American Express Co. (NYSE: AXP US) and other credit-card issuers tumbled as JPMorgan Chase & Co. attributed weakness in its card business to rising costs on marketing and promotions, sparking concern over heightened competition. Shares of AmEx dropped as much as 4.5%, the most in more than a year before closing 3,54% lower at $168,72. AXP shares remain in a strong uptrend.