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New insights in beta-tubulin sequence analysis in non-small cell lung cancer
J de Castro1, C Belda-Iniesta, P Cejas
1Department of Medical Oncology, La Paz University Hospital, Paseo de la Castellana 261, Madrid 28046, Spain.
Abstract:
Scarce data are available regarding the molecular mechanisms implicated in paclitaxel resistance. There is controversial data about beta-tubulin mutations role in paclitaxel resistance. We have conducted this trial to address the influence of beta-tubulin mutations in paclitaxel resistance in advanced non-small cell lung cancer (NSCLC). A group of 15 patients were biopsied and diagnosed of stages IIIB and IV NSCLC. Tumor specimens were used for DNA isolation and exon 4 of HM40 beta-tubulin isotype was amplified and automatically sequenced, using both intronic and exonic primers. Next, the chemotherapy schedule consisted of weekly paclitaxel (100 or 150 mg/m(2) x 6) followed 2 weeks later by cisplatin 100 mg/m(2) on day 1, gemcitabine 1000 mg/m(2) on days 1 and 14, and vinorelbine 25 mg/m(2) on days 1 and 14, every 28 days. Using exonic primers, gene sequence alterations were found in 13/15 (87%) patients, including transitions (codons 180 and 182) and one silent transversion (codon 195). Also, three transversions (codons 231, 234, and 235) were found in all patients and controls. All alterations disappeared when sequenced with intronic primers. Our results suggest that point mutations demonstrated with exonic primers but not with intronic ones are probably due to beta-tubulin pseudogenes present in advanced NSCLC specimens. Even so, when these beta-tubulin pseudogenes are found there is a clear relation with clinical response. Although these changes could be relevant in paclitaxel resistance, this observation must be proven in future clinical trials to resolve "the tubulin dilemma".
Insights
Beta-tubulin mutations in advanced non-small cell lung cancer (NSCLC) specimens may be linked to paclitaxel resistance. These alterations, potentially from pseudogenes, correlate with clinical response, warranting further investigation.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Paclitaxel resistance mechanisms in non-small cell lung cancer (NSCLC) are not fully understood.
- The role of beta-tubulin mutations in paclitaxel resistance remains controversial.
- Advanced NSCLC presents significant challenges in treatment efficacy.
Purpose of the Study:
- To investigate the influence of beta-tubulin mutations on paclitaxel resistance in advanced NSCLC.
- To analyze beta-tubulin gene alterations in NSCLC patient tumor specimens.
- To correlate genetic findings with clinical response to paclitaxel-based chemotherapy.
Main Methods:
- DNA was isolated from tumor specimens of 15 advanced NSCLC patients (Stages IIIB and IV).
- Exon 4 of the beta-tubulin isotype gene was amplified and sequenced using intronic and exonic primers.
- Patients received a chemotherapy regimen including paclitaxel, cisplatin, gemcitabine, and vinorelbine.
Main Results:
- Sequence alterations were detected in 87% (13/15) of patients using exonic primers, including transitions and transversions.
- All detected alterations disappeared when sequencing was performed with intronic primers.
- The presence of beta-tubulin pseudogenes was suggested, correlating with clinical response.
Conclusions:
- Point mutations detected by exonic primers in NSCLC are likely due to beta-tubulin pseudogenes.
- The presence of these pseudogenes shows a clear relation with clinical response.
- Further clinical trials are necessary to confirm the role of these beta-tubulin alterations in paclitaxel resistance.