Down-regulated claudin-7 immunoexpression in urothelial carcinoma of the urinary bladder

Objectives: To analyse the gene-expression level of claudin-7 in urothelialcarcinoma (UC) of the urinary bladder, and its relationship with clinicopathologicalvariables.Materials and methods: This study included 68 specimens of UC of the bladder,comprising 35 with non-muscle-invasive (NMI), stage Ta–T1, and 33 with muscleinvasive(MI) tumours, T2–T4, and 26 of normal urothelium (NU). Total RNAwas extracted and 1μg was reverse transcribed using a cDNA kit. RT-PCR was conductedusing SYBR Green I dye to examine the expression levels of the target gene(claudin-7) and the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase.Using confocal-laser scanning light microscopy, immunohistochemistry (IHC) wasused to validate the RT-PCR data. The correlation between claudin-7 and the clinicopathologicalvariables was assessed.Results: Claudin-7 was down-regulated in UC samples compared to NU samples(P 0.001). NMI (Ta–T1) tumours had significantly higher claudin-7 expressionthan MI (≥pT2) tumours (P = 0.012). There was no significant difference between patients with G1-2 tumours and those with G3 tumours (P = 0.19). There was no significant difference between patients with recurrent NMI UC and those with no recurrence (P = 0.61). IHC showed a lower expression of claudin-7 in the UC sam- ples than NU samples, and in MI UC than in NMI UC. Conclusions: These results indicate that a reduced expression of claudin-7 corre lates with the invasiveness and progression of UC of the urinary bladder. Further studies are needed to validate claudin7 as a marker for UC.