A novel oncogenic BTK isoform is overexpressed in colon cancers and required for RAS-mediated transformation

Oncogene. 2016 Aug 18;35(33):4368-78. doi: 10.1038/onc.2015.504. Epub 2016 Jan 25.


Bruton's tyrosine kinase (BTK) is essential for B-cell proliferation/differentiation and it is generally believed that its expression and function are limited to bone marrow-derived cells. Here, we report the identification and characterization of p65BTK, a novel isoform abundantly expressed in colon carcinoma cell lines and tumour tissue samples. p65BTK protein is expressed, through heterogeneous nuclear ribonucleoprotein K (hnRNPK)-dependent and internal ribosome entry site-driven translation, from a transcript containing an alternative first exon in the 5'-untranslated region, and is post-transcriptionally regulated, via hnRNPK, by the mitogen-activated protein kinase (MAPK) pathway. p65BTK is endowed with strong transforming activity that depends on active signal-regulated protein kinases-1/2 (ERK1/2) and its inhibition abolishes RAS transforming activity. Accordingly, p65BTK overexpression in colon cancer tissues correlates with ERK1/2 activation. Moreover, p65BTK inhibition affects growth and survival of colon cancer cells. Our data reveal that BTK, via p65BTK expression, is a novel and powerful oncogene acting downstream of the RAS/MAPK pathway and suggest that its targeting may be a promising therapeutic approach.

MeSH terms

  • 5' Untranslated Regions / physiology
  • Agammaglobulinaemia Tyrosine Kinase
  • Cell Line, Tumor
  • Cell Transformation, Neoplastic*
  • Colonic Neoplasms / enzymology
  • Colonic Neoplasms / pathology*
  • Heterogeneous-Nuclear Ribonucleoprotein K / physiology
  • Humans
  • MAP Kinase Signaling System / physiology
  • Protein Isoforms / genetics
  • Protein Isoforms / physiology
  • Protein-Tyrosine Kinases / analysis
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / physiology*
  • ras Proteins / physiology*


  • 5' Untranslated Regions
  • Heterogeneous-Nuclear Ribonucleoprotein K
  • Protein Isoforms
  • HNRNPK protein, human
  • Protein-Tyrosine Kinases
  • Agammaglobulinaemia Tyrosine Kinase
  • BTK protein, human
  • ras Proteins