Oral Recombinant Methioninase Overcomes Colorectal-cancer Liver Metastasis Resistance to the Combination of 5-Fluorouracil and Oxaliplatinum in a Patient-derived Orthotopic Xenograft Mouse Model

Background/Aim: Liver metastasis in colorectal-cancer is a recalcitrant disease. To develop precision individualized therapy of this disease, we developed a patient-derived orthotopic xenograft (PDOX) model of colorectal-cancer liver metastasis. In the present report, we evaluated the efficacy of oral recombinant methioninase (o-rMETase) in combination with 5-fluorouracil (5-FU) and oxaliplatinum (OXA) on the colorectal-cancer liver metastasis PDOX mouse model. Materials and Methods: Colorectal-cancer liver metastasis PDOX models were randomized into three groups of seven mice. Group 1, untreated control with phosphate buffered saline (PBS); Group 2, treated with 5-FU + OXA; and Group 3, treated with 5-FU + OXA + o-rMETase. Results: The colorectal-cancer liver metastasis PDOX model was resistant to 5-FU + OXA (p=0.83 at day 15 of treatment, Group 2). In contrast, the colorectal-cancer liver metastasis PDOX model was arrested by o-rMETase combined with 5-FU + OXA (p<0.01 at day 15, Group 3). No significant body-weight differences were observed among the groups. Conclusion: The combination therapy of 5-FU and OXA with o-rMETase can overcome the resistance of first line drugs for colorectal-cancer liver metastasis.