Inhibition of Notch and tumor regression

Abstract

e14623 Background: Notch signaling is an evolutionary-conserved pathway in vertebrates and invertebrates which is involved many developmental processes, including cell fate decisions, apoptosis, proliferation, and stem-cell self renewal. There is increasing evidence that the same molecular pathways regulating the self renewal of stem cells are also being employed in cancer progression. The Notch signal transduction pathway has been implicated in the self-renewal of stem cells in hematopoietic, skin, neural, germ and breast tissue. Increasing evidence suggests that the Notch signaling pathway is frequently up regulated in many forms of cancer including acute T-cell lymphoblastic leukemia, cervical, prostate, lung, breast and others. Thus,inhibition of the pathway could provide a novel treatment of cancer and cancer stem cells. Methods: We have genetically engineered a fusion protein, consisting of the Drosophila transcription factor Antennapedia (ANTP) and with the truncated version of Mastermind-like (MAML) that behaves in a dominant negative (DN) fashion and inhibits Notch activation (ANTP/DN MAML, TR4). This novel fusion protein has been tested for its ability to target tumor cells in vitro and in vivo. Results: Our data show that ANTP/DN MAML fusion protein, TR4 contains signals for proper cell targeting, internalization and nuclear transport. Furthermore, TR4 inhibits human mammary and colon xenograft tumor growth and metastases in immuno deficient mice.TR4 presence and activity was also detected in the brains of treated animals demonstrating that TR4 can cross the blood-brain barrier and potentially eliminate brain tumors and metastases, unlike other anticancer drugs and biological such as monoclonal antibodies that cannot cross the blood brain barrier. TR4 was found to be non- immunogenic following repeat administration in healthy animals. At very high doses (>10x therapeutic dose) it caused anorexia and weight loss in mice. Conclusions: The TR4 protein, a Notch inhibitor, can induce tumor regression and resolution of breast and colon cancer xenografts. It is non- immunogenic following repeat administration and has acceptable toxicity profile. No significant financial relationships to disclose.