A novel intraperitoneal therapy for gastric cancer with DFP-10825, a unique RNAi therapeutic targeting thymidylate synthase, in a peritoneally disseminated xenograft model

Abstract

Purpose: In advanced gastric cancer, peritoneal dissemination is a life-threatening mode of metastasis. Since the treatment options with conventional chemotherapy remain limited, any novel therapeutic strategy that could control such metastasis would improve the outcome of treatment. We recently developed a unique RNA interference therapeutic regimen (DFP-10825) consisting of short hairpin RNA against thymidylate synthase (TS shRNA) and cationic liposomes. The treatment with DFP-10825 has shown remarkable antitumor activity in peritoneally disseminated human ovarian cancer-bearing mice via intraperitoneal administration. In this study, we expanded DFP-10825 to the treatment of peritoneally disseminated gastric cancer.

Methods: DFP-10825 was administered intraperitoneally into mice with intraperitoneally implanted human gastric cancer cells (MKN45 or NCI-N87). Antitumor activity and host survival benefits were monitored. Intraperitoneal distribution of fluorescence-labeled DFP-10825 was monitored in this MKN45 peritoneally disseminated mouse model.

Results: Intraperitoneal injection of DFP-10825 suppressed tumor growth in two peritoneally disseminated cancer models (MKN45 and NCI-N87) and increased the survival time of the MKN45 model without severe side effects. Throughout the treatment regimen, no significant body weight loss was associated with the administration of DFP-10825. Interestingly, after intraperitoneal injection, fluorescence-labeled DFP-10825 retained for more than 72 hours in the peritoneal cavity and selectively accumulated in disseminated tumors.

Conclusions: Intraperitoneal injection of DFP-10825 demonstrated effective antitumor activity without systemic severe adverse effects via the selective delivery of RNAi molecules into disseminated tumors in the peritoneal cavity. Our current study indicates that DFP-10825 could become an alternative option to improve the outcomes of patients with peritoneally disseminated gastric cancer.

Keywords: DFP-10825; RNAi therapeutic; S-1; gastric cancer; peritoneal dissemination; thymidylate synthase (TS).

Figure 1

Therapeutic effect of DFP‐10825 on a MKN45 peritoneally disseminated mouse model. MKN45 peritoneally disseminated model mice were intraperitoneally injected with five injections of DFP‐10825 (2.5, 5, 10, or 20 µg thymidylate synthase [TS] short hairpin RNA [shRNA]/mouse/d) twice weekly from Day 7 post‐tumor implantation. A, Survival periods for the mice were monitored daily (n = 9‐10). B, Body weight changes of the mice were monitored twice weekly. The data are represented as the mean ± SD

Figure 2

Tumor growth suppressive effect of DFP‐10825 in a MKN45 peritoneally disseminated mouse model. Luciferase‐expressing MKN45 peritoneally disseminated model mice were injected with either DFP‐10825 (20 µg/mouse/d, four doses once every 3 d, i.p.) or S‐1 (3.5 mg tegafur/kg/d, 14 doses once every day, p.o.) from Day 7 post‐tumor implantation. A, Bioluminescence of the disseminated tumors was monitored with in vivo imaging system at selected time points (Days 7, 14, 18, and 21 post‐tumor implantation). Two of 10 mice in the DFP‐10825‐treated group died accidently due to excessive anesthesia. B, Bioluminescent intensities of the disseminated tumors were calculated from the images in Figure 2A. The data are represented as the mean ± SD (n = 10, *P < .05, **P < .01 vs control, ^# P < .05 vs S‐1). C, Body weight changes of the mice were monitored at selected time points. The data are represented as the mean ± SD

Figure 3

Tumor growth suppressive effect of DFP‐10825 in a NCI‐N87 peritoneally disseminated mouse model. Luciferase‐expressing NCI‐N87 peritoneally disseminated model mice were injected with either DFP‐10825 (20 µg/mouse/d, five injections once every 3 d, i.p.) or S‐1 (3.5 mg tegafur/kg/d, 14 doses once every day, p.o.) from Day 7 post‐tumor implantation. A, Bioluminescent intensities of the disseminated tumors were calculated from the data imaged using in vivo imaging system at selected time points (Days 7, 23, 30, 37, and 45 post‐tumor implantation). The data are represented as the mean ± SD (n = 2‐3, *P < .05, **P < .01 vs control). B, Body weight change of the mice was monitored at selected time points. The data are represented as the mean ± SD

Figure 4

Biodistribution of intraperitoneally injected DFP‐10825 in a MKN45 peritoneally disseminated mouse model. MKN45 peritoneally disseminated model mice were intraperitoneally injected with free Alexa750‐labeled TS short hairpin RNA (shRNA), DFP‐10825 containing Alexa750‐labeled TS shRNA, or DFP‐10825 containing 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethylindotricarbocyanine iodide (DiR) (20 µg thymidylate synthase [TS] shRNA/mouse). A, The fluorescence of Alexa750‐labeled TS shRNA or DiR in the formulation was monitored with in vivo imaging system (IVIS) at selected time points (5, 10, and 30 min; 1, 3, 6, 12, 24, 48, and 72 h post‐injection). B, After preserving an image at 72 h post‐injection, tumors (Tu) and organs including heart (He), lung (Lu), liver (Li), spleen (Sp), and kidney (Ki) were harvested. The fluorescence of Alexa750‐labeled TS shRNA or DiR in each of the tissues was visualized with IVIS