Resistance to the Tubulin-Binding Agents in Renal Cell Carcinoma: No Mutations in the Class I β-Tubulin Gene but Changes in Tubulin Isotype Protein Expression

Abstract

Purpose:The primary purpose of this study was to determine whether mutations of the class I b-tubulin gene may be implicated in the inherent resistance to tubulin-binding agents (TBA) in renal cancer, with a small number of samples and cell lines also being examined for class I and III h-tubulin isotype protein expression. Experimental Design: DNA was extracted from 90 renal tumors and the class I b-tubulin gene analyzed for mutations. For each sample, eight PCRs were used to cover the complete coding sequence with intronic primers ensuring highly homologous pseudogenes were not coamplified. Additionally, expression levels of class I and III h-tubulin isotypes in 17 matched normal and malignant renal samples and a panel of renal cell carcinoma cell lines with differing intrinsic resistance to theTBAs was examined by Western blotting. Results: Four polymorphic sequence changes of the class I b-tubulin gene were identified with no mutations. Class I protein expression levels were higher in tumor tissue versus normal tissue, whereas class III expression showed no consistent change. In renal cancer cell lines, a significant correlation between class III isotype expression and vinblastine sensitivity was observed. Conclusions:These results do not support a role for mutations in the class I b-tubulin gene in the intrinsic resistance of renal cancer toTBAs. Class III isotype expression may be implicated in resistance in vitro but in vivo, changes in class I isotype expression in renal cell carcinoma tissue may support a role in resistance to theTBAs and warrants further investigation.

Ixabepilone: targeting βIII-tubulin expression in taxane-resistant malignancies

“…There was an increase in the expression of the hI-tubulin isotype in patients with renal cell cancer, but no specific mutations were found. In cell lines, there was no correlation between expression of hI-tubulin and drug sensitivity, but a significant correlation between class III h-tubulin expression and vinblastine sensitivity was observed (40). Investigation of hIII-tubulin expression as it relates to prognosis in patients with renal cell carcinoma is warranted.…”

“…An association between hIII-tubulin overexpression and worse prognosis has been reported in several human tumors, including advanced malignancies that are routinely treated with taxanes [e.g., breast cancer (38), lung cancer (9), and ovarian cancer (10,39)] and malignancies that inherently respond poorly to taxanes [e.g., renal cell carcinoma (40)]. …”

“…The presence of mutations in the hI-tubulin and the distribution of hI and hIII isotypes were studied in patients with renal cell cancer and healthy subjects (40). There was an increase in the expression of the hI-tubulin isotype in patients with renal cell cancer, but no specific mutations were found.…”

Understanding microtubule dynamics for improved cancer therapy

“…Some tubulin isotypes, such as class III b tubulin, were found to be overexpressed in tumors [28,29]. This isotypic selection of tubulin in tumors may have important consequences for MT dynamics regulation and for the sensitivity or resistance to MTDs [29][30][31][32][33][34].…”

Microtubules Regulate Hypoxia-inducible Factor-1α Protein Trafficking and Activity

“…However, no correlation between P-glycoprotein expression and response to MTDs has been found in renal cancer cell lines (40). Another possible mechanism of resistance is the presence of ␤-tubulin mutations in the respective MTD drug binding sites; however, to date, no ␤-tubulin mutations have been identified in renal tumors (41). Interestingly, overexpression of the neuronal-specific ␤III tubulin isotype, which contains HREs and is driven by HIF-1␣ (42), has been clinically correlated with taxane resistance in several epithelial tumor types (43).…”