Abstract
Abstract
Background: Vitamin D3 (VD) and its analogue, Paricalcitol (Pcal), have previously shown anti-tumorigenic activities against colorectal cancer (CRC). Hence, this study compared the therapeutic efficacy of both VD types with or without chemotherapy (5-FU) in azoxymethane (AOM)-induced CRC in rat.
Methods: seventy male Wistar rats were equally allocated into 7 groups: Control, AOM, VD, Pcal, 5-FU, 5-FU/VD and 5-FU/Pcal. AOM was subcutaneously injected for 2 weeks (15mg/kg/week). The study duration was 25 weeks. VD (500 IU/rat/day; 3 days/week) and Pcal (2.5 μg/kg/day; 3 days/week) were injected subcutaneously from week-15 till the end of the study. 5-FU intraperitoneal injections started in week-21 (12 mg/kg/day; 4 successive days) and continued in week-22 (6 mg/kg/4 doses every other day). The colons were collected for gross and histopathological examination. The expression of VD signalling system, Wnt, β-catenin, NF-κB, COX-2, iNOS, VEGF, smad4, p21 and p27 proteins was measured by immune-histochemistry/fluorescence. The mRNA expression of Wnt, β-catenin, DKK-1 and COX-2 genes was measured by Quantitative RT-PCR. ELISA was used to measure the concentrations of TGF-β1, VEGF and COX-2 proteins in tissues.
Results: The AOM and 5-FU groups showed marked inhibitions in the VD receptor and binding protein compared with controls (P < 0.05). VD and Pcal monotherapies significantly increased the expression of the VD molecules and the VD group showed the utmost elevations. Moreover, the tumour numbers and sizes were equally and significantly reduced in the 5-FU, VD and Pcal groups compared with the AOM group (P < 0.05). Interestingly, the 5-FU/VD and 5-FU/Pcal resulted in significantly lower numbers of tumours compared with the remaining study groups and the highest significant reduction was observed in the former group. At the molecular level, the 5-FU/VD markedly inhibited the pro-oncogenic molecules (Wnt, β-catenin, NF-κB, COX-2, iNOS & VEGF) as well as significantly upregulated the anti-tumorigenic molecules (DKK-1, TGF-β1, smad4, p21 and p27) compared with the other study groups (P < 0.05).
Conclusions: Vitamin D3 showed a better synergism than Pcal with 5-FU. The enhanced anti-tumorigenic actions of 5-FU/VD involved the modulation of the Wnt/β-catenin and TGF-β1/smad4 pathways, angiogenesis and cell cycle arrest. Further studies are required to elucidate the therapeutic significance of VD in clinical settings
Citation Format: Mohammed Abbas Baghdadi, Mohammed Aslam, Jawwad Ahmad, Shakir Idris, Bassem Refaat. A comparative study between the therapeutic efficacy of vitamin D3 and its analogue, paricalcitol, in the treatment of colon cancer in rat [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2976.