Summary Since proteolysis of the dermal collagenous matrix and basement membranes is required for local invasive growth and early metastasis formation of cutaneous melanomas, we have analysed the activities/expression levels of certain metalloproteinases in melanomas and cultured melanoma cells by in situ hybridization and Northern analysis. In addition to collagenases-1 and -3 that have been implicated in invasive growth behaviour of various malignant tumours, we analysed the levels of 72-kDa gelatinase and its activators MT1-MMP and TIMP-2 in cultured melanoma cells. The lesions examined included three cases of lentigo maligna and 28 cases of Clark grade I-V melanomas. The premalignant as well as the grade I tumours were consistently negative for collagenase-1 and -3 and TIMP-1 and -3. The collagenases were predominantly expressed in the cancer cells of Clark grade III and IV tumours. TIMP-1 and -3 were abundantly expressed in the cancer and/or stromal cells of grade III and IV melanomas, while TIMP-2 protein was detected also in melanomas representing lower invasive potential. Northern analysis of seven melanoma cell lines showed that the expression of collagenase-1 and TIMPs-1 and -3 was associated with 72-kDa gelatinase positivity. All melanoma cell lines were positive for MTI-MMP and TIMP-2 mRNAs. Our results suggest that overexpression of collagenases-1 and -3 and TIMPs -1 and -3 is induced during melanoma progression. Expression of TIMPs may reflect host response to tumour invasion in an effort to control MMP activity and preserve extracellular matrix integrity. Keywords: MMP; cell invasion; angiogenesis; gelatinase 733British Journal of Cancer (1999) 80(5/6), 733-743 © 1999 Cancer Research Campaign Article no. bjoc.1998 Received 10 September 1998 Revised 3 December 1998 Accepted 3 December 1998Correspondence to: UK Saarialho-Kere type I, II and III collagens. Furthermore, MMP-13 is gelatinolytic and type IV collagenolytic (Knäuper et al, 1996, and MMP-1 has also some activity against full-length type IV collagen (Collier et al, 1988). Our objective was to determine the expression patterns and cellular localization of these MMPs during melanocytic tumour progression. Furthermore, as imbalance between TIMPs and MMPs is an important factor in tumour invasion, the expression levels of collagenase inhibitors TIMP-1 and -3 were also examined. Our results suggest that the induction of MMPs-1 and -13 and their tissue inhibitors is a late event in melanocytic tumour progression, and that these enzymes are involved in the regulation of melanoma invasion. MATERIALS AND METHODS Tissue specimensFormalin-fixed, paraffin-embedded specimens were obtained from the Department of Dermatopathology, Helsinki University Central Hospital, Helsinki, Finland. Invasion levels of the melanomas were determined by Clark's classification: level I with confinement of the malignant melanoma cells to the epidermis and its appendages; level II with extension to the papillary dermis so that only a few melanoma cells extended to the int...

According to available information, montelukast is metabolized by cytochrome P450 (CYP) 3A4 and 2C9. In order to study the significance of CYP2C8 in the pharmacokinetics of montelukast, 10 healthy subjects were administered gemfibrozil 600 mg or placebo twice daily for 3 days, and 10 mg montelukast on day 3, in a randomized, crossover study. Gemfibrozil increased the mean area under the plasma concentration-time curve (AUC)(0-infinity), peak plasma concentration (C(max)), and elimination half-life (t(1/2)) of montelukast 4.5-fold, 1.5-fold, and 3.0-fold, respectively (P < 0.001). After administration of gemfibrozil, the time to reach C(max) (t(max)) of the montelukast metabolite M6 was prolonged threefold (P = 0.005), its AUC(0-7) was reduced by 40% (P = 0.027), and the AUC(0-24) of the secondary metabolite M4 was reduced by >90% (P < 0.001). In human liver microsomes, gemfibrozil 1-O-beta glucuronide inhibited the formation of M6 (but not of M5) from montelukast 35-fold more potently than did gemfibrozil (half-maximal inhibitory concentration (IC(50)) 3.0 and 107 micromol/l, respectively). In conclusion, gemfibrozil markedly increases the plasma concentrations of montelukast, indicating that CYP2C8 is crucial in the elimination of montelukast.

CYP2C8 is the dominant enzyme in the biotransformation of montelukast in humans, accounting for about 80% of its metabolism. CYP3A4 only mediates the formation of the minor metabolite M5a/b, and is not important in the elimination of montelukast. Montelukast may serve as a safe and useful CYP2C8 probe drug.