Altered claudin expression is related to metastatic potential, poor prognosis, or tumor recurrence. We analyzed if the overexpression of claudin-6, claudin-7, or claudin-9 in AGS cells altered cell motility, invasiveness, or proliferation rate. Claudin-7, claudin-9, and claudin-6 enhanced their invasive potential by 3.4-fold, 1.6-fold, and 2.0-fold, respectively. Claudin-6 and claudin-9 enhanced cell migration, while the proliferation rate of claudin-6-, claudin-7-, and claudin-9-transfected cells increased by 12.7%, 9.0%, and 13.3%, respectively. Claudin-7 and claudin-9 overexpression increased claudin-1 and zonula occludens-1 levels. In summary, individual increased expression of claudin-6, claudin-7, or claudin-9 is sufficient to enhance tumorigenic properties of a gastric adenocarcinoma cell line.

Claudins are proteins that preserve cell polarity and determine the size and charge of the molecules that pass through the paracellular space in epithelial tissues. Altered claudin expression in early and late stages of several cancers has been related to increased invasiveness, metastatic potential, poor prognosis or tumor recurrence. We analyzed if claudin‐2, ‐6, ‐7 or ‐9 overexpression confered changes in cell motility, invasion and proliferation in a human gastric adenocarcinoma cell line or in a breast cancer cell line. MCF‐7 and AGS cells were transfected with these claudins and proliferation rate, Matrigel invasion and claudin‐1 expression were determined. While overexpression of claudin‐2, ‐6, ‐7 and ‐9 in AGS cells enhanced their invasive potential, in MCF‐7 cell line only claudin ‐7 and ‐9 had a similar effect. Proliferation rate of claudin‐2, ‐6, ‐7 and ‐9 transfected AGS cells increased, however claudin‐2 overexpression in MCF‐7 cells had the opposite effect. Our results show that the induced modifications in proliferation or invasive potential might be associated with changes in claudin‐1, expression.