MTDH and breast cancer: At the same time, the mouse homolog was cloned as MTDH as a cell membrane protein mediating breast cancer metastasis to the lungs using an in vivo phage screening approach [4], and gene trapping technique facilitated cloning of mouse/rat homologue as 3d3/lyric as an endoplasmic reticulum (ER)/nuclear envelop protein and as a tight junction protein [5,6].