Metastasis, a multistep process including cancer cell migration and invasion, is the major cause of mortality in patients with cancer. Here, we investigated the effect of dicalcin, a Ca2+-binding protein, on the invasion and metastasis of ovarian cancer (OC) cells. Extracellularly administered dicalcin bound to the membrane of OV2944 cells, mouse OC cells, and suppressed their migration in vitro; however, cell viability or proliferation were unaffected. Repeated intraperitoneal injection of a partial peptide of dicalcin (P6) prolonged the survival, and reduced the number of microcolonies in the livers of cancer-bearing mice. P6 bound to the ganglioside GM1b in a solid-phase assay; treatment with P6 inhibited the constitutive activation of Erk1/2 in OC cells, whereas excess administration of GM1b augmented Erk activity and cancer cell migration in vitro. Thus, dicalcin, a novel suppressor of invasion and metastasis of OC cells, acts via the GM1b-Erk1/2 axis to regulate their migration.
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