The present invention relates to a method of inhibiting carcinoma progression wherein matriptase plays a role in a subject in need of such inhibition including administering to a subject an effective amount of a compound comprising two positively charged groups, which are the same or different. The groups are linked by a chemical group having a length of between 5 and 30 A, and preferably between 15 and 24 A. Diagnostic methods based on matriptase action and therapeutic methods involving inhibition of matriptase activity are provided. Exemplary compounds are pentamidine and analogs thereof.