The gene TRK was shown to cause a small percentage of colon cancers in 1982 and then in 2013 and 2014, sequencing of tumor samples found fusions of the TRK family of genes in at least 11 tumor types, including lung, breast and melanoma .
The TRK family of genes, including NTRK1, NTRK2 and NTRK3 are important in the developing nervous system. In the womb, these genes and the proteins they encode are essential for the growth and survival of new neurons. After birth, these genes are unneeded in many tissues and so are programmed to go dormant.
Some cancers wake them up - when improperly fused with other nearby genes, genes in the TRK family can restart their ability to signal cells to grow and become immortal, which in adult tissues can cause cancer.