It is reported that concomitant over-expression of D1 type cyclin and under-expression of tumor suppressor p21 are pre-requisite for tumor initiation, as it is evidenced that down-regulation of cyclin D1 and over-expression of p21 in xenograft model abrogate the formation of primary tumor (Dai et al., 2013). Here, CDKN1A is linked to neoplasm.