Antineoplastic activity of povidone-iodine on different mesothelioma cell lines: results of in vitro study

Abstract

Objective: Povidone-iodine (PVP-I) or Betadine, owing to its antineoplastic activity, is also used as an adjuvant during intra-abdominal or intrathoracic surgery. However, the protocol of PVP-I administration has not been optimized to achieve the best antitumoural efficacy. We aimed to determine the optimal concentration of PVP-I, the time of incubation and the mechanism of cell death by analysing the effect of different doses and time of administration of PVP-I on the cell viability of different mesothelioma cell lines.

Methods: Four different cell lines (MET 5A/normal mesothelium; H2052/sarcomatoid mesothelioma; ISTMES2/epithelial mesothelioma; MSTO/biphasic mesothelioma) were incubated with increasing concentrations of diluted PVP-I (0.0001; 0.001; 0.01; 0.1; 1%) for 5, 10, 30, 60 min and 24 h, respectively. Cell viability was determined using cell direct cytotoxicity assay and cell death was determined through flow cytometry assay analysis. The superoxide dismutase activity was assessed functionally through a specific inhibitor to evaluate the mechanism of cell death.

Results: The antiproliferative effect of PVP-I varied largely among different cell lines in a dose- and time-dependent manner. At 0.1% concentration for 10 min of incubation, the percentage of viable cells was 0.5 ± 0.1; 0.8 ± 0.5 and 0% (P < 0.01) for MET5A, ISTMES2 and MSTO, respectively. Conversely, the same concentration did not significantly affect the H2052 cell line which was completely suppressed at a 1% concentration of PVP-I. Double staining of Annexin V and DNA showed that PVP-I induced cell death in all four cell lines via necrosis depending on PVP-I concentration. However, H2052 was found to be more resistant than MSTO, ISTMES2 and MET 5A cells lines. The activity of superoxide dismutase was significantly inhibited in all cell lines.

Conclusions: Our results confirmed the anti-neoplastic activity of PVP-I especially on ISTMES2 and MSTO cell lines. With respect to chemotherapy pleural irrigation, washing with PVP-I is cost-effective and easy. If confirmed by larger studies, our findings suggest that the intrapleural irrigation with PVP-I (0.1% concentration for 10 min) in patients with epithelial or biphasic mesothelioma undergoing cytoreductive surgery might be applied in thoracic surgery practice to prevent neoplastic cell growth.

Keywords: Betadine; Mesothelioma; Povidone-iodide.

Figure 1:

MTS assay of cell viability (y-axis) of MET5A, ISTMES2, MSTO and H2052 cells treated with different concentrations of PVP-I (x-axis). Cells were treated with different Betadine concentrations (0.0001; 0.001; 0.01%; 0.1; 1%) for 5, 10, 30, 60 min and 24 h, respectively. (A) MTS assay of MET5A cells; (B) MTS assay of ISTMES2; (C) MTS assay of MSTO; (D) MTS assay of H2052. The results are reported as the means of three independent experiments, each conducted in triplicate, and expressed as percentages of cell growth (calculated with respect to the control cells treated with water alone). The results showed that PVP-I inhibited the growth of MET5A, ISTMES2, MSTO and H2052 cells in a dose- and time-dependent manner.

Figure 2:

After 10 min of incubation at a concentration of 0.1%, the percentage of cell viability was significantly decreased with respect to that observed using lower concentrations (0.0001; 0.001; 0.01%), whereas no significant difference was found for a higher concentration (1%) for MET5A (A); for ISTMES2 (B) and for MSTO (C). Among all three different cell lines, no significant differences were found after longer incubation times (D for MET5A, E for ISTMES2 and F for MSTO).

Figure 3:

At 0.1% concentration, the H2052 cell line was highly resistant to PVP-I, having a survival rate of more than 50% also after 24 h of incubation (A). A significant decrease in survival rate in a time-dependent manner was observed using a higher PVP-I concentration (1%) (B).

Figure 4:

Dot plots obtained by FACS analysis after incubation of MET5A, ISTMES2, MSTO and H2052 cell lines with different concentrations of PVP-I for 24 h. FACS analysis was performed for Annexin V-FITC (x-axis) and propidium iodide (PI) staining (y-axis). A representative experiment is shown out of three independent ones.

Figure 5:

Inhibition of SOD activity (y-axis) induced by different concentrations of PVP-I (x-axis). Among the MET5A (A); ISTMES2 (B) and MSTO (C) cell lines, the activity of SOD in the 0.1% PVP-I-treated group was significantly inhibited compared with lower concentration groups and had a similar value compared with the 1%-treated group. The activity of SOD assay on H2052 cell line (D) was significantly inhibited at 1% concentration with respect to the other groups.