Vasopressin Analog [V(4)Q(5)]dDAVP Exerts Cooperative Anticancer Effects in Combination With Low-Dose 5-Fluorouracil on Aggressive Colorectal Cancer Models

BACKGROUND: Colorectal cancer (CRC) is a leading cause of cancer-associated mortality worldwide. Despite being an essential component of systemic chemotherapy for advanced CRC, 5-fluorouracil (5-FU) clinical use has severe limitations, such as high toxicity, low selectivity and drug resistance. [V(4)Q(5)]dDAVP (1-deamino-4-valine-5-glutamine-8-D-arginine vasopressin) is a peptide vasopressin analog and a selective agonist of the arginine vasopressin type 2 membrane receptor (AVPR2), expressed in microvascular and tumor tissue. This synthetic compound has well-proven antitumor and antimetastatic activity in different tumor types, including metastatic CRC. The objective of this work was to assess the potential combinational benefits in preclinical CRC models after [V(4)Q(5)]dDAVP addition to 5-FU. METHODS: Effects on cellular viability, cell cycle progression, apoptosis and molecular mechanisms associated to [V(4)Q(5)]dDAVP treatment in combination with 5-FU were evaluated in murine CT-26 and human COLO-205 cell lines. In vivo, impact of dual therapy was explored on CRC tumor growth and metastatic spread. RESULTS: In CRC cells, [V(4)Q(5)]dDAVP (1 µM) addition to sub-IC(50) 5-FU concentrations resulted in the enhancement of cytostatic effects induced by chemotherapy. Reduction of cell viability after combined treatment was associated with cell cycle arrest in the G(0)/G(1) phase, induction of apoptosis and increased gene expression of the cyclin-dependent kinase inhibitor p21 (CDKN1A) and the tumor suppressor p53 (TP53) in malignant cells, as assessed by flow cytometry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL), and quantitative reverse transcription polymerase chain reaction (qRT-PCR), respectively. In vivo, intravenous administration of [V(4)Q(5)]dDAVP (0.3 µg/kg) in combination with safe low doses of 5-FU (50 or 80 mg/kg for CT-26 or COLO-205 tumor models, respectively) effectively abrogated CRC growth, reducing aggressiveness of primary lesions and increasing survival of tumor-bearing mice. In addition, concomitant administration of [V(4)Q(5)]dDAVP and 5-FU inhibited pulmonary metastasis formation by CT-26 cells in immunocompetent mice, especially reducing macrometastatic disease. CONCLUSIONS: [V(4)Q(5)]dDAVP seems to enhance the efficacy of 5-FU-based chemotherapy in CRC by modulating tumor progression, as well as metastatic dissemination, suggesting its potential role as a safe and cost-effective co-adjuvant agent for the management of advanced CRC.