Zhang, Wenjuan

Abstract Background Most oncology therapeutics have limited distribution into the brain, and developing strategies to overcome this limitation would be clinically impactful. While therapeutic radiation is often cited as a strategy to accomplish this, there are no published studies demonstrating the effect of radiation on drug distribution into the brain or brain tumors. Methods Mice were treated with brain radiation (6 Gy × 5, 4 Gy × 10; 40 Gy × 1) and dosed with drugs (levetiracetam, cefazolin, nedisertib, brigimadlin, apitolisib, or GNE-317) at times ranging from just prior to months after radiation. Plasma and tissue drug concentrations were measured by LC-MS/MS. Results Radiation did not significantly enhance drug delivery into brain tissue for levetiracetam, cefazolin, GNE-317, apitolisib, or nedisertib at any time post-radiation. Even a single, supra-therapeutic dose of radiation (40 Gy) did not significantly affect brain distribution of GNE-317 or apitolisib (P ≥ .07) from 16 to 160 hours post-radiation. For brigimadlin, radiation (6 Gy × 5) was associated with a modest but significant increase in drug accumulation only at 72 hours post-radiation (brain-to-plasma ratio 0.014 ± 0.006 vs. 0.025 ± 0.010, respectively; P = .04), but not at any other timepoint (24 hours, 15, 28, 94, 133, 183 days; P > .05). Similarly, radiation (6 Gy × 5) of orthotopic tumors did not increase levels of brigimadlin in GBM10 or GBM108 or nedisertib in GBM108 (P > .05). Conclusions Radiation had no meaningful impact on drug delivery into brain or brain tumors for the drugs tested.

GH is an important regulator of body growth and composition as well as numerous other metabolic processes. In particular, liver plays a key role in the GH/IGF-I axis, because the majority of circulating “endocrine” IGF-I results from GH-stimulated liver IGF-I production. To develop a better understanding of the role of liver in the overall function of GH, we generated a strain of mice with liver-specific GH receptor (GHR) gene knockout (LiGHRKO mice). LiGHRKO mice had a 90% decrease in circulating IGF-I levels, a 300% increase in circulating GH, and significant changes in IGF binding protein (IGFBP)-1, IGFBP-2, IGFBP-3, IGFBP-5, and IGFBP-7. LiGHRKO mice were smaller than controls, with body length and body weight being significantly decreased in both sexes. Analysis of body composition over time revealed a pattern similar to those found in GH transgenic mice; that is, LiGHRKO mice had a higher percentage of body fat at early ages followed by lower percentage of body fat in adulthood. Local IGF-I mRNA levels were significantly increased in skeletal muscle and select adipose tissue depots. Grip strength was increased in LiGHRKO mice. Finally, circulating levels of leptin, resistin, and adiponectin were increased in LiGHRKO mice. In conclusion, LiGHRKO mice are smaller despite increased local mRNA expression of IGF-I in several tissues, suggesting that liver-derived IGF-I is indeed important for normal body growth. Furthermore, our data suggest that novel GH-dependent cross talk between liver and adipose is important for regulation of adipokines in vivo.