Correlations between claudin-1 and PIGF expressions in retinoblastoma

To investigate the expressions of claudin-1 and placental growth factor (PlGF) proteins in retinoblastoma (RB) and their relationships with the differentiation of RB, the infiltration of optic nerve and choroid and clinical stages.

Immunohistochemical (IHC) method was used to detect the expressions of claudin-1 and PlGF proteins in 56 cases of RB paraffin-embedded tissue samples. The x2-test and Fisher exact test were used to compare the qualitative variables. The Pearson correlation coefficient was used to detect the correlation of the expression of claudin-1 with that of PlGF in RB tissues.

1) Among RB tissues, the positive expression rates of claudin-1 in clinical stage I tumors and clinical stage III tumors were 69.2% and 38.9%, respectively, and claudin-1 was not expressed in all clinical stage II tumors (p=0.002). In case of optic nerve invasion, the lowly positive expression of claudin-1 was detected, and the difference was significant (p=0.001). 2) The positive expression rate of PlGF proteins in RB was 73.8%, which was higher in tumors with optic nerve invasion than in tumors without the invasion; the expression was significantly different (p=0.001). In addition, the positive expression rate of PlGF in tumors with choroidal invasion was 74.1%. 3) The expression of claudin-1 in RB was negatively correlated with the presence of choroidal invasion (r=0.52, p≤0.0001) and optic nerve infiltration (r=0.49, p=0.0003). There was a significant positive correlation between the expression of PlGF and the presence of optic nerve invasion (r=0.30, p=0.009). In addition, there was a significant positive correlation between the expression of claudin-1 and that of PlGF (r=0.41, p=0.006).

The expression level of claudin-1 is negatively correlated with the differentiation of RB cells, optic nerve infiltration and clinical stages, while the expression of PlGF was positively correlated with the optic nerve infiltration and clinical stages of RB. The role of claudin-1 may be opposite to that of matrix metalloproteinase-2 (MMP-2) in the development of RB.