Modification of gene products involved in resistance to apoptosis in metastatic colon cancer cells: roles of Fas, Apaf-1, NFkappaB, IAPs, Smac/DIABLO, and AIF.
BACKGROUND
Colon cancer becomes resistant to apoptosis as it acquires metastatic potential. SW480 and SW620 colon cancer cells were established from the same patient at different stages of tumor progression. The stage III colorectal cancer cell line (SW620) is more resistant to apoptosis. In the present report, we investigated the apoptotic gene products that might account for colon cancer evasion of immune attack and chemoradioresistance-induced apoptosis.


METHODS
SW480 and SW620 cells were used for this experiment. Type 1 apoptosis was induced by CH-11. Type 2 apoptosis was induced by cisplatin and ionizing radiation. Apoptosis was determined by caspase-3 activity and terminal deoxynucleotidyl transferase mediated dUTP nick end labeling. Gene products Fas, TRAIL, c-FLIP, Bid, BAX, Bcl-2, Bcl-xL, Apaf-1, nuclear factor-kappa B, Smac/DIABLO, apoptosis inducing factor, and the inhibitors of apoptosis were investigated by immunocytochemistry and Western blot analyses.


RESULTS
SW620 cell lines were more resistant to both Type 1 and Type 2 apoptosis induced by CH-11, cisplatin, and ionizing radiation, respectively. Examination of the extrinsic pathway demonstrated Fas receptor to be down-regulated in SW620. Apaf-1 was decreased in SW620 cells; while other members of the mitochondrial pathway including Bax, Bid, Bcl-xL, and Bcl-2 demonstrated minimal alterations of protein levels in both cell lines. Survivin and XIAP protein levels were increased in SW620 cells, which correlated with nuclear expression of nuclear factor-kappa B in SW620 cells but not SW480. Mitochondrial-released factors including Smac/DIABLO and apoptosis inducing factor were increased in SW480 cells.


CONCLUSIONS
SW620 cells have acquired genetic defects both in the intrinsic and extrinsic pathways of apoptosis, which may explain in part the ability of colon cancer cells to escape the immune system and to become chemoradioresistant. These genes may be potential targets for chemoradiosensitization in advanced colorectal cancer.
Huerta
Sergio
S
Department of Gastrointestinal and Endocrine Surgery, University of Texas Southwestern Medical Center, Dallas, Texas 75216, USA. Sergio.Huerta@UTSouthwestern.edu
Heinzerling
John H
JH
Anguiano-Hernandez
Yu-Mei
YM
Huerta-Yepez
Sara
S
Lin
Jeffrey
J
Chen
David
D
Bonavida
Benjamin
B
Livingston
Edward H
EH
D000230:Adenocarcinoma / Q000473:pathology / Q000503:physiopathology; D000906:Antibodies / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D051033:Apoptosis Inducing Factor / Q000235:genetics / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D053478:Apoptosomes / Q000502:physiology; D053477:Apoptotic Protease-Activating Factor 1 / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D003110:Colonic Neoplasms / Q000473:pathology / Q000503:physiopathology; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000502:physiology*; D016328:NF-kappa B / Q000235:genetics / Q000502:physiology*; D009362:Neoplasm Metastasis / Q000503:physiopathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D053218:Receptors, Death Domain / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D019014:fas Receptor / Q000235:genetics / Q000502:physiology*
C506592:APAF1 protein, human; D000906:Antibodies; D000970:Antineoplastic Agents; D051033:Apoptosis Inducing Factor; D051017:Apoptosis Regulatory Proteins; D053478:Apoptosomes; D053477:Apoptotic Protease-Activating Factor 1; C481004:CH-11 anti-fas antibody, human; C412403:DIABLO protein, human; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D053218:Receptors, Death Domain; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D002945:Cisplatin