However, one common feature of both glioblastoma and pancreatic cancer sellekchem is the involvement of myeloid cells �C. We hoped to determine whether PKRA7 could have an impact on tumor growth through its inhibitory effect on myeloid cells. Consistent with this postulation, our results clearly demonstrate that PKRA7 possesses a strong anti-tumor activity for both types of cancers, although through different mechanisms. Furthermore, our study indicates that PKRA7 has the potential to become one component of combination therapies with standard care currently used in the clinic and this compound holds promise for further development for treatment of those cancers that currently have very poor prognosis.
Results PKRA7 Suppresses Tumor Growth in Nude (nu/nu) Mouse Xenograft Model of Glioblastoma through Inhibition of Angiogenesis Although an anti-PK2 neutralizing antibody was found by previous studies to display anti-tumor activity, we explored the possibility that small molecules can be developed to achieve the same anti-tumor efficacy with lower costs and easier delivery. After biochemically defining the molecular nature of interactions between PK2 and its receptors , we have determined the hexapeptide amino acid sequence AVTIGA in the N-terminus of PK2 is completely conversed among mammalian and non-mammalian species and is critical for activating PKR1 and PKR2 . Mutations in this region including an A1M (alanine to methionine) substitution or addition of methionine to the N-terminus displayed strong antagonist activity in the presence of both PKR1 and PKR2 stably expressed on Chinese hamster ovary (CHO) cells .
Following this initial discovery, we have synthesized over 200 small molecule compounds that structurally mimic the PK2 N-terminal region mutant peptides and tested their ability to competitively inhibit the activation of PK2 receptors. From this initial screen, we found over 60 water-soluble compounds that exhibit inhibitory effect on PK2-receptor interaction with binding constant below 20 nM (Zhou, manuscript in preparation). We have chosen compound PKRA7 for our experiments because it could potently inhibit PK2 receptors, with IC50 values of 5.0 and 8.2 nM for PKR1 and PKR2, respectively (Figure S1), and, more importantly, it could penetrate the blood-brain barrier, a feature that could be critical for the treatment of glioblastoma. To study the in vivo effect of PKRA7 on glioblastoma tumor growth, we first generated subcutaneous human glioblastoma tumor xenografts in nude mice. 5��104 D456MG glioma cells were implanted into ten nude mice subcutaneously and the mice were separated AV-951 into two treatment groups 14 days after implantation.