DHA Alters Expression of Target Proteins of Cancer Therapy in Chemotherapy Resistant SW620 Colon Cancer Cells

Abstract

Diets rich in n-3 polyunsaturated fatty acids (PUFAs) have been associated with a reduced risk of several types of cancer. Recent reports have suggested that these PUFAs enhance the cytotoxic effect of cancer chemoradiotherapy. The effect of docosahexaenoic acid (DHA) on key cell cycle regulators and target proteins of cancer therapy was investigated in the human malign colon cancer cell line SW620. Cell cycle check point proteins such as p21 and stratifin (14-3-3 sigma) increased at mRNA and protein level, whereas cell cycle progression proteins such as cell division cycle 25 homolog and cyclin-dependent kinase 1 decreased after DHA treatment. Protein levels of inhibitors of apoptosis family members associated with chemotherapy resistance and cancer malignancy, survivin and livin, decreased after the same treatment: likewise the expression of NF-κB. Levels of the proapoptotic proteins phosphorylated p38 MAPK and growth arrest-inducible and DNA damage-inducible gene 153/C/EBP-homologous protein (CHOP) increased. The results indicate that DHA treatment causes simultaneous cell cycle arrest in both the G1 and G2 phase. In conclusion, DHA affects several target proteins of chemotherapy in a favorable way. This may explain the observed enhanced chemosensitivity in cancer cells supplemented with n-3 PUFAs and encourage further studies investigating the role of n-3 PUFAs as adjuvant to chemotherapy and radiotherapy in vivo.

ACKNOWLEDGMENTS

The study was carried out at the Department of Laboratory Medicine, Children's and Women's Health at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. Jens E. Slagsvold and Caroline H. H. Pettersen have contributed equally to this work. The project was financed by The Faculty of Medicine, NTNU, The Cancer Research Fund, St Olavs Hospital, and The Research Council of Norway through grants from the Functional Genomics Program (FUGE). Microarray experiments were performed at the microarray core facility at the Norwegian Microarray Consortium (NMC), Trondheim, which is supported by FUGE, The Research Council of Norway. Financial support was also given by the cross-disciplinary project “BIOEMIT-Prediction and modification in functional genomics: combining bioinformatical, bioethical, biomedical and biotechnological research,” NTNU.