Increased protein expression of the PTEN tumor suppressor in the presence of constitutively active Notch-1.

Mammalian Notch-1 is part of an evolutionarily conserved family of transmembrane receptors best known for involvement in cell fate decisions. Mutations that result in Notch-1 activation result in T-lineage oncogenesis. In other cell lineages, however, studies have indicated that cooperation with cellular signaling pathways, such as Ras, is necessary for Notch-mediated oncogenesis and in some settings, Notch-1 has been reported to function as a tumor suppressor.

Activated EGFR promotes the survival of B-lineage acute leukemia in the absence of stromal cells.

B-lineage acute leukemia (B-ALL) cells often require stromal cell support for optimal proliferation and apoptotic resistance. In addition, stromal cell contact can promote resistance to chemotherapeutic agents. However, the precise biochemical pathways within the leukemic cell that are activated by the bone marrow microenvironment which result promotion of cell proliferation and apoptotic protection are not fully characterized.