[Abstract] The present invention relates to a pharmaceutical composition for cancer prevention and treatment containing the C12orf59 (chromosome 12 open reading frame 59) gene or C12orf59 protein, or else a fragment thereof, as an active ingredient, and relates to a method for screening cancer-diagnosis or cancer-treatment agent candidate substances using the same, and, more specifically, it has been confirmed that when the C12orf59 protein or a fragment thereof is over-expressed in cancer cell lines, there is a reduction in the expression of ITGA5 which is involved in cancer cell invasion and hence there is a reduction in cancer-cell invasion ability, whereas when the expression of C12orf59 genes is inhibited in cancer cell lines, there is an increase in cancer cell invasion and there is an increase in cancer-cell survivability, and various cell signal transmission pathways are activated, and it has been confirmed that the C12orf59 gene has a function as a tumour suppressor through this. Consequently, the C12orf59 gene or C12orf59 protein, or else a fragment thereof can not only be used to advantage in a pharmaceutical composition for cancer prevention and treatment but can also be used to advantage in a method for screening cancer-diagnosis or cancer-treatment agent candidate substances using the same.