TNFRSF9 and neoplasm: According to our previously published data14, 22, the presence of the additional T-cell co-stimulatory molecule 4-1BBL (CD137L) resulted in an amplification of the T-cell-mediated tumor cell killing via the 4-1BB/4-1BBL signaling pathway in comparison to the stimulus provided by the CD33-CD3 bsAb alone.