I. Kempen

3-Bromophenyl 6-acetoxymethyl-2-oxo-2H-1-benzopyran-3-carboxylate inhibits cancer cell invasion in vitro and tumour growth in vivo.

In search for new anticancer agents, we have evaluated the antiinvasive and antimigrative properties of recently developed synthetic coumarin derivatives among which two compounds revealed important activity: 3-chlorophenyl 6-acetoxymethyl-2-oxo-2H-1-benzopyran-3-carboxylate and 3-bromophenyl 6-acetoxymethyl-2-oxo-2H-1-benzopyran-3-carboxylate. Both drugs were able to inhibit cell invasion markedly in a Boyden chamber assay, the bromo derivative being more potent than the reference matrix metalloprotease (MMP) inhibitor GI 129471. In vivo, tumour growth was reduced when nude mice grafted with HT1080 or MDA-MB231 cells were treated i.p. 3 days week−1 with the bromo coumarin derivative. These effects were not associated with the inhibition of urokinase, plasmin, MMP-2 or MMP-9. The mechanism of action of the drugs remains to be elucidated. However, these two coumarin derivatives may serve as new lead compounds of an original class of antitumour agents.

6-Substituted 2-oxo-2H-1-benzopyran-3-carboxylic acid derivatives in a new approach of the treatment of cancer cell invasion and metastasis

Novel 6-substituted 2-oxo-2H-1-benzopyran-3-carboxylic acid derivatives were synthesized and their potency in reducing the invasive behaviour of HT 1080 fibrosarcoma cells was evaluated. Structure-activity relationships were deduced from biological results and will be used in further design of new active compounds. In particular, the acetoxymethyl substituent found at the 6-position of previously described active compounds can be replaced by an acetamidomethyl substituent without loss of potency; while the presence of an aryl ester function at the 3-position was preferred to a thioester or an amide function to induce marked biological activity. This work confirms the interest of aryl esters of 6-substituted coumarin-3-carboxylic acids as potential new anti-cancer agents.

Toward the First Class of Suicide Inhibitors of Kallikreins Involved in Skin Diseases

The inhibition of kallikreins 5 and 7, and possibly kallikrein 14 and matriptase, (that initiates the kallikrein proteolytic cascade) constitutes an innovative way to treat some skin diseases such as Netherton syndrome. We present here the inhibitory properties of coumarin-3-carboxylate derivatives against these enzymes. Our small collection of these versatile organic compounds was enriched by newly synthesized derivatives in order to obtain molecules selective against one, two, three enzymes or acting on the four ones. We evidenced a series of compounds with IC50 values in the nanomolar range. A suicide mechanism was observed against kallikrein 7 whereas the inactivation was either definitive (suicide type) or transient for kallikreins 5 and 14, and matriptase. Most of these potent inhibitors were devoid of cytotoxicity toward healthy human keratinocytes. In situ zymography investigations on skin sections from human kallikrein 5 transgenic mouse revealed significant reduction of the global proteolytic activity by several compounds.

Investigation of the inhibition mechanism of coumarins on chymotrypsin by mass spectrometry

6-Chloromethylcoumarin derivatives are known to express a marked inhibitory potency against serine proteases. However, their mechanism of inhibition remains unclear. In order to confirm the postulated mechanism, we use mass spectrometry. The shift mass obtained after inactivation by two compounds, which differ only by the nature of the leaving group (chloride or acetate) was in agreement with an alkylenzyme formation. With another compound devoid of a latent alkylating group, the shift mass obtained with the complex corresponds to an acylenzyme resulting from the interaction of the serine residue with the lactone carbonyl group. These results clearly demonstrate that the inhibition is not due to an attack of the exocyclic carbonyl group by the active serine but rather result from a nucleophilic attack on the intracyclic carbonyl group.