Department of Oncogene Regulation, Chittaranjan National Cancer Institute, Kolkata, India.
Department of Life Science, Presidency University, Kolkata, India.
Mutagenesis. 2020 Dec 31;35(6):499-508. doi: 10.1093/mutage/geaa031.
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.
膀胱尿路上皮癌（BlCa）中 PIK3CA 的激活及其在 9 号和 20 号外显子的反复突变已得到充分报道。但是，砷对该通路激活的影响尚未得到充分阐明。因此，我们旨在分析砷对原发性 BlCa 样本中 PIK3CA 的遗传（拷贝数变异/突变）和表达谱的影响。观察到 PIK3CA 基因座的扩增频率较低（16%），在高砷（AsH）样本中高于低砷（AsL）样本。在 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，其中以 C>T 转换突变为主（47%）。外显子 9 和 20 分别携带 48%和 73%的总突变，其中 E542K/E545K 突变占 37%，H1047Y/R 突变占 25%。虽然在 AsH 和 AsL 中观察到突变频率相当，但我们观察到一些砷特异性突变，包括 c.1633G>A、c.1634A>C（E545K）和 c.2985C>T 和 c.3130G>T 突变，以及 AsH 组中常见的 A>C 和 G>T 横向突变。此外，73%的 BlCa 样本显示 PIK3CA 的过度表达（mRNA/蛋白）与遗传改变（扩增/突变）有关，在 AsH 组中显著升高（P=0.01）。然而，36%的样本显示 PIK3CA 过度表达，与突变或扩增无关，表明 PIK3CA 基因的转录上调。因此，评估了转录因子 NFκB 的表达状态，并发现其与 AsH 组中 PIK3CA 的过度表达（mRNA/蛋白）显著相关。同样，pAKT1（Thr 308）的表达模式也与 PIK3CA 过度表达显著相关。最后，PIK3CA 或 NFκB 过度表达的 AsH 患者总生存最差，表明砷对该通路和患者预后有重要影响。因此，我们的研究表明，砷相关的 PIK3CA/AKT1/NFkB 在 BlCa 中的差异分子谱在疾病的分子发病机制中起重要作用。
