title: A new model for raf kinase inhibitory protein induced chemotherapeutic resistance.
abstract: Therapeutic resistance remains the most challenging aspect of treating cancer. Raf kinase inhibitory protein (RKIP) emerged as a molecule capable of sensitizing cancerous cells to radio- and chemotherapy. Moreover, this small evolutionary conserved molecule, endows significant resistance to cancer therapy when its expression is reduced or lost. RKIP has been shown to inhibit the Raf-MEK-ERK, NFκB, GRK and activate the GSK3β signaling pathways. Inhibition of Raf-MEK-ERK and NFκB remains the most prominent pathways implicated in the sensitization of cells to therapeutic drugs. Our purpose was to identify a possible link between RKIP-KEAP 1-NRF2 and drug resistance. To that end, RKIP-KEAP 1 association was tested in human colorectal cancer tissues using immunohistochemistry. RKIP miRNA silencing and its inducible overexpression were employed in HEK-293 immortalized cells, HT29 and HCT116 colon cancer cell lines to further investigate our aim. We show that RKIP enhanced Kelch-like ECH-associated protein1 (KEAP 1) stability in colorectal cancer tissues and HT29 CRC cell line. RKIP silencing in immortalized HEK-293 cells (termed HEK-499) correlated significantly with KEAP 1 protein degradation and subsequent NRF2 addiction in these cells. Moreover, RKIP depletion in HEK-499, compared to control cells, bestowed resistance to supra physiological levels of H(2)O(2) and Cisplatin possibly by upregulating NF-E2-related nuclear factor 2 (NRF2) responsive genes. Similarly, we observed a direct correlation between the extent of apoptosis, after treatment with Adriamycin, and the expression levels of RKIP/KEAP 1 in HT29 but not in HCT116 CRC cells. Our data illuminate, for the first time, the NRF2-KEAP 1 pathway as a possible target for personalized therapeutic intervention in RKIP depleted cancers.
authors.affiliation: Department of Pathology, Health Sciences Center, Kuwait University, Faculty of Medicine, Safat, Kuwait. fahd@al-mulla.org
authors.forename: Fahd
authors.initials: F
authors.lastname: Al-Mulla
authors.forename: Milad S
authors.initials: MS
authors.lastname: Bitar
authors.forename: Jingwei
authors.initials: J
authors.lastname: Feng
authors.forename: Sungdae
authors.initials: S
authors.lastname: Park
authors.forename: Kam C
authors.initials: KC
authors.lastname: Yeung
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002945:Cisplatin / Q000494:pharmacology; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004317:Doxorubicin / Q000494:pharmacology; D004318:Doxycycline / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D045325:HCT116 Cells; D057809:HEK293 Cells; D019073:HT29 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D018613:Microscopy, Confocal; D008954:Models, Biological; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D049488:Phosphatidylethanolamine Binding Protein / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D059748:Proteolysis / Q000187:drug effects; D034622:RNA Interference; D008063:Thioctic Acid / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; C511482:PEBP1 protein, human; D049488:Phosphatidylethanolamine Binding Protein; D008063:Thioctic Acid; D004317:Doxorubicin; D006861:Hydrogen Peroxide; D004318:Doxycycline; D002945:Cisplatin; D000111:Acetylcysteine