Chronic oxaliplatin resistance induces epithelial-to-mesenchymal transition in colorectal cancer cell lines.
OBJECTIVE
Epithelial-to-mesenchymal transition (EMT) is a process whereby cells acquire molecular alterations that facilitate cell motility and invasion. In preliminary studies, we observed that oxaliplatin-resistant (OxR) colorectal cancer (CRC) cells underwent morphologic changes suggestive of a migratory phenotype, leading us to hypothesize that OxR CRC cells undergo EMT.


METHODS
The human CRC cell lines KM12L4 and HT29 were exposed to increasing doses of oxaliplatin to establish stable cell lines resistant to oxaliplatin. Migration and invasion were assessed by modified Boyden chamber assays. Morphologic and molecular changes characteristic of EMT were determined by immunofluorescence staining and Western blot analyses.


RESULTS
The OxR cells showed phenotypic changes consistent with EMT: spindle-cell shape, loss of polarity, intercellular separation, and pseudopodia formation. KM12L4 and HT29 OxR cells exhibited an approximately 8- to 15-fold increase in migrating and invading cells, respectively (P < 0.005 for both). Immunofluorescence staining of OxR cells revealed translocation of E-cadherin and beta-catenin from their usual membrane-bound complex to the cytoplasm and nucleus, respectively. The OxR cells also had decreased expression of the epithelial adhesion molecules E-cadherin and plakoglobin and an increase in the mesenchymal marker vimentin. The KM12L4 OxR cells exhibited increased nuclear expression of Snail, an EMT-regulatory transcription factor, whereas the HT29 OxR cells exhibited an increase in nuclear expression of the EMT-associated transcription factor nuclear factor kappaB.


CONCLUSIONS
We hypothesize that induction of EMT may contribute to the decreased efficacy of therapy in chemoresistant CRC, as the tumor cells switch from a proliferative to invasive phenotype. Further understanding of the mechanisms of chemoresistance in CRC will enable improvements in chemotherapy for metastatic disease.
Yang
Anthony D
AD
Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77230-1402, USA.
Fan
Fan
F
Camp
E Ramsay
ER
van Buren
George
G
Liu
Wenbiao
W
Somcio
Ray
R
Gray
Michael J
MJ
Cheng
Haiyun
H
Hoff
Paulo M
PM
Ellis
Lee M
LM
D000970:Antineoplastic Agents / Q000494:pharmacology*; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D019008:Drug Resistance, Neoplasm; D004848:Epithelium / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008648:Mesoderm / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D008941:Spindle Apparatus
D000970:Antineoplastic Agents; D015820:Cadherins; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin