Panoply™ Human CLDN6 Over-expressing Stable Cell Line

Recent studies have shown that aberrant expression of tight junction (TJ) proteins is a hallmark of various solid tumors and is considered a promising therapeutic target. Claudin-6 (CLDN6), a member of the TJ transmembrane protein family, is an ideal therapeutic target because it is not expressed in normal adult tissues. Here, researchers found that CLDN6 is highly expressed in uterine cervical adenocarcinoma (ADC), and that elevated CLDN6 expression correlates with lymph node metastasis and lymphovascular invasion, acting as an independent prognostic factor. Shotgun proteomic analysis revealed a significant increase in intercellular adhesion-related proteins and drug metabolism-related proteins (aldo-keto reductase [AKR] family proteins) in CLDN6-overexpressing cells. Furthermore, CLDN6 overexpression enhanced intercellular adhesion and reduced sensitivity to anticancer drugs such as doxorubicin, daunorubicin, and cisplatin. Taken together, these results suggest that aberrant CLDN6 expression enhances the malignant potential and drug resistance of endocervical adenocarcinoma, likely due to enhanced intercellular adhesion and drug metabolism.

Phase contrast microscopy revealed that compared with control cells, CLDN6-overexpressing cells had blurred intercellular boundaries and smoother cell sheet edges (Figure 1A). Scanning electron microscopy revealed an increase in the number of microvilli due to high CLDN6 expression (Figure 1A). In addition to morphological changes, Western blot analysis confirmed increased expression of cell adhesion-related proteins, including CLDN-1 (a TJ-associated protein), E-cadherin (a major adherens junction resident protein), integrin β4 (a focal adhesion-associated protein), and CD44, in CLDN6-overexpressing cells (Figures 1B-D). Next, the researchers investigated the effects of CLDN6 expression on TJ barrier function and cell-matrix adhesion. As expected, compared with control cells, CLDN6-overexpressing cells showed increased transepithelial electrical resistance (an indicator of paracellular ion movement), while CLDN6-overexpressing cells showed decreased paracellular permeability to fluorescein-labeled dextran (Figures 1E, F), indicating that CLDN6 overexpression enhances TJ barrier function. Furthermore, in an adhesion assay that assesses the adhesion between cells and substrates, overexpression of CLDN6 significantly increased the number of adherent cells (Figure 1G). Taken together, these results suggest that CLDN6 overexpression may promote cell adhesion by inducing cell adhesion-related proteins.

Figure 1. Overexpression of claudin-6 (CLDN6) enhances cell adhesion-associated properties of cervical adenocarcinoma cells. (Ito Y, et al., 2022)