Based on the results of tumor size from the subcutaneous dissection of mice (Figs. 7A–7X), after multiple administrations of 5-FU, the tumor volume inoculated with multidrug-resistant SGC7901/DDP cells with higher expression levels of ARK5 gene was significantly larger than that of SGC7901 cells (Figs. 5A, 5B). Here, NUAK1 is linked to neoplasm.