Indomethacin and Indomethacin‐PC inhibit the growth of colon cancer under in vitro and in vivo conditions.
Authors: Lichtenberger Lenard , Dial Elizabeth , Fang Dexing 
Published: June 2021

BackgroundNonsteroidal anti‐inflammatory drugs (NSAIDs) possess chemopreventive actions against cancer in both animal models and humans. We previously reported that aspirin and a novel aspirin derivative which is associated with phosphatidylcholine (PC) to provide protection of the GI tract against NSAID‐induced injury, are both effective cancer‐preventing agents in a rodent model of colon cancer (Cancer Prev Res 10: 142–152, 2017). Indomethacin (Indo) is highly potent NSAID that has previously been reported to have anti‐neoplastic activity in both rodents and humans (Eur J Cancer 26:811–814, 1990; Cancer Res 54: 5602–5606, 1994).AimIn this study, we performed in vitro and in vivo studies to compare the growth‐inhibitory effect of PC‐associated indomethacin (Indo‐PC) vs the unmodified NSAID on MC‐26 colon cancer cells and in a cancer cell xenograft animal model.MethodsA murine colon cancer cell line MC‐26 was used to compare the efficacy of Indo‐PC and Indo in both in vitro and in vivo systems. The MC‐26 cells were cultured in the presence and absence of the test drug formulations for 8 days with one medium change on the 4th day, at which time, the culture medium was collected and saved for prostaglandin (PGE2) assay as a measure of COX‐2 activity and on day‐8 cells were counted using the MTT assay (Cancer Chemother Pharmacol 57: 93–99, 2006). In the in vivo study, the MC‐26 cells were inoculated into splenic capsule of the syngeneic BALB/c mice. The mice were randomly distributed into three groups and intragastrically treated once daily with vehicle, Indo (2 mg/kg), or Indo‐PC (2 mg Indo + 4 mg PC/kg) for 28 days. We also had a naïve group with no cancer cell injection and no drug treatment. At the end of the study, the mice were euthanized and tissues were collected for analysis of tumor growth (spleen weight and tumor nodule), metastatic cancer cell spread (liver weight and nodule number), and possible GI injury/bleeding, as assessed by measuring hematocrit and fecal hemoglobin. Serum levels of Thromboxane B2 (TXB2) and splenic tissue PGE2 were measured as indices of COX activity.ResultsIndo and Indo‐PC significantly (p< 0.05) inhibited the colon cancer cell growth in culture with an ID50 of 20 μmol/L, and 10 μmol/L, respectively. Both Indo and Indo‐PC were potent inhibitors of PGE2 in culture medium, with Indo‐PC being somewhat more potent at the lowest dose tested (1.28 μmol/L). In vivo, treatment with Indo and Indo‐PC resulted in significant reductions (p<0.05) in splenic tumor nodules and spleen weight. Analysis of liver tissue revealed the presence of a number of metastatic tumor nodules, which tended to be reduced by treatment with Indo and Indo‐PC. Serum TXB2 showed 80–90% inhibition by both NSAID test drugs, supporting the NSAIDs' ability to inhibit prostaglandin formation. Splenic conc of PGE2 in vehicle‐treated controls were elevated over naïve controls which were significantly reduced by both test NSAIDs (~84%, P<0.05). Assessments of GI bleeding showed no differences between treatment and control groups, with hematocrit levels falling within a normal range of 0.43 to 0.47 and fecal hemoglobin also showing minimal alterations.ConclusionsIndo and Indo‐PC are highly potent and effective inhibitors of colon cancer cell growth, under both in vitro and in vivo conditions. These results support the possible use of Indo‐PC, a highly potent NSAID to block COX activity, for chemoprevention of colorectal cancer and possibly treatment.Support or Funding InformationSupported by NIH grants R03 CA171613This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.