Streptozocin is a potent DNA-methylating antibiotic. Streptozotocin causes methylation of liver and kidney and pancreatic DNA, but no methylation in brain DNA.

Streptozocin (STZ) shows higher cytotoxic effect in vitro on hematological cell lines compared to Alloxan (ALX). ALX appeares not to be toxic for the studied cell lines with estimated IC50 values of 2809, 3679 or over 4000 μg/mL for HL60, K562 and C1498 cells, respectively. Streptozocin is more toxic, especially for the human myeloid leukemia cell line, HL60. The IC50 values of Streptozocin are 11.7, 904 and 1024 μg/mL for HL60, K562 and C1498 cells, respectively. Results also show that the murine leukemic cells are more resistant to Streptozocin and ALX cytotoxicity than human leukemic cells[2].

Streptozocin (STZ)-injected mice show tendency to have lower body weight than that observed in animals injected with ALX. Streptozocin -injected mice have significantly fewer splenocytes (22.2±3.2×106; n=10) compared to mice injected with ALX (60.7±4.3×106; n=15; p=0.01)[2].