CCD 841 CON

5-Keto PGE₂ Upregulates Expression of HO-1 in CCD 841 CoN Cells

Prostaglandin E₂ (PGE₂) overproduction caused by COX-2 overexpression is characteristic of inflammatory bowel disease (IBD) and inflammation-associated cancer. 15-hydroxyprostaglandin dehydrogenase (15-PGDH) inactivates PGE₂ to 15-keto PGE₂, and 15-PGDH is a tumor suppressor. In this study, Lee et al. used human colon epithelial CCD 841 CoN cells to determine whether 15-keto PGE₂ activated Nrf2 signaling, leading to HO-1 expression.

They determined the non-cytotoxic concentrations of 15-keto-PGE₂ (20 μM and 40 μM) in human colon epithelial CCD 841 CoN cells by MTT assay. These concentrations were not cytotoxic up to 24 h. They found that 15-keto-PGE₂ (40 μM) induced HO-1 expression, as determined by Western blot (Fig. 1A) and immunocytochemical analysis (Fig. 1B). To check if 15-keto-PGE₂ could induce other antioxidant enzymes like TXN and NQO1, CCD 841 CoN cells were treated for 3, 6, 12, and 24 h. HO-1 mRNA and protein levels were increased at 6 h and maintained up to 12 h, and TXN and NQO1 expression was not induced (Fig. 1C and D).

Fig. 1. 15-Keto PGE₂ induced expression of HO-1 in human colon epithelial CCD 841 CoN cells (Lee J E, Zhong X C, et al., 2020).

Acrolein Activates the RAS/MAPK Signaling Pathway in CRC Tumorigenesis

Colorectal cancer (CRC) is one of the most common cancers with increasing incidence and low survival rate. Dietary habits including a high-fat diet (HFD) increase the incidence of CRC. Acrolein is a Group 2A carcinogen that is produced during food preparation and intake of HFD. Here, Tsai et al. sought to determine if acrolein plays a role in CRC tumorigenesis through the RAS-MAPK pathway.

To elucidate the oncogenic mechanisms of acrolein, researchers conducted cDNA microarray analysis in NIH/3T3 Acr-clone#4 followed by comprehensive pathway analysis (Fig. 2A). Four genes (Rnd1, Rras2, myc, and PI3Kcb) in the RAS/MAPK pathway were significantly upregulated in acrolein-transformed clone #4 (Fig. 2B). These results were confirmed by Western blot analysis (Fig. 2C). Acrolein activated the RAS/MAPK pathway and induced c-myc in NIH/3T3 cells and human colon epithelium CCD-841CoN (Fig. 2D and E). Acrolein also induced cell proliferation, colony formation, and migration in CCD-841CoN cells (Fig. 3A and D) and activated the RAS/MAPK pathway in CCD-841CoN Acr clone and human colon cancer cell lines SW480 and HCT116 (Fig. 3E). Taken together, these data demonstrate that acrolein induces oncogenic transformation through the RAS/MAPK pathway.

Pathway analysis of gene expression profiles in acrolein-transformed clones (Tsai H C, Tsou H H, et al., 2021).

Fig. 3. Acrolein induced oncogenic transformation in CCD-841CoN cells. CCD-841CoN cells were treated with acrolein (Acr, 7.5 μM) for one month and named CCD-841CoN Acr-clone#3 (Tsai H C, Tsou H H, et al., 2021).