Thiopurine methyltransferase (TPMT) activity exhibits a monogenic codominant inheritance and catabolizes thiopurines. TPMT variant alleles are associated with low enzyme activity and pronounced pharmacologic effects of thiopurines. Loss‐of‐function alleles in the NUDT15 gene are common in Asians and Hispanics and reduce the degradation of active thiopurine nucleotide metabolites, also predisposing to myelosuppression. We provide recommendations for adjusting starting doses of azathioprine, mercaptopurine, and thioguanine based on TPMT and NUDT15 genotypes (updates on http://www.cpicpgx.org).

Estrogen receptor α (ERα) plays an important role in breast cancer. Upregulation of HIF-1α in ERα-positive cancers suggests that HIF-1α may cooperate with ERα to promote breast cancer progression and consequently affect breast cancer treatment. Here, we show the histone demethylase JMJD2B is regulated by both ERα and HIF-1α, drives breast cancer cell proliferation in normoxia and hypoxia, and epigenetically regulates the expression of cell cycle genes such as CCND1, CCNA1, and WEE1. We also show that JMJD2B and the hypoxia marker CA9 together stratify a subclass of breast cancer patients and predict a worse outcome of these breast cancers. Our findings provide a biological rationale to support the therapeutic targeting of histone demethylases in breast cancer patients. Cancer Res; 70(16); 6456-66. ©2010 AACR.