title: Sustained regression of tumors upon MYC inactivation requires p53 or thrombospondin-1 to reverse the angiogenic switch.
abstract: The targeted inactivation of oncogenes offers a rational therapeutic approach for the treatment of cancer. However, the therapeutic inactivation of a single oncogene has been associated with tumor recurrence. Therefore, it is necessary to develop strategies to override mechanisms of tumor escape from oncogene dependence. We report here that the targeted inactivation of MYC is sufficient to induce sustained regression of hematopoietic tumors in transgenic mice, except in tumors that had lost p53 function. p53 negative tumors were unable to be completely eliminated, as demonstrated by the kinetics of tumor cell elimination revealed by bioluminescence imaging. Histological examination revealed that upon MYC inactivation, the loss of p53 led to a deficiency in thrombospondin-1 (TSP-1) expression, a potent antiangiogenic protein, and the subsequent inability to shut off angiogenesis. Restoration of p53 expression in these tumors re-established TSP-1 expression. This permitted the suppression of angiogenesis and subsequent sustained tumor regression upon MYC inactivation. Similarly, the restoration of TSP-1 alone in p53 negative tumors resulted in the shut down of angiogenesis and led to sustained tumor regression upon MYC inactivation. Hence, the complete regression of tumor mass driven by inactivation of the MYC oncogene requires the p53-dependent induction of TSP-1 and the shut down of angiogenesis. Notably, overexpression of TSP-1 alone did not influence tumor growth. Therefore, the combined inactivation of oncogenes and angiogenesis may be a more clinically effective treatment of cancer. We conclude that angiogenesis is an essential component of oncogene addiction.
authors.affiliation: Departments of Medicine and Pathology, Division of Oncology, Stanford University School of Medicine, CCSR Building, Room 1120, 269 Campus Drive, Stanford, CA 94305-5151, USA.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Giuriato
authors.forename: Sandra
authors.initials: S
authors.lastname: Ryeom
authors.forename: Alice C
authors.initials: AC
authors.lastname: Fan
authors.forename: Pavan
authors.initials: P
authors.lastname: Bachireddy
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Lynch
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Rioth
authors.forename: Jan
authors.initials: J
authors.lastname: van Riggelen
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Kopelman
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Passegué
authors.forename: Flora
authors.initials: F
authors.lastname: Tang
authors.forename: Judah
authors.initials: J
authors.lastname: Folkman
authors.forename: Dean W
authors.initials: DW
authors.lastname: Felsher
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D051379:Mice; D009369:Neoplasms / Q000098:blood supply / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D019700:Thrombospondin 1 / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D019700:Thrombospondin 1; D016159:Tumor Suppressor Protein p53