[Topical Mitomycin C as a therapy of conjunctival tumours]. / Topisches Mitomycin C als Therapie konjunktivaler Tumore.

Surgical excision with tumour free margins is the gold standard for squamous cell and melanocytic tumours of the conjunctiva. In cases of diffuse and extensive tumours a complete surgical excision is sometimes not possible. Therefore, alternative or adjuvant therapies are required. Topical chemotherapy with mitomycin C (MMC) is increasingly finding use in clinical practice. MMC has several advantages such as good tolerability and mild side effects. Present studies have shown that mitomycin C is a good option in squamous cell neoplasia of the conjunctiva. However, further multi-centre studies and long-term follow-up are needed.The results in treating melanocytic tumours of the conjunctiva with MMC are less convincing. MMC seems to be an option for the treatment of primary acquired melanosis (PAM); but, if the tumour is suspicious for melanoma primary chemotherapy with MMC is obsolete. In these cases MMC can only be used as an adjuvant therapy, otherwise tumour control is not assured. However, prospective randomized controlled trials are necessary for a final evaluation of MMC therapy in melanocytic tumours of the conjunctiva.

Discrimination between plasma membrane and intracellular target sites of sphingosylphosphorylcholine.

On the background of the emerging concept of G protein-coupled sphingolipid receptors, Ca2+ mobilization by sphingosylphosphorylcholine (SPPC) in intact cells and SPPC-induced Ca2+ release in permeabilized cells, both occurring at similar, micromolar concentrations, were characterized and compared. In intact human embryonic kidney (HEK-293) cells, SPPC rapidly increased [Ca2+]i by mobilization of Ca2+ from thapsigargin-sensitive stores. In saponin-permeabilized HEK-293 cells, SPPC released stored Ca2+, in a manner similar to but independent of inositol 1,4,5-trisphosphate. Only the action of SPPC on intact cells, but not that in permeabilized cells, was, at least in part, sensitive to pertussis toxin. In addition and most important, Ca2+ release by SPPC in permeabilized cells was not stereoselective, whereas in intact cells only the naturally occurring D-erythro-SPPC, but not L-threo-SPPC, increased [Ca2+]i. Stereoselectivity of SPPC-induced [Ca2+]i increase was also demonstrated in bovine aortic endothelial cells. In conclusion, Ca2+ mobilization by SPPC in intact cells is independent of the previously described SPPC-gated Ca2+ channel on endoplasmic reticulum but probably mediated by a membrane sphingolipid receptor. Thus, SPPC can regulate Ca2+ homeostasis by acting apparently at two cellular targets, which exhibit clearly distinct recognition patterns.