Despite its oncogenic activity, Tax expression is low or undetectable in tumor cells from adult T-cell leukemia.176,177,178 The current consensus is that Tax is necessary for initiating cell transformation, but in later stages, acquired genetic and epigenetic changes and alternative growth-promoting pathways replace the roles of Tax to maintain adult T-cell leukemia when Tax is no longer expressed. The gene discussed is CNTN2; the disease is T-cell leukemia.