Here is what WIKIPEDIA says:

"Motion picture film, primarily because of the rem-jet backing, requires different processing than standard C-41 process color film. The process necessary is Eastman Color Negative 2 (ECN-2), which has an initial step using an alkaline bath to remove the backing layer. There are also minor differences in the remainder of the process. If motion picture negative is run through a standard C-41 color film developer bath, the rem-jet backing will partially dissolve and destroy the integrity of the developer and, potentially, ruin the film."