[Establishment and biological characteristics of a platinum-resistance nude mouse model in epithelial ovarian cancer].

Objective: To establish a platinum resistance nude mice model of epithelial ovarian cancer (EOC) and investigate its resistance to cisplatin (DDP) biological characteristics, so as to provide evidences for exploring chemoresistence mechanisms and screening for reversal targets in vivo micro-environment.

Methods: The resistance model was produced by repeating a crossover subcutaneous injection of human ovarian cancer SKOV3 cells labelled green fluorescent protein (GFP) and transplatation of tumor fragment into nude mice. Two kinds of cancer cell lines of SKOV3/DDP I and SKOV3/DDP II were induced with acquired resistence to DDP. The chemosensitivities of EOC cells to DDP were tested and half maximal inhibitory concentration (IC50) was measured by methyl thiazolyl tetrazolium (MTT) and flow cytometry (FCS). Dynamic analysis among the concentration of DDP treatment and cell apoptosis, cell cycle phase distribution and intracellular DDP concentration. The expression of PTEN, STAT5, XIAP, BRCA1 and MDR1 were examined by real time quantitative reverser transcription PCR (qRT- PCR) in vivo.

Results: IC50 value of cisplatin for SKOV3/DDP II were 2.83 ± 0.12 and 3.82±0.19 folds than those for SKOV3/GFP by MTT and flow cytometry, separately. SKOV3/DDP I were 2.20 ± 0.16 and 3.40 ± 0.20 folds. The apoptosis rate of SKOV3/DDP II and SKOV3/DDP I were decreased significantly at 29.7 and 39.6 µmol/L DDP when treatment for 36 hours, which were lower than that of SKOV3/GFP cells [(57.0 ± 1.4)% vs (37.6 ± 4.36)% vs (83.1 ± 2.71)%, P = 0.024; (74.4 ± 2.3)% vs (50.5 ± 3.4)% vs (87.4 ± 4.0)%, P = 0.001]. SKOV3/DDP I and SKOV3/DDP II was positively related with cisplatin processing time. Intracellular DDP accumulation of SKOV3/DDP II and SKOV3/DDP I were lower than SKOV3-GFP in dynamic processes(P < 0.05). Besides intracellular DDP accumulation of SKOV3/DDP II also lower than SKOV3/DDP I in dynamic processes (P < 0.05). Transplanted tumor of SKOV3/GFP appeared organelle degradation and nuclear membrane imcompleted after five times DDP injection with concentration of 4 mg/kg. SKOV3/DDP II and SKOV3/DDP I did not generate these phenomenon untill eighth DDP injections with concentration of 4 mg/kg. STAT5 and BRCA1 of SKOV3/DDP II were increased with DDP treatment at concentration of 4 mg/kg. Expression of XIAP from SKOV3/DDP II was positive correlated with injection times. STAT5, XIAP and BRCA1 of SKOV3/DDP II were up-regulated 3.86, 28.1 and 14.6 folds than those in SKOV3/GFP cells after eighth DDP treatment, separately. While PTEN of SKOV3/DDP II was decreased 3.77 folds.

Conclusions: We have successfully established platinum-resistent EOC mice model, which provides a new platform for further study on chemoresistant reversal and individualized clinical treatment. The results shown that potential mechanisms of SKOV3/DDP II DDP-resistance included over-expressed BRCA1 gene may be promote DNA damage repair, elevate XIAP gene to decrease cell apoptosis, up- regulated STAT5 gene and decrease PTEN gene to stimulate proliferation.