CDKL5 and breast cancer: Jones et al described a gene signature in which CDKL1 was downregulated in renal cell cancer, but Qin et al revealed that CDKL1 was upregulated in colorectal cancer.27, 28 Kawahara and colleagues demonstrated that CDKL5 was overexpressed in leukemia cells but not in normal T cells.29 To date, only one study performed by Li and colleagues showed the expression of CDKL2 and indicated that CDKL2 was considerably overexpressed in human breast cancer tissues and cells compared with normal breast tissues and cells.23 By contrast, our data show the loss of CDKL2 in GC.