ID: 2262

• Title:
  Electroporation increases the cytotoxicity of two potent platinum(II) complexes in human tumor cells and spheroids
  
  Authors:
  

  Kranjc Brezar Simona 1,2-1 Institute of Oncology Ljubljana, Ljubljana, Slovenia;1 University of Ljubljana, Medical Faculty, Ljubljana, Slovenia
  Scancar Janez 3-3 Jožef Stefan Institute, Ljubljana, Slovenia
  Bucek Simon 1-1 Institute of Oncology Ljubljana, Ljubljana, Slovenia 
  Iztok Turel 5-5 University of Ljubljana, Faculty of Chemistry and Chemical Technology Ljubljana, Slovenia
  Cemazar Maja 1,6- 1 Institute of Oncology Ljubljana, Ljubljana, Slovenia; 6University of Primorska, Faculty of Heal
  
  
  

  
  
  Abstract:
  Cisplatin (CDDP) is a well-known platinum antitumor drug (II) whose antitumor activity is associated with its ability to form DNA adducts that subsequently lead to cell death. Although CDDP is broadly used, its major limitations are severe side effects and innate or acquired tumor cell resistance. Therefore, researchers are trying to develop new platinum(II)complexes with fewer side effects. Recently, [PtCl (5,7-dibromo-8-quinolinol) (S-dmso)] (complex A) and its analog, [PtCl (5,7-dibromo-8-quinolinol) (pta)] (complex B), hawe been synthesized. Both complexes demonstrate considerable anticancer activity in vitro. To improve the cytotoxicity of complexes A and B in vitro, electroporation was used as a physical drug delivery method to increase membrane permeability and drug uptake.
  
  
  
  Survival of human ovarian carcinoma IGROV 1 and its resistant subclone to cisplatin IGROV 1/RDDP, breast carcinoma MCF7, colon carcinoma HT29 cells and spheroids (MCF7, HT29) was determined after electroporation with complex A or complex B and compared to electroporation with CDDP using a clonogenic assay or growth delay assay, respectively. To detect increased drug uptake after electroporation with complex A, B, or CDDP, intracellular concentrations of all tested compounds were determined by inductively coupled plasma mass spectrometry. In addition, cell cycle analysis was performed by flow cytometry after treatment. Besides, the apoptotic and necrotic cells at 24 and 72 hours after electroporation with complex A, B, or CDDP was examined by Giemsa staining.
  
  All complexes alone, A, B, and CDDP were cytotoxic in a dose-dependent manner in all tumor cell lines and spheroids tested. In addition, electroporation proved to be an effective method for drug uptake, as it significantly increased Pt concentration in cells and Pt bound to DNA (up to 3.5-fold), resulting in increased cytotoxicity of all three platinum(II) complexes. In MCF7, IGROV1, and IGROV1/RDDP cells, the highest cytotoxicity was observed after electroporation with CDDP, resulting in an enhancement factor of up to 4.8, whereas complexes A and B exhibited lower and similar cytotoxicity, resulting in an enhancement factor of up to 3.0 and 3.2, respectively, compared with exposure of cells to the complexes alone. Interestingly, the most pronounced cytotoxicity (5.6-fold) was observed in HT29 cells after electroporation with complex B compared with CDDP (3.2-fold) and complex A (3.1-fold). Moreover, electroporation with CDDP induced cell arrest in the G0/G1 phase, and with increasing time after treatment (from 24 hours to 72 hours), cells gradually accumulated in the G2 phase. A similar redistribution of cells was achieved after electroporation with complex A or complex B. Also, treatment of cells with platinum(II) complexes alone or in combination with electroporation resulted in primary apoptotic cell death as early as 24 hours after treatment, leading to a 2- to 7-fold increase in apoptotic compared with necrotic cells. In addition, similarly increased cytotoxicity was observed in spheroids with all compounds tested, but this was less pronounced compared with cell treatment.
  
  Overall, complex B was found to be more cytotoxic than complex A with and without electroporation and showed similar cytotoxicity to CDDP in all cell lines and spheroids tested. Based on our results, complex B is a very promising potential therapeutic agent that is also cytotoxic in cisplatin-resistant tumor cells. Further in vivo studies are warranted.
  
  
  
  Keywords:
  electroporation , platinum (II) complexes, cisplatin, cancer cells, spheroids
  
  Refs:
  
  
  Topic 1:
  12. Biomedical applications
  
  Topic 2:
  1. Biological responses (molecular, subcellular, cellular and intercellular)