Abstract

The activation of PIK3CA in bladder carcinoma (BlCa) with its recurrent mutations in exon 9 and 20 were well reported. But the association of arsenic on the activation of the pathway is not well elucidated. Therefore, we aimed to analyse the effect of arsenic on the genetic (copy number variation/mutation) and expression profiles of PIK3CA in primary BlCa samples. Infrequent amplification (16%) of the PIK3CA locus was observed, with higher frequency among the arsenic-high (AsH) than arsenic-low (AsL) samples. Frequent (54%) tumour-specific mutations in exon 9 and 20 of PIK3CA were observed in the BlCa samples with prevalent (47%) C>T transition mutations. Exon 9 and 20 harboured 48% and 73% of the total mutations, respectively, with 37% in E542K/E545K and 25% of the mutation in H1047Y/R. Though mutation frequency in AsH and AsL was found to be comparable, we observed some arsenic-specific mutation at c.1633G>A, c.1634A>C (E545K) and c.2985C>T and c.3130G>T mutations, as well as prevalent transverse mutations of A>C and G>T in AsH group. Furthermore, 73% of the BlCa samples showed overexpression (mRNA/protein) of PIK3CA with genetic alterations (amplification/mutation), significantly (P = 0.01) higher in AsH group. However, 36% of the samples showed overexpressed PIK3CA, independent of mutation or amplification, signifying a transcriptional upregulation of PIK3CA gene. Therefore, the expression status of NFκB, a transcription factor of PIK3CA, was assessed and found to be significantly correlated with the overexpression of PIK3CA (mRNA/protein) in AsH group. Similarly, the expression pattern of pAKT1 (Thr 308) was also found to be significantly correlated with PIK3CA overexpression. Finally, AsH patients with the overexpression of PIK3CA or NFκB had the worst overall survival, signifying a strong impact of arsenic on this pathway and outcome of the patients. Thus, our study showed that the arsenic-associated differential molecular profile of PIK3CA/AKT1/NFkB in BlCa has an important role in the molecular pathogenesis of the disease.

中文翻译：

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砷相关膀胱癌中 PIK3CA 基因的不同分子谱

 抽象的

膀胱癌 (BlCa) 中PIK3CA的激活及其外显子 9 和 20 的反复突变已得到充分报道。但砷与该途径激活的关系尚未得到很好的阐明。因此，我们旨在分析砷对原代 BlCa 样品中PIK3CA的遗传（拷贝数变异/突变）和表达谱的影响。观察到PIK3CA基因座的扩增频率不高 (16%)，高砷 (AsH) 样品中的扩增频率高于低砷 (AsL) 样品。在具有普遍 (47%) C>T 过渡突变的 BlCa 样本中观察到PIK3CA外显子 9 和 20 中频繁 (54%) 的肿瘤特异性突变。外显子 9 和 20 分别占总突变的 48% 和 73%，其中 E542K/E545K 占 37%，H1047Y/R 占 25%。虽然 AsH 和 AsL 的突变频率具有可比性，但我们在 c.1633G>A、c.1634A>C (E545K) 以及 c.2985C>T 和 c.3130G>T 突变中观察到一些砷特异性突变，如AsH组中普遍存在A>C和G>T横向突变。此外，73% 的 BlCa 样本显示 PIK3CA 过度表达（mRNA/蛋白质），并伴有遗传改变（扩增/突变），AsH 组显着较高（ P = 0.01）。然而，36% 的样本显示 PIK3CA 过度表达，与突变或扩增无关，这表明PIK3CA基因转录上调。因此，对AsH组中PIK3CA转录因子NFκB的表达状态进行评估，发现其与PIK3CA（mRNA/蛋白）的过表达显着相关。 同样，pAKT1（Thr 308）的表达模式也被发现与 PIK3CA 过表达显着相关。最后，PIK3CA 或 NFκB 过度表达的 AsH 患者的总生存期最差，这表明砷对该途径和患者的预后有强烈影响。因此，我们的研究表明，BlCa 中与砷相关的 PIK3CA/AKT1/NFkB 差异分子谱在该疾病的分子发病机制中具有重要作用。