Effect of various formulations of DAS on the expression of p21/Waf1 in mouse skin tumors. Skin/tumor lysates were prepared as described in Materials and Methods and proteins samples from various groups were employed for Western blots. The level of p21/waf1 was assessed by Western blotting using anti-p21/Waf1 antibodies. To quantify equal loading, membranes were reprobed with β-actin antibody. The intensity of the bands was quantitated using Image Analysis software on an Image Gel Documentation System. Lane 1, untreated; lane 2, DMBA + Acetone; lane 3, DMBA + Cream; lane 4, DMBA + Sham-Lip; lane 5, DMBA + Sham-pH-Lip; lane 6, DMBA + Free DAS; lane 7, DMBA + Lip-DAS; lane 8, DMBA + pH-Lip-DAS and lane 9, Cream base only with no DMBA.