Oral Methioninase Inhibits Recurrence in a PDOX Mouse Model of Aggressive Triple-negative Breast Cancer
Hye In Lim, Kazuyuki Hamada, Jun Yamamoto, QINHONG HAN, Yuying Tan, Hee Jun Choi, Seok Jin Nam, Michael Bouvet, Robert M. Hoffman
Abstract
Background/Aim: The aim of the study was to use a triple-negative breast cancer (TNBC) patient-derived orthotopic xenograft (PDOX) model to examine the efficacy of oral recombinant methioninase (o-rMETase) against this recalcitrant disease. Materials and Methods: The TNBC tumor from a patient was implanted in the right 4<sup>th</sup> inguinal mammary fat pad of nude mice. Two weeks later, the mice underwent tumorectomy with grossly-negative surgical margins. Two days after tumorectomy the mice were divided in two groups: one control and one treated with o-rMETase. Results: Tumors recurred in all mice. On day 11, the mean recurrent tumor volumes were 936.7 mm<sup>3</sup> in the control group and 450.9 mm<sup>3</sup> in the o-rMETase group (p<0.05). On day 15, the mean recurrent tumor volumes were 3392.5 mm<sup>3</sup> in the control group and 1603.5 mm<sup>3</sup> in the o-rMETase group. The mean recurrent tumor weights were 2.1 g in the control group and 1.1 g in the o-rMETase group on day 15. Conclusion: o-rMETase is an effective adjuvant treatment for aggressive TNBC.