Functional Genetic Polymorphisms in the Aromatase Gene CYP19 Vary the Response of Breast Cancer Patients to Neoadjuvant Therapy with Aromatase Inhibitors

Aromatase (CYP19) is a critical enzyme for estrogen biosynthesis, and aromatase inhibitors (AIs) are established endocrine therapy for post-menopausal women with breast cancer. DNA samples were obtained from 52 women pre- and post-AI treatment in the neoadjuvant setting. 82 breast cancer and 19 normal breast samples were resequenced to test the hypothesis that single nucleotide polymorphisms (SNPs) in the CYP19 gene might contribute to response to neoadjuvant AI therapy. There were no differences in CYP19 sequence between tumor and germline DNA in the same patient. Forty-eight CYP19 SNPs were identified, with four being novel when compared with previous resequencing data. Genotype-phenotype association studies performed with levels of aromatase activity, estrone, estradiol and tumor size pre- and post-AI treatment indicated that two tightly linked SNPs, rs6493497 and rs7176005 in the 5’-flanking region of CYP19 exon 1.1, were significantly associated with a greater change in aromatase activity after AI treatment. A follow-up study in 200 women with early breast cancer treated with adjuvant anastrozole showed that these same two SNPs were also associated with higher plasma estradiol levels pre- and post-AI treatment. Electrophoretic mobility shift and reporter gene assays confirmed the potential functional effects of these two SNPs on transcription regulation. These studies provide insight into the role of common genetic polymorphisms in CYP19 in variation in response to AIs by breast cancer patients

Glutathione Stransferase omega 1 and omega 2 pharmacogenomics. Drug Metab Dispos

ABSTRACT Glutathione S-transferase omega 1 and omega 2 (GSTO1 and GSTO2) catalyze monomethyl arsenate reduction, the rate-limiting reaction in arsenic biotransformation. As a step toward pharmacogenomic studies of these phase II enzymes, we resequenced human GSTO1 and GSTO2 using DNA samples from four ethnic groups. We identified 31 and 66 polymorphisms in GSTO1 and GSTO2, respectively, with 4 nonsynonymous coding single nucleotide polymorphisms (cSNPs) in each gene. There were striking variations among ethnic groups in polymorphism frequencies and types. Expression constructs were created for all eight nonsynonymous cSNPs as well as a deletion of codon 155 in GSTO1, and those constructs were used to transfect COS-1 cells. Quantitative Western blot analysis, after correction for transfection efficiency, showed a reduction in protein level of greater than 50% for the GSTO1 Tyr32 variant allozyme when compared with wild type (WT), while levels for the Asp140, Lys208, Val236 and codon 155 deletion variant constructs were similar to that of the WT. For GSTO2, the Tyr130 and Ile158 variant allozymes showed 50% and 84% reductions in levels of expression, respectively, when compared to WT, while the Ile41 and Asp142 allozymes displayed levels similar to that of WT GSTO2. Rabbit reticulocyte lysate (RRL) degradation studies showed that the GSTO1 Tyr32 and the GSTO2 Tyr130, Ile158 and Asp142/Ile158 variant allozymes were degraded more rapidly than were their respective WT allozymes. These observations raise the possibility of functionally significant pharmacogenomic variation in the expression and function of GSTO1 and GSTO2

Cytosolic 5 '-nucleotidase III (NT5C3): gene sequence variation and functional genomics

Background 5'-Nucleotidases play a critical role in nucleotide pool balance and in the metabolism of nucleoside analogs such as gemcitabine and cytosine arabinoside (AraC). We previously performed an expression array association study with gemcitabine and AraC cytotoxicity using 197 human lymphoblastoid cell lines. One gene that was significantly associated with gemcitabine cytotoxicity was a nucleotidase family member, NT5C3. Very little is known with regard to the pharmacogenomics of this family of enzymes