SMN1 and cancer: However, the expression level of intrinsic apoptosis-related transcripts (BAX, caspase 3 and caspase 9) was significantly (P < .05) increased, and the expression level of stress-related transcripts (p21, HSP70 and HSP90) was also significantly (P < .05) increased in the A-549, MDA-MB-231 and U87-MG cancer cells treated with 1 μM SMA for up to 2 weeks.