CLDN6 inhibits colorectal cancer proliferation dependent on restraining p53 ubiquitination via ZO-1/PTEN axis

The Expression of the Claudin Family of Proteins in Colorectal Cancer

“…However, Dong et al reported a reduction in CLDN6 RNA levels in CRC samples. They also compared ten paired samples of CRC and the normal colon by western blotting and found that four had large reductions in CLDN6, while the remaining six had either a minimal change or a slight increase in CLDN6 compared to the normal colon [ 105 ].…”

“…By western blotting, HCT116 had low CLDN6 expression, while SW1116 had high CLDN6 expression [ 105 , 106 ].…”

“…Of the CRCs that expressed CLDN6, 75% (n = 28) had lymph node metastases, while only 46.8% (n = 79) of those negative for CLDN6 had nodal disease [ 106 ]. However, Dong et al reported that higher levels of CLND6 were associated with improved disease-free survival, with a 5-year survival of ~81% for those with high CLDN6 expression compared to ~60% for those with low levels of expression [ 105 ]. …”

“…Yet, there are still conflicting reports if some claudins are even expressed in normal colonic tissue, such as CLDN2, or in malignancy, such as CLDN3 [ 35 , 73 , 74 , 75 , 76 ]. There are also discordant findings regarding RNA expression and protein production in some cases, such as CLDN6 [ 39 , 105 ].…”

“…Based on the currently available body of work on the protein expression of claudins in colorectal cancer, CLDN1, CLDN2, CLDN4, and CLDN18 have all been reported to be expressed in CRC [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 37 , 46 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 73 , 74 , 75 , 80 , 81 , 93 , 96 , 152 , 153 , 160 , 161 , 162 , 163 , 164 ]. Although CLDN6 and CLDN7 are expressed in CRC, their levels are reduced compared to the normal colon [ 44 , 62 , 105 , 106 , 119 , 122 , 124 , 125 ]. The remainder of the claudin proteins have yet to be investigated in CRC at the protein level or have conflicting reports at present.…”