By Lata Chauhan
There is a wide variability in response of individuals to standard doses of drug therapy. This is an important problem in clinical practice as it can lead to treatment failures or adverse drug reactions. Earlier this year, the White House said, “Most medical treatments have been designed for the ‘average patient.’ As a result of this ‘one-size-fits-all-approach,’ treatments can be very successful for some patients but not for others.” Therefore, medical advocates for pharmacogenomics/genomics currently want to better predict the patients who are most likely to respond with high risk of relapse or toxicity from standard doses of anticancer drugs. Identification of these patients early on can help design better treatment strategies to achieve optimal therapeutic outcome.
Our research group at University of Florida, recently identified an interesting single nucleotide polymorphism (SNP) in the CFLAR gene, which has significant impact on triptolide cytotoxicity. Triptolide is a biological diterpenoid derived from the Chinese herb Tripterygium wilfordii HOOK f. It has been shown to have influence on several antitumor target genes and inhibit tumors by altering multiple signaling pathways Epstein-barr virus (EBV)-transformed lymphoblastoid cell lines such as those generated by Coriell cell repositories on participants of International HapMap project have been widely used as a model for pharmacogenomics discoveries. We utilized HapMap cell lines for our study and performed a genome wide association study (GWAS) to identify predictive markers associated with triptolide cytotoxicity.
GWAS results show significant association of triptolide cytotoxicity with SNPs on chromosome 2. Mapping of these SNPs identified biologically important genes from the apoptotic pathway, such as CFLAR, PPIL3, caspase 8/10, NFkB, and STAT6. The CFLAR gene encodes for protein c-FLIP, a protein known for its antiapoptotic regulatory function. We identified that CFLAR splicing SNP rs10190751 is very significantly associated with triptolide sensitivity. Splicing SNP-rs10190751 regulates production of CFLAR- long and short isoforms, which are associated with triptolide cytotoxicity. Our results of siRNA mediated knock down and overexpression of CFLAR in pancreatic cancer cell lines further provides evidence of its involvement in chemosensitivity to triptolide. Up-regulation of CFLAR (c-FLIP) has been associated with poor clinical outcome and thus could be a reliable prognostic factor for several types of cancer. Since, the significance of CFLAR genetic variations as predictor of therapeutic efficacy has not yet been explored, our results open up opportunities for future studies.
Given the important role of CFLAR (c-FLIP) as a key inhibitor of processing and activation of caspase 8, it holds a potentially significant prognostic and therapeutic relevance in Acute Myeloid Leukemia as well as in development of cancer drug resistance. This research helps explore the clinical significance of the CFLAR gene and its genetic variations, especially the splicing of SNP (regulating CFLAR-L and CFLAR-S forms), as potential biomarkers of risk of disease as well as with the risk of chemoresistance.
This work is being presented at the 2015 AAPS Annual Meeting and Exposition this week in Orlando.