Aim
Evasion of apoptosis is a hallmark of human cancer cells. We sought to explore the potential synergistic antitumor activity and underlying mechanisms of the pro-apoptotic agent PAC-1 plus cisplatinum (Cis) in non-small cell lung cancer (NSCLC) cell lines.
Conclusions
PAC-1 showed anti-tumor activity in NSCLCs in vitro and a synergistic effect with cisplatin in EGFR(wt)KRAS(wt) H1299 cells. Our data suggest a potential treatment approach using cisplatin plus a pro-apoptotic agent acting via CASP3 activation for this subgroup of pulmonary adenocarcinomas.
Methods
The adenocarcinoma cell lines H1299, A549, PC9, H1650 and H1975 were used as in vitro models. Colorimetric MTT assays, Western blotting and flow cytometry were used to evaluate the anti-growth effects of PAC-1 and/or Cis and apoptosis status. The activated form of CASP3 (C-CASP3) was assessed by immunofluorescent staining.
Results
Single-agent Cis and PAC-1 were able to inhibit the cancer cell growth in certain dose ranges, with IC50 values of 1.9-11.7 and 5.6-14.8 μM, respectively. Sequential Cis→PAC-1 or concurrent Cis + PAC-1, but not PAC-1→Cis combinations showed synergistic effects on cell growth inhibition in H1299 cells (combination index, CI ≤ 0.6). In contrast, other combination modes mostly showed seemingly antagonistic effects (CI > 1.0). Flow cytometric analysis showed that Cis→PAC-1 sequential combination showed strong pro-apoptotic effects in H1299 cells. Western blots showed that in H1299, PC9 and H1975 cells, PAC-1 promoted the C-CASP3, but only in H1299 cells was there a synergistic effect with Cis on the CASP3 activation. Conclusions: PAC-1 showed anti-tumor activity in NSCLCs in vitro and a synergistic effect with cisplatin in EGFR(wt)KRAS(wt) H1299 cells. Our data suggest a potential treatment approach using cisplatin plus a pro-apoptotic agent acting via CASP3 activation for this subgroup of pulmonary adenocarcinomas.