Antagonistic effect of cisplatin on paclitaxel cytotoxicity against cervical cancer in vitro when applied in doses ratio recommended in clinics.
Authors: Filippova Svetlana Yu , Kit Oleg I. , Sitkovskaya Anastasia O. , Mezhevova Irina V. , Gnennaya Nadezhda V. , Shamova Tatiana V. , Timofeeva Sofia V. , Novikova Inna A. , Menshenina Anna P. , Moiseenko Tatiana I. , Verenikina Ekaterina V. , Tumanyan Sergey V. , Abdullaeva Nina M. , Zhenilo Oksana E. , Selezneva Olga G. , Chernikova Natalia V. , Ardzha Anna Yu , Adamyan Meri L. 
Published: June 2022

e15003 Background: Taxanes and platinum compounds are widely used in cervical cancer chemotherapy. In particular, a combination of 75 mg/m2cisplatin and 175 mg/m2 paclitaxel, which suggests a doses ratio of 1:2.3, is recommended as first-line systemic chemotherapy. Although this combination has performed well in clinical practice, little is known about its effect on cervical cancer cell biology in vitro. This study assessed the effect of combined application of cisplatin and paclitaxel in a dose ratio of 1:2.3 on HeLa cells. Methods: HeLa cells were seeded at 3000 cells per well in a 96-well plate (Eppendorf, Germany) and incubated for 24 hours in DMEM medium (Gibco, USA) supplemented with 10% FBS (HyClone, USA) at 37°C in an atmosphere containing 5.0% CO2. After 24 hours, the culture medium was replaced with a medium containing chemotherapy drugs in combination or as standalone agents in a series of two-fold dilutions: 0.03 - 32 µg/mL cisplatin and 0.07 - 73.6 µg/mL paclitaxel. After 2 h exposition to studied compounds the medium was replaced and cells were incubated for another 72 hours. At the end of the experiment, the number of living cells was assessed using the MTT test. Viability was determined as the number of living cells in % of the control without the addition of chemotherapy drugs. Results: The combination of cisplatin with paclitaxel demonstrated significantly greater efficacy than pure cisplatin in the concentration range from 0.03 μg/ml to 8 μg/ml. The difference between the mean viability values for each concentration between pure cisplatin and its 1:2.3 mixture with paclitaxel was significant at α = 0.05 (df = 14). The decrease in viability is especially dramatic at non-toxic concentrations of cisplatin (0.03 - 0.5 μg/ml) and is about 60% over this concentration range. However, when moving to toxic concentrations of cisplatin (0.5-32 μg/ml), the difference in the viability of HeLa cells between pure cisplatin and its combination with paclitaxel linearly decreases with increasing cisplatin concentration, becoming insignificant in the range of 8-32 µg/ml. However, when comparing the dose-response curves for pure paclitaxel and its combination with cisplatin, we see a significant reduction in cytotoxic activity compared with pure paclitaxel. The difference in cell viability reaches its maximum (45%) at a paclitaxel concentration of 2.3 µg/ml and is significant at α = 0.05 (df = 14). Conclusions: The combined use of cisplatin and paclitaxel in a dose ratio of 1:2.3 on HeLa culture has a greater cytotoxic activity compared to pure cisplatin. However, compared with pure paclitaxel, the effectiveness of its combination with cisplatin is significantly lower, which indicates the antagonism of the two substances.