Gene trapping identifies chloride channel 4 as a novel inducer of colon cancer cell migration, invasion and metastases.
BACKGROUND
To date, there are few reports on gene products contributing to colon cancer progression.


METHODS
We used a gene trap comprised of an enhanced retroviral mutagen (ERM) cassette that includes a tetracycline-responsive promoter upstream of a haemagglutinin (HA) tag and a splice donor site. Integration of the ERM within an endogenous gene yields a tetracycline-regulated HA-tagged transcript. We transduced RKO colon cancer cells expressing a tetracycline trans-activator-off with the ERM-encoding retrovirus and screened for enhanced migration.


RESULTS
One clone showed fivefold enhanced migration with tetracycline withdrawal. Rapid amplification of cDNA ends identified the trapped gene as the chloride channel 4 (CLCN4) exchanger. Stable expression of a CLCN4 cDNA enhanced motility, whereas cells knocked down or null for this transcript showed reduced migration/invasion. CLCN4-overexpressing RKO colon cancer cells were more resistant than controls to proton load-induced cytotoxicity, consistent with the H(+)-extruding function of this antiporter. Intra-splenic delivery of RKO-CLCN4 transfectants, but not controls, yielded liver metastases, and transcript levels were higher in colon cancer metastases to the liver when compared with primary tumours.


CONCLUSIONS
CLCN4 is a novel driver of colon cancer progression.
Ishiguro
T
T
Cancer Biology Department, MD Anderson Cancer Center, Houston, TX 77030, USA.
Avila
H
H
Lin
S-Y
SY
Nakamura
T
T
Yamamoto
M
M
Boyd
D D
DD
D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology*; D000818:Animals; D002465:Cell Movement / Q000235:genetics*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D003001:Cloning, Molecular / Q000379:methods; D003110:Colonic Neoplasms / Q000235:genetics / Q000473:pathology*; D018450:Disease Progression; D045325:HCT116 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000556:secondary; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D014183:Transplantation, Heterologous
C484312:CLCN4 protein, human; D018118:Chloride Channels