A label-free mass spectrometry method for relative quantitation of β-tubulin isotype expression in human tumor tissue
Correspondence: Dr. Ruth Hogue Angeletti, Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx NY 10461, USA
Quantitation of β-tubulin isotype expression in taxane resistant human tumor tissue has been difficult to achieve because of the limited availability of validated antibodies. Here we present a label-free MS method to quantitate relative expression levels of β-tubulin isotypes.
Using isotype-specific reporter peptides, we determined relative β-tubulin isotype expression levels in human lung tumor tissue.
Four reporter peptides were chosen to quantitate the βI/βII, βIV, βIII, and βV tubulin isotypes. These peptides were validated using human cancer cell lines. The label-free method was then used to determine β-tubulin isotype expression in nine human lung tumor samples, which had been described as high or low βIII-tubulin expressing using immunohistochemistry. It was found that βI/βII (accounting for 18.7–65.7% of total β-tubulin) and βIVa/βIVb (26.3–79.1%) were the most abundant isotypes and that the βIII (0–8.9%) and βV (1.0–10.4%) were less abundant in the tissue. We also categorized the samples as high or low βIII-tubulin expressing.
Conclusion and clinical relevance
With this method we can determine the relative expression levels of β-tubulin isotypes in human tumor tissue. This method will facilitate studies assessing the use of tubulin isotypes as biomarkers of taxane resistance.