Cutaneous leukemia inhibitory factor and its potential role in the development of skin tumors

Leukemia inhibitory factor (LIF) is a polyfunctional cytokine with a variety and a diverse range of biological activities. However, this is a reflection of the fact that the cytokine is expressed in many different tissues, has a wide target cell range, and fulfills different functions in different tissues. The purpose of this article is to examine what is known about LIF expression in the skin and to consider whether LIF plays a role in inflammatory and hyperplastic events in the skin. LIF is strongly expressed in skin tumors, and recent studies indicate that it may affect tumor growth by several different mechanisms. The biological activities of LIF relevant to carcinogenesis, its expression, and signal transduction by the LIF receptor are described. Expression of LIF in normal skin by skin tumors and its induction by ultraviolet radiation and proinflammatory stimuli are discussed, as are possible interactions between LIF, mast cells, and tumor growth. We consider what role LIF and other members of the hemopoietin family of cytokines play in healthy and diseased skin and whether LIF could play a role in hyperplastic skin disorders. LIF appears to be an important cytokine for normal keratinocyte growth and wound healing and may be involved in regulating the proliferation of skin tumors. Accordingly, LIF may be a useful target for anticancer therapy and as a growth factor for normal skin during reconstructive surgery.

Leukaemia inhibitory factor and interleukin-8 expression in nonmelanoma skin cancers

Leukaemia inhibitory factor (LIF) and interleukin (IL)-8 possess activities which may contribute to the development of carcinomas. LIF can stimulate proliferation of some tumour cell lines and IL-8 is angiogenic. Using semiquantitative reverse-transcription polymerase chain reaction (RT-PCR), we measured the expression of LIF and IL-8 mRNA in cultured normal keratinocytes (NKC) and the malignant carcinoma cells lines A431, SiHa, HeLa, and in biopsies of basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and normal skin. Protein expression for LIF was assessed by immunohistochemistry in the biopsies. LIF mRNA expression was increased significantly (P < 0.01) in all carcinoma lines, except SiHa, compared with NKC but the IL-8 mRNA expression in carcinoma cell lines was similar to that in NKC. Expression of LIF mRNA was elevated in BCC and SCC compared with normal skin, but a significant difference was observed only between SCC and normal skin (P < 0.01). Both BCC and SCC showed significantly greater expression of IL-8 compared with normal skin (P < 0.01). There was no correlation between LIF and IL-8 mRNA expression either in BCCs or in SCCs. Immunoreactivity for LIF was absent throughout BCC and SCC, however, normal epidermis surrounding the tumour stained positive, as in normal skin. These data may suggest a role for LIF and IL-8 in the development of skin carcinomas, but without co-ordinate regulation of these two cytokines in this process.