Shares of AMC were up 3.5% in late trading, near 63.50, in the stock market Thursday.AMC Networks owns and operates several cable TV channels, including AMC, IFC, and Sundance Channel, producing shows such as The Walking Dead and Mad Men.Among his reasons for the upgrade, Miller referred to a number of key catalysts upcoming in the next 2-3 quarters, including season four of The Walking Dea