Research

Synthesis and biologic properties of hydrophilic sapphyrins, a new class of tumor-selective inhibitors of gene expression

Zhong Wang¹ , Philip S Lecane¹ , Patricia Thiemann¹ , Qing Fan¹ , Cecilia Cortez¹ , Xuan Ma¹ , Danielle Tonev¹ , Dale Miles¹ , Louie Naumovski¹ , Richard A Miller¹ , Darren Magda¹ , Dong-Gyu Cho² , Jonathan L Sessler² , Brian L Pike³ , Samantha M Yeligar³ , Mazen W Karaman³ and Joseph G Hacia³

¹  Pharmacyclics, Inc., Sunnyvale, California, USA

²  Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas, USA

³  Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California, USA

author email corresponding author email

Molecular Cancer 2007, 6:9doi:10.1186/1476-4598-6-9

Published:	19 January 2007

Abstract

Background

Sapphyrin analogues and related porphyrin-like species have attracted attention as anticancer agents due to their selective localization in various cancers, including hematologic malignancies, relative to surrounding tissues. Sapphyrins are electron affinic compounds that generate high yields of singlet oxygen formation. Although initially explored in the context of photodynamic therapy, sapphyrins have intrinsic anticancer activity that is independent of their photosensitizing properties. However, the mechanisms for their anticancer activity have not been fully elucidated.

Results

We have prepared a series of hydrophilic sapphyrins and evaluated their effect on proliferation, uptake, and cell death in adherent human lung (A549) and prostate (PC3) cancer cell lines and in an A549 xenograft tumor model. PCI-2050, the sapphyrin derivative with the highest in vitro growth inhibitory activity, significantly lowered 5-bromo-2'-deoxyuridine incorporation in S-phase A549 cells by 60% within eight hours and increased levels of reactive oxygen species within four hours. The growth inhibition pattern of PCI-2050 in the National Cancer Institute 60 cell line screen correlated most closely using the COMPARE algorithm with known transcriptional or translational inhibitors. Gene expression analyses conducted on A549 plateau phase cultures treated with PCI-2050 uncovered wide-spread decreases in mRNA levels, which especially affected short-lived transcripts. Intriguingly, PCI-2050 increased the levels of transcripts involved in RNA processing and trafficking, transcriptional regulation, and chromatin remodeling. We propose that these changes reflect the activation of cellular processes aimed at countering the observed wide-spread reductions in transcript levels. In our A549 xenograft model, the two lead compounds, PCI-2050 and PCI-2022, showed similar tumor distributions despite differences in plasma and kidney level profiles. This provides a possible explanation for the better tolerance of PCI-2022 relative to PCI-2050.

Conclusion

Hydrophilic sapphyrins were found to display promise as novel agents that localize to tumors, generate oxidative stress, and inhibit gene expression.