β-tan and Sal A selectively inhibit the growth of JB6P+ cells. At 50–60% confluency, primary mouse keratinocytes (PMK), SP-1, PAM212, I7 (A) and JB6 P+ (B) cells were treated with the indicated β-tan or Sal A concentrations, or 0.1% ethanol as the control. Cell growth was determined at 24 h and expressed as percentage of control (Ct) treated cells using the MTT Cell Proliferation Kit, as described in Materials and Methods. Significance between neoplastic cell lines and PMKs is indicated by * at p < 0.05 or ** at p < 0.01. Results represent the mean (± SEM) of at least two independent experiments done in triplicate wells.