Purpose: The in vitro and in vivo effects of pyrvinium pamoate (PP), a newly identified WNT signaling inhibitor, were evaluated against colon cancer cell lines and primary colon cancer samples.
Experimental design: Antiproliferative activity of PP and its effects on protein and RNA levels of WNT targets were evaluated on adenomatous polyposis coli (APC (mut)) and β-catenin(mut) cell lines, one WNT(wt) colon cancer cell line, as well as six primary colon cancer samples with mutant APC in vitro. In addition, the effect of PP on the growth of liver metastasis was examined.
Results: PP blocked colon cancer cell growth in vitro in a dose-dependent manner with great differences in the inhibitory concentration (IC(50)), ranging from 0.6 × 10(-6) to 65 × 10(-6) mol/L for colon cancer cells with mutations in WNT signaling. In addition, PP demonstrated a cytotoxic effect on primary colon cancer samples. A combined cytotoxic effect of PP with 5-fluorouracil (5-FU) was observed for two cell lines. PP decreased messenger RNA (mRNA) and protein levels of known WNT target genes as c-MYC and thereby led to the induction of p21. PP inhibited the migration of HCT116 colon cancer cells in vitro and decreased tumor growth in vivo after intraportal injection of HCT116 cells in nude mice.
Conclusions: PP displays promising anticancer activity against a broad panel of human colon cancer cell lines, as well as primary colon cancer samples. However, our findings do not demonstrate a predominant cytotoxic effect of PP on colon cancer cells with mutations in WNT signaling.