Nasopharyngeal carcinoma (NPC) is a common form of malignant cancer, for which radiotherapy or chemotherapy are the main treatment methods. Cucurbitacin E (CuE) is a natural compound-based drug which from the climbing stem of Cucumic melo L (Guadi). Previously shown to be an antifeedant as well as a potent chemopreventive agent against several types of cancer. The present study, investigated anti-proliferation and cell cycle G2/M arrest induced by CuE in Detroit 562 cells (pharynx carcinoma) and HONE-1 (nasopharyngeal carcinoma) cells. Results indicate that the cytotoxicity is associated with accumulation in G2/M cell-cycle phases. CuE produced cell cycle arrest as well as the downregulation of cyclin B1 and CDC2 expression. In addition, treated cells with CuE and GADD45γ SiRNA that also coincided with GADD45γ gene activation in cell cycle arrest. Both effects increased proportionally with the dose of CuE; however, proliferation inhibition and mitosis delay was dependant on the amount of CuE treatment in the cancer cells.