PIWIL2 and neoplasm: While exploring the mechanism underlying Piwil2-mediated tumor development, we found by GEM RT-PCR that the “Piwil2” transcripts expressed in the murine pCSCs were truncated at 5′-end and absent of first 6 exons of Piwil2. Through bioinformatics analysis of human and mouse PIWIL2 gene, we found several potential 5′-end truncated variants of PIWIL2, called Piwil2-like (PL2L) genes.