Anti-TUBB3 monoclonal antibody, clone UVK-2 [Alexa Fluor® 488]

The transcription factor ZEB1 is normally not expressed in epithelial cells. When inappropriately expressed in carcinomas, ZEB1 initiates epithelial to mesenchymal transition due to its ability to repress E-cadherin and other genes involved in polarity. Recently, ZEB1 and ZEB2 have been identified as direct targets of the microRNA-200c family. We find that miR-200c levels are high in well-differentiated endometrial, breast, and ovarian cancer cell lines, but extremely low in poorly differentiated cancer cells. Low or absent miR-200c results in aberrant expression of ZEB1 and consequent repression of E-cadherin. Reinstatement of miR-200c to such cells restores E-cadherin and dramatically reduces migration and invasion. Microarray profiling reveals that in addition to ZEB1 and ZEB2, other mesenchymal genes (such as FN1, NTRK2, and QKI), which are also predicted direct targets of miR-200c, are indeed inhibited by addition of exogenous miR-200c. One such gene, class III beta-tubulin (TUBB3), which encodes a tubulin isotype normally found only in neuronal cells, is a direct target of miR-200c. This finding is of particular significance because we show that restoration of miR-200c increases sensitivity to microtubule-targeting agents by 85%. Because expression of TUBB3 is a common mechanism of resistance to microtubule-binding chemotherapeutic agents in many types of solid tumors, the ability of miR-200c to restore chemosensitivity to such agents may be explained by its ability to reduce TUBB3. Because miR-200c is crucial for maintenance of epithelial identity, behavior, and sensitivity to chemotherapy, we propose that it warrants further investigation as a therapeutic strategy for aggressive, drug-resistant cancers. [Mol Cancer Ther 2009;8(5): 1055-66]

Background: It has been proposed that the level of class III beta-tubulin gene expression can be used to predict clinical sensitivity to paclitaxel/vinorebine-based chemotherapy in non-small cell lung cancer (NSCLC) patients. However, whereas there are published reports supporting this association, there are also reports of studies that failed to find such an association. We conducted a meta-analysis of all relevant published data to provide a combined statistical assessment of the proposed association of expression variations of class III beta-tubulin with objective response and median survival in patients with NSCLC treated with paclitaxel/vinorebine-based chemotherapy. Methods: We conducted the meta-analysis using data from ten studies, each of which evaluated the correlation between class III beta-tubulin expression levels and objective response in patients treated with paclitaxel/vinorebine-based chemotherapy for NSCLC patients. All eligible studies were searched by MEDLINE, EMBASE and CNKI databases. Overall odds ratios (ORs) of the objective response were calculated using the method of Mantel-Haenszel. The differences in objective responses between Caucasian and Asian patients treated with paclitaxel/vinorebine-based chemotherapy were compared. We also compared outcomes for patients treated with paclitaxel to those treated with vinorebine. Results: There were a total of 552 patients in the ten studies that met our criteria for evaluation. High/positive expression of class III beta-tubulin was found in 279 patients (50.5%), and low/negative expression for this gene was found in 273 (49.5%) patients. The objective response rate for paclitaxel/vinorebine-based chemotherapy was significantly higher in patients with low/negative class III beta-tubulin expression (OR = 0.28; 95% CI, 0.20-0.41; P<0.00001). Median survival time was longer for patients with low/negative expression of class III beta-tubulin compared with patients with high/positive expression (MR = 1.40; CI, 0.89-0.90; P<0.00001). There was no significant difference in therapy between Caucasian and Asian patients treated with paclitaxel/vinorebine-based chemotherapy (Chi(2) = 0.02, P = 0.88). In our analysis, NSCLC patients treated with paclitaxel had more favorable clinical outcomes than those treated with vinorelbine (Chi(2) = 3.69, P = 0.05). Conclusions: By combining data from ten different studies, we found a correlation between low TUBB3 gene expression and favorable clinical outcome to anti-tubulin therapy. The correlation for the combined data was significantly stronger than it was for any of the individual studies. This result supports the usefulness of class III beta-tubulin mRNA level as a biomarker for sensitivity to paclitaxel/vinorebine-based chemotherapy in NSCLC patients. (C) Ltd 2012 Elsevier Ireland Ltd. All rights reserved.