Abstract A95: Intermittent, but not chronic, hypoxia increased chromosomal copy number variations of prostate cancer cells.

Abstract

Abstract Background: Intra-tumoral hypoxia as a potential mechanism for therapy resistance has been well documented in prostate cancer. Screening drugs under hypoxic conditions, however, has not been adopted for drug discovery. Part of this is due to the difficulty to recapitulate the heterogeneity of intra-tumoral hypoxia in vitro. Indeed, a spatio-temporal irregularity of the microvascular network of a growing tumor creates regions that are either chronically (diffusion-limited) or intermittently (perfusion-limited) hypoxic. If genomic instability is the fundamental driving force for development of therapy resistance, the hypoxic culture condition with the most genomic instability would serve as an alternative in vitro model for drug testing. We therefore accessed chromosomal copy number variations (CCNV) in prostate cancer cells grew under intermittent as well as chronic hypoxia. Method: Metastatic prostate cancer cell lines, PC3 and DU145, were grown under normoxia (21% oxygen), chronic hypoxia (0.2% oxygen), or intermittent hypoxia (16 hours of 0.2% oxygen alternating with 8 hours of 21% oxygen) for total of 3 weeks. PC3 cells were also treated with the 1 µM poly(ADP-ribose) polymerase (PARP) inhibitor, veliparib under intermittent or chronic hypoxia conditions for 3 weeks. Genomic DNA was extracted for molecular karyotyping with the nanoString nCounter human karotyping platform, which covers 24 human chromosomes with 338 probes. DNA from human foreskin fibroblast (HFF) grew under normal culture condition (21% oxygen) was used as a reference. Results: Both PC3 and DU145 cells continue to proliferate under intermittent as well as chronic hypoxia. Compared to untreated PC3 cells, daily treatment with PARP inhibitor under chronic or intermitent hypoxia for 3 weeks did not affect the proliferation or survival of the PC3 cells. Compared to HFF, frequent CCNVs were observed in PC3 and DU145 cells. This is consistent with the known complicated karyotype of these 2 cell lines. When compared to PC3 or DU145 cells cultured under normoxia, CCNVs were enhanced under intermittent hypoxia, but not chronic hypoxia. Daily treatment with PARP inhibitor did not alter CCNVs under either chronic hypoxia or intermittent hypoxia. Conclusions: Intermittent hypoxia is probably a more relevant model to study genomic instability and drug resistance than chronic hypoxia. Neither chronic hypoxia nor intermittent hypoxia sensitizes prostate cancer cells to PARP inhibitor, veliparib. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A95. Citation Format: Jingsong Zhang, Xue Wang. Intermittent, but not chronic, hypoxia increased chromosomal copy number variations of prostate cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A95.