Date of Award

2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Ahmed AI-Marzouqi

Second Advisor

Dr. Sehammudine Galadari

Third Advisor

Prof. Evelyn Tiffany-CastigJioni

Abstract

Nucleosides and their analogs are considered a clinically proven class of therapeutic agents possessing anticancer and antiviral activity. Several trifluoromethyl-substituted pyrazole N-nucleosides (coded NIA, NIIA and NIIA) and their nucleobases were synthesized and tested for the ability to induce apoptosis in acute human promyelocytic cell line (HL-60). The growth and proliferation of HL-60 was more effectively inhibited by NIA, NIIA and their nucleobases compared to NIIIA and its nucleobase. In addition, DNA fragmentation was detected in a concentration-dependent manner as a result of nucleosides treatment. A caspase-3-dependent apoptosis was observed based on the Western blot analysis of poly-ADP-ribose polymerase (PARP) and caspase-3. Nucleosides and nucleobases also trigger the release of cytochrome-c from the mitochondria by disruption of mitochondrial membrane potential and ROS formation. Furthermore, the use of zDEVD-fmk (caspase-3 inhibitor) and zLEHD-fmk (caspase-9 inhibitor) resulted in an inhibition of the activity of caspase-3 and 9, accompined with no change in the activity of caspase-8 after the use of zIETD-fmk (casapse-8 inhibitor). These findings implicate the involvement of the caspase-9-dependent mitochondrial pathway. Treatment with nucleosides also resulted in a concentration-dependent upregulation and translocation of the proapoptotic molecule Bax, increased expression of other proapoptotic proteins Bad, Bak, decreased expression of antiapoptotic proteins (i.e. Bcl-2 and Bcl-xL), and enhancement of p53 expression. Moreover, treatment with these agents resulted in accumulation of cells in the G0-G1 phase of the cell cycle, indicating the degradation of the cellular DNA. Interestingly, these nucleosides were found to posses anti-histone deacetyl transferase(s) (HDACs) potential, which is an exciting turn in cancer therapy. This conclusion was based on the observed decease in the expressed level of HDAC-1, -2 and -3. Our results suggest that these novel synthetic nucleosides can induce apoptosis via the mitochondrial pathway, and therefore they could be considered as candidate anti-tumor agents.

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