TCGA的肿瘤突变负荷，你会算了吗？

不论你是做TCGA数据挖掘，还是自己的研究结果与TCGA数据库比较，都需要掌握一定的TCGA数据处理方法。当然，很多公众号都有TCGA数据挖掘的讲解，这里就不做赘述了。

什么是TMB?

如果你从事肿瘤相关研究，那么对Tumor mutation burden(TMB)一定不陌生，是指每Mb上产生的非同义突变的数目，产生的突变数目越多，意味着可能产生更多的新抗原，即越有可能被免疫系统识别，对免疫治疗敏感。TMB可以作为免疫治疗疗效的潜在指标，小编在文末整理了几篇经典的文献供大家学习。

如何计算TCGA全外显子突变数据的TMB？

计算TCGA数据(WES)的TMB，目前主要有两种方式：

1. 直接用非同义突变的数目来代表肿瘤的突变负荷。适用于同一批WES数据不同分组的TMB比较。

（Tips: 除了TCGA的全外显子数据外，任何全外显子数据都可以这样来计算TMB）

2. 非同义突变数目除以外显子芯片大小。TCGA全外显子芯片大小约38Mb。适用于不同研究间的TMB比较。

(Tips.非TCGA的WES数据，要根据实际芯片大小的情况作为分母，计算每Mb下产生了多少个非同义突变)

参考文献：

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