title: Bcl-2 confers survival in cisplatin treated cervical cancer cells: circumventing cisplatin dose-dependent toxicity and resistance.
abstract: BACKGROUND
  Cisplatin is the main chemotherapeutic drug for the treatment of cervical cancers, however resistance to cisplatin is increasingly common and therefore has limited the efficacy and use of this drug in the clinic. Dose-dependent toxicity poses an additional challenge since patients suffer long-term and often permanent side-effects after treatment. Bcl-2 up-regulation has been implicated in the resistance to cisplatin in a variety of cancer cell lines, however its role in cervical cancer is confounding.
  
  
  METHODS
  A low, non-cytotoxic concentration of cisplatin was used in the treatment of HeLa and CaSki cells. Bcl-2 expression was determined through Western blotting and immunocytochemistry before and after treatment with cisplatin. To assess the reliance of the cervical cancer cells on Bcl-2 in the presence of cisplatin, Bcl-2 knock-down was achieved through RNA interference, where after apoptosis was assessed through PARP cleavage (Western blotting), Caspase activity (Caspase-Glo(©)) and PI inclusion analysis (Flow cytometry). Finally, pre-malignant and malignant cervical tissue was analysed for the presence of Bcl-2 through Western blotting and immunofluorescence.
  
  
  RESULTS
  Cervical cancer cells upregulate Bcl-2 when treated with a non-cytotoxic concentration of cisplatin, which when silenced, effectively enhanced cisplatin sensitivity, and therefore significantly induced apoptosis. Analysis of the expression profile of Bcl-2 in cervical tissue revealed its up-regulation in cervical carcinoma, which agrees with results obtained from the in vitro data.
  
  
  CONCLUSIONS
  Our data strongly suggest that utilising a lower dose of cisplatin is feasible when combined with Bcl-2 silencing as an adjuvant treatment, thereby improving both the dose-dependent toxicity, as well as cervical cancer resistance.
authors.affiliation: Department of Physiological Sciences, Stellenbosch University, c/o Merriman and Bosman road, Stellenbosch, South Africa. ginal@sun.ac.za.
authors.forename: Gina
authors.initials: G
authors.lastname: Leisching
authors.affiliation: Department of Physiological Sciences, Stellenbosch University, c/o Merriman and Bosman road, Stellenbosch, South Africa. bloos@sun.ac.za.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Loos
authors.affiliation: Department of Obstetrics and Gynaecology, Stellenbosch University, Stellenbosch, South Africa. mhbotha@sun.ac.za.
authors.forename: Matthys
authors.initials: M
authors.lastname: Botha
authors.affiliation: Department of Physiological Sciences, Stellenbosch University, c/o Merriman and Bosman road, Stellenbosch, South Africa. ame@sun.ac.za.
authors.forename: Anna-Mart
authors.initials: AM
authors.lastname: Engelbrecht
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000071186:Beclin-1; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology*; D002945:Cisplatin / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology*; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D002945:Cisplatin