Previous in vitro studies have demonstrated that endogenously produced human interleukin‐8 (IL‐8) can act as an important growth factor for human melanoma cells in vitro. The present study, has investigated whether IL‐8 mRNA expression in primary melanomas may be of prognostic relevance with regard to melanoma progression and metastatic spread. In order to evaluate the clinical significance of IL‐8 mRNA expression of melanoma cells in vivo, 59 melanocytic tissue specimens (37 primary melanomas and 22 melanocytic naevi) were studied using a semiquantitative in situ hybridization technique. Significant mRNA expression of IL‐8 was found in 59 per cent (22/37) of melanomas. In 19 per cent (7/37) of the malignant melanomas, additional hybridization signals were noted within keratinocytes of the overlying epidermis. In contrast, paralesional normal‐appearing epidermis and melanocytes in non‐malignant lesions (melanocytic naevi) showed no IL‐8 mRNA. Analysis of the relationship between IL‐8 expression and clinico‐histopathological features showed a significant association between IL‐8 mRNA expression and the histological melanoma subtype (IL‐8 mRNA: 14/19 in superficial spreading melanoma versus 4/12 in nodular melanoma, p< 0·05). Furthermore, IL‐8 expression in primary tumours could be correlated with the patients' clinical course, with time to progression being significantly reduced in primary tumours expressing IL‐8 in either the tumour cells or keratinocytes of the overlying epidermis. These results demonstrate for the first time that IL‐8 expression, as detected by in situ hybridization in primary tumours, may serve as a significant prognostic factor for tumour progression in human malignant melanoma. Copyright © 1999 John Wiley & Sons, Ltd.

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