PRKCA and colon carcinoma: Similar to HPL-39 N (3), HPL-1RS36N (8) also activates PKCalpha more strongly than C6-ceramide (1), and exhibits a larger pro-apoptotic activity in Renca cells.13 Human colon carcinoma cells HT-29 are a well-established model to study ceramide-triggered effects on proliferation and induction of apoptosis.17 In human HT-29 cells, the two enantiomers of HPL-1RS36N (8)—HPL-1R36N (6) and HPL-1S36N (7)—show distinct effects on gene expression.