Abstract 1861: Aviscumine (ME-503) suppresses the growth of melanoma by potentially targeting c-Myc pathway

Aviscumine, a recombinant mistletoe lectin I, is produced in E. coli and has been evaluated for its antitumor activities in various experimental in-vitro and in-vivo tumor models as well as in clinical trials. A phase II trial demonstrated the safety and efficacy of Aviscumine in pretreated patients with metastatic melanoma (stage IV). However, the mechanism(s) underlying the effect of Aviscumine in melanoma is inconclusive. Here, the antitumor activities and relevant mode of actions of Aviscumine were investigated in human melanoma A375, mouse melanoma Yummer and B16 cells as well as their relevant xenograft animal models. Cells were treated with Aviscumine (0-20 ng/mL) for 48 and 72 hrs, and cell proliferation was measured by MTT assay. Alteration of cell growth regulatory proteins and cell signaling proteins were determined by Reverse Phase Proteomic Array (RPPA) and validated with western blotting. Aviscumine exerted much stronger anti-proliferative activity in both A375 and Yummer cells with IC50 of 0.18 ± 0.03 ng/ml and 0.41 ± 0.06 ng/ml, respectively than that of B16 cells (IC50 15.93 ± 3.48 ng/ml). In A375 cells, Aviscumine significantly increased subG0/G1 population suggesting Aviscumine treatment led to apoptotic and necrotic cell death. Additionally, downregulation of various proteins associated with apoptotic cell death (pCDK1, pRB, MCl-1) was also observed by RPPA. Furthermore, Aviscumine significantly decreased c-Myc protein expression in a concentration-dependent manner measured by both RPPA and western blot. Interestingly, baseline c-Myc protein expression was much higher in the Aviscumine-sensitive A375 and Yummer cells than that in the Aviscumine-resistant B16 cells. Finally, the effects of Aviscumine on tumor growth were tested via subcutaneous injection (30 ng/kg, twice per week for three weeks) in mice bearing A375 or B16 melanoma. At 3 weeks, A375 tumors were markedly smaller in Aviscumune treated mice (383.8 ± 102.2 mg) than in the control-treated group (922.4 ± 296.1 mg). c-Myc protein expression was also significantly reduced (62% vs. control) in Aviscumine treated A375 tumors, as were levels of multiple downstream metabolites (pyruvate, malate, and glutamate) (p Citation Format: Peiying Yang, Tara Conway, Patrea Rhea, Dongmei Chen, Bo Wei, Jibin Ding, Hans Lentzen, Jennifer McQuade. Aviscumine (ME-503) suppresses the growth of melanoma by potentially targeting c-Myc pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1861.