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Selective Reduction in α‐Hydroxypalmitic Acid‐containing Sphingomyelin and Concurrent Increase in Hydroxylated Ceramides in Murine Skin Tumors Induced by an Initiation‐promotion Regimen

The sphingomyelin cycle is activated to accumulate ceramides in the process of epidermal differentiation. We found that sphingomyelin in the epidermis of 4 different murine strains gave three bands on TLC, the lower band containing α‐hydroxypalmitic acid (C16h:0(α)). However, in the papillomas induced in the skin of SENCAR and SSIN mice by initiation with 7,12‐dimethylbenz[α] anthracene followed by promotion with 12‐O‐tetradecanoylphorbol acetate, the concentration of C16h:0(α)‐ containing sphingomyelin was selectively diminished with a concomitant increase in the concentrations of the ceramides containing α‐hydroxy fatty acids. These findings indicate a possible involvement of the selective hydrolysis of α‐hydroxy fatty acid‐containing sphingomyelin in the process of tumorigenesis in mouse skin.