PTEN and central nervous system cancer: For instance, the lncRNA LINC00961-encoded peptide, SPAR, is highly conserved in both human and mouse, and SPAR inhibits amino acid-mediated mTORC1 activation through the interaction with v-ATPase on the lysosomal membrane.62 Additionally, a small open reading frame at the 5’ end of the MYC gene mRNA encodes a secreted peptide, MPEP, composed of 114 amino acids that promotes glioma stem cell proliferation and tumor growth.63 The tumor suppressor protein PTEN has multiple isoforms translated from CUG or AUU start codons, including PTENα, β, and ε.