Earthworm coelomic fluid (CF) is known as a rich source of various bioactive compounds with promising anticancer features. However, it has been demonstrated that CF affects functionality of both, cancer and normal cells. This non-selective activity causes a major problem for medical application of CF.

In this study, we present the anticancer activity of the active protein-carbohydrate fraction (AF) isolated from thermally treated CF of earthworm Dendrobaena veneta. The in vitro effect of the AF was examined in human colon model including normal human colon epithelium (CCD 841 CoTr) and human colon adenocarcinoma (HT-29 and LS180) cell lines. We investigated the impact of AF on cell viability neutral red and lactate dehydrogenase assays, morphology May-Grünwald-Giemsa staining assay proliferation MTT tetrazolium salt and BrdU incorporation assays as well as cell cycle progression propidium iodide/RNase staining and the activity of human 20S proteasome the hydrolysis of AMC from a Suc-LLVY-AMC peptide substrate. Additionally, the influence of AF on apoptosis was examined in HT-29 cells by Annexin V/PI, Hoechst 33342 staining and active caspase-3 assays.

Our investigation demonstrated that AF at the tested concentration range does not affect the viability and morphology of CCD 841 CoTr cells. Simultaneously, AF inhibits human 20S proteasome activity as well as significantly decreases mitochondrial metabolism, disturbs cell cycle and induces apoptosis via activation of procaspase-3 in HT-29 cancer cells. Obtained results demonstrate the antiproliferative and proapoptotic activity of AF that can be useful in developing therapeutic strategies to treat human colon cancer.