PTEN and neoplasm: In addition, alternative splicing of the precursor PTEN mRNA has also been reported, both under pathogenic and non-pathogenic conditions, and a PTEN isoform lacking the PTEN-C-terminal region encoded in exon 9 (PTEN-Δ, residues 1-343-Ser) has been proposed to play active roles in the context of tumor suppression [29–32].