Blockade of EP4 by ASP7657 Modulates Myeloid Cell Differentiation In Vivo and Enhances the Antitumor Effect of Radiotherapy

Figure 4

Rechallenged CR mice show no tumor growth. (a) Antitumor activity of ASP7657 in a syngeneic mouse E.G7-OVA-engrafted model. On day 0, E.G7-OVA cells were inoculated ( cells per mouse) into the right flank of C57BL/6J mice, and oral administration of ASP7657 was started once per day (qd) or twice per day (bid). Significant inhibition of tumor growth was seen in all treatment groups at day 20. Data show for mice per group. , compared with the vehicle-treated group (Dunnett’s multiple comparison test). (b) Number of mice in (a) that achieved CR. E.G7-OVA tumors had regressed completely in 11 out of 50 ASP7657-treated mice by day 34, and these animals remained tumor-free for an additional 8 weeks. (c, d) The 11 CR mice from (b) were reinoculated with E.G7-OVA cells (c) into the right flank and with LL/2(LLC1) cells (d) into the left flank simultaneously at cells per mouse. Mice were observed for 19 days. No tumor growth was detected in the right flank whereas aggressive tumor growth was seen in the left flank.

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