Targeted sequencing of cancer‐related genes in nasopharyngeal carcinoma identifies mutations in the TGF‐β pathway

Approximately, 25% of nasopharyngeal carcinoma (NPC) patients develop recurrent disease. NPC may involve relatively few genomic alterations compared to other cancers due to its association with Epstein‐Barr virus (EBV). We envisioned that in‐depth sequencing of tumor tissues might provide new insights into the genetic alterations of this cancer. Thirty‐three NPC paired tumor/adjacent normal or peripheral blood mononuclear cell samples were deep‐sequenced (>1000×) with respect to a panel of 409 cancer‐related genes. Newly identified mutations and its correlation with clinical outcomes were evaluated. Profiling of somatic mutations and copy number variations (CNV) in NPC tumors identified alterations in RTK/RAS/PI3K, NOTCH, DNA repair, chromatin remodeling, cell cycle, NF‐κB, and TGF‐β pathways. In addition, patients harbored CNV among 409 cancer‐related genes and missense mutations in TGF‐β/SMAD signaling were associated with poor overall survival and poor recurrence‐free survival, respectively. The CNV events were correlated with plasma EBV copies, while mutations in TGFBR2 and SMAD4 abrogate SMAD‐dependent TGF‐β signaling. Functional analysis revealed that the new TGFBR2 kinase domain mutants were incapable of transducing the signal, leading to failure of phosphorylation of SMAD2/3 and activation of downstream TGF‐β‐mediated cell growth arrest. This study provides evidence supporting CNV and dysregulated TGF‐β signaling contributes to exacerbating the NPC pathogenesis.