TNF and cancer: While TNFα (5 ng ml−1) or phorbol 12-myristate 13-acetate (PMA, 1 nM) induced reactivation of HIV in 2D10 cells (Supplementary Fig. 3b)23, cancer cell exosomes failed to stimulate transactivation of the HIV genome (Supplementary Fig. 3b, c), suggesting the unidirectional exosome signaling from HIV-infected T cells to cancer cells.