Abstract

BACKGROUND:

Morphologically normal tissue, adjacent to tumors, contains multiple molecular changes, the so-called field cancerization. The multifocal and recurrent nature of bladder cancer has been hypothesized to originate from this. However, further studies are required to explore the mutational composition of normal tissue adjacent to tumors.

OBJECTIVE:

To analyze field cancerization in bladder cancer patients using a non-tumor guided approach.

METHODS:

We investigated the mutational landscape of normal appearing urothelium and paired bladder tumors from four patients by applying deep-targeted sequencing.

RESULTS:

Sequencing of 509 cancer driver genes revealed the presence of 2– 13 mutations exclusively localized in normal tissue (average target read depth 634×). Furthermore, 6– 13 mutations were shared between tumor and normal samples and 8– 75 mutations were exclusively detected in tumor samples. More mutations were observed in normal samples from patients with multifocal disease compared to patients with unifocal disease. Mutations in normal samples had lower variant allele fractions (VAF) compared to tumor mutations (p < 2.2*10^–16). Furthermore, significant differences in the type of nucleotide changes between tumor, normal and shared mutations (p = 2.2*10^–5) were observed, and mutations in APOBEC context were observed primarily among tumor mutations (p = 0.02). No differences in functional impact between normal, shared and tumor mutations were observed (p = 0.61).

CONCLUSION:

Overall, these findings support the presence of more than one field in the bladder, and document non-tumor specific driver mutations to be present in normal appearing bladder tissue.

中文翻译：

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膀胱癌中野癌的突变分析

摘要

背景：

与肿瘤相邻的形态正常的组织包含多个分子变化，即所谓的野癌。据推测，膀胱癌的多灶性和复发性源于此。然而，需要进一步的研究来探索邻近肿瘤的正常组织的突变组成。

目的：

使用非肿瘤指导方法分析膀胱癌患者的野外癌变。

方法：

我们通过应用深度靶向测序研究了来自四名患者的正常出现的尿路上皮和成对的膀胱肿瘤的突变情况。

结果：

对509个癌症驱动基因的测序表明，仅在正常组织中存在2–13个突变（平均目标阅读深度634倍）。此外，在肿瘤和正常样品之间共有6–13个突变，仅在肿瘤样品中检测到8–75个突变。与患有单灶疾病的患者相比，在多灶疾病患者的正常样本中观察到更多的突变。与肿瘤突变相比，正常样品中的突变具有较低的变异等位基因分数（VAF）（p  <2.2 * 10 ^–16）。此外，肿瘤突变，正常突变和共有突变之间核苷酸变化类型的显着差异（p  = 2.2 * 10 ^–5），并且主要在肿瘤突变中观察到APOBEC背景下的突变（p  = 0.02）。在正常，共有和肿瘤突变之间没有观察到功能影响的差异（p  = 0.61）。

结论：

总的来说，这些发现支持膀胱中存在多个视野，并证明在正常出现的膀胱组织中存在非肿瘤特异性驱动基因突变。