TERF1 and breast cancer: Lee et al. have reported that one tRF-1, namely, tRF-1001, derived from pre-tRNASer, is highly expressed in several cancer cell lines and is required for proliferation of prostate cancer cells [10]; another tRF, the tRF-3Thr, has been demonstrated to be significantly downregulated in primary breast cancer and metastatic tumors, and overexpression of tRF-3Thr in breast cancer cells remarkably inhibited cell invasiveness and migration [11].