Lack of β‐tubulin gene mutations in early stage lung cancer

Abstract

Objective Fibroblasts from patients with systemic sclerosis (SSc) have an activated phenotype characterized by increased synthesis of extracellular matrix (ECM) components. SPARC (secreted protein, acidic and rich in cysteine) regulates the deposition or assembly of ECM components. The aim of this study was to investigate the role of SPARC in SSc susceptibility by functional and genetic association studies. Methods Complementary DNA (cDNA) microarrays were used to obtain gene expression data on cultured dermal fibroblasts from SSc patients. SPARC protein levels were assessed by Western blotting. Five polymorphic microsatellite markers within 5 cM of the SPARC gene (chromosome 5q31‐32) were genotyped in Choctaw Indians, a population previously shown to have a high prevalence of SSc. Discovery of single‐nucleotide polymorphisms (SNPs) was accomplished by sequencing the SPARC cDNA. These SNPs were then genotyped in a multi‐ethnic cohort of SSc patients to determine potential associations with disease susceptibility in a broader population of SSc patients, as well as with various clinical and immunologic features of SSc. The functional relevance of these SNPs with regard to transcript stability of SPARC was also assessed. Results Microarrays demonstrated increased expression of SPARC, along with other ECM genes, in SSc patients compared with normal controls. SSc fibroblasts also had increased SPARC protein levels. Three of 5 microsatellite markers near SPARC showed significant associations with SSc in the Choctaw SSc patients. Sequencing of SPARC cDNA revealed 3 novel SNPs in the 3′‐untranslated region at +998 (C→G), +1551 (C→G), and +1922 (T→G). Homozygosity for the C allele at SNP +998 was significantly increased in SSc patients across ethnic lines. SPARC SNPs +1551 and +1922 demonstrated correlations with Raynaud's phenomenon and pulmonary fibrosis, respectively. Functional studies of SPARC SNP +998 in normal fibroblast cultures suggested a correlation between the SNP +998 C allele polymorphism and an increased messenger RNA half‐life. Conclusion This study is the first to show that polymorphisms of the SPARC gene are associated with susceptibility to, and clinical manifestations of, SSc and that they may also be functionally important in influencing SPARC expression in skin fibroblasts.

Looking at Drug Resistance Mechanisms for Microtubule Interacting Drugs: Does TUBB3 Work?

“…In 1999, -tubulin mutations were observed in serum DNA from one-third of non-small-cell lung cancer patients, those exhibiting the worst outcome [31]. However, this first report was not confirmed in later studies, either in lung [32][33][34] or other tumors [34][35][36][37]. Where was the problem?…”

Mechanisms of Taxol resistance related to microtubules

“…Moreover, this report suggested a relationship between the location of the mutations on b-tubulin and response to Taxol-based chemotherapy, since patients with and without mutations had dramatic differences in median survival, a finding, which if validated, would have profound implications in determining treatment options for patients with NCSLC. Several groups sought to confirm this initial study; however, the results have not been corroborated in these prospective studies (Kelley et al, 2001;Kohonen-Corish et al, 2002;Sale et al, 2002;Tsurutani et al, 2002), although silent polymorphisms have been reported. A recent study analysing 62 human breast cancer tumors also concluded a lack of b-tubulin mutations in these tumors, and documented the presence of a silent polymorphism at codon 217 (Hasegawa et al, 2002).…”

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

“…Single nucleotide polymorphisms in the 3V untranslated region have also been described previously (refs. 22, 23;dbSNP:1054419 The vast majority of previous mutation analyses have employed J00314 as a reference, which differs from the recently published wild-type sequence (cDNA AF070600, genomic DNA AP00512) by eight nucleotides (22,36). Such findings are particularly important in a mutational analysis of h-tubulin, as mismatches between these reference genes have been reported as somatic mutations (21).…”