We speculate that the up-regulation of claudin-6 plays a role in ovarian cancer carcinogenesis and metastasis by influencing structure and function of TJs or promoting the activation of MMP-2 that degrades the extracellular matrix, and can be used as an index for the prognostic assessment of ovarian cancer carcinogenesis and metastasis. The gene discussed is MMP2; the disease is ovarian cancer.