Adjuvant Oral Recombinant Methioninase Inhibits Lung Metastasis in a Surgical Breast-Cancer Orthotopic Syngeneic Model

Abstract

Background/Aim: In the present study, we evaluated the efficacy of adjuvant administration of oral recombinant methioninase (o-rMETase) against recurrence and metastasis in a 4T1 murine breast-cancer syngeneic model. Materials and Methods: 4T1 cells were orthotopically implanted into the 2nd mammary fat pad of BALB/c mice. The 4T1 orthotopic syngeneic models were randomized into 2 groups after primary tumor resection: untreated control and o-rMETase (100 units, oral, daily, 2 weeks). Results: The frequency and extent of local recurrence were reduced by o-rMETase. The number of individual cancer cells and metastatic nodules on the lung surface was significantly lower in the o-rMETase-treated mice than the untreated control mice. Conclusion: Adjuvant o-rMETase inhibited local recurrence and lung metastasis after primary tumor resection. Methionine addiction is possibly the most fundamental and general hallmark of cancer (1-9) and is tightly linked to other hallmarks of cancer (2). Methionine addiction was discovered in our laboratory and is due to increased rates of transmethylation compared to normal cells (3-6). Methionine overuse by cancer cells is called the "Hoffman effect", analogous to the "Warburg effect" of glucose overuse by cancer cells (7). Methionine restriction targets the methionine addiction of cancer. For methionine restriction, we have used L-methionine-deamino-mercapto-methanelyase (methioninase) (8, 9). Recombinant methioninase (rMETase) has been produced in Escherichia coli containing the methioninase gene cloned from Pseudomonas putida (9). We have reported the efficacy of oral administration of rMETase (o-rMETase) on various types of tumors in vivo, including patient-derived orthotopic xenograft (PDOX) mouse models (10-16). Breast cancer needs follow-up for long periods after treatment. Although distant recurrence can be detected mostly in the first 5 years, there is still a significant rate of recurrence in the second and the third 5-year periods (17, 18). In order to reduce recurrence and improve survival, systemic adjuvant therapy is administered as the standard of care. Adjuvant endocrine therapy for at least 5 years is recommended for patients with hormone receptor-positive breast cancer (19, 20). Oral endocrine therapy is tolerable long term. However, patients with hormone receptor-negative breast cancer are recommended to take one regimen of adjuvant chemotherapy after surgery and be frequently followed-up for over 5-years. If a novel treatment, tolerable for 5 years, decreases the recurrence rate, it would be recommended for patients with hormone receptor-negative breast cancer. Murine breast cancer cell lines have been used to generate orthotopic syngeneic models (21-25), especially the 4T1 cell line which has the characteristics of human triple-negative breast cancer (TNBC) and is highly metastatic (21-24). Additionally, the lung is the most frequent site for metastasis in 4T1 orthotopic models. In the present study, we evaluated the efficacy of adjuvant o-rMETase on local recurrenc...

Oral-recombinant Methioninase Converts an Osteosarcoma from Methotrexate-resistant to -sensitive in a Patient-derived Orthotopic-xenograft (PDOX) Mouse Model

“…r-METase effectively degrades external methionine (63). The efficacy of orally-administrated r-METase (o-rMETase) was shown previously shown in many types of cancer in PDOX models (18,21,22,(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(51)(52)(53)(54)(55)(56)(57)(58). We have also reported the efficacy of rMETase on PDOX models of osteosarcoma including o-rMETase (8,10,18,21,22).…”

“…o-rMETase has also been shown to prevent obesity, diabetes and fatty liver in mouse models (47)(48)(49). o-rMETase has also shown apparent clinical efficacy in advanced prostate cancer (50), reflecting its efficacy in PDOX models of advanced cancers (51)(52)(53)(54)(55)(56)(57)(58).…”

Dietary Manipulation of Amino Acids for Cancer Therapy

“…PEGylated-METase extended this half-life and prevents anaphylactic reactions in primates [154]. Surprisingly, an oral administration of METase, which removes Met from the gastrointestinal tract, was as effective as an intraperitoneal administration in lowering serum Met levels and inducing anticancer activity in several murine cancer models [155][156][157][158][159][160][161][162]. Other human recombinant enzymes have recently been developed [163,164].…”

“…Enzymatic Met depletion has shown synergistic effects with 5-fluorouracil [149], cisplatin [148], temozolomide [150,151], nitrosourea [150], and doxorubicin [152]. Oral METase has also shown a synergistic effect in combination with various anticancer drugs [155][156][157][158][159][160][161][162]. The pharmacokinetics and safety of METase have also been evaluated in patients.…”

Elimination of Axillary-Lymph-Node Metastases in a Patient With Invasive Lobular Breast Cancer Treated by First-line Neo-adjuvant Chemotherapy Combined With Methionine Restriction

“…We have produced recombinant methioninase (rMETase) (12), an enzyme that catabolizes methionine, and have demonstrated the effectiveness of rMETase in breast cancer using patientderived orthotopic xenograft (PDOX) models (13)(14)(15)(16).…”