Complex sentence: PCA has been reported to induce apoptosis of human leukemia cells, as well as malignant HSG1 cells taken from human oral cavities, but PCA was found to have mixed effects on (TPA)-induced mouse skin tumors.
Split into simpler sentences: PCA has been shown to induce apoptosis of human leukemia cells, as well as malignant HSG1 cells taken from human oral cavities. However, PCA was found to have mixed effects on (TPA)-induced mouse skin tumors.