SUBLETHAL EFFECTS OF EXPOSING THE HUMAN-MELANOMA CELL-LINE SKMEL-23 TO 532 NM LASER-LIGHT

The human melanoma cell line SKmel-23 has been used to investigate the sub-lethal damage that can occur as a result of exposing melanin cont aining cells to light (532 nm) from a frequency doubled Q-switched (Nd :YAG) laser, A dose response curve was obtained, which indicates that at energy levels of 0.6 J/cm(2) and below no effect on either the viab ility or growth rate of the cell line was observed, Above this, cells rapidly died and at an energy level of 2.0 J/cm(2), only approximately 15% of cells survived. This contrasts with the effects on the G361 me lanoma line, which contains far less melanosomes, as an LD50 for this cell line was approximately 5.5 J/cm(2). , Exposing SKmel-23 cells to 0.4 J/cm(2) of 532 nm light results in a diminution of the number of m elanosomes within cells as well as a marked decrease in melanin conten t, as determined by spectrophotometric assay and electron microscopy, Using the reverse transcriptase polymerase chain reaction technique, t he reduction in melanin content of the cells was accompanied by a sele ctive decrease in mRNA coding for tyrosinase, the first enzyme in the biosynthetic pathway for melanin, No decrease in the mRNA coding for t he GAPDH protein was observed, Our finding has implications for unders tanding the control processes that regulate the melanin content of cel ls and suggests that the model described can be used to further invest igate changes that may occur in cells as a result of their exposure to sub-lethal levels of laser light. (C) 1997 Wiley-Liss, Inc.