NEW YORK (AP) -- Stock futures tumbled Wednesday after economic policymakers signaled that they may be less willing to fund more economic growth through bond purchases. The Dow Jones industrial average futures fell 112 points to 13,020. The Standard & Poor's 500 index futures fell 12.1 points to 1,396.7. The Nasdaq composite futures slipped 21.25 points to 2,757.75. The Institute for Supply Management will release its services index at 10 a.m. Eastern time and economists expect it to show that growth has cooled compared to February, which came in at the highest growth in a year. But it was the...