Fig. 1
Characterization of HCC38 and cisplatin-resistant HCC38CisR. (A) Weekly exposure of HCC38 with the IC50 of cisplatin for 6 h resulted in the cisplatin resistant subclone HCC38CisR with a resistance factor of at least 3.5 (p < 0.001). IC50 cisplatin HCC38: 2.7 μM; IC50 cisplatin HCC38CisR: 9.4 μM. Shown are mean +/− SEM, n = 3. b Detail of phospho-RTK-array displays phosphorylation status of EGFR-family and IGF1R in HCC38 and HCC38CisR. c Immunostaining of expression and activation of signaling kinases. Shown is a representative experiment out of 3. HCC38 cells were treated with 2.5 μM cisplatin for 6 h followed by a recovery of 24 h or 1 week. Untreated HCC38 and HCC38CisR served as controls. d Densitometric analysis of the protein bands of HCC38 and HCC38CisR were performed using ImageJ software (NIH). Data are means ± SD, n = 3. All values have been normalized to HCC38 control. Statistical analysis was performed using one-way ANOVA test (* p < 0.05, ** p < 0.01, and *** p < 0.001). e Cell proliferation measured by flow cytometry-based cell counting. Doubling times were 23.6 h in HCC38 and 16.9 h in HCC38CisR and were significantly different (*** p < 0.001). Shown are mean +/− SEM, n = 3