Solute Carrier Family 29A1 Mediates In Vitro Resistance to Azacitidine in Acute Myeloid Leukemia Cell Lines.

Azacitidine (AZA) is commonly used hypomethylating agent for higher risk myelodysplastic syndromes and acute myeloid leukemia (AML). Although some patients achieve remission, eventually most patients fail AZA therapy. Comprehensive analysis of intracellular uptake and retention (IUR) of carbon-labeled AZA (14C-AZA), gene expression, transporter pump activity with or without inhibitors, and cytotoxicity in naïve and resistant cell lines provided insight into the mechanism of AZA resistance. AML cell lines were exposed to increasing concentrations of AZA to create resistant clones. 14C-AZA IUR was significantly lower in MOLM-13- (1.65 ± 0.08 ng vs. 5.79 ± 0.18 ng; p < 0.0001) and SKM-1- (1.10 ± 0.08 vs. 5.08 ± 0.26 ng; p < 0.0001) resistant cells compared to respective parental cells. Importantly, 14C-AZA IUR progressively reduced with downregulation of SLC29A1 expression in MOLM-13- and SKM-1-resistant cells. Furthermore, nitrobenzyl mercaptopurine riboside, an SLC29A inhibitor, reduced 14C-AZA IUR in MOLM-13 (5.79 ± 0.18 vs. 2.07 ± 0.23, p < 0.0001) and SKM-1-naive cells (5.08 ± 2.59 vs. 1.39 ± 0.19, p = 0.0002) and reduced efficacy of AZA. As the expression of cellular efflux pumps such as ABCB1 and ABCG2 did not change in AZA-resistant cells, they are unlikely contribute to AZA resistance. Therefore, the current study provides a causal link between in vitro AZA resistance and downregulation of cellular influx transporter SLC29A1.

Ovarian follicles are resistant to monocyte perturbations-implications for ovarian health with immune disruption†.

Monocytes and macrophages are the most abundant immune cell populations in the adult ovary, with well-known roles in ovulation and corpus luteum formation and regression. They are activated and proliferate in response to immune challenge and are suppressed by anti-inflammatory treatments. It is also likely they have a functional role in the healthy ovary in supporting the maturing follicle from the primordial through to the later stages; however, this role has been unexplored until now. Here, we utilized a Cx3cr1-Dtr transgenic Wistar rat model that allows a conditional depletion of circulating monocytes, to investigate their role in ovarian follicle health. Our findings show that circulating monocyte depletion leads to a significant depletion of ovarian monocytes and monocyte-derived macrophages. Depletion of monocytes was associated with a transient reduction in circulating anti-Müllerian hormone (AMH) at 5 days postdepletion. However, the 50-60% ovarian monocyte/macrophage depletion had no effect on ovarian follicle numbers, follicle atresia, or apoptosis, within 5-21 days postdepletion. These data reveal that the healthy adult ovary is remarkably resistant to perturbations of circulating and ovarian monocytes despite acute changes in AMH. These data suggest that short-term anti-inflammatory therapies that transiently impact on circulating monocytes are unlikely to disrupt ovarian follicle health, findings that have significant implications for fertility planning relative to the experience of an immune challenge or immunosuppression.