Non-Hodgkin's lymphoma (NHL) has a wide biological heterogeneity and shows extremely variable responses to therapeutic measures. However, markers that indicate disease activity and determine treatment strategies for this malignancy are little recognized. Using the differential display method, we have identified Aurora2/BTAK/STK15, a centrosome-associated serine/threonine kinase, whose overexpression leads to centrosome amplification, chromosomal instability and transformation of mammalian solid tumours. Northern analysis with mRNA from a single tumour cell suspension of NHL confirmed that Aurora2/BTAK/STK15 was highly expressed in histologically aggressive types. To elucidate the function of Aurora2/BTAK/STK15 in NHL, Aurora2/BTAK/STK15 sense or antisense genes were transfected to B-cell lymphoma cell lines to generate overexpressed or under-regulated tumour cells. Aurora2/BTAK/STK15 antisense transfectant was barely established compared with a sense or vector-only transfectant. Two clones were finally established that exhibited a low proliferation rate and significantly increased G1 arrest compared with vector-only transfectants. Moreover, antisense oligo treatment in vitro showed that restriction of cell growth appeared in proportion to antisense oligo concentration. These results suggest that Aurora2/BTAK/STK15 is an effective candidate to indicate not only disease activity but also tumorigenesis of non-Hodgkin's lymphoma. Retardation of tumour cell growth resulting from the restriction of this gene's functions may be a novel therapeutic approach for non-Hodgkin's lymphoma.