MAP2K1 and fibrosarcoma: Furthermore, recent studies have shown that afadin can competitively inhibit the binding of rat sarcoma (Ras) protein to rapidly accelerated fibrosarcoma (Raf) protein, inhibiting the activation of mitogen-activated protein kinase kinase 1/2 (MEK1/2) and blocking activation of the extracellular signal-regulated kinase (ERK) signal pathway [19].