# The Many Roads from Alternative Splicing to Cancer: Molecular Mechanisms Involving Driver Genes

## TL;DR

This review explains how alternative splicing can lead to cancer by creating harmful protein variants from driver genes, even without mutations.

## Contribution

The paper systematically categorizes 199 driver genes whose oncogenic potential arises from alternative splicing and details molecular mechanisms for over 40 genes.

## Key findings

- Aberrant alternative splicing can produce oncogenic variants from driver genes without requiring mutations.
- Thirty-one genes directly influence splicing and contribute to oncogenesis.
- Sixty-eight driver genes produce oncogenic isoforms through alternative splicing.

## Abstract

Alternative splicing is a mechanism that allows, through the combination of different exons, for the yielding of several protein variants from a single gene. These variants may display different and often opposed functions. Mutations occurring in driver genes result in oncogenesis, but alternative splicing may also result in obtaining oncogenic variants in the absence of driver mutations. This review describes how the oncogenic potential of driver genes is activated through aberrant alternative splicing. Firstly, there are driver genes directly acting on alternative splicing and their dysregulation affects the splicing of other genes involved in malignant transformation. A second possibility is that aberrant alternative splicing of a proto-oncogene or tumour suppressor gene results in the appearance of an oncogenic variant. The oncogenic potential of a total of 199 driver genes may result from aberrant alternative splicing, and the molecular mechanisms involved are detailed for more than 40 genes.

Cancer driver genes are either oncogenes or tumour suppressor genes that are classically activated or inactivated, respectively, by driver mutations. Alternative splicing—which produces various mature mRNAs and, eventually, protein variants from a single gene—may also result in driving neoplastic transformation because of the different and often opposed functions of the variants of driver genes. The present review analyses the different alternative splicing events that result in driving neoplastic transformation, with an emphasis on their molecular mechanisms. To do this, we collected a list of 568 gene drivers of cancer and revised the literature to select those involved in the alternative splicing of other genes as well as those in which its pre-mRNA is subject to alternative splicing, with the result, in both cases, of producing an oncogenic isoform. Thirty-one genes fall into the first category, which includes splicing factors and components of the spliceosome and splicing regulators. In the second category, namely that comprising driver genes in which alternative splicing produces the oncogenic isoform, 168 genes were found. Then, we grouped them according to the molecular mechanisms responsible for alternative splicing yielding oncogenic isoforms, namely, mutations in cis splicing-determining elements, other causes involving non-mutated cis elements, changes in splicing factors, and epigenetic and chromatin-related changes. The data given in the present review substantiate the idea that aberrant splicing may regulate the activation of proto-oncogenes or inactivation of tumour suppressor genes and details on the mechanisms involved are given for more than 40 driver genes.