Supplementary Figure Legends
Supplementary Figure 1: TSA induces tumor cell death dose-dependently.
B16F0 melanoma cells were treated with indicated concentrations of TSA. 36 hours later, cells were collected for the detection of cell death by PI staining.
Supplementary Figure 2: T cell infiltration within tumor was elevated by
TSA administration. Tumor sections were prepared for histological analysis of CD3 + cells (Bar = 100 μM). Values represent mean ±S.E.M.
Supplementary Figure 3: CD4 + CD62L cells are also positive for CD44.
Infiltrating lymphocytes were isolated and stained for CD3, CD4, CD62L and
CD44. CD3 + CD4 + CD62L cells were gated to determine the percentage of
CD44 positive cells.
Supplementary Figure 4: TSA increases the level of several anti-tumor cytokines in serum. Serum from DMSO group and 1 μM/kg TSA treated group was collected and the serum levels of IL-2, IFNγ, TNF-α and GM-CSF were assayed by the Luminex technology (Bio-Plex, Bio-Rad).
Supplementary Figure 5: TSA alone does not change the apoptotic status of A1.1 cells. 2.5×10 5 A1.1 T cell hybridomas were cultured in the presence

or absence of indicated concentrations of TSA. 24 hours later, cells were harvested for PI staining. The apoptotic rate of A1.1 cells was determined by the proportion of subdiploid cells.
Supplementary Figure 6: NaBu also protects T cells from AICD.
(A)
2.5×10 5 A1.1 T cell hybridomas were cultured in the presence or absence of indicated concentrations of NaBu in 24-well plates that had been previously coated with CD3 mAbs(10μg/ml). 24 hours later, cells were harvested for PI staining. The apoptotic rate of A1.1 cells was determined by the proportion of subdiploid cells. (B) The statistic result of three separate experiments was shown. (C) A1.1 cells were treated by anti-
CD3 with or without 3μM NaBu for indicated time. The percentage of apoptotic cells was assessed by PI staining.
Supplementary Figure 7: NaBu inhibits FasL expression during AICD.
AICD was induced on A1.1 cells for indicated time with or without 3μM NaBu.
Cells and supernatant were then collected at indicated time points for the detection of expression of FasL by real-time PCR on mRNA level (A), or by elisa assay on protein level (B).
Supplementary Figure 8: TSA inhibits FasL expression induced by anti-Thy-1. 2.5×10 5 A1.1 cells were treated with Thy1 antibodies (250μg/ml)

or both Thy-1 antibodies and 100nM TSA. After 24 hours, cells were harvested for the apoptotic assay (A) or the detection of FasL mRNA (B).
Supplementary Figure 9: TSA alone does not change the apoptotic status of T cell blasts. 2.5×10 5 CD4 + T cell blasts were cultured in the presence or absence of indicated concentrations of TSA. 12 hours later, cells were harvested for PI staining. The apoptotic rate of A1.1 cells was determined by the proportion of subdiploid cells.
Supplementary Figure 10: TSA shows no inhibitory effect on NFΚb signaling pathway. A1.1 cells were treated with immobilized anti-CD3 and graded concentrations of TSA. At indicated time points, total protein were extracted and the expression of p-p65, total p65 and GAPDH were analyzed by western blot.
Supplementary Figure 11: TSA also inhibit EL4 lymphoma growth dependent of FasL. EL4 lymphoma cells were administrated into C57BL/6 mice (n=5) and gld/gld mice (n=5). DMSO and 1μM/kg TSA were administrated as before. Tumors were weighed (A) and single-cell suspensions prepared from tumor tissues were counted and then analyzed for the frequency of CD4 + CD62L cells (B-C).