vo. Therefore, HIF 1, a key transcription factor with a pivotal role in tumor cell metabolism, is a promising target Histamine inhibition in the treatment of colorectal cancer. But the inhibitory effect of irinotecan itself on the accumulation of HIF 1 has been shown to be limited. In our study, SN 38, a derivative of irinotecan, was found to be able to inhibit HIF 1 accumulation, even at very low doses. The inhibitory effect of SN 38 on HIF 1 was stronger than that of irinotecan. This may result from the stronger antitumor activity of SN 38 compared to irinotecan. In addition to the inhibitory effect on HIF 1, SN 38 has antiangiogenic effects through inhibition of VEGF production and a direct effect on endothelial cells. Thus, SN 38 seems to exert at least triple effects on solid tumors: a direct cytotoxic effect on cancer cells, an inhibitory effect on HIF 1, and an antiangiogenic effect.
We conclude that SN 38 is an anticancer agent with the ability GSK256066 801312-28-7 to inhibit the accumulation of HIF 1 in colorectal cancer cells and, consequently, to actively kill these cells even under hypoxic conditions. Oxaliplatin, similar to 5 FU, was less effective against hypoxic colorectal cancer cells. In colorectal cancer, HIF 1 overexpression is associated with mortality and metastasis. Thus, targeting HIF 1 would be a very promising strategy for the treatment of colorectal cancer, especially poorly vascularized tumors and those overexpressing HIF 1. In these kind of tumors, FOLFIRI therapy could be more effective than FOLFOX, and these features should be evaluated and considered when choosing the ideal therapeutic protocol.
determined by micro BCA protein assay using bovine serum albumin as a standard. Equal protein amounts were separated by 4 12% NuPAGE, Bis Tris electrophoresis and then transferred to polyvinylidene fluoride membranes. The primary antibodies used were anti EGFR, antiphospho p44/p42 mitogen activated protein kinase, anti phospho STAT3, and anti phospho AKT all from Cell Signaling Technology. Detection was performed with goat anti rabbit horseradish peroxidase linked antibody in combination with the ECL plus detection kit. The staining intensity was determined using a FluorChem FC2 with AlphaView software and Coomassie protein staining was used as loading control as previously described. Specific expression of each protein species was calculated by dividing the immunostaining intensity with the Coomassie staining intensity.
Results The effect of cetuximab on cell growth was measured in vitro using the SRB assay. The parental S1 cell line was inhibited by cetuximab to a maximum of 20%, consistent with earlier results. The least oxaliplatin resistant cell line, S1 oxa2, displayed an equal sensitivity towards cetuximab but the other three cell lines were inhibited by up to a maximum of around 70%. The experiment was repeated three times with similar results. To investigate if the oxaliplatin resistance was coupled to increased EGFR expression, which could explain the change in cetuximab sensitivity, cell lysates were subjected to western blotting. The EGFR expression increased proportionally in relation to the level of acquired resistance to oxaliplatin, to a maximum in S1 oxa6, 3.5 times higher than the one of S1. EGFR downstream signalling was measured by western