl(-) current in wild-type A549 cells. Both the AVD process and VSOR Cl(-) current were blocked by the chloride channel blocker 4,4'-diisothiocyanostilbene-2,2' disulfonic acid. However, the A549/CDDP cells, a model of acquired cisplatin resistance cells, on the other hand, had almost no AVD process and VSOR Cl(-) current when treated with cisplatin. Treatment of A549/CDDP cells with trichostatin A (TSA), a drug that inhibits histone deacetylases, partially restored the VSOR Cl(-) current and increased cisplatin-induced cell apoptosis rate. These results suggest that impaired activity of VSOR Cl(-) channels contributes to the cisplatin resistance in A549/CDDP cells.

Current status of methods to assess cancer drug resistance

Drug resistance is the main cause of the failure of chemotherapy of malignant tumors, resistance being either preexisting (intrinsic resistance) or induced by the drugs (acquired resistance). At present, resistance is usually diagnosed during treatment after a long period of drug administration.In the present paper, methods for a rapid assessment of drug resistance are described. Three main classes of test procedures can be found in the literature, i.e. fresh tumor cell culture tests, cancer biomarker tests and positron emission tomography (PET) tests. The methods are based on the evaluation of molecular processes, i.e. metabolic activities of cancer cells. Drug resistance can be diagnosed before treatment in-vitro with fresh tumor cell culture tests, and after a short time of treatment in-vivo with PET tests. Cancer biomarker tests, for which great potential has been predicted, are largely still in the development stage. Individual resistance surveillance with tests delivering rapid results signifies progress in cancer therapy management, by providing the possibility to avoid drug therapies that are ineffective and only harmful.

Navitoclax enhances the efficacy of taxanes in non-small cell lung cancer models

PURPOSE

To explore the potential of navitoclax in combination with taxane-based chemotherapy in the treatment of non-small cell lung cancer (NSCLC) by defining mechanism of synergy and identifying correlative biomarkers.

EXPERIMENTAL DESIGN

We treated a panel of NSCLC lines with a dose matrix of paclitaxel and navitoclax (formerly ABT-263), an inhibitor of Bcl-2, Bcl-x(L), and Bcl-w (1), and evaluated synergy. We next used time-lapse microscopy to explore mechanism of synergy. Finally, we developed an immunohistochemical assay and assessed prevalence of Bcl-x(L) in NSCLC tumor tissues.

RESULTS

All cell lines exhibit greater than additive response to the combination of navitoclax and a taxane. These results were extended to mouse xenograft tumor models, in which the combination is more efficacious than either single-agent docetaxel or navitoclax. Addition of navitoclax to paclitaxel decreases the time from mitotic entry to cell death and changes cell fate from mitotic slippage to death during mitotic arrest. The relative levels of Bcl-x(L) and Mcl-1 correlate with the extent of synergy, suggesting that cancers with elevated levels of Bcl-x(L) will be relatively resistant to taxane-based therapy but could benefit from the addition of navitoclax to taxane treatment. Finally, a significant percentage of NSCLC patient samples exhibit relatively high Bcl-x(L) levels.

CONCLUSIONS

The addition of navitoclax to taxane-based chemotherapy in NSCLC has the potential to increase efficacy, particularly in patients whose tumors express high levels of Bcl-x(L).

Cancer cells acquire mitotic drug resistance properties through beta I-tubulin mutations and alterations in the expression of beta-tubulin isotypes

BACKGROUND

Anti-mitotic compounds (microtubule de-stabilizers) such as vincristine and vinblastine have been shown clinically successful in treating various cancers. However, development of drug-resistance cells limits their efficacies in clinical situations. Therefore, experiments were performed to determine possible drug resistance mechanisms related to the application of anti-mitotic cancer therapy.

PRINCIPAL FINDINGS

A KB-derived microtubule de-stabilizer-resistant KB-L30 cancer cell line was generated for this study. KB-L30 cells showed cross-resistance to various microtubule de-stabilizers including BPR0L075, vincristine and colchicine through multiple-drug resistant (MDR)-independent mechanisms. Surprisingly, KB-L30 cells showed hyper-sensitivity to the microtubule-stabilizer, paclitaxel. Results of the RT-PCR analysis revealed that expression of both class II and III β-tubulin was down-regulated in KB-L30 cells as compared to its parental KB cancer cells. In addition, DNA sequencing analysis revealed six novel mutation sites present in exon four of the βI-tubulin gene. Computational modeling indicated that a direct relationship exists between βI-tubulin mutations and alteration in the microtubule assembly and dynamic instability in KB-L30 cells and this predicted model was supported by an increased microtubule assembly and reduced microtubule dynamic instability in KB-L30 cells, as shown by Western blot analysis.

CONCLUSIONS AND SIGNIFICANCE

Our study demonstrated that these novel mutations in exon four of the βI-tubulin induced resistance to microtubule de-stabilizers and hyper-sensitivity to microtubule stabilizer through an alteration in the microtubule assembly and dynamics in cancer cells. Importantly, the current study reveals that cancer cells may acquire drug resistance ability to anti-mitotic compounds through multiple changes in the microtubule networks. This study further provided molecular information in drug selection for patients with specific tubulin mutations.

Molecular circuits of solid tumors: prognostic and predictive tools for bedside use

The explosion of knowledge in cancer biology in the past two decades has led to the identification of specific molecular circuits in solid tumors. These pathways reflect specific abnormalities thought to drive malignant progression. This knowledge has also generated a vast panel of cancer biomarkers although many of these biomarkers lack sufficient research and validation to be used in the clinic. This Review discusses relevant molecular prognostic and/or predictive biomarkers in the six leading tumors with the highest contribution to cancer mortality: breast, lung, colorectal, prostate, pancreatic and ovarian cancer. Each biomarker is described according to its associated clinicopathological presentation and specific associated molecular interactions. Despite only few biomarkers being currently implemented in clinical practice, a new generation of predictors is emerging that could modify the classic organ-based cancer classification (for example, defects in DNA repair, aberrant MAPK signaling and aberrant PI3K/Akt/mTOR signaling). The advent of high-throughput strategies will also probably substitute monobiomarker strategies.