PTEN and neoplasm: In addition, PTEN plays PIP3-independent tumor suppressor roles in the cytoplasm and in the nucleus, and the dynamic partitioning of PTEN between membranes, cytoplasm, and nucleus, is crucial in modulating PTEN physiologic activity.19–22 The PTEN gene behaves as a haploinsufficient gene, and partial loss of expression or activity of PTEN protein confers tumor growth advantages.