NSC59984 (NSC) is a compound in the National Cancer Institute chemical diversity library that has recently been shown in colorectal cancer to restore p53 wild-type function by activating p73 and simultaneously degrades mutant p53. All of these drugs have potentially valuable effects, however, NSC and Prima1 reactivate wild-type p53 and inhibit mutant p53 which would potentially restore the advantageous aspects of p53 while preventing its gain-of-function activities. Additionally, NSC was synthesized within the NCI which simplifies using this drug in clinical trials. Accomplishments: We established a baseline by first investigating inhibition of cell lines with metabolic inhibitors. All cells responded with a dose dependent reduction in proliferation to metformin and 2-DG. When these inhibitors were used in combination, the reduction in proliferation varied across the panel of cells, however, the effects were uniformly more robust. Additionally, p53 wild-type Barrett's line CP-A was less sensitive to metabolic inhibitors alone than EAC cells. Unfortunately, we have no additional cell lines with wild-type p53. Based on the specific mutations, CP-A, NCI-SB-Esc3, and Eso26 were selected for additional studies. Multiple compounds were initially evaluated, but NSC was chosen for additional treatment and mechanistic experiments. Although we are most interested in the combination of p53 mutant inhibitors with metabolic inhibition, the standard, approved treatments in esophageal cancer includes platinum-based therapy, therefore, we used combination with cisplatin (Cis) as well as metformin (Met). These results reveal that as single agents, both NSC and metformin significantly reduces proliferation of EAC cells. The reduction in proliferation was greater with both in combination than as signal agents. Interestingly, the combination of NSC and cisplatin appeared more robust than metformin and cisplatin. A synergistic reduction in proliferation was noted p53-mutant cells compared to the p53 wild-type cells. Similar results were obtained when apoptosis was measured with cisplatin and NSC . Development of p53 mutant lines within single cells is underway to determine whether the precise mutant can serve as a biomarker for response.
