A fusion protein or a gene encoding the same comprising a specific region of p120(p120 catenin) capable of being bound to an activated ARF6(ADP-ribosylation factor 6) is provided to overcome weakening of cellular adhesion and increase of intercellular permeability, thereby being used for preventing and treating cancer diseases and immune diseases related to angiogenesis and transition of tumor cells. A pharmaceutical composition for preventing and treating cancer diseases or immune diseases comprises a fusion protein including a specific region of p120 or a gene encoding the same, wherein the specific region of the p120 is an amino acid of SEQ ID : NO. 23 or a DNA sequence of SEQ ID : NO. 24, the fusion protein is selected from the group consisting of amino acid sequences of SEQ ID : NOs. 3 to 12, and the gene encoding the fusion protein is selected from the group consisting of DNA sequences of SEQ ID : NOs. 13 to 22. To decrease cellular adhesion weakening and intercellular permeability increasing or to inhibit angiogenesis of tumor, the fusion protein or the gene encoding the same are administered to be bound to an activated ARF6. A method for screening a low molecular compound inhibiting binding between the p120 and the ARF6 comprises the steps of: (a) binding the fusion protein to the activated ARF6； (b) mixing a reaction material obtained from the step(a) with a candidate material and a fluorescence-labeled trace to allow them to react； and (c) measuring fluorescence polarization of a reaction material obtained from the step(b). 본 발명은 p120 (p120 catenin)의 특정 부분을 포함하는 단백질 또는 이를 코딩하는 유전자를 함유하는 조성물에 관한 것으로서, 상세하게는 본 발명은 활성화된 ARF6 (ADP-ribosylation factor 6)과 결합 가능한 p120의 특정부분을 포함하는 융합단백질 또는 이를 코딩하는 유전자를 유효성분으로 함유하는 염증 및 종양을 억제하기 위한 약학 조성물에 관한 것으로, 본 발명의 약학 조성물은 암 질환 또는 면역질환의 예방 및 치료에 유용하게 이용될 수 있다.
