KITLG is a novel target of miR-34c that is associated with the inhibition of growth and invasion in colorectal cancer cells.

MiR-34c is considered a potent tumour suppressor because of its negative regulation of multiple target mRNAs that are critically associated with tumorigenesis and metastasis. In the present study, we demonstrated a novel target of miR-34c, KITLG, which has been implicated in colorectal cancer (CRC). First, we found a significant negative relationship between miR-34c and KITLG mRNA expression levels in CRC cell lines, including HT-29, HCT-116, SW480 and SW620 CRC cell lines. In silico analysis predicted putative binding sites for miR-34c in the 3' untranslated region (3'UTR) of KITLG mRNA. A dual-luciferase reporter assay further confirmed that KITLG is a direct target of miR-34c. Then, the cell lines were infected with lentiviruses expressing miR-34c or a miR-34c specific inhibitor. Restoration of miR-34c dramatically reduced the expression of KITLG mRNA and protein, while silencing of endogenous miR-34c increased the expression of KITLG protein. The miR-34c-mediated down-regulation of KITLG was associated with the suppression on proliferation, cellular transformation, migration and invasion of CRC cells, as well as the promotion on apoptosis. Knockdown of KITLG by its specific siRNA confirmed a critical role of KITLG down-regulation for the tumour-suppressive effects of miR-34c in CRC cells. In conclusion, our results demonstrated that miR-34c might interfere with KITLG-related CRC and could be a novel molecular target for CRC patients.

Localization and vasopressin regulation of the Na⁺-K⁺-2Cl⁻ cotransporter in the distal colonic epithelium.

AIM: To investigate whether Na(+)-K(+)-2Cl(-) cotransporter (NKCC2) is expressed in the mouse distal colonic epithelia and whether it is regulated by vasopressin in the colon. METHODS: The mRNA expression of NKCC2 in the mouse colonic mucosa was examined by reverse transcription-polymerase chain reaction. NKCC trafficking in the colon stimulated by 1-D-amino(8-D-arginine)-vasopressin (dDAVP) infusion (10 ng/mouse, intraperitoneal injection ) within 15 min, 30 min and 1h was investigated by laser confocal scanning microscopy. Total and membrane NKCC2 expression in the colonic mucosa from control and dDAVP-treated mice was detected by Western blotting. Short circuit current method was performed to determine regulation of NKCC2 by vasopressin in the colon. RESULTS: NKCC2 was predominantly located in the apical region of the surface of the distal colonic epithelia; by comparison, a large amount of NKCC1 was distributed in the basolateral membrane of the lower crypt epithelia of the mouse distal colon. Short-term treatment with dDAVP, a V2-type receptor-specific vasopressin analog, induced NKCC2 re-distribution, i.e., NKCC2 traffics to the apical membrane after dDAVP stimulation. In contrast, no obvious NKCC1 membrane translocation was observed. Western blotting results confirmed that membrane NKCC2 had significantly higher abundance in the dDAVP-treated mouse colonic mucosa relative to that in the untreated control, which is consistent with our immunostaining data. Moreover, the short-circuit current method combined with a NKCC2 inhibitor demonstrated that NKCC2 was also activated by serosal vasopressin in isolated distal colonic mucosa. CONCLUSION: Our results provide direct evidence that vasopressin also plays an important role in the colonic epithelia by stimulating NKCC2 trafficking to the apical membrane and inducing NKCC2-mediated ion transport.