Figure 1.

In vitro cytostatic activity of [V⁴Q⁵]dDAVP in combination with 5-fluorouracil on colorectal cancer cells and its impact on apoptosis induction and cell cycle progression. (a) Cytotoxic activity of 5-fluorouracil on COLO-205 (left) and CT-26 (right) colorectal cancer cells and IC₅₀ calculation after a 72-h exposure to chemotherapeutic agent. (b) Effect on colorectal cancer cell viability of [V⁴Q⁵]dDAVP (1 µM) addition to 5 µM 5-fluorouracil for COLO-205 cells (left) or 0.5 µM for CT-26 cells (right). Direct cytotoxic/cytostatic effects on cancer cells were assessed by the metabolic MTS assay. (c) Cell cycle phase distribution evaluated by flow cytometry for COLO-205 cells after 24 h treatment with [V⁴Q⁵]dDAVP (1 µM), 5-fluorouracil (5 µM) or dual combined therapy. (d) Percentage of apoptotic cells after 48 h treatment with [V⁴Q⁵]dDAVP (1 µM), 5-fluorouracil (5 µM) or its combination in human colorectal cancer cell cultures. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL). (e) Representative images of TUNEL labeling in human COLO-205 cell cultures under different treatments (× 200 magnification. Scale bar = 200 µm). (f) Relative gene expression of cyclin-dependent kinase inhibitor p21 (CDKN1A) and the tumor suppressor p53 (TP53) by quantitative reverse transcription polymerase chain (qRT-PCR) in colorectal cancer cells after 24 h treatment with [V⁴Q⁵]dDAVP and 5-fluorouracil, in combination or as monotherapies. Data are presented as mean ± standard error of mean (SEM) (a, c, f), box and whiskers with minimum to maximum values (b) or violin plots (d) and are representative of at least two or three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001 and ****P < 0.0001.