Genomic Analysis Identifies Rare ALK Positive Cases In The TCGA Database

Abstract

Introduction/Objective The anaplastic lymphoma kinase (ALK) gene is a receptor tyrosine kinase gene located in the 2p23.2 region. Normally, dimerization of ALK receptor by binding to its ligand activates the ALK receptor by autophosphorylation of c-termius and activates downstream PI3K, MAPK and JAK3 pathways. The ALK gene is abnormally hyperactivated by fusion of the 3’ half containing the kinase domain with 5’ portion of other genes, resulting in the ligand independent dimerization and activation of the ALK receptor. The tumors harboring these translocations are termed as ALK-positive tumors and can be treated with ALK inhibitors. Methods We analyzed the status of clinically relevant ALK fusion driver mutations in 230 different cancer studies, containing tumors from 79222 different individuals, in The Cancer Genome Atlas database (TCGA) using the cbioportal web browser. Results We observed that, as expected ALK-positive mutations are predominantly present in NSCLC, with EML4- ALK being the most common. In addition, we were able to identify ALK positive mutations in colorectal carcinomas, papillary thyroid carcinomas, papillary renal cell carcinomas, sarcomas and invasive ductal carcinomas of the breast. Most important, our analysis identified extremely rare ALK positive cases in salivary duct carcinomas, urothelial carcinomas, cutaneous melanomas and prostatic adenocarcinomas. Conclusion Our analysis identified ALK positive cases were predominant in adenocarcinoma of lung with EML4-ALK being the most common ALK positive mutation, which is also consistent with the literature. However, the ALK positive mutations were at a lower prevalence rate than that described in the literature. We attribute the lower prevalence rate to underrepresentation of the Asian population in the TCGA database. In addition, we identified extremely rare ALK positive cases in salivary duct carcinomas, melanomas and prostate cancers, thus highlighting the need for testing for these mutations in these cancers.