DDIS-16. A MOLECULAR IMAGING BIOSENSOR MONITORS THE EFFECTS OF ANTI-MISFOLDING DRUGS THAT RESTORE MUTANT p53 FUNCTION AND ENHANCE COMBINATION CHEMOTHERAPY FOR GLIOBLASTOMA

Abstract

BACKGROUND

Small molecule drugs that induce refolding of mutant p53 conformations may restore tumor suppressor function in glioblastoma. We developed a molecular imaging biosensor to monitor drug modulated changes in p53 folding in cells and in vivo. We evaluated the role of drugs that bind to mutant p53 proteins in different glioblastoma cells engineered to stably express four different genetic backgrounds (wt-p53 or three other mutant p53s).

METHODS

We developed separate Ln229 cells (endogenously mt-p53^P98L) to each stably express one of four varieties of a split-Renilla luciferase reporter protein complementation biosensor (NRLuc-p53-CRLuc), to thus achieve four different cellular p53 statuses (wt-p53, mt-p53^Y220C, mt-p53^G245S and mt-p53^G282W). We first studied if these transduced fusion proteins could induce changes in background p53 status. We then tested these cells for luciferase complementation after exposure to anti-misfolding drugs (PhiKan083 and SCH-529074, with high affinity for p53^Y220C and p53^G245S, respectively). Further, we studied the apoptotic effects of these drugs when combined with chemotherapies in all transduced Ln229 and U-87MG cells (the latter endogenously wt-p53 status).

RESULTS

Ln229 cells adopted p53 phenotypes that reflected the transduced biosensor fusion proteins. There was activation of p53 structural change upon PhiKan083 and SCH-529074 treatments. Cells treated with PhiKan083 showed significant levels of p53 refolding for mt-p53^Y220C. Cells treated with doxorubicin (Dox) or temozolomide (TMZ) in combination with PhiKan083 (12.5–50μM) or SCH (1.25–5.0μM) showed significant dose dependent enhancement of apoptotic effect (>40% increase) within 24h after treatment.

CONCLUSION

A p53 protein folding biosensor maintains its particular p53 function within cells, and induces a change in their p53 genetic background. The use of PhiKan083 and SCH-529074 improves the therapeutic effects of Dox and TMZ in glioblastoma cells. Applications of this biosensor will be useful for discovery and screening of new p53 anti-misfolding drugs and subsequent validation of hits in small animal models.