Preclinical evaluation of azathioprine plus buthionine sulfoximine in the treatment of human hepatocarcinoma and colon carcinoma

Table 1 HepG2 cells metabolic activity and caspase-3 activity

	Metabolic activity (absorbance units)	Caspase-3 activity (% of CRL)
		0 h	6 h	12 h	18 h
BSO/DMSO	0.833 ± 0.016	100.00 ± 6.62	-	-	-
BSO/AZA	0.544 ± 0.046a	-	95.87 ± 8.56	92.79 ± 6.09	-
BSO/AZA/NAC	0.933 ± 0.059	-	93.29 ± 4.03	98.87 ± 2.64	-
BSO/AZA/Z-VAD-mfk	0.680 ± 0.034a	-	94.85 ± 6.81	102.60 ± 7.30	-
TNF-α (35 pmol/L)/ActD (0.8 μmol/L)	-	-	-	-	143.00 ± 5.77b
TNF-α (700 pmol/L)/ActD (0.8 μmol/L)	-	-	-	-	141.30 ± 4.33b

Cells were treated with buthionine sulfoximine (BSO) (500 μmol/L, 24 h), or pretreated with BSO (500 μmol/L, 24 h) and then cotreated for 12 h with: (1) azathioprine (AZA) (300 μmol/L), (2) AZA (300 μmol/L) plus N-acetylcysteine (NAC) (1.5 μmol/L) or (3) AZA (300 μmol/L) plus Z-VAD-mfk (50 μmol/L). tumor necrosis factor (TNF)-α plus actinomycin D (ActD) treatment for 18 h was used as a positive control (CRL). Significant differences with respect to control [(BSO plus dimethyl sulfoxide (DMSO)] were statistically analyzed by analysis of variance.

^aP < 0.05;

^bP < 0.05.

Table 2 Summary of enzyme levels in mice

Enzyme	DMSO	BSO	AZA	BSO/AZA
AST (IU/L)	91.07 ± 8.36	62.79 ± 3.89	124.90 ± 10.56	154.30 ± 19.75a
ALT (IU/L)	31.50 ± 9.12	22.36 ± 2.85	36.17 ± 5.44	42.29 ± 9.04
CK (IU/L)	598.60 ± 112.10	416.00 ± 89.28	904.40 ± 129.40	918.50 ± 128.70

Enzyme activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatine kinase (CK) in plasma of nude mice transplanted with HepG2 cells at the end of the experiment (12 d of treatment in similar conditions as in Figure 7). Significant differences with respect to control animals [dimethyl sulfoxide (DMSO)] were statistically analyzed by analysis of variance.

^aP < 0.001. BSO: Buthionine sulfoximine; AZA: Azathioprine.